Micro-computed tomographic assessment of the influence of light-curing modes on internal void formation in bulk-fill composites

Introduction:
Polymerization reactions in a new generation bulk-fill composites carried out in a short time with high irradiation, raise concerns about curing processes. With micro-computed tomographic evaluation, it is possible to investigate polymerization shrinkage, and subsequent gap and void formation in dental materials.

Objectives:
The aim of this study was to evaluate the void formation in bulk-fill composites light-cured with different modes using micro-computed tomography.

Material and methods:
Class I preparations were made in 25 molars that were randomly divided into sub-groups, according to resin composite and curing mode used: Tetric EvoCeram (TEC)*high power mode, TEC*turbo mode, Tetric PowerFill (TPF)*high power mode, TPF*turbo mode, and TPF*3s mode. Each tooth was scanned at two time intervals: pre- and post-cure.

Results:
After light-curing, a significant increase in the total volume of internal void was noted for both composites cured with high power mode compared with pre-cure. The difference between the sub-groups at post-cure was also significant. While TEC exhibited similar values in terms of different curing modes, turbo and 3s modes caused a significant difference in TPF group, and the lowest void percentage was detected in 3s mode.

Conclusions:
Internal void formation results from an interplay of different factors, including composition of materials and curing modes.