Statement Of Problem Various polymers marketed for additive or subtractive manufacturing of definitive fixed partial dentures (FPDs) have been introduced. However, studies about the accuracy and internal fit of 3-unit FPDs fabricated from these polymers are lacking. Purpose The purpose of this study was to evaluate the dimensional accuracy (trueness and precision) and internal fit of anterior 3-unit tooth-supported FDPs made of different computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials. Material And Methods A maxillary anterior 3-unit FDP was digitally designed on the right central incisor and canine abutments and manufactured using 4 different CAD-CAM materials: a urethane acrylate-based polymer developed for additive manufacturing (AM-UA), a subtractive manufacturing (SM)-based high-impact polymer composite (SM-HP), an SM-based nanographene-reinforced poly(methyl methacrylate) (SM-GP), and an SM-based lithium disilicate glass ceramic (SM-LS). Dimensional trueness and precision were assessed at 3 different regions (external, internal, and margin areas) by calculating the root mean square (RMS) error values in μm. Internal fit evaluation was performed by measuring the average gap distance (AGD) in μm with triple scan analysis. Welch analysis of variance (ANOVA) and post hoc Games-Howell comparison tests were used to statistically analyze the data (α=.05). Results For external region trueness, AM-UA was significantly better than SM-HP (P<.001). When the internal region trueness was evaluated, AM-UA and SM-LS were better than SM-GP and SM-HP (P≤.013). For marginal region trueness, AM-UA was the best among the groups (P≤.041). AM-UA, SM-LS, and SM-HP had significantly superior precision than SM-GP in terms of external and internal regions (P<.001). In addition, AM-UA had higher marginal region precision than SM-GP (P<.05). However, AM-UA showed the highest AGD, whereas SM-HP had the lowest AGD, and the differences were significant regardless of the abutment (P≤.047). Conclusions AM-UA exhibited significantly higher dimensional accuracy at the internal and marginal regions of the anterior 3-unit FDPs compared with SM-GP. Although SM-HP showed the best internal fit and AM-UA exhibited the poorest, the internal fit of all tested FDPs was close to or below clinically acceptable thresholds.
Bazelli et al. (Sat,) studied this question.