Jordan University of Science and Technology

Comparison of the accuracy of fit of metal, zirconia, and lithium disilicate crowns made from different manufacturing techniques

Khaled Q Al Hamad, Firas A Al Quran, Sendos A AlJalam, Nadim Z Baba

Purpose: To evaluate the accuracy of fit of metal, lithium disilicate, and zirconia crowns, which were produced using different manufacturing techniques. Materials and methods: Ten patients in need of a molar crown were recruited. Eight crowns were fabricated for each patient: 2 zirconia, 3 lithium disilicate (e.max), and 3 metal-ceramic crowns using conventional, conventional/digital, and digital techniques. Marginal, axial, and occlusal gaps were measured using a replica technique. Replicas were sectioned mesiodistally and buccolingually and were observed under a stereomicroscope. A total of 32 measurements for each crown replica at 3 different points (12 marginal, 12 axial, and 8 occlusal) were performed. Statistical analysis was performed using two-way ANOVA and Tukey HSD tests. Results: Marginal means ranged from 116.39 ? 32.76 ?m for the conventional metal-ceramic group to 147.56 ? 31.56 ?m for the digital e.max group. The smallest axial gap was recorded for the digital zirconia group (76.19 ? 23.94 ?m), while the largest axial gap was recorded for the conventional e.max (101.80 ? 19.81 ?m) and conventional/digital metal-ceramic groups (101.80 ? 35.31 ?m). The conventional e.max crowns had the smallest occlusal mean gap (185.59 ? 59.09 ?m), while the digital e.max group had the largest occlusal mean gap (295.38 ? 67.80 ?m). Type of crown had no significant effect on marginal (p = 0.07, f = 2.71), axial (p = 0.75, f = 0.29), or occlusal fit (p = 0.099, f = 2.4), while fabrication method had a significant effect on axial gap only (p = 0.169, f = 1.82, p = 0.003, f = 6.21, and p = 0.144, f = 2 for marginal, axial, and occlusal fit, respectively). Digital fabrication produced significantly smaller axial gaps than the conventional method (p = 0.02), and the conventional digital method (p = 0.005). Conclusions: The type of crown and method of manufacturing had no effect on the marginal and occlusal gap of single posterior crown, while the method of manufact