Effect of print layer height on the assessment of 3D-printed models.

INTRODUCTION: Many variables can affect the accuracy of 3D-printed orthodontic models, and the effects of different printing parameters on the clinical utility of the printed models are just beginning to be understood. The objective of this study was to investigate the effect of print layer height on the assessment of 3D-printed orthodontic models with the use of the American Board of Orthodontics Cast-Radiograph Evaluation grading system. METHODS: Twelve cases were scanned using a desktop model scanner and 3D-printed using a stereolithography-based printer at three different layer heights (25, 50, and 100-µm; n = 12 per group). All models were scored by eleven graders using the Cast-Radiograph Evaluation grading system. All models were scored a second time, at least two weeks later. RESULTS: No statistically significant effects of print layer height were found on the scoring of the models for any of the grading metrics or total score. 3D-printed models of each layer height were highly positively correlated with stone models for the total score, with the strongest correlation found with models printed at 100-µm. CONCLUSIONS: 100-µm layer height 3D-printed models are potentially clinically acceptable for the purposes of evaluation of treatment outcomes, diagnosis and treatment planning, and residency training.

Comparison of automated grading of digital orthodontic models and hand grading of 3-dimensionally printed models.

INTRODUCTION: Emerging workflows in orthodontics enable automated analysis of digital models and production of physical study models from digital files for the evaluation of treatment outcomes. The objective of this study was to compare the automated assessment of digital orthodontic models and the hand grading of 3D-printed models with the use of the American Board of Orthodontics cast-radiograph evaluation (ABO CRE) system. METHODS: Plaster models from 15 cases were scanned with the use of a desktop model scanner to create digital models from which physical models were produced with the use of a stereolithography-based 3D printer. All digital models from each case were graded with the use of an automated software tool (SureSmile), and 3D-printed models were scored by hand with the use of the ABO CRE grading system. All hand-graded models were scored a second time at least 2 weeks later. RESULTS: SureSmile gave statistically significantly higher scores to alignment and rotations (P < 0.001), overjet (P < 0.001), occlusal contacts (P < 0.001), and total score (P < 0.001). Hand grading scored higher in buccolingual inclination (P < 0.001). No significant differences were found in marginal ridges, occlusal relationships, and interproximal contacts. CONCLUSIONS: Scores assessed in an automated manner by SureSmile are generally significantly greater than those assessed by hand grading.