Comprehensive Evaluation Of The Effect Of Dental Unit On The Dimensional Accuracy Of Cocr Multi-Unit Fixed Bridge

To study the effect of units on dimensional accuracy through comprehensive assessments. SLM technique (SLM group) and conventional casting (CAST group) were used to produce 40 FPDs, respectively. A total of 40 specimens of each group were divided into 5 subgroups, including 6 units (n = 8), 8 units (n = 8), 10 units (n = 8), 12 units (n = 8), and 14 units (n = 8). The vertical error was expressed by measuring the edge clearance using the silicon replica. Horizontal and local errors were measured by reverse engineering. The surface of the SLM and CAST specimens was observed by SEM. One-way analysis of variance (one-way ANOVA) and Tukey-post-hoc analysis were used to compare inter-group differences of different units. The t-test (a = 0.05) was used to analyze the difference between SLM and CAST in the same unit. The average value of vertical, horizontal accuracy and surface errors of SLM were better than those of CAST group (P < 0.05), but vertical, horizontal accuracy of 12 and 14 units were statistically different from 6, 8, 10 in SLM group (P < 0.05). In cast group, a statistically significant difference was shown among different subgroups in vertical, horizontal accuracy and surface errors (P < 0.05). On SEM observation, the surface of SLM specimens was relatively flat and regular, with less spheroidized protuberance. In conclusion, the number of units had an effect on dimensional accuracy of SLM FPDs when it was higher than 10. SLM technology is superior to conventional casting in size accuracy and surface quality.