Effect of Implant Height Differences on the Retention and Wear Behaviour of Ball Attachment System in Mandibular Two-Implant Over Dentures: An In Vitro Study

Abstract

PURPOSE: The purpose of this study was to evaluate in vitro, the effect of implant height differences on the retention and wear behaviour of ball attachment system in mandibular two-implant over dentures. MATERIALS AND METHODS: 22 wax blocks were fabricated and out of these, 2 were used as master blocks and 20 were used as prosthetic blocks. 2 implant analogs were placed in each master wax block with same height in one block and with different height in the other block. Both the master and prosthetic wax blocks were then heat cured. The attachments were placed in the master block and transferred to the prosthetic block by Direct Pick up technique. Group I had test samples placed at same height and Group II at different height. The retention force was tested from baseline to 1440 cycles with 3 time intervals simulating 1 year of clinical use, using Universal testing machine. The data obtained were then subjected to statistical analysis using ‘t’-test. The surface wear was qualitatively evaluated using Stereo microscope. RESULTS: The mean retention force for Group I and II at baseline, 360, 720, 1080, and after 1440 cycles were 24.73N, 23.49N, 22.46N, 21.07N, 19.28N and 27.13N, 25.80N, 24.16N, 22.73N and 21.85N respectively. Group II showed statistically higher retention force than Group I. Both the groups showed significant retention loss over a period of 1 year and wear on the surface of the attachments evaluated. CONCLUSION: Within the limitations of the study, the retention values obtained from the implant analogs placed at different height was significantly higher than that of at same height. But both the values were higher from the value considered minimal for overdenture stability