Corrosion and cytotoxicity evaluation of thermafil endodontic obturator carriers.

The purpose of this study was to evaluate the in vitro cytotoxicity of two metallic and two plastic Thermafil carrier materials, and to separately evaluate the in vitro corrosion behavior of the two metallic carriers. Stainless-steel, Ti-6AI-4V, Polysulfone, and Vectra carriers were evaluated for cytotoxicity using the ISO-recommended agar overlay test. The two metallic carriers were additionally corrosion tested in 0.9% NaCl solution for 174 wk, at 37 degrees C. Elemental analyses of the corrosion solutions were periodically conducted using inductively coupled plasma-mass spectroscopy. Agar overlay results showed that the four carrier materials were not cytotoxic to L929 fibroblasts. Inductively coupled plasma-mass spectroscopy results showed that the metallic materials had small mass loss rates. Scanning electron microscopy showed no evidence of pitting or crevice corrosion.

Endodontic treatment outcomes: do patients perceive problems?

Patient's perceived problems related to endodontically treated teeth are an important consideration for all dental practitioners. Chronic pain or restorative problems may occur that are not reported back to the attending dentist in a timely manner and thus may not be resolved. The authors conducted a study involving a one-year follow-up of endodontically treated patients. They offer suggestions for interventions that could minimize the reported problems.

New and emerging technologies: promise, achievement and deception.

Technology has touched every aspect of dentistry from diagnosis to treatment. The promises and limitations of several emerging technologies, including lasers, digital radiology and electronic anesthesia, are reviewed.

Today's sonics: using the combined hand/sonic endodontic technique.

Combing sonic technology with hand instrumentation facilitates root canal preparation. The authors present an efficient and safe technique.

Amalcore strength recovery following refilling of access preparations with amalgam.

After endodontic treatment through an amalgam core, the recommended procedure is to replace the entire core. This study examined the strength achieved by restoring the access openings with dental amalgam and reported the type of failure during strength testing. Seventy-two Dispersalloy 8 x 8 mm cylindrical specimens were produced using controlled condensation pressures. The specimens were randomized in three groups: (1) controls, (2) 3 mm access preparations wetted with mercury-rich amalgam before restoration, and (3) 3 mm access preparations restored unwetted. The specimens tested for compressive strength were separated in two subsets. The unwetted group demonstrated significantly less strength than the control and wetted group (p less than 0.05), while the unwetted and wetted groups revealed significantly less strength than the control group (p less than 0.05). The mean diametral tensile strength recovery for the wetted and unwetted groups was 76% and 69%, respectively. The qualitative assessment of the fracture zones indicated that wetted specimens exhibited more fractures through the new amalgam core than the unwetted specimens (p less than 0.05). It would appear that amalgam refilling of access preparations through amalgam cores has clinical potential.

Spotlight on lasers. A look at potential benefits.

Before lasers can be highly integrated into clinical practice, further research must prove the efficacy, efficiency, consistency and safety of this new technology. Currently, increased caries prevention and rapid laser etching are two potential benefits of laser technology.

Dental lasers and science.

We have attempted to accomplish two purposes in this article. First, we have presented the case that extensive scientific investigation must form the base of our profession, that it must be an ongoing, continuous process and that laser dentistry must be developed through extensive scientific inquiry--as all of our treatment modalities should be. Second, we have presented many examples of the science involved in the development of laser dentistry. Lasers do have far-reaching potential for application to dentistry. We, as a profession, must insist that such laser development is done properly, not foisted upon us based on anecdotal reports and incomplete research.

Efficient and effective root canal retreatment without chloroform.

A root canal retreatment technique is described which eliminates the need for chloroform as a gutta percha solvent. This technique utilizes the gutta percha softening actions of both a self-heating instrument and the heat-potentiated solvent action of eucalyptol. In addition, sonics/ultrasonics and/or Gates-Glidden drills are suggested as useful adjuncts to canal debridement during re-preparation of the canal system. Given the controversy regarding the toxicity of chloroform, both for dental patients and dental personnel, practitioners may wish to consider using this retreatment technique to eliminate chloroform from endodontic retreatment procedures, while still achieving effective, efficient root canal retreatment.

Comparative bactericidal exposures for selected oral bacteria using carbon dioxide laser radiation.

Although relatively high CO2 laser energies have been shown to sterilize root canals, the response of several bacterial strains to decreasing exposures of CO2 laser energy remains unknown. Freshly grown bacterial cells were irradiated on glass microscope coverslips. A comparison of equivalent energy exposures with differing parameters was made on the bacterial viability. No statistically significant difference was found in the energy required to kill closely related bacterial species. However, the energy density required to kill greater than 99.5% of the bacteria is less than 200 J/cm2, much less than that shown to sterilize in a previous study.

The emerging role for lasers in endodontics and other areas of dentistry.

This article focuses on the emerging role of lasers in endodontic therapy, a discipline where lasers could significantly change the way we practice. The use of the CO2 laser in caries prevention therapy and laser etching is also discussed to illustrate how the same laser can be used for other important procedures in dental practice by simply varying the exposure parameters. Lasers will have a definitive place in dentistry in the future, but to be practical, one dental laser will have to be applicable to a number of therapeutic procedures. This article discusses just such a situation relating to a wide variety of endodontic procedures, caries preventive procedures, and laser etching of enamel. Due to its very favorable absorption on dental hard tissues, the CO2 laser will also undoubtedly be useful for many other procedures in dental practice.

Bactericidal action of carbon dioxide laser radiation in experimental dental root canals.

The ability of a carbon dioxide laser to sterilize the root canal of human teeth has been investigated. Three oral bacteria, Streptococcus sanguis, Streptococcus mutans, and Actinomyces viscosus, and three other bacteria, Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa were used as experimental organisms. Exposure of cells on glass slides to laser radiation showed there was little difference in the exposure required to kill these six organisms. Complete recovery of bacteria from the root canal was initially a problem and was only achieved when bacterial manipulations and removal were carried out in rapid succession, within 5 min of inoculation. However, the geometry of the instrumented canal and the laser alignment were major factors in achieving consistent cell death of oral bacteria in the root canals. Using sets of 10 teeth, four repeated exposures of 10 W for 1 s was found to sterilize 4 or more of the teeth.

The effects of cyclical axial motion on rotary endodontic instrument fatigue.

A potential problem with the use of rotary engine-driven files to flare canals is metal fatigue and subsequent breakage. This study analyzes the effects of cyclical axial motion on instrument failure by fatigue testing of endodontic files with and without cyclical axial motion. Eighteen new instruments, sizes 15 to 45, were mounted in a lathe and turned at 1650 rpm in the lubricated lumen of a curved Pyrex capillary tube until failure occurred. Nine instruments of each size were turned with cyclical axial motion and nine were turned without it. The results indicated that cyclical axial motion can significantly extend the life span of rotary engine files. Torsional forces were not considered in this study.