Retrospective 1- to 8-Year Follow-Up Study of Complete Oral Rehabilitation Using Monolithic Zirconia Restorations with Increased Vertical Dimension of Occlusion in Patients with Bruxism

Edge Chipping Resistance and Flexural Strength of CAD-CAM Ceramics Before and After Thermomechanical Aging

OBJECTIVES

To evaluate the complementary mechanical properties of dental ceramics using edge chipping resistance (Rea) and flexural strength before and after thermomechanical aging.

MATERIAL AND METHODS

Computer-aided design and computer-aided manufacturing of ceramic materials, including zirconia (ZR), lithium disilicate (LS2), and resin nanoceramics (RNC), were evaluated. Specimens for flexural strength testing were fabricated with dimensions of 3 × 4 × 25 mm, with 30 specimens per group. For the edge chipping test (ECT), specimens were fabricated with dimensions of 3 × 4 × 12 mm, with 48 specimens per group. Half of the specimens for both tests were subjected to thermomechanical aging for 200,000 cycles at 50 N. A Weibull analysis was performed to determine flexural strength. Fractographic analysis was performed before and after thermomechanical aging during the ECT. X-ray diffractometry (XRD) was performed on the ZR specimens before and after thermomechanical aging. Flexural strength was analyzed using a two-way repeated analysis of variance (ANOVA) with a t-test, and Rea was analyzed using Pearson correlation and a two-way repeated ANOVA.

RESULTS

The flexural strength and Rea differed according to the material (p = 0.001), whereas they were similar before and after thermomechanical aging (p > 0.05). The Weibull modulus of the flexural strength decreased after thermomechanical aging. In the fractographic analysis of the ECT, more than two fracture origins were identified after thermomechanical aging. The XRD analysis of ZR showed an increased monoclinic phase after thermomechanical aging.

CONCLUSION

All the materials met the ISO 6872 standards for bending test. However, LS2 and RNC show low edge chipping resistance within the range of the occlusal force. The thermomechanical aging did not significantly alter the mechanical properties of the materials. However, the Weibull coefficients of the flexural strength decreased, and an additional origin of fracture appeared after thermomechanical aging.

SIGNIFICANCE

Flexural strength and Rea differed depending on the material used. The probability of the material fracture increased after thermomechanical aging. To understand ceramic fractures, two mechanical tests and thermomechanical aging must be performed together.

A Retrospective Evaluation of 5 Years of Clinical Results of Metal-Ceramic vs. Monolithic Zirconia Superstructures in Maxillary All-on-4TM Concept

The aim of the current study was to present the clinical and radiological outcomes of monolithic zirconia superstructures compared to the metal-ceramic ones in the All-on-4 concept for the prosthetic rehabilitation of the maxillae. A total of 30 patients were subdivided into groups according to their superstructure type (metal-ceramic (n = 15) or monolithic zirconia (n = 15)). All implants were functionally loaded within 24 h after insertion with provisional acrylic superstructures. Prosthetic complications, marginal bone loss, plaque accumulation, probing pocket depth, bleeding on probing, and bite force were documented over a period of 5 years. Marginal bone loss around the implants of the ceramic group remained well over the five years (1.21 ± 0.23 mm). However, marginal bone loss was significantly lower around the implants in the monolithic zirconia group (0.22 ± 0.14 mm) (p < 0.001). Bleeding on probing, plaque accumulation, and probing pocket depth values were correlated with marginal bone loss. Among all evaluated parameters, no differences could be detected in terms of the angulation of the implants. Detachment or chipping was observed in seven cases in the metal-ceramic superstructure group. In all cases, dentures were removed and repaired in the laboratory. In the monolithic zirconia group, chipping was detected after one year in two cases, after two years in four cases, and after five years in one case and could be managed by polishing in situ. Monolithic zirconia superstructures presented superior results regarding the parameters evaluated.

Outcomes and Complications of 33 Soft-Milled Cobalt-Chromium-Ceramic Full-Arch Screw-Retained Implant-Supported Prostheses: A Retrospective Study with up to 10-Year Follow-up

This retrospective study assessed outcomes and complications related to implants and prostheses in edentulous patients treated with soft-milled cobalt-chromium-ceramic full-arch screw-retained implant-supported prostheses (SCCSIPs). After the final prosthesis was delivered, patients participated in an annual dental check-up program, including clinical and radiographic assessments. Outcomes of implants and prostheses were evaluated, and biological and technical complications were categorized as major or minor. Implant and prosthesis cumulative survival rates were assessed using the life table analysis. A total of twenty-five participants (mean age 63.6 ± 7.3 years) with 33 SCCSIPs were observed for a mean of 68.9 ± 27.9 months (range 1–10 years). A total of 7 out of 245 implants were lost, with no effect on prosthesis survival, leading to cumulative survival rates of 97.1% for implants and 100% for prostheses. The most recurrent minor and major biological complications were soft tissue recession (9%) and late implant failure (2.8%). Among 25 technical complications, porcelain fracture was the only major technical complication, requiring prosthesis removal (1%). Porcelain chipping was the most frequent minor technical complication, affecting 21 crowns (5.4%), which required polishing only. At the end of the follow-up, 69.7% of the prostheses were free of technical complications. Within the limitations of this study, SCCSIP showed promising clinical performance after 1–10 years.