Prospective study of 94 platform-switched implants observed from 1992 to 2006.

The purpose of the present prospective study was to evaluate implant survival and crestal bone levels around implants that used the platform-switching concept and were followed for a minimum of 11 years. Radiographs of 94 implants obtained 11 to 14 years after loading were evaluated by measuring the location of the crestal bone level relative to the implant platform. All implants had been placed at the crestal level at the time of surgery. Using the known distance of 0.8 mm between the peaks of adjacent threads, a determination was made on the radiographs of the amount of bone lost. Seventy-one of the 94 implants (75.5%) showed no bone loss on the mesial aspect, and 67 (71.3%) showed no bone loss on the distal aspect. Eighty-four percent of the mesial surfaces and 88% of the distal surfaces had 0.8 mm or less of bone loss. This is the longest follow-up to a prospective investigation of platform-switched implants and confirms the concept for preservation of crestal bone levels.