Retention and wear of nylon matrix component in implant-supported overdentures based on insertion technique: A clinical trial

Attachments are used for connections between overdentures and dental implants. The maintenance of attachment components plays an important role in optimal clinical service of overdentures. This study aimed to compare the effects of overdenture insertion by hand pressure versus placement by clenching the jaws on the retention and diameter of resilient attachments. Thirty patients with mandibular overdentures participated in this study. First, the patients were instructed to insert the overdentures with hand pressure. After 6 months, patients were recalled, the nylon matrix components of the attachments were replaced, and the patients were instructed to place the overdentures by clenching for the next 6 months. The retention and internal diameter of matrices were measured at baseline and at 6 and 12 months later. A universal testing machine was used to measure the residual retention, and a coordinate measuring machine was used to assess the matrix diameter. The retention loss and changes in matrix diameter were compared between the two techniques, using paired samples t-test. The results showed that retention loss was lower in the hand placement method than in the clenching method (P<0.001). The two insertion methods were not significantly different regarding the amount of diameter increase (P=0.074). The residual retention of the matrices was significantly greater in the hand placement of overdentures along the longitudinal attachment axis, which may result in greater efficacy and longevity of implant overdentures.