John M. Brady

Biodegradable ceramic implants in bone. Electron and light microscopic analysis.

Abstract The main purpose of a biodegradable ceramic implant is to fill a bone space as well as to eliminate the need for a metallic implant. Although the biodegradable ceramic does stimulate bone formation and does disappear from the implanted site, it does not have the same initial strength as a metal or nondegradable ceramic implant. When completely replaced by bone, however, it should prove superior to the latter two. Additional studies comparing degradable ceramic with various other types of ceramic material and with unfilled bone defects are in progress.

Efficacy of ultrasonic cleaning.

Resin blocks containing simulated root canal spaces were compared with extracted teeth as models for measuring the efficiency of endodontic debridement with hand instrumentation, ultrasonication, or a combination of both techniques. Canal spaces were filled with radioisotope-laden gelatin, and the loss of radioactivity was measured after treatment. No significant differences in efficiency of debridement were observed in teeth prepared with hand instruments or ultrasonics alone; both techniques reduced radioactivity by between 77% and 79%. Ultrasonication after hand instrumentation was the most efficient method; it reduced radioactivity in the teeth and blocks by 88% and 92%, respectively.

Sealing Quality of a Temporary Filling Material.

Endodontic access cavities were prepared in forty extracted human teeth. The access cavities were obturated with Cavit and tested for leakage with methylene blue. The data suggested that at least a 3.5 mm. thickness of Cavit should be used in order to prevent leakage. Examination under the scanning electron microscope showed areas in which the constituents of Cavit were improperly mixed, which may lead to increased penetration.

Reaction of bone to tricalcium phosphate ceramic pellets

Abstract This study indicates that tricalcium phosphate is well accepted by the tissue and may actually contribute mineral salts for the formation of bone at the site as the ceramic is broken down into granules.

Corrosion of endodontic silver cones in humans: a scanning electron microscope and X-ray microprobe study

Analyses with the scanning electron microscope and the X-ray microprobe were performed on 13 silver cones removed from 12 patients. The cones showed changes that ranged from surface dulling to black corrosion and pitting. Sulfur and chlorine were detected at the apical end of the cones and in the biopsy specimens of periapical tissues.

Long-Term Effects of Radiation on the Vascularity of Rat Bone: Quantitative Measurements with a New Technique

Radiation-induced depression of vascularity in the humerus of 62 rats was measured at 2 and 8 months after irradiation with a 250 kVp x-ray unit. These rats were locally irradiated, and later perfused with a silicone rubber material that contained chromium-51. Marked weight loss of the humerus occurred at 8 months with all exposures above 4000 rads. Vascularity decreased in the irradiated humerus to 28% of the unirradiated bone at 4000 rads 2 months after irradiation. At 8 months after irradiation there was no recovery of vascularity at any of the doses studied (2000, 4000, 6000, 8000, and 10,000 rads). The vascular depression after irradiation appeared to consist of two components, the first comprised approximately 70% of the vasculature and was destroyed above 4000 rads. The second, approximately 30% of the vasculature, was present up to 10,000 rads and 8 months after exposure.

Corrosion of silver cones in bone: a scanning electron microscope and microprobe analysis

Sections of silver cones were implanted in tibial bone wounds in 36 Sprague-Dawley rats. Groups of six rats each were killed at monthly intervals, and the specimens were examined by scanning electron microscopy and by X-ray microanalysis. The silver cones had corroded rapidly, but they were well tolerated by the tissues. Elements of silver, chlorine, and sulfur were found in the tissues adjacent to the implants.

Postdebridement retention of endodontic reagents: A quantitative measurement with radioactive isotope

Forty freshly extracted human teeth were biomechanically prepared for endodontic obturation using a radioisotopically labeled EDTA-urea peroxide-Carbowax compound. The amount of radiolabeled mixture remaining in the canals after through cleansing was about 3.8% of that originally applied. The amount of residue did not decrease with reinstrumentation and irrigation.

Light microscopy, scanning electron microscopy, and microprobe analysis of bone response to zinc and nonzinc amalgam implants

Freshly mixed, unset zinc-free and zinc-containing analgam was implanted in the right tibia of 32 rats. Half of the specimens were examined by the light microscope and the other half by the scanning electron microscope and x-ray microprobe analysis. It was found that amalgam is well tolerated by the rat osseous tissue, and there were no histologic reaction differences between zinc and zinc free amalgam. The surfaces of the implants were covered by an organic film at 3 weeks and with bone at later intervals. Very little corrosion products containing sulfur were observed on the amalgam surface at all intervals. Bone adjacent to the amalgam contained tin and sulfur irrespective of the presence of zinc in the alloy, indicating outward migration of specific components of the alloy.

Evaluation of endodontic instruments as received from the manufacturer: the demand for quality control.

Two hundred seventy new files, reamers, and Hedström files from three different manufacturers were evaluated for debris and defects. Statistical analysis of the new instruments showed that one companys instruments were cleaner than the other two but still contained defects. A standard for quality is proposed.