WIDE-DIAMETER IMMEDIATE POST-EXTRACTION IMPLANTS VERSUS SOCKET PRESERVATION AND DELAYED PLACEMENT OF NORMAL-DIAMETER IMPLANTS IN THE MOLAR REGION: 5-YEAR POST-LOADING OUTCOME OF A RANDOMISED CONTROLLED TRIAL

OBJECTIVES. To compare the effectiveness of 6-to 8-mm-wide diameter implants placed immediately after tooth extraction with conventional diameter implants (4.0 or 5.0 mm) placed in preserved sockets after a 4-month healing period in the molar region. MATERIALS AND METHODS. Just after extraction of one or two molar teeth, and in the presence of no vertical loss of buccal bone in relation to the palatal wall, 100 patients were randomly allocated to either immediate placement of one to two 6-to 8-mm-wide diameter implants (immediate group; 50 patients) or one or two 4.0-or 5.0-mm-wide delayed implants to be placed four months after socket preservation using a porcine bone substitute covered by a resorbable collagen barrier (delayed group; 50 patients) by a single operator according to a parallel group design. Bone-to-implant gaps at immediate implants were filled with autogenous bone retrieved with the trephine drill used to prepare the implants sites. Implants were loaded 4 months after placement with provisional acrylic fixed prostheses, joining both implants when present. After 4 months, definitive metal-ceramic fixed prostheses were fitted. Patients were followed up to 5 years after loading. Outcome measures were: restorations and implant failures; complications; aesthetics, assessed using the pink aesthetic score (PES); pe-ri-implant marginal bone level changes; and patient satisfaction, recorded, when possi-ble, by blinded assessors. RESULTS. Five years after loading, seven patients from the immediate group and eight from the delayed group dropped out. Ten out of 43 patients in the immediate group (23.3%) experienced one implant failure versus two out 42 (4.8%) in the delayed group, the difference being statistically significant (difference in proportion = 18.5%, 95% CI: 4.3 to 32.7%, P = 0.03). Sixteen patients in the immediate group were affected by 21 complica-tions, and four patients by four complications in the delayed group, a statistically significant difference (difference in proportion = 26.0%, 95% CI: 9.4 to 42.6%, P = 0.005). Five years after loading, patients in the immediate group lost on average 1.82±0.72 mm of peri-im-plant marginal bone, and those in the delayed group lost 0.84±0.33 mm, the difference being statistically significant (1.04 mm; 95% CI: 0.75 to 1.32; P <0.0001). Photographs of only two immediate implants were taken, so no aesthetic evaluation could be performed. All patients were fully or partially satisfied with both function and aesthetics, and would undergo the same procedure again. CONCLUSIONS. Despite all the limitations of this study, the findings indicate that immediate placement of 6-to 8-mm-wide diameter implants in molar extraction sockets yiel-ded unacceptable outcomes when compared to ridge preservation and delayed placement of conventional 4-or 5-mm diameter implants. CONFLICT OF INTEREST STATEMENT. This trial was partially funded by the manufacturer of the implants evaluated in this investigation (MegaGen Implant, Gyeongbuk, South Ko-rea) up to 1 year after loading, and then by the producer of the bone substitutes and membranes used in this study (Tecnoss, Giaveno, Italy) thereafter. However, the data be-longed to the authors and the manufacturers did not in any way interfere with the con-duct of the trial or the publication of its results.