Comparison of retention values of different polyvinylsiloxane matrix materials on different types of patrices in implant-supported overdentures

Aim: The aim of this study was to compare the retention values of four polyvinyl siloxane (PVS) materials used as matrix parts over ball, locator and TiSi.snap attachments with the retention values of each other and conventional matrices in implant-retained overdentures. Materials and Methods: 140 specimens each consisting of two parts were prepared (n: 10). The lower part consisted of two implant analogs embedded perpendicularly in plexiglass and two patrices screwed on top of them. These patrix attachments were ball (DTI Implant Systems, Turkey), locator (DTI Implant Systems, Turkey), and TiSi.snap (Bredent GmbH & Co.KG, Germany). The upper part of the specimen containing the matrix components and simulates an implant-supported overdenture, was milled from polymethyl methacrylate (PMMA) blocks. As matrices, four PVS materials (Retention.sil 200, Retention.sil 400, Retention.sil 600, and GC Reline II Soft) were used for all attachment types, as well as conventional matrices for ball and locator attachments. Each specimen was subjected to thermal cycling, and occlusal force application in a chewing simulator. Retention values were recorded at initial, after 1 year of use (1490 cycles), and after 2 years of use (2920 cycles). Results: For ball and locator attachments, conventional matrices provided significantly higher retention values than PVS matrix materials (p= 0.0001). The highest retention value (84.75 N) among all groups was obtained when ball attachment combined with the conventional matrix at the initial measurement. For all patrix and matrix combinations, initial retention values decreased proportionally as the usage time increased (p<0.05). Among PVS matrices, the highest retention value was observed with Retention.sil 600, and the lowest with Retention.sil 200 for all patrix groups. Conclusion: PVS matrices showed significantly lower retention values than conventional matrices. As the hardness values of PVS matrix materials increased, the retention values at the initial measurements also increased.