Objectives: This study aimed to test the hypothesis of an influence of platform switching on crestal bone changes.
Methods: In a split-mouth design two implants with a diameter of 4 mm were inserted epicrestally in the posterior mandible of 25 subjects. After three months of submerged healing single-tooth crowns were placed, either with (3.3mm platform, test) or without platform switching (4mm platform, control). Patients were then followed up at short intervals for monitoring of healing and for oral hygiene control. Microbiological samples were taken from the implant interior at baseline, abutment connection, restoration and after 12 months. The height of the prosthetic suprastructure from the implant shoulder to the highest cusp tip was measured. Standardised radiographs (baseline, 3, 4 and 12 months) were independently evaluated by three calibrated examiners.
Results: After one year the mean radiographic periimplant bone loss (vertical / horizontal extent of vertical defects) around the test implants was 0.56±0.44mm / 0.21±0.38mm and around the control implants 0.61±0.57mm / 0.40±0.46mm. The mean difference (vertical / horizontal) between the two treatment modalities was 0.05±0.54mm / 0.19±0.59mm (p > 0.05). There was no influence of crown height (range: 5.38 - 10.50mm) on crestal bone loss. Regardless of platform design, a greater microbial colonisation of the implant interior was associated with greater periimplant bone loss (p=0.046).
Conclusions: The present randomised clinical trial could not confirm the hypothesis of a reduced periimplant crestal bone loss, when implants had been restored according to the concept of platform switching.