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The antimicrobial effect of the root canal filling material N2 has been studied in vitro. Pulverized as well as intact set N2 inhibited the growth of the mixed bacterial flora of saliva or pure cultures of S. mutants and A. viscosus on blood agar for at least 100 days. Intact set N2 transferred daily to blood agar inoculated with saliva lost its antimicrobial activity after nine transfers. The antimicrobial effect of N2 against S. mutants was found to be bactericidal. N2 also appeared to possess an antimicrobial "vapor effect".

Calcium hydroxide, in its various forms, has become the preferred agent of most practitioners who perform pulp capping. The application of calcium hydroxide to the pulp stimulates the growth of new dentin and protects the pulp from subsequent irritation. However, the new dentin generated by the pulp may, in turn, infringe on the pulp. If the thickness of the pulp tissue is large, this infringement will not be significant. If the volume of pulp tissue is shallow, the same amount of infringement may cause sufficient impairment of circulation to the cornal area of the pulp, leading to an area of the necrosis may then contaminate the entire pulp, and root canal therapy will become necessary. Therefore, pulpal amputation is the preferred treatment in such situations.

The sealing efficacy of temporary endodontic filling materials was tested in vivo. The following materials were studied: Cavit, Caviton, gutta-percha, three types of zinc phosphate cement, and zinc oxide and eugenol. All the materials were tested in the access cavity of the same anterior tooth in ten different patients for a minimum of 1 week. Seepage was determined bacteriologically by culturing a cotton pellet which was sealed into the access cavity. On the basis of the quantity of microorganisms grown anaerobically, differentiation was made between no leakage, minor leakage, and gross leakage. Findings with Cavit and Caviton are essentially the same and show no or minor leakage in the vast majority of tests. Gutta-percha showed gross leakage in six out of eight tests. Phosphate cements showed no leakage in more than two thirds of the tests.

The systemic administration of methotrexate in nonlethal doses impairs the ability of the laboratory rat to localize an inflammatory response to operative dental procedures that result in exposures within the pulpal tissue. The pulpal healing response within these animals is thus greatly compromised.

Thirty-six 56-day-old male Sprague-Dawley albino rats served as two groups of experimental animals. Group 1 was irradiated with 400 rads delivered as total-body radiation from a cesium source. Group 2 served as the control group and was not irradiated. Three weeks later, the dental microscope was used to facilitate various dental procedures in both groups of animals (cavity preparation filled with zinc oxide-eugenol, pulp exposure capped with zinc oxide-eugenol, and pulp exposure left open). Two animals for each procedure from Groups 1 and 2 were killed at time intervals of 2, 4, and 8 weeks. The results showed that (1) radiation at this dose resulted in a depression of the normal response of the dental pulp to the trauma and infection induced by pulpal exposure, (2) there were no pathologic changes in the untreated molars of the irradiated animals, and (3) the use of the dental microscope greatly facilitated cavity preparation in the molars of rats.

Forty adult male Sprague-Dawley rats were divided into two equal groups, control (Group 1) and experimental (Group 2). Group 2 received 100 mg of dl-alpha-tocopherol acetate (vitamin E) twice weekly by the oral route. After 2 weeks the animals in both groups were subjected to pulp exposures that were capped with zinc oxide and eugenol and to pulp exposures that were left open. The oral administration of 100 mg dl-alpha-tocopherol acetate in the Group 2 animals was continued for periods of 1 day to 4 weeks after the operative procedures. The animals were killed 1 day, 3 days, and 1, 2, and 4 weeks after the procedures. The most severe, prolonged, and extensive pulpal disease was seen in both groups when the pulp exposure was left open to the oral flora. The most favorable repair and healing results took place after 1, 2, and 4 weeks in the Group 2 animals in pulp exposures covered with zinc oxide and eugenol.