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

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)

Characterization of phosphoglycerate mutase isoenzymes from free dissected facial processes.

To characterize the three phosphoglycerate mutase (PGM) isoenzymes present in rat facial processes (types MM, BB, and MB), their sensitivity to reagents of the sulfhydryl groups and to heat treatment has been studied. Type BB PGM was not affected by the -SH group reagents; type MB PGM was inhibited about 50%, and type MM PGM was fully inhibited. Type MB PGM showed a greater heat lability than type MM PGM. There was a developmental change from type BB PGM from the 9th embryonic day to isoenzymes MB and MM on the 15th embryonic day. Isoenzyme development was first seen in mandibular processes, followed by maxillary, lateral nasal, and medial nasal processes.

Changes in mineral content, mineral deposition and vascular supply of the mandible after osteotomy.

Circulatory and skeletal damage in the form of a vertical osteotomy of the mandible, proximal to the entry of the inferior alveolar artery and mandibular perforantes, alone or in combination with unilateral or bilateral mucoperiosteal reflections were undertaken on young growing rats. Changes in mineral content and mineral deposition in the hard tissues of the mandibles were studied using microradiography and by labelling with tetracycline and lead acetate. Microangiography was performed to evaluate changes in the vascular supply. Resorption of the compact bone was seen in the central part of the compact bone, in the lower border of the mandible and in the incisal part of the alveolar bone. There was resorption of the cementum and dentin in the molar teeth. Remodelling processes were seen in the compact bone starting from vascular channels and on the surface of the bone trabeculae, ten days after osteotomy. Microangiography revealed that there is a collateral vascular system existing across the midline via the symphysis region, via submucosal tissue, via the mucoperiosteal pedicle to the inferior border of the mandible and via the network of small vessels in the periodontal membrane. It was concluded that the circulation to the peripheral parts of the mandible could in part be kept up by a retrograde flow in the collateral systems when the main circulation had ceased.

Quantitation of blood flow in the rat mandible after vertical osteotomy.

Vertical osteotomies were performed in the mandibles of rats and combined with elevations of the buccal or bilateral mucoperiosteal pedicles. Isotope fractionation and particle distribution were used to measure blood flow in the distal and proximal segments of the mandible, the masseter muscle and the submandibular gland. Average decrease in blood flow ranged from 9-39% in the distal segment and from 8-24% in the proximal segment. Decrease in blood flow was most pronounced when bilateral mucoperiosteal pedicles were performed. Blood flow in the masseter muscle increased by 16-26% after osteotomy with mucoperiosteal elevations.

Changes of serum alkaline phosphatase following mandibular osteotomy in the rat.

Activity of alkaline phosphatase in serum (S-ALP) was characterized and compared with that of non-specific alkaline phosphatase (APase) of hard-tissue origin in the rat. The enzyme was characterized biochemically, and optimal incubation procedures were determined. S-ALP levels were determined before and after mandibular osteotomy combined with different degrees of periosteal reflections. Separation of S-ALP isoenzymes by isoelectric focusing revealed four major bands. A marked decrease of S-ALP activity was seen after osteotomy, and all isoenzymes were affected similarly. After treatment with hyperbaric oxygen, a smaller decrease in S-ALP was seen. S-ALP could be used as a marker for hard-tissue turn-over after surgical procedures.

Effects of dextrans, heparin and hyperbaric oxygen on mandibular tissue damage after osteotomy in an experimental system.

The effect of heparin, dextran 40, dextran 70 and hyperbaric oxygen (HBO) therapy to reduce tissue damage after mandibular osteotomy was tested in an experimental system. Tissue damage was recorded morphologically and blood flow and vascular bed was determined by isotope techniques. Subcutaneously administered heparin reduced morphologically determined tissue damage in the incisor odontoblastoma, pulp and ameloblastoma. Furthermore, central and peripheral bone damage was prevented by heparin. Dextrans had no preventive effect on tissue damage. HBO treatment reduced tissue damage in a similar manner to heparin but also induced reparative events as osteodentin formation in pulps and chondroid reactions in bone. Effects on blood flow and vascular bed provided a basis for a possible role for HBO and heparin treatment in tissue damage after osteotomy.

Experimental mandibular fracture: studies on bone repair and remodellation.

An experimental mandibular fracture model was developed in Sprague-Dawley rats. Healing and remodellation were studied using routine histology, microradiography and incorporation of tetracycline and lead acetate. Bone healing after fracture started by outgrowth of bone trabeculae from the periosteum and from marrow spaces in the mandibular corpus and coronoid process. Stabile fracture healing was seen after 14-16 days, which correlated to the time when bone trabeculae were seen to cross the fracture diastasis morphologically. Formation of reparative bone was produced by direct formation of bone trabeculae but also via formation of a chondroid tissue which was later resorbed and replaced by bone.

Experimental mandibular fracture: effect on bone circulation and metabolism after treatment with anticoagulants.

An experimental model was designed for the study of mandibular fracture healing in Sprague-Dawley rats. Healing and remodellation were studied by routine histology and the vascular supply of the mandible by micro-angiography. The blood supply to the body of the mandible was similar to that seen in long bones. The arterial vascular system appeared to be intimately involved with the formation of bone. The vessel configuration varied in relation to the progress of healing. The effect of heparin, dextran 40 and dextran 70 therapy to increase blood flow in the fracture region was tested. Dextrans had no effect on fracture healing whereas heparin induced an increased chondroid reaction in the callus. Serum alkaline phosphatase was measured as a marker for hard-tissue formation. The enzyme activity was reduced after fracture with a minimum activity three days after fracture.