Effect of loading on the development of nerve fibers around oral implants in the dog mandible

Occlusal forces cause stress which morphologically affects the supporting t issues of implants. The aim of this study was to examine the effects of occ lusal forces on the distribution of neurofilament protein (NFP)-positive ne rve fibers in the tissue of periimplant bone. The bilateral 2nd, 3rd and 4t h mandibular premolars and the Ist molars were extracted from three mongrel dogs. After 4 months of healing, 4 screw-type implants were inserted in th e oral cavity. Three months after insertion, the implants on the molar site were loaded by occlusal forces, while those on the premolar site were unlo aded. After a further 3 months, the dogs were sacrificed, and specimens wer e prepared for immunohistochemical NFP-positive staining by the labeled-str eptavidinbiotin method. Many NFP-positive nerve fibers were found in the ti ssues of the loaded site when compared with the unloaded site. These fibers were localized in both the bone marrow space and in the peri-implant fibro us tissue. They had two types of nerve endings: simple free nerve endings, and nerve endings with tree-like ramifications. The present results suggest that loading by occlusal force causes an increase in the number of NFP-pos itive nerve fibers, many of which have free nerve endings in the peri-impla nt tissue. The possible role of these NFP-positive nerve fibers is discusse d.