Comparison of irrigation penetration into the apical part of canals in hand and rotary instrumentations

The penetration of irrigating solution to the apical one third of canals and removal of debris are dependent on the final size of the instruments and instrumentation techniques used in the canals. The purpose of this study was to evaluate the effect of final instrument size, on irrigation penetration into the apical part of canals in hand K-file instrumentation versus rotary system of Hero 642. The mesiobuccal canals of 48 first mandibular molar teeth were selected for this study. The teeth were divided into 2 groups of 24 in each and the mesiobuccal canals were instrumented by hand K-file or rotary system of Hero 642 at 2 stages. After each stage, a contrast medium was injected into the canals and radiographs were taken by RVG system. The irrigation penetration was measured in radiographs by Diamax software. The data were analyzed using t -student test. This study showed that instrumentation up to # 25 file is not enough for irrigation penetration into the apical area. Also by more flaring the canals, more irrigating solution penetrates into the apical part of canals [P < 0.001], but the difference between hand and rotary systems was not statistically significant [P > 0.05]. According to this study, instrumentation up to # 30 file results in better irrigation penetration into the apical area. The flaring of the canals is essential for better cleaning and irrigation of apical area

[Cleaning efficacy of nickel titanium and stainless steel hand files compared to rotary nickel titanium files in moderate curved canals: a SEM study]

Recently, the Nickel-Titanium rotary instruments have been noticed because of their desired properties such as high flexibility, less transportation and perforation and less time consumption. Therefore, the aim of this study was to compare the cleaning efficiency of these instruments with hand stainless steel [SS] and Nickel-Titanium [NiTi] files. In this invitro experimental study 46 freshly extracted human molars with the curvature of 15-25 degree in mesial root were used. The teeth were randomly divided into 4 experimental groups, each containing 11 teeth and two control teeth. Then mesial canals were instrumented as follows: group 1: step back instrumentation with stainless steel hand files. group 2: passive step back instrumentation with stainless steel hand files group 3: step back instrumentation with Nickel- Titanium hand files group 4: crown down instrumentation with rotary Profile system No instrumentation was done on two control teeth. After crown amputation of teeth, the mesial roots were split in half and one half was randomly selected for SEM investigation. After SEM preparation, the photomicrographs were prepared from apical, middle and cervical part of canal with magnification of 2000 under SEM. These graphs were scored by an endodontist in a blind manner, according to the amount of residual debris and smear layer on canal surface. Then, the data was analyzed by Kruskal-Wallis and Mann-Whitney tests. The difference between 4 groups was not statistically significant according to the amount of residual debris [P>0.05]. But, rotary Profile system had produced more smear layer than other three groups [P<0.01]. This study showed that the amount of residual debris and smear layer after canal preparation in apical third is more than middle third and in middle third is more than cervical third [P<0.01]. After using the rotary instrumentation, it is better that canals were finally irrigated with combination of 17% EDTA and 5.25% NaOCl to remove the smear layer

Histopathologic evaluation of the subcutaneous tissue response to three endodontic sealers

The materials used for obturation of root canal system may be extruded through apical foramen into the periapical tissue. Therefore, biocompatibility of these materials is very important. The purpose of this study was to evaluate the in vivo biocompatibility of three conventional endodontic sealers: AH26, Roth 801, and ZOE after their subcutaneous implantation in rats. Twenty-two mature male Albino rats, weighting from 250 to 500gr were used. Each animal received four polyethylene implants; three implants were containing test sealers and one was empty tube as negative control. The animals were sacrificed at third day and third month after implantation and the implants were dissected with 2cm of surrounding tissue margins. Then, tissue reactions to the test materials were evaluated histologically and quantitatively by a pathologist under light microscope, after histologic processing and staining with H-E. The obtained results were analyzed statistically by Mann-Whitney test. After 3 days, tissue reaction to ZOE was more acute than AH26, Roth 801, and control group. But after 3 months, no significant difference was observed among these three sealers and among those and control group. According to this study, all of the sealers cause inflammatory reactions immediately after contact with tissue, but the intensity of these responses decrease with time. The acute responses of third day changed to chronic, proliferative, healing processes in third month

effect of EDTA and citric acid on smear layer removal of mesial canals of first mandibular molars, a scanning electron microscopic study

Background: the purpose of this in vitro study was to determine the effect of EDTA and citric acid on smear layer removal in different regions of root canals

Methods: in this study, mesial roots of 48 freshly extracted human mature mandibular first molar teeth with curved mesial roots of about 15-45 degrees and lengths of 20-23 mm were used. Instrumentation was done using the crown down technique by hand and rotary filing. Irrigant used during instrumentation was NaOCl. The teeth were divided in three groups. The mesial canals of teeth were irrigated by 17% EDTA in group I, 7% citric acid in group II and 5.25% NaOCl in group III as the control group. Then, the mesial roots were split in to two parts and studied under scanning electron microscopy

Results: the degree of cleanliness by 17% EDTA and 7% citric acid were 96.55% and 95% respectively. Although both solutions seem to be appropriate, their difference was statistically significant [P<0.05] and EDTA proved better than citric acid especially in middle and apical thirds of canals. The smear layer removal in apical area was less than that in other areas and was maximum in the middle third. However, the removal of smear layer in apical area was acceptable in both groups

Conclusion: it seems that use of both 17% EDTA and 7% citric acid offer desired results and they can remove smear layer from narrow and curved canals especially from apical region