Evaluation of non-carious cervical restorations with different cavity configurations: a microscopy and OCT analysis

The aim of this in vitro study was to assess marginal and internal gap formation in simulated non-carious cervical lesions (NCCLs) of different cavity configurations and restored with either bulk-fill or nanofilled resin composite, before and after thermocycling. NCCLs with 2.3 mm diameter and approximately 3.5 mm³ volume were prepared in 40 human molars in two cavity configurations (n = 20): saucer (1.3 mm depth) or wedge (1.9 mm depth) shape. The adhesive Clearfil SE Bond was used in all groups. These cavities were randomly divided according to the resin composite used (n = 10): Filtek Z350 XT or Filtek One Bulk Fill Restorative. The marginal and internal adaptation of the composite at cavity margins was assessed before and after thermal aging (TA) (5000 cycles between 5 and 55°C) using a plane light microscope and optical coherence tomography (OCT), respectively. The 3D images captured by OCT were analyzed by obtaining 16 B-scans per specimen using a custom-made script for software MATLAB R2019a, Update 3. Data were analyzed by two-way analysis of variance and paired t-tests (α = 0.05). Regarding the marginal gap, there was no statistically significant difference between the saucer and wedge cavity configurations, before or after TA, nor between cavities restored with bulk-fill or nanofilled composite (p > 0.05). Likewise, for the internal gap, no significant differences were found for the cavity configuration nor the resin composite (p > 0.05). Restorations placed in saucer or wedge cavity configurations showed similar marginal and internal adaptation, regardless of the type of resin composite, and gap formation was not aggravated by thermocycling.