Chemomechanical Instrumentation Research Articles

Antibacterial Efficacy of Rotary and Reciprocating Instrumentation Techniques.

To clinically evaluate the effectiveness of rotary (ProTaper Next [PTN]) and reciprocating (Wave One Gold [WOG]) instrumentation techniques in eliminating bacteria from the root canals of teeth with apical periodontitis during a single-visit root canal treatment. Forty patients were randomly assigned to the WOG or PTN instrumentation techniques groups. A single-visit root canal treatment was performed on all the patients. In both groups, root canals were irrigated with 10 ml of sodium hypochlorite (NaOCl) and the final irrigation protocol was applied. Microbiological samples from the root canal were collected initially (Sample 1), after chemo-mechanical instrumentation (Sample 2), and after the final irrigation protocol (Sample 3). Quantification of bacteria at each stage of root canal treatment was performed using the culture method (colony-forming units [CFUs]), and bacterial species were identified using MALDI-TOF mass spectrometry. There were 55 aerobic and anaerobic bacterial species identified. Chemo-mechanical root canal treatment with both instrumentation techniques and the final irrigation protocol significantly reduced the number of CFUs (p<0.001). There were no statistically significant differences in antibacterial efficacy between WOG and PTN groups (p>0.05). Although both root canal instrumentation techniques were highly effective in removing bacteria from the necrotic canals of teeth with chronic apical periodontitis, no complete eradication of bacteria was found in any sample.

Assessing the efficacy of various irrigation solutions in dissolving organic tissue

For successful root canal treatment, adequate chemomechanical instrumentation to eliminate microorganisms and pulp tissue is crucial. This study aims to assess the organic tissue dissolving activity of various irrigation solutions on bovine tooth pulp tissue. 40 extracted bovine mandibular anterior teeth (n = 10) were used for the study. Bovine pulp pieces (25 ± 5 mg) were placed in 1.5 ml Eppendorf tubes. Each tooth pulp sample was then covered with 1.5 ml of different irrigation solutions, dividing them into four groups: Group 1 with freshly prepared 5% Boric acid, Group 2 with 5% NaOCl, Group 3 with Irritrol, and Group 4 with Saline. Samples were left at room temperature for 30 min, then dried and reweighed. The efficacy of tissue dissolution ranked from highest to lowest was found to be NaOCl, Boric Acid, Irritrol, and saline (p < 0.05). It was observed that the decrease in the NaOCl group was greater than the decrease in the Irritrol and saline groups, and the decrease in the Boric acid group was significantly greater than the decrease in the saline group (p < 0.05). It also emphasizes the need for future studies to further investigate the effects of Irritrol and Boric Acid on tissue dissolution.

STEREOMICROSCOPIC ASPECTS OF ROOT CANAL WALLS AFTER CONVENTIONAL LASER ENDODONTICS – A PRELIMINARY STUDY

Bacterial decontamination of root canals can be improved by directly irradiating the dentinal walls with dental lasers or by irradiating/activating the irrigation solutions, the laser having an indirect clinical action. Inside the root canal, laser irradiation produces a thermal effect on the dentine walls and bacteria, which generates unwanted side effects, if the therapeutic protocol is not followed. The aim of this study was to evaluate the root canal walls by stereomicroscopic ex-amination, after their chemo-mechanical instrumentation and conventional laser irradiation. For this study, 35 palatal roots of upper first molars were used. For some of the palatal canals, con-ventional laser irradiation was performed using a diode laser with a wavelength of 980 nm and two different irradiation protocols. The root canal walls were examined stereomicroscopically at different degrees of magnification. The study demonstrated the effectiveness of the stereomicro-scope in examining the walls of prepared and laser irradiated root canals. Areas of morphological alteration were identified and measured on the walls of the root canals for which the irradiation protocol was not applied correctly.

Precision-milled simulated curved root canals in bovine dentine for the assessment of chemo-mechanical root canal preparation.

The aim was to develop a standardized curved root canal model in bovine dentine and to assess whether that natural substrate would behave differently from the resin in standard plastic training blocks when prepared chemo-mechanically. The impact of substrate microhardness on simulated canal transportation was considered. High-precision computer numerical control (CNC) milling was used to recreate a simulated root canal from a resin training block (Endo Training Bloc J-Shape, size 15) in longitudinally sectioned, dis- and re-assembled bovine incisor roots. Optical overlays obtained from 10 resin blocks were used to identify an average canal and program the CNC milling apparatus accordingly. Resin and dentine microhardness were measured. Simulated root canals in resin training blocks and their bovine counterparts were then instrumented at 37°C using Reciproc R25 instruments (VDW) with water or 17% EDTA (n = 10). Open-access image processing software was used to superimpose and analyse pre- and postoperative images obtained with a digital microscope. Centering ratios were averaged to indicate canal transportation. The effects of substrate and irrigant on canal transportation were assessed by two-way anova. Superimposed images showed that resin blocks under investigation varied considerably in terms of simulated canal length and curvature, whilst the milled canals were highly similar. The microhardness of dentine was more than three times higher than that of the resin. Conversely, canal transportation was considerably greater in dentine compared to resin, and in dentine had a tendency to be increased by EDTA. There was a strong effect of substrate on canal transportation (p < .001), no overall effect of irrigant, and a marginally significant interaction between irrigant and substrate (p = .077). CNC milling allows to create standardized simulated curved root canals in bovine dentine. These models may be useful to test and compare materials and concepts of chemo-mechanical root canal instrumentation. Microhardness is a bulk feature that does not predict the response to chemo-mechanical instrumentation of a composite material such as dentine.

NiTi rotary system in endodontics – An overview

Success of root canal treatment depends on complete removal of microorganisms which is done through chemomechanical instrumentation of root canal system. To achieve this, earlier stainless steel files were used which had inherent disadvantages of excessive tooth cutting as well as straightening of the canal curvature. This Eventually led to introduction of NiTi alloy which has proven to be a valuable adjunct in root canal preparation. These NiTi files are highly flexible and elastic due to their Metallurgical properties like Austenite, Martensite, Intermediate R phase. It has got greater strength and modulus of elasticity making them more beneficial in curved canals. Over the evolution various changes have taken place within the NiTi rotary systems and various generations too. Thus the Objective of this Review article is to completely discuss about Evolution, Metallurgy, Mechanical properties, Generations of NiTi rotary system.

Is XP-endo Finisher a better treatment option for its efficacy against intracanal bacteria for post-treatment apical periodontitis cases than EndoActivator?

To investigate the efficacy of the supplementary use of a rotary agitation method [XP-endo Finisher (XPF)] and sonically-activated irrigation [EndoActivator (EA)], using droplet digital PCR (ddPCR) on reducing the bacterial load in previously root canal treated teeth with apical periodontitis. Twenty patients with post-treatment apical periodontitis were allocated into two groups according to the irrigation activation method used: XPF and EA group. Total bacterial loads, as well as the amount of Enterococcus faecalis (E. faecalis) were determined before (S1) and after (S2) chemomechanical preparation, and after final irrigation activation (S3) by means of ddPCR. The bacterial copy numbers were compared between groups using the Friedman test (Nonparametric Repeated Measures ANOVA). When the groups were examined in terms of gender, age, number of root canals, periapical index score, sterility control total bacteria (SCTB), S1- and S2-total bacteria copy number, it was found that there was no statistical difference between the XPF group and the EA group (p > 0.05). Subsequent activation (S3) resulted in a significant microbial reduction in both XPF and EA groups, both of which reduced significantly more bacteria than chemomechanical instrumentation (S2) (p < 0.0001). On the contrary, S3-total bacteria copy number of the EA group was lower than the XPF group (p < 0.0147). There was no statistical difference between the XPF group and the EA group in terms of E. faecalis copy number (p > 0.05). Although both the XPF and the EA optimised the antibacterial efficiency of chemomechanical preparation in previously root canal-treated teeth with apical periodontitis, a lower total bacterial copy number was achieved with the EA application than the XPF application.

Impact of an Enhanced Infection Control Protocol on the Microbial Community Profile in Molar Root Canal Treatment: An in Vivo NGS Molecular Study

IntroductionRecent findings demonstrated that 1-year cone-beam computed tomography–based outcomes of molar root canal treatment were improved through an enhanced infection protocol (EnP), when compared with a current best-practice standard infection control protocol (StP). The EnP comprised measures to reduce iatrogenic contamination from direct and indirect contact surfaces, including the replacement of the rubber dams, gloves, files, all instruments, and surface barriers before root canal obturation. The aim of this study was to investigate the effect of such an EnP on resident microbiome present after chemomechanical instrumentation and the protocol ability in reducing iatrogenic contamination in molar teeth during root canal treatment. MethodsMolar teeth were block-randomized to receive treatment under EnP or StP. To compare the differential effect of the protocol on the identity of bacteria present, 150 matched DNA extracts from 75 molar teeth samples (StP, n = 39; EnP, n = 36) were evaluated. Samples were taken before (S1) and after (S2) chemomechanical preparation and were subjected to next-generation sequencing of the V3-V4 region of the 16S rRNA gene before bioinformatical identification using the HOMD oral microbiome database and downstream taxonomic processing, providing measures of richness and diversity of bacteria and significant bacterial taxa during chemomechanical instrumentation and the effect of the 2 treatment groups. ResultsEighty-eight microbial taxa were significantly more abundant in StP S2 samples, including endodontically relevant contaminants taxa as Actinomyces, Cutibacterium, and Haemophilus. The S2 samples demonstrated fewer residual bacterial species in the EnP group, with 26.8 observed species compared with 38.3 in the StP. Reduced diversity and richness measures were noted in the EnP pre-obturation samples compared with the StP in OTU, Chao1, and ACE indices (P ≤ .05). Differential microbial identities between S1 and S2 samples and protocols demonstrated that the previously observed increased effectiveness of the EnP protocol was likely to prevent recontamination or de novo contamination of the root canal space during treatment. ConclusionsThe implemented EnP resulted in a specific reduction of microbial taxa often associated with recontamination or iatrogenic contamination, suggesting the basis for improved infection control measures during root canal treatment.

Dentinal microcracks and cemental tears related to chemo-mechanical root canal instrumentation: a micro-CT Cadaver Study.

The prevalence of radicular defects after root canal instrumentation is unresolved. This study used micro-CT to assess the relationship between the formation of radicular defects and chemo-mechanical instrumentation in a cadaver model. Maxillary and mandibular molars (n = 24) were sectioned from cadaver specimens as a tissue block containing the teeth, alveolar bone and attached mucogingival tissues. After a baseline micro-CT scan (13.45 μm), the specimens were distributed into 3 groups (n = 8 molars): Reciproc® , ProTaper Next™ and Mtwo® . Micro-CT scans of each specimen were obtained after access, glide path and preparation with each instrument. The pre-operative and final post-operative micro-CT cross-sectional images of the roots were screened by two blinded examiners to identify any pre-existing and new radicular defects. Pre-existing and new radicular defects were examined histologically. Overall, 16 pre-existing radicular defects were identified in 12 of the 24 molars (50%). Most of these were cemental tears (87.5%), and not true dentinal microcracks. New dentinal microcracks were observed in the post-operative micro-CT scans of only 3 canals (3.9%; 3/77). However, only one of these defects was found to be present histologically. Within the limitations of the study, chemo-mechanical instrumentation did not routinely promote the formation of radicular defects.

Scanning electron microscopic analysis of interaction between 2% lidocaine hydrochloride (with adrenaline) with 3% sodium hypochlorite and 2% chlorhexidine on root canal dentin after Chemomechanical instrumentation: An in vitro study

Introduction: To investigate the effect of resultant precipitate formed on interaction between 2% lidocaine hydrochloride (with adrenaline) (LA) with 3% sodium hypochlorite (NaOCL) and 2% chlorhexidine (CHX) on root canal dentin after chemomechanical preparation using scanning electron microscopy (SEM). Methods: Thirty six mandibular premolars were decoronated, and the root length was standardized. All specimens were randomly distributed into the following three groups: Group I (control): 2% LA mixed with sterile water. Group II: 2% LA with 3% NaOCL, Group III: 2% LA with 3% CHX. In all groups mechanical instrumentation with rotary files was done. Teeth samples were sectioned into three parts, split and SEM analysis of root canal wall was done at cervical. Middle, and apical root thirds. Results: SEM images revealed patent dentinal tubules with no precipitate occlusion in group I and group III, whereas there was occlusion of dentinal tubules with a precipitate in group II at all the three root levels studied. Conclusions: The precipitate formed on the interaction between 2% LA solution with 3% NaOCL tends to occlude the dentinal tubules at the coronal, middle, and apical root thirds. The chemomechanical rotary instrumentation procedure did not effectively remove the precipitate from all the three root levels of the specimens studied. LA/sterile water group and LA/CHX group did not result in any precipitate formation on root canal dentin.

Comparative evaluation of antimicrobial efficacy of calcium hydroxide, curcumin and aloe vera as an intracanal medicament: An in-vivo study

For achieving predictable long-term success of nonsurgical endodontic treatment, complete debridement and effective disinfection of the root canal space are considered to be essential. The use of an intracanal medication remains an important adjunct in the total elimination of bacteria remaining even after chemo-mechanical instrumentation during endodontic treatment. Calcium hydroxide is most commonly used as intracanal medicament. Herbal alternatives like turmeric, neem, aloe vera etc. have the potential to be used as intracanal medicaments. The present study was undertaken for evaluating the antimicrobial efficacy of curcumin and aloe vera as an intracanal medicament for endodontic disinfection. : In this prospective randomised controlled study, 45 patients of age group of 18-55 years requiring endodontic therapy for single rooted, single canaled teeth with periapical lesions were selected. Patients were divided into 3 groups having 15 patients each, Group I (Curcumin), Group II (Aloe vera) and Group III (Calcium hydroxide). Under aseptic conditions preoperative and post-operative samples were collected &amp; sent to the microbiology laboratory. Antimicrobial property was assessed using the microbial colony count. : Distribution of median postoperative microbial colony counts among the cases studied did not differ significantly between Groups I and III (P-value&amp;#62;0.05) whereas it was significantly higher in Group II compared to Groups I and III (P-value&amp;#60;0.05 for both). It can be concluded that antimicrobial efficacy of curcumin showed highest antibacterial efficacy followed by calcium hydroxide and aloe vera as an intracanal medicament.

Etidronic acid and ethylenediaminetetraacetic acid associated with sodium hypochlorite have limited effect on the compressive fracture resistance of roots ex vivo.

Aims:To assess the effect of etidronic acid (EA) mixed with sodium hypochlorite (NaOCl) and two ethylenediaminetetraacetic acid-containing preparations (EDTA and SmearClear) alternated with NaOCl, as a final rinse, on root fracture resistance to a compressive force.Materials and Methods:Seventy-two premolar roots were randomly allocated to the following groups according to the irrigant solutions. For the EA group, 9% EA + 2.5% NaOCl were used throughout the assays (n = 21). The remaining groups received 2.5% NaOCl during and immediately after chemo-mechanical instrumentation. Intermediately, the roots received 17% EDTA (n = 19), or SmearClear (n = 16), or no irrigation (control) (n = 16) plus a final rinse with 2.5% NaOCl. The specimens were subjected to a vertical compressive force loaded at a crosshead speed of 0.02 mm/s parallel to the long axis of the root until fracture occurred. The results were compared statistically using the one-way analysis of variance for intergroup comparisons.Results:The negative control presented with the highest values, whereas the SmearClear presented with the lowest values, though no significant differences were found when comparing the different groups (P = 0.82).Conclusions:The use of EA + NaOCl or two EDTA formulations in association with NaOCl does not affect the fracture resistance of previously chemo-mechanically prepared roots.

Use of natural substitutes as an intracanal medicament in the endodontics-An update for in vivo studies

The success of root canal treatment depends on the elimination of bacteria by chemo-mechanical instrumentation and use of various irrigants to remove or dissolve organic and inorganic debris.The intracanal medicament also has an important role in the outcome of root canal treatment. With the rise in bacterial resistance to antibiotics, there is considerable interest in the development of other classes of antimicrobials for the control of infection. Use of Herbal intracanal medicament has been shown promising results when used under in vitro conditions, but very limited clinical trials reported due to the ethical concern. Hence, this review highlights the current guidelines (laid by the drugs and cosmetics act as per the Gazette of India) regarding the use of herbal medicaments for the clinical trials in Endodontics.

Herbal medicaments in endodontics - Current guidelines for in vivo studies in India.

Elimination of bacteria from infected root canal systems is a challenging task. Various techniques have been described to reduce the number of bacteria within the root canal system, which include chemomechanical instrumentation, use of various irrigants to remove or dissolve organic and inorganic debris, and to destroy bacteria. The intracanal medicament plays a key role in the success of root canal treatment. With the rise in bacterial resistance to antibiotics, there is considerable interest in the development of other classes of antimicrobials for the control of infection. Natural products are known to play an important role in human life. The use of herbal products as mouthwash has been tried and tested in the literature. However, the use of herbal intracanal medicament has been shown promising results when used under in vitro conditions, but in vivo studies are very scarce. This may be due to the limited supporting literature available to use it as intracanal medicament in patients due to the ethical concern. Hence, the purpose of this review is to highlight the current guidelines (laid by the drugs and cosmetics act as per the Gazette of India) regarding the use of herbal medicaments for the clinical trials in endodontics.

In vitro assessment of interaction between lidocaine hydrochloride and sodium hypochlorite on root canal dentin before and after chemomechanical instrumentation procedures.

Introduction:To investigate the effect of resultant precipitate formed on interaction between 2% lidocaine hydrochloride with adrenaline (LA) and 2.5% sodium hypochlorite (NaOCl) on root canal dentin before and after chemomechanical preparation, using scanning electron microscopy (SEM).Methods:Sixty mandibular premolars were decoronated, and the root length was standardized. All specimens were randomly distributed into the following three groups: Group I (control): 2% LA mixed with sterile water without root canal instrumentation, Group II: 2% LA with 2.5% NaOCl and no instrumentation, and Group III: 2% LA with 2.5% NaOCl, followed by mechanical instrumentation with rotary files. Teeth samples were sectioned into three parts, split and SEM analysis of the root canal wall was done at cervical, middle, and apical root thirds.Results:SEM images revealed patent dentinal tubules with no precipitate occlusion in the control group, whereas there was occlusion of dentinal tubules with a precipitate in all the specimens in Group II and Group III at all the three root levels studied.Conclusions:The precipitate formed on the interaction between 2% LA solution and 2.5% NaOCl tends to occlude the dentinal tubules at the coronal, middle, and apical root thirds. The chemomechanical rotary instrumentation procedure did not effectively remove the precipitate from all the three levels of the root specimens studied. LA/sterile water group did not result in any precipitate formation on root canal dentin.

Antibacterial activity of newly synthesized endodontic nanomaterial based on calcium aluminate

Introduction Materials used for root canal obturation and root perforation are expected to have, in addition to preventing apical, lateral and coronary leakage, antimicrobial effects on microorganisms that are not accessible to chemomechanical instrumentation and intra-canal medications. The aim of this study was to evaluate the antimicrobial effect of a novel calcium aluminate-based endodontic nanostructured biomaterial (ALBO-MCCA) using agar diffusion test. Material and methods the two materials were tested in the study. The nanostructured calcium aluminate was synthesized by the hydrothermal sol-gel method from individual components of calcium aluminate (CaOxAl2 O3 ), calcite (CaCO3 ) and barium sulfate (BaSO4 ) as radiocontrast agent in the ratio of 2:2:1 according to V. Jokanovic's recipe. The other used material was calcium silicate MTA Angelus (Londrina, Brazil). The antimicrobial effect was assessed using agar diffusion test. Standard strains of Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, cultured on blood Mueller-Hinton agar and Candida albicans cultivated on Sabouraud Dextrose Agar, were used as test microorganisms. Results the best antimicrobial effect after 24 h both materials showed against S. aureus. The mean values of the growth inhibition zone for ALBO MCCA were 5.7 ± 0.25 mm and MTA 6.2 ± 0.4 mm. The ALBO MCCA material showed slightly stronger antibacterial effect against E. coli compared to MTA (p < 0.05), whereas none of the materials showed antibacterial effect against E. faecalis. Conclusion the ALBO MCCA material showed certain antibacterial effect on Escherichia coli, Staphylococcus aureus and Candida albicans that was comparable to antibacterial effect of MTA.

Evaluation of Antibacterial Effect of Diode laser 980 nm, Triple Antibiotic Past, and Calcium Hydroxide on Enterococcus Faecalis Biofilm

Aim: The purpose of this study is to evaluate the anti-biofilm capacity of Diode laser 980 nm, triple antibiotic mixture and calcium hydroxide.Methods: Eighty five single-rooted teeth with mature apices were prepared using Protaper Universal rotary nickel titanium system till size # F4 then contaminated with E.faecalis. Irrigation done using 2.5% sodium hypochlorite followed by 17% EDTA. Samples were divided into 4 groups (n= 20) according to the irrigant activation method. Laser group,TAP group, Ca(OH)2group and the control group. Residual bacteria were plated onto Brain Heart Infusion media and determined as colony-forming units (CFU mL-1). Data were analyzed using one way ANOVA followed by performance of Tukey post hoc tests. Significance was set at p < 0.05.Results: There was a statistically significant reduction in the mean numbers of colony-forming units among all groups. However, none of the activation methods was able to kill E. faecalis biofilm completely. The Laser group behaved most effectively among all groups.Conclusion: The adjunctive use of 980nm laser is an effective method for bacterial reduction after chemo-mechanical instrumentation of the root canal.

Microbial Analysis of Endodontic Infections in Root-filled Teeth with Apical Periodontitis before and after Irrigation Using Pyrosequencing

IntroductionThe root canal microbiota in root-filled teeth with post-treatment apical periodontitis before and after chemomechanical instrumentation and irrigation with either 1% sodium hypochlorite (NaOCl) or 2% chlorhexidine digluconate were analyzed by using the pyrosequencing method. MethodsSamples from 10 root-filled teeth with apical periodontitis undergoing retreatment were taken before (S1) and after (S2) preparation using irrigation with either NaOCl (n = 5) or 2% chlorhexidine digluconate (n = 5). DNA was extracted, and the 16S rRNA gene (V3-V5) variable regions were amplified and subjected to pyrosequencing (GS junior 454) to determine the bacterial composition. ResultsPyrosequencing yielded 43,797 sequence reads in S1 and 9196 in S2 samples. Overall, 125 bacterial species belonging to 68 genera (S1, 59; S2, 38) and 9 phyla were found. The most abundant and prevalent phyla in S1 and S2 samples were Firmicutes, Fusobacteria, Bacteroidetes, and Actinobacteria. The most represented, abundant, and prevalent genera in S1 and S2 samples were Streptococcus and Fusobacterium. The most prevalent species in S1 and S2 samples were Fusobacterium nucleatum ss. vincentii, Streptococcus oralis/mitis, Streptococcus intermedius, and Streptococcus gordonii. The mean number of species per root canal was 20 (range, 4–37) in S1 and 9 (range, 4–15) in S2, respectively. ConclusionsA high interindividual diversity was observed in both S1 and S2 samples, with no difference between the two irrigation groups. F. nucleatum ss. vincentii and some Streptococcus species were the most prevalent species in pre-preparation and post-preparation samples during retreatment of root-filled teeth with infection.

EVALUATION OF ANTIBACTERIAL EFFECT OF DIODE LASER 980 NM, ENDOVAC AND PASSIVE ULTRASONIC IRRIGATION DURING FINAL IRRIGATION

Aim: The purpose of this study is to evaluate the antibacterial effect of Diode laser 980 nm, EndoVac and passive ultrasonic irrigation ex vivo. Methods: One hundred and five maxillary central incisors were standardized to 15mm in length. All samples were prepared using Protaper Universal rotary nickel titanium system till size # F4 then contaminated with E. faecalis. The irrigation protocol used was 2.5% sodium hypochlorite followed by 17% EDTA. Samples were randomly divided into 5 groups (n= 20) according to the irrigant activation method. LAI group, Diode laser 980nm. API group, EndoVac system. PUI group, passive ultrasonic activation. The positive control group, in which the irrigating solution was not activated and the negative control group in which the samples were not subjected to irrigation or activation. Residual bacteria were collected with sterile paper point, plated onto BHI media and incubated (37 °C, 48 h) to determine the colony-forming units (CFU mL-1). Data were analyzed using one-way ANOVA followed by performance of Tukey post hoc tests. Significance was set at p < 0.05. Scanning electron microscopy was used to investigate the changes in biofilm. Results: There was a statistically significant reduction in the mean numbers of colony-forming units among all groups. However, none of the activation methods was able to kill E. faecalis biofilm completely. The LAI group behaved most effectively among all groups.Conclusion: The adjunctive use of 980nm laser is an effective method for bacterial reduction after chemo-mechanical instrumentation of the root canal.

Influence of Taper of Root Canal Shape on the Intracanal Bacterial Reduction.

Objectives:Taper is a factor that determines final root canal dimensions and consequently, the space available for the cleaning action of irrigants. Therefore, the aim of this study was to investigate the influence of taper on intracanal bacterial reduction.Methods:Sterilized root canals of 25 mandibular incisors were inoculated with E. faecalis and then divided into two experimental groups and one control group (A= saline, B= NaOCl + EDTA and C= control, not prepared). Groups A and B were prepared to an apical size of #30/0.04, a culture was obtained and then prepared to #30/0.08 and cultured again. Final irrigation sequence was 30 ml of saline for group A and 10 ml of 17% EDTA followed by 10 ml of 2.5% NaOCl and 10 ml of saline for group B. The CFU ml-1 of the pre- and two post-operative samplings were recorded. Values were compared by performing ANOVA and FDR for multiple hypothesis testing.Results:No statistically significant difference between initial CFU ml-1 readings was recorded, whereas significant differences between group A and B at both 4% and 8% tapers were noted. Furthermore, a linear-dependent reduction of CFU ml-1 was recorded in each group from non-instrumented root canals to #30/0.04 and subsequently to #30/0.08. The positive control group shows the expected reduction of bacterial count.Conclusion:Chemomechanical instrumentation was more efficient at reducing E. faecalis when the taper of root canals increased from 4% to 8% and NaOCl plus EDTA led to a greater intracanal bacterial reduction than saline, regardless of the taper achieved.

Ultrastructural Analysis of the Surface of Endodontic Instruments after Immersion in Irrigating Solutions

Summary Introduction Separation (fracture) of endodontic instruments in the root canal during chemomechanical instrumentation is a complication that can compromise the final outcome of endodontic treatment. One of the most common factors that cause fatigue of endodontic instruments and consequent fracture is surface corrosion. The aim of this study was to investigate the ultrastructure of surface corrosion of endodontic instruments made of stainless steel and nickel-titanium after immersion in the most commonly used root canal irrigants. Material and Methods The study included 48 nickel-titanium and stainless steel endodontic hand files. All instruments were immersed in 5.25% sodium hypochlorite, 0.2% CHX and 17% EDTA. Surface corrosion was analyzed using a scanning electron microscope (SEM). Results Nickel-titanium instruments showed significantly higher susceptibility to corrosion after immersion in 5.25% sodium hypochlorite compared to stainless steel instruments (p&lt;0,001). After immersion in 0.2% CHX corrosion damage was observed on both nickel-titanium and stainless steel instruments but the difference was not statistically significant (p=0.096). No corrosion was observed in both types of instruments after immersion in 17% EDTA. Conclusion The use of 5.25% NaOCl and 0.2% CHX as root canal irrigating solutions can cause serious corrosion changes on the surface of nickel-titanium and stainless steel endodontic instruments.