Michael A. Heuer

Composition and physical properties of gutta-percha endodontic filling materials

Gutta-percha has been the predominant root canal filling material for over a century. It has been used in various filling techniques and its effect on biologic tissues has been studied; however, knowledge of its chemical and mechanical properties has grown little since its introduction into dentistry. In this investigation, the mechanical properties of five brands of gutta-percha endodontic filling materials were determined, and their chemical compositions were compared. Significant correlations were found to exist between some of these parameters.

Forces and efficacy in endodontic irrigation systems

Measurements of the pressure necessary to activate three commercially available types of endodontic irrigation systems were obtained from an in vitro testing procedure. In addition, the irrigation process was observed in simulated 1 mm. diameter root canals prepared in clear acrylic. Except for one patented system, the force necessary to depress the plunger of an irrigation syringe was found to increase as the size of the needle decreased. the most effective irrigation was observed when the larger needles of a blunted, open-end design were inserted to the full length of the preparation.

Cutting efficiency of endodontic instruments. Part III. Comparison of sonic and ultrasonic instrument systems.

The cutting efficiency of two ultrasonic and two sonic instrumentation devices were compared for their ability to enlarge and prepare standardized models of artificial root canals composed of epoxy resin. Five groups of instruments, sizes 15 to 35, were used sequentially to prepare straight and curved artificial canals by a circumferential filling motion. Ten straight, and 10 curved artificial canals were instrumented for a period of 1.5 min, with each size instrument under constant irrigation at a rate of 20 ml per min. Cutting efficiency was evaluated in terms of the mean weight loss of the specimens following serial preparation for each of the systems tested. Statistical analysis of the data indicated that significant differences in cutting efficiency existed between the groups at α=0.01 level.

Torsional failure of endodontic files

The effects of some hitherto ignored clinical variables on the torsional properties of endodontic files were determined. Torsional tests and scanning electron microscope examination revealed that endodontic files twisted in a counterclockwise manner were extremely brittle in comparison to those twisted in a clockwise manner. This phenomenon represents a potential contributor to the clinical fracture of these instruments. Additional tests showed that endodontic bead sterilization at 425 F has no apparent effect on torsional strength and ductility and that these endodontic files do not exhibit strain-rate sensitivity.

Biological and physical properties of an experimentalroot canal sealer without eugenol

Abstract The working time, setting time, set hardness, setting pH, sealing potential, and biocompatibility of an experimental root canal sealer without eugenol were compared with those of two other root canal sealers that contain eugenol. The working and setting times for the sealer without eugenol were longer than those for the sealers with eugenol at 25 C. The setting times for all sealers were similar at approximately 37 C. Set hardness, pH, and sealing ability were similar for all the sealers tested. At less than 96 hours, the sealer without eugenol was more tissue-compatible than the sealers containing eugenol. After six months, the biocompatibility of all the sealers tested was similar.

In vivo autoradiographic study of relative penetrating abilities ofaqueous 2% parachlorophenol and camphorated 35% parachlorophenol

The in vivo diffusibility of camphorated 35% parachlorophenol (PCP) and aqueous 2 % PCP was compared by autoradiographic evaluation. Aqueous 2% PCP showed complete dentinal tubule penetration at a clinically equivalent dosage while camphorated 35% PCP was limited to a mean dentinal tubule penetration of 0.58 mm, or less than a fifth of the pulpoperiodontal distance. The results of this study substantiate the findings of a previous in vitro investigation and suggest that the use of camphorated 35% PCP be discontinued and replaced by an aqueous PCP preparation in routine endodontic therapy.

A comparative study of the wound healing of three types of flap design used in periapical surgery

The clinical and histological features of wound healing of three common types of surgical flap designs used in periapical surgery were evaluated. A semilunar incision of alveolar mucosa, a submarginal incision of attached gingiva, and an intrasulcular incision of the attachment apparatus and papillae of the teeth were performed on beagles and observed at intervals of up to 60 days. Inflammatory changes persisted longer in the semilunar and intrasulcular incisions and retarded healing of the wound. Loss of alveolar bone occurred with the intrasulcular incision. Visible scarring occurred in the submarginal and semilunar incisions.

A comparative study of tooth apexification in the dog

Calcium hydroxide, collagen-calcium phosphate gel, and blood clot were compared as inducers of periapical calcification in the immature nonvital teeth of dogs. This investigation showed that calcium hydroxide accelerated hard tissue bridging of the open apex irrespective of complete resolution of initially induced inflammatory state. Collagen-calcium phosphate gel inhibited the reparative process of the initial inflammatory lesion leading to extensive destruction of the periapical tissues with no evidence of apexification. Locally induced blood clot maintained the initial inflammatory state and did not result in hard tissue bridging of the open apex. The investigation confrmed the use of the dog as an effective animal model for meeting the criteria of the experimental design.

Quantitative evaluation of the immunocompetence of the dental pulp

Human dental pulps were assayed for the presence of immunoglobulins IgG, IgA, IgM, C3 fraction of complement, and albumin by immunodiffusion. Mean concentrations of IgG and IgA were shown to be greater in the samples of inflamed tissue than in the samples of noninflamed tissue, which indicated the presence of an immune response in inflamed pulpal tissue with the possibility of the localized synthesis of immunoglobulins. The pooling technique used in this study does have weaknesses. Because of the size of the dental pulp, investigation of individual samples is impractical. This would eliminate the possibility of reporting ranges in protein concentration. Another possible factor that influences quantitation is the potential of tissue-fixed antibodies that remain in the cellular debris after centrifugation; this could mean that the actual concentrations of immunoproteins may have been higher than observed.

Natural modifiers of the inflammatory process in the human dental pulp

Concentrations of the protease inhibitors alpha 1-antitrypsin and alpha 2-macroglobulin were determined in normal and inflamed human dental pulps. Carious pulpal exposure which is associated with polymorphonuclear leukocyte infiltration and release of lysosomal enzymes was chosen as the point of verifiable inflammatory activity in the pulp. Normal samples were collected from nondiseased third molar teeth treatment planned for extraction and inflamed human pulps were collected from teeth with deep carious lesions. One half of each sample was assayed for concentration of protease inhibitors by enzyme-linked immunosorbent assay and the remaining half was examined histologically to verify the clinical diagnosis and categorize the extent of the inflammatory process. alpha 1-Antitrypsin and alpha 2-macroglobulin were detected in normal and inflamed human dental pulps in the nanogram per milliliter range. Statistically significant differences were found in the concentrations of alpha 2-macroglobulin (p less than 0.01) in moderate to severe inflammation versus normal pulp categories and between mildly inflamed pulps and moderate to severely inflamed pulps (p less than 0.05). Although differences in concentrations of alpha 1-antitrypsin were seen between inflamed and normal pulps, the differences were not statistically significant. The presence of these two protease inhibitors in the human dental pulp tissue and the increase in their concentration in acute inflammation indicates that these proteins play a role in the pathogenesis of pulpal inflammatory disease.