Effect of Ultraviolet Radiation on Candida albicans Biofilm on Poly(methylmethacrylate) Resin

Ultraviolet C as a method of disinfecting medical silicone used in facial prostheses: An in vitro study - Part 2

STATEMENT OF PROBLEM

Disinfection is an important factor in preserving facial prostheses and maintaining tissue health. However, whether disinfection with ultraviolet C is an effective disinfection method is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effectiveness of irradiation with different exposure durations of an ultraviolet-C light-emitting diode in the disinfection of the silicone (A-588-1; Factor II) used in facial prostheses.

MATERIAL AND METHODS

A total of 216 specimens were prepared, contaminated by multispecies biofilm, and divided into 9 groups (n=24) for different treatments: chlorhexidine 0.12% (G CHG), ultraviolet-C light-emitting diode for 5 minutes (G UVC5), ultraviolet-C light-emitting diode for 10 minutes (G UVC10), ultraviolet-C light-emitting diode for 20 minutes (G UVC20), their respective untreated controls (Gcontrol CHG, Gcontrol UVC5, Gcontrol UVC10, Gcontrol UVC20), and dimethyl sulfoxide (G DMSO) as the negative control. Cell viability was measured by using the methyl tetrazolium salt (MTT) method. Two statistical analyses were performed. First, a 2×3 ANOVA was carried out to compare the control groups (Gcontrol UVC5, Gcontrol UVC10, and Gcontrol UVC20) and the experimental groups of UV-C LED light with different exposure durations (G UVC5, G UVC10, and G UVC20). The second analysis was performed using generalized linear models to compare the optical density of the groups (G UVC5, G UVC10, G UVC20, G CHG, and G DMSO).

RESULTS

Cell viability results demonstrated a microbial reduction after exposure to the ultraviolet-C light-emitting diode for 20 minutes (G UVC20) compared with untreated controls (P<.05). The 5- and 10-minute exposures were statistically similar to their respective control groups (P>.05). The 20 minutes exposure had the lowest average optical density value, being statistically different from the 5-minute exposure (P<.05). A 20-minute exposure to the ultraviolet-C light-emitting diode (G UVC20) was similarly effective when compared with the standard disinfection treatment (G CHG) and dimethyl sulfoxide (G DMSO) (P>.05).

CONCLUSIONS

Irradiation with an ultraviolet-C light-emitting diode for 20 minutes decreased the in vitro microbial cell viability on the medical silicone used in facial prostheses.

Effect of Ultraviolet-C Light Exposure Time on the Dimensional Stability of Addition Silicone Dental Impressions: An In Vitro Study

AIM

To compare the effect of different ultraviolet-C (UV-C) light exposure times on the dimensional stability of addition silicone dental impressions.

MATERIALS AND METHODS

The dimensional stability of the addition silicone dental impressions was assessed by measuring specific dimensions on dental casts that were recovered from an upper acrylic resin model of dental implants. The impressions were reproduced using a customized tray adapted in a three-point simplex dental articulator permitting only opening and closing movements. Addition silicone dental impressions were divided into five groups (N = 12) according to the UV-C light exposure time. Group A was untreated; group B received 10 minutes; group C, 20 minutes; group D, 30 minutes; and group E, 40 minutes. All the impressions were poured with type IV dental stone and the internal edges of the upper silicone retainers of impression copings were used as five reference points (E, D, C, B, and A) to determine six linear measurements between ED, CB, EA, AD, EB, and CD points using a traveling microscope of 0.001 mm accuracy. One-way analysis of variance (ANOVA) was used for the statistical analysis (p < 0.05).

RESULTS

Expansion and contraction were noted among ED, CB, EA, and EB measurements, whereas only expansion was noted among AD and CD measurements. The ANOVA analysis showed there was no significant difference in the arithmetic means for the measurements between and within group A and the other groups (p > 0.05).

CONCLUSION

The UV-C light exposure time of 10, 20, 30, and 40 minutes did not have any negative effect on the dimensional stability of the addition silicone dental impressions evaluated.

CLINICAL SIGNIFICANCE

In the daily routine dental practice, dental impressions need to be washed and disinfected immediately after making to prevent cross-infections. The UV-C light has been proposed as a promising method for disinfection, but only a few studies have been published about its effect on the dimensional stability of dental silicones. How to cite this article: Bravo-Cueto AG, Tinedo-López PL, Malpartida-Carrillo V. Effect of Ultraviolet-C Light Exposure Time on the Dimensional Stability of Addition Silicone Dental Impressions: An In Vitro Study. J Contemp Dent Pract 2024;25(6):507-513.

Plasma-activated liquids for mitigating biofilms on food and food contact surfaces

Plasma-activated liquids (PALs) are emerging and promising alternatives to traditional decontamination technologies and have evolved as a new technology for applications in food, agriculture, and medicine. Contamination caused by foodborne pathogens and their biofilms has posed challenges and concerns to the food industry in terms of safety and quality. The nature of the food and the food processing environment are major factors that contribute to the growth of various microorganisms, followed by the biofilm characteristics that ensure their survival in severe environmental conditions and against traditional chemical disinfectants. PALs show an efficient impact against microorganisms and their biofilms, with various reactive species (short- and long-lived ones), physiochemical properties, and plasma processing factors playing a crucial role in mitigating biofilms. Moreover, there is potential to improve and optimize disinfection strategies using a combination of PALs with other technologies for the inactivation of biofilms. The overarching aim of this study is to build a better understanding of the parameters that govern the liquid chemistry generated in a liquid exposed to plasma and how these translate into biological effects on biofilms. This review provides a current understanding of PALs-mediated mechanisms of action on biofilms; however, the precise inactivation mechanism is still not clear and is an important part of the research. Implementation of PALs in the food industry could help overcome the disinfection hurdles and can enhance biofilm inactivation efficacy. Future perspectives in this field to expand existing state of the art to seek breakthroughs for scale-up and implementation of PALs technology in the food industry are also discussed.

Advances in application of ultraviolet irradiation for biofilm control in water and wastewater infrastructure

Biofilms are ubiquitous in aquatic environment. While so far, most of the ultraviolet (UV) disinfection studies focus on planktonic bacteria, and only limited attention has been given to UV irradiation on biofilms. To enrich this knowledge, the present paper reviews the up-to-date studies about applying UV to control biofilms in water and wastewater infrastructure. The development of UV light sources from the conventional mercury lamp to the light emitting diode (LED), and the resistance mechanisms of biofilms to UV are summarized, respectively. Then the feasibility to control biofilms with UV is discussed in terms of three technical routes: causing biofilm slough, inhibiting biofilm formation, and inactivating bacteria in the established biofilm. A comprehensive evaluation of the biofilm-targeted UV technologies currently used or potentially useful in water industry is provided as well, after comparative analyses on single/combined wavelengths, continuous/pulsed irradiation, and instant/chronic disinfection effects. UV LEDs are emerging as competitive light sources because of advantages such as possible selection of wavelengths, adjustable emitting mode and the designable configuration. They still, however, face challenges arising from the low wall plug efficiency and power output. At last, the implementation of the UV-based advanced oxidation processes in controlling biofilms on artificial surfaces is overviewed and their synergistic mechanisms are proposed, which further enlightens the prospective of UV in dealing with the biofilm issue in water infrastructure.

Ultraviolet C as a method of disinfecting medical silicone used in facial prostheses: An in vitro study

STATEMENT OF PROBLEM

Hygiene and disinfection are important factors for preserving facial prostheses and supporting tissue health. However, a method that does not accelerate degradation or color change is necessary.

PURPOSE

The purpose of this in vitro study was to evaluate the effectiveness of irradiation with ultraviolet C light-emitting diode (UV-C LED) light in the disinfection and initial color stability of the silicone (A-588-1; Factor II) used in facial prostheses.

MATERIAL AND METHODS

One hundred and twenty specimens were made, contaminated by multispecies biofilm, and divided into 5 groups (n = 24) with different treatments: control, distilled water, 0.12% chlorhexidine, UV-C LED light, and dimethyl sulfoxide (DMSO) as the negative control. Cell viability was measured by the methyl tetrazolium salt method. Statistical analysis was performed by generalized linear models. Additional descriptive analysis was performed for color analysis by using 16 silicone specimens made with light and dark intrinsic coloring in 4 groups (controls and treatments n=4) submitted to UV-C LED light. The ΔE of the specimens was obtained by CIEDE200.

RESULTS

The results of cell viability demonstrated a statistically significant difference among the groups (P<.001), with a microbial reduction after UVC-LED exposure compared with the control group. Regarding the color, the groups presented an average ΔE (light 0.205 and dark 0.308) compatible with visually imperceptible changes (light < 0.7 and dark < 1.2).

CONCLUSIONS

Irradiation with UV-C LED light decreased the in vitro microbial cell viability of the medical silicone used in facial prostheses, demonstrating initial color stability.