Dental implant titanium frame work in a Articulator with zirconium crowns stop motion | FMS Dental
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Precision of Fit of Titanium and Cast Implant Frameworks Using a New Matching Formula
Osseointegrated dental implants have been proven successful in the treatment of edentulism [1]. Several techniques have been described for the successful restoration of the edentulous ridges, one being the fixed complete dentures [2]. Among the procedures used in the fabrication of those prostheses is the milled bar [3].
Meanwhile numerous articles emphasize the importance of passivity of implant-prosthetic component interfaces [4–6]. A nonpassive interface between the mating surface of the framework to its intended interface position to the implants or abutments has been implicated as a causative factor associated with implant/bone surface contact, implant screw loosening/fracture, abutment screw loosening/facture, and/or prosthetic screw loosening/fracture for abutment-based framework designs [7–9]. The conventional laboratory procedures for framework fabrication with the lost wax-casting technique are most commonly accomplished in either one piece or in segmental castings that are subsequently indexed and soldered. Discrepancies in the passive fit to its supporting abutments are occasionally encountered during the clinical try-in and evaluation appointment [10]. Frequently, the framework must then be sectioned, related in the mouth, and meticulously soldered to achieve a more accurate seating of the prosthesis to the implants. Clinically the final implant frameworks usually provide a less than absolute passive fit [11]. Nevertheless, the clinical results of applications of advanced laboratory technology to improve framework fit seem promising [12]. One of the most recent approaches to the problem of misfit is the introduction of the computer-aided design/computer-aided machined (CAD/CAM) milled one-piece titanium framework. This technique utilizes the biocompatible and relatively low-cost titanium metal and the potential for a lower risk of oral corrosion than other alloys used for implant frameworks. Further, the CAD/CAM fabrication process is less dependent on manual laboratory procedures compared to conventional casting protocols. By using an industrial manufacturing protocol for the frameworks, many factors related to manual handling of the conventional cast frameworks are controlled and avoided [13, 14].
The present investigation evaluated and compared the precision of fit of CAD/CAM one-piece titanium-fixed complete denture frameworks to that of conventional cast frameworks. Using a measurement system reported first by Jemt et al. the center point is projected in a position that is perpendicular to the component plane as the centroid point of the abutment replica [15]. This method was repeated in 2 other studies which compared the precision of fit of several types of milled fixed partial denture frameworks [16, 17]. During the present study the center point was used to determine the angular gap at the implant bar interface. The null hypothesis was that there is no differenced in the precision of interface fit between the one-piece titanium-fixed complete denture frameworks and the conventional cast frameworks.
