Brushing effect on the retentive force of retentive inserts in three denture attachments: An in vitro study

Abstract

Statement of problem: Daily denture brushing results in wear on implant-retained overdenture attachments. However, studies on the remaining denture attachment retention after brushing are lacking. Purpose: The purpose of this in vitro study was to evaluate the retentive force of the retentive inserts in 3 denture attachments after brushing with different media. Material and methods: Three retentive insert types in 3 denture attachments (LOCATOR, LOCATOR R-Tx, and Novaloc) were tested. Three abutments and 20 metal housings of each denture attachment were separately embedded into individual acrylic resin blocks, and 20 retentive inserts of each retentive type in each denture attachment were placed in the metal housing. The blocks embedded with a metal housing of each denture attachment were divided into 2 brushing media groups (n=10), mounted on a brushing machine, and brushed with deionized water (DI) or toothpaste slurry (TP). After 0, 10 000, and 20 000 brushing cycles, the block specimens were mounted on a universal testing machine, and the retentive force was evaluated by pulling the blocks apart until complete separation. The maximum retentive force was measured 5 times and averaged. The evaluated retentive insert was removed and replaced with a new retentive insert. The specimen blocks were subjected to another brushing test with the same protocol. Representative specimens of each group were examined with scanning electron microscopy. The retentive force of each retentive insert type in each denture attachment was analyzed by 2-way repeated measures ANOVA, followed by the Bonferroni test (α=.05). Results: The retentive force of each LOCATOR and LOCATOR R-Tx retentive insert demonstrated significant differences in the interaction between brushing media and brushing cycles (P<.05). Between baseline and 20 000 brushing cycles with DI, the retentive force of the LOCATOR and LOCATOR R-Tx retentive inserts decreased significantly (P<.05). Between baseline and 20 000 brushing cycles with TP, the retentive force of the LOCATOR retentive inserts increased significantly (P<.05), while the retentive force of the LOCATOR R-Tx retentive inserts was statistically similar (P>.05). The retentive force of the Novaloc retentive inserts demonstrated significant differences only for brushing cycles (P<.05). The Novaloc retentive inserts decreased in average retentive force over time. Conclusions: After brushing with deionized water, the retentive forces of the LOCATOR, LOCATOR R-Tx, and Novaloc retentive inserts decreased, while, after brushing with toothpaste, the retentive force of the retentive inserts increased in the LOCATOR group, was unchanged in the LOCATOR R-Tx group, and decreased in the Novaloc group.