Comparison of the Retention of Conventional and Polyvinyl Siloxane Matrix Materials with Different Patrices for...

To compare the retention forces of implant overdenture patrices (ball, bar, and TiSi.snap) to conventional (O-ring, metal housing, and clip) and polyvinyl siloxane (PVS)-based silicone (retention.sil 200, 400, and 600; Mucopren Soft; and GC Reline Soft) matrix materials.

Two implant analogs, in which the patrices were to be placed, were embedded parallel to each other in polyethylene blocks, and the matrices were placed in heatpolymerized acrylic blocks that were fabricated as overdentures. Ten samples were prepared for each attachment type, and 180 samples were obtained from 18 groups. All samples were placed in a chewing simulator for occlusal force application and for insertion and removal of the pieces. Retention measurements were performed with a universal testing device at the initial (10 cycles), simulated first-year (1,825 cycles), and simulated second-year (3,650 cycles) periods, assuming that the patients would insert and remove their overdenture five times daily.

Loss of retention occurred in all the attachment systems at the end of 3,650 cycles (P < .05). The PVS matrix materials showed less retention than the O-ring and metal matrices when a ball patrix was used, while they had higher retention than bar clips when the Hader bar patrix was used (P < .05). Among the PVS matrix materials, retention.sil 200 produced the lowest retention values, whereas retention.sil 600 generated the highest.

PVS matrix materials show higher retention than that achieved by yellow plastic bar matrices. However, these materials exhibit lower retention than with plastic and metal matrices of ball abutments.