Influence of the Number of Microthreads on Marginal Bone Loss: A Five-Year Retrospective Clinical Study in Humans

The purpose of the present study was to evaluate the clinical and radiographic outcomes of the number of microthreads on marginal bone over 5 years. Thirty-two implants were placed in 32 patients with partially edentulous maxillae or mandibles. Two implants with the same characteristics were placed: the first one had a 1 mm crest module and 3 microthreads (Q); and the second one had a 3 mm crest module and nine microthreads (S). The prosthesis was inserted 3 months after implant placement. Clinical and radiographic examinations were performed at the one-week, one-month, and three-month follow-up visits and then every six months until a five-year follow-up period was completed. After 5 years of follow-up, five patients withdrew from the study. Complete data were available for 27 implants, with a 100% implant survival rate. No cases of peri-implantitis were diagnosed. The average bone loss was 0.65 mm (C.I. 0.21–1.09) for Q implants and 0.86 mm (C.I. 0.39–1.33) for S implants, with no statistically significant difference. The bone level does not vary between implants with three and nine microthreads or with a 1 mm and 3 mm crest module. No differences in clinical parameters were found.