Calcium hydroxide has been used successfully as a dressing over exposed dental pulps and after pulp amputations to promote the formation of a dentin bridge in the teeth of humans, dogs, and rats.' A good deal of clinical and experimental evidence has accumulated to show that this material causes the formation of a dentin roof or bridge over the denuded pulp more quickly than do most other substances.2 3 In spite of extensive studies, it is not yet clear whether the rapidity of the bridging is due to its acidneutralizing action, to the calcium ion, or even to its coagulating powers. Zander4' 5 believes that calcium diffuses from the calcium hydroxide dressing into the pulp and enters into the formation of the new dentin roof. Others suggest that the calcium necessary for the calcification of the new dentin is derived via the vascular supply from the pulp, since good dentin bridging can be observed under dressings which do not contain calcium.2The purpose of this study was to determine whether the calcium from the calcium hydroxide dressing entered into the formation of the new dentin roof. Radioactive calcium was used to trace whether a diffusion of calcium ions occurs from the calcium hydroxide placed over amputated pulps into the dentin bridge or pulp of dogs' teeth. MATERIALS AND METHODSForty-two teeth in two dogs were prepared for this experiment. Both dogs were wellnourished males, approximately 2 years old and weighing about 7 kg. Their condition remained good throughout the duration of the experiment.The animals were anesthetized with sodium pentobarbital injected intraperitoneally at 30 mg/kg. The teeth and gingivae were swabbed with a 5 per cent solution of iodine in alcohol. Cavities were prepared on the buccal surfaces of the canine and molar teeth approximately 1.0 mm. above the free gingival margin, using tungsten carbide burs revolving at 3,000 rpm. Drilling was stopped at the first appearance of blood following penetration of the pulp. As a rule, bleeding stopped of its own accord. When it continued for any length of time, it was controlled by application of a saturated solution of calcium hydroxide in distilled water. The exposed pulp was then covered with a paste of calcium hydroxide (pH 10.5-12.5) containing 120 microcuries of radioactive calcium (Ca45C12) per gram of calcium hydroxide powder. Each dressing was then covered with a zinc oxide-eugenol cement, care being taken to avoid pressure on the pulp.Three teeth were treated each week in each dog for 6 weeks. The dogs were sacrificed by an intravenous injection of air into the femoral vein, 2 weeks after the last treatment, so that a total of 6 teeth was available for histologic study after intervals of 2, 3, 4, 5, 6, 7, and 8 weeks after pulp capping. The jaws were separated from the skull and 1128
A study was undertaken to find a standard method that would be relatively reproducible and would visualize the vascular changes in hard and soft tissues that accompany pathologic changes. Each tooth and its surroundings were found to have a complex vascular network that is directed to its particular function. Also each network is closely connected with other vascular networks; they form a complex blood supply source which, when necessary, can easily provide a compensatory blood supply.Most pathologic changes in both hard and soft tissues are accompanied by changes in blood supply. It seemed useful to find a standard method that would provide a relatively reproducible way to visualize such vascular changes.Addison and Appleton' observed that rats' teeth have a rich blood supply. Gulat2 described, in part, the vascularization of the rat incisor. Kindlova and Matena3,4 obtained better details by injecting the blood vessels of rats with colored latex, and emphasized especially the vessels of the incisor. Kindlova5 6 and Egelberg7 found in the coronal gingiva facing molars, capillary loops that differed from those in the gingiva facing the oral cavity. Adams8 described the vascularization of the enamel organ of the incisor only. Cutright and Bhaskar,9 by use of silicone rubber perfusion, found communicating vessels between the lower lip and periodontium in the lower incisor region in monkeys. Saunders'0 suggested there was a close relationship between gingival periodontal and pulpal circulation at the apical region. Kindloval" also found that the network facing the epithelial attachment develops independently from the periodontal or gingival vessels, and that a circular vessel
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