Biological evaluation of collagen gels containing calcium hydroxide and hydroxyapatite

Dentinal chips and different biocompatible materials have been used in the past as apical plugs to enhance healing and simplify obturation. The purpose of this study was to evaluate bone reactions to implants of hydroxyapatite, collagen, and calcium hydroxide, alone or in different combinations. The materials were implanted bilaterally in the mandibles of 36 guinea pigs and the reactions were compared histologically over a period of 16 wk. No major inflammatory reactions were observed in any of the implant combinations. Hydroxyapatite was not resorbed over the examination periods, but calcium hydroxide and collagen implants were partially or totally resorbed and replaced by bony tissue. The results indicate that cylinders which may be useful as apical plugs can be performed and will heal with minimal biological reactions.