Biodegradation of four calcium phosphate ceramics;in vivo rates and tissue interactions

Abstract

To prevent exposure of artificial tooth root implants, a resorbable root implant may be developed, that in time will resorb in a vertical direction at the same rate as the alveolar ridge does after the loss of the natural teeth. Implants of four calcium phosphates: rhenanite, β-tricalcium phosphate, hydroxylapatite and magnesium-whitlockite were measured duringin vivo resorption and their interactions with the surrounding tissues at experimental periods of 6 weeks and 3 months were investigated. It was shown that a sequence of progressive resorptionin vitro does not correlate with the resorption rates found in thisin vivo experiment.In vivo hydroxylapatite was found to be less resorbable than magnesium-whitlockite and rhenanite less resorbable than β-tricalcium phosphate. Tissue interactions showed that resorption of the calcium phosphates was positively related to the number of osteoclast-like cells and did not completely correlate with the resorption measurements insofar that most rhenanite implants showed a more reactive peri-implant with the largest number of osteoclast-like cells, strongly affecting the implant surface. In contrast, two rhenanite implants showed intimate contact with bone after initial resorption. Because of this divergent reaction with rhenanite, furtherin vivo investigation on this material is proposed.