Correspondence between fiber post and drill dimensions for post canal preparation.

PURPOSE: To compare fiber posts of several calibers and trademarks to their corresponding root canal preparation drills.

METHODS: Three widely used endodontic post brands and their drills were evaluated: Exacto, ParaPost Taper Lux, and Macro-Lock Illusion X-RO. Fiber posts and drills were microphotographed with a scanning electron microscope and images were analyzed using ImageJ image processing software. Fiber post diameter on apical extreme (Pd0), fiber post diameter at 5 mm from the apical extreme (Pd5), drill diameter on apical extreme (Dd0) and drill diameter at 5 mm from the apical extreme (Dd5) were analyzed. The data were statistically analyzed using student t-test.

RESULTS: Exacto posts 0.5 showed larger dimensions than their corresponding drills (P< 0.05) at Pd0. Macro-Lock posts showed no significant differences vs. their drills at Pd0 in any of the studied groups. ParaPost drills 4.5, 5 and 5.5 were statistically significantly larger than their posts at Dd0 (P< 0.05). Exacto posts 0.5 and 1 showed larger dimensions than their drills measured at Pd5 (P< 0.05). Exacto posts number 2 showed smaller calibers than their corresponding drills at Pd5 (P< 0.05). Macro-Lock drills number 4 and ParaPost drills number 5 were larger than their posts at Dd5 (P< 0.05).

CLINICAL SIGNIFICANCE: Poor spatial correspondence between post and drill dimensions can adversely affect the film thickness of the resin cement, diminishing bond strength due to polymerization shrinkage. The lack of correspondence in size between posts and drills may lead to the formation of empty chambers between the post and endodontic obturation with excessive luting cement thickness, thus inducing critical C-Factor stresses.