Effect of sodium hypochlorite on mechanical properties of dentine and tooth surface strain
Aim The aim of this study was to test the null hypothesis that sodium hypochlorite irrigation of root canals does not alter the properties of dentine and contribute to the weakening of root‐treated teeth. Methodology The effect of two concentrations (0.5%, 5.25%) of sodium hypochlorite (NaOCl) and s...
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Published in | International endodontic journal Vol. 34; no. 2; pp. 120 - 132 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
Blackwell Science Ltd
01.03.2001
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Subjects | |
Online Access | Get full text |
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Summary: | Aim
The aim of this study was to test the null hypothesis that sodium hypochlorite irrigation of root canals does not alter the properties of dentine and contribute to the weakening of root‐treated teeth.
Methodology
The effect of two concentrations (0.5%, 5.25%) of sodium hypochlorite (NaOCl) and saline on (i) the elastic modulus and flexural strength of machined dentine bars, and (ii) changes in strain of ‘whole’ extracted human teeth were evaluated. One hundred standardized plano‐parallel dentine bars (> 11.7 × 0.8 × 0.8 mm) were randomly divided into the three groups, immersed for 2 h in the respective solutions and then subjected to a three‐point bend test. Changes in strain of each of 10 teeth on cyclical nondestructive occlusal loading were measured using electrical resistance strain gauges bonded to the cervical aspects. Each tooth had its crown and enamel reduced and root canal prepared. These were irrigated sequentially in a series of four separate, 30‐minute regimes; initial‐saline, 0.5% NaOCl, 5.25% NaOCl and final‐saline. The changes in strains after each irrigation regime were compared.
Results
There was a significant decrease in elastic modulus of the dentine bars immersed in 5.25% NaOCl compared with the saline group (P < 0.01). There was also a significant decrease in flexural strength of the dentine bars in the 5.25% NaOCl group compared to both the saline and 0.5% NaOCl groups (P < 0.01). The strain data from the nondestructive tooth loading tests revealed significant increases in tensile strain between the initial‐saline and the final‐saline stages (P < 0.01). Significant increases in compressive strains were also found between initial‐saline and 5.25% NaOCl; and between 0.5% NaOCl and 5.25% NaOCl stages (P < 0.01).
Conclusions
The null hypothesis was rejected, 5.25% NaOCl reduced the elastic modulus and flexural strength of dentine. Irrigation of root canals of single, mature rooted premolars with 5.25% NaOCl affected their properties sufficiently to alter their strain characteristics when no enamel was present. |
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Bibliography: | ArticleID:IEJ357 ark:/67375/WNG-XK4ZHSSM-H istex:662E9B6C66F088049BF7AB5DD1FAD1B9DE245371 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 ObjectType-News-3 content type line 23 |
ISSN: | 0143-2885 1365-2591 |
DOI: | 10.1046/j.1365-2591.2001.00357.x |