COMPARATVE EVALUATION OF FAILURE LOAD OF TWO DESIGNS CAD/CAM ZIRCONIA FIXED PARTIAL DENTURES USING LASER SCANNING CONFOCAL MICROSCOPY

Document Type : Original Article

Authors

1 Instructor at the Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt

2 -Professor of Fixed Prosthodontics, Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt.

3 Professor of Dental Biomaterials, Dental Biomaterials Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt.

Abstract

INTRODUCTION: Chipping of the porcelain veneer was a common failure of zirconia based restorations, especially in the presence of high occlusal loads. The development of full-contour monolithic zirconia (MZ) restorations promises an end to the heartbreak of fractured esthetic porcelain on posterior restorations. The clinical recommended thickness of zirconia monolithic restorations has not been reported. It is essential to find out a proper thickness guarantee not only the load bearing capacity but also conservation of dental hard tissues. OBJECTIVES: was to evaluate the failure load of two different preparation designs – (classical and conservative) – in three units monolithic zirconia fixed partial dentures. MATERIALS AND METHODS: 2 parallel groups (n = 5/group) examined in this study. Group I: Classical tooth preparation design with occlusal reduction of 1.5 mm and rounded 1 mm finish line. Group II: Conservative tooth preparation design with occlusal reduction 0.5 mm and rounded 0.2 mm finish line. All fixed partial dentures (FPDs) adhesively luted on epoxy resin dies and subjected to thermal cycling and cyclic loading corresponding to 6 months of clinical service. Specimens then loaded till failure in a universal testing machine. The load of failure recorded in Newton. Fractographic analysis was done using stereomicroscope, scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). Data statistically analyzed using Student t-test. RESULTS: None of the FPDs failed during the aging process. Mean of failure load of Group I was 1317.36 ± 186.11 N and for Group II was 1215.92 ± 217.03 N without significant difference between the groups (P =0.450). CONCLUSIONS: The conservative tooth preparation design of the posterior three units FPDs was a very good alternative to the classical one. Aging behavior, translucency testing, color reproduction and long-term clinical performance need to be further assessed before recommending this conservative FPDs design for daily practice.

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References

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