Systemic distribution of N2 paste containing 14C paraformaldehyde following root canal therapy in dogs

Using rubber-dam isolation and an aseptic and standardized endodontic technique, root canal therapy was performed on the right and left fourth mandibular premolars in four dogs. Each tooth was obturated with N2 paste containing 6.5 percent 14C paraformaldehyde. In each dog at 1 hour, 1, 7, 14, and 28 days, blood was drawn and biopsy specimens were taken of the adjacent lymph nodes, liver, and kidney. At 28 days, the animals were killed, and the experimental and adjacent tissues were processes for light microscopy. Histologic examination demonstrated that particles of the paste placed in the root canal were present in pulp, periapical, and periodontal tissues remote from the original site in the root canal. In addition, 14C-labeled paraformaldehyde which was contained in the N2 paste was found in blood, regional lymph nodes, kidney, and liver. The amount of radioactivity in all the body organs decreased with time.

Pulpal response to the application of phosphoric acid to dentin

Experimental cavities were prepared in forty-six clinically intact premolars of young individuals to evaluate the biologic effects of 50 per cent phosphoric acid etchant containing 7 percent zinc oxide by weight. The experimental periods ranged from 30 minutes to 150 days. The remaining dentin thickness varied from 1.8 to 3.5 mm. The teeth treated with the acid showed no more than a moderate pulpal response at the varying time periods. All of the acid-treated teeth demonstrated pulpal imflammation in the absence of clinical pain. Acid etchants should not be used on exposed or unprotected dentin surfaces.

Corticosteroids in dentistry

The application of corticosteroids to cut dentine following cavity preparation, to carious dentine in indirect pulp capping, to the exposed pulp or to pulp remnants and periapical tissues during root canal therapy has been claimed to eliminate post operative pain and inflammation. Other investigators have thrown doubt on the validity of these claims and have reported continued inflammation progressing to necrosis following such applications. This paper reports detailed clinical and histological findings in a series of over 500 teeth some of which received conventional treatment while others were treated with various corticosteroids including Mosteller's solution, tritiated prednisolone, and Ledermix paste and cement. The results confirm the fact that no clear correlation exists between symptoms and histological findings in pulp disease. The absence of pain following application of corticosteroids cannot therefore be taken as evidence of a specific therapeutic effect. In some cases pain returned after a period and histologic examination showed the slow development of inflammatory changes coupled with calcification in pulp tissue and on the walls of the canal. Further investigation is needed to clarify the relative contribution of the removal of toxic products by instrumentation and the anti-inflammatory properties of corticosteroids in the reduction of pain of pulpal origin.

A histopathologic, histobacteriologic, and radiographic study of periapical endodontic surgical specimens

Data available on 230 periapical endodontic surgical specimens were studied. It was found that bacteria occurred in the periapical tissue very infrequently. In addition, there was no correlation between the presence of acute inflammatory cells and the presence or absence of pain. Granulomas with epithelium occurred in 61 out of 230 cases, while 14 of these were cysts. Of the 110 cases with radiographic follow-up data, 67 were classified as successful, 40 were uncertain, and 3 were unsuccessful according to a modification of Strindberg's criteria, whereas 107 would have been successes according to the criteria of Bender and Seltzer and their associates. No valid biologic or clinical basis for endodontic therapy as suggested by Bhaskar was found in this material.

Methodology and criteria in the evaluation of dental implants

This study was designed to develop an inexpensive, reproducible method for studying the reaction of the tissues of the oral cavity to the endosseous implant. Thirty-six guinea pigs, three materials (Teflon, Vitallium, and Titanium 6Al-4V), two observation periods (two and 12 weeks), and two implant designs (one with exposure to the oral cavity and one without exposure to the oral cavity) were used. The inflammatory response was significantly greater in the exposed implants than in the unexposed implants. In the implants that were exposed 12 weeks, there was a strong interrelationship between severe inflammation, bacteria, and epithelial invagination. These factors are significant causes for failures of implants.