Journal of Dental Medicine

Background and Aim: Preserving canal curvature during different phases of canal preparation is an important point. In Endodontic therapy all efforts are made to prepare canal in a way that final canal follows the primary canal curvature. The purpose of this study was to evaluate the efficacy of root canal preparation performed by students at Endodontic Department of Dental School, Tehran University of Medical Sciences.

Materials and Methods: In this retrospective study, classic method of step- back technique was investigated for preserving canal curvature in mesial roots of first mandibular molars and mesiobuccal roots of first maxillary molars between years 2000 and 2004. A randomly selected sample of 400 dental patient records was investigated by 4 observers (Endodontic department professors), searching for procedural errors. A clear explanation sheet of curvature preservation and procedural errors such as ledge formation, apical foramen transportation, zipping and stripping and a questionnaire were prepared for observers. The observers went through reliability test and kappa value for agreement between every two observers. The results were above 0.8. Data were analyzed by EPI6 statistical computer program, using Chi-Square and Fisher exact test with P<0.05 as the limit of significance.

Results: This study consisted of 152 first maxillary molars and 248 first mandibular molars. The prevalence of curvature preservation in mesial root of first mandibular molars and mesiobuccal root of first maxillary molars were 38.5% and 47.6% respectively. Procedural errors detected consisted of 33% ledge formation, 26.1% apical foramen transportation, 1.8% zipping and 4.1% stripping for mesial root of the first mandibular molars. The results for the first maxillary molars were 27%, 19%, 3.2% and 3.2% respectively.

Conclusion: The study results revealed the efficacy of endodontic education and the proficiency of junior and senior students in preparing curved posterior root canals. The results obtained in this retrospective study are comparable to prospective studies.

Background and Aim: Mechanical preparation of canal is one of the most important stages in root canal therapy. Various kinds of hand or rotary techniques are used for mechanical preparation of canal and each of them has advantages and disadvantages. During canal preparation, extrusion of debris from the apical foramen can result in periapical inflammation and increased pain and edema. The aim of this study was to compare hand instrumentation technique with three rotary systems (Profile, Race, Flex Master) regarding the amount of extruded debris from apical foramen during canal preparation.

Materials and Methods: In this experimental in vitro study, one hundred human extracted single rooted mandibular premolars with curvature between 0-10 degrees were selected and divided into four groups of 25 teeth each. All teeth were shortened to 15 mm length by cutting the crown. Group H was prepared by hand step back technique, group P by Profile system, group R by Race system and group F by Flex Master system. For debris collection, vials containing distilled water were used which were weighed before preparation. After the end of canal preparation, vials were completely dried and weighed again. The difference between weights of vials in two stages was the weight of debris extruded from apical foramen. The groups were compared by One-way ANOVA with p<0.05 as the level of significance.

Results: Group H had the highest mean weight of debris which showed significant difference with all three rotary groups (P<0.001). The lowest mean weight of debris was observed in group R (Race) which was significantly different from group F (Flex Master) but not significantly different from group P (Profile).

Conclusion: Based on the results of this study, race rotary system caused less debris extrusion from apical foramen compared to hand step back technique and Flex Master rotary system.

Background and Aim: The role of applying rotary instruments in reducing preparation time and proper root canal preparation have been approved in permanent teeth. The aim of this study was to compare the rotary instruments (Hero642) and K-files in root canal preparation of primary molars. Time and canal transportation were compared.

Materials and Methods: In this experimental, invitro study, 30 human extracted primary molars with 8 mm length were selected and divided into two equal groups. After preparing access cavity, group 1was prepared by K-files and group 2 by Hero642 systems. Before canal preparation, with # 15 K-file and after canal preparation, with master apical file, canal curvature was evaluated by Weine technique using Radiovisiography. Apical transportation was calculated. Time taken for preparation was recorded by chronometer. The results were analyzed with T-test and Mann-Whitney. P<0.05 was considered as the level of significance.

Results: The average canal transportation angle was 3.42 for Hero642 group and 7.33 for K-file group (p<0.04). The mean instrumentation time was 4.28 for Hero642 group and 8.76 minutes for K-file group (p<0.001). There was a significant difference between two groups.

Conclusion: Based on the findings of this study, it is suggested to apply Hero642 rotary instrument for primary molar canal preparation due to less preparation time and less canal transposition.