Fracture resistances of CAD/CAM monolithic crowns with different occlusal thickness.

Abstract

The aim of this study was to examine the effect of different occlusal thickness on fracture resistances of different monolithic crowns. Materials and methods:Forty molar crowns were fabricated from four different types of monolithic ceramic blocks (n=10): Group I: Vita Enamic (V.enamic), Group II: IPS E-max CAD (e.max), Group III: Celtra Duo(CD), Group IV: Functional explore (f.explore); by means of CAD/ CAM system with two occlusal thickness (1 and 1.5mm).All crowns were cemented on implant abutments using self adhesive resin cement.Combined thermocycling and mechanical loading was performed under a chewing simulator, fracture resistance was examined by universal testing machine.The fractured specimens were inspected by scanning electron microscopy (SEM). Results:The highest fracture resistance was recorded with f.explore group followed by CD group then e.max group while the lowest fracture resistance mean value recorded with V.enamic with statistical significance (P=0.0001<0.05) for both occlusal thicknesses.The 1.5 mm occlusal thickness recorded statistically non-significant (P=0.2267> 0.05) higher fracture resistance mean value than 1mm occlusal thickness except for f.explore group. Conclusions:The fracture resistance of monolithic crowns was differently affected by the ceramic materials and changes in occlusal thickness.Within the limitations of this study, all the tested crowns resisted the physiological range of masticatory forces at 1.5mm and reduced (1.0 mm) occlusal thickness.