METHODS: A total of 60 dentinal blocks were prepared from freshly extracted teeth in three different thicknesses (300, 500 and 1000μm) and 20 sections in each of these thicknesses were divided randomly to the test and control groups. Samples in the test groups were irradiated at 2W power setting by scanning movement of 2mm/s of diode laser, and the controls were stored in normal saline. The flexural strength of samples was evaluated by UTM (Universal Testing Machine). Data analysis was done with the SPSS Software 11.5.
RESULTS: Samples of 300μ had the lowest flexural strength (mean: 71/65 mpa) followed by 500 (116.64 mpa) and 1000μ (217.56 mpa). Statistical analyses showed that after laser irradiation, the flextural strength in the samples of 300μ was significantly lower than that in the other groups (500μ, 1000μ) (P= 0.017).
CONCLUSION: Within the limits of this study, diode laser irradiation in laser assisted root canal therapy has no significant effect on flexural strength of root dentinal walls with the thickness of more than 500μ. Although in areas with critical dentinal width (≤300μ), this setting can jeopardize root micromechanical properties and predispose tooth to the root fracture.
Kakehashi S, Stanley HR, Fitzgerald RJ. The effect of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1965;20:340-9.
Moller AI, Fabricius L, Dahlen G, Ohman AE, Heyden G. Influence on periapical tissues of indigenous oral bacteria and necrotic pulp tissue in monkeys. Scand J Dent Res. 1981;89(6):475-84.
Bystrom A, Sundquist G. Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy. Scand J Dent Res. 1981;89(4):321-8.
Sjogren U, Hagglund B, Sundquist G, Wing K. Factors affecting the long-term results of endodontic treatment. J. Endod. 1990; 16(10):498-504.
McComb D, Smith DC. A preliminary scanning electron microscope study of root canals after endodontic procedures. J Endod. 1975;1(7):238-42.
Mader CL, Baumgartner JC, Peters DD. Scanning electron microscopic investigation of the smeared layer on root canal walls. J Endod. 1984;10(10):477-83.
Torabinejad M, Handysides R, Khademi AA, Bakland LK. Clinical implications of the smear layer in endodontics: A review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2002;94(6):658-66.
Oguntebi BR. Dentin tubule infection and endodontic therapy implications, Int Endod J. 1994;27(4):218-22.
Anic I, Tachibana H, Matsumoto K, Qi P. Permeability, morphologic and temperature changes of canal dentin walls induced by Nd:YAG, CO2 and argon lasers. Int Endod J. 1996; 29(1): 13-22.
Moritz A. Oral laser application. 1st ed. Quintessenz Verlags – GmbH; Berlin. 2006. 568p.
Bachmann L, Diebolder R, Hibst R, Zezell DM. Changes in chemical composition and collagen structure of dentine tissue after erbium laser irradiation. Spectrochim Acta A Mol Biomol Spectrosc. 2005;61(11-12):2634-9.
Lim SS, Stock CJ. The risk of perforation in the curved canal: anticurvature filing compared with the stepback technique. Int Endod J. 1987 Jan;20(1):33-9.
Lee BS, Chen MH, Lin YW, Lin CP, Chia JS, Wan-Hong Lan WH, et al. Bactericidal effects of diode laser on streptococcus mutans after irradiation through different thickness of dentin. Lasers Surg Med. 2006: 38(1):62–69.
Kreisler M, Al Haj H, Götz H, Duschner H, d’Hoedt B. Effect of simulated CO2 and GaAlAs laser surface decontamination on temperature changes in Ti-plasma sprayed dental implants. Lasers Surg Med. 2002;30(3):233-9.
Kreisler M, Kohnen W, Beck M, Al Haj H, Christoffers AB, Götz H, et al. Efficacy of NaOCl/H2O2 irrigation and GaAlAs laser in decontamination of root canals in vitro. Lasers Surg Med. 2003;32(3):189-96.
Bachinger HP, Davis JM. Sequence specific thermal stability of the collagen triple helix. Int J Biol Macromol. 1991;13(3):152-6.
Bank RA, Krikken M, Beekman B, Stoop R, Maroudas A, Lafeber FP, et al. A simplified measurement of degraded collagen in tissues: application in healthy, fibrillated and osteoarthritic cartilage. Matrix Biol. 1997; 16(5):233-43.
Little MF, Casciani FS. The nature of water in sound human enamel. A preliminary study. Arch Oral Biol. 1966;11(6):565-71.
Carlstrom D, Glas Je, Angmar B. Studies on the ultrastructure of dental enamel. V. The state of water in human enamel. J Ultrastruct Res. 1963;8:24-9.
Da Costa Ribeiro A, Nogueira GE, Antoniazzi JH, Moritz A, Zezell DM. Effects of diode laser (810 nm) irradiation on root canal walls: thermographic and morphological studies. J Endod. 2007 Mar;33(3):252-5.
Marending M, Stark WJ, Brunner TJ, Fischer J, Zehnder M. Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentin. Dent Traumatol. 2009;25(1):126-9.
Pascon FM, Kantovitz KR, Sacramento PA, Nobredos- Santos M, Puppin-Rontani RM. Effect of sodium hypochlorite on dentine mechanical properties. A review. J Dent. 2009;37(12):903-8.
Doyon GE, Dumsha T, von Fraunhofer JA. Fracture resistance of human root dentin exposed to intracanal calcium hydroxide. J Endod. 2005;31(12):895-7.
Sim TP, Knowles JC, Ng YL, Shelton J, Gulabivala K. Effect of sodium hypochlorite on mechanical properties of dentine and tooth surface strain. Int Endod J. 2001;34(2):120-32.