In vitro comparison of the efficacy of rotary and hand files in removing gutta-percha and sealer from the root canals

AbstractIntroduction: An important step in retreatment of root canals is removal of filling materials and sealers from the root canal. The aim of this study was to compare the efficacy of rotary and hand files in removing gutta-percha and sealer from the root canals.Materials and methods: In this in vitro study 58 extracted human anterior teeth were collected. Standard access cavities were prepared after radiography. The canals were prepared using the step-back technique and obturated with gutta-percha and AH26 sealer. The teeth were divided into two experimental (n = 24) and two positive and negative control (n=5) groups. In one experimental group Gates-Glidden drills and Hedstrom files were used with chloroform to remove the filling materials from the canals and in the other Flexmaster and Hero 642 rotary instruments were used. In the negative control group 5.25% sodium hypochlorite and EDTA were used to achieve clean canals without any debris. In the positive control group the teeth were placed in an incubator without removing canal fillings. Then the teeth were split longitudinally and dyed with hematoxylin. Total canal surface area and area of remaining material in the apical, middle, cervical thirds of the canals were measured under a stereomicroscope and their ratio was calculated as percentage of remaining debris. Data were analyzed by t-test and paired t-test at 95% confidence interval.Results: The means of remaining filling materials in the entire canals in hand and rotary file groups were 4.73 and 5.85, respectively (p value = 0.05). Comparisons of the percentages of remaining filling materials in the entire canal lengths and in corresponding segments of the canal did not reveal any significant differences between the two groups (p value = 0.475).Conclusion: None of the two techniques evaluated was able to completely remove filling materials from the root canals, especially from the apical third. Key words: Preparation, Retreatment, Root canal, Root canal therapy, Sealer