An in-vitro assessment of the shear bond strength of bulk-fill resin composites to permanent and deciduous teeth.
OBJECTIVES
This study aimed to evaluate the shear bond strength (SBS) of bulk-fill resin composites (RCs) to deciduous and permanent teeth.


METHODS
The following parameters were investigated: (1) tooth type (deciduous and permanent), (2) tooth substrate (enamel and dentine), (3) restorative material (a high- and a low-viscosity bulk-fill RC and a regular nanohybrid RC as control), and (4) adhesive (two self-etching adhesives). The combination of those parameters resulted in a total of 24 different groups (n=20). Permanent caries-free human molars (240) and deciduous teeth (240) were selected. The bulk-fill RCs (Tetric Evo Ceram Bulk Fill and SureFil SDR) were applied in one 4-mm increment, whereas the regular RC (Tetric Evo Ceram) was layered in two consecutive 2-mm increments. The SBS was examined after storing the specimens for 24 h at 37 °C in distilled water, followed by thermal ageing (5000 cycles between 5 °C and 55 °C).


RESULTS
Data were statistically analyzed using one- and multiway analyses of variance and an independent-samples t-test (α=0.05). The multivariate analysis (general linear model with partial eta-squared statistics) tested the influence of the parameters tooth type, tooth substrate, restorative material, and adhesive on the SBS. The parameter tooth type showed no significant impact on the SBS (p=0.576). The influence of the other parameters was significant (p<0.05) but low, and the highest influence was exerted by the parameter adhesive (η(P)(2)=0.120, p=0.0001) followed by tooth substrate (η(P)(2)=0.092, p=0.0001) and restorative material (η(P)(2)=0.028, p=0.0001). The fracture pattern was predominantly adhesive (61.9%) or mixed (38.1), and no cohesive or prefailure was registered.


CONCLUSIONS
Bulk-fill materials performed comparable or better than the nanohybrid RC used as control, but the adhesive used was the most relevant factor of influence. This material type might be clinically an option for a faster restoration in both permanent and deciduous teeth.


CLINICAL SIGNIFICANCE
Bulk-fill materials performed comparable or slightly better than the nanohybrid RC used as control. Clinically, ﬂowable bulk-fill RCs might be an advantage in restoring deep, narrow cavities, with difficult access angles, whereas larger cavities might be restored easily and faster using high-viscosity compounds.
['Ilie|Nicoleta|N|', 'Schöner|Christian|C|', 'Bücher|Katharina|K|', 'Hickel|Reinhard|R|']
D000180:Acrylic Resins D000268:Adhesiveness D003188:Composite Resins D001840:Dental Bonding D003738:Dental Cements D003743:Dental Enamel D003764:Dental Materials D003799:Dental Stress Analysis D003804:Dentin D006801:Humans D055115:Light-Curing of Dental Adhesives D008422:Materials Testing D008963:Molar D053761:Nanocomposites D019279:Resin Cements D033081:Shear Strength D013314:Stress, Mechanical D013696:Temperature D013997:Time Factors D014094:Tooth, Deciduous D014783:Viscosity D014867:Water
Shear bond strength Bulk-fill resin composites Deciduous teeth Self-adhesive