A cohort study on short mini-implants for mandibular overdentures compared to those of standard length.

OBJECTIVES: To assess peri-implant bone level, survival and success rates of short (6 or 8 mm long) one-piece mini-implants (MDIs) in edentulous patients with extremely resorbed alveolar ridge (interforaminal height <10 mm) rehabilitated with mandibular implant overdentures and to compare them with patients having standard length MDIs in 1-year prospective clinical study. MATERIAL AND METHODS: The Short MDI group consisted of 28 participants with interforaminal height </=10 mm. Implants being, both, short and slim (short MDIs: 6 or 8 mm long, 2 or 2.5 mm wide) were inserted. The Standard-MDI group included 35 participants (interforaminal height >13 mm) who received standard length MDIs (10-14 mm long, 2 or 2.5 mm wide). Primary outcomes were assessments of MDI peri-implant bone level, survival and success rates; secondary outcomes were assessments of peri-implant tissue, oral hygiene, and prosthodontic maintenance. RESULTS: The Short MDI group had mean marginal bone loss (MBL) of 0.26 +/- 0.35 mm, 6.4% of failure, and 92.6% of, both, success and survival rates. The Standard-MDI group had mean MBL of 0.34 +/- 0.40 mm, 5% of failure, 95% of survival, and 94.3% success. There were no significant differences in MBL (p = .420), survival (p = .414), and success (p = .571) between the groups. The Short MDI group had significantly less plaque (p = .001) and bleeding on probing (p < .001). CONCLUSION: Within the limitations of this study, short MDIs (6 or 8 mm long) in extremely atrophied mandibles (interforaminal height <10 mm) showed good clinical results in the first year of function.