The fit of removable partial denture frameworks should be assessed to optimize clinical adaptation. Potential discrepancies between framework and supporting structures are typically precisely measured with negative subtracts and high-resolution equipment. The growth of computer-aided engineering technology allows the development of new methods for the direct evaluation of discrepancies. However, how the methods compare is unclear. The purpose of this in vitro study was to compare 2 digital methods of fit assessment based on direct digital superimposition and microcomputed tomography indirect analysis. Twelve cobalt-chromium removable partial denture frameworks were fabricated by conventional lost-wax casting or additive manufacturing techniques. The thickness of the gap between occlusal rests and respective definitive cast rest seats (n=34) was evaluated by using 2 different digital methods. Silicone elastomer impressions of the gaps were obtained, and microcomputed tomography measurements were used as controls for validation purposes. Digitization of the framework, the respective definitive cast, and the combination was followed by digital superimposition and direct measurements with the Geomagic Control X software program. Because normality and homogeneity of variance were not verified (Shapiro-Wilk and Levene tests, P<.05), the data were analyzed with Wilcoxon signed rank and Spearman correlation tests (α=.05). The thicknesses measured by microcomputed tomography (median=242 μm) and digital superimposition (median=236 μm) did not reveal statistically significant differences (P=.180). A positive correlation (ρ=0.612) was detected between the 2 methods of assessing fit. The frameworks presented median gap thicknesses under the limit of clinical acceptability without differences between the proposed methods. The digital superimposition method was determined to be as acceptable as the high-resolution microcomputed tomography method for assessing removable partial denture framework fit.

(1) Introduction: This review aimed to synthesize the significant literature addressing digital techniques for producing removable partial denture (RPD) metal frameworks, focusing on oral fit outcomes. (2) Material and Methods: A systematic review of the Web of Science and Pubmed databases was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. The selection was for original articles in English containing relevant data on RPD metal frameworks produced with digital techniques, including study characteristics, digital techniques, and fit assessment methods and outcomes. (3) Results: From the 967 search studies, 405 were duplications, and 521 were excluded after screening against set criteria. A manual search included 21 studies resulting in 62 papers for review. Extra-oral was more frequently used than intra-oral scanning. The computer-assisted design was the most applied digital technique. Additive manufacturing was preferred to milling for direct and indirect fabrication of frameworks. Fit assessments were based on qualitative measures, but quantitative evaluation showed acceptable clinical fit for RPDs made by digital protocols. (4) Conclusions: The combination of direct metal additive manufacturing with conventional impression was the most used protocol and included better qualitative and quantitative fit outcomes than the other digital protocols.

Objectives: The purpose of this cross-over clinical study was to compare the number of framework repetitions, percentage of framework components adjusted, clinical acceptability, and fit accuracy of removable partial denture frameworks produced by the direct metal laser sintering technique (DMLS) and conventional technique. Materials and methods: For each dental arch (n = 26), two cobalt-chromium frameworks were produced through two protocols: direct metal laser sintering (experimental group) and conventional lost-wax casting technique (control group). The number of framework repetitions, the percentage of components that had to be adjusted, and the clinical acceptability were registered. The fit accuracy of functional components was assessed by a qualitative method using endodontic files to identify maladjustments and compared to a quantitative method based on silicone specimens digitized by micro-computed tomography. The normality was checked (Shapiro-Wilk test), and data were analyzed with McNemar, Wilcoxon and paired-t tests (α = 0.05). Results: No statistically significant differences were found between conventional and digital frameworks for most of the variables tested (p > 0.05) except the fewer laboratory repetitions (p = 0.046), higher percentage of components adjusted (p = 0.011), and better reciprocal arms fit (p = 0.044) in the frameworks produced by DMLS protocol. No statistically significant (p = 0.174) difference was found between the fit accuracy qualitative and quantitative assessment methods. Conclusions: The DMLS and conventional protocols were similar. Despite the DMLS protocol exhibiting a higher percentage of components adjusted, it presented better reciprocal arms fit accuracy with no framework repetition. Clinical relevance: Metal frameworks can be produced using DMLS eliminating casting problems.