The effect of cyclic dislodgement and denture cleanser storage on various attachment systems used in implant-overdenture prostheses.

Purpose: The present study aims to evaluate and compare the retention forces of nylon and polyetheretherketone (PEEK) attachments with different color codes over time and denture cleansers.

Materials and methods: Two plexiglass models were prepared for this study. In the first model, two Astra-Tech EV implants and two Locator abutments were placed, followed by the placement of two corresponding housings in the opposite blocks where nylon attachments were fitted. The second model was mounted with two Medentika Microcone RI implants and two Novaloc abutments. PEEK attachments were then placed in the corresponding housings. Blue-pink-clear nylon and white-yellow-green PEEK attachments' (n = 8 for each group) maximum dislodgement forces were measured at baseline (T₀). Second measurements were conducted after 1080 insertion and removal cycles (T₁). Corega denture cleanser solution was prepared by adding one tablet to 200 mL of tap water. All attachments were soaked in the solution for three minutes and rinsed under running water. Each group of attachments was soaked for 1080 min in total, corresponding to 1 year of clinical use. The final measurements were conducted after storage in the solution. One specimen and abutment were randomly selected from each group and examined using a scanning electron microscope. The data were analyzed by repeated measures ANOVA and Bonferroni multiple comparison test (p < 0.05). The percentage decrease in the dislodgement force of the attachments was also calculated.

Results: Insertion and removal cycles significantly affected the retention values (p < 0.001). Storage in the cleanser did not significantly affect the retention (p > 0.05). The lowest retention value was observed in blue nylon attachments (501.50 ± 33.39 gf [gram force]) after insertion-removal (T₁), with a similar trend after immersion (476.13 ± 39.75 gf) (T₂). The highest retention was observed similarly in clear nylon attachments (1660.38 ± 41.73 gf) after insertion-removal after immersion (1636.50 ± 62.20 gf) (T₂). In terms of percentage loss of retention, yellow PEEK attachments were the most affected group after all test procedures (36.88%), while the lowest affected group was pink nylon attachments (21.56%).

Conclusions: PEEK attachments were the least affected by the denture cleanser but the most affected by insertion and removal cycles. Corega denture cleanser had no significant effect on nylon or PEEK attachments, whereas the insertion-removal cycle had a significant effect on both attachment systems.