ABSTRACT
Objective:To investigate the the retention force changes of 2 kinds of T bar clasps on Cr-Co crowns and the surface ab-rasion of the crowns.Methods:Standard Cr-Co crowns were made,and standard T bar clasps were made of Cr-Co alloy and Vitalli-um2000 with 0.25 mm and 0.5 mm undercut depth respectively.1 800 times repeated placement and removal(fatigue test)were car-ried out on instron testing machine in or without saliva soak condition.The attenuation curves of the maximum retention force was an-alysed.The surface abrasion of the crowns was observed before and after the fatigue test by SEM.Results:The retention force attenu-ation of the clasps in every group was accord with the logarithm attenuation law.SEMexamination showed that in the same condition, there was less surface abrasion in Vitallium2000 group than that in Cr-Co group.Vitallium2000 clasp was superior to Cr-Co clasp in maintaining the retention force.Conclusion:Vitallium2000 T bar clasp may provide better retention force with less furface abrasion on Cr-Co crown than Cr-Co clasp.