Cuspal Movement and Gap Formation in Premolars Restored with Preheated Resin Composite

Objective: The current study aimed to determine the effect of preheating resin composite to three different temperatures on the cuspal movement and gap formation at the tooth/restoration interface.

Methods: Fifty extracted, sound human upper premolars were subjected to standardized MOD cavity preparations. Five groups of 10 premolars each were restored with either 1) Tetric Ceram HB, 2) a layer of Tetric Flow followed by Tetric Ceram HB, 3-5) preheated composite to 37 degrees C, 54 degrees C and 68 degrees C, respectively, using a chair-side preheating device (Calset thermal assist unit). Cuspal movement was calculated by measuring the intercuspal distance between the indexed cusp tips before restoration 5 minutes and 24 hours after composite curing using a stereomicroscope. The teeth were sectioned longitudinally and examined under a stereomicroscope connected to a digital camera and image analysis software to detect gap formation.

Results: Group 2 showed the least cuspal movement at 5 minutes and 24 hours and the highest gap area, while Groups 4 and 5 showed the highest cuspal movement at 5 minutes and 24 hours. Group 3 had the least gap area.

Conclusions: Preheating resin composite to temperatures higher than 37 degrees C increases cuspal movement. The adaptation and gap area of preheated resin composite to 37 degrees C and 54 degrees C improved, but it did not change with resin composite preheated to 68 degrees C.