Abstract
Objective This study aimed to evaluate the effects of different types and restorative techniques
of Class I composite restorations with a single loading force on stress distribution
and cyclic loading force on microleakage formation.
Materials and Methods Class I cavities were prepared in premolars with 4 mm depth and divided into six
groups of different restorations with: (1) Filtek Z250; (2) a 3-mm-thick layer of
Filtek Bulk Fill Flowable Restoration and covered with Z250; (3) a 1.5-mm-thick layer
of flowable composite and covered with Z250; (4) lining all cavity with flowable composite
and restored with Z250; (5) Filtek Bulk Fill Posterior Restoration; and (6) lining
all cavity with flowable composite and restored with bulk-fill composite. The specimens
with and without cyclic occlusal loading were subjected to microleakage observation.
In addition, six different models of Class I restorations corresponding to the microleakage
study were generated. Finite element analysis (FEA) was used to identify the stress
distribution under a single loading force.
Statistical Analysis Data were statistically analyzed by two-way analysis of variance and multiple comparison.
The significance level set at 0.05.
Results Cavity lining or restoration with flowable composite underneath conventional composite
reduced stress on composite resin based on FEA (groups 2 and 3). The cyclic stress
on composite increased microleakage. Restoration with flowable composite underneath
conventional composite reduced the microleakage in Class I restoration (groups 2,
3, and 4).
Conclusion The most effective cavity lining with a flowable composite underneath conventional
composite restoration was stress reduction under loading force resulting in microleakage
reduction.
Keywords
composite restoration - cyclic loading - finite element - microleakage - occlusal
force - stress
