Stimulation of early bone formation by the combination of an osteopromotive membrane technique and hyperbaric oxygen.

Large bone defects often heal incompletely as a result of ingrowth of connective tissue. By using a mechanical hindrance, a porous expanded polytetrafluoroethylene (e-PTFE) membrane, it is possible to prevent fibroblasts and other soft connective tissue cells from entering the defect, thereby allowing osteogenesis to occur unhindered. As evidenced in several investigations, this osteopromotive membrane technique causes a strongly improved bone regeneration of well defined osseous lesions. Hyperbaric oxygen treatment has also been shown to accelerate bone healing. In this study the value of combining the two techniques was investigated. Through-and-through bone defects, 5 mm in diameter, were produced unilaterally in the angular region of the mandibles of adult rats (n = 60); the defects in half the number of animals were covered lingually and buccally with membranes. The animals were then divided into four groups: treatment with membrane alone, treatment with hyperbaric oxygen alone, combined treatment, and no treatment. Histological examination of the defects after 14 days showed that the combination of techniques had resulted in significant improvement in bone healing, compared with hyperbaric oxygen or the membrane technique alone. Synergistic effects can thus be achieved by the use of membranes and stimulatory factors for bone regeneration.

Studies in oral galvanism: mercury and copper levels in urine, blood and saliva in submerged electrically cutting divers.

The aim of the study was to analyse the concentration levels of mercury and copper in urine, blood/blood plasma and saliva in relation to intra-oral electrical activity. Five Swedish Navy divers took part in the study in order to determine whether working submerged with electrical cutting equipment produced changes in the presence and level of oral galvanism and whether this posed a serious occupational health risk. The investigation concluded that the risk of seriously increased intra-oral electrical activity during welding or cutting activities was small. Development of the study is suggested, with long-term sampling of urine and blood samples of divers supported.

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.

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.

Evaluation of oral problems in divers performing electrical welding and cutting under water.

A study of 118 professional commercial divers, using an inquiry form, revealed that 55% of the divers complained about a metallic taste in the mouth when working with electrical equipment under water. A nationwide clinical examination of 40 divers was performed to see if the metallic taste during work reflected any alteration in the oral cavity. The clinical appearance of the dental amalgam restorations differed significantly between divers who had been working with electrical equipment and divers who had not. A number of other dental indexes were assessed and showed no differences between the two groups. These included salivary secretion rate, buffering capacity, secondary caries, plaque index, bleeding index, and cultures of S. mutans and Lactobacillus. Relatively high levels of the two organisms were noted, indicating that the group of divers examined should be considered as a caries risk groups.

Studies on protracted tissue reactions and repair after circulatory and skeletal damage to the rat mandible.

The effect of circulatory and skeletal damage to the distal part of the mandible was studied on young growing rats after interruption of the inferior alveolar artery. The central part of the mandible including the incisor was most vulnerable to circulatory trauma. Maximal damage was seen when the inferior alveolar artery was interrupted combined with bilateral reflection of the mandibular periosteum. The damage produced then was a necrosis of the incisor pulp, odontoblasts and enamel organ and extensive resorption of the centrally-located compact bone. When both sides of the mucoperiosteum remained intact, damage to the main vessels of the mandible did not produce total necrosis of the incisor pulp. Reparative events with production of a fibrous connective tissue of the pulp and osteodentin production were seen. After resorption of sequestered bone was finished, this was replaced by a cell-rich type of bone which also replaced the alveola of those animals which had had their incisors excised. Hypercementosis was seen in the molars after 1 year. No respiratory activity in the incisor pulps was seen after the circulatory damage.

Early tissue reactions after circulatory and skeletal damage to the mandible of the rat.

Skeletal and circulatory damage in the form of a fracture of the mandible, proximal to the entry of the inferior alveolar artery and other perforantes, alone or combined with unilateral or bilateral mucoperiosteal extirpation, was inflicted on growing young rats. A morphological study of the tissue changes in the bone, dental tissues and soft tissues was performed. Cutting of the nutrient vessels together with extirpation of the periosteum was followed after 10 days by extensive infarction of the incisor pulp, the odontoblasts and the apical part of the enamel organ. The bone was damaged centrally in the mandibular corpus and at the lower border of the ramus, and was partly resorbed during the experimental period. The periodontium showed dilated vessels, but was not damaged. The pulps of the three molars showed numerous dilated vessels but were otherwise not damaged. The oral mucosa, bone marrow, peripheral nerve tissue and peripherally situated bone were not altered. In the animals after fracture alone, oedema of the incisor pulp was present, but infarction did not occur with certainty. A similar bone damage as with mucoperiosteal extirpation was present. The incisor with its dentin and enamel-forming cells was most sensitive to circulatory disturbances due to its central location, while the gingivoperiodontal, mucoperiosteal and midline circulatory systems could nourish the peripheral parts of the mandible. The dependence of the different nutrient systems to bone and dental tissues is discussed.

Optical properties of damaged and undamaged muscle tissue studied in high-energy missile wounds.

Modern surgical treatment of wounds caused by high-energy traumata includes the excision of all non-viable muscle tissue. To judge the transition zone between viable and non-viable tissue correctly, however, it takes a highly qualified surgeon, experienced in high-energy trauma surgery. Less skilled surgeons are tending to leave some non-viable tissue behind in the wound, which often leads to infection and re-operation and causes, among other things, extended suffering and hospitalization for the patient. Among the visible and palpable properties serving as criteria for the surgeon is that the non-viable tissue is dark purple, whereas the viable tissue is of lighter red colours. The perception of colour is depending on the optical properties of a surface and on the composition of the light illuminating it. A pilot study has shown that the colour contrast between viable and non-viable muscle tissue can be enhanced by using colour filters. In this investigation optical properties for muscle tissue in different degrees of viability have been scrutinized. It seems to be possible to find a clinically applicable method to help the surgeon in his work.

Proteoglycan clearance in rat femoral cartilage exposed to 6 aTa.

Sprague-Dawley rats were exposed to air at 6 ATA. The decompression time was varied from 30 s to 6 h, resulting in a total pressure time interval from 0--24 h. The amount of rat femoral cartilage proteoglycans was determined by measuring the uronic acid content of the cartilage after papain digestion. The amount of proteoglycans decreased linearly with time of total pressure (decompression time included). No correlation with decompression time was found. It is discussed whether the clearance of proteoglycans is because of a decreased cellular synthesis, assuming the chondrocytes maintain an unchanged degradation activity, or because of an enhanced extracellular transport facilitated by the high pressure.

Effects of local anesthetics on aerobic and anaerobic metabolism of the dental pulp.

Pulps from rat incisor have been dissected out and the respiratory activity in the tissues has been measured in a Gilson respirometer (modified Warburg technique). Local anesthetics lidocain (xylocain) and prilocain (citanest) in concentrations 2.5%, 5%, and 10% have been added to the medium. Effects on the membrane permeability i.e. on the potassium-sodium pump has been studied using incubation at 37 degrees C in 24NaCl. The influx of 24Na has been registered in a scintillation counter. The anaerobic respiratory activity has been studied determining lactate dehydrogenase activity with a spectrophotometric technique. The results show that the concentrations of local anesthetics in the medium of 5% and 10% caused a significantly lower respiratory activity of the cells in the dental pulp. This was not the case in the concentration 2.5%. The isotope studies show a decreased uptake in all concentrations indicating a depression of the potassium-sodium pump activity. The lactate dehydrogenase activity was significantly lower in all concentrations of local anesthetics.

Comparison of the visible spectrum of reflected light from muscle tissue in rats breathing varying amounts of oxygen in nitrogen or perfused with saline.

One of the most important problems in the treatment of injuries caused by high velocity missiles is to find the borderline between viable and non-viable muscle tissue. Technical aids using spectrophotographic principles are designed. The present investigation was performed in order to study the absorption of incident light in muscle tissue spectrographically and to compare vital muscle tissue supplied with blood of varying degrees of oxygen saturation in rats. Transmission of light through transparencies was analysed spectrographically. Transmission of muscle tissue without blood is responsible for approximately 60% of the total transmission. Rats breathing 100% oxygen differ in transmission significantly from the control group (breathing air) within the wavelength region of 430--570 nm. Rats breathing 10% oxygen show no significant difference to the control group.

Testicular blood flow and plasma testosterone concentrations in anesthetized rats previously exposed to air at 6 ATA.

Testicular blood flow and peripheral testosterone levels were measured in sodium pentobarbitone anesthetized adult rats within 3 h of exposure to air at 6 ATA for 24 h. The animals appeared clinically healthy and showed no signs of dehydration. The treated rats showed a small but significant reduction in arterial blood pressure, and blood flow to the testis, epididymis, ventral prostate, and kidneys was also reduced. Calculations of regional vascular resistance revealed a vasoconstriction in all organs studied. The plasma testosterone concentrations were also significantly reduced after hyperbaric exposure. It is suggested that this may be due partly to the reduction in testicular perfusion.

Effects of local anesthetics on the respiratory activity in vitro of cells in the dental pulp.

The respiratory activity of isolated dental pulps from rat incisors was studied using a Gilson respirometer. The activity was compared with activities after administration of varying concentrations of commercial standard solutions of lidocaine with and without adrenaline and prilocaine with felypressin. Above a 2.5% concentration of the standard solution added to the respiratory medium a significant inhibition was registered.

Leucine and fucose incorporation into odontoblast protein.

Odontoblasts isolated from rat incisors were incubated in vitro in the presence of tritiated leucine or fucose, and the amount of precursor incorporated into TCA-recipitated proteins was determined. The effect on precursor incorporation of varying the total precursor concentration was examined. The incorporation of leucine and fucose into TCA-precipitated proteins was found to be linear with time for at least 90 min. Inhibition studies with puromycin, cycloheximide and chloramphenicol demonstrated the presence of odontoblastic protein synthesis. One hour after in vivo administration of triated leucine the highest specific activity of odontoblast-predentin protein material was noted the corresponding maximum for pulp proteins was found to occur after 30 min. The in vivo incorporation of triated fucose was maximal after 4 h in both odontoblasts and pulp tissue.

On the regeneration of cartilage after x-irradiation. A study on rabbits ears.

The present investigation demonstrates cartilage healing in experimental defects in rabbits ears. The authors confirm the importance of the presence of the perichondrium. Ears X-irradiated with disages of 2 000-4 000 R show a reduced healing capacity as compared with control ears.