Fit accuracy in the rest region of RPDs fabricated by digital technologies and conventional lost-wax casting: a systematic review and meta-analysis

Abstract

Abstract Background Digital technologies have recently been introduced into the fabrication of removable partial dentures (RPDs). However, it is still unclear whether the digitally fabricated RPDs fit better than conventionally cast ones in the rest region. The aim of this study was to evaluate the fit accuracy in the rest region of RPDs fabricated by digital technologies and compare it to those made by conventional lost-wax (CLW) technique. Methods A comprehensive search was conducted in Cochrane Library, PubMed, EMbase, Web of Science and SpringerLink. Studies published up to August 2022 were collected. Two authors analyzed the studies independently and assessed the risk of bias on the modified methodological index for non-randomized studies (MINORS) scale. The mean values of gap distance between rests and corresponding rest seats of each study were extracted as outcome. A random-effects model at a significance level of P < 0.05 was used in the global comparison and subgroup analysis was carried out. Results Overall, 11 articles out of 1214 complied with the inclusion criteria and were selected, including 2 randomized controlled trials (RCTs), 1 non-randomized clinical trial and 8 in vitro studies. Quantitative data from Meta-analysis revealed that fit accuracy in the rest region of RPDs fabricated with CLW showed no statistically significant difference with digital techniques (SMD = 0.33, 95%CI (-0.18, 0.83), P = 0.21). Subgroup analysis revealed a significantly better fit accuracy of CLW-fabricated RPDs in the rest region than either additive manufacturing (AM) groups or indirect groups (P = 0.03, P = 0.00), in which wax or resin patterns are milled or printed before conventional casting. While milled RPDs fit significantly better than cast ones in the rest region (P = 0.00). With digital relief and heat treatment, hybrid manufactured (HM) clasps obtained better fit accuracy in the rest region (P < 0.05). In addition, finishing and polishing procedure had no significant influence in the fit accuracy in all groups (P = 0.83). Conclusions RPDs fabricated by digital technologies exhibit comparable fit accuracy in rest region with those made by CLW. Digital technologies may be a promising alternative to CLW for the fabrication of RPDs and additional studies are recommended to provide stronger evidence. Trial registration CRD42020201313.