Effect of three direct restorative materials on molar cuspal fracture resistance

This study compared the cusp fracture strength of molars restored using a condensable resin composite with that of teeth restored with conventional amalgam, a bonded amalgam, and an incrementally placed resin composite.

Standardized MOD cavity preparations (2/3 the buccal-lingual dimension x 4 mm deep) were made in 50 extracted human molars and restored as follows (n = 10): (1) a packable posterior resin composite; (2) an incrementally placed microfilled posterior resin composite; (3) a spherical particle amalgam alloy; (4) spherical amalgam with a dentin adhesive liner and (5) no restoration (preparation only; negative control). A sixth group of intact molars (n = 10) served as a positive control. Following storage and thermocycling, each specimen was tested for cuspal fracture strength.

Cavity preparation reduced cuspal fracture strength by over 50%. The fracture strength of intact teeth was significantly greater than that of all other groups (P< 0.0001). None of the restorative procedures increased cuspal fracture resistance over that of prepared teeth.