Within the limits of this study, the present results suggest that bone resorption is mostly related to biologic (biologic width re-establishment) rather than to biomechanical factors (implant platform diameter). Furthermore long-term studies with a wider sample size are needed to confirm the platform diameter influence on hard tissue response around implants restored according to the PS concept.

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The study aims were to evaluate survival rates of dental implants in patients wearing maxillary and mandibular overdentures in relation to age, sex, smoking, implant splinting or non-splinting, the maxilla rehabilitated, and number of implants per dental arch. This was a prospective study of patients who were completely edentulous in either mandible or maxilla or both, rehabilitated with implant-retained overdentures, with a follow-up of at least 3 years. 95 patients with 107 overdentures were supported by 360 implants were included in the study. Rehabilitations were monitored over an average of 95 ± 20.3 months (range 36-159). Implant survival in the maxilla was 91.9% and in the mandible 98.6%, representing a statistically significant difference (P < .05). Age, sex and implant splinting did not influence survival rates significantly. Smokers presented a lower survival rate. Implant numbers in the maxilla had a significant influence on survival, 100% for 6 but 85.7% for 4. Three mandibular implants achieved higher survival rates (100%) but with 2 (96.6%) or 4 (99%) survival was lower, although without significant difference. Long-term results suggest that 3-implant mandibular overdentures have an equivalent survival rate to 4-implant overdentures. In the maxilla, results showed that 6 implants may be the best treatment strategy. For smokers with fewer implants retaining the overdentures, there were higher numbers of implant failures.