Fate of the HA Coating of Loaded Implants in the Augmented Sinus Floor: A Human Case Study of Retrieved Implants

A histomorphometric study was performed on six retrieved loaded hydroxyapatite (HA)-coated titanium implants.The implants had been clinically functioning in a 50-year-old patient. She originally presented a severely atrophic maxilla that was reconstructed by sinus floor augmentation using autogenous bone from the iliac crest. In spite of good clinical function, because of psychiatric problems, all implants, including some bordering bone, were removed using a trephine bur. Thin ground sections were prepared for histology and used for histomorphometry. The aim of this study was to observe the condition of the calcium phosphate coating after 2.5 years of functional loading, the nature of the bone-to-implant interface, as well as the density of the bone graft around the implants. Intimate and abundant bone-to-implant contact was observed, ranging from 90.4% to 99.8% along the implant surface. Active bone remodeling occurred within all threads, as demonstrated by secondary osteons close to the implant surface. The thickness of the calcium phosphate coating varied from 51 to 88 µm for the loaded retrieved implants, versus 53 to 89 µm for the nonused control implant. All implants showed bone contact including the first thread and up to the smooth titanium neck. Both the nature and thickness of the coating had hardly changed after 2.5 years of loading. The HA-coated implants used achieved excellent osseointegration and must be considered clinically safe and effective in maxillary grafted bone.