Marginal gap and internal fit of 3D printed versus milled monolithic zirconia crowns

Abstract

Background This study aimed to evaluate and compare the marginal gap using two different methods and the internal fit of 3D printed and zirconia crowns. Methods 3Y-TZP zirconia crowns (n = 20) were manufactured using subtractive milling (group M) and 3D printed (group P). The marginal gap was measured at 60 points using vertical marginal gap technique (VMGT). On the other hand, the silicone replica technique (SRT) was used to evaluate the internal fit and was divided into 4 groups: marginal gap, cervical gap, axial gap, and occlusal gap where the thickness of light impression was measured at 16 references. The numerical data was tested for normality using Shapiro–Wilk's test. They were found to be normally distributed and were analyzed using an independent t-test. Results Using VMGT, group P had significantly higher mean marginal gap values of 80 ± 30 µm compared to group M = 60 ± 20 µm (p < 0.001). Also, with the SRT, the marginal gap of group P (100 ± 10 µm) had significantly higher values compared to group M (60 ± 10 µm). The internal fit showed significant difference between the tested groups except for Axial Gap. Conclusions Although milled crowns showed better results. The 3D printed zirconia crowns offer clinically acceptable results in terms of marginal adaptation and internal fit. Both VMGT and SRT are reliable methods for the assessment of the marginal gap.

Feasibility of images acquired using smartphone camera for marginal and internal fit of fixed dental prosthesis: comparison and correlation study

“…Various methods are used to evaluate the marginal and internal fit, such as the silicone replica technique 6 , superimposition after 3D scan 8 , 9 , weight technique 10 , microcomputed tomography 11 , 12 , optical coherence tomography 4 , 13 , and cutting and measurement after cementation of the prosthesis 14 , 15 . The silicone replica technique has been used in several studies as a gold standard for marginal and internal fit evaluation owing to its simplicity and excellent accuracy in a nondestructive method 16 – 18 . This technique involves the injection of silicone into the intaglio surface of the prosthesis and evaluation of the marginal and internal fit.…”