[Effect of a 10-Methacryloyloxydecyl Dihydrogen Phosphate- treated Bioceramic Sealer on the Bond Strength of an Endodontic Fiber Post: Multilayer Composite Disk Models and Ultra-highspeed Imaging Analysis].

PURPOSE: Multiple materials are found in the root canal after fiber-post cementation. The layer of a bioceramic-based (BC) sealer may affect the bond strength (σBS) of the fiber post in the root canal. The purpose of this study was to employ multilayer compos-ite-disk models in diametral compression to investigate whether the bond strength between a fiber post and root dentin can be in-creased by the application of a primer on the BC sealer. MATERIALS AND METHODS: The multilayers of materials in the root canal required 3D finite-element (FE) stress analyses (FEA) to pro-vide precise σBS values. First, BC sealer was characterized using x-ray powder diffraction (XRD) to determine when the sealer com-pletely set and the types of crystals formed to select which primer to apply to the sealer. We selected a 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-based primer to treat the BC sealer before post cementation. Ultra-highspeed (UHS) imaging was utilized to analyze the crack initiation interface. The obtained failure force was used in FE analysis to calculate σBS. RESULTS: UHS imaging validated the fracture interface at the post-dentin junction as FEA simulations predicted. σBS values of the fiber posts placed with various material combinations in the root canal were 21.1 ± 3.4 (only cement/ post), 22.2 ± 3.4 (BC sealer/cement/post) and 28.6 ± 4.3 MPa (10-MDP primer treated BC sealer/cement/post). The 10-MDP-treated BC sealer exhibited the highest σBS (p < 0.05). CONCLUSION: The multilayer composite disk model proved reliable with diametral compression testing. The presence of BC sealer in the root canal does not reduce σBS of the fiber post. Conditioning the BC sealer layer with 10-MDP primer before fiber-post cemen-tation increases σBS.

An efficient and accurate approach for fabricating dental implant surgical guides.

The aim of this research was to develop an efficient and accurate method to fabricate a dental implant surgical guide. The surgical guide is adapted from the patient's vacuum-formed clear template with the use of a plate with three ceramic balls, a six-axis drilling machine and its fixture. The plate, with the ceramic balls used as radiographic markers, is glued to the template, and the patient bites this template during a CT scan. Then, the surgeon can plan the locations and orientations of the implants on the CT-based model in the dental planning software. The drilling information is exported directly to the computer-controlled drilling machine for subsequent drilling on the template to complete the surgical guide. This method allows the surgical guide to be made without any measurements, which reduces the fabrication time, but increases the drilling accuracy. The preliminary results show that the average location error was 0.31 ± 0.17 mm and the average orientation error was 0.53 ± 0.24°, which can be considered accurate in comparison with the results reported in the literature.