Light and scanning electron microscopic evaluation of Glyde File Prep in smear layer removal

Herbal Medications in Endodontics and Its Application-A Review of Literature

Herbal products are gaining popularity in dental and medical practice nowadays due to their biocompatibility, higher antimicrobial activity, antioxidant and anti-inflammatory properties. Herbal medicine has experienced rapid growth in recent years due to its beneficial properties, ease of availability, and lack of side effects. As pathogenic bacteria become more resistant to antibiotics and chemotherapeutic agents, researchers are becoming more interested in alternative products and treatment choices for oral diseases. As a result, natural phytochemicals separated from plants and utilized in traditional medicine are suitable substitutes for synthetic chemicals. The aim of this review article is to list and understand several herbal alternatives that are currently accessible for use as efficient endodontic medicaments. The herbal products used in endodontics have several advantages, including safety, ease of use, increased storability, low cost, and a lack of microbial tolerance. However, preclinical and clinical testing and interactions with other materials and adverse effects are required for these herbal products.

An in vitro investigation of the sealing ability of biodentine and mineral trioxide aggregate as retrofilling materials after the use of various irrigating solutions

Aim:

Materials and Methods:

Statistical Analysis:

Results:

Conclusion:

Canal transportation and centering ability of root canals prepared using rotary and reciprocating systems with and without PathFiles in cone-beam computed tomography-based three-dimensional molar prototypes

Background:

It is important to use instruments that cause minimal changes in the canal path for root canal preparation. There is inadequate literature comparing rotary and reciprocating systems and hand files. No study used three-dimensional printed models to compare rotary, reciprocating, and hand files.

Aims:

We aimed to assess the canal transportation and centering ability of WaveOne Gold, ProTaper Gold, and NiTi Flex K-file systems with and without glide path preparation.

Material and Methods:

Forty-nine resin models were randomly divided into Group I A – WaveOne Gold with WaveOne Gold Glider and Group I B – WaveOne Gold without glide path; Group II A – ProTaper Gold with ProGlider and Group II B – ProTaper Gold without glide path; and Group III A – NiTi Flex K-files with no. 10 stainless steel K-file and Group III B – NiTi Flex K-files without glide path. Pre- and postinstrumentation cross-sectional images at levels 3, 5, 7, 9, and 11 mm were compared.

Results:

WaveOne Gold caused the least canal transportation and improved centering ability (P < 0.05). NiTi Flex K-files transported the canal more than others in the apical levels (3, 5 mm). Glide path creation reduced canal transportation and improved canal-centering ability.

Conclusions:

WaveOne Gold system has better centering ability and lesser canal transportation than ProTaper Gold and NiTi Flex K-file. Glide path creation reduced canal transportation and improved canal-centering ability.

Scanning electron microscopic evaluation of the efficacy of 5% ethylenediaminetetraacetic acid for smear layer removal

The purpose of the study was to evaluate the smear layer removal efficacy of novel Saver® irrigating solution including 5% EDTA and to compare the 17% EDTA as the most used counterpart. Forty-four single-rooted teeth were divided into four groups, were instrumented, and irrigated. The smear treatment groups were as follows: sterile distilled water; 5.25% sodium hypochlorite; Saver®; 17% EDTA. The root samples were blinded. The micrographic images of root samples were collected by scanning electron microscope. The percentages of open dentin tubules were quantified using an image analysis software on micrographs. Two-way ANOVA followed by Tukey's multiple comparisons was used (p < .05). The 17% EDTA showed the highest percentages of open dentin tubules than the other treatments (p < .01). The mean percentages of open dentin tubules of 17% EDTA revealed statistically highly significant differences than Saver® treatment in all root regions (p < .01). Dentin tubules were covered by dense smear layer in distilled water irrigation whereas, the tubular pattern of dentin structure was not observed in hypochlorite irrigation. The commercial Saver® product presented to be less cleaning property on the smear layer than 17% EDTA and failed to show any improvement in the removal of smear layer compared with its tested counterpart.

Azadirachta indica A. juss, Morinda citrifolia L. and Triphala as herbal endodontic irrigants: A scoping review

Background:

The success of the root canal treatment depends on the complete elimination of the microflora, biofilms and smear layer from the pulp space. A wide variety of chemical endodontic irrigants are available to achieve disinfection and thorough debridement besides mechanical means. However, detrimental properties such as allergic potential, cytotoxicity, antimicrobial resistance and safety concerns have intrigued researchers over the years to look for safer options.

Aim:

The review is aimed at providing comprehensive information of the studies evaluating the efficacy of Azadirachta indica A. juss (A. indica), Morinda citrifolia L. (M. citrifolia) and Triphala (fruits of Emblica officinalis Gaertn., Terminalia chebula (Gaertn.) Roxb. and Terminalia belerica Retz.) as herbal endodontic irrigants.

Materials and methods:

The literature review was conducted using indexed databases (PubMed, Google Scholar, Cochrane) electronically for publications in peer-reviewed journals for relevant articles evaluating the efficacy of A. indica, Triphala, M. citrifolia as endodontic irrigant from the year 1985-March 2020.

Results:

A total of 58 studies were identified for full text reviewing after duplicate removal and screening title and abstracts. A total of 32 studies were included and processed for data extractions.

Conclusion:

Various in-vitro/in-vivo studies utilizing these herbal irrigants have documented promising results and hold the potential to replace chemical endodontic irrigants in routine practice but more preclinical and clinical trials are needed to substantiate these results before they can conclusively be recommended as intracanal irrigating solutions.

Comparative Evaluation of Cleaning Efficacy using Four Novel Nickel-titanium Rotary Instruments: An in vitro Scanning Electron Microscope Study

AIM

The aim of the study was to compare the cleaning efficacy (debris and smear layer removal) of two multifile rotary systems (MTwo and Silk) and two single-file rotary systems (F6 Skytaper and NeoNiTi).

MATERIALS AND METHODS

Eighty mesial canals of mandibular first molars were cleaned and shaped using four nickel-titanium (NiTi) rotary instruments to size # 25 and 3% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA). Samples were randomly divided into four equal groups (n = 20) according to instrumentation: Group I, Mtwo; group II, Silk; group III, F6 Skytaper; group IV, NeoNiTi. Samples were split longitudinally and examined under scanning electron microscope (SEM) for debris and smear layer removal in coronal, middle, and apical thirds of each root canal.

RESULTS

F6 skytaper and Mtwo groups showed significantly higher debris removal than Silk and NeoNiTi groups in apical third of root canal as well as when compared with NeoNiTi group in middle third. F6 Skytaper group showed significantly higher debris and smear layer removal than Silk group in coronal third. There was statistically significant difference among all thirds of root canal in terms of debris removal in Silk and NeoNiTi groups. There was statistically significant difference among all thirds of root canal in F6 Skytaper and NeoNiTi groups in terms of smear layer removal.

CONCLUSION

F6 Skytaper single-file rotary instrumentation showed the maximum cleaning efficacy followed by Mtwo multifile rotary instrumentation in all thirds of root canal.

CLINICAL SIGNIFICANCE

F6 Skytaper rotary instrument is most efficient followed by Mtwo rotary instrument among all rotary instruments.

Effectiveness of Three Different Irrigants - 17% Ethylenediaminetetraacetic Acid, Q-MIX, and Phytic Acid in Smear Layer Removal: A Comparative Scanning Electron Microscope Study

Background:

Removal of smear layer from the root canal walls is important for long-standing endodontic success.

Aim:

The aim of this study is to evaluate and compare smear layer removing ability among 17% ethylenediaminetetraacetic acid (EDTA), Q-MIX, and phytic acid by scanning electron microscopy (SEM).

Materials and Methods:

This in-vitro experimental study assessed smear layer removal using three different irrigants. Thirty single-rooted freshly extracted human permanent premolars were collected, disinfected, and decoronated to a standardized root length of 13 mm. Root canals were cleaned and shaped till F2 universal rotary protaper at working length 1 mm short of the apex. They were randomly divided into three groups, and final irrigation was done accordingly. Group 1 (n = 10): with 1 ml of 17% EDTA, Group 2 (n = 10): with 1 ml of Q-MIX, Group 3 (n = 10): with 1 ml of phytic acid. Samples were then longitudinally sectioned and evaluated under SEM at coronal, middle, and apical levels.

Statistical Analysis:

Two-way analysis of variance and Tukey's post hoc test were performed. The level of significance was set at 0.05.

Results:

Smear layer removing ability among irrigants and sections in descending order: 17 EDTA > Q-MIX > phytic acid; coronal > middle > apical.

Conclusion:

17% EDTA showed better and promising results followed by Q-MIX and then phytic acid.

Micro-CT evaluation of several glide path techniques and ProTaper Next shaping outcomes in maxillary first molar curved canals

AIM

To evaluate the ability of ProGlider instruments, PathFiles and K-files to maintain canal anatomy during glide path preparation using X-ray computed micro-tomography (micro-CT).

METHODOLOGY

Forty-five extracted maxillary first permanent molars were selected. Mesio-buccal canals were randomly assigned (n = 15) to manual K-file, PathFile or ProGlider groups for glide path preparation. Irrigation was achieved with 5% NaOCl and 10% EDTA. After glide path preparation, each canal was shaped with ProTaper Next X1 and X2 to working length. Specimens were scanned (isotropic voxel size 9.1 μm) for matching volumes and surface areas and post-treatment analyses. Canal volume, surface area, centroid shift, canal geometry variation through ratio of diameter ratios and ratio of cross-sectional areas were assessed in the apical and coronal levels and at the point of maximum canal curvature. One-way factorial anovas were used to evaluate the significance of instrument in the various canal regions.

RESULTS

Post-glide path analysis revealed that instrument factor was significant at the apical level for both the ratio of diameter ratios and the ratio of cross-sectional areas (P < 0.001), with an improved maintenance of root canal geometry by ProGlider and PathFile. At the coronal level and point of maximum canal curvature, ProGlider demonstrated a tendency to pre-flare the root canal compared with K-file and PathFile. PathFile and ProGlider demonstrated a significantly lower centroid shift compared with K-file at the apical level (P = 0.023). Post-shaping analysis demonstrated a more centred preparation of ProGlider, compared with PathFile and K-files, with no significant differences for other parameters.

CONCLUSIONS

Use of ProGlider instruments led to less canal transportation than PathFiles and K-files.

Scanning Electron Microscopic Evaluation of Residual Smear Layer Following Preparation of Curved Root Canals Using Hand Instrumentation or Two Engine-Driven Systems

Introduction:

In this experimental study, the amount of smear layer (SL) remnants in curved root canals after chemomechanical instrumentation with two engine-driven systems or hand instrumentation was evaluated.

Methods and Materials:

Forty-eight mesiobuccal roots of mandibular first molars with curvatures ranging between 25 and 35 degrees (according to Schneider’s method) were divided into three groups (n=16) which were prepared by either the ProTaper Universal file series, Reciproc single file system or hand instrumentation. The canals were intermittently irrigated with 5.25% NaOCl and 17% (ethylenediaminetetraacetic acid) EDTA, followed by distilled water as the final rinse. The roots were split longitudinally and the apical third of the specimens were evaluated under 2500× magnification with a scanning electron microscope (SEM). The mean scores of the SL were calculated and analyzed using the non-parametric Kruskal-Wallis and Mann-Whitney U tests.

Results:

The mean scores of the SL were 2.00±0.73, 1.94±0.68 and 1.44±0.63 µm for the ProTaper Universal, Reciproc and hand instrumentation, respectively. Mean score of SL was significantly less in the hand instrumentation group than the ProTaper (P=0.027) and Reciproc (P=0.035) groups. The difference between the two engine-driven systems, however, was not significant (P=0.803).

Conclusion:

The amount of smear layer in the apical third of curved root canals prepared with both engine-driven systems was similar and greater than the hand instrumentation technique. Complete cleanliness was not attained.

An in vitro study to compare the effectiveness of F-fle with ultrasonically activated K-fle to remove smear layer by using a scanning electron microscope

AIM

The aim of this study was to compare the effectiveness of the F-fle with an ultrasonically activated #15 K-fle in removing the smear layer after biomechanical instrumentation along with irrigation of Saline, NaOCl and with or without a fush of EDTA.

MATERIALS AND METHODS

Sixty decoronated human premolar teeth with a single canal were instrumented with ProTaper using S1, S2 and F1 series to produce the smear layer and randomly divided into two groups. Group A used Ultrasonics and group B used F-fle for activation of irrigants respectively. Each group was further divided in to three subgroups consisting of 10 teeth in each as I, II, III consisting of saline, NaOCl, NaOCl and EDTA as irrigants respectively. SEM micrographs were taken and amount of smear layer removal was analyzed by using Chi-square statistics tests.

RESULTS

Most effective smear layer removal was seen only when EDTA was used. There was no statistically signifcant difference between the groups A and B in removal of smear layer.

CONCLUSION

There was no increase in smear layer between use of F-fle when compared with the Ultrasonically activated K-fle. CLINICAL SIGNIFCANCE: The F-fle although does not have a superior effcacy than the ultrasonics in removal of smear layer from root canals but when used along with EDTA, can be an effective alternative for the dentists who are unable to bear the initial setup cost of ultrasonics.

Effect of endodontic irrigation and dressing procedures on the shear bond strength of composite to coronal dentin

This study aimed to evaluate the effects of three sodium hypochlorite (NaOCl)-endodontic irrigation procedures used alone or in combinations with two intermediate dressing materials on bond strengths of two adhesive composite systems to coronal dentin. Surfaces were treated with NaOCl or NaOCl–Glyde-File-Prep (H₂O₂ and EDTA) with or without chlorhexidine (CHX) as a final rinse. Intermediate dressing materials of calcium hydroxide (Ca(OH)₂) and sodium perborate (SP) were combined with surface treatments. Surface treatment groups (n = 10/group) included (1) distilled water (control), (2) 5.25% NaOCl (30 min), (3) NaOCl/Glyde (30 min), (4) NaOCl/Glyde (30 min) + CHX (2 min), (5) NaOCl/Glyde (30 min) + Ca(OH)₂ (5 days) + CHX (2 min), and (6) NaOCl/Glyde (30 min) + SP (9 days) + CHX (2 min). For each surface treatment group, dentin shear bond strengths of two different composite systems (Excite/Tetric Flow Chroma, [EX/TFC], and Clearfil Protect Bond/Protect Liner F [PB/PLF]) were evaluated. Median shear bond strengths (EX/TFC, PB/PLF) for each surface treatment group in MPa were (1) 21, 18; (2) 26, 18; (3) 21, 17; (4) 22, 16; (5) 17, 11; and (6) 14, 11, respectively. NaOCl significantly increased the bond strength of EX/TFC (p < 0.05), but did not significantly affect that of PB/PLF. The use of NaOCl/Glyde with CHX did not significantly affect EX/TFC (p > 0.05), whereas it significantly decreased PB/PLF (p < 0.05). Ca(OH)₂ and SP significantly decreased the bond strengths of both adhesive systems (p < 0.05). Adhesion to coronal dentin is dependent upon the irrigation regimen and the type of adhesive.

A comparative evaluation on the cleaning and shaping ability of three nickel titanium rotary instruments using computerized tomography - An ex vivo study

Introduction:

Successful root canal treatment depends primarily on the removal of micro-organisms through chemo-mechanical instrumentation of the root canal system. This encompasses shaping by mechanical removal of the dentine and cleaning by chemical disinfection of microorganisms and dissolution of organic tissues from the root canal. While root canal shaping can be predictably and efficiently attained with advanced instrumentation technology, effective cleaning of the entire root canal system remains a challenge. Rotary nickel titanium instruments are known for their efficient preparation of root canal. This is mainly because of the super elasticity of the nickel titanium alloy which gives an increased flexibility and allows the instrument to efficiently follow the original path of root canal. The purpose of this study is to compare the cleaning efficiency and shaping ability of M two, K3, Race ni-ti rotary instruments during the preparation of curved canals in extracted molars.

Materials and Methods:

Thirty teeth with 18 mm as their working length were selected and divided into three groups of 10 teeth each Angle of curvature, Radius of curvature, was determined using computerized tomography. A Pre and Post-operative measurement of canal width and volume was recorded and compared using CT. The teeth was then sectioned into two halves and subjected to scanning electron microscope. Images were taken at the level of apical third, middle third and coronal third for debris and smear layer. Scoring was done separately for both debris and smear layer.

Results:

Results were tabulated and statistically analyzed to evaluate the shaping ability and cleaning efficiency. Instruments were examined for any deformation or fracture during canal preparation.

Conclusion:

M two showed greater enlargements in all the three levels, when compared its width and volume, with other two instruments. K3 was better than Race when compared among them. In the scanning electron microscope study for debris and smear layer M Two performed better followed by K3 and Race.

Comparison of influence of different manufacturing methods on the cleaning efficiency of rotary nickel-titanium files

The purpose of this study was to evaluate and compare cleaning effectiveness of TwistedFile, GT series X, Revo-S, RaCe, Mtwo, and ProTaper Universal rotary files in curved canals. Seventy mesiobuccal canals of extracted human first maxillary molars were divided into seven groups of 10 samples each. Canals were prepared with six nickel-titanium (NiTi) rotary systems and manual K-Flexofile. Irrigation was performed with 2 mL 2.5% NaOCl solution after each file, and 5 mL 2.5% NaOCl was used for the final flush. After the roots were split longitudinally, the presence of debris and smear layer was visualized using scanning electron microscopic photomicrographs taken at coronal, middle, and apical third. Mean scores for debris and the smear layer were calculated and statistically analyzed for significance between groups using the Kruskal-Wallis nonparametric analysis of variance (P < 0.05) and Mann-Whitney U test (P < 0.001). There was no significant difference among the groups in terms of debris and smear layer scores (P > 0.05). Without considering the preparation method used, while no statistically significant difference was found between the coronal third and the middle third (P > 0.05), higher amount of debris and smear layer were found in apical third (P = 0.001). The new generation of NiTi rotary files including the Twisted File and GT Series X presented similar cleaning effectiveness compared with traditionally ground NiTi rotary files.

The effect of the NRT files instrumentation on the quality of the surface of the root canal wall

PURPOSE

To analyze in vitro, trough scanning electron microscope (SEM), the shaping ability of NRT NiTi rotary system (Mani, Inc, Toshigi-Ken, Japan).

METHODS

Ten extracted human teeth were cut at the level of the CEJ and prepared with Gates-Glidden burs 4-3-2 and NRT rotary files up to size #35. Irrigation was performed with 7.5 mL of 5% NaOCl and 7.5 mL of 10% EDTA during each canal instrumentation. Following the shaping sequence, a final irrigation was performed with EDTA followed by NaOCl, each left in situ for three minutes. Teeth were then fractured longitudinally, and the coronal, middle, and apical thirds of the canals were inspected with SEM. Three parameters, divided into four different levels (Alfa and Bravo, considered clinically acceptable; Charlie and Delta, considered clinically unacceptable), were used to score the canal morphology: presence and amount of smear layer; presence of organic and inorganic debris; surface profile.

RESULTS

SEM assessment revealed that in the coronal and middle third the majority of canals shaped with NRT rotary system presented a clinically acceptable surface. The apical third presented a higher amount of smear layer and dentinal debris instead, compared to the coronal and middle third.

CONCLUSIONS

NRT files demonstrated that they provided good instrumentation of the coronal and middle third, while being unable to obtain a defects-free surface in the apical third.

Comparative evaluation of surface characteristics of dentinal walls with and without using plastic finishing file

Aim:

The aim of this in vitro research is to evaluate the debris present on the dentinal walls after instrumentation in mesiobuccal root of maxillary molar with Hand Protapers, Hand Profiles, Hand Hero Shapers, and finishing the dentinal walls with and without rotary plastic files using stereomicroscope.

Materials and Methods:

Sixty freshly extracted human maxillary first molar teeth were divided into two groups of 30 teeth each (group A and B). Both the groups were divided into three subgroups of 10 teeth each (group A had subgroups A1, A2, and A3) and (group B had subgroups B1, B2 and B3). In group A, all the 30 canals were subjected to cleaning and shaping with three different instruments system and kept unfinished. This group was named as unfinished group. In group B, all the 30 canals were subjected to cleaning and shaping with three different instruments system followed by finishing with plastic files. This group was named as finished group. The crown of each tooth was sectioned at the cementoenamel junction. Canals were prepared following conventional principles of crown down technique. After splitting the roots longitudinally, the dentinal debris of each root canal was evaluated in three areas (coronal, middle and apical thirds of the root) by means of numerical evaluation scale, using a stereomicroscope.

Results:

Stereomicroscopic evaluations showed that there was no significant difference in the debris scores between the subgroups when the canals were instrumented with hand Protaper, hand Profile and hand Hero Shaper in all the thirds. There was no significant difference in scores between the unfinished group and the finished group in the coronal third but significant differences were seen in middle third and apical third.

Conclusions:

After instrumentation with different hand instruments, the use of plastic finishing files showed cleaner canal walls.

Cleaning ability of chlorhexidine gel and sodium hypochlorite associated or not with EDTA as root canal irrigants: a scanning electron microscopy study

The aim of this study was to evaluate the cleaning efficacy of 2% chlorhexidine gluconate gel (CHX) compared to 2.5% sodium hypochlorite solution (NaOCl) associated or not with 17% EDTA used as irrigants during the biomechanical preparation. Fifty freshly extracted single-rooted human teeth with complete apex formation were randomly divided into five groups: G1 - sterile saline, G2 - 2.5% NaOCl, G3 - 2% CHX, G4 - 2.5% NaOCl + EDTA and G5 - 2% CHX + EDTA. The specimens of G1 were subdivided into two control groups. The teeth were decoronated and the coronal and middle root thirds were prepared with Gates-Glidden burs, and the apical third was reserved to manual instrumentation. All procedures were performed by a single operator. In all groups, 2 mL of irrigant was delivered between each file change. The teeth were sectioned and prepared for analyses under scanning electron microscopy (SEM). SEM micrographs were graded according to a score scale by two examiners. Data were analyzed statistically by Kruskal-Wallis and Dunn tests at 1% significance level. The best results were obtained in the groups in which the irrigant was used followed by the chelating agent. No statistically significant difference was observed among G4, G5 and the positive control group (p<0.01). The groups G2 and G3 were significantly different from the others, presenting the worst cleaning capacity. In conclusion, the use of the chelating agent is necessary to obtain clean canal walls, with open tubules and no heavy debris. The use of 2% chlorhexidine gluconate gel alone is not able to remove the smear layer.

Scanning electron microscopic evaluation of debris and smear layer remaining following use of ProTaper and Hero Shaper instruments in combination with NaOCl and EDTA irrigation

OBJECTIVE

The purpose of this study was to evaluate the amounts of debris and smear layer remaining on canal walls after preparation with ProTaper and Hero Shaper instruments in combination with NaOCl and EDTA irrigation in curved root canals.

STUDY DESIGN

A total of 55 root canals were randomly divided into 2 instrumentation groups of 20 canals each and 1 negative control group of 15 canals. The canals in each of the 2 instrumentation groups were prepared with ProTaper or Hero Shaper instruments. Irrigation was performed with 5% NaOCl and 17% EDTA solutions. The control group was not instrumented. The remaining debris and smear layer were evaluated from scanning electron photomicrographs at x200 and x1,000 magnification taken in the coronal, middle, and apical thirds of the canals at both inner and outer canal walls. A 5-category scoring system for debris and smear layer was used. Statistical analysis was carried out using the Kruskal-Wallis and Mann-Whitney rank sum tests.

RESULTS

Completely clean root canals were not found in either instrumentation group. In the coronal and middle thirds, the canal walls of both instrumentation groups were clean, with no or only small areas of debris and smear layer. In the apical region, there were higher scores in terms of debris and smear layer in both instrumentation groups. No significant difference was found at the inner wall of the 2 instrumentation groups in terms of debris mean score. However, the outer canal walls prepared with ProTaper showed lower debris score compared with those prepared with Hero Shaper (P < 0.001). Concerning the smear layer, both the inner and outer canal walls prepared with ProTaper showed lower mean scores compared with those prepared with Hero Shaper (P < 0.001).

CONCLUSIONS

Within the limitations of this study, both instruments in combination with NaOCl and EDTA irrigation produced a clean and debris-free canal surface in the coronal and middle thirds, but were unable to produce a canal surface free from debris and smear layer in the apical third. However, the canals prepared with ProTaper instruments showed smaller amounts of debris and smear layer remaining in the apical region.

The influence of smear layer in lateral channels filling

This in vitro study evaluated the ability of a warm gutta-percha obturation system Thermafil to fill lateral channels in presence/absence of smear layer. Forty single-rooted extracted human teeth were randomly divided into two groups for which different irrigation regimens were used: group A, 5 ml of 5% NaOCl + 2.5 ml of 3.6% H(2)O(2); group B, 5 ml of 5% NaOCl 5% + 2.5 ml of 17% ethylenediamine tetraacetic acid. A conventional crown-down preparation technique was employed. Obturation was performed using epoxy resin-based cement (AH Plus) and a warm gutta-percha plastic carrier system (Thermafil). Specimens were cleared in methyl salicylate and analyzed under a stereomicroscope to evaluate the number, length, and diameter of lateral channels. Lateral channels were identified in both groups at medium and apical thirds. Additional samples were prepared for scanning electron microscopy inspection to confirm the presence of smear layer in group A, and the absence of smear layer in group B. All lateral channels resulted filled in both groups. No statistically significant differences regarding number, length, and diameter were observed between the two groups. Smear layer did not prevent the sealing of lateral channels.

Comparative study on the shaping ability and cleaning efficiency of rotary Mtwo instruments. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth

AIM

To compare the cleaning effectiveness and shaping ability of Mtwo, K3, and RaCe nickel-titanium rotary instruments during the preparation of curved root canals in extracted human teeth.

METHODOLOGY

A total of 60 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into three groups of 20 canals. Based on radiographs taken prior to instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared using a low-torque control motor. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. The amount of debris and smear layer was quantified on the basis of a numerical evaluation scale. The data established for scoring the debris and the smear layer was separately recorded and analysed statistically using the Kruskal-Wallis test.

RESULTS

During preparation no instrument separated. Completely clean root canals were never observed. For debris removal Mtwo instruments achieved significantly better results (P < 0.001) than K3 and RaCe instruments. The results for remaining smear layer were similar and not significantly different (P > 0.05). Mtwo instruments maintained the original canal curvature significantly better (P < 0.05) than the other instruments. Instrumentation with Mtwo files was significantly faster than with K3 or RaCe instruments (P < 0.05).

CONCLUSIONS

Under the conditions of this study, Mtwo instruments resulted in good cleaning and maintained the original curvature significantly better than K3 or RaCe files.

Effects on Smear Layer and Debris Removal with Varying Volumes of 17% REDTA after Rotary Instrumentation

The purpose of this study was to quantify the volume of 17% ethylene diamine tetra-acetic acid (EDTA) needed to efficiently remove the smear layer after rotary instrumentation, and to determine if additional irrigation has any effect on debris removal. Forty single canal teeth were instrumented with ProFile GT rotary instruments. Experimental groups were irrigated with 1, 3, or 10 ml of 17% EDTA for 1 min, followed by a final rinse with 3 ml of 5.25% sodium hypochlorite (NaOCl). Samples were scored for debris remaining and examined under SEM to determine quality of smear layer removal. There were no significant differences among groups when comparing either debris remaining or quality of smear layer removal. EDTA irrigation volume greater than 1 ml did not improve debris removal. Efficient removal of the smear layer was accomplished with a final rinse of 1 ml of 17% EDTA for 1 min, followed by 3 ml of 5.25% NaOCl.

Comparative investigation of two rotary nickel-titanium instruments: ProTaper versus RaCe. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth

AIM

To determine the cleaning effectiveness and shaping ability of ProTaper and RaCe nickel-titanium rotary instruments during the preparation of curved root canals in extracted human teeth.

METHODOLOGY

A total of 48 root canals of mandibular and maxillary molars with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 24 canals each. Based on radiographs taken prior to instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared using a crown-down preparation technique. After each instrument, the root canals were flushed with a 2.5% NaOCl solution and at the end of instrumentation with NaCl. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. After splitting the roots longitudinally, the amount of debris and smear layer was quantified on the basis of a numerical evaluation scale, using a scanning electron microscope (SEM). The data established for scoring the debris and the smear layer were separately recorded and analysed statistically using the Wilcoxon test.

RESULTS

Two ProTaper and three RaCe instruments fractured; there was no significant difference between instrument types (P > 0.05). Completely clean root canals were never observed. For debris removal, RaCe files achieved significantly better results (P < 0.001) than ProTaper instruments. The results for remaining smear layer were similar and not significantly different (P > 0.05). RaCe instruments maintained the original canal curvature significantly better (P < 0.05) than ProTaper instruments. No significant differences were detected between the instruments (P > 0.05) for the time taken to prepare the canals.

CONCLUSIONS

Under the conditions of this study, RaCe instruments resulted in relatively good cleaning and maintained the original curvature significantly better than ProTaper did.

Chelating agents in root canal treatment: mode of action and indications for their use

Chelating agents were introduced into endodontics as an aid for the preparation of narrow and calcified root canals in 1957 by Nygaard-Østby. A liquid solution of ethylenediaminetetraacetic acid (EDTA) was thought to chemically soften the root canal dentine and dissolve the smear layer, as well as to increase dentine permeability. Although the efficacy of EDTA preparations in softening root dentine has been debated, chelator preparations have regained popularity recently. Almost all manufacturers of nickel-titanium instruments recommend their use as a lubricant during rotary root canal preparation. Additionally, a final irrigation of the root canal with 15-17% EDTA solutions to dissolve the smear layer is recommended in many textbooks. This paper reviews the relevant literature on chelating agents, presents an overview of the chemical and pharmacological properties of EDTA preparations and makes recommendations for their clinical use.