Sterilisation in Dentistry: A Review of the Literature

Evaluation of Forensic Luminol in Detection of Blood Stains in Instruments Following Dental Treatment

Background Saliva and blood, being biological materials with a high potential for infectious transmission in dental environments, pose significant risks to dental professionals, assistants, and patients alike. Therefore, practitioners must adopt stringent security measures to ensure patient care, considering all parties as potential carriers of microorganisms capable of causing infectious diseases. Currently, various methods of disinfection and sterilization are employed to maintain the aseptic chain effectively. Having reliable methods for detecting substances in liquids, particularly body fluids, is crucial and highly convenient. Luminol, a chemiluminescent agent widely used in forensic science for detecting minute traces of blood that are invisible to the naked eye, presents itself as a valuable tool. Blood, a major bodily fluid often present in instruments following dental procedures, underscores the importance of its detection. Hence, in this study, luminol was utilized to detect blood traces in dental instruments following dental treatment, both before and after sterilization or disinfection. Objective Blood and saliva splashes, together with highly contagious aerosols, are always a part of dental procedures. The objective of the current study is to detect traces of blood stains on face shields, surgical instruments, and endodontic files using luminol before and after sterilization. Materials and methods Sample size calculation was done with G*Power software (Version 3.1.9.4, Düsseldorf, Germany), and a total of 30 instruments were selected for the study. In the present study, a total of 30 items were collected and utilized, including 14 instruments used after implant placement, 12 endodontic files employed after root canal treatment, and four face shields utilized during these procedures. Meanwhile, a freshly prepared luminol solution was applied to these instruments, and they were viewed in a dark environment both before and after sterilization procedures. Luminescence generated by luminol was observed in the instruments, indicative of the presence of blood not visible to the naked eye. Statistical analysis for both groups was done with IBM SPSS Statistics for Windows, Version 16.0 (Released 2007; SPSS Inc., Chicago, IL, USA). Intragroup comparison was done using the Friedman test, and intergroup comparison was done using the Wilcoxon signed-rank test. Results Blood stains and chemiluminescence were visualized in two out of 10 endodontic files (one #15 K-file and #20 K-files) and two out of four face shields. The intragroup comparison was done using the Friedman test, and it was found to be statistically significant (p < 0.05). Intergroup comparison was done using the Wilcoxon signed-rank test and was found to be statistically insignificant (p > 0.05). Conclusion Following sterilization and disinfection, there were no visual blood stains or chemiluminescence. Therefore, luminol was found to be effective in detecting blood stains in endodontic files, surgical instruments, and face shields, as well as in validating the sterilization and disinfection processes. Hence, sterilization in dentistry stands as a critical measure to guarantee patient safety, halt the dissemination of infections, and uphold exemplary clinical care standards.

A survey regarding the organizational aspects and quality systems of in-house 3D printing in oral and maxillofacial surgery in Germany

PURPOSE

The aim of the study was to get a cross-sectional overview of the current status of specific organizational procedures, quality control systems, and standard operating procedures for the use of three-dimensional (3D) printing to assist in-house workflow using additive manufacturing in oral and maxillofacial surgery (OMFS) in Germany.

METHODS

An online questionnaire including dynamic components containing 16-29 questions regarding specific organizational aspects, process workflows, quality controls, documentation, and the respective backgrounds in 3D printing was sent to OMF surgeons in university and non-university hospitals as well as private practices with and without inpatient treatment facilities. Participants were recruited from a former study population regarding 3D printing; all participants owned a 3D printer and were registered with the German Association of Oral and Maxillofacial Surgery.

RESULTS

Sixty-seven participants answered the questionnaires. Of those, 20 participants ran a 3D printer in-unit. Quality assurance measures were performed by 13 participants and underlying processes by 8 participants, respectively. Standard operating procedures regarding computer-aided design and manufacturing, post-processing, use, or storage of printed goods were non-existent in most printing units. Data segmentation as well as computer-aided design and manufacturing were conducted by a medical doctor in most cases (n = 19, n = 18, n = 8, respectively). Most participants (n = 8) stated that "medical device regulations did not have any influence yet, but an adaptation of the processes is planned for the future."

CONCLUSION

The findings demonstrated significant differences in 3D printing management in OMFS, especially concerning process workflows, quality control, and documentation. Considering the ever-increasing regulations for medical devices, there might be a necessity for standardized 3D printing recommendations and regulations in OMFS.

Efficacy and design requirements of UV light cabinets for disinfection of exchangeable non-sterilizable "dental objects"

Non-sterilizable items such as prosthodontics items constitute a high risk of transmitting dangerous pathogens, including Coronavirus, between patients and healthcare personnel. Although UV rays are recognized for their germicidal efficacy, large and expensive UV devices previously hindered their adoption in dental offices. During the COVID-19 pandemic, small UV devices became available for domestic use, albeit with varying designs and effectiveness. Our study assesses the disinfection capacity of a UV light cabinet for four dental materials and discusses crucial design features for effective performance. Specimens of each material (silicone impressions, stone cast, acrylic denture base, and indelible pencils) were contaminated with Escherichia coli Bl21, and randomly divided into three study groups: UV device (UVG), impressions disinfection solution (SG), and control (CG). The experiment was repeated thrice, and disinfection efficacy assessed by colony forming units (CFU) count. A 2.5-min UV exposure achieved full disinfection for all materials. Significantly different results were found between groups (p < 0.05, one-way ANOVA, Tukey HSD), except for indelible pencils, where UVG and SG were both highly effective. UV cabinets surpass SG's disinfection efficacy. Compact UV devices can offer affordable, portable, and efficient disinfection for non-sterilizable dental objects, with careful consideration of wavelength, exposure, intensity, and safety.

The synergistic antibacterial activity of ozone and surfactant mists

The microbiological safety of medical equipment and general surfaces is paramount to both the well-being of patients and the public. The application of ozone (a potent oxidant) has been recognised and implemented for this purpose, globally. However, it has primarily been utilised in the gaseous and aqueous forms. In this study, we investigate the potency of fine ozone mists and evaluate the synergistic effect when combined with cationic, anionic and non-ionic surfactants (dodecyl trimethyl ammonium bromide - DTAB, sodium dodecyl sulfate - SDS, alkyl polyglycoside - APG) as well as polyethylene glycol (PEG). Ozone mist is generated via a nebuliser (equipped with a compressed gas stream) and the piezoelectric method; whereas fabric substrates contaminated with Escherichia coli and Staphylococcus aureus are utilised in this study. Contamination levels on the fabric swatches are evaluated using agar dipslides. Compared to gaseous ozonation and aqueous ozonation (via nanobubble generation), the produced ozone mists showed significantly inferior antimicrobial properties for the tested conditions (6 ppm, 5-15 min). However, the hybrid mist-based application of 'ozone + surfactants' and 'ozone + PEG' showed considerable improvements compared to their independent applications (ozone mist only and surfactant mist only). The 'ozone + DTAB' mist had the highest activity, with better results observed with the micron-mist nebuliser than the piezoelectric transducer. We propose a likely mechanism for this synergistic performance (micellar encapsulation) and demonstrate the necessity for continued developments of novel decontamination technologies.

The influence of indirect bonded restorations on clinical prognosis of endodontically treated teeth: A systematic review and meta-analysis

OBJECTIVE

The loss of the dental coronal portion following carious lesions or fractures leads to endodontic treatment with subsequent restoration to ensure correct anatomy and function. Recently, partial adhesive restorations have been widely proposed to increase the survival rate of endodontically treated teeth. The primary purpose of this review is to assess the failure rate of indirect partial adhesive restorations on endodontically treated teeth (ETT), considering the follow-up period.

METHODS

The indications reported in the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) were used to draft the present review. The study was constructed on PICO questions: population (patients who need indirect adhesive restorative treatment on endodontically treated teeth with onlay and overlay), intervention (onlay and overlay), control (patients with onlay and overlay on endodontically treated teeth) and outcome (failure rate and types of failure for onlay and overlay). The asked scientific question was: what are the failure rate and types of failure for adhesive indirect partial restorations on ETT?

RESULTS

The overall failure rate that emerges is 0.087 with a ratio of 121/1254, I² 80 % p-value< 0.001. Moreover, by meta-regression with covariates the follow-up period reports a coefficient of 0.013 with a P-value< 0.001. In conclusion, the indirect partial restorations on endodontically treated teeth displayed overall acceptable outcomes in terms of success from 2 to 4 years after their placement with only 4.32 % of failure. Failures increase after 7 years up to 12-30 years with failure rates of approximatively 10.65 % and 20.94 %. The analysis of the included articles reporting the causes of restorations failures showed that 15.51 % of cases were related to the loss of dental element.

SIGNIFICANCE

Besides the survival rates of indirect adhesive restorations on endodontically treated posterior teeth, it was highlighted that the majority of failures appeared restorable. Thus, partial restorations seemed able to prevent the ETT tooth loss.

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.

A Description of Infection Control Structure in Primary Dental Health Care, Brazil

OBJECTIVE

This study is aimed at describing a score to assess infection control structures in Oral Health Teams (OHT) in Primary Health Care (PHC) in Brazil.

METHODS

Secondary data from a national external evaluation of PHC conducted in 2017 and 2018 were analyzed. The construction of the score used 14 variables, divided into the following: structural characteristics of the PHC, infection control equipment under conditions of use, and biosafety supplies in sufficient quantity. The questions were mostly dichotomous (yes/no). Descriptive analyses were carried out to characterize the OHT and factor analyses to reduce the number of observed variables to a specific number of factors.

RESULTS

Among 20,301 health units with OHT, 4,510 (22.2%) units did not have washable floors, ceilings, and walls; 8,406 (41.4%) did not have a sealer; 16,780 (82.7%) did not have taps with noncontact activation, and 4,663 (23.0%) units did not have rubber gloves. Regarding personal protective equipment (PPE), 1,618 (8.0%) units did not have a sufficient quantity of basic PPE. Three factors were defined to explain the 14 evaluated variables. The South region had the best score of infection control, while the North had the worst.

CONCLUSIONS

Regional inequalities in the failures in infection control structures identified in PHC with OHT were related to the physical structure, equipment, and supplies used for infection control and the absence of PPE for OHT.

Effects of repeated sterilization cycles on the surface alterations of ProTaper Next, TF Adaptive, HyFlex CM, and 2Shape instruments

Background. This study aimed to evaluate the effects of repeated sterilization cycles on the surface alterations of various nickel-titanium instruments, including ProTaper Next (PTN), TF Adaptive (TFA), HyFlex CM (HCM), and 2Shape (2S). Methods. Twenty-four new NiTi files of four different alloys were selected. The instruments in each group were divided into two equal groups, as follows: control and sterilization. The first group was chosen as the control without applying any sterilization procedure, while in group 2, five cycles of sterilization procedures were applied. The surface topographies were evaluated using scanning electron microscope (SEM) and atomic force microscope (AFM). The root mean square (RMS) and maximum height (MH) values and three-dimensional images were recorded. The data were analyzed with the Shapiro-Wilk test, one-way ANOVA, and post hoc Tukey tests. The statistical significance level was set at P ≤ 0.05. Results. Before the experiment, HCM demonstrated the highest RMS value, and 2S showed the lowest. After the procedures, the RMS and MH values deteriorated on the surface of PTX, TFA, and 2S (P < 0.001). The HCM was not affected by sterilization processes (P > 0.05). Conclusion. The initial irregularity on the surface did not affect the rate of alteration. The HCM files demonstrated superior surface properties after several cycles of sterilization. The PTN, TFA, and 2S presented similar surface responses after five cycles of autoclave sterilization.

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.

Portable ozone sterilization device with mechanical and ultrasonic cleaning units for dentistry

A portable device for cleaning and ozone sterilization of small-sized delicate dental instruments that cannot withstand the high heat and humidity of standard autoclaving has been developed. The device contains a remote unit for magnetic mechanical washing, an ultrasonic bath for pre-cleaning treatment, and a container for ozone sterilization with a reactor based on dielectric barrier discharge. The maximum ozone concentration in water reached 8.5 mg/l for 10 min of operation at a water temperature of 19 °C. The results of inactivation of Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus are presented. Distilled water with such seeded micro-organisms was bubbled with an ozone-air mixture at an ozone concentration of 5.8 mg/l at 17 °C for 5 min, 10 min, 20 min, and 30 min. The maximum bactericidal effect was manifested for Pseudomonas aeruginosa cells with their total elimination within 10 min. Inactivation of Escherichia coli bacteria was monitored after 20 min of treatment, and Staphylococcus aureus-after 30 min of treatment.

Novel Electronic Device to Quantify the Cyclic Fatigue Resistance of Endodontic Reciprocating Files after Using and Sterilization

Background: The aim of this study was to analyze the effects of the time of use (TU) and sterilization cycles (SC) of endodontic reciprocating files on cyclic fatigue resistance. Methods: One-hundred-and-twenty (120) Procodile NiTi endodontic reciprocating instruments were selected at random and distributed into the following study groups: A: 0 sterilization cycles/0s time of use (n = 10); B: 0/60 (n = 10); C: 0/120 (n = 10); D: 1/0 (n = 10); E: 1/60 (n = 10); F: 1/120 (n = 10); G: 5/0 (n = 10); H: 5/60 (n = 10); I: 5/120 (n = 10); J: 10/0 (n = 10); K: 10/60 (n = 10); and L: 10/120 (n = 10). A dynamic cyclic fatigue device was designed using computer-aided design/computer-aided engineering (CAD/CAE) technology and created with a 3D printer to simulate the pecking motion performed by the clinician. Failure of the endodontic rotary instrument was detected by a light-emitting diode-light-dependent resistor (LED-LDR) system controlled by an Arduino driver complex and management software. The results were analyzed using the ANOVA test. Results: All pairwise comparisons presented statistically significant differences between the time to failure, number of cycles to failure and number of cycles of in-and-out movement for the time of use study groups (p < 0.001), but not in the number of sterilization cycles (p > 0.05). Conclusions: The time of use of NiTi endodontic reciprocating files negatively affects dynamic cyclic fatigue resistance. Dynamic cyclic resistance is not affected by the number of sterilization cycles.

Sterility maintenance of reused disposable paper/plastic sterilization pouches in actual clinical practice

Paper/plastic sterilization pouches are commonly used packaging material for steam sterilization. Reuse of these pouches is a general practice in Thailand despite a single-use recommendation. This study aimed to determine microbial contamination after reusing paper/plastic sterilization pouches in a dental clinic and storage in a closed environment for 6 months. Three hundred and twenty pouches underwent 3 times of clinical use in terms of packaging, autoclave sterilization, handling, and unpacking. A mouth mirror was packed in each pouch to be used in a clinic. After each use, a pouch would be carefully inspected for reusability and undergone packaging, sterilization, handling again. In all steps, sterilization monitoring was rigorously applied. After 3 times of use, a piece of filter paper was placed inside each pouch (instead of a mouth mirror), the pouch was autoclaved and stored in a closed environment for 6 months. Then the filter paper was retrieved for microbial cultivation. A negative control group comprised new pouches containing filter paper without storage and a positive control group comprised pouches with impaired integrity. All samples in both the reuse and the negative control groups had no microbial contamination. All samples in the positive control group showed contamination. These results suggested that reusing paper/plastic sterilization pouches could be a safe practice provided careful monitoring and inspection were employed.

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.

Surface Alterations Induced on Endodontic Instruments by Sterilization Processes, Analyzed with Atomic Force Microscopy: A Systematic Review

Endodontic canal disinfection procedures that use sodium hypochlorite, and subsequently, heat sterilization procedures can alter the surface of endodontic instruments, described as corrosion and micropitting. These phenomena can be visualized on the surface of the instruments by SEM and atomic force microscopy analyses. The endodontic instruments used in probing, pre-enlargement, and shaping phases are made of steel alloy or nickel-titanium alloy (NiTi) and are subject to torsional, flexor, and cyclic fatigue; indeed, reuse of these instruments must be done with the knowledge that these instruments are subject to fracture following stress caused during their use. Fracture of the instrument within the canal is an eventuality that can lead to failure of the treatment, and therefore it is important to try to reduce situations that can contribute to the fracture. This review was performed based on the PRISMA protocol. Studies were identified through bibliographic research using electronic databases. A total of 1036 records were identified on the PubMed and Scopus databases. After screening the articles, restricted by year of publication (1979 to 2019), there were 946 records. With the application of the eligibility criteria (all the articles pertaining to the issue of sterilization in endodontics), there were 228 articles. There were 104 articles after eliminating overlaps. There were 50 articles that discussed the influence of sterilization procedures on the surface characteristics of endodontic instruments, and 26 articles that measured parameters on surface alteration. Applying the inclusion and exclusion criteria resulted in a total of eleven articles for quantitative analysis. Four articles were in reference to the primary outcome, eight articles to secondary outcome, and five articles to tertiary outcome. The meta-analysis showed a statistically significant surface alteration effect after five autoclaves and after immersion in the canal irrigants after 10 min.

Autoclave sterilization of dental handpieces: A literature review

PURPOSE

The present review aimed to investigate autoclave sterilization of dental handpieces based on available studies.

STUDY SELECTION

The sterilizing efficiency of dental handpieces with autoclave is mainly affected by the types of apparatus (N, B, and S), the packaging with sterilizing pouch, cleaning, and lubrication. These subjects were reviewed based on the in vitro experimental studies.

RESULTS

Dental handpieces can be sterilized, including inactivation of heat-resistant bacterial spores, with type B or type S sterilizers, regardless of the use of a sterilization pouch. In contrast, although type N autoclaves are capable of sterilization of general bacteria such as Streptococcus salivarius even in a sterilization pouch if instruments are washed beforehand, complete sterilization of the wrapped handpiece is not always achieved. Therefore, to achieve sterilization efficiency with type N autoclaves, processing without any packaging is recommended. As regards cleaning of handpiece, although contamination decreases with irrigation and wiping of handpieces, all reports concluded that these treatments alone do not achieve complete decontamination of reusable handpieces.

CONCLUSION

Although type B and type S autoclaves allow us to sterilize the dental handpieces, it is important to realize that complete sterilization of the handpiece is not always achieved by type N autoclave. Understanding autoclave processing of handpieces is essential for dental practice to deliver the safe dental care.

Effects of Hot Sterilization on Torsional Properties of Endodontic Instruments: Systematic Review with Meta-Analysis

Sterilization is a fundamental step in the reuse of endodontic instruments. The sterilization procedure involves disinfection, cleaning, washing, drying, packaging, and sterilization by heat. Heat sterilization can lead to changes in the physical and mechanical properties of dental instruments. These changes can affect the external surfaces via micropitting, corrosion, a reduction in cutting capacity, and/or an influence on the resistance to cyclic fatigue or to torsional fatigue. In this study, we examined the modification of the torsional properties of endodontic instruments after hot sterilization, and compared the properties with instruments not subjected to hot sterilization cycles in terms of resistance to torsional fatigue and deflection angle in NiTi and steel instruments. The following work was performed based on the PRISMA indications. Studies were identified through bibliographic research using electronic databases. A total of 725 records were identified in the PubMed and Scopus databases. A total of 685 records remained after exclusion by year of publication (1979 to 2019). With the application of the eligibility criteria (all articles pertaining to the issue of sterilization in endodontics), we found 146 articles, which decreased to 130 articles after elimination of duplications. There were 45 articles that studied the influences of sterilization procedures on the physical and mechanical characteristics of the instruments, and 12 that measured parameters related to resistance to torsional fatigue. Applying the inclusion and exclusion criteria resulted in a total of eight articles for quantitative analysis. The meta-analysis results show a pejorative effect of torsional fatigue for NiTi instruments subjected to heat sterilization compared to the non-sterilized control.