RESUMO
STATEMENT OF PROBLEM: The digitalization of completely edentulous arches presents limitations because of the lack of anatomic structures for best-fit alignment during the image generation process of the scanner's software program. PURPOSE: The purpose of this clinical study was to evaluate a new device for intraoral scanning and to analyze its usefulness in capturing the 3-dimensional (3D) position of implants in edentulous mandibular arches. MATERIAL AND METHODS: The 3D positions of 40 implants in 10 participants with fixed interim mandibular prostheses were evaluated by comparing 3 scanning techniques. Images were generated in 2 experimental groups, with digital scan bodies (group SC) and with the scanning device (group SD) and in a control group (group CT) in which images were obtained by laboratory scanning of casts produced from splinted impression copings. The standard tessellation language (STL) files were superimposed by using a reverse engineering software program to measure the 3D coordinate system. Variations in implant linear displacements (Δx, Δy, and Δz), total 3D displacement (Δx2+Δy2+Δz2), and angle projections (ΔθXY, ΔθXZ, and ΔθYZ) were statistically analyzed (α=.05). The distances between the implants were also measured. The Spearman correlation coefficient (α=.05) was used to find the correlation between the 3D coordinates and the distances between the implants. RESULTS: Group SD had lower values for linear displacement than group SC; however, this difference was not statistically significant except for implant #2. The overall evaluation showed a significant difference with better accuracy for group SD. Concerning angular displacements, group SD showed lesser angular variation for the 3 projection planes. For the distances between the implants, significant differences were only observed for the "all" assessment in which group SD behaved similarly to group CT, while group SC showed the highest values (P<.05). No correlation was detected between the axes (x, y, and z) and the distances between the implants. CONCLUSIONS: The evaluated scanning device led to improved trueness for linear, angular displacements, and distances between implants in mandibular edentulous arches.
Assuntos
Implantes Dentários , Boca Edêntula , Humanos , Técnica de Moldagem Odontológica , Modelos Dentários , Desenho Assistido por Computador , Imageamento TridimensionalRESUMO
STATEMENT OF PROBLEM: Removable partial dentures (RPDs) are traditionally made by casting, a complex, error-prone, and time-consuming process. Computer-aided design and computer-aided manufacturing (CAD-CAM) RPD systems may simplify the clinical steps and minimize errors; however, the accuracy of CAD-CAM RPD systems is unclear. PURPOSE: The purpose of this systematic review was to determine whether CAD-CAM systems are accurate for the manufacturing of RPD frameworks. MATERIAL AND METHODS: A literature search was conducted through Medline-PubMed, Scopus, Lilacs, Web of Science, and Cochrane Library databases using specific keywords for articles published up to November 2019. Three reviewers obtained data and compared the results. All studies evaluated the framework accuracy or fit of prostheses fabricated with conventional and digital techniques. RESULTS: A total of 7 articles, 2 clinical studies, and 5 in vitro studies that complied with the inclusion criteria were evaluated. One in vitro study compared indirect (extraoral) and direct (intraoral) scanning for partially edentulous ridges and shows that digital scans were better than conventional impressions in terms of trueness. In the other studies included, although the frameworks analyzed had clinically acceptable discrepancies (<311 µm), the material influenced the fit. Polyetheretherketone (PEEK) showed better fit than traditional metal cast RPDs. Co-Cr alloy RPDs produced by rapid prototyping exhibited the highest discrepancies when produced by sintering laser melting. CONCLUSIONS: The results show that the digital technique for RPD frameworks is accurate. In the studies included, the analyzed frameworks had clinically acceptable gaps, but the results were heterogeneous among studies because the articles used different measurement methods with small sample sizes. Few studies discussed the long-term clinical performance. The digital technique for RPD frameworks was accurate because the misfits and mismatches found in in vitro and clinical studies were within the acceptable clinical limit for RPDs.