Root Canal Therapy System for the Waterlase MDTM YSGG Laser Peer-Reviewed Clinical Articles

Dr. Gordon is a clinical assistant professor, Department of Endodontology, Kornberg School of Dentistry, Temple University, Philadelphia. Dr. Atabakhsh was a postdoctoral student, Department of Endodontology, Kornberg School of Dentistry, Temple University Philadelphia, when this article was written. He now maintains a private practice in Clinton, Md. Dr. Meza was a postdoctoral student, Department of Endodontology, Kornberg School of Dentistry, Temple University, Philadelphia, when this article was written. He now maintains a private practice in Reston, Va. Dr. Doms was a postdoctoral student, Department of Endodontology, Kornberg School of Dentistry, Temple University, Philadelphia, when this article was written. He now maintains a private practice in Roseville, Calif. Dr. Nissan is an associate professor, Kornberg School of Dentistry, Temple University, Philadelphia. Ms. Rizoiu is the vice president for clinical research and development, Biolase Technology, Irvine, Calif. Dr. Stevens is a professor and the chairman, Department of Endodontology, Kornberg School of Dentistry, Temple University, 3223 North Broad St., Philadelphia, Pa. 19140, e-mail “[email protected]”. Address reprint requests to Dr. Stevens. DISCLOSURE: The research project described in this article received financial support from Biolase Technology, Irvine, Calif., for materials purchase only. The antimicrobial efficacy of the erbium, chromium:yttrium-scandium-galliumgarnet laser with radial emitting tips on root canal dentin walls infected with Enterococcus faecalis Wanda Gordon, DMD; Vahid A. Atabakhsh, DDS; Fernando Meza, DMD; Aaron Doms, DDS; Roni Nissan, DMD; Ioana Rizoiu, MS; Roy H. Stevens, DDS, MS Copyright ©2007 American Dental Association. All rights reserved. R E S E A R C H A D V A N C E S I N D E N T A L P R O D U C T S JADA, Vol. 138 http://jada.ada.org July 2007 993 sodium hypochlorite and chlorhexidine also have demonstrated useful antimicrobial effects; however, here too, infection of the root canal and adjacent dentin many persist owing to the inability of these agents to reach all the infecting microorganisms. The use of intracanal medicaments such as calcium hydroxide typically requires multiple patient visits, since short-term application (of less than one week) has been found to be ineffective in eliminating endodontic infection. The elimination of infection would seem to be a worthy goal, since research has shown that the absence of infection before obturation of a tooth undergoing endodontic treatment results in a higher success rate. However, the multiple visits required for effective treatment with calcium hydroxide increases treatment time and reduces patient compliance, thus increasing the risk of treatment failure. Despite improvements in instrumentation techniques and the use of intracanal medicaments, endodontic treatment still can fail. Researchers have attributed such failure to the presence of residual intraradicular or, less frequently, extraradicular infection. Enterococcus faecalis is a gram-positive facultative anaerobic bacterium, and it frequently is isolated from endodontic cases requiring retreatment. It can infect dentinal tubules up to 800 micrometers from the root canal wall. E. faecalis is resistant to calcium hydroxide treatment. Sodium hypochlorite and chlorhexidine have proved to be effective against E. faecalis in vitro, but they require direct contact. Consequently, clinicians should seek an alternative disinfection technique. The erbium, chromium:yttrium-scandiumgallium-garnet (Er,Cr:YSGG) laser is a laser system unit approved by the U.S. Food and Drug Administration for cleaning, shaping and enlarging the root canal as well as for use in osseous, apical and periodontal surgery. The Er,Cr:YSGG laser can remove calcified hard tissues by emitting a beam of infrared energy at 2.78 μm that works in combination with a water spray. Previous studies have examined the effects of this laser on mucocutaneous soft tissue and root canal walls. The Er,Cr:YSGG laser is highly absorbed by water both surrounding and within the tissue. For this reason, it is possible that the laser may more efficiently disinfect tissue in the absence of a water spray, since this may focus more of the laser’s energy on the water within the bacteria. In addition, radially emitting laser tips, the latest laser beam source (developed and manufactured by Biolase Technology, Irvine, Calif.), may prove to be an improvement for use in disinfecting root canals. Owing to the direction of their laser emission, these tips could provide better coverage of the root canal walls than conventional, forward-emitting tips. This effect could increase the probability that the emitted laser energy will enter the dentinal tubules and have an effect on bacteria that are some distance from the canal. We conducted a study to evaluate the efficacy of the Er,Cr:YSGG laser (Waterlase, Biolase Technology) to disinfect E. faecalis–infected dentin when used with radially emitting laser tips. MATERIALS AND METHODS Model preparation. We sectioned 180 singlerooted teeth that had not been stored in sodium hypochlorite or any other disinfectant solution at the cementoenamel junction and at a point 3 to 4 millimeters from the apex. We then adjusted the resulting root section to a length of 5 mm. Using a diamond bur, we machined away the cementum and peripheral dentin of each root section, which resulted in a dentin cylinder approximately 5 mm in diameter that would fit within a hollowed-out plastic needle encasement (see below). Haapassalo and Orstavik showed that removal of the cementum layer is important in facilitating the ingress of the infecting microorganisms into the dentinal tubules. We enlarged the canal of each root section with Peeso-type reamers sizes no. 1 through no. 4, resulting in a canal with an approximate volume of 8 microliters. To remove the smear layer, we then treated the sectioned roots with 17 percent ethylenediamine tetraacetic acid for four minutes, followed by 5.25 percent sodium hypochlorite for another four minutes, and finally rinsed the roots in sterile water for 30 minutes. We infected the dentin cylinder models for one week, according to the protocol described by Haapassalo and Orstavik. We modified a 30-gauge ABBREVIATION KEY. BHI: Brain-heart infusion. BSG: Buffered saline with gelatin. CFU: Colonyforming unit. Er,Cr:YSGG: Erbium, chromium:yttrium-scandium-gallium-garnet. Log CFU: Logarithmic scale colony-forming unit. TA: Thallous acetate. Copyright ©2007 American Dental Association. All rights reserved. R E S E A R C H A D V A N C E S I N D E N T A L P R O D U C T S 994 JADA, Vol. 138 http://jada.ada.org July 2007 blue syringe needle assembly by uncapping and removing the needle from its encasement, then hollowing out the encasement with a bur. We applied Kneadatite epoxy putty (Polymeric Systems, Phoenixville, Pa.) (certified at 300 F and 2,000 pounds per square inch) to the external surface of each root section as well as to the apical end of each root section to create an airtight seal between the external dentin surface and plastic when the root section was placed in the hollowed-out needle encasement. The root section thereby was secured in place with the putty. We pipetted 500 μL of buffered saline with gelatin solution (BSG: sodium chloride 0.85 percent, anhydrous monopotassium phosphate 0.03 percent, anhydrous disodium phosphate 0.06 percent and gelatin 0.01 percent) into the apical cap, thus forming a buffer reservoir. We then returned the encasement (containing the root section) to the apical cap, over which we placed the cervical cap. The putty in all the models was allowed to set for at least 12 hours. This model allowed for a cap to cover both the cervical and apical ends of the root sections individually, thus creating a closed system (Figures 1 and 2). We stored the models in a cold, damp location to prevent the teeth from drying out. We autoclaved the models with slow exhaust for 15 minutes at 120 C before infection. During sterilization, approximately 50 μL of BSG in the reservoir was lost owing to evaporation, leaving 450 μL of BSG in the lower reservoir of the model. We divided the models into groups 1 through 18, with 10 models in each group, as shown in Table 1. Incubation conditions. We prepared overnight broth cultures (grown at 37 C) of E. faecalis (American Type Culture Collection 29212) in brain-heart infusion (BHI) broth (Difco Laboratories, Sparks, Md.). We used the broth cultures to infect the root dentin models. Infection of models. We used a micropipette with a sterile, gel-loading tip to transfer 8 μL of an overnight BHI broth culture of E. faecalis 29212 to the canal space of each model. We performed this inoculation by removing the cervical cap of each assembled model, injecting the bacterial sample into the canal space and replacing the cervical cap. After inoculation, we incubated all Prepared Root Section