Wear of I-bar clasps and porcelain laminate restorations

Partial-coverage porcelain laminate restorations, placed to provide undercut areas for I-bar direct retainers of removable partial dentures, were evaluated over simulated 2- and 5-year periods of placement and removal movements. SEM photomicrographs and computer imaging were used to quantify wear of the I-bar tips and the contacting laminate surfaces. These data were statistically compared to previously collected data of I-bar clasp tip wear against human enamel under the same experimental conditions. None of the laminate restorations debonded during this investigation. I-bars contacting laminates exhibited significantly more wear than I-bars contacting human enamel; however, the combined laminate-I-bar wear compared to the combined enamel-I-bar wear produced no significant difference.