PURPOSE The objective of this study was to investigate how internal structures influence the overall and marginal accuracy of full arch preparations fabricated through additive manufacturing in different printing systems. MATERIALS AND METHODS A full-arch preparation digital model was set up with three internal designs, including solid, hollow, and grid. These were printed using three different resin printers with nine models in each group. After scanning, each data was imported into the 3D data processing software together with the master cast, aligned and trimmed, and then put into the 3D data analysis software again to compare the overall and marginal deviation whose results are expressed using root mean square values and color maps. To evaluate the trueness of the resin model, the test data and reference data were compared, and the precision was evaluated by comparing the test data sets. Color maps were observed for qualitative analysis. Data were statistically analyzed by one-way analysis of variance and Bonferroni method was used for post hoc comparison (α = .05). RESULTS The influence of different internal structures on the accuracy of 3D printed resin models varied significantly ( P < .05). Solid and grid models showed better accuracy, while the hollow model exhibited poor accuracy. The color maps show that the resin models have a tendency to shrink inwards. CONCLUSION The internal structure design influences the accuracy of the 3D printing model, and the effect varies in different printing systems. Irrespective of the kind of printing system, the printing accuracy of hollow model was observed to be worse than those of solid and grid models.

Aims To evaluate and compare the clinical efficacy and the volume of occlusal adjustment of digital occlusal splints designed using an average digital articulator and the Jaw Movement Analysis System (JMAS). Materials and methods A digital impression was taken intraorally from the maxillary and mandibular dentition and from the maxillomandibular relationship record in the centric relation position. Two pairs of occlusal splints were designed, one using an average digital articulator and the other using a digital articulator whose parameters were adjusted by the JMAS. Comparing the position and volume of adjustment of each occlusal splint before and after adjustment, and to subjectively evaluate the clinical efficacy of the occlusal splints. Results The subjective scores of the occlusal splints made using the average articulator parameters and the JMAS were 9 and 11, respectively. The objective evaluation of the occlusal splints revealed that the RMS value of the average occlusal splint was 0.1932 mm, while that of the customized occlusal splint was 0.1015 mm. Conclusions The occlusal splints made with the assistance of the JMAS had a lower volume of occlusal adjustment. The two occlusal splints fulfilled all clinical requirements.