Clinical and radiographic changes at implants supporting single-unit crowns (SCs) and fixed dental prostheses (FDPs) with one cantilever extension. A retrospective study

Objectives: To evaluate the clinical and radiographic changes at implants in posterior maxillary and mandibular areas supporting single-unit crowns (SCs) and fixed dental prostheses (FDPs) with one mesial or distal cantilever extension after an observation period of at least 3 years. Material and methods: Seventeen subjects with 19 implant-supported SCs and 21 subjects with 21 implant-supported FDPs fulfilled the inclusion criteria. All FDPs were supported by two implants and had a span of 3-4 units. All reconstructions were incorporated in the posterior maxilla or mandible. The mesial and distal radiographic marginal bone loss from baseline (i.e. delivery of the reconstruction) to the follow-up examination was averaged and compared between SCs supporting one cantilever extension with that of implants supporting FDPs adjacent to or distant from the cantilever extension. Changes in mean pocket probing depth (PPD) were calculated and compared between the three groups. Results: The mean observation period was 78.2 +/- 34.5 months for SCs supported by one implant and 67.8 +/- 29.8 months for FDPs supported by two implants. No implant loss occurred, yielding a 100% survival rate. At baseline, the mean radiographic bone levels +/- SD were 2.6 +/- 0.3 mm for implants supporting SCs, 2.6 +/- 0.3 mm for implants of FDPs adjacent to the cantilever extension, and 2.4 +/- 0.5 mm for implants of FDPs distant from the cantilever extension. At follow-up, the corresponding mean bone levels +/- SD were 2.7 +/- 0.4, 2.7 +/- 0.5, and 2.8 +/- 0.5 mm, respectively. No statistically significant differences (P > 0.05) were observed comparing the mean marginal bone loss between the three groups. Moreover, mean changes in PPD between baseline and follow-up were not statistically significantly different (P > 0.05) between the three groups. Conclusion: The presence of one mesial or distal cantilever extension in the posterior maxilla or mandible does not jeopardize the marginal bone levels of implants supporting SCs or short-span FDPs after a mean observation period of at least 5 years.