Andrew E. Michanowicz

Evaluation of an injection of thermoplasticized low-temperature gutta-percha using radioactive isotopes

The purpose of this study was to investigate the sealing properties of a low-temperature injection gutta-percha by quantitatively determining the leakage of radioactive isotopes. Sixty-three single-rooted teeth were used. C-14 starch was injected into each root canal and the leakage was determined by liquid scintillation spectrometry. All of the group tested showed very little leakage. It was shown in this study that low-temperature gutta-percha creates a good apical seal and has a promising future in endodontics.

Sealing properties of an injection-thermoplasticized low-temperature (70°C) gutta-percha: A preliminary study

The objective of this study was to investigate the sealing properties of a low-temperature gutta-percha that was injected with a new prototype pressure syringe. No compaction was necessary with the injection syringe. Sixty single-rooted teeth were biomechanically prepared for obturation. Low-temperature gutta-percha (70°C) was used with and without sealer and compared with the lateral condensation technique with sealer. The apical seal was tested for leakage with 5% methylene blue dye. Results showed that low-temperature gutta-percha creates a good seal, especially if used in conjunction with a sealer.

A pilot study of the clinical problem of regionally anesthetizing the pulp of an acutely inflamed mandibular molar

The diplomates of the American Association of Endodontists were surveyed regarding difficulties in regionally anesthetizing acutely painful mandibular molar teeth. Frequently patients developed evidence of adequate regional block anesthesia but experienced pain when the dentist attempted access. A pilot projection was undertaken to determine if a scientific basis existed for this problem. With the animal under general anesthesia, the mandibular nerve of a cat was isolated and then regionally blocked. A stimulating electrode was implanted in a cuspid tooth and a receiving electrode in the cortex of the brain. When a state of inflammation was created in the tooth in the presence of a regional block, there was an increasing cortical response to this stimulation. It was concluded that the pilot project offered a realistic technique for the study of this clinical entity.

A method of canal preparation to control apical extrusion of low-temperature thermoplasticized gutta-percha

This study evaluated an adaptation of an accepted method of root canal preparation for its ability to contain the flow of injection-molded low-temperature thermoplasticized gutta-percha. Twenty-two extracted teeth with a total of 26 canals were mounted in stone. They were radiographed with a #15 file in place to determine working length. Canals were enlarged at the working length three file sizes beyond the initial file that bound. The body of the canal was further prepared to allow placement of a 22-gauge needle within 6 mm of the working length. Integrity of the apical barrier was assessed by probing with a smaller file, and teeth with an unsatisfactory barrier were discarded. Satisfactory canals were obturated using the Hygenic Ultrafil injection system. Teeth were radiographed postoperatively, then removed from stone blocks for examination under ×25 magnification. Gutta-percha was extruded in 1 of 23 canals, as the result of a lateral canal. This method of canal preparation seems to be effective in limiting the flow of injection-molded low-temperature thermoplasticized gutta-percha.

Low-temperature (70°C) injection gutta-percha: A scanning electron microscopic investigation

The purpose of this investigation was to evaluate the adaptation of the low-temperature gutta-percha injection system (70°C) to the dentinal walls of the root canal with the scanning electron microscope. Thirty single-rooted teeth were used in this study. The teeth were filled by injection with low-temperature thermoplasticized gutta-percha with and without sealer and compared with the lateral condensation technique. Scanning electron microscopic observations of the low-temperature gutta-percha without sealer showed close adaptation to the dentinal wall, with the gutta-percha penetrating the dentinal tubules. Good adaptation but no penetration was noticed when sealer was used. Obturation was as good or better than lateral condensation with sealer.

A comparative study between injectable low-temperature (70°C) gutta-percha and silver amalgam as a retroseal

This study compared two different dental materials used in endodontic retrosealing procedures. One of these materials was a new low-temperature gutta-percha product, manufactured by the Hygenic Corporation, that involved an injection technique. The second of these materials was silver amalgam. Silver amalgam was selected because it has been recognized by many clinicians as the most effective apical sealing material. Two groups of ten recently extracted teeth were endodontically prepared with one of each of the materials being tested, and the effectiveness of these materials as sealants was determined by their ability to inhibit the penetration of methylene blue dye for a predetermined period of time through the apically sealed root tips. Preliminary results obtained indicated that, although these materials were not 100% effective in inhibiting the dye penetration, each was as effective as the other when evaluated by two observers following completion of the study as determined by its experimental design. No significant difference was exhibited between the amalgam group and the gutta-percha group. The leakage of the dye that was observed in each of the groups might have been caused by the ineffectiveness of, or the ineffective use of, the nail polish or cyanoacrylate used to coat all but the apically sealed tips of the endodonticalled prepared teeth. The function of these coating materials was to prevent penetration of the dye through the surface of the body of the root.(ABSTRACT TRUNCATED AT 250 WORDS)

Apical surgery on a two-rooted maxillary central incisor

This article presents a case of a two-rooted maxillary central incisor with previous endodontic therapy. One root canal was well filled and the other partially filled. A post was present in each root and the tooth had a crown. Surgery was performed and an amalgam retrograde filling was placed. A 6-month postoperative radiograph shows repair.

Clinical evaluation of low-temperature thermoplasticized injectable gutta-percha: a preliminary report.

An injectable thermoplasticized gutta-percha system (Ultrafil) was used to fill 50 teeth which were monitored radiographically over a period of 24 months. An equal number of teeth were filled with the lateral condensation technique and used as controls. Radiographic evidence of success was determined at a 24-month recall. The results were subjected to a 2 x 2 analysis of variance (control versus experimental/before and after treatment. There was a significant amount of repair irrespective of obturation procedure (p greater than 0.0001). Thirteen teeth in the experimental group randomly filled with sealer showed that the sealer did not influence repair.

Histopathologic study of the effect of pulpal disease upon nerve fibers of the human dental pulp

Abstract Thirty specimens of diseased human pulpal tissue were placed in either of two categories—irreversible pulpitis or necrosis—on the basis of their response to standard diagnostic tests. After being stained with a modified Bodians stain, the nerve fibers were studied microscopically and compared with nerve fibers from healthy pulpal tissue. Intact fibers with some variation from normal were observed in the specimens with irreversible pulpitis. These fibers were considered to be capable of conduction, on a morphologic basis. Dissolution of the fibers in the necrotic specimens was apparent. Only connective tissue sheaths remained. Conduction of a nerve impulse was considered impossible in these specimens.

Changes in the physical properties of the Ultrafil low-temperature (70°C) thermoplasticized gutta-percha system

Three tests were used to obtain a basic understanding of the changes taking place in the physical properties of the Hygenic Ultrafil system. The materials studied were raw gutta-percha, gutta-percha points, and the two Ultrafil materials Blue (firm set) and White (regular set) gutta-percha. In the first test a differential scanning calorimeter was used to determine melting points; two crystalline forms were observed in the dental materials and only one crystalline form in the raw gutta-percha. In the second test a magnetic bearing torsional creep apparatus was used in which the rates of crystallization were observed. The differences seen in the induction times of the crystallization are related to the amount of mastication of the gutta-percha. Mastication in this usage is the manufacturers process of mixing the raw gutta-percha with its other components. The gutta-percha is masticated slightly in the points and considerably more in the Ultrafil material. Ultrafil exhibits longer periods of time required to induce nucleation at any specific temperature due to the increased mastication. Melting points were also decreased with increased mastication. In the third test a dilatometer was used to observe isothermal volumetric shrinkage of the materials during crystallization. When the Ultrafil material was compared with the gutta-percha points, the blue material had approximately the same amount of shrinkage, 2.6%; the white material shrank slightly less, 2.2%. The raw gutta-percha being 100% polymer had the greatest amount of shrinkage, 4.6%.