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.

A comparison of the marginal vertical discrepancies of zirconium and metal ceramic posterior fixed dental prostheses before and after cementation.

STATEMENT OF PROBLEM: Marginal discrepancies of zirconia posterior fixed dental prostheses (FDPs) fabricated using various systems have been assessed to determine the quality of the restorations and facilitate clinical use; however, studies are limited and results are ambiguous because of the sample sizes and measurement methods. PURPOSE: The purpose of this in vitro study was to compare changes in marginal fit of posterior fixed dental prostheses of 3 zirconia systems manufactured using CAD/CAM technology and metal ceramic posterior fixed dental protheses fabricated with the conventional lost-wax technique, before and after cementation. MATERIAL AND METHODS: Forty standardized master steel dies with 2 abutments simulating first mandibular premolars were fabricated to receive a posterior 3-unit FDP (from first molar to first premolar) and divided into 4 groups (n=10): Lava All-Ceramic System, Procera Bridge Zirconia, VITA In-Ceram 2000 YZ, and metal ceramic (control group). All FDPs were prepared for an internal space of 50 microm. The external marginal gap of the restorations was investigated by measuring 30 points in the middle of the buccal and lingual surfaces; therefore, 60 measurements per abutment were recorded. Measurements were made with an image analysis program on the master steel model before and after conventional cementation with a glass ionomer agent (Ketac Cem Easymix). The data obtained were statistically analyzed using 1-way ANOVA, Duncan's multiple range post hoc test, and Student's paired t test (alpha=.05). RESULTS: No significant differences in the vertical marginal fit before and after cementation were recorded for the analyzed groups. The marginal discrepancy of Procera abutments before and after cementation (9 +/-10 microm and 12 +/-9 microm, respectively) was less than that of the other groups. Significant differences (P=.001) were observed in marginal adaptation between Procera Bridge Zirconia and the other groups. CONCLUSIONS: The results of this study showed that cementation did not cause a significant increase in the vertical marginal discrepancies of the FDPs and that an internal space of 50 mum provided a high precision of fit of the restorations. The accuracy of fit achieved for the 3 zirconium oxide groups analyzed was within the range of clinical acceptance, and the discrepancies were lower than in the metal ceramic group. Procera Bridge Zirconia showed the lowest vertical discrepancies.

Influence of melting and casting methods and finish line design on the marginal discrepancy of nickel-chromium-titanium alloy crowns.

The aim of this study was to analyze the influence of melting and casting procedures and the cervical finish line design on the marginal fit of nickel-chromium-titanium alloy crowns. Sixty standardized specimens were prepared to receive metal-ceramic crowns and were divided into two groups according to the cervical finish line: chamfer or rounded shoulder. Three melting and casting procedures were analyzed: (1) induction-centrifuge (IC), (2) gas oxygen torch-centrifuge (TC), and (3) induction-vacuum/pressure (IP). The marginal fit was measured with an image analysis system. Significant differences (P =.005) were observed among the groups, with TC showing the lowest discrepancies (45.87 µm). No significant differences were observed between the two finish lines. The accuracy of fit achieved for the groups analyzed may be regarded as within the range of clinical acceptance.

Comparative analysis of two measurement methods for marginal fit in metal-ceramic and zirconia posterior FPDs.

The purpose of this study was to compare two measurement methods for the external marginal fit of zirconia posterior fixed partial dentures (FPDs) fabricated using computer-aided design/manufacturing technology and metal-ceramic posterior FPDs fabricated using the conventional lost-wax technique. The null hypothesis was that there would be no differences between the measurement methods. Forty standardized steel specimens were prepared to receive posterior three-unit FPDs. Specimens were divided into four groups (n = 10): (1) metal-ceramic, (2) Procera Bridge Zirconia, (3) Lava AllCeramic System, and (4) Vita In-Ceram YZ 2000. All FPDs were luted with glass-ionomer cement (Ketac Cem EasyMix, 3M ESPE). Two measurement methods were used to analyze marginal fit: an image analysis (IA) program and a scanning electron microscope (SEM) (JEOL JSM-6400) with magnifications of 340 and 31,000, respectively. Marginal fit was measured at the same point on each abutment. Significant interaction was observed between measurement method and material (P = .0019). Therefore, the measurement method is not independent of the restoration material. Differences among groups were observed for IA (P = .0001) and SEM (P = .0013). Significant differences were observed for the Procera (P = .0050) and metal-ceramic (P = .0039) specimen groups when both measurement methods were evaluated separately. Accuracy of fit achieved by the four groups analyzed was within the range of clinical acceptance, yielding Procera Bridge Zirconia to have the best marginal fit using both measurement methods.

Marginal fit of Zirconia posterior fixed partial dentures.

The aim of this study was to investigate the marginal fit of posterior fixed partial dentures (FPDs) made with 2 computer-aided design/computer-assisted manufacture systems--Procera Bridge Zirconia (Nobel Biocare) and Lava AllCeramic System (3M ESPE)--and to analyze the differences between abutments and between buccal and lingual surfaces. Twenty standardized specimens were prepared to receive posterior 3-unit FPDs. FPDs were fabricated according to the manufacturer's instructions. A scanning microscope (JSM-6400, JEOL) with a magnification of 1,000x was used for measurements. Three-way analysis of variance showed significant differences (P < .001) in marginal adaptation between the ceramic groups. Procera Bridge Zirconia showed the lowest discrepancies (26 +/- 19 microm). No significant differences were observed between abutments and surfaces, and no significant interaction was observed among the ceramic system, abutments, and surfaces. The accuracy of fit achieved by both zirconia systems was within the range of clinical acceptability, with Procera Bridge Zirconia showing the best marginal fit.

Marginal fit of titanium metal-ceramic crowns.

PURPOSE: This study aimed to compare the marginal fit of 2 kinds of metal-ceramic crowns-crowns cast from commercially pure titanium and Procera titanium crowns. MATERIALS AND METHODS: Ten copings of each type were prepared, veneered with low-fusing porcelain, and bonded with glass-ionomer cement. Marginal fit was assessed before and after cementation, and the data were analyzed statistically. RESULTS: There were significant differences among mean values of marginal fit between the groups. Cementation increases discrepancies in both groups. CONCLUSION: Casting titanium has resulted in the highest discrepancies in marginal fit of both groups.

Comparison of the marginal fit of Procera AllCeram crowns with two finish lines.

PURPOSE: The purpose of this study was to determine the influence of two finish line configurations on the marginal accuracy of Procera AllCeram crowns. MATERIALS AND METHODS: Twenty mechanized specimens of brass were fabricated for complete-coverage crowns. Two finish line designs were used: chamfer and rounded shoulder. AllCeram crowns were fabricated, and the fit of the crowns to the dies was recorded from the buccal and lingual margins. An image-analysis program was used to measure the gap. The results were subjected to statistical analysis using a Student's t test for separate samples and Student's paired t test. RESULTS: No significant differences were observed between the buccal and lingual measurements. When the values of the buccal and lingual measurements were averaged, there were no significant differences in the marginal gap, horizontal discrepancy, or internal adaptation of the axial wall, but there were significant differences in the vertical discrepancy, absolute marginal discrepancy, and internal discrepancy between the two finish line designs. CONCLUSION: The marginal gap was within the range of clinical acceptability. Some of the variables were influenced by the two finish lines tested.

Three-year clinical evaluation of In-Ceram Zirconia posterior FPDs.

PURPOSE: The purpose of this study was to evaluate the clinical performance of In-Ceram Zirconia posterior fixed partial dentures (FPD) after 3 years in service. MATERIALS AND METHODS: Eighteen In-Ceram Zirconia FPDs were fabricated in 16 patients. The FPDs were placed between January and April 1999. The CDA quality evaluation system was used for assessment of surface and color, anatomic form, and marginal integrity. Bleeding on probing was also recorded. RESULTS: One of the 18 posterior FPDs was lost because of a root fracture. All remaining FPDs were rated as either excellent or acceptable after the observation period. Bleeding was more often recorded at crowned abutments with In-Ceram Zirconia than at contralateral teeth. CONCLUSION: In-Ceram Zirconia posterior FPDs seem to be an acceptable treatment alternative in a 3-year perspective. However, more clinical long-term follow-up studies must be performed before the system can be recommended as an alternative to conventional FPDs.