The fungicidal effect of ultraviolet light on impression materials

Disinfection Procedures and Their Effect on the Microorganism Colonization of Dental Impression Materials: A Systematic Review and Meta-Analysis of In Vitro Studies

Dental impressions are contaminated with potentially pathogenic microorganisms when they come into contact with patient blood, saliva, and plaque. Numerous disinfectants are used; however, no sole disinfectant can be designated as universal for all the impression materials. Thus, the aim of this study is to systemically review the literature to evaluate the effect of the existing disinfection procedures on the bacterial colonization of dental impression materials. This systematic review and meta-analysis was conducted according to the PRISMA statement. PubMed (MEDLINE), Web of Science, Scopus, EMBASE, and SciELO databases were screened up to April 2021. Eligibility criteria included in vitro studies reporting the antibacterial activity of disinfectant solutions in dental impression materials. The meta-analysis was performed using Review Manager (version 5.3.5). A global comparison was performed with the standardized mean difference based on random-effect models at a significance level of α = 0.05. A total of seven studies were included in the meta-analysis. The included studies described the effect of disinfection processes with chlorhexidine gluconate, alcohol, sodium hypochlorite, glutaraldehyde, and hydrogen peroxide in alginate, polyvinyl siloxane, and polyether impression materials. The meta-analyses showed that the use of chlorhexidine, alcohol, glutaraldehyde, and sodium hypochlorite reduced the colony-forming units by a milliliter (CFU/mL) in alginate (p < 0.001). On the other hand, glutaraldehyde, sodium hypochlorite, and alcohol reduced the CFU/mL in polyvinyl siloxane (p < 0.001). Finally, alcohol and glutaraldehyde reduced the CFU/mL in polyether material (p < 0.001). High heterogenicity was observed for the alginate and polyvinyl siloxane materials (I2 = 74%; I2 = 90%). Based on these in vitro studies, the disinfection of impression materials with several disinfection agents reduces the CFU/mL count.

Disinfection of Impression Materials with Glutaraldehyde, Ultraviolet Radiation, and Autoclave: A Comparative Study

Background:

The present study was conducted to compare various methods of disinfection of impression materials such as glutaraldehyde, ultraviolet (UV) radiation, and autoclave.

Materials and Methods:

The present study was conducted on eighty alginate impression materials which were disinfectant with 2.2% glutaraldehyde, UV radiation, and autoclave. The pre- and postbacterial count was assessed.

Results:

The mean premicrobial contamination in Group I was 362.2 106 colony-forming unit (CFU)/ml, in Group II was 306.4 106 CFU/ml, and in Group III was 336.2 106 CFU/ml. The mean postmicrobial contamination in Group I was 65.2 106 CFU/ml, in Group II was 76.7 106 CFU/ml, and in Group III was 28.4 106 CFU/ml.

Conclusion:

The authors found that autoclave proved to be better in terms of reduction in bacterial colonies as compared to glutaraldehyde and UV radiation.

Comparative Evaluation of the Effect of Chemical Disinfectants and Ultraviolet Disinfection on Dimensional Stability of the Polyvinyl Siloxane Impressions

Context

Infection control is an important concept in the present day practice of dentistry. Disinfection of dental impressions is part of the daily routine in a dental clinics. After disinfection, it is important that impressions remain dimensionally stable.

Aim

The purpose of this study was to compare the effect of chemical disinfectants and ultraviolet (UV) disinfection on the dimensional stability of the polyvinyl siloxane impressions.

Objectives

The objective of the study is (1) To evaluate the effect of chemical disinfectant (2% glutaraldehyde and 1% sodium hypochlorite) and UV disinfectant on the dimensional stability of polyvinyl siloxane impression material. (2) Comparative evaluation of the dimensional discrepancy between the cast poured from the polyvinyl impressions material, that is subjected to chemical disinfectant and UV disinfectant to that of cast poured from impressions that were nondisinfected.

Materials and Methods

A customized tray was fabricated to make impressions. Impressions were divided into four groups, 10 samples were disinfected with 2% glutaraldehyde for 20 min, 10 samples were disinfected with 1% sodium hypochlorite for 20 min, 10 samples were disinfected with UV light for 20 min, and 10 samples were not subjected to disinfection which served as control group. All the samples were poured after 30 min in die stone. Measurements were recorded using traveling microscope of 0.001 accuracy. Statistical analysis used in this study was the one-way ANOVA test.

Results

The result showed significant dimensional changes in samples disinfected with 2% glutaraldehyde and 1% sodium hypochlorite, whereas samples disinfected with UV disinfectant unit showed no significant dimensional changes when compared with control group samples. Within the chemical groups, impressions disinfected with 1% sodium hypochlorite showed more discrepancy in the dimensions when compared to the 2% glutaraldehyde disinfected group.

Conclusions

UV light disinfectant can be safely used to disinfect impressions as compared to chemical disinfectants in clinical prosthodontic procedures.

Comparative evaluation of dimensional stability of impression materials from developing countries and developed countries after disinfection with different immersion disinfectant systems and ultraviolet chamber

Objectives

It was to analyse and compare the effect of different disinfectant systems on the dimensional stability of commonly used irreversible hydrocolloid and addition silicone impression materials from developing countries as compared to materials from developed countries.

Material and methods

Disinfectant systems used were glutaraldehyde, sodium hypochlorite and ultraviolet chamber. The stability after disinfection of commonly used alginate and addition silicone of native origin (Algin-Gum & Ad-Sil) was compared with similar impression materials from developed countries (Vignette and Aquasil) and results compared. A CAD/CAM manufactured stainless steel die simulating maxilla with four metal studs at canine and molar region was used. Impressions were made and disinfected after rinsing and drying and casts poured. The cross arch distance, interabutment distance and the occluso-gingival length of the studs was measured under traveling microscope and observations were recorded and compared. ANOVA test and Bonferroni test was applied.

Results

An increase in the interabutment and cross arch distance and decrease in occluso-gingival height was seen in the casts obtained. Glutaraldehyde immersion showed variation in the interabutment and cross arch distance for all materials studied. Ultraviolet chamber and sodium hypochlorite produced best results. Dimensional stability of impression materials like Vignette, Algin-Gum & Aquasil was found to within clinically acceptable limits after disinfection while maximum deviation was seen with Algin-Gum.

Conclusion

Evaluated materials can be safely disinfected with sodium hypochlorite and ultraviolet chamber. Addition silicone of native origin is at par with impression materials from developed countries but same cannot be said about alginate.

Comprehensive Review and Comparison of the Disinfection Techniques Currently Available in the Literature

The goal of disinfection in the dental office is to prevent the spread of infection from one patient to another and maintain the safety of the dental care providers. Prevention of cross infection has significant effect on infection control. The standard procedure of rinsing impressions under tap water immediately after removal from the mouth eliminates microorganisms along with saliva and blood. A broad search on published literature was done using the keywords impression materials, disinfection method, and sterilization of dental impression from 1980 to 2016 in Medline, Google Scholar, the internet, and textbooks. This article critically analyzes the various published methods of dental impression disinfection in dentistry.

Comparison of UV C Light and Chemicals for Disinfection of Surfaces in Hospital Isolation Units

Objective.

To determine the bactericidal effect on surfaces of ceiling- and wall-mounted UV C (UVC) light (wavelength, 254 nm) in isolation units, compared with standard hospital environmental cleaning and chemical disinfection during final disinfection after patients are treated for infections.

Design.

Microbial samples were obtained from surfaces in isolation units (patient room, anteroom, and bathroom) before and after irradiation with UVC, chloramine disinfection, and standard hospital environmental cleaning. Samples were tested using standard contact plates.

Setting.

Four identical, negative air-pressure isolation units (patient room, anteroom, and bathroom) with a defined number of ceiling-and wall-mounted UVC light units. The UVC distribution was monitored in one isolation unit after irradiation for approximately 40 minutes, corresponding to doses ranging from 160 J/m2in a shadowed area to 19,230 J/m2at the mostly highly exposed site (which is high enough to inactivate most bacterial organisms, including spores).

Results.

UVC disinfection significantly reduced the number of bacteria on surfaces directly or indirectly exposed to UVC to a very low number, as did 5% chloramine disinfection alone (P<.001 for both). Completely shadowed areas in the isolation unit (eg, the bed rail, lockers, and mattresses) still required disinfection by chemicals.

Conclusion.

Disinfection with UVC light may significantly reduce environmental bacterial contamination and thereby protect the next patient housed in an isolation room. UVC disinfection may not be used alone but is a good addition to chemical disinfection.

Quantitative investigation of efficiency of ultraviolet and visible light in eradication of Candida albicans in vitro

OBJECTIVE

The aim of this study was to quantitatively investigate the efficiency of the ultraviolet (UV) and visible light in eradication of Candida albicans in vitro; in particular, to determine, for selected wavelengths, the specific eradication coefficients and thresholds in terms of energy density levels required to effect 3.0log10 and 4.0log10 reduction.

BACKGROUND DATA

Oral candidosis is the most common infection of the oral cavity and is caused by Candida species. The widespread use of topical and systemic antifungal agents as conventional treatment for oral candidosis has resulted in the development of resistance in C. albicans. Therefore, it has become necessary to develop alternative therapies for the treatment of oral candidosis.

METHODS

C. albicans ATCC(®) 90028(™) was irradiated with 254 nm, 365 nm, 406 nm, 420 nm, and broadband Xe spectrum. For each wavelength, a fit of experimental data (survival fraction vs. applied energy density) with an exponential decay function enabled estimation of the specific eradication coefficients and thresholds.

RESULTS

Based on estimated specific efficiencies (Δ) and eradication thresholds (ET) of the investigated wavelengths, the ranking in eradication efficiency of C. albicans (most to least effective) is: 254 nm (Δ=6.1 mJ/cm(-2), ET99.99=56 mJ/cm(-2)), broadband Xe spectrum (Δ=27.7 mJ/cm(-2), ET99.99=255 mJ/cm(-2)), 365 nm (Δ=4.3 J/cm(-2), ET99.99=39 J/cm(-2)), 420 nm (Δ=0.65 J/cm(-2), ET99.99=6 J/cm(-2)), and 406 nm (Δ=11.4 J/cm(-2), ET99.99=104 J/cm(-2)).

CONCLUSIONS

The results provide insight into the wavelength-dependent dynamics of eradication of C. albicans. For each investigated wavelength, the eradication coefficient and corresponding eradication threshold were estimated. The observed different eradication efficiencies are consequence of different spectrally dependent inactivation mechanisms. The established methodology enables unambiguous quantitative comparison of eradication efficiencies of optical radiation and selection of most effective wavelengths for clinical and therapeutic use.

In vitro antifungal evaluation of seven different disinfectants on acrylic resins

Objective. The aim of this study was to evaluate alternative methods for the disinfection of denture-based materials. Material and Methods. Two different denture-based materials were included in the study. Before microbial test, the surface roughness of the acrylic resins was evaluated. Then, the specimens were divided into 8 experimental groups (n = 10), according to microorganism considered and disinfection methods used. The specimens were contaminated in vitro by standardized suspensions of Candida albicans ATCC#90028 and Candida albicans oral isolate. The following test agents were tested: sodium hypochlorite (NaOCl 1%), microwave (MW) energy, ultraviolet (UV) light, mouthwash containing propolis (MCP), Corega Tabs, 50% and 100% white vinegar. After the disinfection procedure, the number of remaining microbial cells was evaluated in CFU/mL. Kruskal-Wallis, ANOVA, and Dunn's test were used for multiple comparisons. Mann Whitney U test was used to compare the surface roughness. Results. Statistically significant difference (P < 0.05) was found between autopolymerised and heat-cured acrylic resins. The autopolymerised acrylic resin surfaces were rougher than surfaces of heat-cured acrylic resin. The most effective disinfection method was 100% white vinegar for tested microorganisms and both acrylic resins. Conclusion. This study showed that white vinegar 100% was the most effective method for tested microorganisms. This agent is cost-effective and easy to access and thus may be appropriate for household use.

In vitro bactericidal effects of 625, 525, and 425 nm wavelength (red, green, and blue) light-emitting diode irradiation

OBJECTIVE

The purpose of this study was to evaluate the relationship of 625, 525, and 425 nm wavelengths, providing average power output and effects on three common pathogenic bacteria.

BACKGROUND DATA

Ultraviolet (UV) light kills bacteria, but the bactericidal effects of UV may not be unique, as 425 nm produces a similar effect. The bactericidal effects of light-emitting diode (LED) wavelengths such as 625 and 525 nm have not been described. Before conducting clinical trials, the appropriate wavelength with reasonable dose and exposure time should be established.

MATERIALS AND METHODS

The bactericidal effects of 625, 525, and 425 nm wavelength LED irradiation were investigated in vitro for the anaerobic bacterium Porphyromonas gingivalis and two aerobes (Staphylococcus aureus and Escherichia coli DH5α). Average power output was 6 mW/cm(2) for 1 h. The bacteria were exposed to LED irradiation for 1, 2, 4, and 8 h (21.6, 43.2, 86.4, and 172.8 J/cm(2), respectively). LED irradiation was performed during growth on agar and in broth. Control bacteria were incubated without LED irradiation. Bacterial growth was expressed in colony-forming units (CFU) and at an optical density at 600 nm in agar and broth.

RESULTS

The bactericidal effect of LED phototherapy depended upon wavelength, power density, bacterial viable number, and bacteria species. The bactericidal effect of 425 and 525 nm irradiation varied depending upon the bacterial inoculation, compared with unirradiated samples and samples irradiated with red light. Especially, P. gingivalis and E. coli DH5α were killed by 425 nm, and S. aureus growth was inhibited by 525 nm. However, the wavelength of 625 nm was not bactericidal for P. gingivalis, E. coli DH5α, or S. aureus.

CONCLUSIONS

Irradiation at 625 nm light was not bactericidal to S. aureus, E. coli, and P. gingivalis, whereas wavelengths of 425 and 525 nm had bactericidal effects. S. aureus was also killed at 525 nm.

A comparative evaluation of disinfection effect of exposures to ultra-violet light and direct current glow discharge on Candida Albicans colonies coated over elastomeric impression material: An in vitro study

Aim:

The aim of our study is to compare the efficacy of ultra-violet light (U-V light) and direct current glow discharge in disinfecting Candida Albicans coated elastomeric impression material.

Materials and Methods:

Two hundred and forty samples of addition silicone material in the form of circular discs measuring (diameter-30 mm, thickness-3 mm) were prepared. Samples were divided into four groups namely A, B, C, D, with each group containing 60 samples. All samples in each group were sub grouped as follows for exposure time 15, 30, 60, 90, 120 and 180 s respectively. Group A samples were exposed to U-V light with 8 watts. Group B samples were exposed to U-V light with 16 watts. Group C samples were exposed to U-V light with 24 watts. Group D samples were exposed to direct current glow discharge. After exposure, the impression material was swabbed on sabourauds dextrose agar (SDA) plates and incubated at 37°C for 48 h. The total number of colonies indicating the number of C. Albicans that survived the direct current glow discharge and U-V light treatment was then determined using a microscope.

Results and Conclusion:

Group A samples exhibited proportionate decrease in the number of colonies with each greater time of exposure. Group B samples exhibited proportionate decrease in the number of colonies with each greater time of exposure. Group C samples exhibited total absence of C. Albicans colonies at 90 s exposure. In Group D samples there was a proportionate decrease in number of C. Albicans colonies with exposure to direct current glow discharge for more seconds. Hence, this study reveals that exposure to U-V light drastically reduced the C. Albicans colonies compared with exposure to direct current glow discharge. It was observed that with greater wattage of U-V light tube in U-V light unit chamber, greater decrease in colony count was observed in lesser time of exposure.

Efficacy of different disinfectant systems on alginate and addition silicone impression materials of Indian and international origin: a comparative evaluation

Study was planned to evaluate the efficacy of commonly used disinfectants and to study qualitatively and quantitatively the persistence of microflora on the untreated (control group) and the disinfected impression surface after 24 h. Disinfectant systems used were immersion systems like glutaraldehyde, sodium hypochlorite and the ultraviolet chamber. The effect of disinfectant on most commonly used Indian impression materials was carried out in this study and results compared with the most commonly used foreign brands for irreversible hydrocolloid and addition silicone. Impressions were made of 25 healthy volunteers. These were disinfected and incubated in an incubator for 24 h at 37°C for aerobic organisms. The inoculation in nutrient media was done to test the viability of microorganisms that can persist after rinsing and disinfection of the impression surface. The colony forming units were counted and compared with that of control group. Control group of all the impression material samples showed growth of Streptococcus viridans, Diphtheroids, Streptococcus pneumoniae to a greater extent. The growth of Candida albicans, Pseudomonas aerugenosa and Staphyloccus albus was present in all the groups but to a lesser extent. The persistence of the microflora on the impression surface of both the studied brands was similar but the concentration of organisms in the alginate control group was two folds as compared to addition silicone group. Use of ultraviolet chamber gave better results compared to the studied immersion systems. All the disinfection systems were effective in reducing the microbial load with ultraviolet chamber as the most effective.

Accuracy and stability of impression materials subjected to chemical disinfection - a literature review

Disinfection of impressions by immersion or spraying with disinfecting solutions is considered nowadays mandatory for effective infection control. The purpose of this review was to examine existing evidence on the effects that chemical disinfection may have on critical qualities of impressions, namely dimensional accuracy and stability over time. A PubMed search was conducted to include original laboratory research articles written in English, published between 1980 and 2005 in peer-reviewed journals and investigating the effect of chemical disinfection, by immersion or spraying, on the dimensional changes that the impression materials experience after setting. Studies were also sought manually, by tracing the references cited in the retrieved articles. The reports on dimensional changes of disinfected impression materials, although rather numerous, are difficult to compare and analyze because of variations of the experimental design. The investigations broadly agree that the disinfection process does not generally affect the dimensional integrity of the impressions, in spite of the statistically significant differences occasionally found. However, the immersion in the disinfecting solution encourages water absorption phenomena in the case of the so-called hydrophilic impression materials, especially after the long-term immersion. Chemical interactions between impressions and disinfectants may occur, but they do not appear to influence the dimensional behaviour of the former. The overall effect of the disinfection is influenced not only by the changes experienced by the impression per se, but also by the alterations of the acrylic tray containing the impression and of the gypsum product poured in it.

Effect of ultraviolet light irradiation on bonding of experimental composite resin artificial teeth

The purpose of the present study was to evaluate how ultraviolet light (UV) irradiation using an ordinary UV sterilizer would affect the bonding of experimental composite resins to an autopolymerizing acrylic resin. To this end, three composite resins and one unfilled resin--of which the compositions were similar to commercial composite resin artificial teeth--were prepared as repair composites. Their shear bond strengths after UV irradiation for one to 60 minutes were significantly greater than those before UV irradiation regardless of composite resin type. Failure mode after UV irradiation for one to 60 minutes was mainly cohesive failure of the composite resins, but that before UV irradiation and after 24 hours' irradiation was mainly adhesive failure. These results thus suggested that a short period of UV irradiation on composite resin teeth would improve the bonding efficacy of composite resin artificial teeth to autopolymerizing resin.

Ultraviolet disinfection with a novel microwave-powered device

AIMS

To evaluate the antimicrobial efficacy of a novel u.v. beaker, powered in a domestic microwave oven.

METHODS AND RESULTS

Three beakers were compared, with most rapid killing obtained in the Neutra Plasma 50. Ultraviolet light generated within the beakers efficiently killed planktonic and surface-associated Streptococcus mutans, Pseudomonas aeruginosa, vegetative Bacillus stearothermophilus, herpes simplex and polio viruses. Candida albicans and Mycobacterium phleii were less rapidly killed, and only 70% inactivation of B. stearothermophilus endospores was achieved. Irradiation for 45 s reduced viable bacterial counts in saliva by > 99%.

CONCLUSIONS

The u.v.-generating beakers efficiently reduced viable counts of bacteria, yeast and viruses. Kinetics of killing varied, reflecting the fact that lethal mechanisms are complex, and probably depend on interplay between u.v. and heat.

SIGNIFICANCE AND IMPACT OF THE STUDY

This novel method of generating u.v., using a cheap and widely available power source, provides a rapid, inexpensive and non-toxic method of disinfection with a wide range of applications in hospitals, clinics and the home.