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Páginas: 28 (6974 palabras) Publicado: 17 de noviembre de 2012
doi:10.1111/j.1365-2591.2009.01625.x

The effect of sodium hypochlorite and ethylenediaminetetraacetic acid irrigation, individually and in alternation, on tooth surface strain

R. Rajasingham1, Y.-L. Ng1, J. C. Knowles2 & K. Gulabivala1
Unit of Endodontology, and 2Unit of Biomaterials Science, Divisions of Restorative Dental Sciences and Biomaterials Science and Tissue-Engineering, UCLEastman Dental Institute, University College London, London, UK
1

Abstract
Rajasingham R, Ng Y.-L, Knowles JC, Gulabivala K. The
effect of sodium hypochlorite and ethylenediaminetetraacetic acid irrigation, individually and in alternation, on tooth surface strain. International Endodontic Journal, 43, 31–40, 2010.

Aim To evaluate the effect of irrigation regimens on tooth surface strain usingsaline, sodium hypochlorite (3% and 5% NaOCl) and ethylenediaminetetraacetic acid (17% EDTA), individually and in alternating combinations. Methodology Single-rooted premolar teeth with single canals prepared to standardized dimensions were grouped by anatomical features and randomly distributed amongst six experimental groups (n = 12 each). The six groups were: (1) saline; (2) 5% NaOCl; (3) 3%NaOCl; (4) 17% EDTA; (5) 3% NaOCl and 17% EDTA; (6) 5% NaOCl and 17% EDTA. All groups underwent four (group 1) or five (groups 2, 3, 4, 5, 6) sequential 30-min irrigation periods following each of which the tooth was subjected to a standard regime of cyclic, nondestructive, occlusal loading. Tooth surface strain was measured during each loading cycle using electrical strain gauges

mountedcervico-proximally. The data were analysed by Hierarchical anova and post hoc multiple comparisons. Results Irrigation with 5% NaOCl alone or alternating with 17% EDTA significantly (P < 0.001) increased the peak strain values for each of the irrigation periods compared with that of saline (group 1). The data for the other groups revealed no significant differences compared with those of saline. The strainincrease after the fourth irrigation cycle was significantly higher for group 6 than for group 2. The measured canal morphology and dentine thickness parameters did not prove to have a significant effect on tooth surface strain. Conclusions Irrigation with 5% NaOCl acting alone or alternated with 17% EDTA (used in 30 min cycles), significantly increased tooth surface strain. The alternated regimenshowed significantly greater changes in tooth surface strain than NaOCl alone. Irrigation with 3% NaOCl and 17% EDTA individually or in combination did not significantly alter the tooth surface strain. Keywords: ethylenediaminetetraacetic acid, irrigation, sodium hypochlorite, tooth surface strain.
Received 28 January 2009; accepted 15 July 2009

Introduction
It is widely believed that root filledteeth are more susceptible to fracture than teeth with vital pulps (Rosen 1961, Johnson et al. 1976, Gher et al. 1987)

Correspondence: K. Gulabivala, Professor and Head of Endodontology, UCL Eastman Dental Institute, 256 Gray’s Inn Road, London WC1X 8LD, UK (Tel.: 020-7915-1033; fax: 0207915-2371; e-mail: k.gulabivala@eastman.ucl.ac.uk).

but conclusive evidence is lacking. Nevertheless,there is circumstantial evidence for putative causes of nonvital and root filled tooth fracture (Burke 1992). The main causes could be: loss of tooth tissue, altered physical properties of dentine, and altered proprioceptive/nociceptive properties (Gutmann 1992, Gulabivala 1995, Kinney et al. 2003). These factors probably interact cumulatively to influence tooth loading, stress distribution and,ultimately result in catastrophic failure.

ª 2010 International Endodontic Journal

International Endodontic Journal, 43, 31–40, 2010

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Effect of irrigants on tooth strain Rajasingham et al.

Tooth tissue loss reduces the force required to strain and ultimately fracture teeth in vitro. The pattern of tooth tissue loss influences the magnitude of the induced strain (Mondelli et al. 1980,...
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