Supplementary Material for: In vitro effect of occlusal loading on cervical wall lesion development in a Class II composite restoration.

Aim: determine the effect of simulated occlusal loading on wall lesion development in cervical gaps of Class-II composite restorations in vitro. 64 extracted human molars received standardized (4.0x4.2x3.0 mm) box preparations. The teeth were randomly assigned to one of two restoration groups: restoration with a normal or a low E-modulus composite material (Clearfil AP-X: E-modulus 16.8 GPa; or Clearfil Majesty ES Flow: E-modulus 6.6 GPa). A metal matrix was placed at the bottom of the box for each restoration, creating a cervical gap of about 100 µm wide. Samples were exposed to simulated caries lesion development in a lactic acid solution (pH 4.8) for 8 weeks in a Rub&Roll device. Half of the samples were subjected to 90N cyclic loading. After demineralisation, the teeth were sectioned. Wall lesion development was measured using microradiography (T-WIM) in two different locations (Location 1: 1000 µm and Location 2: 1600 µm from the gap entrance) and recorded in lesion depth (µm) and mineral loss (µm*vol%). Linear regression modelling was used to estimate the effect of loading and material on wall lesion development. Mean wall lesion depth in location 1 across all groups was 150.83 µm with an SD of 61.83 µm. In location 2, mean overall wall lesion depth was 102.98 µm with an SD of 64.92 µm. Linear regression showed no significant effect of either loading or material on wall lesion development. Occlusal loading had no significant effect on secondary caries lesion development in composite class II restoration in this in vitro study.