Jesús Peláez

A prospective evaluation of zirconia posterior fixed dental prostheses: Three-year clinical results

STATEMENT OF PROBLEM Although the favorable mechanical properties of zirconium oxide-based ceramics have increased the acceptance of fixed dental prostheses for use in the posterior regions of the mouth in recent years, there are few clinical studies documenting the longevity of these restorations. Furthermore, certain complications must be resolved before the material is used more extensively. PURPOSE The purpose of this randomized prospective study was to evaluate the clinical performance of zirconia (Lava) 3-unit posterior fixed dental prostheses. MATERIAL AND METHODS Twenty 3-unit fixed dental prostheses were placed in 17 participants to replace a second premolar or a first molar. Eleven were placed in the maxilla and 9 in the mandible. All abutment teeth were prepared with a chamfer finish line of 0.8 to 1 mm, and frameworks were prepared with the Lava system. Restorations were cemented with a resin cement. Two calibrated examiners independently evaluated the fixed dental prostheses 1 week (baseline) and 1, 2, and 3 years after placement with the California Dental Association quality evaluation system. The periodontal parameters: the gingival index, plaque index, margin index, and the probing depths of abutment teeth and contralateral teeth were assessed. Data were analyzed by using descriptive statistics and the Wilcoxon signed-rank test (α=.05). RESULTS All fixed dental prostheses were rated satisfactory after 3 years, and no fracture of the framework was observed during the observation period. One fixed dental prostheses was lost because of a biological complication at the 3-year examination, and a small degree of chipping of the veneering ceramic was observed in 2 participants. No significant differences among the periodontal parameters of the test and control teeth were observed except for the margin index. CONCLUSIONS The results of a 3-year evaluation suggest that posterior zirconia 3-unit fixed dental prostheses are a reliable treatment.

Marginal Vertical Discrepancies of Monolithic and Veneered Zirconia and Metal-Ceramic Three-Unit Posterior Fixed Dental Prostheses.

PURPOSE The aim of this study was to investigate and compare the marginal fit of posterior fixed dental prostheses (FDPs) made of monolithic and veneered computer-aided design/computer-assisted manufacture (CAD/CAM) zirconia ceramic with metal-ceramic posterior FDPs. MATERIALS AND METHODS Thirty standardized steel dies were prepared to receive posterior three-unit FDPs. Specimens were randomly divided into three groups (n = 10): (1) metal-ceramic (control group), (2) veneered zirconia, and (3) monolithic zirconia. All FDPs were cemented using a glass-ionomer cement. The specimens were subjected to thermal cycling (5°C to 55°C). A scanning electron microscope (SEM) with a magnification of ×500 was used for measurements. The data were statistically analyzed using one-way analysis of variance and paired t test. RESULTS Both zirconia groups showed similar vertical marginal discrepancies, and no significant differences (P = .661) in marginal adaptation were observed among the groups. No differences were observed in either group in marginal discrepancies between surfaces or abutments. CONCLUSION Monolithic zirconia posterior FDPs exhibit similar vertical marginal discrepancies to veneered zirconia posterior FDPs. No influence of localization measurements was observed.

Fracture Load Before and After Veneering Zirconia Posterior Fixed Dental Prostheses.

PURPOSE To evaluate the fracture load of 3-unit zirconia-based posterior fixed dental prostheses (FDPs) before and after veneering the frameworks. MATERIALS AND METHODS Forty standardized stainless-steel master dies were fabricated (height: 5 mm, convergence: 6º, chamfer: 1 mm) and randomly screwed in pairs onto metal bases. The bases were randomly divided into two groups (n = 20 each) according to the zirconia CAD/CAM system used for constructing 3-unit structures for FDPs: group 1 (L): Lava All-ceramic, group 2 (Z): IPS e.max ZirCAD. Half of the zirconia structures per group were randomly selected and veneered, while the remaining half was left unveneered. The specimens were luted in standard fashion onto the stainless steel master dies using conventional glass ionomer cement. All specimens were tested for fracture load (FL). Specimens were subjected to a three-point bending test until fracture by applying an axial compressive load at the central fossa of the pontics with a universal testing machine at a 0.5 mm/min crosshead speed. Wilcoxons rank-sum test and Weibull statistics were used for statistical analysis (α = 0.05). RESULTS L structures recorded significantly higher values of load to fracture than the Z group both before and after veneering. Within each ceramic group, no differences were found between unveneered and veneered frameworks. CONCLUSIONS Although further studies are necessary to corroborate these findings, both zirconia systems could be recommended for restoring posterior teeth on the basis of the fracture load values recorded in this experiment (>1000 N). The veneering procedure did not affect the overall load to fracture in any group.

Comparative fracture behavior of monolithic and veneered zirconia posterior fixed dental prostheses

The purpose of this study was to evaluate and to compare the fracture load and the fracture pattern of monolithic and veneered zirconia posterior fixed dental prostheses (FDPs). Twenty standardized steel dies were prepared to receive posterior 3-unit FDPs. Specimens were randomly divided into 2 groups (n=10): (1) Lava Zirconia, and (2) Lava Plus. All FDPs were cemented using glass ionomer cement and subjected to thermal and mechanical cycling at 5-55ºC with a 30-s dwell time for 120,000 masticatory cycles. All specimens were subjected to a three-point bending test until fracture. Data were statistically analyzed using Students t test, paired t-test and Weibull statistics (α=0.05). No differences were observed in fracture load between the groups. Veneering ceramic fractured before than framework in veneered zirconia group. The fracture pattern was different. The tested groups demonstrated clinically acceptable fracture load values. Monolithic zirconia solves the chipping problem.

Fracture resistance and failure mode of posterior fixed dental prostheses fabricated with two zirconia CAD/CAM systems.

Background In recent years there has been an improvement of zirconia ceramic materials to replace posterior missing teeth. To date little in vitro studies has been carried out on the fracture resistance of zirconia veneered posterior fixed dental prostheses. This study investigated the fracture resistance and the failure mode of 3-unit zirconia-based posterior fixed dental prostheses fabricated with two CAD/CAM systems. Material and Methods Twenty posterior fixed dental prostheses were studied. Samples were randomly divided into two groups (n=10 each) according to the zirconia ceramic analyzed: Lava and Procera. Specimens were loaded until fracture under static load. Data were analyzed using Wilcoxon´s rank sum test and Wilcoxon´s signed-rank test (P<0.05). Results Partial fracture of the veneering porcelain occurred in 100% of the samples. Within each group, significant differences were shown between the veneering and the framework fracture resistance (P=0.002). The failure occurred in the connector cervical area in 80% of the cases. Conclusions All fracture load values of the zirconia frameworks could be considered clinically acceptable. The connector area is the weak point of the restorations. Key words:Fixed dental prostheses, zirconium-dioxide, zirconia, fracture resistance, failure mode.

A Randomized Clinical Trial Comparing Zirconia and Metal-Ceramic Three-Unit Posterior Fixed Partial Dentures: A 5-Year Follow-Up: Survival of Zirconia Posterior FPDs

PURPOSE To compare the survival, success rates, and biological/technical complications of posterior metal-ceramic (MC) and zirconia fixed partial dentures (FPDs). MATERIALS AND METHODS A total of 40 patients requiring 40 posterior FPDs were randomly assigned to receive 20 zirconia and 20 MC restorations. The restorations were examined 1 week (baseline) and 1, 3, and 5 years after the end of treatment. Technical and biological outcomes were compared. Data were statistically analyzed using the Wilcoxon signed-rank and Mann-Whitney U tests. RESULTS The survival rates of both groups were 100%, and the success rates were 80% (zirconia) and 100% (MC). No biological complications were observed. Minor chipping was found in 20% of the zirconia restorations. No differences in periodontal parameters were observed between groups. CONCLUSIONS Zirconia FPDs exhibited the same survival rate (100%) as MC FPDs after 5 years; however, the success rate was 80%, because an increased rate of chipping was observed in zirconia restorations.