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

Abstract

PurposeTo investigate the design and location of supporting structures on the marginal and internal gap of interim restorations.Materials and methodsA 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).ResultsThere 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).ConclusionThe 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.

Fracture resistance, marginal and internal adaptation of innovative 3D‐printed graded structure crown using a 3D jet printing technology

“…65 Alharbi et al compared the marginal and internal gaps of milled and 3D-printed interim crowns and reported smaller gaps for 3D-printed interim restorations than milled crowns 66 ; however, other studies had conflicting outcomes. 53,67 The outcome of the current study showed that the marginal gaps of the ML and BL groups were within an acceptable range for definitive crowns 50,64 and comparable with previous studies; 53,[66][67][68] the solid group showed a high marginal gap of 318 mm. In addition, the mean internal gap of SC in the current study was significantly (p < 0.05) higher than that of the crowns with graded structures.…”

“…The sample size was selected based on similar previous studies [51][52][53] to achieve a power of 99%. A complete coverage restoration with a uniform thickness of 1.5 mm was designed on a mandibular first molar die with 50 mm die spacer, 0.5 mm from the margin.…”

“…Each replica was assessed at 25 points for the marginal gap and 25 points for the internal gap (axial and occlusal); the average of readings was reported as the marginal and internal gaps for each crown. 53 All measurements were made by one operator. Crowns were then luted to their assigned resin dies using a temporary luting agent (TempBond NE; Kerr Dental) under a constant pressure of 450 g and set for 24 h at room temperature.…”

Maximum Fracture Load of Interim Crowns Fabricated by Additive and Subtractive Techniques

“…[17][18][19][20][21] Additionally, interim crowns manufactured through the DLS technique have demonstrated smaller marginal gaps compared to those produced via DLP and SM. 22 The fracture strength of interim prostheses holds paramount importance in ensuring their long-term functionality. Numerous studies have assessed the fracture load of interim crowns produced through both SM and AM.…”