Five-year clinical prospective evaluation of zirconia-based Denzir 3-unit FPDs.

PURPOSE: The aim of this prospective study was to evaluate the clinical performance of fully sintered hot isostatic pressed yttria-partially-stabilized zirconia (Denzir) 3-unit fixed partial dentures (FPDs). MATERIALS AND METHODS: Nineteen 3-unit FPDs were placed in 18 patients. Ten FPDs were placed in the maxilla and 9 in the mandible. Two calibrated examiners evaluated the FPDs independently 1 week (baseline), 1 year, 3 years, and 5 years after placement using the California Dental Association quality evaluation system. RESULTS: All FPDs were intact at the 5-year examination. One FPD lost retention after 12 months but remained intact; it was recemented and is still in function after 5 years. All FPDs were rated satisfactory over 5 years. No changes were seen in terms of color and anatomic form. The number of slightly rough or pitted occlusal surfaces increased approximately 30% over 5 years. Visible evidence of ditching along the margin increased over time, but only for those FPDs luted with zinc phosphate cement. CONCLUSION: The 5-year results indicate that yttria-partially-stabilized zirconia 3-unit FPDs with anatomically designed frameworks are promising prosthetic alternatives, even in the premolar and molar regions. However, for all-ceramic FPDs with more units in function, further studies are necessary.

Clinical evaluation of all-ceramic onlays: a 4-year retrospective study.

PURPOSE: The aim of the present study was to evaluate the clinical outcome of extensive Empress onlays retained with resin-bonded cement. MATERIALS AND METHODS: One hundred thirty extensive ceramic onlays were placed in premolar and molar regions in 91 patients treated by 2 general practitioners between 1997 and 2000. Seventy-seven percent of the constructions were luted with chemically cured resin composite cement and 23% were luted with dual-cured resin cement. Fifty-nine patients with 81 restorations were clinically evaluated independently by 2 calibrated examiners using the California Dental Association protocol. The mean time in function for all restorations at examination was 49 months. RESULTS: Seventy-five (93%) onlays were still in function after 4 years. Six onlays (7.3%) failed; 1 had lost retention as a result of caries, and 5 had fractured. All failures were in molar regions. CONCLUSIONS: Ceramic onlay therapy is an acceptable treatment alternative over a 4-year period, but further long-term data are necessary before this treatment should be considered for general dental practice.

Levels of gold in plasma after dental gold inlay insertion.

OBJECTIVE: Several studies have reported increased levels of gold (Au) in the blood of patients with dental gold restorations. This study analyzed gold levels in blood plasma before dental gold inlay insertion, 0-12 months after, and 15 years after. MATERIAL AND METHODS: Plasma samples from 9 patients were taken before and 0-10 months after gold inlay insertion. Fifteen years after gold inlay insertion, further blood samples taken from 8 of these patients were analyzed for gold using inductively coupled plasma mass spectrometry. An oral examination was also carried out before and 15 years after gold inlay insertion. RESULTS: Gold levels in plasma were significantly higher 0-12 months after gold inlay insertion than before treatment (p=0.008). No significant difference in gold plasma levels was found between 0-12 months after and 15 years after insertion (p=0.109), although there was a significant correlation between the number of gold alloy surfaces and the amount of gold in plasma 15 years after insertion (p=0.028). CONCLUSIONS: This study supports a dose-related release of gold into plasma from dental gold restorations, a release that appears to be stable over time.

Three-dimensional finite element analyses of all-ceramic posterior fixed partial dentures with different designs.

The aim was to evaluate the influence on the stress distribution patterns in and the magnitude of stresses on fixed partial dentures (FPDs) under different anatomic and design conditions. Three-dimensional finite element models of posterior 3-unit all-ceramic FPDs were created with and without periodontal ligaments, with different radii of curvature at the embrasure area, and in a curve shape with a periodontal ligament. The model with a periodontal ligament showed 40% higher stress values compared to the no-ligament model. A smaller radius of curvature resulted in 20% to 40% higher stress values. The curved model increased stress values at the distal connector by 65% compared to the straight model. Support by teeth, occlusal curvature, and a small radius of curvature at the embrasure area negatively affect stress distribution patterns in the connector area of all-ceramic FPDs.

Bond strength of a composite luting agent to alumina ceramic surfaces.

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength (SBS) of a dental luting agent to alumina ceramics after different surface pretreatment. MATERIAL AND METHODS: Specimens (n=50) of pressed blocks (10 x 0 x 5 mm) of alumina ceramic (Procera AllCeram) were divided into untreated specimens (AF) as provided by the manufacturer and polished specimens (AP). Five groups of specimens (n=5 x 10) with different surface pretreatments were prepared. Groups 1 and 2: AF and AP without any pretreatment; Group 3: AF treated with silane, (AF-s); Group 4: AF treated with RF plasma spray (AF-RF); Group 5: AF treated with low fusing porcelain (AF-p) glass pearls. Composite cylinders (5 x 5 mm) were cemented to the test specimens with a resin luting agent. The specimens were loaded to failure in shear mode using a universal testing machine. Recorded loads were used to calculate SBS in MPa. The results were analyzed using one-way ANOVA and the Tukey HSD multiple comparison test at alpha = 0.05. Scanning electron microscopic micrographs (SEM) were used to characterize surfaces of interest. RESULTS: Polished surfaces had significantly lower SBS (p < 0.05) compared with untreated specimens (AP vs AF). Silanated, non-polished surfaces (AF-s) revealed lower SBS, even though the result was not significantly different from that of AF-s without silane treatment. Plasma treatment improved SBS by a factor of 2 (p<0.05) and treatment with low-fusing porcelain micro pearls increased SBS by a factor of 3 compared to untreated surfaces (p<0.05). The layer of glass pearls did not exceed 5 microm (SEM). CONCLUSIONS: Within the limitation of the conditions of this study, treatment of alumina oxide ceramic surfaces with a plasma spray coating or a low-fusing porcelain pearl layer significantly increased the SBS of a resin luting agent to the ceramic surface.

Bond strength of composite luting cement to zirconia ceramic surfaces.

OBJECTIVES: To evaluate the bond strength of dental resin agent to zirconia ceramic after surface pre-treatment with different techniques. METHODS: Specimens of hot isostatic pressed yttrium-oxide-partially-stabilized zirconia blocks (ZF) were fabricated (Procera Zircon, Nobel Biocare, Sweden) and compared to glossy dense zirconia blocks (ZG). Four groups of specimens with different surface treatment were prepared. Group I: ZF (n = 5) and ZG (n = 5) without any pre-treatment, Group II: ZF-s (n = 5) and ZG-s (n = 5) treated with silane solution, Group III: ZF-P (n = 10) and ZG-P (n = 10) treated with RF plasma spraying (hexamethyldisiloxane) using a reactor (Plasma Electronic, Germany), Group IV: ZF-p (n = 10) and ZG-p (n = 10) treated with micro pearls of low fusing porcelain (720 degrees C) on the surfaces. Composite cylinders (Charisma, Hereus Kulzer, Dormagen, Germany) were luted with Variolink II (Ivoclar-Vivadent, Schaan, Liechtenstein) to the test specimens. The specimens were then stored in air for 1 h before shear loading in a universal testing machine (LRX, Lloyd Instruments, Farnham, England) until failure. RESULTS: No statistical difference was found between the untreated ZF and ZG specimens (Group I) neither between the specimens treated with silane (Group II). Plasma spraying treatment improved bond strength by a factor of three (p < 0.001). Treatment with low fusing porcelain micro pearls increased the bond strength by a factor of 10 compared to untreated surfaces (p < 0.001). No significant difference was seen between the surfaces treated ZF-p and ZG-p specimens. The thickness of the glass pearls layer did not exceed 5 microm. SEM showed dense grain borders of ZF and a flat glossy texture of ZG. SIGNIFICANCE: Treatment of zirconia ceramic surfaces with plasma spraying or a low fusing porcelain pearl layer significantly increased the bond strength of resin cement to the ceramic surface.

Fracture resistance of yttrium oxide partially-stabilized zirconia all-ceramic bridges after veneering and mechanical fatigue testing.

OBJECTIVES: Yttria-stabilized zirconia (Y-TZP) ceramic is a high-performance material with excellent mechanical properties suitable for fixed partial dentures. The purpose of this study was to evaluate after fatigue testing, the effect of heat-treatment and veneering on the fracture resistance of frameworks manufactured using sintered and subsequently hot isostatic pressed yttrium oxide partially-stabilized zirconia (Denzir). METHODS: The specimens were subjected to dynamic loading in water. Thereafter, using a universal testing machine, the fracture resistance of three-unit fixed partial dentures was determined; (i) of the frameworks as delivered after machining, (ii) after the frameworks had been subjected to heat-treatment similar to veneering with a glass-ceramic (Eris) or a feldspar-based ceramic (Vita D) and (iii) after the frameworks had been veneered with these ceramics. In addition, the fracture resistance of frameworks as delivered after machining not subjected to dynamic loading in water was determined. RESULTS: Cyclic loading in water did not significantly (p>0.05) affect the fracture resistance. The load necessary to fracture the frameworks as delivered after machining was significantly (p<0.001) higher than for the heat-treated and veneered specimens. No significant difference was seen between the specimens veneered with Eris and those veneered with Vita D (p>0.05). For all but three specimens the fractures were located in the loading point and through one of the connectors. SIGNIFICANCE: Heat-treatment and veneering reduce fracture resistance of hot isostatic pressed zirconia. Nevertheless, the results obtained indicate that it is an interesting material for potential in all-ceramic restorations.

A 10-year prospective evaluation of CAD/CAM-manufactured (Cerec) ceramic inlays cemented with a chemically cured or dual-cured resin composite.

PURPOSE: The present follow-up study was carried out to evaluate the performance of Class II Cerec inlays after 10 years of clinical service. MATERIALS AND METHODS: Sixty-six Class II CAD/CAM ceramic inlays were placed in 27 patients. Each patient received at least one inlay luted with a dual-cured resin composite and one inlay luted with a chemically cured resin composite. At the 10-year recall, 25 (93%) patients with 61 (92%) inlays were available for evaluation using a slight modification of the USPHS criteria. RESULTS: Fifty-four (89%) of the 61 inlays reevaluated still functioned well at the 10-year recall. During the follow-up period, seven (11%) of the inlays required replacement because of: four inlay fractures, one cusp fracture, endodontic problems in one case, and postoperative symptoms in one case. All the replaced inlays had been luted with the dual-cured resin composite. The fractured inlays were all placed in molars. The estimated survival rate after 10 years was 89%, 77% for the dual-cured resin composite-luted inlays and 100% for the chemically cured resin composite-luted ones. The difference was statistically significant. CONCLUSION: Patient satisfaction with and acceptance of the Cerec inlays were high, and the performance after 10 years of clinical service was acceptable, especially regarding the inlays luted with the chemically cured resin composite. The properties of the luting agents seem to affect the longevity of the type of ceramic inlays evaluated.

Longevity and quality of FPDs: a retrospective study of restorations 30, 20, and 10 years after insertion.

PURPOSE: The aim of this retrospective study was to investigate the longevity and clinical performance of fixed partial dentures (FPD) 30, 20, and 10 years after insertion. MATERIALS AND METHODS: A total of 289 FPDs were inserted in 1966/67, 1976/77, and 1986/87. For patients with FPDs presumably still in function, an evaluation according to the CDA criteria was made. RESULTS: For 64 of the FPDs (22%), no information was available. Seventy-nine patients with 94 FPDs (33%) were clinically examined, and 44 of the FPDs (15%) were reported to be still in function by the patients' current clinicians. The remaining 87 FPDs (30%) were considered lost to follow-up. These FPDs had either been removed for various reasons--in most cases dental caries, lost retention, or fractured abutment teeth--or the patient could not be contacted. Eighty-four percent of the FPDs inserted in 1966/67 were still in function after 20 years, compared to 64% of those inserted in 1976/77. Apart from an increase in wear and discoloration, the oldest FPDs had excellent marginal fit and anatomic shape. CONCLUSION: The survival rate of 30-year-old FPDs was high; 53% remained in function after 30 years. Based on the CDA criteria, 78% of the restorations were rated satisfactory in all subgroups. The FPDs placed in 1966/67 obtained the highest ratings in color, anatomy, and margin integrity.