High-power diode laser in the disinfection in depth of the root canal dentin Eliana Barbosa de Souza, MS, a Silvana Cai, MS, PhD, b Maria Regina Lorenzetti Simionato, MS, PhD, b and José Luiz Lage-Marques, MS, PhD, c São Paulo, Brazil UNIVERSITY OF SÃO PAULO Objective. The objective of this study was to evaluate the disinfection degree of dentine caused by the use of diode laser after biomechanical procedures. Study design. Thirty teeth were sectioned and roots were autoclaved and incubated for 4 weeks with a suspension of Enterococcus faecalis. The specimens were randomly divided into 3 groups (n = 10): G1, instrumented with rotary files, irrigated with 0.5% sodium hypochlorite and 17% EDTA-T, and then irradiated by 830-nm diode laser at 3 W; G2, the same procedures as G1 but without laser irradiation; and G3, irrigation with saline solution (control). Dentin samples of each third were collected with carbide burs and aliquots were sowed to count viable cells. Results. The disinfection degree achieved was 100% in G1 and 98.39% in G2, when compared to the control group (G3). Conclusion. Diode laser irradiation provided increased disinfection of the deep radicular dentin in the parameters and samples tested. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e68-e72) The success of endodontic therapy is solidly based on efficient disinfection of the root canal system. 1-4 Per- sistent contamination following chemical preparation is due to the inadequate execution of the technique and to the anatomical difficulties present in the radicular canal system. 5-8 Among the most commonly found microorganisms in root canal re-intervention with or without periradicu- lar lesions is the coccus gram-positive Enterococcus faecalis, which is resistant to endodontic therapy pro- cedures. 9-13 Many resources, such as interappointment dressings, irrigation solutions, and different types of laser radiations are used to act against these microor- ganisms, which are resistant to chemical surgical prep- arations. Disinfection of the main canal through use of laser radiation has been demonstrated by many studies. 14-17 It is worthwhile to analyze its effectiveness of decon- tamination deep in the dentin (dentinal tubules) where microorganisms that remain following endodontic treatment may cause failure. 18,19 The high-power diode laser has been tested in several areas of dentistry, with promising results in relation to dentinal disinfection. 20-26 Because of the laser’s prop- erties and its low cost in relation to most lasers used in endodontics, the diode laser has proved to be a resource worth testing. This study aims to verify the degree of disinfection deep in the dentin caused by the use of high-power diode laser irradiation, following chemo- mechanical procedures against Enterococcus faecalis. MATERIAL AND METHODS Thirty single-rooted teeth, supplied by the Human Tooth Bank from the College of Dentistry at the Uni- versity of São Paulo, were cut to a standard length of 15 mm, cleaned, and emptied with the help of file K-type #15 and 1% sodium hypochlorite in order to remove the pulp remains. Following these procedures, the apical third of these roots was gradually filed until reaching the K-type #40 (Dentsply-Maillefer, Ballaigues, Swit- zerland) in order to standardize the specimens. The roots were then waterproofed externally using cyano- acrylate (Super Bonder, Loctite Henkel, Itapevi, SP, Brazil) and dried at room temperature for 24 hours. The roots were set up in 1.5 mL Eppendorf tubes coated in heavy condensation silicone (Zetaplus, Zhermack, Rovigo, Italy) and the set underwent sterilization in a 134°C autoclave for 15 minutes. The authors thank Professor Geraldo Maia Campos for statistical analysis support, and Professor Patrícia Freitas from LELO-FOUSP. This study was supported by Brazilian agencies: FAPESP and CNPq. a Postgraduate Student of Endodontics, Restorative Dentistry Depart- ment, Dentistry Faculty, University of São Paulo, São Paulo, Brazil. b Associate Professor of Oral Microbiology, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil. c Associate Professor of Endodontics, Restorative Dentistry Depart- ment, Dentistry Faculty, University of São Paulo, São Paulo, Brazil. Received for publication May 14, 2007; returned for revision Feb 23, 2008; accepted for publication Feb 28, 2008. 1079-2104/$ - see front matter © 2008 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2008.02.032 e68