A THREE-YEAR TWO-CENTER RANDOMIZED CONTROLLED TRIAL COMPARING SINGLE 6-MM VERSUS 10-MM LONG IMPLANT-SUPPORTED CROWNS IN POSTERIOR JAWS

PURPOSE. The aim of this study was to compare the clinical and radiographic outcomes of single dental implants of two different lengths (6 mm versus 10 mm) placed in healed posterior sites and restored with single crowns.

MATERIALS AND METHODS. Forty patients requiring a single implant-supported restoration in the posterior regions of the maxilla or mandible were selected and randomized to receive either 6-mm implants (test group, n = 20) or 10-mm implants (control group, n = 20). Impressions were taken three months after placement, and the implants were restored with single fixed crowns. The primary outcome was implant failure. Secondary outcomes included changes in peri implant marginal bone levels, biological and mechanical complications, and gingival health indicators such as plaque index (PI), calculus index (CI), bleeding index (BI), and probing depth (PD).

RESULTS. Forty implants, all featuring a double acid-etched and sandblasted surface, were placed successfully. One 6-mm implant failed during the first year. Three years after loading, no drop-out occurred with no difference in success rates between the test and control group (-5% with a 95% confidence interval, CI 95% -15 to +5%; p-value = 1). One patient in the 6-mm group and six patients of the 10 mm group were affected by complications, the difference was not statistically significant (-25% with a 95% CI ranging from -52.5% to +2.5%; p-value = 0.0915). No statistically significant differences were observed at the final follow-up for gingival health indicators between the test and control groups: 21% versus 15% for positive plaque index, with a difference of +6% (CI 95%: -23.2 to +35.2%; p-value = 0.6947); 36.9% versus 50% for a positive bleeding index, with a difference of -13.1% (CI 95%: -49.1 to +22.9%; p-value = 0.8517); and 2.6mm versus 2.7mm for probing depth with a difference of -0.10mm (CI 95%: -0.43 to +0.23mm; p-value = 0.7680).
Both groups exhibited a decrease in marginal bone levels from baseline to the 3 year follow-up (-1.08+0.40mm and -1.02+0.40mm, respectively for short and standard groups), with an observed test-standard difference in means of -0.06±0.40mm (CI 95%: -0.22 to +0.10; p-value = 0.1849).

CONCLUSIONS. This study found no statistically significant differences in outcomes between 6-mm and 10-mm implants supporting single crowns in the posterior maxilla or mandible. Both implant lengths demonstrated high success rates and comparable clinical and radiographic performance over the 3-year follow-up period.