ObjectiveThe aim of this in vitro study was to evaluate the microtensile
bond strength (µTBS) to dentin of two different restorative systems:
silorane-based (P90), and methacrylate-based (P60), using two cavity models.Material and MethodsOcclusal enamel of 40 human third molars was removed to expose flat dentin
surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width
and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into
two groups (n=10) restored with P60 and P90, bulk-filled after dentin treatment
according to manufacturer's instructions. Flat buccal dentin surfaces were
prepared in the 20 remaining teeth (C-factor=0.2) and restored with resin blocks
measuring 4x3x3 mm using the two restorative systems (n=10). The teeth were
sectioned into samples with area between 0.85 and 1.25 mm2 that were
submitted to µTBS testing, using a universal testing machine (EMIC) at speed of
0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and
categorized according to fracture pattern. Data were analyzed using ANOVA and
Tukey Kramer tests.ResultsFor flat surfaces, P60 obtained higher bond strength values compared with P90.
However, for Class I cavities, P60 showed significant reduction in bond strength
(p<0.05). No statistical difference between restorative systems was shown for
Class I cavity model (p>0.05), or between Class I Cavity and Flat Surface
group, considering P90 restorative system (p>0.05). Regarding fracture pattern,
there was no statistical difference among groups (p=0.0713) and 56.3% of the
fractures were adhesive.ConclusionIt was concluded that methacrylate-based composite µTBS was influenced by cavity
models, and the use of silorane-based composite led to similar bond strength
values compared to the methacrylate-based composite in cavities with high
C-factor.