CORTICAL BONE INGROWTH IN GROWTH HORMONE-LOADED GROOVED IMPLANTS WITHCALCIUM-PHOSPHATE COATINGS IN GOAT FEMURS

Dental implants are successfully used for tissue-integrated protheses, but the long-term survival in the maxilla is shorter than in the mand ible [Cune MS, Thesis, University of Utrecht, 1993; Jaffin RA, Berman CL. J Periodontol 1991,62:2-4]. However, by adding growth hormone at i mplantation, increased bone apposition may be expected, since it is kn own that growth hormone has a stimulating effect on the differentiatio n and proliferation of osteoblastic cells [Ernst M, Froesch ER. Bioche m Biophys Res Commun 1988;151:142-47; Scheven BAA et al. Growth Regul 1991;1:160-67; Stracke H et al. Acta Endocrinol 1984;107:16-24]. We st udied bone ingrowth and bone contact of grooved implants impregnated w ith growth hormone in the cortex of femurs of female goats. We compare d the effect of growth hormone on grooved implants with or without cal cium phosphate coatings at the bottom of the grooves. The coatings use d were hydroxyapatite, fluorapatite and heat-treated hydroxyapatite. T he implants had both small and large grooves. The implants were positi oned in the cortex of one femur and were treated with recombinant huma n growth hormone, while the implants on the opposite femur served as c ontrols. After 6 weeks, the implants and surrounding tissues were diss ected and evaluated histomorphologically and morphometrically by light microscopy. The bone ingrowth and the bone contact in the grooves wer e quantified by digital image analysis. Calcium phosphate coating at t he bottom of the grooves resulted in a significant increase of bone in growth and bone contact. Small grooves had significantly more bone ing rowth and bone contact than the larger grooves. However, all implants impregnated with growth hormone showed inhibition of bone contact and bone ingrowth. We conclude that recombinant human growth hormone inhib its bone formation in the grooves coated with calcium phosphate. Witho ut the addition of growth hormone, the calcium phosphate coatings impr oved bone ingrowth and bone contact in the grooves. Further studies ar e required to determine whether growth hormone could also possibly act as a bone growth promoting factor in these implants. (C) 1998 Publish ed by Elsevier Science Ltd. All rights reserved.