ABSTRACT
AIM: The presence of calcium hydroxide (Ca(OH)2) in the root canal interferes with the apical root canal sealing and may result in periapical lesions in the long run. The present study was aimed to compare the efficacy of two rotary systems of Race and Mtwo in the removal of Ca (OH)2 aqueous-based from distobuccal canals of human maxillary molars. MATERIALS AND METHODS: A total of 44 distobuccal root canals of human maxillary molars were randomly distributed into two groups of 20 canals each and two control groups. Specimens in each group were instrumented with similar master apical rotary (MAR) and flexible files according to the manufacture's guidelines. The Ca (OH)2 paste was placed in canals using # 20 lentulo and radiographs were taken from the two dimensions. The roots were incubated for 1 week at 37°C and 100% humidity and Ca (OH)2 was removed from canals by MAR, afterward. Then, the roots were longitudinally split in halves by diamond disk and chisel without entering the root canals. Photos were taken from the canals' walls by a stereomicroscope with × 10 magnification. Next, according to a defined scoring system, photos were scored by four endodontists, so that scores 1 and 2 (nonvisible remnants or scattered remnants of Ca(OH)2) were considered as acceptable and scores 3 and 4 (distinct mass or densely-packed mass of Ca(OH)2) were regarded as nonacceptable. RESULTS: The obtained findings indicated that in coronal, middle, and apical portions of the root canal, 45, 60, and 65% of Mtwo specimens and 40, 50, and 55% of specimens prepared by the Race system acquired an acceptable score (1 and 2), respectively. Moreover, the results showed no significant difference between the two groups (P > 0.05). CONCLUSIONS: Both Mtwo and Race rotary systems with acceptable removal efficiency (score 1 and 2) were similarly able to remove Ca(OH)2.
ABSTRACT
INTRODUCTION: Retreatment is performed in teeth with unsuccessful root canal therapy or persistent apical lesion. The most important factor for achieving successful retreatment is thorough cleaning and reshaping. NiTi files and rotary instruments are widely used for the removal of obturatants. This study compared the ability of Mtwo and D-RaCe retreatment systems to remove residual gutta-percha and sealer within the root canal after retreatment. MATERIALS AND METHODS: This in vitro experiment was performed on sixty extracted human teeth. The samples were cut at the CEJ level, manually prepared, filled with gutta-percha and AH26 and finally stored at 37ºC for two weeks. Samples were then randomly divided into two groups. Group 1 was retreated with Mtwo and Group 2 with D-RaCe. Both groups were then divided into two subgroups retreated either with or without solvent. Teeth were then vertically sectioned for evaluation of residual filling materials on the canal walls. A microscopic assessment at 16× magnification was performed. T-test statistical analysis was used to compare the data. RESULTS: Comparison between the Mtwo and D-RaCe rotary systems revealed no significant differences in residual gutta-percha or sealer on canal walls (P=0.2). The study revealed a negative effect of solvent on removal of gutta-percha and sealer in both the Mtwo and D-RaCe systems. CONCLUSION: Mtwo and D-RaCe retreatment files removed residual gutta-percha and sealer similarly; there was no significant difference between them.
