BONE HEALING FOLLOWING THE USE OF HYDROXYAPATITE OR IONOMERIC BONE SUBSTITUTES ALONE OR COMBINED WITH A GUIDED BONE REGENERATION TECHNIQUE - AN ANIMAL STUDY

The healing of standardized bone defects grafted with either particula te ionomeric or hydroxyapatite bone substitutes was compared in the ma ndibular ramus of 30 Sprague-Dawley rats. The possible additional resp onse achieved when combining these materials with a guided bone regene ration (GBR) technique was also evaluated. Three groups of 10 animals received either no implant material or ionomeric or hydroxyapatite bon e substitute in defects in the right ramus. The left mandibular defect s received the same treatment, except that the operation site was cove red by a membrane (GBR technique). Half of the animals were sacrificed at 4 and 10 weeks following surgery, and the inflammatory response at the implant site and the amount of new bone formed in the defects wer e determined histomorphometrically. Defects implanted with ionomeric b one substitute exhibited more bone formation (4 weeks = 3.19 +/- 0.38 mm(2), 10 weeks = 5.35 +/- 0.26 mm(2)) than both defects that received no treatment (4 weeks = 0.88 +/- 0.35 mm(2), 10 weeks = 2.1 +/- 0.49 mm(2)), membrane alone (4 weeks = 1.21 +/- 0.05 mm(2)) or hydroxyapati te bone substitute (4 weeks = 1.41 +/- 0.46 mm(2), 10 weeks = 3.34 +/- 0.41 mm(2)) at 4 weeks (P less than or equal to .01) and at 10 weeks (P less than or equal to .05). The use of a GBR technique did not incr ease the amount of bone formed, compared to the use of bone substitute s alone. Hydroxyapatite and ionomeric bone substitutes used alone were more effective in inducing repair of the defects than was GBR membran e alone. The use of hydroxyapatite was associated with a greater infla mmatory reaction (P less than or equal to .01) than was ionomer in thi s model.