A SEM evaluation of debris removal from endodontic files after cleaning and steam sterilization procedures

A SEM/EDS evaluation of debris removal of used rotary Ni-Ti endodontic files by four different cleaning solutions

Purpose

The aim of this study was to compare the efficacies levels of four cleaning solutions for removing debris from rotary Nickel-Titanium (Ni-Ti) endodontic instruments.

Materials and methods

Twelve instruments that fractured during ex vivo instrumentation were used. Fractured surfaces were investigated by SEM before and after 3, 6 and 9 min of ultrasonic cleaning in 17 % EDTA.3NaOH (Group A), 2.5 % NaOCl (Group B), Dentasept 3H Rapide (Group C) and ZymeX™ (Group D) solutions. EDS analyses of selected files from all four groups of untreated and ultrasonically cleaned samples were performed to assess the elemental composition of the alloy surfaces.

Results

SEM analysis revealed that after 9 min of ultrasonic agitation, all four investigated solutions had cleaned fractured surfaces. However, some low-atomic-number regions exhibited random distributions on the fractured surfaces. EDS analyses indicated that only C was retained on surface after 9 min of ultrasonic cleaning. This finding was common in all tested groups.

Conclusions

All four investigated solutions substantially removed debris from the surfaces of the Ni-Ti files and were considered appropriate for clinical practice.

Validating cleanability of dental rotary diamond instruments soiled with 2 clinically relevant dental test soil components

BACKGROUND

The aim of this study was to produce a dental test soil, with 2 clinically relevant soil components, to be quantified for cleaning process validation. Another goal was to soil diamond instruments with the 2 soil components and validate the efficacy of cleaning instructions, developed and detailed in this study, using both qualitative and quantitative techniques.

METHODS

To simulate worst-case clinical use conditions, the authors used each soiled instrument to prepare a 9-millimeter-deep access cavity on a noncarious extracted molar. Afterward, the authors applied a mixture of pooled human saliva and blood test soil to each instrument and air-dried it for 30 minutes. The authors cleaned each instrument using documented multistep cleaning instructions, which were then validated via both qualitative and quantitative assessment of protein and enamel-dentin residues using spectrophotometric analysis and microscopy images.

RESULTS

After thorough cleaning, neither protein nor enamel-dentin residues were found at quantifiable levels (spectrophotometric analysis) on the soiled and cleaned diamond instruments, which was qualitatively verified (microscopy images).

CONCLUSIONS

The results of this study show the successful development of a dental test soil with 2 clinically relevant soil components. Furthermore, using these soil components as test markers, the authors found that when the established cleaning instructions are properly followed, a soiled diamond instrument can be cleaned in a quantifiable manner.

PRACTICAL IMPLICATIONS

Thorough cleaning is a critical step in reprocessing multiuse dental instruments. In accordance with US Food and Drug Administration guidance, the described process for quantification of soil components, using 2 clinically relevant soil markers, on cleaned diamond instruments can be helpful to dental instrument manufacturers in the development and validation of cleaning instructions for their reusable instruments.

Management of Instrument Sterilization Workflow in Endodontics: A Systematic Review and Meta-Analysis

Endodontic treatment consists of different working procedures, such as the isolation of the operating field, pulp chamber access, and cleaning and shaping phases with at last the need of a three-dimensional filling of the canals. Each step requires a series of single-use or sterilizable instruments. We have performed a systematic review of different sterilization and disinfection procedures aiming at drawing up a disinfection and sterilization procedure to be used on endodontic instruments. A search on PubMed and Scopus was carried out using the following keywords: “endodontic sterilization,” “endodontic autoclave,” “decontamination dental bur,” “sterilization dental burs,” and “gutta-percha points sterilization.” Eligible articles were included in the qualitative and quantitative analysis. Results of the meta-analysis showed that the most effective method in sterilization is autoclaving. The qualitative analysis showed that the use of single-use or first-use instruments requires presterilization or sterilization procedures, and for reusable tools, attention must be paid to the removal of debris deposited on the blades, not easy to remove manually.

Effect of Intraoral Aging on Debris Accumulation and Friction of First Molar Tubes

AIM

The aim of this article was to evaluate the impact of intraoral aging and site specificity on debris accumulation and friction in molar tubes after intraoral use.

MATERIALS AND METHODS

A total of 80 intraorally used first molar convertible tubes were provided by 20 orthodontic adolescent patients after 6 months of treatment. The specimens were divided into eight groups (n = 10) according to the mouth quadrant and the type of examination [four groups of ten tubes for scanning electron microscope (SEM) and four groups of ten tubes for friction test]. Scanning electron microscope examination was performed after opening the convertible caps and friction test was executed using a 0.019'' × 0.025'' stainless steel wire, which was inserted in the tubes belonging to each group. The Mann-Whitney test, analysis of variance (ANOVA), and Bonferroni tests were performed for statistical analysis at 0.01 level of significance.

RESULTS

There was a significant increase in the amount of debris and frictional force after 6 months of intraoral exposure (p < 0.0001). Debris scores were higher (10% increase) on the upper tubes when compared with the lower ones, with no statistical difference. Mean frictional force ranged from 0.22 to 0.26 N according to the mouth quadrant, but the difference between groups was also not significant.

CONCLUSION

After 6 months of intraoral exposure, there was a significant increase in the amount of debris in the first molar tube slots, leading to significantly higher frictional forces during sliding mechanics. The influence of site specificity on the amount of debris and on frictional forces of the first molar tubes could not be demonstrated.

CLINICAL SIGNIFICANCE

Molar tubes should be cleaned, before and during sliding mechanics, in order to minimize friction.

Effect of Autoclave Cycles on Surface Characteristics of S-File Evaluated by Scanning Electron Microscopy

Introduction:

Presence of surface defects in endodontic instruments can lead to unwanted complications such as instrument fracture and incomplete preparation of the canal. The current study was conducted to evaluate the effect of autoclave cycles on surface characteristics of S-File by scanning electron microscopy (SEM).

Methods and Materials:

In this experimental study, 17 brand new S-Files (#30) were used. The surface characteristics of the files were examined in four steps (without autoclave, 1 autoclave cycle, 5 autoclave cycles and 10 autoclave cycles) by SEM under 200× and 1000× magnifications. Data were analyzed using the SPSS software and the paired sample t-test, independent sample t-test and multifactorial repeated measures ANOVA. The level of significance was set at 0.05.

Results:

New files had debris and pitting on their surfaces. When the autoclave cycles were increased, the mean of surface roughness also increased at both magnifications (P<0.05). Moreover, under 1000× magnification the multifactorial repeated measures ANOVA showed more surface roughness (P<0.001).

Conclusion:

Sterilization by autoclave increased the surface roughness of the files and this had was directly related to the number of autoclave cycles.

Sterilization of rotary NiTi instruments within endodontic sponges

AIM

To determine whether the following can be sterilized by autoclaving - endodontic sponges, rotary nickel-titanium (NiTi) instruments within endodontic sponges, and rotary NiTi instruments with rubber stoppers.

METHODOLOGY

Sixty-four samples of eight different endodontic sponges (n = 512) were placed into brain heart infusion broth (BHI) for 72 h. An aliquot of this was then spread onto horse blood agar and cultured aerobically and anaerobically to test sterility at purchase. Bacterial suspensions of Enterococcus faecalis, Porphyromonas gingivalis and Geobacillus stearothermophilus in BHI were used to contaminate sterile sponges and rotary NiTi instruments (with and without rubber stoppers) inserted into sponges. The various samples were autoclaved and then cultured aerobically and anaerobically. Success of sterilization was measured qualitatively as no growth. The experiment was repeated with clinically used rotary NiTi instruments (n = 512). All experiments were conducted in quadruplicate.

RESULTS

No sponges on purchase had microbial growth when anaerobically cultured but some did when aerobically cultured. All autoclaved sponges and instruments (within or without sponges, and with or without rubber stoppers) were associated with no microbial growth. All nonautoclaved positive control samples showed microbial growth.

CONCLUSIONS

Autoclaving was effective in the sterilization of sponges and endodontic instruments. Endodontic sponges should be autoclaved before clinical use. For clinical efficiency and cost-effectiveness, rotary NiTi instruments can be sterilized in endodontic sponges without removal of rubber stoppers.

Efficacy of Needle, Ultrasonic, and Endoactivator Irrigation and Photon-Induced Photoacoustic Streaming in Removing Calcium Hydroxide from the Main Canal and Isthmus: An In Vitro Micro-Computed Tomography and Scanning Electron Microscopy Study

OBJECTIVE

The aim of this in vitro study was to use high-resolution micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to compare the efficacy of four irrigation techniques [needle, ultrasonic, EndoActivator, and photon-induced photoacoustic streaming (PIPS)] in removing calcium hydroxide (Ca[OH]2) from the root canal and isthmus of maxillary premolars.

METHODS

Twenty-four maxillary first premolars were selected based on the presence of isthmus regions on micro-CT scans. Root canals were instrumented with an F2 file using ProTaper rotary instruments and filled with Ca(OH)2 paste. Samples were stored at 37°C and 100% humidity for 1 week and randomly divided into four groups (n=6 each), according to irrigation technique. Samples were scanned with micro-CT before instrumentation, after Ca(OH)2 filling, and after irrigation. Ca(OH)2 reduction in the coronal, middle, and apical thirds and in the isthmus were assessed with three-dimensional image analysis. Next, specimens were split longitudinally, and canal walls were examined with SEM for Ca(OH)2 residues. Data were statistically evaluated with the Kruskal-Wallis and Mann-Whitney tests (p=0.05).

RESULTS

The PIPS and ultrasonic groups showed greater Ca(OH)2 reduction in the apical third and higher cleanliness of the isthmus than the EndoActivator and needle irrigation groups (p<0.05). Ca(OH)2 residue scores in the PIPS and ultrasonic groups were significantly lower than those in the EndoActivator and needle groups in all regions of the root canals (p<0.05). There was no significant difference between PIPS and ultrasonic groups (p>0.05), or between EndoActivator and needle groups (p>0.05).

CONCLUSIONS

PIPS and ultrasonic irrigation more effectively removed Ca(OH)2 from the main canal and isthmus in maxillary premolars than did EndoActivator or needle irrigation.

Archwire cleaning after intraoral ageing: the effects on debris, roughness, and friction

Dental material science has paid more attention to mechanical properties of as-received materials than to changes produced after intraoral exposure. Orthodontic archwires when exposed to the intraoral environment have shown a significant increase in the degree of debris, surface roughness (Ra), and frictional force. The purpose of this split-mouth study was to evaluate the effects of two methods of archwire cleaning on these variables after clinical use for 8 weeks. For eight individuals, four sets of three brackets each (n = 32) were bonded from the first molar to the first premolar. A passive segment of 0.019 × 0.025 inch stainless steel (SS) archwire was inserted into the brackets and tied by elastomeric ligature. Debris level [via scanning electron microscopy (SEM)], Ra, and frictional force were evaluated in a paired comparison after 8 weeks of intraoral exposure and after cleaning with a steel wool sponge (SWS) for 1 minute or ultrasound (US) cleaning for 15 minutes. Kruskal-Wallis, Friedman's, and Spearman and Pearson correlation tests were used for statistical analysis. The debris and Ra of SS rectangular wires increased significantly (P < 0.05) during clinical use, causing a significant increase in the frictional force level. These changes can be effectively eliminated by either of the investigated cleaning methods, although a SWS seems to be clinically more practical.

Debris, roughness and friction of stainless steel archwires following clinical use

OBJECTIVE

To investigate the degree of debris, roughness, and friction of stainless steel orthodontic archwires before and after clinical use.

MATERIALS AND METHODS

For eight individuals, two sets of three brackets (n = 16) each were bonded from the first molar to the first premolar. A passive segment of 0.019- x 0.025-inch stainless steel archwire was inserted into the brackets and tied by elastomeric ligature. Debris level (via scanning electron microscopy), roughness, and frictional force were evaluated as-received and after 8 weeks of intraoral exposure. Mann-Whitney, Wilcoxon signed-rank, and Spearman correlation tests were used for statistical analysis at the .05 level of significance.

RESULTS

There were significant increases in the level of debris (P = .0004), roughness of orthodontic wires (P = .002), and friction (P = .0001) after intraoral exposure. Significant positive correlations (P < .05) were observed between these three variables.

CONCLUSION

Stainless steel rectangular wires, when exposed to the intraoral environment for 8 weeks, showed a significant increase in the degree of debris and surface roughness, causing an increase in friction between the wire and bracket during the mechanics of sliding.

A systematic method for predetermined scanning electron microscope analysis in dental science

Scanning electron microscope evaluation could be criticized if the method adopted to correct for bias is not specified in the study design. Observers can draw conclusions from images unconsciously chosen to best support their research hypotheses, impairing the basic research principle of operator's impartiality. In this study, a systematic observation method has been described and verified for repeatability. The number and the observation points on a certain specimen have been predetermined using a scheme along with observation rules previously established in the research protocol. When our instrument is used at an operating magnification between 500x and 1,000x (corresponding to a frame of 250x190 micro and 120x90 micro, respectively), the method allowed 100% repeatable observation frames, with linear frame errors in finding an observation point of 12.5% in length and 16.8% in height. With modifications to accommodate research objective and statistical requirements, the method could be applied to many SEM observation study.

Regenerating titanium ventricular assist device surfaces after gold/palladium coating for scanning electron microscopy

Titanium is one of the most commonly used materials for implantable devices in humans. Scanning electron microscopy (SEM) serves as an important tool for imaging titanium surfaces and analyzing cells and other organic matter adhering to titanium implants. However, high-vacuum SEM imaging of a nonconductive sample requires a conductive coating on the surface. A gold/palladium coating is commonly used and to date no method has been described to "clean" such gold/palladium covered surfaces for repeated experiments without etching the titanium itself. This constitutes a major problem with titanium-based implantable devices which are very expensive and thus in short supply. Our objective was to devise a protocol to regenerate titaniumsurfaces after SEM analysis. In a series of experiments, titanium samples from implantable cardiac assist devices were coated with fibronectin, seeded with cells and then coated with gold/palladium for SEM analysis. X-ray photoelectron spectroscopy spectra were obtained before and after five different cleaning protocols. Treatment with aqua regia (a 1:3 solution of concentrated nitric and hydrochloric acid), with or without ozonolysis, followed by sonication in soap solution and sonication in deionized water, allowed regenerating titanium surfaces to their original state. Atomic force microscopy confirmed that the established protocol did not alter the titanium microstructure. The protocol described herein is applicable to almost all titanium surfaces used in biomedical sciences and because of its short exposure time to aqua regia, will likely work for many titanium alloys as well.

[The investigation of ultrasound efficacy in cleaning the surface of new endodontic instruments]

INTRODUCTION

Active parts and tips of various new stainless steel and nickel-titanium endodontic instruments can be coated with fragments or metal residues, which can become detached during endodontic treatment. These fragments may obstruct the root canals or even reach the periapical tissue during biomechanical preparation and should be removed before clinical use.

OBJECTIVE

The aim of this study was to evaluate the presence of metal residues on both new stainless steel and nickel-titanium endodontic instruments, and to determine the cleaning efficacy of ultrasound using distilled water or disinfectant solution for removing these residues.

METHODS

Forty-eight stainless steel and nickel-titanium instruments were carefully removed from their original packages with dental tweezers, in order to avoid any contact with the cutting flutes and tips. The instruments were evaluated in term of metal debris presence, using scanning electron microscopy (SEM) and x-ray energy-dispersive spectroscopy (EDS). The instruments were then removed from the electron microscopy analysis stubs and placed in an ultrasonic bath for 15 minutes at a frequency of 28 kHz, using distilled water or disinfectant solution. The surfaces of the instruments were re-evaluated after cleaning.

RESULTS

Before ultrasound cleaning, a larger amount of metal debris was observed on the nickel-titanium endodontic instruments when compared to those made of stainless steel. The presence of metal particles on the instruments was evaluated by using EDS analysis. The use of ultrasound was effective in removing the metal residues from both types of endodontic instrument surfaces.

CONCLUSION

The use of ultrasound proved to be an efficient method for the removal of metal particles from the surface of new stainless steel and nickel-titanium endodontic instruments.

Influence of Usage History, Instrument Complexity, and Different Cleaning Procedures on the Cleanliness of Blood-Contaminated Dental Surgical Instruments

Our study assessed the factors that influence the resistance of blood residues on dental surgical instruments to washer-disinfector-based cleaning procedures in a clinical setting. The use of 2 additional cleaning methods—presoaking and scrubbing by hand—and the use of newer and/or less structurally complex instruments significantly increased the efficacy of washer-disinfector cleaning.

Effect of Prion Decontamination Protocols on Nickel-Titanium Rotary Surfaces

Decontamination of instruments is a prerequisite for their potential reuse but may affect surface integrity. Hence, the effect of prion removal protocols on 7 brands of nickel-titanium files was investigated. Baseline debris scores were determined under magnification after staining with van Gieson's solution. After shaping root canals in vitro, rotaries were mechanically and ultrasonically cleaned followed by immersion for 24 hours in 2 M sodium hydroxide (NaOH), 6 M CH(5)N(3), or 3% sodium hypochlorite (NaOCl); control files were stored dry. After sterilization, files were again stained and evaluated. Two of seven file brands demonstrated significantly higher baseline debris scores compared to final scores. Uniformly, debris could not be completely removed; there were no significant differences among groups. After immersion in NaOCl, 27.8% of instruments showed corrosion; however, no deterioration after immersion in the other solutions was found in the other groups. Regarding corrosion, no significant difference was found between brands. Based on these findings, single use of nickel-titanium rotaries appears beneficial.

Debris retention and wear in three different nickel-titanium rotary instruments

The aim of this in vitro study was to compare three nickel-titanium (Ni-Ti) rotary instruments: EndoWave, K3 and ProFile, with respect to their debris retention and wear. Thirty simulated root canal models made from resin blocks with 40 degrees canal curvature were used. They were divided into three groups of 10 samples each; EndoWave, K3 and ProFile were used in Groups A, B and C respectively. They were prepared with four serial size files. The weight of each file was measured to evaluate debris retention and wear at four representative time points: prior to root canal preparation (W1), immediately after root canal preparation (W2), after ultrasonic cleaning (W3), after further additional cleaning (W4). The weight of debris on each file after root canal instrumentation and ultrasonic cleaning was calculated as D1: (W2 - W4) and D2: (W3 - W4) respectively. Also, wear of the file was calculated as WF: (W1 - W4). There was a significant difference in the amount of debris remaining on the file among the three files; EndoWave retained more debris (D1) than K3 and ProFile (P < 0.001, one-way anova). ProFile had the largest amount of debris (D2) remaining after ultrasonic cleaning (P < 0.001). Wear was not detectable in this study. Under the conditions of this study, immediately after root canal preparation, EndoWave retained the largest amount of debris, while ProFile retained the most debris even after ultrasonic cleaning.

Rotary NiTi Instrument Fracture and its Consequences

The fracture of endodontic instruments is a procedural problem creating a major obstacle to normally routine therapy. With the advent of rotary nickel-titanium (NiTi) instruments this issue seems to have assumed such prominence as to be a considerable hindrance to the adoption of this major technical advancement. Considerable research has been undertaken to understand the mechanisms of failure of NiTi alloy to minimize its occurrence. This has led to changes in instrument design, instrumentation protocols, and manufacturing methods. In addition, factors related to clinician experience, technique, and competence have been shown to be influential. From an assessment of the literature presented, we derive clinical recommendations concerning prevention and management of this complication.

An Energy-Dispersive X-ray Analysis And SEM Study Of Debris Remaining On Endodontic Instruments After Ultrasonic Cleaning And Autoclave Sterilization

This study was carried out to investigate metallic and non-metallic debris remaining on endodontic files after ultrasonic cleaning and autoclave processing. Forty-eight unused rotary and hand endodontic files, including eight different brands, were tested. Instruments were cleaned with ultrasound, autoclaved and before and after each step were observed by scanning electron microscopy (SEM). Adherent debris was analysed by energy-dispersive X-ray analysis (EDXA). All of the instruments before ultrasound cleaning were contaminated with metallic and non-metallic debris. Although most non-metallic debris was removed by ultrasonic cleaning, most of the metallic debris remained even after the final step of sterilization.

Microbiological evaluation of endodontic files after cleaning and steam sterilization procedures

BACKGROUND

Infection control procedures are essential for modern dental practice and they are continually evolving to meet the dental profession's high standards. The present study evaluated the efficacy of two cleaning procedures to reduce bacterial numbers on endodontic files, and evaluated the effect of biological debris on the subsequent sterilization of files.

METHODS

Stainless steel and nickel-titanium (NiTi) files were examined upon removal from the manufacturer's packaging, after instrumentation in root canals of human teeth inoculated with a broth containing two anaerobic species and one facultative anaerobic species of bacteria, and after instrumentation and cleaning with either an ultrasonic bath or a thermal disinfector. For each file, the bacterial numbers were quantified using routine microbiological techniques in an anaerobic chamber.

RESULTS

No bacteria were detected from files direct from their packets. The size, taper and type of file did not affect the ability of either of the cleaning procedures to reduce bacterial numbers. However, an absence of bacteria was more likely when files were cleaned in the thermal disinfector. No bacteria were detected from files that were-subjected to steam sterilization irrespective of the type of prior cleaning procedure.

CONCLUSIONS

Steam sterilization eliminated all bacteria from the endodontic files irrespective of the presence of biological debris. The majority of bacteria were eliminated from endodontic files after either ultrasonic cleaning or using a thermal disinfector.