the amount of wear in attachment of implant-supported overdentures in mandible

Background and objectives: one of the simplest and cheapest attachments for overdentures, is the ball-type attachment, however, keeping it during the first year of prosthesis delivery and after that is one of the main concerns of dentists. the present study aimed to assess the wear of matrix in overdentures attachment supported by one, two and three implants in the mandible. materials and methods: thirty edentulous patients were randomly divided into three groups: the first group received a single implant in the midline of the lower mandible, the second group two implants in areas b and d, and the third group three implants in areas b, c, and d. the attachment used in patients’ prosthetic with single and two implants was o-ball/ring attachment and for patients with three implants, the treatment plan was ball bar-supported attachments. after placing the new matrix implant for each patient and obtaining their consent, the matrix wear was measured with cmm (coordinate measuring machine) device. to compare matrix wear after six months and one year, measurements were repeated. data analysis, using anova and multiple comparisons was down by tukey test. variance with repeated measures and tukey test were used to compare the groups two-by-two. p.value less than 0.05 was set statistical significant. spss 16 software was used for data analysis. results: the data obtained from the cmm device showed that the lowest mean matrix wear in the maximum single implant and maximum mean were in group two. conclusion: both time and the number of implants had a significant effect on the wear of the o-ring.