Effect of a new support design on the marginal and internal gap of additively manufactured interim crowns using direct light deposition technology.

PURPOSE: To investigate the design and location of supporting structures on the marginal and internal gap of interim restorations. MATERIALS AND METHODS: A mandibular right first molar resin tooth was prepared for a full coverage crown and scanned using a laboratory scanner (3Shape D900). The scanned data were converted into standard tessellation language (STL) format and an indirect prosthesis was designed using computer-aided design (CAD) software (exocad DentalCAD). The STL file was used to fabricate a total of 60 crowns with a 3D printer (EnvisionTEC Vida HD). The crowns were printed using E-Dent C&B MH resin and divided into 4 groups based on four different support structure designs, including supports on the occlusal (0° group), buccal and occlusal (45° group), buccal (90° group), and a new design consisting of horizontal bars placed on all surfaces and line angles (Bar) (n = 15). The silicone replica technique was used to determine the gap discrepancy. Fifty measurements were obtained for each specimen to examine the marginal and internal gaps by using a digital microscope (Olympus SZX16) at ×70 magnification. Additionally, the marginal discrepancy at different locations of the tested crowns, including buccal (B), lingual (L), mesial (M), and distal (D), as well as the maximum and minimum marginal gap intervals among groups, were analyzed. The collected data were analyzed using factorial ANOVA, followed by the Tukey HSD test for multiple comparisons (a = 0.05). RESULTS: There was a significant difference in marginal and internal gaps among the groups (p < 0.001). The buccal placement supports (90° group) had the least marginal and internal discrepancies (p < 0.001). The new design group showed the highest marginal and internal gap. The marginal discrepancy in different locations of the tested crowns (B, L, M, D) was found to be significantly different among the groups (p < 0.001). The mesial margin of the Bar group had the largest marginal gap, whereas the buccal margin of the 90° group had the lowest marginal gap. The new design had a significantly smaller difference between the maximum and minimum marginal gap intervals than other groups (p < 0.001). CONCLUSION: The location and design of the supporting structures affected the marginal and internal gaps of an interim crown. The buccal placement of supporting bars (90° printing orientation) showed the smallest mean internal and marginal discrepancies.

Prosthetic temporomandibular joint replacement (TJR): Stock or custom? A single institution pilot comparison.

OBJECTIVE: The aim of this study was to compare stock (Biomet-Lorenz Stock, Parsippany, NJ) and custom (TMJ Concepts, Inc., Ventura, CA) total temporomandibular joint (TMJ) replacement prosthetics. METHOD: This was a retrospective cohort study of 17 consecutive patients operated by the same surgeon from 2015 to 2020 comparing stock and custom options for total joint replacement (TJR). The inclusion criteria were patients who documented 1 year of follow-up post-TJR without previous TMJ replacement surgery. The predictor variable was the TMJ prosthetic replacement. The primary clinical outcome variables was pain via Visual Analog Scale (VAS) measured at 1, 3, and 6 months postoperatively and maximum incisal opening measured pre and post-surgery. The other variables were grouped into the following categories: surgery time, length of stay, and unilateral vs bilateral replacements. RESULTS: Our review showed no statistically significant difference in maximum incisal opening, subjective pain score, hospital stay, surgical time, or complication rate between Biomet-Lorenz stock and TMJ Concepts, Inc. custom total joint replacement. Bilateral TJR, irrespective of prosthesis type, did have greater improvement in maximal incisal opening (MIO) compared with unilateral that was statistically significant (P < .05). CONCLUSIONS: There was no statistically significant difference in the pain VAS or MIO using either stock or custom TJR. Both should be considered good surgical options for improvements in patient function and long-term jaw stability.