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0.5 MM VERSUS 1.5 MM SUBCRESTAL PLACEMENT OF DENTAL IMPLANTS WITH INTERNAL CONICAL CONNECTION: EIGHT-YEAR POST-LOADING RESULTS FROM A MULTICENTRE WITHIN-PERSON RANDOMIZED CONTROLLED TRIAL

PURPOSE. To determine whether there are clinical advantages to placing single dental implants 0.5 versus 1.5 mm subcrestally in healed bone crests.

MATERIALS AND METHODS. Sixty partially edentulous patients requiring two single implant- supported crowns had both sites randomly allocated to either 0.5 mm or 1.5 mm subcrestal implant placement according to a split-mouth design at six centres; implant sites were left to heal for 3 months either submerged in aesthetic areas or not in non-aesthetic areas. Provisional acrylic crowns were fitted and after 2 months replaced by definitive metal-ceramic crowns. Patients were followed up to 8 years after loading. Outcome measures were: crown or implant failures; complications; aesthetics, assessed using the pink esthetic score (PES); peri-implant marginal bone level changes; and patient preference, recorded by blinded assessors.

RESULTS. Out of the 54 patients, 7 dropped out. There were no statistically significant differences between groups in failure rates (seven implants failed in the 0.5mm group versus three in the 1.5-mm group; difference = 0.07; P = 0.125) or complications (in the 0.5-mm group ten complications occurred in nine patients versus seven complications in seven patients in the 1.5-mm group; difference = 0.04; 95% CI 0.37 to 10.92; P = 0.688). At 8 years after loading, the mean pink aesthetic score was 11.04±2.27 and 10.6±2.46 for the 0.5 and 1.5 mm group, respectively. There were no statistically significant differences between the two groups at 8 years (P = 0.367). Eight years after loading, patients of the 0.5 mm lost on average 0.17±0.45 mm and those of the 1.5 mm group 0.15±0.50 mm, the difference not being statistically significant (difference = -0.10 mm; 95% CI -0.22 to 0.02; P = 0.091). Patients did not prefer any depth of the implant placement over the other. There were no differences in outcomes among centres, except for the number of patients with no preferences (P = 0.047). However, patients were equally satisfied with both implant placement sites.

CONCLUSIONS. Eight years after loading, no statistically significant differences were found between 0.5 mm vs. 1.5 mm subcrestal placement when implant were surrounded by at least 1 mm of bone, and clinicians are therefore free to choose which depth they prefer.

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