Resistance to root fracture of dowel channels with various thicknesses of buccal dentin walls.

The significance of the amount of remaining buccal dentin plate of the dowel channel in resisting root fracture under horizontally directed load was investigated. Forty cast gold dowels and cores were made for four groups of dowel channels that had, respectively, 1 mm, 2 mm, 3 mm, and 1 mm with a 60-degree bevel (collar) of the remaining buccal dentin at the entrance of the canal. An Instron tester in compressive mode was used to produce the horizontal force. Although significant differences in the failure loads for the four groups were not found, dowel channels with 1 mm of remaining buccal dentin walls were apparently more prone to fracture under horizontal impact than those that had 2 or 3 mm of buccal dentin walls. Contrary to popular belief, the addition of a metal collar did not enhance the resistance to root fracture.