The concept of platform-switching has been introduced to implant dentistry based on clinical observations of reduced periimplant crestal bone loss. However, published available data are controversial and most studies are limited to 12 months. The aim of the present RCT was to test the hypothesis that platform-switching has a positive impact on crestal bone level changes after 3 years.

Two implants with a diameter of 4 mm were inserted crestally in the posterior mandible of 25 subjects. After three months of submerged healing, single-tooth crowns were randomly placed, either with (3.3mm platform, test) or without platform-switching (4mm platform, control). Patients were followed up at short intervals for monitoring of healing an oral hygiene. Statistical analysis for the influence of time and platform-type on bone levels employed the Brunner-Langer Model.

Inclusion Criteria:

• good general health
• edentulous gap in the posterior mandible for placement of 2 implants
• sufficient bone height above the alveolar nerve for placement of implants with a height of 9.5mm
• bone width for placement of implants with diameter of 4mm
• at least 4mm keratinized mucosa
• medium or a thick soft tissue biotype

Exclusion Criteria:

• infectious disease
• diabetes or osteopathy
• active periodontitis
• medication influencing bone metabolism
• lactating or pregnant women