Crestal bone changes in macrogeometrically similar implants with the implant-abutment connection at the crestal bone level or 2.5mm above: a prospective randomized clinical trial.

Abstract

Crestal bone loss around dental implants is a criterion for success as this could prevent loss of implant and superstructure. The macrogeometry of the implant could influence bone remodelling when the implant-abutment connection is placed at crestal bone level or above. The aim of this study was to evaluate crestal bone remodelling in a randomized clinical prospective trial in macrogeometrically similar implants with the prosthetic connection at the crestal bone level and 2.5mm above. The null hypothesis was that there was no difference in crestal bone loss after 1year of early loading. Patients were referred to Academic Centre of Dentistry Amsterdam for implant placement. Patients were subjected to inclusion and exclusion criteria and received a minimum of two implants: an implant with the prosthetic abutment connection at the crestal bone level (minimized collar [MC], bone level) and one with the prosthetic abutment connection 2.5mm supracrestal (long collar [LC], tissue level). The mesial or distal location of each implant type was blinded for the patient and randomized. The implants were loaded splinted after 3weeks of healing. The primary outcome was bone-level change assessed after 1year of loading. Thirty-three patients fulfilled the inclusion criteria. Thirty-nine Thommen SPI ELEMENT LC implants and 39 MC were placed, and each fixed dental prosthesis was supported by one LC and one MC implant. The intraclass correlation of measures performed by the first and second X-ray examiner was as follows: on the mesial side of the MC implant 0.990 (0.980-0.995; 95% confidence interval [CI]), 0.980 (0.962-0.990; 95% CI) on the distal side of the MC implant, 0.979 (0.959-0.989; 95% CI) and 0.988 (0.978-0.994; 95% CI) on the mesial and distal side of the LC implant, respectively. The mean bone loss of the MC implant was 0.4±0.4mm. The mean bone loss of the LC implant was 0.2±0.5mm. The paired samples t-test showed a statistically significant difference (P<0.05) between the MC and LC implants. Dental implants at bone level show statistically significantly (P<0.05) more crestal bone change after 1year of loading than a tissue-level implant.