Root canal irrigants.

Regenerative endodontics: a review of current status and a call for action.

Irrigation in Endodontics

Chelating agents were introduced into endodontics as an aid for the preparation of narrow and calcified root canals in 1957 by Nygaard-Ostby. A liquid solution of ethylenediaminetetraacetic acid (EDTA) was thought to chemically soften the root canal dentine and dissolve the smear layer, as well as to increase dentine permeability. Although the efficacy of EDTA preparations in softening root dentine has been debated, chelator preparations have regained popularity recently. Almost all manufacturers of nickel-titanium instruments recommend their use as a lubricant during rotary root canal preparation. Additionally, a final irrigation of the root canal with 15-17% EDTA solutions to dissolve the smear layer is recommended in many textbooks. This paper reviews the relevant literature on chelating agents, presents an overview of the chemical and pharmacological properties of EDTA preparations and makes recommendations for their clinical use.

Chelating agents in root canal treatment: mode of action and indications for their use.

Debridement of the root canal by instrumentation and irrigation is considered the most important single factor in the prevention and treatment of endodontic diseases. In clinical practice, instrumentation of the root canal(s) within the affected tooth is usually the most time consuming and technically demanding element of the treatment. The technical success of the treatment, as judged by the post-operative radiograph after the root filling, is based on optimized root canal instrumentation. Mounting evidence from epidemiological research is also indicating that the combination of high-quality coronal restoration and technically satisfactory root canal treatment is associated with the greatest long-term prognosis. Therefore, it is not surprising that for several decades of endodontic research, a substantial number of articles on instruments and instrumentation have been published in the scientific literature. Although interest in the effects of instrumentation on intracanal infection is not new, it is obvious that during the last few years a renewed focus of interest has appeared on the relationship between instrumentation and infection control in the root canal. The ongoing discussion in international endodontics about one-appointment therapy in the treatment of apical periodontitis has naturally further motivated the newly emerged research activities. The goal of this review is to gather the relevant and most recent literature and provide an updated analysis of the effect of preparation (instrumentation and irrigation) on the microbial infection in the necrotic root canal.

Eradication of endodontic infection by instrumentation and irrigation solutions

A new solution for the removal of the smear layer.

Various organic acids, ultrasonic instruments, and lasers have been used to remove the smear layer from the surface of instrumented root canals. The purpose of this study was to investigate the effect of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) as a final rinse on the surface of instrumented root canals. Forty-eight extracted maxillary and mandibular single-rooted human teeth were prepared by using a combination of passive step-back and rotary 0.04 taper nickel-titanium files. Sterile distilled water or 5.25% sodium hypochlorite was used as intracanal irrigant. The canals were then treated with 5 ml of one of the following solutions as a final rinse: sterile distilled water, 5.25% sodium hypochlorite, 17% EDTA, or a new solution, MTAD. The presence or absence of smear layer and the amount of erosion on the surface of the root canal walls at the coronal, middle, and apical portion of each canal were examined under a scanning electron microscope. The results show that MTAD is an effective solution for the removal of the smear layer and does not significantly change the structure of the dentinal tubules when canals are irrigated with sodium hypochlorite and followed with a final rinse of MTAD. Microscopic examinations of root canals show that they are irregular and complex systems, with many cul-de-sacs, fins, and lateral canals. Additionally, numerous dentinal tubules open onto the root canal surface. When the dental pulp undergoes pathologic changes caused by trauma or carious invasion, the root canal system becomes susceptible to infection by several species of bacteria, with their toxins and their by-products. The microorganisms present in the root canal not only invade the anatomic irregularities of the root

SCIENTIFIC ARTICLES A New Solution for the Removal of the Smear Layer

Metallurgical Characterization of a New Nickel-Titanium Wire for Rotary Endodontic Instruments

Effects of raw material and rotational speed on the cyclic fatigue of ProFile Vortex rotary instruments.

Thermodynamic calculations have been used to construct time temperature sensitization (TTS) diagrams for AISI 304 stainless steels (SS). The quantitative Stawstrom and Hillert model, which is based on chromium diffusion control of sensitization, was used to calculate the TTS diagrams. Electrochemical potentiokinetic reactivation (EPR) tests were performed on these steels, with various nitrogen additions, to obtain the experimental TTS curves. The calculated and experimental TTS diagrams have been compared to better understand nitrogen addition effects on the sensitization kinetics of AISI 304 SS. These results indicate that nitrogen additions below 0.16 wt% retard the sensitization kinetics; one possible mechanism by which this is achieved is an increase in chromium concentration adjacent to the grain boundaries, which decreases the chromium concentration gradient between the austenite matrix and the grain boundaries and hence retards carbide growth.

William Ben Johnson

Papers

A new solution for the removal of the smear layer.

SCIENTIFIC ARTICLES A New Solution for the Removal of the Smear Layer

Metallurgical Characterization of a New Nickel-Titanium Wire for Rotary Endodontic Instruments

Effects of raw material and rotational speed on the cyclic fatigue of ProFile Vortex rotary instruments.

The Effect of Nitrogen on the Sensitization of AISI 304 Stainless Steel