Abstract
About 70% of the restorations are made to replace previous restorations.Secondary caries was the main reason for replacement of amalgam fillings, and poor marginal adaptation(ditching/leakage)and isthmus fracture(bulk fracture)were another reason.Poor marginal adaptation was considered to be the cause of secondary caries.The mechanism of marginal fracture of amalgam fillings has been studied by many workers.In this study, the axi-symmetric elastic creep finite element method was applied to simulate the development of the marginal gap and ditch at the interface of the amalgam and tooth.Here, the occlusal force was assumed loaded on the amalgam fillings with creep and vertical direction to the axis of the tooth.The gap and ditch were developed proportionally with the creep value of the amalgam(American Dental Association specification no.1)and proportionally square of the occlusal force.From the estimation of the service life of the restoration, it was concluded that the poor adaptation at the margin can be seen in 4-to-10-year old amalgam fillings when the amalgam with a high creep value was used or high chewing force was loaded on the fillings.This is consistent with the clinical findings reported.
