Adhesive Reconstruction of Vertical Dental Root Fractures

Purpose: Improvements in adhesive resins have allowed the restoration of vertically-fractured teeth. We investigated the strength of reconstructed roots as well as roots reconstructed on an abutment, and the outcome of the adhesive reconstruction/replantation of vertically-fractured teeth.<br> Methods: Experiment 1: The roots of bovine anterior teeth frozen after extraction were cut at their center parallel to the root axis. After applying Superbond C & B (SB), thermal or mechanical stress was applied before testing. Microtensile bond strength was measured, and the fractured cross-section surface was observed by scanning electron microscopy. Experiment 2: A post hole was created along the root canal, and a metal post was inserted into the hole. Vertical pressure was applied to the metal post in order to measure the initial fracture strength. Adhesive reconstruction was performed using SB. Reconstructed root fracture strength was measured when a metal post or a resin post was pressed vertically. The reconstructed root fracture strengths were compared with the initial fracture strengths, and the percent decrease was defined as the value of the sample (comparison value). The reconstructed root fracture strength after application of a thermal cycle (TC) of 5-55°C was measured, and a comparison value was calculated. Experiment 3: The initial fracture strength was measured as described in Experiment 2. After posts were bonded to reconstructed teeth, reconstructed root fracture strengths were measured in order to calculate comparison values. The results obtained were analyzed by one-way analysis of variance and Tukey’s HSD method (α=0.05).<br> Results: No significant difference was observed in the tensile bond strength among the groups. Although a significant difference was found in comparison values depending on the presence of TC loading, no significant differences were observed among different post materials. The risk of refracture in the metal post at the reconstruction site was high, whereas the risk of refracture in the resin post was low.<br> Conclusions: The durability of the root with adhesive reconstruction was less than 25% for stress parallel to the dental axis compared with that of the sound root. The risk of refracture in the metal post at the reconstruction site was high, whereas the risk of refracture in the resin post was low.