Fabrication outcomes and clinical performance of CAD‐CAM monolithic translucent zirconia implant crowns in the molar region‐ a randomized controlled clinical study

Abstract

Background The data on all-ceramic implant reconstructions showed a high rate of veneering fractures. The monolithic design may reduce the technical complication rate. To date, the evidence on the CAD-CAM fabrication outcomes and the clinical performance is limited to glass-ceramic implant crowns. Recently, translucent zirconia was introduced exhibiting good mechanical properties and biocompatibility. Therefore, monolithic translucent zirconia implant crowns may be a valuable option in the posterior region Aim/Hypothesis The aim of the present clinical trial was to test whether or not translucent monolithic zirconia implant crowns fabricated by means of CAD-CAM technology render similar fabrication outcomes and perform similar to porcelain-fused-to-metal implant crowns in the posterior region. Material and Methods The present study was designed as a randomized controlled clinical trial. Eighty healthy patients in need of a single implant crown in the molar region were enrolled and a narrow-diameter implant (Straumann Roxolid, Tissue Level, Standard Plus, diameter of 3.3 mm) was placed. After tissue healing, implants were restored with screw-retained crowns. Following random allocation, either a monolithic zirconia crown bonded onto a titanium base (Straumann, Variobase) or a porcelain-fused-to-metal crown (control) was inserted. Modified USPHS criteria, crown and implant survival rates, change in marginal bone level (MBL), and clinical measurements (PD, PCR, BOP, KM) were assessed after crown insertion and at the 1-year follow-up visit. Data were analyzed descriptively. For continuous outcomes, student's unpaired t-test and the Mann-Whitney rank test were applied. For ordinal outcomes, the paired Wilcoxon test was applied. The level of statistical significance was set at P < 0.05. Results At baseline, eighty patients (36 females and 44 males) with 41 test crowns (mean age 56.8 y) and 39 control crowns (mean age 54.9 y) were evaluated. Anatomical contour and color match as compared to the neighboring dentition were rated ideal in 13 and 14 patients of the test group and in 20 and 37 patients of the control group, respectively. These differences between test and control group were statistically significant. Patient satisfaction was high in both groups after crown delivery and after one year. At the 1-year follow-up, one crown in each group was lost due to loss of the implant (test, loss of osseointegration; control, implant fracture). Minor chippings occurred in the control group only (3 40). Interproximal and occlusal contacts were lost in 4 and 11 patients of the test and control groups, respectively. There were no significant differences between the groups with respect to the change in MBL and to the clinical parameters. Conclusion and clinical implications Monolithic translucent zirconia crowns bonded to titanium base abutments are a valuable option to PFM crowns for single implants in the posterior area. The anatomical contour and the color match of the test crowns were inferior to the PFM crowns. Nevertheless, patient satisfaction was high. The outcomes may be attributed to the CAD-CAM devices used. The results of this study raise the question, whether titanium-zirconia narrow-diameter implants can be recommended to support molar crowns.