[Experimental studies of direct pulp capping in permanent teeth with incompletely formed apices]

In permanent teeth described as having incompleted roots, dentin is still in the process of deposition on internal dentin walls and the root is in the process of completion. The purpose of this study of dog's immature permanent teeth was to investigate pulp healing and continuous root and internal dentin-wall developments after direct pulp capping with two types of calcium hydroxide paste on mechanically exposed pulp. Material and methods In this study, 148 vital permanent premolars with incompletely formed apices were obtained from 26 dogs (6 months old). The animals were generally anesthetized with 5% sodium pentobarbital, and a cavity was prepared on the occlusal surface of each experimental tooth using an air turban handpiece with diamond bur. After the cavity preparation, the central pulp horn of each tooth was mechanically exposed with a sterile round bur (ISO No. 007, 2/0). In experimental teeth on the right side, a calcium hydroxide-iodoform paste "Calvital" was applied on the exposed pulp, in experimental teeth on the left side, the exposed pulp was capped with a hard-setting calcium hydroxide paste "Dycal". The cavities were lined with first a zinc-oxide eugenol cement and then a zinc-phosphate cement. Then the cavities were filled with silver amalgam. The dogs were sacrificed by means of sodium pentobarbital at intervals of 3, 7, 14, 28, and 56 days after direct pulp capping. Their jaws and teeth were removed, fixed with formalin, and 100 cases out of 148 teeth with bones from 20 dogs were decalcified, and embedded in celloidin. Each specimen was serially sectioned, stained with hematoxylin-eosin, thionin-picric acid and van Gieson's stain, and evaluated microscopically. In order to identify postoperative dentin formation, intravenous injections of tetracycline were administered to the remaining 6 dogs (48 teeth) at various intervals after the experimental procedure. Two dogs were sacrificed each of the experimental periods. Specimens were embedded in resin and sectioned to a thickness of 50 microns. Undecalcified ground sections were observed by contact microradiography, and tetracycline labeling was evaluated by ultraviolet light. Results and Conclusion 1. Pathological evaluations of the 2 groups "Calvital" group: 49 (98.0%) of 50 cases were evaluated as good, and 1 case (2.0%) as moderately good. "Dycal" group: 31 (62.0%) of 50 cases were evaluated as good, 15 (30.0%) as moderately good, and 4 (8.0%) as bad.(ABSTRACT TRUNCATED AT 400 WORDS)