Oily calcium hydroxide suspension (Osteoinductal) used as an adjunct to guided bone regeneration: an experimental study in rats

Objectives: To evaluate whether an oily calcium hydroxide suspension (OCHS) promotes bone healing when used as an adjunct to guided bone regeneration (GBR). Material and methods: Rigid, hemispherical, teflon capsules were placed with their open part facing the lateral surface of the ramus on both sides of the mandible in 10 adult Wistar rats. In each animal, one capsule was filled out with an OCHS (test) before placement, while the capsule on the other side was left empty (control). After 4 months of healing, the animals were sacrificed and histological sections containing the capsules and the neighboring soft and hard tissues were prepared. On three to four sections taken by uniformly random sampling from each specimen, the relative volumes of (1) the newly formed bone (mineralized bone and marrow), (2) the soft connective tissue, (3) the residual OCHS, and (4) the acellular (mpty) space inside the capsule were estimated by a point-counting technique, and expressed as percentage of the space originally created by the capsule. Results: There was no new bone formation inside the capsules in all but one test specimen, where only a minimal amount of newly formed bone could be observed in continuation with the lateral surface of the ramus. OCHS had a homogenous appearance and occupied the major portion (79.4%) of the space created by the capsule. No signs of active resorption of the material could be observed. On the contrary, 31.5% of the space provided by the capsule was filled out with newly formed bone in the control group. The new bone had a trabecular appearance with large marrow spaces filled with hematopoietic and fatty marrow. The rest of the capsule space in the controls appeared empty. Conclusion: OCHS may hamper bone healing when used as an adjunct to GBR.