Evaluation of intaglio surface trueness and margin quality of interim crowns in accordance with the build angle of stereolithography apparatus 3-dimensional printing.

STATEMENT OF PROBLEM: Studies on the intaglio surface trueness and margin quality of interim crowns fabricated using stereolithography apparatus (SLA) 3D printing depending on the type of tooth and the build angle are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effects of intaglio surface trueness and margin quality in accordance with the type of tooth and the build angles of interim crowns fabricated by SLA 3D printing. MATERIAL AND METHODS: A definitive cast was digitized for computer-aided design (CAD) reference model (CRM) production, and the interim crown was designed by using a CAD software program and saved as a standard tessellation language (STL) file. For CAD test model (CTM) production, 3D printing was performed in accordance with the type of tooth (maxillary central incisor, first premolar, and first molar) and the build angles (90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees) (n=17). The intaglio surface of the printed interim crown was digitized. CRM and CTM used 3D inspection software to analyze the intaglio surface superimposition and root mean square (RMS). In addition, a grading system was developed to evaluate the margin quality, which was assessed visually. Statistical analysis was performed using 1-way ANOVA, 2-way ANOVA, and the Tukey honestly significant difference post hoc test (α=.05). RESULTS: The RMS value showed significant differences in the various types of tooth as per the build angles (P<.001). The central incisor and first premolar showed the lowest RMS value at 180 degrees, and the first molar showed the lowest RMS value at 210 degrees. The margin quality was significantly different as per the build angle in the central incisor and the first molar (P<.05). The worst margin quality observed in all teeth was at 180 degrees. CONCLUSIONS: In 3D printing, the build angle affected the intaglio surface trueness of the interim crown. The recommended build angle for interim crowns fabricated using 3D printing is between 150 and 210 degrees. The tooth type affected the margin quality according to the build angle, except in the case of first premolars.

Comparison of Intaglio Surface Adjustment in the Oral Cavity for Lithium Disilicate Crowns Fabricated Using Different Scanners.

PURPOSE: A clinical study to evaluate the intraoral adjustment of crowns fabricated using different scanners. MATERIALS AND METHODS: A total of 15 patients requiring single ceramic crowns were recruited. Impressions were made according to four protocols: a conventional approach and using three intraoral scanners (IOSs) (CS3600 (Carestream Dental, Atlanta, GA), i500 (Medit, Seoul, Republic of Korea), and EZIS PO (DDS, Seoul, Republic of Korea)). Four crowns per patient were fabricated using lithium disilicate ceramic. An experienced dentist performed the internal adjustment in the oral cavity. Three-dimensional analysis was conducted using an inspection software program (Geomagic Control X; 3D Systems, Rock Hill, SC). Statistical analysis was conducted using one-way analysis of variance and Tukey's honest significance difference tests (α = 0.05). RESULTS: A significant difference was observed in the intraoral adjustment among the conventional approach and the three IOSs (F = 213.7, p < 0.001). Crowns fabricated by conventional impressions (20.1 ± 1.4 µm) displayed better three-dimensional conformity before and after intraoral adjustment than IOS groups (29.6 ± 4.3 µm) (p < 0.001). CONCLUSIONS: Crowns fabricated using conventional impressions required fewer intraoral adjustments of the intaglio surface than those fabricated using IOSs.

Effect of the volumetric dimensions of a complete arch on the accuracy of scanners.

PURPOSE: The present study aimed to evaluate the accuracy of a desktop scanner and intraoral scanners based on the volumetric dimensions of a complete arch. MATERIALS AND METHODS: Seven reference models were fabricated based on the volumetric dimensions of complete arch (70%, 80%, 90%, 100%, 110%, 120%, and 130%). The reference models were digitized using an industrial scanner (Solutionix C500; MEDIT) for the fabrication of a computer-aided design (CAD) reference model (CRM). The reference models were digitized using three intraoral scanners (CS3600, Trios3, and i500) and one desktop scanner (E1) to fabricate a CAD test model (CTM). CRM and CTM were then superimposed using inspection software, and 3D analysis was conducted. For statistical analysis, one-way analysis of variance was used to verify the difference in accuracy based on the volumetric dimensions of the complete arch and the accuracy based on the scanners, and the differences among the groups were analyzed using the Tukey HSD test as a post-hoc test (α=.05). RESULTS: The three different scanners showed a significant difference in accuracy based on the volumetric dimensions of the complete arch (P<.05), but the desktop scanner did not show a significant difference in accuracy based on the volumetric dimensions of the complete arch (P=.808). CONCLUSION: The accuracy of the intraoral scanners was dependent on the volumetric dimensions of the complete arch, but the volumetric dimensions of the complete arch had no effect on the accuracy of the desktop scanner. Additionally, depending on the type of intraoral scanners, the accuracy differed according to the volumetric dimensions of the complete arch.