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

Presence and Causes of Sterilization Equipment Failures with Biological Indicators in Dental Offices in Mexico: A Longitudinal Cohort

Background/Objectives: Sterilization in dental practice is crucial for infection prevention. The aim of this study was to identify the presence and causes of bacterial growth using biological indicators in dental sterilization equipment in San Luis Potosí, S.L.P., Mexico, with different consecutive measurements over a year. Methods: This longitudinal cohort, conducted from January 2022 to January 2024 in San Luis Potosí, Mexico, aimed to identify the presence and causes of bacterial growth in dental sterilization equipment using biological indicators. A total of 207 dental offices were approached, and 175 participated, providing data through questionnaires and monitoring sterilization cycles with BIs. The checks were bimonthly for one year, with a total of six checks. Results: (a) An 11% (n = 1188) incidence of bacterial growth was observed, with a higher percentage in dry heat equipment (13%). (b) Upon analyzing the six consecutive verifications over a year, no statistically significant differences were observed in the failures of the sterilization cycles when comparing the two pieces of equipment. (c) Error in temperature and time of the equipment (OR = 4.0, 95% CI = 1.6-3.9, p = 0.0001) was significantly associated with the presence of bacterial growth during the one-year period. Conclusions: Monitoring sterilization cycles and identifying the causes of bacterial growth with different consecutive verifications decreased the presence of bacterial growth (failures) during the one-year period.

Microbiological evaluation of ultraviolet C light-emitting diodes for disinfection of medical instruments

Background

Despite the many guidelines for reprocessing of medical instruments, challenges persist such as microbial resistance to biocides, corrosive effects on materials, and time-consuming reprocessing procedures. Ultraviolet (UV) C light-emitting diode (LED) chambers might provide a solution but the integration in healthcare is still in its infancy. Here, we evaluated the efficacy of a novel ZAPARAY™ UVC LED chamber as a time and energy-efficient alternative for reprocessing of medical instruments for which current disinfection protocols exhibit limitations.

Methods

We verified the disinfection efficacy of the UVC LED chamber on a Petri dish and contaminated several medical devices with Staphylococcus aureus ATCC 25923. The bacterial reduction was assessed after 5 min of UVC LED exposure. Additionally, we investigated the impact of rinsing before UVC exposure.

Results

We demonstrated a bacterial reduction of 9 log10 on a Petri dish. Non-rinsed dental tools exhibited varied reduction levels ranging from a 3.23 log10 to a 6.25 log10 reduction. Rinsing alone yielded an average reduction of 2.7 log10 and additional UVC exposure further reduced the bacterial load by an average of 3.65 log10. We showed an average 4.90 log10 reduction on thermistors, 2 log10 or less on orthodontic pliers, and no reduction on handpieces.

Conclusions

This study demonstrates that UVC LED chambers may be used as a standardized substitute for specific (manual) disinfection procedures of certain medical devices, offering a time-efficient and more sustainable alternative. However, its use should be preceded by efficacy testing for each specific type of instrument.

Effect of simulated clinical use and sterilization on the cyclic fatigue resistance of nickel titanium files

Aim

Assess the effect of simulated clinical use and sterilization on the cyclic fatigue resistance of Race Evo and Tia Tornado Blue nickel titanium (NiTi) files.

Materials and Methods

For this study, a total of sixty-four NiTi files were selected, with thirty-two files each from two different manufacturers. Files from each manufacturer were subdivided into four subgroups (n = 8) based on the test parameters. The control groups included files that were neither used nor sterilized. Files from the test groups were used to prepare the root canals of extracted mandibular premolars and then sterilized. This procedure was repeated once, twice, or thrice, depending on the test group. All files were then subjected to a cyclic fatigue test. Data was statistically analyzed using the Kruskal-Wallis and Mann-Whitney U tests.

Results

No significant difference was observed in the number of cycles to failure (NCF) among the subgroups for both types of files (P = 0.869 for Tia Tornado Blue, P = 0.626 for Race Evo). Tia Tornado Blue files displayed significantly higher NCF values in the control (P = 0.021), once (P = 0.027), and thrice (P = 0.031) usage groups when compared to Race Evo files.

Conclusions

Repeated clinical use and sterilization for up to three cycles did not affect the cyclic fatigue resistance of Race Evo and Tia Tornado Blue files.

In Vitro Evaluation of the Dynamic Cyclic Fatigue Resistance of a New TruNatomy Glider File after Different Cycles of Use

INTRODUCTION

Determination of the glide path is recommended before using rotary instruments. This study aimed to evaluate the dynamic cyclic fatigue resistance of new and used glider rotary instruments in up to 6 root canals.

METHODS

Seventy-two TruNatomy Glider files were used for the preparation of root canals of extracted lower molars, which were then submitted to the dynamic cyclic fatigue test carried out in a curved metallic artificial canal. The instruments were divided into 4 groups (n = 18): Control group, new instruments without any use in the root canal; Group 2U, instruments used in 2 mesial canals; Group 4U, instruments used in 4 mesial canals; Group 6U, instruments used in 6 mesial canals. The time to failure (TF) of the instrument was recorded, and the number of cycles to failure (NCF) was calculated. The data were submitted to 1-way analysis of variance and to the Games-Howell test for multiple comparisons, adopting a significance level of 5%.

RESULTS

TF and NCF were significantly affected by the number of file uses. The Games-Howell test revealed that TF and NCF were significantly greater in the control group than in Group 4U. In Group 2U, TF and NCF were intermediate and not significantly different from the control group. Group 6U had significantly lower TF and NCF than all other groups.

CONCLUSION

The TruNatomy Glider can be used as a glide path for up to 2 mesial canals of mandibular molars, whereas its use on 4 or 6 root canals is not suggested.

Influence of Multiple Sterilization on Performance of Titanium Pegs When Measuring Implant Stability With Resonance Frequency Analyses

This in vitro study was conducted to investigate the repeatability of the implant stability quotients (ISQ) measured with multipegs after numerous sterilizations and to detect the exact time when the readings start to deviate. Multipegs were sterilized with 3 different methods (autoclaved, autoclaved + ultrasonic cleaner, chemical disinfection + autoclaved) and grouped according to the method applied. All specimens were put into the autoclave with sealed packages every time they were sterilized. Each specimen was sterilized 50 times according to the technique described in its group after an ISQ measurement was performed. Results of the 2-way analysis of variance showed that neither the sterilization method nor the cycles, nor their interaction, were statistically significant. A multipeg may be reused multiple times after sterilization procedures and may be more cost-effective than a disposable smartpeg for checking implant stability after confirming these results in further investigations.

Biofilm on and structural damage of rotary cutting instruments after 5 cycles of clinical use and processing

BACKGROUND

Rotary cutting instruments (RCIs) are sterilized routinely. The authors aimed to analyze the structural integrity, presence of dirt, and microbial contamination of RCIs used in clinical practice after processing.

METHODS

Eighty-four RCIs (42 carbide burs, 42 diamond burs) were divided into baseline, control, and test groups. The RCIs were evaluated by means of scanning electron microscopy and microbiological analysis. Evaluation criteria included presence of structural damage, dirt, biofilm, and isolated cells and their phenotypic profile.

RESULTS

The carbide burs from all groups and diamond burs from the test groups had structural damage. Dirt was observed in the baseline and test groups. Three bacterial species were isolated from 4 RCIs (9.52%). An isolated cell was observed from 1 carbide bur. Biofilm was observed on 3 RCIs (7.14%).

CONCLUSIONS

RCIs should not be subjected to multiple uses; after the first clinical use they accumulate structural damage and dirt that hampers the cleaning step, causing failure in the sterilization process.

PRACTICAL IMPLICATIONS

The presence of microorganisms and structural damage on the RCIs confirmed that they are not amenable to processing, a fact that characterizes them as a single-use health care product.

Sterilization of New Endodontic Hand Files Stored in Dental Office Inventory: An In Vitro Study

Background and objective Endodontic files, as supplied by the manufacturers to the endodontists, are not pre-sterile routinely. For both new and used equipment, rotary as well as manual, autoclaving is the standard sterilization protocol used in clinical and academic practice. In dentistry, instrument sterilization aims to safeguard patients from cross-contamination through instruments. Hence, every device should be thoroughly cleaned and sterilized. In this study, we aimed to evaluate the presence of various microorganisms in sealed and unsealed stored packs in dental offices and the probable impact of pre-sterilization procedures on the survival of these microorganisms. Materials and methods Two groups of root canal files varying in their packing method, boxes (Mani stainless steel K-files, ISO 25, length 25 mm) and blister packs (UGD, ISO 25, length 25 mm), pre-sterile, opened/unopened were chosen and stored for about two weeks in the dental office and were classified into three groups based on their storage and further classified into subgroups depending on their packing modes as follows: Group-1 (unopened and stored in shelf for two weeks), Subgroup-1A (boxes), Subgroup-1B (blister packs); Group-2 (unopened and stored on the countertop for two weeks), Subgroup-2A (boxes), Subgroup-2B (blister packs); Group-3 (opened and stored on the countertop for two weeks). After two weeks of storage, a set of three new files from each pack, both boxes and blisters, were placed in the nutrient broth to assess the turbidity and later cultured to assess the presence/absence and type of any bacterial growth. All the instruments in the three groups and subgroups were placed separately in the nutrient broth and carried to the microbiology lab for bacterial cultures. The entire procedure was carried out under the laminar flow. All these files in the nutrient broth were incubated for about 72 hours and the turbidity was assessed, and then the turbid bacteria were cultured on blood agar and MacConkey agar plates for the presence/absence and the type of bacteria in each group and subgroups. Results All specimens, both opened/unopened boxes and blister packs, after about two weeks of storage, were cultured and observed for contamination. All the tested files groups showed bacterial culture growth both on blood agar and MacConkey agar plates. Group-1 (Subgroups 1A, 1B) boxes and blister packs unopened and stored on the shelf for two weeks demonstrated aerobic spore bacilli; Group-2 (Subgroups 2A, 2B) boxes and blister packs unopened and stored on the countertop for two weeks demonstrated Gram-positive bacilli; Group-3 opened boxes and blisters stored on the countertop for two weeks demonstrated Micrococci and Gram-negative bacilli. Conclusion In the present study, all the packs, blisters and boxes, demonstrated the presence of bacterial growth irrespective of their storage in the dental office. Hence, in order to prevent any new infections from the operating field, sterilization of not only the old files but also the pre-sterilization of new files should be made mandatory.

Effect of autoclave sterilization on the cyclic fatigue resistance of EdgeFile X7, 2Shape, and F-one nickel-titanium endodontic instruments

Background

Rotary nickel-titanium files have become the most commonly used engine-powered endodontic instruments due to their improvement in fatigue resistance and flexibility. The autoclaving is the most commonly used method for sterilization. However, the risk of instrument fracture, mainly due to cyclic fatigue during rotation within a curved canal, is still a matter of critical concern.

Aims

This study aimed to measure and compares the cyclic fatigue resistance of EdgeFile X7, 2Shape, and F-One files in a single curved simulated canal before and after autoclave sterilization.

Materials and Methods

Twenty-four files each of EdgeFile X7, 2Shape, and F-One files were used in this study. They were grouped as group A: EdgeFile X7, group B: 2Shape, and group C: F-One files. Then, each group was subdivided into two, sterilized and nonsterilized, subgroups. The files were tested using a custom-made artificial canal. The number of cycles to fracture (NCF) was calculated.

Statistical Analysis Used

One-way analysis of variance, post hoc Tukey's test, and independent t-test were used.

Results

In nonsterilized instruments, the NCF of the EdgeFile X7 group was significantly higher than that in the other groups (P < 0.05). In sterilized instruments, there was a nonsignificant difference in NCF between EdgeFile X7 and F-One files (P > 0.05). The NCF of 2Shape was significantly lower than other files (P ≤ 0.05) in sterilized and nonsterilized groups. The autoclaving significantly decreased (P ≤ 0.05) the cyclic fatigue resistance of the tested files.

Conclusions

EdgeFile X7 was the most fatigue resistant. Autoclaving reduced the cyclic fatigue resistance of the tested files.

Knowledge and practice of dentists in processing polishing points: A cross-sectional study

BACKGROUND

Adequately processing polishing points used to polish composite resin restorations is necessary for microbiological control in dentistry, but there is no specific protocol to guide professionals. Therefore, this study aimed to assess the knowledge and practice of dentists in processing these instruments.

METHODS

This cross-sectional observational study included the application of an online questionnaire via Google Forms and social media promotion. The study evaluated the association of field of activity, time since graduation, age, and sex of professionals with processing practice. The statistical analysis was performed with absolute and relative frequencies and logistic and Poisson regressions at a 5% significance level.

RESULTS

Overall, 473 questionnaires were analyzed. A rate of 51% of professionals reported using inadequate processing methods, and almost 68% claimed to have good knowledge of the topic. Both regression analyses were significantly associated, showing a direct effect of age and time since graduation on adequate processing practices.

CONCLUSIONS

Although most professionals reported understanding the processing of polishing points, they do not perform it most adequately.

CLINICAL SIGNIFICANCE

An expressive number of dentists process polishing points improperly. The topic is significant for representing a semi-critical instrument extensively used in esthetic restorations.

Nitinol Type Alloys General Characteristics and Applications in Endodontics

A very extensive literature review presents the possibilities and needs of using, in endodontics, the alloys commonly known as nitinol. Nitinol, as the most modern group of engineering materials used to develop root canals, is equilibrium nickel and titanium alloys in terms of the elements’ atomic concentration, or very similar. The main audience of this paper is engineers, tool designers and manufacturers, PhD students, and students of materials and manufacturing engineering but this article can also certainly be used by dentists. The paper aims to present a full material science characterization of the structure and properties of nitinol alloys and to discuss all structural phenomena that determine the performance properties of these alloys, including those applied to manufacture the endodontic tools. The paper presents the selection of these alloys’ chemical composition and processing conditions and their importance in the endodontic treatment of teeth. The results of laboratory studies on the analysis of changes during the sterilization of endodontic instruments made of nitinol alloys are also included. The summary of all the literature analyses is an SWOT analysis of strengths, weaknesses, opportunities, and threats, and is a forecast of the development strategy of this material in a specific application such as endodontics.

The Effects of Sterilization Procedures on the Cutting Efficiency of Endodontic Instruments: A Systematic Review and Network Meta-Analysis

Sterilization processes guarantee the sterility of dental instruments but can negatively affect instrument features by altering their physical and mechanical properties. The endodontic instrumentation can undergo a series of alterations, ranging from corrosion to variation in the cutting angle and then changes in the torsional properties and torsional fatigue resistance. This systematic literature review and meta-analysis aims to investigate alterations to the cutting efficiency of endodontic instruments that are induced by procedures for their disinfection and sterilization. Methodologies adopted for this investigation follow the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. The following were used as search terms on PubMed and Scopus: "endodontic sterilization", "endodontic autoclave", "cyclic fatigue", "torsional", "cutting efficiency", "sterilization", "surface characteristics", and "corrosion". At the end of the selection process, 36 articles were identified, and seven of them are included in this systematic review. The results of a meta-analysis conducted for the use of 10 autoclaving cycles shows a standardized mean difference (SMD) of 0.80 with a p-value equal to 0.04 with respect to effect on cutting efficiency. The network meta-analysis, through direct and indirect comparison between the different autoclave cycles (0, 1, 5, 10, and 15 cycles), revealed that treatment involving 15 autoclave cycles produced the most robust results in terms of having the greatest effects in terms of altered cutting efficiency with a probability of 57.7% and a SUCRA (surface under the cumulative ranking) of 80%. The alterations in the effects on cutting efficiency appear to be triggered after five cycles of sterilization by heat (autoclave). In conclusion, the meta-analysis of the data indicates that the autoclave sterilization protocol must not be repeated more than five times to preserve cutting efficiency. Within the limitations of this review, we can therefore establish that sterilization by autoclaving alone results in steel and NiTi instruments becoming less efficient in cutting after five cycles, as measured by a reduction in cutting efficiency.

The Effect of Multiple Autoclave Sterilization on the Cyclic Fatigue of Three Heat-Treated Nickel-Titanium Rotary Files: EdgeFile X7, Vortex Blue, and TRUShape

OBJECTIVE

The purpose of this study was to evaluate the effect of repeated autoclave sterilization on the cyclic fatigue resistance of heat-treated NiTi rotary endodontic instruments.

MATERIALS AND METHODS

Three NiTi rotary endodontic instruments (EdgeFile X7, EFX7 0.30/0.4; Vortex Blue, VB 0.30/0.4; and TRUShape, TS 0.30/0.6) were selected. Each group (n = 24 each) was divided into 2 subgroups (n = 12 each): sterilized instruments and nonsterilized instruments. The sterilized instruments were subjected to 10 cycles of autoclave sterilization. Twelve instruments from each different subgroups were tested for cyclic fatigue resistance, and the number of cycles to failure (NCF) was calculated. Means and standard deviations were calculated for each group, and data were statistically analyzed using the SPSS program (P < 0.05).

RESULTS

Sterilized and nonsterilized EFX7 files showed the highest NCF compared with other file subgroups. Comparing the results between sterilized and nonsterilized instruments for each type of files, there was a statistically significant difference (P < 0.05) only between sterilized and nonsterilized EFX7 files (1198 versus 755 NCF). The other instruments did not show significant differences (P > 0.05) in the mean NCF as a result of sterilization cycles (VB, 606 versus 568 NCF; TS, 487 versus 442 NCF).

CONCLUSION

Repeated cycles of autoclave sterilization increased the NCF of the new heat-treated files, with EFX7 showing statistically significant superior results compared with other files tested.

Management of Severe Curvatures in Root Canal Treatment with the New Generation of Rotating Files Using a Safe and Predictable Protocol

Objective:

The aim of this work was to show the management of severe curvatures done with the new generation of rotating files through a safe and predictable protocol.

Methods:

Three clinical cases were described. A safe protocol was explained using the latest generation of rotating files for the shaping of the anatomy of complex root canals. All the cases presented 90°, 45° curvatures and/or double curvatures.

Results:

The instrumentation of canals increased their surface area and volume. All the cases with 90° and 45° curvatures were optimally shaped.

Conclusion:

With the help of rotating files in the martensitic alloy, it is possible to work safely, while avoiding the risk of file separation, even in root canals with severe curvatures, thus achieving success even in complex clinical cases.