Influence of storage conditions of extracted teeth on dentine removal by a standardised method of filing.

Extracted teeth are often stored in a variety of solutions for different lengths of time prior to use in studies on the efficacy of root canal preparation. The aim of this study was to evaluate the effect of duration (12 h, 1, 4 and 15 weeks) and type of storage medium (Saline, Formal-saline, Sodium Hypochlorite and Dry conditions) on dentine removal by standardised filing. Apparatus was constructed to standardise variables inherent in filing. These included the file, the rate, duration and amplitude of its push-pull motion, its alignment with a flat dentine surface, the interfacial force (80 gms) and rate of irrigation. Freshly extracted teeth were immediately stored in one of the 13 combinations of storage media and duration. The teeth were prepared into test specimens by splitting the roots and flattening the root canal surface. Twenty specimens were designated to each combination. Dentine removal was quantified by profilometry using maximum depth at 8 selected points. Statistical analysis of the mean values showed highly significant differences (p<0.001) between the media at 1, 4 and 15 weeks.When comparisons of mean values were made within the storage groups, there were highly significant differences (p<0.001) in dentine removal between 0, 1, 4 and 15 weeks of storage in sodium hypochlorite and saline. There were no significant differences found for storage in formal-saline. In dry conditions, the differences were significant (p<0.01) between 0, 1, 4 and 15 weeks of storage, but were not significant when the 4 weeks values were excluded.