Effect of Using Bulk fill Composites on Fracture Resistance of Maxillary Premolars with MOD Cavities

Bulk fill composites are an innovative class of dental resin composite materials, developed to simplify the restoration procedures, and are preferred to conventional composites if they have good mechanical properties and marginal seal. The aim of this study was to evaluate the fracture resistance of premolar teeth with mesio-occlusodistal (MOD) cavities restored with bulk and conventional composites.

In this experimental in-vitro study, 40 sound maxillary premolar teeth were randomly divided into five groups: Group I: Positive control, intact teeth. In the remaining four groups, MOD cavities were prepared. Group II: Negative control, unrestored teeth. In other groups, cavities were restored as follows; Group III: (X-tra fil, bulk filling with 4mm-thick increment), Group IV: (X-tra base, bulk filling+Grandio, incremental filling) Group V: (Grandio, incremental filling with 2mm-thick increment). The restored teeth were stored in distilled water for 24 hours at 37oC and thermocycled (500 cycles). Specimens were subjected to a compressive load until fracture, and the fracture resistance was recorded in Newton.

The highest fracture resistance values were obtained in group I (1150±507 N) and the lowest in group II (85±62.51 N), which was significantly lower than other groups (p=0.001). The fracture resistance of bulk fill composites and conventional composite did not differ significantly with intact teeth.

The restoration of teeth with moderate MOD cavity size using bulk fill composites can restore the lost tooth strength to a level comparable to intact teeth and similar to conventional composite.