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.