[Histopathological studies on tissue reactions to experimental root canal sealer in cats]

This study was designed to elucidate whether or not the root canal sealers, newly prepared here, show high affinities and promote the osteo-cicatric healing for the remaining dental pulp and periapical regions. For these purposes, I used two types of sealers, newly devised here and mainly composed of powdered corals mixed with propyreneglycol for the experiment 1 and powdered human dentins mixed with atelocollagen implant for the experiment 2. Guttapercha points with these sealers were applied in the premolar and molar tooth mesial or distal canals of 24 adult cats, whereas in controls guttapercha points with Canals, made commercially, were used instead of these sealers. After treatment, the periapical tissues and accessory root canal regions were histopathologically observed at different intervals throughout 30 to 130 days. The results obtained were as follows: 1. When guttapercha points were penetrated beyond the apical foramen and reached periapical tissues, prolonged inflammatory reactions of a slight or medium degree were observed in all three types of sealers. 2. When Canals were applied, prolonged inflammatory reactions were persistent if the sealer flooded out. In contrast, if they were in just-filling (Type-I, as termed in text), inflammatory reactions were often detectable at the accessory root regions. Many exudative inflammatory cells around the over-tip of guttapercha points were seen, as compared around the apicals of the dental root. 3. When powdered coral was used, strong inflammatory reactions was little found. Adjunction of the new bone was usually observed in the alveolar bone. The tendency of scar formations was seen in the periapical tissues where the inflammatory reaction was assumed to have occurred. 4. When powdered human dentin was used, in any experiments, inflammatory reaction were not seen with a few exceptions. However, if inflammatory responses were existed in a few cases, their degrees were relatively strong. 5. If the debris of dentin was blocked within the root canal apex, fine examples were seen regardless of the three types of the sealers. 6. Calcium in the powdered coral showed a conspicuous peak by energy X-ray analysis. The ratio of Ca and P of powdered human dentin was 1:1. From the above findings, both powdered coral and powdered human dentin could be useful as composites of sealers.