24829969
OBJECTIVE	The purpose of this ongoing randomized study was to assess differences in bone level changes and success rates using implants supporting single crowns in the posterior mandible either with platform matched or platform switched abutments .
METHODS	Patients aged 18 and above , missing at least two teeth in the posterior mandible and with a natural tooth mesial to the most proximal implant site were enrolled .
METHODS	Randomization followed implant placement .
METHODS	Definitive restorations were placed after a minimum transgingival healing period of 8 weeks .
METHODS	Changes in crestal bone level from surgery and loading ( baseline ) to 12-month post-loading were radiographically measured .
METHODS	Implant survival and success were determined .
RESULTS	Sixty-eight patients received 74 implants in the platform switching group and 72 in the other one .
RESULTS	The difference of mean marginal bone level change from surgery to 12 months was significant between groups ( p < 0.004 ) .
RESULTS	Radiographical mean bone gain or no bone loss from loading was noted for 67.1 % of the platform switching and 49.2 % of the platform matching implants .
RESULTS	Implant success rates were 97.3 % and 100 % , respectively .
CONCLUSIONS	Within the same implant system the platform switching concept showed a positive effect on marginal bone levels when compared with restorations with platform matching .

