Adapting the vertical position of implants with a conical connection in relation to soft tissue thickness prevents early implant surface exposure : a 2-year prospective intra-subject comparison

Aim: To evaluate the effect of soft tissue thickness on bone remodelling and to investigate whether implant surface exposure can be avoided by adapting the vertical implant position in relation to the soft tissue thickness. Materials and Methods: Twenty-five patients received two non-splinted implants supporting an overdenture in the mandible. Soft tissue thickness was measured using bone sounding and ultrasonically. One implant was installed equicrestally (control), and the vertical position of the second implant was adapted to the site-specific soft tissue thickness (test). Crestal bone levels were determined on digital peri-apical radiographs and compared with baseline (implant placement). Results: Twenty-five patients were consecutively treated. No implants failed during the follow-up. A significant correlation was observed between soft tissue thickness and bone level alterations after 6 months (ultrasound ICC=0.610; bone sounding ICC = 0.641) with inferior bone levels for equicrestal implants when thin tissues are present. Subcrestal implants showed significantly better bone levels after 6-month (n = 24, 0.04 mm versus 0.72 mm; p < .001), 1-year (n = 24, 0.03mm versus 0.77 mm; p < .001) and 2-year follow-up (n = 24, 0.04 mm versus 0.73 mm; p<.001). Conclusion: Initial bone remodelling was affected by soft tissue thickness. Anticipating biologic width re-establishment by adapting the vertical position of the implant seemed highly successful to avoid implant surface exposure