The Helkimo Clinical Dysfunction Index (HCDI) is a simple and quick test used to evaluate subjects affected by temporomandibular disorders (TMDs), and its psychometric properties have not been tested. The test evaluates movement, joint function, pain and musculature, providing a quick general overview that could be very useful at different levels of care. For this reason, the aim of this study was to validate the use of the HCDI in a sample of patients with TMD. Methods: The sample consisted of 107 subjects, 60 TMD patients and 47 healthy controls. The study evaluated concurrent validity, inter-rater concordance and predictive values. Results: The HCDI showed moderate to substantial inter-rater concordance among the items and excellent concordance for the total scores. The correlation with other TMD assessment tests was high, the correlation with dizziness was moderate and the correlation with neck pain, headache and overall quality of life was poor. The prediction of TMD showed a sensitivity of 86.67%, a specificity of 68.09% and an area under the curve (AUC) of 0.841. Conclusions: The HCDI is a valid and reliable assessment instrument; its clinimetric properties are adequate, and it has a good ability to discriminate between TMD-affected and TMD-unaffected subjects. Temporomandibular joint disorders (TMDs) are a very prevalent condition that, according to some authors, are present in 27.4% of adolescents  and 25% Due to the wide list of related symptoms, diagnostic criteria for temporomandibular disorders (DC/TMDs) were designed for the performance of an exhaustive assessment of each patient ; for thiAccording to the cost of misdiagnosis and the time necessary to perform the reference test for TMD diagnosis, it would be beneficial to find a simpler and quicker tool to use as a diagnostic method for TMD in primary care. The Helkimo Clinical Dysfunction Index (HCDI) has been widely used for the clinical diagnosis of TMDs ,18,19. ITherefore, a thorough analysis of the main properties of the HCDI is necessary, using the DC/TMD protocol as a reference. For this reason, the aim of the study was to assess and test the psychometric properties of the HCDI in patients with TMD.To meet the objectives of this work, a cross-sectional validation study was designed. The protocol of this study received the approval of the Research Ethics Committee of Jaén, Spain . This study was conducted in accordance with the Declaration of Helsinki, good clinical practice guidelines and all applicable laws and regulations, and written informed consent was obtained from all subjects to participate in the study.The sample size calculation was carried out using the recruitment of at least 10 subjects per item of the scale as a criterion, with a minimum of 80 subjects for validity studies and 20 for reliability . This stOnce the patients were selected, demographic data were recorded: age, sex, height, weight, body mass index (BMI), educational level, work situation, smoking status, alcoholic habits and physical activity .The diagnostic validity of the HCDI was measured according to the DC/TMD protocol, which is the gold-standard diagnostic test for TMD. The DC/TMD protocol is composed of 12 items that assess muscle and joint pain, pain during jaw movement, headache, bites, noise, obstacles or blockages during jaw movement and discomfort in the palpation of the muscles of the temporomandibular joint. Finally, a diagnostic tree is used to specify a diagnostic result. The DC/TMD protocol has a sensitivity of 86%, a specificity of 98% and an inter-examination reliability of 85% .The main measure was the HCDI. The instrument is comprised of five items, with each assessment having three possible answers, scored as 0, 1 or 5. The first item (A) is related to the limitation in the range of jaw movement and is subdivided into four sections: the maximum opening of the mouth and the protrusion and lateral shift to both sides. In the opening of the mouth, a value of more than 40 mm scores 0 points, a value between 30 and 39 mm scores 1 point and opening less than 30 mm scores 5 points; protrusion and lateral mouth shifts score 0 if the measurement is 7 mm or more, 1 point if the range of motion is between 4 and 6 mm and 5 points if the range is less than 4 mm. These subsections of item A are added together to obtain a subtotal that scores 0 if the sum of the four sections is 0, 1 point if the subtotal is between 1 and 4 points and 5 points if the subtotal is greater than 4 points. The second item (B) evaluates the alterations of joint function that produce deviations, sounds and/or joint locks or blockages; the third item (C) evaluates the presence of pain when performing some movements; the fourth item (D) evaluates muscular pain in the masticatory muscles; and the fifth item (E) evaluates the presence of discomfort or pain in the prearticular area of the temporomandibular joint (TMJ) through palpation. From the sum of the 5 items, we identify no TMJ involvement if the score is 0, mild TMJ involvement when the score ranges from 1 to 9, moderate TMJ involvement if the score ranges between 10 and 19 and severe TMJ involvement for a score between 20 and 25. Previous studies have shown that the HCDI is able to detect TMD-affected subjects with rheumatoid arthritis, with a statistically significant difference between affected and unaffected subjects ,27,28.Concurrent validity was also measured with Fonseca’s anamnestic index (FAI), which is made up of 10 questions that can be answered with yes, no or sometimes, and these answers are scored 10, 0 or 5, respectively. This questionnaire classifies patients according to the affectation, with a total score between 0 and 100. The test categorises temporomandibular disorder as not affected when the score is between 0 and 15 points, mild affectation when the score is between 20 and 40 points, moderate affectation when the score is between 45 and 65 points and severe affectation when the score is between 70 and 100 points. The FAI has a Cronbach alpha of 0.826, an intraclass correlation coefficient of 0.937, a cut-off point of >35 points, a sensitivity of 83.33% and a specificity of 77.97% ,30. SimiPain perception was evaluated by the Numerical Pain-Rating Scale (NPRS) test. The subjects indicate their perceived pain with a number between 0 (no pain) and 10 (the worst pain possible). This tool was used to quantify both the neck and the temporomandibular joint and is the pain assessment test preferred by Spanish-speaking patients. The test has a strong correlation with the Visual Analogue Scale (VAS) and the Four-category Verbal Rating Scale (VRS-4) instruments, with the NPRS being preferred by patients; the Kaiser–Meyer–Olkin (KMO) value is 0.85, with a Bartlett sphericity of <0.01, a landing factor of 0.95 and a lack of implementation percentage of <0.01% .To evaluate the possibility of associated neck disability, the Neck Disability Index test was used; it is a 10-question survey, with answers being reported as a number between 0 and 5. For each question, a score of 0 refers to the total absence of disability, while a score of 5 refers to total disability. In this line, a total score between 0 and 5 indicates absence of disability, 5–14 points indicate low disability, 15–24 point indicates moderate disability and 35–50 points indicate great disability. Cronbach’s alpha is 0.89, and the intraclass coefficient is 0.98, with a Pearson’s correlation coefficient with the visual analogue pain scale of r = 0.65 and with the Northwick Park neck pain questionnaire of r = 0.89 .p < 0.01); factorial analysis shows a structure formed by three components, and there is perfect correlation with the Dizziness Characteristics and Impact on Quality of Life (UCLA-DQ) (>0.75) [The presence of vertigo and balance problems was assessed by the Dizziness Handicap Inventory (DHI). This questionnaire is composed of 25 questions that can be answered with yes, no or sometimes, scoring 4, 0 and 2 points, respectively. This questionnaire assesses physical, emotional and functional dimensions, each of which has an independent score in addition to the total score. There is a high correlation between each of the dimensions and the total score ( (>0.75) ,35,36.Headache-associated symptoms were measured with the Headache Impact Test (HIT-6), which is an evaluation questionnaire consisting of six questions that can be answered with usual, almost always, sometimes, rarely and never, with a total score between 36 and 78 points. The correlation between the HIT-6 in different languages is high, it has high reliability, and its items are comparable .Finally, the quality of life was assessed using the 12-item Short-Form Health Survey (SF-12). This questionnaire is the short version of the SF-36 and retains its self-administered form. It results in a Mental Component Summary score and a Physical Component Summary score (PCS-12), differentiating between the two components of the quality of life. The weights of the Spanish version of the SF-12 are similar to those of the original American version, with a correlation of >0.9. The questionnaire explains 91% of the variance of the SF-36 in the sum of the components, and the coefficient of internal consistency is 0.9 for the SF-36 and slightly lower for the SF-12 .p < 0.05).Descriptive analysis was performed by calculating means and standard deviations for continuous variables and frequencies and percentages for categorical variables. The Kolmogorov–Smirnov test was used to verify the normality distribution of the continuous variables, and the Levene test was used to test the homoscedasticity of the samples. The confidence level was set at 95%  of Shrout and Fleiss was used in a one-way random effects model of the absolute agreement type; it estimates the reliability of single ratings . ReliabiTo analyse the concurrent validity of the HCDI with the FAI, NPRS, NDI, DHI, HIT-6 and SF-12, Pearson’s correlation coefficient r was used. The correlation coefficient was considered strong if it was >0.50 and moderate if it was between 0.30 and 0.50 .The ability of the HCDI to discriminate between TMD patients and healthy subjects was determined using receiver operating characteristic (ROC) curves. First, the classification of the subjects as TMD patients or healthy controls was carried out based on the diagnostic criteria of the DC/TMD protocol, and the total score obtained in the HCDI was evaluated as a variable. In the ROC curve, the fraction of true positives (sensitivity) was represented as a function of the fraction of false positives for different cut-off points. The area under the curve (AUC) was also calculated as a measure of the ability of the score to discriminate between the two diagnostic groups . The AUC was considered statistically significant when the 95% confidence interval did not include 0.5 . Values In all, 158 people were contacted, but the final sample was composed of 107 participants , as 51 did not meet the selection criteria or refused to participate. The sociodemographic and anthropometric characteristics of the sample are shown in Results showed a maximum weighted kappa value of 0.774 for item C and a minimum value of 0.426 for item A2. Based on these values, reliability ranged from moderate to substantial, while the total score of the scale reached an excellent degree of concordance of 0.905 . Figure ROC curve analysis found an optimal cut-off point of more than 1 point in the HCDI score that showed a sensitivity of 86.67% with a specificity of 68.09% for the diagnosis of TMDs, making the DC/TMD protocol the gold standard . This anThis study evaluated the clinimetric properties of the Helkimo Clinical Dysfunction Index. The data obtained suggested that it is a valid and reliable instrument for evaluating patients with TMD, determining the degree of severity of the condition and discriminating between affected and unaffected patients with TMD. In this study, a total sample of 107 patients was used , and all of them were evaluated by this test, which lasted approximately 4 min. The two groups were comparable, except that a higher proportion of females who suffered from TMD, which is a consistent observation among TMD studies ,27. ThisDespite being a commonly used tool for TMD assessment , few autOliveira de Santis et al. conducted the only study analysing the psychometric characteristics of the HCDI and the American Association of Orofacial Pain (AAOP) index in subjects aged between 6 and 18 years, using the DC/TMD protocol as a reference. The authors found a non-statistically significant difference between genders, a sensitivity of 53.40% and a specificity of 77.27% for the HCDI, as well as a low level of accordance between the test being considered and the gold standard . NonetheThe present study had some limitations. First, the study sample had a higher proportion of women due to the higher proportion of women affected by TMD. Furthermore, although this study analysed the most common psychometric properties, we did not study the sensitivity to change or the ability to discriminate between different TMD populations. Additionally, this study was carried out on a sample of resident patients in a well-defined geographic location, which limits the generalisation of the results obtained.The study shows that the HCDI is suitable for the diagnosis of TMD. The inter-observer concordance was between moderate and substantial for each of the items and excellent for the total score of the test. The HCDI has strong concurrent validity with the FAI, SFAI and NPRS orofacial assessment instruments; moderate validity with the NPRS neck pain assessment, emotional and physical facets and the total DHI value; and poor validity with respect to HIT-6 instruments, the mental and physical components of the SF-12 and the functional component of the DHI. The HCDI shows a sensitivity of 86.67%, a specificity of 68.09% and an AUC of 0.841 to predict the presence of TMD.


Islet amyloid polypeptide (IAPP) is a proposed cause of the decreased beta-cell mass in patients with type-II diabetes. The molecular composition of the cell-membrane is important for regulating IAPP cytotoxicity and aggregation. Cholesterol is present at high concentrations in the pancreatic beta-cells, and in-vitro experiments have indicated that it affects the amyloid formation of IAPP either by direct interactions or by changing the properties of the membrane. In this study we apply atomistic, unbiased molecular dynamics simulations at a microsecond timescale to investigate the effect of cholesterol on membrane bound IAPP. Simulations were performed with various combinations of cholesterol, phosphatidylcholine (PC) and phosphatidylserine (PS) lipids. In all simulations, the helical structure of monomer IAPP was stabilized by the membrane. We found that cholesterol decreased the insertion depth of IAPP compared to pure phospholipid membranes, while PS lipids counteract the effect of cholesterol. The aggregation propensity has previously been proposed to correlate with the insertion depth of IAPP, which we found to decrease with the increased ordering of the lipids induced by cholesterol. Cholesterol is depleted in the vicinity of IAPP, and thus our results suggest that the effect of cholesterol is indirect. Islet amyloid polypeptide  is co-secreted with insulin  from theIslet amyloid polypeptide is a 37 residue peptide with a net positive charge of +3  at physiological pH, as illustrated in Few structures of the mature fibrils are available; 2+-ATPase (SERCA)  , the dop (SERCA) , aquapor (SERCA) , and pep (SERCA) . CHOL ch (SERCA) . Some ex (SERCA) .sn-glycero-3-phosphatidylcholine (DOPC or PC), 10% 1,2-dioleoyl-sn-glycero-3-phosphatidylserine (DOPS or PS), and CHOL concentrations of 20 and 40%. They also showed that high concentrations of anionic DOPS lipids (above 25%) diminish the effect of CHOL , and with an isothermal compressibility of 310−4bar−1 for the system. In the production run the pressure was controlled with the Parrinello-Rahman barostat  between the two simulation series in question is shown in ormation , as seenormation . Interesormation , this inormation .There are general differences between the position of the kinked and the straight peptides. Comparing Membrainy tool . For the systems with DOPC and DOPS lipid there is a significant depletion of DOPC and a significant enrichment DOPS within the at all the measured distances , the effect is, however, decreasing with the distance. The distances 7, 14, and 21 Å, were used in the original paper by 1–19, as illustrated in The lipid depletion-enrichment index (D-E index) is calculated to investigate local concentration variations of the lipids surrounding the peptide . The anaSince the effect of the lipids on the position of IAPP can not be explained completely by the physical properties of the membrane, a structural clustering is performed to investigate the specific interactions between the lipids and IAPP. In order to perform a structural clustering of IAPP and the membrane lipids, the conformational flexibility of IAPP has to be taken into account. The largest flexibility is in (a) the N-terminal loop (residue Lys1 to Cys7), (b) in the C-terminus after the C-terminal helix from residue Ser28 to Tyr37, and (c) in the kink region of the peptides between the N-terminal and C-terminal helix; the kink usually includes residue His18 to Phe23, and allows for variation in the angle between the two helices.A geometric clustering was performed to better understand the flexibility in the N-terminal loop . The analysis is repeated for IAPP with the N-terminal loop in each of the two orientations. The occupancy maps can be seen from other angles in The 3D occupancy maps in O1 in two regions around the peptide; at the N-terminal of the peptide, where DOPC interacts with the loop region (Lys1 – Cys7). Seen from above  of DOPC and DOPS are illustrated with representative structure in Binding mode 1 (BM1) This is the most prominent lipid binding mode placed on the right side of the helix, with the lipid binding in a pocket between Arg11 and Asn14 and the tails between Leu12 and Phe15. This binding mode is independent of the orientation of the N-terminal loop and the binding mode is observed for both DOPC and DOPS lipids. Binding mode 2 (BM2) is another prominent “binding mode.” It entails the unspecific salt-bridge interactions with Lys1, both DOPC and DOPS has a negative charge at the phospholipid phosphate which can interact with Lys1, the N-terminus, or bridging between the two. In the case of DOPS, the two negative charges can interact with Lys1 and the N-terminus simultaneously, thus making this interaction very favorable for DOPS lipids, as seen from the relatively high occurrence of this binding mode for DOPS lipids compared to DOPC lipids. Independent of the orientation of the N-terminal loop, it is a common interaction point for the phospholipids. In Binding mode 3 (BM3) the N-terminal loop between Cys2 and Cys7 consists of several hydrophilic residues , and it has exposed backbone atoms, making it a good interaction point for the hydrophilic headgroups of both DOPC and DOPS. In O2 of Binding mode 4 (BM4) the N-terminus and Lys1 is pointing toward the right side of the helix. In this orientation the phospholipid can interact with Lys1 (or the N-terminus) and Arg11 simultaneously. Binding mode 5 (BM5) only occurs for the loop in O1, where the phospholipids can bind between Gln10 and Lys1 (or the N-terminus).In addition to the binding modes presented here, less frequently occurring binding encounters are found, e.g., some binding modes interacting with the kinked region, more details about these binding modes are available in It would be expected that the membrane composition affects the distribution and frequency of the lipid binding modes. The lipids could potentially be competing for the binding site, and the change in positioning of the helix in the presence of CHOL could affect the frequency of experiencing a given binding modes. The binding frequency of the binding modes could also be dependent on whether IAPP is straight or kinked. The fraction of each simulations series contributing to the binding modes of phospholipids and CHOL is shown in Moving on to cholesterol, the 3D Occupancy maps show the interactions between the N-terminal helix and CHOL is less dependent on the orientation of the N-terminal loop. The interactions between CHOL and the N-terminal helix are primarily defined by hydrophobic interactions and hydrogen bonding of the hydroxyl group. The binding modes of CHOL are depicted in Binding mode 1 (BM1) of CHOL to the N-terminus of IAPP is at the kink region, this region has several hydrophilic residues (His18 and Ser19) and exposed backbone in the kinked peptides. At the kink region the hydrophobic residues Phe15, Leu16 and Val17 can interact with the hydrophobic rings of CHOL. Even for the straight peptides the kink region is an important interaction point (Binding mode 2 (BM2) is at the left side of the helix, near the N-terminal. In BM2, CHOL hydrogen bond to Thr9 or Gln10, and interact with the hydrophobic residues Leu12 and Ala13. In binding mode 3 (BM3) CHOL interacts with the N-terminal helix end, most frequently interacting with Ala8, Thr9, and Leu12, and the exposed backbone atoms. Binding mode 4 (BM4) is very unspecific, in this binding position CHOL interacts with the hydrophobic residues below the helix, most frequently Leu12 and Phe15. In Binding mode 5 (BM5), CHOL interacts with the right side of the helix between the loop and Arg11, with hydrogen bonding to Arg11 and hydrophobic interactions with Ala8.on point , due to The relative occurrence of the CHOL binding modes can also be affected by the orientation of the N-terminal loop, the conformation of IAPP (straight or kinked), and the membrane composition. The relative contribution of each simulations series to the binding modes is shown in Binding mode 1 involves binding in the kink region, it is therefore expected to be affected by whether IAPP is in a straight or a kinked conformation. In the PC/CHOL membranes, BM1 is observed more frequently for the CHOL binding to IAPP in the kinked conformation than in the straight conformation, independent of the orientation of the N-terminal loop. In the PC/PS/CHOL membrane, this trend is not observed, and their relative binding frequency is independent of the conformation of IAPP, as seen in 1–19, which was also observed from the 3D occupancy maps in Other than the variations in the binding frequency in BM1 there are no major variations across the systems. The binding modes are very evenly distributed around IAPPCholesterol is an important element of the lipid membrane, and it is often present as a sizeable fraction of the membrane lipids. CHOL affect the aggregation propensity and membrane effects of IAPP, however, the specific role of CHOL is unclear. This study investigates the effect of CHOL on the membrane bound state of IAPP.The results presented here, confirm the stabilizing effect of lipid bilayers toward the helical structures of IAPP. Both the straight and the kinked conformations of IAPP were found to be stable on the membrane but unfolded in solution. The C-terminus was found to be less structured than the core membrane binding region in the N-terminal half of the peptide, which is in good agreement with previous results . No signIt was found that the depth of membrane insertion of the amphipathic helices was affected by CHOL and whether IAPP was in a straight or a kinked conformation. CHOL generally results in a less deep insertion of the IAPP, than in pure phospholipid membranes, which can be explained by the increased ordering of lipids. A deep binding indicates a strong binding, and IAPP is observed to bind weaker to ordered membranes in experiments . The pre1–19 was enriched with DOPS lipids and slightly depleted of CHOL, as seen from the D-E indices in 1–19 and the phospholipids is very dependent on the positively charged groups . CHOL has a less well-defined interaction pattern, and it mostly interacts underneath the helix and with the kink region, as can be observed from the most frequent CHOL binding modes and 3D occupancy maps. It has been proposed from experiments that CHOL interacts directly with Phe15, which increases the binding affinity of IAPP to the membrane (It was found that the membrane patch around IAPPmembrane . It was Based on these results we propose, that the effect of CHOL on the membrane bound state of IAPP and the membrane induced amyloid formation, is based on changes in insertion of IAPP due to changes in the physical properties of the membrane, rather than through direct interactions. We managed to observe significant changes in the insertion depth of IAPP in the presence of CHOL, and we found that PS can diminish the effect of CHOL. This provides a structural interpretation of the effect of CHOL on the membrane binding and the effect of the lipids on the aggregation rate.This study is a step toward a deeper understanding of the role of CHOL in IAPP aggregation. Further studies, which take lipid raft formation into account need to be performed, but this topic is reserved for future work.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.MC did the simulations and analysis. BS designed the project and supervised the work. All authors wrote the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


In order to determine the influence of water with micro-nano bubbles of gases, the consistency of fresh mortar and the physical properties of hardened mortar, i.e., specific and apparent density, total porosity, water absorption by weight and capillary absorption, were established. The mechanical strength of the considered mortars was studied as well by conducting the tests for flexural and compressive strengths following 14, 28 and 56 days. Reduced workability and capillary absorption were observed in the modified mortars within the range of 0.9–8.5%. The mortars indicated an increase in the flexural strength after 28 days ranging from 3.4% to 23.5% and improved compressive strength in 1.2–31%, in comparison to the reference mortar. The conducted studies indicated increased flexural and compressive strengths along with the share of micro-nano bubbles of gases in the mixing water.The paper presents the experimental studies on the effect of the water containing micro-nano bubbles of various gases on the physico-mechanical properties of lime-cement mortars. In total, 7 types of mortars were prepared: with water containing the micro-nano bubbles of O Nanotechnology is a branch of science and technology concerned with production, study and application of nanomaterials, i.e., particles with the size under 100 nm in at least a single dimension . This is2 increases the pozzolanic reactivity of a concrete mixture, improves the compressive strength, as well as decreases porosity and water absorptivity ,3].Total porosity, determining the share of pore volume in the total volume of material, was calculated in line with , using tWater absorption by weight, which constitutes the capacity for water absorption of the material at atmospheric pressure, was determined in accordance with PN-EN 13755:2008  as the rC—water absorption coefficient [kg/m2],wm24—sample weight determined after 24 h of capillary water rise [g],sm—sample weight after drying to constant mass [g].Capillary rise was studied in line with the PN-EN 1015-18:2003 standard . Six samThe studies aimed at determining the mechanical properties of the analyzed lime-cement mortars involved in the flexural and compressive strength tests. The tests were performed in accordance to the PN-EN 1015-11:2001 standard  using ba2, O2 and O3. The applied MDS method [The multidimensional scaling (MDS) method was used for visualization of the similarity level for the component of matrix containing the data connected with the properties of the examined mortars along with the different amount  of used MNW with COS method ,56,57 alS method . Its aimS method . General2 micro-nano bubble water. This is connected with the accelerated binder hardening processes. Hydrated lime, forming an air-hardened binder after being mixed with water, hardens as a result of a slow carbonatation process, reacting with the carbon dioxide from the atmosphere and forming calcium carbonate. Application of the CO2 micro-nano bubble water, instead of ordinary mixing water, accelerated the hardening process.The consistency tests of lime-cement mortars prove the effect of micro-nano bubble water on the workability of prepared mixes. The use of micro-nano bubble water instead of the mixing water resulted in a reduction of mortar fluidity and workability. The greatest drop in mix fluidity was observed in the mortars with the COMNB water also affects the cement mixes. Khoshroo et al.  investigArefi et al.  investig3). These mortars also had the highest apparent density and lowest water absorption by weight, 2.7–2.8% lower in comparison to the reference mortars. In turn, substituting mixing water with the ozone and oxygen micro-nano bubble water in 50% and 100%, increased the water absorption by weight. Substituting 50% of mixing water with the oxygen micro-nano bubble water did not indicate a significant difference in water absorption by weight. The 50% O2 mortar was characterized by the lowest total porosity. The 100% CO2 mortars indicated the highest total porosity; however, this result is comparable to the porosity of the reference sample.Oxygen and ozone micro-nano bubble water reduced the specific density of the investigated mortars. The mortars with the carbon-dioxide micro-nano bubble water were characterized by the highest specific density amounting to 2.39–2.44  was observed, which was 1.6-fold lower than the mortars with 6% SiO2 and halved in comparison to the mortars with 9% nanoaddition. The authors attributed the reduction of capillary absorptivity of the mortars with nanoadditions to the decreased pore dimensions and increased number of gel pores.A decrease in capillary absorption can be attributed to the reduced pore diameter of the lime-cement mortar resulting from the admixture of different nanomaterials. This can be confirmed by the studies conducted by Kyriakou et al. . The aut2 addition. The authors attributed this phenomenon to the occurrence of pozzolanic reaction between Ca(OH)2 and nano SiO2. An improvement in the carbonatation process and a reduction in pore diameter were also observed.Luo et al.  observed2 addition. An increase in open porosity was observed as well. In the hardened mortars, the presence of microcracks filled with precipitated CaCO3 was observed, which reduced the diameter of capillary pores, and contributed to the reduction in capillary absorption in relation to other mortars.The studies by Ergenç et al.  on lime-2 micro-nano bubbles, compared with the carbon dioxide from the atmosphere and the related phenomenon of pores filling with calcium carbonate. A reduction in capillary absorption after 30 min and reduced depth of water infiltration into the concrete following substitution of tap water with the micro-nano bubble water was confirmed by Yahyaei et al. [Kim et al.  observedi et al. . MoreoveIn turn, the studies by Khoshroo et al.  indicateSimilar conclusions were drawn by Mohsen Zadeh et al. . SubstitThe research conducted by Asadollahfardi et al.  showed t2 mortars. In relation to the reference mortar, this is a 31% increase. In the remaining mortars, the compressive strength increased by 1.2–27.4% compared to the mortar with ordinary water. The examined mortars indicate improved flexural and compressive strengths along with the increasing mixing water substitution. The only exception are the mortars with O2, in which the flexural strength dropped by 2.6%, whereas the compressive strength reduced by 18.2%, following the complete substitution of mixing water with micro-nano bubble water—in relation to the 50% substitution. In turn, the highest strength after 56 days was achieved by the mortars with CO2, reaching 2.97 and 3.32 (MPa) for the 50% CO2 and 100% CO2, respectively. Almost all mortars indicated increased flexural strength after 56 days in the range of 8.3–34% and improved compressive strength by 4–19.4%, compared to the reference mortar. Only the 50% O2 mortar, which was characterized by the highest compressive strength after 28 days, showed an 8.3% reduction, in relation to the reference mortar.On the basis of the conducted studies, it was stated that substituting mixing water with micro-nano gas bubble water improves the strength of lime-cement mortars. The compressive strength clearly increases along with the quantity of MNB. Nanomaterials, due to their large specific surface, are characterized by increased chemical reactivity, which is suggested by the afore-mentioned literature sources ,13,14,152 and nano TiO2, indicated an improvement of the mechanical properties of all mortars containing nanoadditives. Moreover, the authors observed an increase in the durability of the mortars containing a hydraulic binder with nano SiO2 as well as increased resistance to salt crystallization of the mortars with nano TiO2.Literature contains multiple works confirming the influence of nanoadditives on the improvement of the mechanical properties of cement mortars ,27,28,292 addition (w/w) after 28 and 90 days by 14.9% and 20%, respectively, in comparison with the reference samples. Moreover, it was observed that the nanomodified mortars exhibited greater hydraulic properties with more hydrated phases and more progressive carbonatation degree. Nanoparticles participate in the binding of lime, precipitating the C-S-H gel, reducing the diameter of pores, and increasing the share of gel pores [Kyriakou et al.  observedel pores .Similar conclusions were drawn by Mohsen Zadeh et al. . The mic2 micro-nano bubble water. It was observed that the CO2 micro-nano bubble water had higher strength properties in the initial period and yielded comparable results after 28 days, in relation to the reference mortars. The increased strength in the initial period was attributed to the greater amount of CaCO3 in the cement matrix, which made the structure of mortars denser.Kim et al.  comparedKhoshroo et al.  stated tArefi et al.  observedIn turn, Maruyama et al.  reported2, O3 or CO2 micro-nano bubble water as well as the reference mortar  for the matrix containing the results of all measurements connected with the properties of the lime-cement mortars along with the 50% and 100% mixing water substitution with Ortar see .2 MNB water is found in close proximity of the afore-mentioned triangle, reflecting the properties and their general variability in the case of the reference mortar. It can be seen that the 50% share of the MNB water contributes to a shorter distance between the visualized points than in the case of the points obtained with 100% share of MNB water. The polygon visualizing the properties of the mortars with CO2 MNB also has greater surface and distances between the extreme edges than other polygons, which indicates greater variability of the obtained results and more significant effect of increasing dose on the obtained results of measurements. Another dependence visualized graphically through multidimensional scaling is that the results obtained from the measurements of the mortars with O2 addition are more similar (less distant) to the reference mortar compared to the mortars with the O3 MNB water. Moreover, relatively short distances between the edges of the polygon reflecting the sum of mortar properties suggests lesser influence  on the analyzed parameters of the O2 MNB water dose than in the case of the CO2 or O3 MNB water. In the two-dimensional space, the polygon reflecting the results of measurements related to the mortar with O3 was most distant from the triangle visualizing the results of the reference mortar.Another piece of information from the MDS analysis is the low value of STRESS parameter, reaching 0.09, which indicates a good fit of the matrix of the estimated distances to the observed distances. It is additionally supported by a tight point cloud along the plane described by the target rank on the x-axis and the obtained rank on the y-axis see .2, O3, CO2) used as 50% and 100% mixing water substitute and a reference mortar with ordinary tap water were tested. The studies indicated that the micro-nano gas bubble water reduces the workability of lime-cement mortars in all analyzed cases. Since nanomaterials are chemically active, the MNB water affected the cement properties, accelerated the hydration reaction and the early curing process. This phenomenon was observed especially during the compressive and flexural strength tests.2 mortars, which translates into a 31% improvement in relation to the reference sample. The 50% O3 mortar, in which strength dropped by 2.6%, constitutes an exception. Almost all mortars indicated an increase in flexural strength after 56 days, ranging from 8.3% to 34% and increased compressive strength in the range of 4–19.4%, compared to the reference mortar.Along with an increase in the amount of MNB, the compressive strength is markedly proved. The highest strength after 28 days was achieved by the 50% O2 increased the specific density, which resulted from faster CaCO3 formation in the mortar. The CO2 micro-nano bubble water increased the bulk density of the considered mortars by 0.9% and 1.5% in the case of the 50% CO2 and 100% CO2, respectively. These mortars were also characterized by a comparable porosity to that of the reference mortars, reaching the highest porosity values out of all mortars.The studies of the physical properties indicated a diversified influence of micro-nano bubbles on the density of mortars. The oxygen and ozone micro-nano bubble water reduced the specific density of the investigated mortars, whereas the water with COA general reduction in capillary absorption of the mortars with micro-nano bubble water was observed in the range of 0.9–8.5% in relation to the reference mortar. This is caused by a reduced size of capillary pores resulting from the application of MNB water, which is confirmed by the studies concerning the water absorption by weight of the mortars with ozone and oxygen micro-nano bubbles, which reduced the water absorption of the investigated mortars by 2.7–2.8% in relation to the reference mortars.2 micro-nano bubbles as mixing water.The analysis based on the MDS method showed that taking into account the results of all analyzed parameters simultaneously, it is possible to clearly distinguish the mortars prepared with the addition of the water containing micro-nano bubbles of various gases as well as reference mortars. The changes in the properties of the mortar are most clearly visible with the increased proportion of water with the COThe study investigated the effect of water with micro-nano gas bubbles on the physical and mechanical properties of lime-cement mortars. The mortars with three types of gas (OThe ozone, oxygen, and carbon dioxide micro-nano bubble water proved to be a desirable substitute of tap water, ensuring a simultaneous improvement of the physico-mechanical properties of lime-cement mortars. The application of MNB is technologically possible in almost each case and does not require complicated procedures, compared to other nanoadditives used in the construction industry. The works on the prospective application of the water with micro-nano bubbles of various gases in the process of improving the strength of cement composites, as well as the investigations connected with the chemical analysis and determination of the mechanisms occurring in the internal structure of the studied lime-cement mortars are currently underway.


The aim of this study was to synthesize and characterize a novel methacrylate-functionalized calcium phosphate (MCP) to be used as a bioactive compound for innovative dental composites. The characterization was accomplished by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The incorporation of MCP as a bioactive filler in esthetic dental composite formulations and the ability of MCP containing dental composites to promote the precipitation of hydroxyapatite (HAp) on the surfaces of those dental composites was explored. The translucency parameter, depth of cure, degree of conversion, ion release profile, and other physical properties of the composites were studied with respect to the amount of MCP added to the composites. Composite with 3 wt.% MCP showed the highest flexural strength and translucency compared to the control composite and composites with 6 wt.% and 20 wt.% MCP. The progress of the surface precipitation of hydroxyapatite on the MCP containing dental composites was studied by systematically increasing the MCP content in the composite and the time of specimen storage in Dulbecco’s phosphate-buffered solution with calcium and magnesium. The results suggested that good bioactivity properties are exhibited by MCP containing composites. A direct correlation between the percentage of MCP in a composite formulation, the amount of time the specimen was stored in PBS, and the deposition of hydroxyapatite on the composite’s surface was observed. Natural bone and teeth are unique composites of biological origin. They consist of a mineral inorganic phase of calcium-phosphates and an organic phase of collagen. Dentin is a mineralized structure that forms the major component of dental hard tissue. It is covered by a highly mineralized and protective layer of enamel in the crown and cementum in the root ,2.Demineralization and remineralization processes co-exist in teeth during the entire life of an individual . Dental Remineralization of carious dentin can occur either by a spontaneous incorporation of beneficial ions, such as calcium, phosphate, and fluoride, from the oral fluid into remnant crystallites in the demineralized tissue, or by treatments that incorporate the same beneficial ions from external sources. The repair of dental caries with dental restoratives (fillings) that release calcium, phosphates, and fluoride ions is gaining interest. These bioactive restoratives can help to prevent caries by inducing the remineralization of hypo-mineralized caries lesions and by interfering with the metabolic activity of the biofilm ,8.Dental resins containing calcium phosphate fillers such as hydroxyapatite (HAp), amorphous calcium phosphates, nano-calcium phosphates, and mono-, di- and tetra-calcium phosphates have been investigated in recent years as calcium and phosphate releasing composites with remineralizing capabilities ,10,11,12Recently, a combination of reactive calcium dihydrogen phosphate and tri-calcium phosphate has been used. The less soluble tri-calcium phosphate enhances control over the composite’s water absorption and the dissolution of the more soluble calcium dihydrogen phosphate . A lightSeveral strategies to increase the interaction of these bioactive fillers with resin phases have been tested . These iA great surge of interest in bioactive dental materials was observed in 2013 after the introduction of the first esthetic, bioactive, dental restorative material, Activa Bioactive-Restorative (AB) . AB is composed of a reactive, ionic resin (bis-2-(methacryloyloxy)ethyl phosphate) (Bis-2), polycarboxylic acid, and reactive glass. It releases and recharges beneficial calcium, phosphate, and fluoride ions , which fThe original AB materials require a two-part system to derive the benefit of the glass ionomer reaction. To achieve bioactive properties in a one-part material, the authors synthesized methacrylate-functionalized calcium phosphate (MCP), a calcium phosphate with pendent methacrylate groups. Composites incorporating MCP can be formulated as one-part, light-cure only materials. Although dental composites containing varying amounts of bioactive fillers, such as bioglass or calcium phosphate, have been studied, the application of a methacrylate-functionalized calcium phosphate and its commercial development as an esthetic bioactive composite is hitherto unknown. This study investigates the bioactivity of methacrylate-functionalized calcium phosphate containing composites in a concentration dependent manner and the effect of MCP on the optical and physical properties of the composites. The null hypothesis assumed that incorporation of the highly functional methacrylate calcium phosphate (MCP) would not affect the esthetics, translucency, depth of cure, degree of polymerization, and mechanical properties of dental composites.Methacrylate-functionalized calcium phosphate (MCP) was synthesized by the conventional solution-precipitation chemistry method; reacting calcium salts with a mixture of phosphoric acid and the phosphate-functional monomer, Bis-2. The reagents calcium chloride dihydrate ; calcium hydroxide ; phosphoric acid 80% ; and Bis-2  were used as obtained. The molar ratio of calcium and phosphorous reagents was kept at 1.6. The detailed synthesis of MCP was reported in US Patent . MCP wasAnnealing of the MCP powder was performed in a Paragon E series Kiln equipped with a Sentry 2 Digital Temperature controller  by heating 100 mg of MCP powder in a silica crucible to a temperature of 600 °C for 4 h. The weight of the annealed sample was recorded and the amount of the volatile component was determined by the weight difference. The powder turned brown upon annealing, indicating the thermal degradation of the carbonaceus group. This heat treated MCP powder was not used in any of the experimental polymeric formulations, it was made only to calculate the organic content and Ca/P ratio of the hybrid MCP powder.The bioactive ionic resin formulation used in the tested composites contains aliphatic urethane dimethacrylate  and other multi-methacrylate monomers. The composition is proprietary to Pulpdent Corporation, Watertown, MA, USA. The resin mixture also contains a patented rubberized urethane methacrylate resin  to provi2 , and the intensity was frequently measured with a hand-held radiometer .To determine the optimum levels of MCP required for bioactivity and esthetics, and to understand the relationship between MCP concentrations in the composite and its bioactivity and mineralization properties, formulations with 3 wt.%, 6 wt.%, and 20 wt.% MCP and a control composite with no MCP were investigated for their ion release and physico-chemical properties. All of the specimens were polymerized by light curing with a light source having an output of 600 mW/cm−1 resolution with 32 scans and in the range of 500–4000 cm−1. The FTIR of the surface precipitated layer was measured by scraping off that layer from the specimens after being stored in phosphate buffered saline (PBS) for 21 days at 37 °C.Attenuated total reflection Fourier transform spectroscopy (ATR-FTIR) was employed to characterize the methacrylate-functionalized calcium phosphate (MCP) and the precipitated layer formed on the composite after immersion in PBS. The spectra of the specimens were obtained using a Nicolet IR200 spectrophotometer  with an ATR accessory and were recorded in absorption mode using 4 cmb refers to color parameters over the black background; and subscript w refers to color parameters over the white background.The translucency parameter (TP) was calculated from the color coordinate values of the composite material . The colThe degree of conversion of the composites with respect to the amount of the MCP filler in the formulation was evaluated.Prior to curing, the specimens were fabricated in black silicon molds 1 mm in height and 4 mm in internal diameter placed directly on the ATR cell of the ATR-FTIR spectrophotometer . A transparent Mylar film was placed over the material, and the spectrum of the specimens was recorded before light activation.After light curing the specimen from the top surface for 20 s, the spectrum of the bottom layer of each polymerized specimen was scanned. More scans of the bottom layer were recorded after irradiating the specimen at the top surface for 40, 60, and 120 s.−1 of the polymerized specimen to that of non-polymerized specimen. The DC was calculated according to the following equation [1/A0 and A1′/A0′ are the peak area ratio of methacrylate and amide, before and after polymerization. The amide group of the UDMA at 1537 cm−1 was used as the internal standard [The degree of conversion of the specimens was determined by the ratio of the area of the methacrylate group (C=C) at 1638 cmequation .DC (%) standard .The depth of cure of each test material was measured by ISO 4049 . Specime2. After curing, the specimen bars were taken out of the mold, excess flash was removed, and the specimens were wet polished with 600 grit paper. The specimens were then stored in PBS for one day at 37 °C. The specimen dimensions were measured by a digital micrometer of 0.01 mm sensitivity . Immediately after removing the specimens from the PBS, the three-point flexural strengths of the specimen bars were tested on a universal testing machine  with a cross head speed of 1 mm/min. The distance between the support beams of the three point jig was 20 mm. Flexural strength (FS) in MPa was calculated using the following equation:Max is the load at break, b is the specimen width, h is the specimen thickness, and L = 20.Six specimen bars with dimensions of 2 × 2 × 25 mm were fabricated for each material by injecting the material into a polypropylene mold. The mold was placed between two glass sides covered with Mylar film. The specimen bars were cured for 1 min on each side using a light source of 600 mW/cmThe deflection at break data for each specimen was generated from the three-point flexural strength measurements and was measured by correlating the crosshead motion to beam deflection.Disk shaped specimens (N = 5) approximately 9 mm in diameter and 2.5 mm in thickness were fabricated by injecting the composite material into a silicon mold and light curing for 20 s on each side. The dimensions of each specimen were then accurately measured using the digital micrometer, and the weight of each specimen was recorded. Each specimen was stored in 10 mL of distilled water (pH 7) in an incubator  at 37 °C. After 24 h, each specimen was transferred to a new bottle with 10 mL of fresh distilled water.The calcium ions present in the solution of the original bottle were measured by UV-Vis colorimetric analysis , after an aliquot of the solution was treated with cresolphthalein-complexone reagent  . To caliThe release of phosphate ions was measured by colorimetric analysis using Smart 2 Colorimeter  after complexing with Vanadate Molybdate reagent . The specimens (N = 5) were stored in 10 mL of distilled water, and the soluble phosphate ions in the solution on day one were determined. The procedure was repeated, and the ion release from the specimens was calculated on days 2, 5, 7, 14, 21, and 28. Calibration curves were generated by 1, 2, 5, 10, 20, and 40 ppm standard solutions of sodium phosphate in distilled water.The in vitro bioactivity and the bio-mineralization potentials of MCP containing composites were tested in accordance with ISO method 23317:2014  by immerThe specimens were analyzed using SEM  and energy dispersive X-ray spectroscopy (EDS) to assess the morphology and elemental composition of the surface precipitated layer formed on the specimens. Control specimens (0 days) and the specimens stored in PBS for 7, 14, and 21 days were mounted on aluminum SEM stubs using double-sided, carbon adhesive tape. The SEM stubs were sputter-coated with Au-Pd for 90–95 s in a Denton Vacuum Desk II  to eliminate charging in non-conductive specimens. The specimens were analyzed at 10 KV, condenser spot size −25, objective aperture 200, working distance of 25–28 mm, using a RaySpec light element detector  for 120–130 s to determine the elemental composition of the material. Images were captured at magnifications of 40×, 100×, 1000×, 2000×, 3000×, and 6000×.The synthesis of methacrylate functionalized calcium phosphate was done according to the patented process , and a y−1 region. The absorption peaks of MCP powder at 1720 cm−1(C=O) and 1638 cm−1 (C=C) indicated that the methacryloyl group was already in the powder. The MCP powder and heat treated MCP powder showed multiple peaks in the 550–605 cm−1 region, which were attributed to the bending vibrations of phosphate and hydroxyl groups. The absorption peaks of MCP powder at 1074 cm−1 and 1021 cm−1 were attributed to the P-O vibration modes of regular tetrahedral PO4 groups, which were also observed in the Bis-2 monomer [The FTIR spectrum of the MCP powder was very complex. The absorption peaks of MCP powder were close to, or merged with, the absorption peaks of the phosphate monomer (Bis-2), especially in the 950–1300 cm monomer .−1, 1638 cm−1, and 1454 cm−1 (corresponding to the organic monomer Bis-2). Instead, all of the characteristic peaks of apatitic phosphate groups were observed. The FTIR of the MCP showed characteristic absorption bands of HAp, evidenced by the presence of PO43− , whereas that of annealed MCP showed absorption peaks at 1035 cm−1, 956 cm−1, 944 cm−1, and multiple peaks in the 555–604 cm−1 region, indicative of apatite structure. The newly formed peaks at the 940 cm−1 region may be attributed to the partial thermal degradation of the apatitic structure to a tricalcium phosphate (TCP) structure. This proves the thermal degradation of both the carbonaceous group and the organic functional group upon annealing at 600 °C for 4 h. The organic, volatile part of the MCP was calculated by weight difference to be 42% of the material. The Ca/P ratio of the heat treated MCP was found to be 1.46, which also indicated a possible decomposition of the MCP to TCP on annealing.The FTIR spectrum of the annealed MCP showed no presence of organic groups, as there were no absorption peaks observed at 1720 cmThe translucency parameters (TP) of the experimental composites are presented in −1) of the starting material, represented as 0% of conversion, versus the peak area of the polymerized specimen. The control composite (CS-0) and 3 wt.% MCP composite (CS-3) showed the highest DC values, in the range of 69, and are not statistically different. The DC of the specimens decreased with the amount of added MCP in the specimen. The specimen with 20 wt.% MCP showed the lowest DC at 58%.The mean degree of conversion (DC), measured at the bottom surface of the specimens as a function of irradiation time, and the amount of the functional MCP filler, is shown in The mean ISO depth of cure values are also presented in The mean flexural strength (FS) values of the composites are also presented in Finally, the deflection at break of the specimens is also presented in 2, and the cumulative phosphate ion release from that specimen was 5.2 mM/L or 500 µg/cm2. The control composite released the lowest amount of calcium and phosphate ions; those primarily originated from the inorganic glass fillers.The release of calcium and phosphate ions from the various composite materials was directly correlated to the amount of MCP in the material. The relative molar mass release of calcium ions to phosphate ions decreased as the percentage of MCP filler in the composite decreased.This experiment demonstrated a direct relationship between the hydroxyapatite formation on the surface of the specimens, the percentage of MCP in the specimens, and the number of days of storage in PBS. After 21 days of storage in PBS, all the specimens showed at least partial hydroxyapatite aggregates on this disc surface. As the percentage of MCP increased, there was a dramatic increase in the development of calcium phosphate crystals on the surface of the specimens. The calcium and phosphate contents of the specimens before immersion in PBS were 0.73% and 0.65%, respectively.The SEM micrographs and EDS of specimens containing 3 wt.% MCP (CS-3), before and after immersion in PBS for 21 days, are presented in In-order to understand the biomineralization potential of MCP as a functional filler, experimental specimens containing even higher percentages of MCP were studied. Specimens with 6 wt.% MCP, after 7 days storage in PBS, showed the entire surface of the specimen disc covered with calcium phosphate nucleation sites A. The ED43− ions) was regulated by the bulky organic phosphate group. The linkage of the bulky organic phosphate to the divalent calcium ions occurred through an ionic bonding. In contrast to amorphous calcium phosphate (ACP), MCP exhibited good stability. Compared to crystalline calcium phosphates, amorphous calcium phosphate exhibits greater bioactivity, and has been shown to have better adhesion to periodontal ligament cells [It is known that the crystallinity and solubility of calcium phosphate can be controlled by adding suitable additives to the reactants . It is ant cells . The incnt cells . FurtherThe optical and physical properties of dental composites are highly influenced by the composition of the resin matrix and fillers. Variables include: (i) the resin matrix type and its amount; (ii) the size, shape, and amount of inorganic fillers, (iii) the interaction of the resin matrix and the fillers; and (iv) the amount and type of the photo-initiator system ,43. TranThe translucency of composite formulations is highly dependent on the refractive index match of the filler phase and the resin phase . A typicThe degree of conversion is an important tool to determine the final physical, mechanical, and biological properties of dental composites. The correlation between the degree of conversion and the mechanical performance of photopolymerized dental composites has been well studied . The degThe depth of cure of dental composites is clinically relevant and is defined as “the thickness of a resin that may be converted from a monomer to a polymer, under a specific light curing condition” . Depth oIn this study, to investigate the effect of the added MCP filler on translucency, degree of conversion, and depth of cure, all composite formulations contained the same resin composition, photo-initiator system, inorganic fillers, and shade. It was found that replacing some of the inorganic filler with an equal amount of MCP improved the translucency parameter, increased the depth of cure, and showed a similar degree of conversion over that of a control composite without MCP. The higher translucency parameter and depth of cure of a composite with 3 wt.% MCP was attributed to the higher interaction and solubility of the MCP filler with the resin phase. The composite with 6 wt.% MCP exhibited a lower mean degree of conversion of 64% and slightly lower depth of cure, but had a similar mean translucency parameter as the control composite with no MCP. On the other hand, composite with 20 wt.% MCP showed the lowest mean value for translucency parameter (5.5), degree of conversion (58%), and a mean depth of cure (2.48 mm). The low depth of cure of CS-20 may be attributed to the higher paste viscosity of the formulation. All tested composites have acceptable depths of cure for clinical application.The mean flexural strength of the composites with MCP filler was tested by a three-point ISO 4049 method. Composite with 3 wt.% MCP presented the highest flexural strength (106 MPa), which was slightly higher than that of the control composite (98.2 MPa). The composite with 6 wt.% MCP showed slightly higher mean flexural strength compared to the control composite, but the difference was not statistically significant. The composite with 20 wt.% MCP showed the lowest mean flexural strength of 92.6 MPa. The lower values were attributed to the lower degree of conversion due to the high paste viscosity and reduced filler-resin interaction. All composite formulations exhibited good toughness values, which were evidenced by high flexural strength and high deflection at break. The high toughness of the dental composites studied in the present work is attributed to the incorporation of the rubberized urethane in the resin matrix of the composite formulation. Composites with higher toughness and flexural properties enhance the fatigue strength and longevity of dental restorations ,49. The 2. The release of calcium and phosphate ions is highly influenced by the nature of the resin matrix and the amount of the functional calcium phosphate filler, MCP. The hydrophilic character of the resin matrix plays a significant role in the ion release properties of the experimental composites, and is impacted by the addition of a small amount of phosphate monomer (Bis-2) to the resin matrix. The release of calcium and phosphate ions occurs after the interaction of composite with water or saliva in the oral environment. The release of calcium and phosphate ions from the dental composites was directly correlated to the amount of MCP in all experimental composites. Sustainable releases of calcium and phosphate ions were observed in all experimental composites with MCP fillers over a period of four weeks. Dental composites that release adequate amounts of calcium and phosphate ions have been demonstrated to achieve dentin lesion remineralization [The ion releasing properties of the experimental composites with MCP were studied in distilled water over a period of four weeks. The ion release data is presented as micrograms of ions released per cmlization . In an elization . Composi+ and Si+ ions) from the glass; a polycondensation reaction of surface silanols to generate a large number of heterogeneous nucleation sites; and crystallization of biologically reactive hydroxyl carbonate apatites in contact with a phosphate-containing medium  [The biomineralization pathway of MCP containing composites is different from that of bioglass 45S5 or that of calcium-silicate based dental products. In bioglass 45S5 and calcium-silicate based products, such as TheraCal  and MTA , there is a rapid release of soluble ionic species  . In MCP The role of the experimental composite’s polyionic resin matrix on the biomineralization process can be further understood by application of various theories proposed by researchers ,52,53. A−1, 963 cm−1, 603 cm−1, and 563 cm−1  enables the creation of highly mineralized, durable, polymer-based composites with mono-functional, di-functional, or multi-functional monomers.The patent “Stabilized calcium phosphate and methods of forming same” US patent 10,219,986 dated 03-05-2019 resulted from the work reported in this manuscript.


The objective of this study was to characterize the effects of intramuscular botulinum toxin (BT) injections on the electromechanical delay (EMD) in spastic human biceps muscles. The EMD is calculated as the time lag between the muscle activation onset, as recorded from the surface electromyogram (sEMG), and the onset of recorded force. In a cohort of chronic stroke survivors, we compared the computed EMD derived from the spastic (injected) biceps brachii with that from the contralateral muscle. Eight participants were tested before and up to 3 months after a BT injection. At each session, participants followed an isometric trapezoidal force trajectory at 50 and 30%, respectively, of the tested maximum voluntary contraction (MVC). Joint force and sEMG signals were recorded as well. The number of zero crossings (ZC) of the sEMG during the steady-state portion of the task was also computed. The EMD post-BT was found to increase by 64 ± 10% (at 50% MVC) and 93 ± 18% (at 30% MVC) when compared to pre-BT values, while the number of sEMG-ZC, the mean MVC values, and the force-EMD slope exhibited striking reductions. These parameters, calculated on the contralateral side, remained relatively constant across sessions, with the EMD significantly lower and the MVC values much higher. We discuss potential contributing factors to an increase in EMD values on the affected side, both pre- and post-BT. The observed co-variation across sessions of the increased EMD values with the decreased ZC estimates, a surrogate of motor outflow, and, potentially, more compliant muscle fascicles suggests that the altered motor unit (MU) behavior contributes, at least in part, to the delayed force production. The process of tension generation in the neurally activated muscle fiber begins at the neuromuscular junction, followed by a cascade of electromechanical events . There iIn general, the electromechanical delay, which is partly a function of a muscle's rate of force generation, depends on two major factors: (a) the number of recruited motor units, and (b) the electro-mechanical properties of the muscle-tendon unit (MTU). The latter is dominated by intrinsic stiffness of the muscle and tendon . Neural Botulinum toxin reduces hypertonia and hyperreflexia by means of the chemodenervation at the neuromuscular junction (NMJ) . GeneralHaubruck et al. have studied the passive biomechanical properties of the muscle-tendon unit in the healthy mouse gastrocnemius muscle during stretching, and have reported a decrease of stiffness by 25% after the botulinum toxin . Howren In the last few decades, the EMD values have been quantified by several researchers in humans under several conditions. The EMD value during a voluntary contraction of the biceps brachii (abbreviated to biceps from hereon) in intact subjects was reported to be 75 ms  and 80 ±Lacourpaille et al. have studied the human biceps muscle during electrically evoked contraction and have found that 56% of the EMD is contributed by the muscle during an active force generation, while the rest is by the MTU . Mörl etThe number of turns in an sEMG signal has been used by several researchers as a rough measure of the MU activity during a voluntary contraction of the muscle as shown experimentally . During Although the clinical consequences of BT have been widely investigated , 33, theAccordingly, the objective of the current study is to characterize and to understand the effects of BT on the electromechanical delay by computing the EMD values during the isometric voluntary contractions over a period of several weeks, in the course of multiple sessions in the post-injection period. We have measured the force and the sEMG during the isometric voluntary contraction in eight stroke-affected individuals who were injected with BT, as a part of their standard clinical care in their biceps muscle. As a surrogate measure of an MU recruitment, we also computed the number of ZCs or “turns” in the respective sEMG signal over time.We report data from eight survivors of chronic stroke, who were studied before (Pre) and after (Post-W2) a BT injection, to assess the changes in the EMD subsequent to an intramuscular BT injection on the affected spastic side only. Six of the eight tested subjects were able to continue testing to the mid-segment (Post-W6), and 5 subjects were tested until the third month (until Post-W12). We have tested both the BT injected spastic biceps and the contralateral arm at different submaximal contraction levels. Details of our tested cohort are summarized in via protocols approved by the Institutional Review Board under the Office for the Protection of Human Subjects at the Northwestern University (IRB No-STU00200242).We collected the experimental and clinical data at each session from stroke survivors, across a maximum of 3 months per subject. Approximately, there were over 45 total experimental recording sessions in both stroke-affected and contralateral arm muscles. The contralateral recordings were performed in separate sessions using the same protocol. The recordings from the contralateral side were used for comparative purposes as normative (non-injected) experimental data. Details of our experimental process, data collection, and analysis are summarized in the following section. All participants gave an informed consent Two types of sEMG electrodes were used during the experiment. A single differential surface electrode (SD-sEMG)  was placed over the muscle belly in the distal region of biceps, along the fiber direction. The single differential sEMG preamplifier has a bandwidth of 20–450 Hz for surface signals, amplified by a factor of 1,000, and sampled with a band-pass filter of 20–450 Hz . The force and single differential EMG signals were digitized at a rate of 2 kHz . Force and sEMG signals were then collected and were visualized online using a software program from CED, Spike2 (version 7), and were stored on a personal computer for later analysis. The synchronized data allowed an accurate determination of the onset of sEMG in relation to the onset of torque production .In order to analyze the zero crossings of the sEMG, we utilized recordings from a novel 4 channel sensor array (SA-sEMG) electrode . The senvia a metal ring to record generated force. The other end of the load cell was firmly attached to a stable iron platform through fixture arrangements. A rubber pad was placed under the elbow to keep the forearm parallel to the ground. To restrict trunk and shoulder movement a pair of Velcro straps was attached around the subject, to the Biodex chair.Subjects were positioned in an upright sitting posture on a Biodex chair. Their upper arm joint angles were fixed at elbow flexion 120°, shoulder flexion 10°, shoulder abduction 35°, and the forearm pronation to 45° for maximum activations of biceps muscle during the elbow flexion. To further ensure isolation of the biceps, and thereby reducing contamination of force production from other muscles, the forearm was secured in a custom-made fiberglass orthopedic cast used from above the elbow up to their fingertip. A rigid 6 d-o-f force-torque sensing load-cell  was mounted on the wrist r) was calculated as the vector summation of the Fx and Fz recorded from the sensor. Real-time feedback of the force response was provided on a computer monitor. Two-dimensional visual feedback of the force trajectory in the desired quadrant plane assisted the participants to track and to maintain their force profiles as required. Details of the experimental setup and the processing are provided in Voluntary contraction force and sEMG data were recorded during a sustained isometric non-fatiguing elbow flexion task; first, in a maximum voluntary contraction (MVC) trial, then in subsequent trials of submaximal levels at 30% MVC and 50% MVC. Three good trials were performed (with an average error within 10% of the instructed trajectory) at each level with different levels performed in a randomized sequence. During each trial, all forces were simultaneously collected with an sEMG. The resultant force , then by the submaximal steady-state contraction level for a period of 10 s, and a decreasing force level at the rate identical to the rate of increment. The average FWe define the electromechanical delay as the time delay between the onset of the sEMG and the onset of force production during the increasing phase of the force trapezoid. After the initial qualitative inspection, the method was programmed to automatically detect the onset of force production. The location, where the magnitude of the sEMG trace exceeded a statistical threshold above the background noise level, was determined using a sliding window (50 samples long) as shown in To reduce the possible effects of noise in the system, 1,000 samples (500 ms) were selected from the sEMG and the force recording channel during the resting period prior to each contraction to determine the respective baseline values. The mean and the standard deviation of the selected resting period activity were calculated, the values for the affected side are summarized in The time of the initial sample of the window will be recorded, if the mean of the samples in the window exceeded the threshold. If the mean of the samples in the window did not exceed the criteria, the window was advanced one sample at a time until an onset was found. The time difference between the onset of sEMG and force was determined for both trials at each contraction level.ETH was defined as:The ZCs of the sEMG were measured during the steady-state of the force trajectory. The trials for which the EMD were detected were further analyzed for the calculation of ZC. We have only considered one incident of ZC between successive positive and negative peaks detected in sEMG. All the sEMG peaks were detected in a 5-s window (with a minimum variation of the force trace) in the sensor array sEMG signal during the steady-state period for the force trajectory. The region was selected with a minimum force variation of the resulted force trace. This sensor array recording channel, with the highest peak to baseline value, was selected for the peak analysis. The small electrode area and the high recording sampling rates of the sensor array further supported the precise detection of representing the MU firing instances. More detailed descriptions of the sensor can be found in . The sigWhere μ and δ are the mean and the standard deviation of the baseline sEMG signals before the start of the voluntary activation . The avep < 0.05.The normality of the data was analyzed by the Kolmogorov Smirnov test and the non-normality was confirmed . ThereafThe EMD values were calculated in both the stroke-affected side and the contralateral side. The EMD values were systematically higher on the affected side (79.7 ± 9 ms at 50% MVC and 127 ± 18 ms at 30% MVC contraction levels) compared to the contralateral side (25 ± 12 ms at 50%MVC and 45 ± 9 ms at 30% MVC contraction levels), as shown in p < 0.01) increase after the injection (at Post-W2) at both contraction levels compared to their respective pre-injection baseline values. In the affected side, a maximum increase of 64 ± 10 and 93 ± 18% of the EMD values were observed respectively at 50 and 30% MVC levels during Post-W2 compared to the pre-injection values as shown in 0 < 0.05, χ2 = 7.93). A decaying trend of the EMD values was observed in the following experimental sessions after Post-W2. Finally, at the end of 12 weeks (Post-W12), the EMD values decreased to 7 and 26% for the respective contraction levels as summarized in r = 0.86 ± 0.04 with p < < 0.05) was found among the time course of the EMD values at two contraction levels.Experiments were conducted longitudinally as discussed in the methods section. The EMD values were calculated across the sessions before and after the BT injection. The maximum voluntary contraction (MVC) force values, and, thus, the submaximal contraction values are varied across the post-BT recording sessions. r > 0.68) within the force and the EMD values. In order to assess the changes in the relation between the force and the EMD, the slope of the linear fit was analyzed across the experimental sessions. The slope values of the linear fit were found to systematically vary in the injected side for all the subjects as shown in The force and the EMD values were measured respectively during 30, 40, and 50% of the MVC level across the experimental sessions. After the injection, a linear regression line was fitted (min p = 0.0113) reduction of 3.5 times compared to the pre-injection values. The reduced slope value persisted until 12 weeks for the subjects (p = 0.006) compared to its pre-injection slope value. Despite the increase of the slope values compared to the post W2 were observed from Post-W6 onward, even at the end of 12 weeks (Post-W12), the values were found to be significantly lower than the pre-injection value recorded at −1.19. During this session, the slope values in the contralateral side remained high in all the experimental recording session across the time course, and the variation recorded were within 20% of all the contralateral values recorded among the subjects.During the pre-injection recording session, the slope values in the injected side (−0.49 ± 0.16) were found to be lower than the contralateral side (−0.22 ± 0.07). At Post-W2, the slope value in the affected side showed a statistically significant  than the contralateral side for all the subjects when compared to the respective contraction level. p < < 0.05) for the test cohort.The number of ZCs in the affected side was reduced after the BT injection, and the average ZCs among the subjects were found to be lower than the pre-injection baseline recording. The reduction of the number of ZCs was statistically significant (p > 0.08) for all the subjects at all contraction levels.The average reduction of ZC was 50 ± 16, 74 ± 24, and 18 ± 11% at Post-W2, Post-W6, and Post-W12, respectively, compared to the pre-injection value of the respective subjects. The number of ZCs did not return to the baseline pre-injection values when compared individually for the subjects who have studied for full 12 weeks apart from B5. Unlike the injected side, the number of ZCs across the sessions in the uninjected contralateral side remained relatively unchanged with a statistical significance . The average reduction in the slope values for the subjects at Post-W2 was 38 ± 31% compared to the Pre-session. The force-ZC slope values did not recover to the pre-injection baseline level by Post-W12. While the systematic reduction of the force-ZC was observed in the affected side, the contralateral side values did not change significantly, and no systematic difference was found.The goal of this study was to investigate the time-course of the EMD during isometric voluntary contraction in spastic biceps muscle followed by a clinically prescribed injection in the muscle of our tested cohort. Our results show that estimating EMD might provide an insight into the changes in neural control—i.e., changes in recruitment of motor units due to a BT-induced chemodenervation in spastic biceps muscle. We have measured the EMD between the sEMG activation and the resulting detectable elbow contraction force at various levels of contraction. Simultaneously, we have studied the number of ZCs in the sEMG signal based on a novel sensor array recording. Recordings from the contralateral side were used as a control reference  for the experimental analyses.The primary finding of this study was that the EMD values increase by 64 ± 10% (at 50% MVC) and 93 ± 18% (at 30% MVC), respectively, during the first recording session after the BT (Post-W2) for our test cohort, while the mean force value was also reduced by 8%. We have found maximum EMD values that occurred during the first post-injection session (Post-W2). Thereafter, the values declined gradually during the following sessions in the later stage (at Post-W6 and W12). Concurrently, the force also partially recovers back from its minimum value among four of the six subjects (except B3 and 4) who were studied for additional sessions after the initial session (Post-W2).Despite the partial recovery of the following sessions, there exists a 7 and 15% prolongation in the EMD values during session Post-W12 compared to the Pre-session baseline as shown in The highest antispastic effect of the BT induces the denervation found within 1 month of the injection affecting the contraction force and the sEMG. This has been reported earlier by several groups including us , 43.We have observed higher standard error in the EMD values at lower force levels. This is potentially due to the variation in the effect of BT in the muscle as suggested by earlier groups . A majorSince a functional alteration of the MU pool will be reflected in the sEMG, we have used the zero-crossings value of the sEMG signal as a surrogate of the recruited MU , 30. TheOur results show a dramatic reduction in the number of ZCs among our subjects that may signify a reduced number of active fibers. A reduction of active fibers after BT injection was reported earlier . We haveReduction in the force-ZC slopes provides a means of comparing the ZC despite the reduction of the contraction force during the post BT session to the respective pre-injection baseline values. Reduction of the force-ZC slope at Post-W2 indicates a disproportionate reduction of the motor outflow compared to the reduction in force in the BT-injected muscle.Disproportionately larger reductions of contraction force may have two reasons:  A changeIn order to understand the relation between EMD and the neural drive to the active MN pool, we have studied the force EMD slopes. The negative slope values for all the subjects across all the recording sessions indicate a negative correlation between the MVC levels and the EMD values  compared to their pre-injection level. This may be attributable to the architectural limitations of the shortcoming in a spastic muscle during the contraction, which also played an important role in the force generation . Moreove comparedComputation of the EMD critically depends upon the calculation method and the nature of the muscle activation task. We have defined EMD as a time delay between the detected onset of the sEMG and the respective voluntary contraction force . ExistinEMD is, in part, a measure of functional architecture and internal disruption of the muscle. This study provides a quantitative characterization of changes in the EMD and the number of zero-crossing in the sEMG signal after the intramuscular BT injections in stroke survivors, which allowed us to understand the effects of BT more clearly on voluntary contraction. The results suggest that the BT-induced reduction of spasticity results in a reduction in voluntary contraction capacity in association with the increased EMD value. The increase in EMD indicates that the BT disrupted both the fascicle architecture and the normal mechanics of force production that contributed to the clinical impairment. We have further shown the increase in EMD is at least, in part, contributed by the reduced number of firings, which was measured in terms of the zero-crossing in the sEMG signals, and does not come back to its pre-injection baseline after 12 weeks. The result of this study is the first evidence of a change in EMD affecting the force production capacity after the BT injection.The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.The studies involving human participants were reviewed and approved by the Institutional Review Board at Northwestern University (IRB No. STU00200242). The patients/participants provided their written informed consent to participate in this study. Written informed consent was also obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.SC, BA, WR, and NS participated in the study conception, design, data analysis, and interpretation. SC, BA, and NS participated in data acquisition. All authors read and approved the final manuscript.This study was funded by the National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR-90RE5013) through Advanced Rehabilitation Research and Training (ARRT) and Rehabilitation Engineering Research Center (RERC) program.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. 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To determine the relationship between the level of quality of professional life and the characteristics of the burnout syndrome of the nursing staff in the intensive care unit.An analytic cross-sectional study was conducted in the intensive care unit of a public hospital in Mérida (Venezuela), with the participation of 40 nurses from a total population of 43. The Professional Quality of Life of 35 items (QoPL-35) and Maslach Burnout Inventory scales were used.. The professional quality of life was regular (median = 213), the intrinsic motivation dimension was the best scored (median = 76), followed by that of workload (median = 68) and that of directive support (median = 65). The prevalence of high burnout syndrome was 22.5%; emotional exhaustion affected 75.5% of the participants and 37.5% had low personal achievement. The level of professional quality of life was related with the severity of the burnout syndrome (p=0.04).Of the participants, 67.5% were professionals and 32.5% were residents, < 41 years of age (75%) and of female sex (90%)The professional quality of life of the nurses in the ICU studied was regular and is associated with a higher risk of suffering severe burnout syndrome. Professional quality of life (QoPL) is the emotional state resulting from the interaction between the demands of work and the resources  available to satisfy them. A Good QIn areas dedicated to caring and direct interaction with people, like health institutions, it is vital to comprehend the behavior of the QoPL and its influence on the quality of services provided to patients, with emphasis on the nursing staff who, besides being the most numerous component of the health staff, due to their work dynamics are prone to emotional burnout, perceiving low QoPL, and job dissatisfaction.,5 In speThe BS is an occupational disease consequeIn the nursing staff working in the ICU, it is common to find the association of low QoPL and higher severity of BS, a phenomenon that has negative consequences, like increased frequency of errors related with caring, deterioration of interpersonal relations, anxiety, emotional isolation, greater rate of resignations, diminished quality of care of patients, physical exhaustion, insomnia, depression, cynical treatment of patients, diminished job performance, lack of motivation, increased work absenteeism, consumption of alcohol and tobacco; situatioIn view of the severe sequelae that accompany a low QoPL and the BS, and of the relationship that exists between both conditions, it is necessary for health institutions to have up-to-date information about their characteristics to design timely strategies to maintain optimal levels of QoPL and avoid the development of the BS.-6 The obInstituto Autónomo Hospital Universitario de Los Andes in Mérida-Venezuela from July to September 2019, with participation by 40 of the 43 nurses who constituted the total population, including professionals with academic degrees in intensive care  and graduate nursing degree students in intensive care (residents). The inclusion criteria had to do with having at least three months of continuous work in the unit at the moment of the study, performing functions related with direct care of critically ill patients. Three nurses were excluded; two were in administrative assignments and one manifested the desire to not participate.A cross-sectional study was conducted in the intensive care unit at the Prior to collecting the study information, a brief induction was made on the theme; informed consent was requested for participation and a 15-day limit was established to deliver an administrative form answered anonymously, containing: (1) sociodemographic data; (2) the Spanish version of the Quality Professional of Life Questionnaire (QoPL-35) instrument or Quality of Professional of Life (QoPL-35) questionnaire, which waThe severity of the BS is established according to the severity of the dimensions that compose its fundamental nucleus . However, for the instrument’s authors, work and specially that related with direct care of patients represents in itself a risk for developing BS; which is why no category exists that excludes it in its entirety, considering that all the nurses have at least a low level of such.p value ≤0.05. The statistical analyses were performed with the SPSS program version 21 . This study was approved by the ethics committee and competent authorities at Instituto Autónomo Hospital Universitario de Los Andes.The quantitative data are shown through medians, interquartile range, and maximum and minimum values; qualitative data are presented in frequency tables. To establish the level of each dimension from the QoPL-35 questionnaire, a division was carried out in tertiles establishing three categories: high, medium, and low for each of them. The statistical relations were determined  through the chi squared test, considering significant a Of the 40 participants, the mean age was 35.5 years (range from 24 to 70 years), highlighting two age groups; those < 30 years of age (37.5%) and those from 31 to 40 years of age (37.5%); the female sex represented 90% of the sample; 47.5% manifested being single; 40% had no economic dependents; and 57.5% had - at the time of the survey - less than 5 years of work experience in ICU. It is highlighted that 67.5% are professionals with degrees in intensive care, 57.5% reported having only one job (in the institution where the study was conducted), and the majority of the nurses (55%) work by alternating day and night shifts .The professional quality of life of the 40 participants is regular (median = 213), the dimension of intrinsic motivation was the best scored (median = 79), followed by the dimensions of workload (median = 68) and directive support (median = 65). The perceived professional quality of life (independent question) obtained a median = 5 that is within the category of somewhat or regular .Through the division by tertiles of the dimensions of the QoPL-35, it was established that only 40% of the participants perceive high directive support, 37.5% considered being exposed to high workload, and 70% has between medium and high intrinsic motivation. .Through the Maslach Burnout Inventory instrument, it was determined that 22.5% of the nurses have high burnout syndrome, 65% medium, and 12.5% low. Emotional exhaustion affects 77.5% of the participants, 37.5% has low personal achievement, and only 15% manifests high degree of depersonalization. . p = 0.002).Significant statistical association exists between some sociodemographic characteristics and the dimensions of the QoPL-35 questionnaire; thus, it is evident that intrinsic motivation is higher in participants with 1 to 2 economic dependents; nurses with > 10 years of professional practice in ICU perceive greater workload, professionals have greater intrinsic motivation and perceive higher directive support than the residents, however, they have a higher workload . LikewisMedium and high BS prevalence is higher in participants > 41 years of age, with 11 or more years of professional practice and with regular professional quality of life; in contrast, younger nurses, less time of professional exercise, and good QoPL tend to have lower severity of the BS . p=0.015) and with greater workload, lower personal achievement is perceived (p=0.009).Moreover, it was determined that significant relations exist among the dimensions that compose both instruments; lower directive support indicates higher emotional burnout (et al.,(et al.,(et al.,(In the ICU, the nursing staff is exposed to high and sustained levels of stress, mental, physical, and emotional exigencies that predispose them to physical wear, job dissatisfaction, emotional burnout, low QoPL, and development of the BS with negative effect in their performance, health and quality of the care provided to patients.,10 This et al., and Fern,(et al., a situat,(et al., who alsoet al.,(et al.,(et al.,(et al.,(et al.,(The diagnosis of high BS has a prevalence of 22.5%, far surpassing the findings by Maticorena-Quevedo et al., and Salg,(et al., who addi,(et al., where em,(et al., deperson,(et al.,et al.,(et al.,(et al.,(et al.,(Significant statistical associations exist between the sociodemographic characteristics and the dimensions that structure the QoPL-35; thus, similar to the findings by Fernandez-Araque et al., the staf,(et al., professi,(et al., professi,(et al., the partet al.,(et al.,(et al.,(et al.,(This research demonstrated a significant statistical relation among the severity of the BS, age, and time of professional practice; participants in the age group of 41 or more years and with > 10 years of professional practice have a higher prevalence of medium and high burnout syndrome, these results differ from Mefoh et al., and Mole,(et al., who foun,(et al., and Kwak,(et al., a lower As a limitation, it must be stated that this was a study in a single hospital center and of cross-sectional design, making it difficult to extrapolate the results to other ICUs in the country. However, these results offer valuable and relevant information from the administrative point of view upon identifying points susceptible to intervention to improve the QoPL and diminish the BS prevalence and avoid its unwanted effects.This research permits concluding that the QoPL of the nursing staff in the ICU studied is regular, high intrinsic motivation of the staff exists, workload is high, and 60% of the nurses perceive that directive support is from low to medium. The different dimensions that compose the QoPL have different behaviors related with age, time of professional exercise in ICU, number of economic dependents, and academic level. The high BS prevalence is significantly above that described in other research from the region; emotional exhaustion affects 77.5% of the participants and 37.5% has low personal achievement, however, depersonalization remains in low levels. It was demonstrated that the regular level of QoPL is related with higher severity of the BS.According to the authors’ knowledge, when conducting this study, no evidence was documented on the professional quality of life of the nursing staff in an ICU in Venezuela, which is why their behavior and association with the BS was totally unknown.