Objectives:To evaluate the influence of restoration thickness and auxillary retentive means on fracture resistance of occlusal ceramic veneers.
Materials and Methods: Forty sound molars were chosen which are free from caries,The teeth were restored with ceramic occlusal veneers of CAD /CAM lithium disilicate material and divided to two groups.Group(1) without finish line ,Group(2) with finish line.Each group had 10 molars with buccal groove extension and 10 molars without it of different thickness 1&1.5 mm.Usage of universal testing machine to measuring the fracture strength of lithium di silicate material after loading till fracture.
Results. Only specimens in the group with the thickest thickness of (1.5 mm ) survived cyclic loading without any damage. Survival rates in the remaining sub-groups ranged from 50 to 100% for surviving with some damage and from 12.5 to 75%for surviving without any damage. Medians of final fracture resistance ranged from 772 to 902 N. In groups with larger ceramic thickness (1.5 mm) provided statistically significant (p ≤0.007) higher fracture resistance than smaller one.
Significance. Usage of 1.5mm thickness buccally retentive lithium disilicate ceramic occlusal veneers can restore successfully severely abraded teeth.