Performance of posterior third-generation monolithic zirconia crowns in a complete digital workflow: A three-year prospective clinical study.

Background/purpose: Translucent monolithic zirconia restorations have recently introduced. The purpose of this study was to evaluate the clinical behavior and the survival rate of the posterior third-generation monolithic zirconia crowns (MZCs) during three years of clinical service. Materials and methods: Twenty-four patients who needed thirty crowns were enrolled in this study. Digital impressions were made, and the crowns were milled and cemented with a resin cement. The crowns outcomes were assessed using the California Dental Association's (CDA) criteria. Gingival index (GI), plaque index (PI), and periodontal probing depth (PPD) for MZCs and contralateral natural teeth (control) were assessed. Margin index (MI) for MZCs was also assessed. Data analysis was conducted using the Wilcoxon signed-rank and the Friedman tests. Results: The 3-year survival rate was 100%. All MZCs were rated as satisfactory throughout the follow-up period, and no biological or mechanical complications were observed. No differences were recorded when GI, PI and PPD at 3-year of follow-up were compared to baseline. No differences were recorded between crowned and control teeth. The MI remained stable throughout the study period. Conclusion: The third-generation monolithic zirconia appears to be a good treatment option for the rehabilitation of posterior single teeth.

Immediate Loading of Zygomatic Implants Using a Dual Scan Technique.

The immediate loading protocol has become increasingly popular due to the progressive growth in demand for a reduction in treatment times. The possibility of applying this protocol would depend on certain important factors. The application of the digital workflow mentioned in the protocol guarantees rapidity, precision, and esthetics. This report aims to describe a fully digital workflow using a dual scan impression technique to fabricate immediate fixed complete dentures (FCDs) for zygomatic and standard implants. A 58-year-old female patient requested treatment for her severely atrophic maxilla, and four unrehabilitated implants in the mandible. After proper diagnosis and planification, four zygomatic implants and two standard implants were placed. During the surgery, transmucosal abutments were placed on all implants. After suturing, the positions of the implants were recorded using a stereophotogrammetric technique, creating a standard tessellation (STL) file. In the lower arch, the second phase of the surgery was carried out: the transmucosal abutments were placed, and then the implant positions were recorded in the same way. The soft tissues were rescanned after suturing with an intraoral scanner (IOS), and all STL files were aligned to obtain the virtual final models. The pre-design after virtual modifications was aligned with the definitive models. The provisional prostheses were milled and placed after six hours after the surgery, and the definitive prostheses were placed six months after the surgery. The dual scan technique used obtained a precise fit for both the provisional and definitive FCDs. This technique might be an effective and reliable alternative for the fabrication of immediate and definitive screw-retained FCDs in a completely digital workflow. The time taken for scanning and fabrication was reduced, and the clinician's and patient's satisfaction were improved.

Effect of Surface Treatments with Low-Pressure Plasma on the Adhesion of Zirconia.

The purpose of this study was to investigate the effect of low-pressure plasma on the contact angle, shear bond strength (SBS), and the failure mode of zirconia ceramic. Zirconia specimens were divided into three groups according to the surface treatment methods as follows: sandblasting with aluminum oxide (ZR-C), sandblasting with aluminum oxide and oxygen plasma (ZR-CP), and argon plasma (ZR-P). The contact angle, SBS, and surface characteristics were tested after thermocycling. Data analysis was made using the Kruskal-Wallis test and one-way analysis of variance. Plasma treatment significantly reduced the contact angle (p < 0.001) with the lowest value for the Zr-P group. An increase in oxygen and a decrease in carbon was observed on the zirconia surface in both plasma groups. For the SBS, there were significant differences among the groups (p < 0.018), the Zr-CP group showing the highest bond strength. Mixed failures were the most frequent. Plasma treatment was effective in increasing the wettability, increasing the oxygen/carbon ratio without changing zirconia surface morphology. The sandblasting plus plasma with oxygen group exhibited the highest bond strength.

Prospective Clinical Evaluation of Posterior Third-Generation Monolithic Zirconia Crowns Fabricated with Complete Digital Workflow: Two-Year Follow-Up.

Clinical studies on the behavior of posterior translucent monolithic zirconia restorations are lacking. We assessed the clinical outcome and survival rate of posterior third-generation monolithic zirconia crowns over a 2-year period. A total of 24 patients, requiring 30 posterior full-contour restorations were selected. All abutments were scanned, and crowns were milled and cemented with a self-adhesive dual cure cement. Crowns were assessed using the California Dental Association's criteria. Gingival status was assessed by evaluating the gingival index, plaque index, periodontal probing depth of the abutments and control teeth, and the margin index of the abutment teeth. Statistical analyses were performed using the Friedman and the Wilcoxon signed-rank tests. During the 2-year follow-up, no biological or mechanical complications were observed, and the survival and success rate was 100%. All restorations ranked as satisfactory throughout the follow-up period. The gingival index and plaque index were worse at the end of the 2-year follow-up. The margin index was stable during the 2 years of clinical service. No significant differences were recorded in periodontal parameters between crowns and control teeth. Third-generation monolithic zirconia could be a reliable alternative to posterior metal-ceramic and second-generation monolithic zirconia posterior crowns.