歯石様石灰化物の付着を認めたHAコーティングインプラントの撤去症例について

―SEM， EPMA， WDXによる観察―

抄録

Hydroxyapatite (HA)-coated implants have been a subject of great interest since the mid-1980 s. Various clinical studies have shown that HA-coatings lead to good clinical results over a 15-year period. Statistics with a success rate of 95% were reported over a 5-year period. More recently, however, an increased number of failures with HA-coated implants have been reported.
One case of an HA-coated implant, which had to be removed due to implant mobility, marginal swelling and redness, and marginal bone loss (funnel-shaped resorption) around the implant, at 4 years after the implant had been placed, in a 48-year-old male patient, was reported. An explanted HA-coated titanium cylinder-form implant was examined, using scanning electron microscopy (SEM) and an electron probe X-ray microanalyzer (EPMA) to analize the main constructive elements. Also, soft tissue removed from the implant socket was microscopically examined.
The results were as follows
1. The removed implant demonstrated, macroscopically and microscopically, a dental calculus-like deposit on the plasma-sprayed surface, and loss of the HA-coating, with the presence of a smooth titanium substrate.
2. The loss of HA-coating was seen within the hole of the apical end of the implant.
3. For the EPMA data, the implant material mainly consisted of titanium, with a loss of the HA-coated layer. The dental calculus-like deposit chiefly consisted of calcium and phosphate, and showed no bone structure.
4. Microscopic examination revealed that granulation tissue replaced the resorbed bone and was separated from the implant itself by proliferating squamous epithelium. Epithelium proliferated apically to the encapsulated granulation tissue. The granulation tissue that resulted from the inflammatory process began marginally and followed the bacterial movement; the process proceeded rapidly with the loss of an implant.
From the above results, marginal bone loss may be induced by etiologic factors known to be causative, such as bacterial infection and mechanical overload. The most important factors for preventing late complications with implant-prosthetic treatment are the peri-implant osseous and soft tissue conditions. A check of the implant-borne suprastructure is essential. A thorough cleaning of the implant, as well as any remaining natural teeth of the patient who receives implant-prosthetic treatment, is necessary.