|Year : 2019 | Volume
| Issue : 2 | Page : 61-70
Effect of autoclaving cycles on the surface topography of endodontic nickel-Titanium rotary files: A systematic review
Nikhil B Nighot, Anamika C Borkar, Soumya S Shetty, Nitika Tiwari, Sayali A Maral, Shruti Kamath
Department of Conservative Dentistry and Endodontics, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra, India
|Date of Submission||30-May-2019|
|Date of Acceptance||19-Jul-2019|
|Date of Web Publication||23-Dec-2019|
Dr. Nikhil B Nighot
Flat No. 29, Kishori Park, S. No. 38/A/1, Erandwana, Pune - 411 038, Maharashtra
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The surface topography of nickel-titanium (Ni-Ti) rotary files, after being exposed to a specific number of sterilization cycles in an autoclave, can cause surface changes in the file. Hence, the use of AFM and scanning electron microscopy would help to shed some light on the delicate balance between the action of steam sterilization and its reaction, in terms of topographical changes on the surface of the instrument, which could have implications in its clinical use. To analyze the effect of autoclave cycles on the surface topography of endodontic Ni-Ti rotary files. English-language articles were retrieved from electronic biomedical journal databases. PubMed, Google Scholar, and ResearchGate were used to complete the search for all full-text articles available. The search was done till September 30, 2018. The last data search was conducted on September 30, 2018. All articles that were published in English were included. Only those articles that were published between January 1, 2000, and September 30, 2018, comparing the effect of autoclaving cycles on the surface roughness of Ni-Ti rotary files, were included. Autoclave cycles. A total of 62 articles were identified through electronic database searching. After duplicate removal, and full-text reading, six articles qualified for qualitative synthesis in this systematic review. Autoclave sterilization causes an increase in the surface roughness of Ni-Ti files; the increase in roughness corresponds to the number of autoclave cycles that the instruments were exposed to.
Keywords: Atomic force microscope, autoclave cycles, nickel-titanium endodontic rotary files, scanning electron microscope, sterilization, surface roughness, surface topography
|How to cite this article:|
Nighot NB, Borkar AC, Shetty SS, Tiwari N, Maral SA, Kamath S. Effect of autoclaving cycles on the surface topography of endodontic nickel-Titanium rotary files: A systematic review. J Int Clin Dent Res Organ 2019;11:61-70
|How to cite this URL:|
Nighot NB, Borkar AC, Shetty SS, Tiwari N, Maral SA, Kamath S. Effect of autoclaving cycles on the surface topography of endodontic nickel-Titanium rotary files: A systematic review. J Int Clin Dent Res Organ [serial online] 2019 [cited 2020 Feb 17];11:61-70. Available from: http://www.jicdro.org/text.asp?2019/11/2/61/273755
| Rationale|| |
The advent of nickel-titanium (Ni-Ti) rotary files has revolutionized every aspect, sphere, and branch of dentistry. It has undergone a plethora of changes since its inception, both in formulation and application, to suit the varying needs of the profession. Nitinol is the name given to a family of intermetallic alloys consisting of nickel and titanium, which have been ascribed to have the properties of shape, memory, and superelasticity.
With the introduction of Ni-Ti rotary files into endodontic practice, the number of procedural errors during the preparation of root canals, as well as the total preparation time, has been reduced, as compared to when using hand files. Despite these advantages, Ni-Ti rotary files can fracture unexpectedly within root canals.
Infection control processes are essential parts of modern dentistry. Because endodontic instruments are in contact with blood and mucosa, they need to be sterilized before use. Sterilization should be carried out to remove all pathogenic organisms. Using autoclave is a common technique for sterilization of all files which can demolish all bacteria, spores, and viruses.
Because of high cost, rotary Ni-Ti files are frequently reused after autoclave sterilization. Autoclaving is important to minimize the risk of cross infection during endodontic treatment, which has been discussed in the literature., Despite this fact, no general agreement exists regarding the effect of repeated autoclave cycles on the surface of rotary Ni-Ti files.,,,
Surface corrosion could influence the mechanical properties of rotary Ni-Ti files and lead to undesirable fracture during root canal instrumentation.,,
However, due to thermal expansion and contraction processes, sterilization in autoclave can permanently deform the flutes and make all cutting tools dull. These surface changes can affect the properties of the file and result in unfavorable fracture of the instrument during root canal treatment. The surface changes of the file include flattened flutes, piled-up grooves, deformed tip, and corrosion. Should these changes occur, the file must be discarded. Research has shown that surface cracks and corrosion of the file can result in instrument fracture;,, hence, the surface quality of the file is important.
The topography of the surface affects the bulk properties and influences the behavior of a given material. Atomic force microscope (AFM) is part of a larger family of scanning probe microscopes. It works by probing the surface of the sample with a small tip attached to a cantilever. This process provides valuable data regarding the topography of the surface of the sample. The AFM is simple to use and can give detailed surface information even at the molecular level. The most commonly used parameters to describe the topographic characteristics of a surface using the AFM are the arithmetic mean roughness (AMR), the maximum height (MH), and the root mean square (RMS). These parameters describe the vertical amplitude of the surface topography.
Scanning electron microscope (SEM) is used for extensive structure analysis through secondary electron imaging and is an excellent technique for the analysis of surface characteristics. Martins et al. showed that the majority of the defects of endodontic files can be detected by SEM at high magnification.
The aim of this systematic review is to analyze the effect of autoclaving cycles on the surface topography of endodontic Ni-Ti rotary files.
What is the effect of autoclaving cycles on the surface topography of endodontic Ni-Ti rotary files?
To analyze the effect of autoclaving cycles on the surface topography of endodontic Ni-Ti rotary files.
- Articles published in English
- Articles published between January 1, 2000, and September 30, 2018
- In vitro studies
- Studies evaluating the effect of autoclaving cycles on the surface roughness of Ni-Ti rotary files.
- Review articles, case reports, abstracts, letters to editors, and editorials
- Studies which do not have an influencing or confounding factor.
The PICOS guidelines that were selected are as follows:
- P – Participants: Endodontic Ni-Ti rotary files
- I – Intervention: Autoclaving cycles
- C – Comparison: Nil
- O – Outcomes: Increase or decrease in the surface roughness of Ni-Ti rotary files due to autoclaving cycles
- S – Study design:In vitro study.
English-language articles were retrieved from electronic biomedical journal databases. PubMed, Google Scholar, and ResearchGate were used to complete the search for all the full-text articles available. The search was done till September 30, 2018.
The following databases were searched on: PubMed (the limits used were all full-text articles in English dated from January 1, 2000, to September 30, 2018) and Google Scholar. [Table 1] summarizes the terms used as keywords in several combinations for the electronic search strategy [Table 2].
Study selection process
In vitro and comparative studies were selected; however, only articles which describe the effect of various autoclaving cycles on the surface topography of Ni-Ti files were included. Using different search strategies from the above mentioned keywords [Table 1] and their combinations, various electronic databases were searched. A total of 62 articles were identified through the database searching. Out of the 62 articles, 44 articles were removed after the review of titles. These records were assessed for any duplicates, and ten articles were removed. After thorough reading of titles, eight articles were selected. These eight articles were further screened for abstract reading, two articles were excluded, and six were selected after reading the abstracts. Full texts for these six articles were obtained and were assessed for eligibility. All these six articles qualified and were selected. No exclusion was done after reading the full texts [Flowchart 1].
Data collection process
Data collection process was done according to the consultation approved from our expert. First, a pilot Microsoft Excel Sheet [Table 3] was filled accordingly, and then the expert was consulted for further progress. According to the data collected and the records selected, the remaining Excel sheet was filled only with the data that were related to this study and retained.
The headings under which the data were tabulated are study ID where the number of studies that were selected was mentioned number wise. Various articles were included and the name of the author and location as important factors. Year of publication of the studies were taken into account to mention and specify the fixed time interval of the study. Study design was mentioned to specify the type of study design, for example, whether the study was in vitro, ex vivo, or in situ. Population/products were included, and this comprised endodontic Ni-Ti rotary files. Intervention/exposure was the autoclaving cycles. Conclusion was mentioned according to the study's protocol and in the author's original words. Remark was expressed by the author of this systematic review.
In many areas of medicine, the amount of published information is increasing at an exponential rate, making it difficult for the clinician to condense the data to a manageable amount of valuable and useful information. Systematic reviews have been suggested as a remedy for this information overload. Such reviews are regarded as the highest level of evidence. Certain statistical methods, for example meta-analysis, have also been introduced for the calculation of a more comprehensive summation of the compiled results from studies with small sample sizes. These findings would then serve as an authoritarian guide for evidence-based practice.
Thus, conducting systematic reviews may provide reliable results that can be used for clinical decision-making, especially when it is possible to perform a meta-analysis. This systematic review aimed to identify, evaluate, and synthesize allin vitro studies that met the prespecified eligibility criteria to answer the following research question: “What is the effect of autoclaving cycles on the surface topography of endodontic Ni-Ti rotary files?”
| Summary of Evidence|| |
Nair et al., 2015, conducted a study to observe the effect of multiple autoclave sterilization cycles, on the surface of Ni-Ti files. The file used for this study was the Mtwo file (VDW, Munich, Germany) and ProTaper (Dentsply, Tulsa, Oklahoma). The apical 5-mm files were attached to a silicon wafer and subjected to autoclave cycles under standardized conditions. They were scanned with an AFM after 1, 5, and 10 cycles. The unsterilized files were used as control, before the start of the study. Three vertical topographic parameters, namely MH, RMS of surface roughness, and AMR, were measured with the atomic force microscope (AFM). Analysis of variance (ANOVA) along with Tukey's test was used to test the differences. The vertical topographic parameters were higher for both the files, right after the first cycle, when compared with the control (P < 0.01). The surface roughness increased sharply for Mtwo when compared to ProTaper, although ProTaper had a rougher surface initially. The study confirmed that the irregularities present on the surface of the file became more prominent with multiple autoclave cycles, a fact that should be kept in mind during their reuse.
Razavian et al., 2016, conducted a study to evaluate the effect of autoclave cycles on the surface characteristics of S-File by SEM. 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, one autoclave cycle, five autoclave cycles, and ten autoclave cycles) by SEM under ×200 and ×1000 magnifications. Data were analyzed using the SPSS software (SPSS version 20.0, SPSS, Chicago, IL, USA) and the paired sample t-test, independent sample t-test, and multifactorial repeated-measures ANOVA. The level of statistical significance was set at 0.05. 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). They concluded that sterilization by autoclave increased the surface roughness of the files, and this was directly related to the number of autoclave cycles.
Valois et al., 2008, conducted a study to evaluate the surface roughness of rotary Ni-Ti files after multiple autoclave cycles. Two different types of rotary Ni-Ti files (Greater Taper and ProFile) were attached to a glass base. After 1, 5, and 10 autoclave cycles, the files were positioned in the AFM. The analyses were performed on 15 different points. The same files were used as control before any autoclave cycle. The following vertical topographic parameters were measured: AMR, MH, and RMS. The differences were tested by ANOVA with Tukey's test. All topographic parameters were higher for both Greater Taper and ProFile after ten cycles compared with the control (P < 0.05). ProFile also showed higher topographic parameters after five cycles when compared with the control (P < 0.05). The results indicated that multiple autoclave cycles increase the depth of surface irregularities located on rotary Ni-Ti files.
Yamazaki-Arasaki et al., 2012, conducted a study to make a comparative evaluation of the surface topography of the cervical third of four different rotary systems, before and after being used twelve times, in 1.440 resin blocks with simulated root canals with standardized 458 curvatures, and they were analyzed by AFM. The blocks were divided into the following four groups and were prepared according to the manufacturer's recommendations: Group 1 – K31; Group 2 – ProTaper Universal1; Group 3 – Twisted files 1; and Group 4 – Biorace 1. After each preparation, the instruments were washed and autoclaved. A total of 240 instruments were selected, with 30 being new instruments and 30 after having been used for the 12th time, from each group. These instruments were analyzed by AFM and for quantitative evaluation, the mean RMS values of the cervical third of the specimens from the four groups were used. The result showed that all the rotary files used for the 12th time suffered wear with change in the topography of the cervical region of the active portion of the file (ANOVA, P < 0.01). Classifying the specimens in increasing order, from the least to the greatest wear suffered, Group 3 (2.8993 nm) presented the least wear, followed by Group 4 (12.2520 nm), Group 1 (36.0043 nm), and lastly, Group 2 (59.8750 nm) with the largest amount of cervical surface wear.
Spagnuolo et al., 2012, conducted a study to evaluate the effects of repeated autoclave sterilization cycles on the surface topography of conventional Ni-Ti and titanium nitride (TiN)-coated rotary instruments. A total of sixty Ni-Ti rotary instruments, thirty ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) and thirty TiN-coated AlphaKite (GmbH & Co. KG, Gebr. Brasseler, Germany), were analyzed. The instruments were evaluated in the as-received condition and after 1, 5, and 10 sterilization cycles. After sterilization, the samples were observed using scanning electron microscope (SEM), and surface chemical analysis was performed on each instrument with energy-dispersive X-ray spectroscopy (EDS). Moreover, the samples were analyzed by atomic force microscopy (AFM), and roughness average (Ra) and RMS value of the scanned surface profiles were recorded. Data were analyzed by means of ANOVA followed by Tukey's test. Scanning electron microscopy observations revealed the presence of pitting and deep milling marks in all the instruments. EDS analysis confirmed that both types of instruments were composed mainly of Ni-Ti, while AlphaKite had additional nitride. After multiple autoclave sterilization cycles, SEM examinations revealed an increase in surface alterations, and EDS values indicated changes in chemical surface composition in all instruments. Ra and RMS values of ProTaper significantly increased after five (P = 0.006) and ten cycles (P = 0.002) with respect to the as-received instruments, whereas AlphaKite showed statistically significant differences compared with the controls after ten cycles (P = 0.03). They concluded that multiple autoclave sterilization cycles modified the surface topography and chemical composition of the conventional and TiN-coated Ni-Ti rotary instruments.
Yılmaz et al., 2018, conducted a study to compare the effect of autoclave cycles on the surface topography and roughness of HyFlex CM, Coltène Whaledent, Switzerland and HyFlex EDM, Coltène Whaledent, Switzerland instruments using atomic force microscopy (AFM) analysis. Eight new files of each brand were subdivided into four subgroups (n = 2/each subgroup). One group was allocated as the control group and was not subjected to autoclave sterilization. The other three groups were subjected to different numbers (1, 5, and 10) of autoclave sterilization cycles. After the cycle, the instruments were subjected to AFM analysis. Ra and RMS values were chosen to investigate the surface features of endodontic files. The data were analyzed using one-way ANOVA and post hoc Tamhane tests at 5% significance level. The lowest Ra and RMS values were observed in the HyFlex EDM files that served as the control and in those subjected to a single cycle of autoclave sterilization (P < 0.05). The highest Ra and RMS values were observed in the HyFlex CM and HyFlex EDM files that were subjected to ten cycles of autoclave sterilization (P < 0.05). The surface roughness values of the HyFlex CM group showed a significant increase after ten autoclave cycles, whereas those of the HyFlex EDM group exhibited a statistically significant change after five autoclave cycles (P < 0.05). They concluded that although the initial surface roughness values of the HyFlex EDM files were lower than those of the HyFlex CM files, the surface roughness values of the EDM files showed a statistically significant increase after five cycles of autoclave sterilization. In contrast, the surface roughness values of the HyFlex CM files did not increase until ten cycles of autoclave sterilization. The present study indicated that autoclave sterilization negatively affected the surface roughness of the tested Ni-Ti files.
The studies did not include different protocols of sterilization. Different modes of sterilization on different file systems will increase the impact of the study.
| Conclusion|| |
Autoclave sterilization causes an increase in the surface roughness of Ni-Ti files.
The increase in roughness corresponds to the number of autoclave cycles that the instruments were exposed to.
| Future Implications|| |
In order for thein vitro studies to translate into meaningful data for a clinician, the studies themselves have to be standardized and the data should include the effect of other sterilizing agents on the surface of Ni-Ti rotary files. Furtherin vitro and microscopic studies are required to find out the effect of autoclaving cycles on different files depending on their surface treatments.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]