Effects of hyperbaric oxygen treatment on bone healing. An experimental study in the rat mandible and the rabbit...

This study was undertaken in order to investigate some of the factors important for bone healing. A simple and reproducible experimental model was developed for study of tissue reactions following mandibular osteotomy in the rat. Osteotomies were performed proximal to the entry of the inferior alveolar artery, alone or combined with different degrees of mucoperiosteal reflections. The maximal damage that was seen 10 days after surgery was bone resorption in the central portion of the mandibular corpus. The incisors were found to be more sensitive to vascular disturbancies than the molars. The tissue changes were most pronounced when the osteotomies were combined with mucoperiosteal reflections. In order to test different ways of reducing the damage induced and to initiate reparative events by altering local circulatory and metabolic parameters, hyperbaric oxygen (HBO), heparin, or dextran treatments were utilized. The HBO animals were placed in a pressure chamber and subjected to 2.8 ATA HBO, for 2 hours daily. The heparin was administered subcutaneously and dextran by i.v. infusion. Heparin treatment reduced morphologically determined tissue damage in the incisor pulp, odontoblasts and enamel organ. Dextrans had no ameliorative effects. HBO treatment reduced tissue damage in a manner similar to heparin, and also induced reparative events, such as osteodentin formation in pulps and early chondroid reactions in bone. The vascular bed (86Rb) and blood flow [( 125I]polyvinylpyrrolidone) in the mandible were determined at 10 and 30 days after surgery in animals with and without treatment with HBO. The operated right side was compared to the unoperated left side with respect to these two parameters. In HBO treated animals no difference could be seen between the operated and unoperated sides, whereas both a reduced blood flow and diminished vascular bed were seen in the operated side of the mandible in HBO-untreated animals. Alkaline phosphatase in serum (S-ALP) is considered to reflect the spillover of different isoenzymes from different tissues, and the activity of S-ALP is known to vary because of disease in the tissue from which it is derived. S-ALP was characterized biochemically. Separation and measurement of S-ALP isoenzymes was done using isoelectric focusing and optical densitometry. The S-ALP levels were determined before and after mandibular osteotomy and were compared in tissues of animals treated with HBO. A marked decrease in S-ALP was seen after osteotomy. HBO treatment, on the other hand, inhibited this S-ALP decrease, paralleling a reduced tissue damage in the mandible.(ABSTRACT TRUNCATED AT 400 WORDS)