ABSTRACT
In managing loose abutment screws, locating precisely the position of the screw access channel is difficult. This technique describes the use of cone-beam computed tomography (CBCT) and surgical guide planning software to locate the screw access channel with the intention of retrieving a loosened cement-retained implant-supported prosthesis. The method minimizes damage to the abutment crown assembly.
Subject(s)
Cone-Beam Computed Tomography , Dental Abutments , Dental Prosthesis, Implant-Supported/adverse effects , Dental Restoration Failure , Printing, Three-Dimensional , Cone-Beam Computed Tomography/methods , Dental Abutments/adverse effects , Dental Implant-Abutment Design/adverse effects , HumansABSTRACT
PURPOSE: The purposes of this study were (1) to evaluate the fit between implant frameworks and implants fabricated with two types of implant framework fabrication techniques: computer-aided design/computer-assisted machining (CAD/CAM) and conventional casting with the lost wax technique; and (2) to describe a digital measurement system consisting of tactile scanning and computer software programs that measured the volumetric differences between implant-supported frameworks and implant restorative platforms fabricated with these technologies. MATERIALS AND METHODS: This laboratory study used acrylic resin models with five interforaminal implants. The models were scanned; implant-level impressions and verification indexes were then made to construct master casts. First, a cast gold alloy framework and a titanium milled bar fabricated with CAD/CAM technology were made to clarify the construction processes of each. After this pilot study was completed, five cast and five CAD/CAM frameworks were made at each of three dental schools (15 milled and 15 cast bars). Each framework was made on a master cast from individual impressions. The implant restorative interfaces of the frameworks were scanned, and the data were entered into a computer software program. The virtual representations of the frameworks were fit onto digitized scans of the implant restorative platforms and used for virtual one-screw tests on both sides of the arch. Volumetric differences between the implant restorative platforms of the implant-supported frameworks and the model implants were measured to determine the amount of misfit between the frameworks and the model implants. RESULTS: Implant-supported frameworks made with the CAD/CAM technology fit significantly better onto the implants than the cast implant frameworks. There was a significant difference between the right and left one-screw tests; there were no significant differences among the three university sites. CONCLUSIONS: The CAD/CAM frameworks featured in this study were significantly more accurate than cast frameworks made with the lost-wax technique.
Subject(s)
Computer-Aided Design , Dental Casting Technique , Dental Implants , Dental Prosthesis Design , Dental Prosthesis, Implant-Supported , Computer Simulation , Gold Alloys , Models, Dental , Prosthesis Fitting , TitaniumABSTRACT
Component removable partial dentures (RPDs) are fabricated in pieces and assembled on the definitive cast. The treatment modality described is believed by the authors to optimize the passive fit and frictional retention of the RPD. Increased frictional retention and stability is believed to improve the clinical performance of the RPD. Patients may thereby benefit from more esthetic and more durable prostheses.