Influence of post types and sizes on fracture resistance in the immature tooth model

Abstract

[한글]

[영문]

When pulp necrosis of immature tooth is developed, thickness of root dentin wall remains thin for the discontinuation of tooth development, and long-term exposure to calcium hydroxide for conventional apexification procedure weakens root structures. Therefore, there is a need to reinforce root structures after apexification procedure of immature tooth. To date, various restorative techniques for root strengthening of immature tooth have been introduced, however, no treatment procedures are established as a gold standard for restoration of immature root canals. The purpose of this study was to determine the effect of post types and sizes on fracture resistance in immature tooth model with various restorative techniques.Bovine incisors were prepared to simulate immature tooth model and conventional endodontic treatments were performed. In control group, canals were restored with thermoplastic gutta-percha and resin core over 4-㎜-thick portland cement apical barrier. Specimens of experimental groups 1, 2, 3 were reinforced of dentin wall with dual-cured resin core material, followed by placement of D.T. LIGHT-POST® (Bisco Inc.) #3, ParaPost® XT™ (Coletene/Whaledent Inc.) #6, and EverStick® Post (StickTech) 0.9 individually. In group 4, several EverStick® Post 1.5 were bonded and shaped to each other according to the root canal in customized size. All of specimens were stored in the distilled water for 72 hours and underwent 6,000 thermal cycles. After stimulation of periodontal ligament structure with polyether impression material, compressive load was applied at 45 degrees to the long axis of the specimen until fracture was occurred.Experimental groups reinforced with post and composite resin were shown significantly higher fracture strength than control group without intra-radicular reinforcement technique ( p < 0.05 ). Post types did not influence on fracture resistance significantly when cement space was filled with dual-cured resin composite. In addition, no statistically significant differences were seen between customized and standardized glass fiber posts, which cement spaces were filled with resin cement or composite resin individually. Therefore, it is recommended post placement for root strengthening in immature teeth regardless of post types and sizes.