Herbert Schilder

Effects of moisture content and endodontic treatment on some mechanical properties of human dentin

The objective of this study was to determine whether significant differences exist between the mechanical properties of human dentin from treated pulpless teeth and dentin from normal vital teeth. Dentin specimens (n = 262) were obtained from 54 freshly extracted normal vital human teeth and 24 treated human pulpless teeth. These specimens were subjected to different experimental conditions (wet, air dried, desiccated, and rehydrated). Compression, indirect tensile, and impact tests were conducted to measure the mechanical properties of those specimens. All data obtained were analyzed with t tests. The results showed that the dehydration of dentin increases the Youngs modulus, proportional limit (in compression), and especially the ultimate strength (in both compression and tension). Substantial dehydration changes the fracture characteristics of dentin specimens under static compressive and indirect tensile loadings. The measurements of impact-breaking energies of desiccated dentin were not found to be significantly decreased. The compressive and tensile strengths of dentin from treated pulpless teeth obtained in this study do not appear to be significantly different from those of normal dentin (p > 0.05), while the mean values of Youngs modulus and proportional limit in compression tests appear to be lower. Fifty percent of the dentin specimens from treated pulpless teeth exhibit greater plastic deformation than normal dentin in compression. The results of this study do not support the theory that dehydration after endodontic treatment per se weakens dentin structure in terms of compressive and tensile strengths. Other mechanical properties of treated pulpless teeth, however, may not be the same as those of normal vital teeth.

Endotoxin Content in Endodontically Involved Teeth

Fluid was aspirated from the root canals of 40 endodontically involved teeth. This fluid was assayed for endotoxin with the limulus lysate test. Pulpless teeth contained greater concentrations of endotoxin than those with vital pulps. Symptomatic teeth also contained more endotoxin than asymptomatic teeth.

Effectiveness of Various Medications on Postoperative Pain following Complete Instrumentation

The root canals of 588 consecutive nonsurgical patients with varying levels of pain were completely instrumented in 10 endodontic practices and 4 endodontic graduate programs. The participants were sequentially assigned to one of nine medications and a placebo. The severity of pain was assessed by the visual analog scale for 72 h following instrumentation. Among all of the parameters studied, three factors (preoperative pain, apprehension, and types of medication) were found to be significant in determining postinstrumentation pain. An association was found between the intensity of pre-and postoperative pain. As the intensity of preoperative pain increased, the chances for more severe postoperative pain increased (p < 0.0001). In addition, an association between the presence of apprehension before any treatment and postoperative pain was also noted (between 0.012 < p < 0.047). Examination of the time-effect curves for various medications in patients with no mild pain showed no statistical significant difference between the effectiveness of different medications and placebo. However, a multiple comparison of the effectiveness of various medications and placebo on patients in moderate and severe preoperative pain showed that ibuprofen, ketoprofen, erythromycin base, penicillin, and methylprednisolone plus penicillin were more effective than placebo within the first 48 h following complete instrumentation.

The thermomechanical properties of gutta-percha

Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, Dept. of Endodontics, 1973.

The thermomechanical properties of gutta-percha: II. The history and molecular chemistry of gutta-percha☆

Abstract The various early uses of gutta-percha are reviewed, and its molecular chemistry is discussed.

The thermomechanical properties of gutta-percha. Part V. Volume changes in bulk gutta-percha as a function of temperature and its relationship to molecular phase tranformation

A variety of gutta-percha materials was subjected to dilatometric analysis to measure volume changes which take place with heating and cooling. The volume changes were found to be related directly to the molecular transformation kinetics of the polymer material and to the temperature ranges within which they take place. If the gutta-percha in the apical segment is not elevated above 45 degrees C, molecular transformation is avoided and the ultimate volume changes which accompany temperature cycling are small, predictable, and controllable.

A histological evaluation of the human pulp in teeth with varying degrees of periodontal disease

Careful periodontal documentation and subsequent histological examination of 46 human teeth with varying degrees of periodontal involvement showed that their pulps remained within normal limits regardless of the severity of the periodontal disease. Furthermore, it was observed that very deep caries or extensive coronal restorations were associated with pulpal changes regardless of the degree of periodontal involvement. On the basis of the teeth examined in this study, no correlations could be made between the presence or severity of periodontal disease and pulpal changes.

The thermomechanical properties of gutta-percha. Part IV. A thermal profile of the warm gutta-percha packing procedure

A thermal profile of the warm gutta-percha technique was produced by the thermocouple instrumentation of natural teeth and the subsequent monitoring of intraradicular temperature changes during the packing procedure. Although variations in thermal patterns resulted from individual differences in timing and instrumentation, certain clinically accepted patterns of activity produced consistent, representative temperature ranges to which the gutta-percha in the body of the canal was 80 degrees C., while the over-all peak temperature recorded in the apical region was 45 degrees C. Thermal penetration of the gutta-percha was expectedly limited, with significant thermal effects rarely exhibited more than 4 to 6 mm. into the material.

An evaluation of EDTA in endodontics

Abstract The purpose of this investigation was to determine the chemical self-limiting property of the chelating agent, EDTA, by a gravimetric method. It was shown that a determinable quantity of dentin can be chelated by a known quantity of EDTA. It was also found that an excess of EDTA will react with 73 per cent of the available inorganic dentin in vitro. In two different approaches, a proportionate amount of inorganic matter was chelated. Buffering the solution had no effect on the dentin sample.

Physical properties of gutta-percha when subjected to heat and vertical condensation

Abstract Vertical condensation of warm gutta-percha is a relatively new technique in the endodontic therapeutic regimen. The physical properties of gutta-percha when used in this manner have been evaluated. Part I is concerned with the determination of the distance to which the mass of gutta-percha will conduct heat ahead of heat application and vertical condensation. Part II deals with the evaluation of volume stability of gutta-percha when used in a repeated sequence of heating and vertically condensing the material. Results showed that the temperatures recorded vary from a 12.5° C. increase in the gutta-percha in the body of the preparation to a 4.0° C. increase at the apex at the time condensation is completed. The volume of gutta-percha recovered from the preparations was significantly greater than the volume of the preparations.