Fracture resistance of dowel channel preparations with various dentin thickness.

This in vitro study consisted of 40 cast dowel core made of technique metal alloy. They were divided into 4 groups of dowel channels with 1 mm facial dentin thickness, 2 mm facial dentin thickness, 1 mm facial dentin thickness with 60 degrees bevel for the metal collar and 2 mm facial dentin thickness with 60 degrees bevel in the metal collar, respectively. The fracture resistance under horizontal force were compared by using Instron machine. From the study, it was found that more than 1 mm thickness of labial dentin wall of post channel is required to prevent root fracture under horizontally directed force and an addition of 2 mm collar in the core around the root enhanced the resistance to root fracture. It was also found that adequate post diameter should be present when technique metal was used to prevent dowel failure due to bending under force.