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DENTAL SCIENCE - ORIGINAL ARTICLE
Year : 2013  |  Volume : 5  |  Issue : 5  |  Page : 80-84  

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


Department of Prosthodontics, Sathyabama University Dental College and Hospital, Chennai, Tamil Nadu, India

Date of Submission02-May-2013
Date of Decision04-May-2013
Date of Acceptance04-May-2013
Date of Web Publication13-Jun-2013

Correspondence Address:
Vijay Anand
Department of Prosthodontics, Sathyabama University Dental College and Hospital, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0975-7406.113302

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   Abstract 

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.

Keywords: Candida albicans , elastomers, impression, ultra-violet light


How to cite this article:
Anand V. 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. J Pharm Bioall Sci 2013;5, Suppl S1:80-4

How to cite this URL:
Anand V. 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. J Pharm Bioall Sci [serial online] 2013 [cited 2022 Dec 1];5, Suppl S1:80-4. Available from: https://www.jpbsonline.org/text.asp?2013/5/5/80/113302

"Primum non nocere" (In the first place do no wrong) has been one of the fundamental principles in the practice of medicine. Infection control is an imperative practice in Prosthodontics if one has to follow the afore mentioned dictum. Dental impressions [1],[2] serve as a source of infectious microorganisms to dental personnel who handle the impressions or casts made from them. Many pathogenic microorganisms as well as opportunistic pathogens can be transmitted by impressions. The standard procedure [3],[4] of rinsing impressions under tap water immediately after removal from the mouth, eliminates gross contamination along with most saliva and blood. However, not all microorganisms are removed and they can be a source of infection. Since sterilization of impressions is expensive, time consuming, and may be potentially damaging to the material, surface disinfection with various chemicals has become an alternative.

The prevalence of candidal stomatitis among patients has been reported as varying between 9% and 97%. [5] Candida Albicans plays an important role as the major cause of microbial origin in denture related stomatitis. C. Albicans is an ovoid or spherical budding cell, which produces pseudomycelia both in culture and in tissues. Candidiasis is an opportunistic endogenous infection, the commonest predisposing factor being diabetes. Systemic infections such as septicemia, endocarditis and meningitis may occur as terminal complications. Candida granuloma and chronic mucocutaneous candidiasis are serious manifestations seen in immuno deficiencies. Bacterial and fungal plaque on dentures may lead to such serious infections.

Immersion disinfection, sonication with disinfectants, microwave irradiation, ultra-violet light (U-V light) exposure, have all been suggested as methods to disinfect impressions. Dental impression materials vary in dimensional stability with time and humidity. Hence, many are unsuitable for immersion in disinfectant solutions. The potential for distortion is of major concern when procedures for disinfection of dental impressions are considered. A review of recent literature [5],[6],[7] indicated a lack of consensus among researchers regarding the best method for disinfection procedure of impression materials. Although the efficacy of U-V light as a sterilizer for hand pieces or dental materials has been reported, the effect of U-V light on dental impression materials has not much been researched. So the present study has been designed to evaluate the effect of Ultra violet light exposure and direct current glow discharge exposure on C. Albicans colonies when impression material is coated with Candidal colonies.


   Aims and Objectives Top


The aims and objectives of our study includes:

  1. To find out the efficacy of U-V light in causing decrease in colony count of C. Albicans.
  2. To find out the efficacy of direct current glow discharge in causing decrease in the colony count of C. Albicans.
  3. To find out the relative efficacy of U-V light exposure on C. Albicans when varying wattage is used.
  4. To find out the relative efficacy of U-V light exposure on C. Albicans at varying times of exposure.
  5. To find out the relative efficacy of direct current glow discharge at different times of exposure.
  6. To find out the most suitable wattage of maximum efficacy when U-V light exposure is used to decrease the colony count of C. Albicans.
  7. To find out the appropriate time of exposure at which U-V light is efficient to kill C. Albicans.
  8. To find out the appropriate time of exposure at which direct current glow discharge is efficient in decreasing the colonies of C. Albicans.
  9. To comparatively evaluate the efficacy of U-V light and direct current glow discharge in decreasing the colonies of C. Albicans.

   Materials and Methods Top


Addition silicone elastomeric impression material samples (240 nos.), make of Aquasil (Caulk/Dentsply USA)

Medium body - type II were used in our study. C. Albicans culture and Nutrient broth (pH 5.6), Sabourauds Dextrose Agar and following equipment's U-V light unit and Direct current glow discharge unit were used. U-V light disinfection unit was designed based on similar equipment by Boylan et al., (1987). [4]

Nutrient broth and Sabourauds dextrose agar were prepared in routine manner. About 1 ml of the prepared nutrient broth was dispensed in a test tube and sterilized by autoclaving at 121°C for 10-15 min. The Sabourauds Dextrose Agar was dispensed on petri plates for the convenient incubation of the samples. A culture strain of C. Albicans isolated from oral lesions of human immunodeficiency virus patients was obtained from the department of microbiology, madras medical college. A loop full of the obtained culture was suspended in 1 ml nutrient broth (pH adjusted to 5.6) and incubated at 37°C for 2 h. The number of C. Albicans cells were estimated to be 105 cells/ml.

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

  • A 15-a to A 15-j
  • A 30-a to A 30-j
  • A 60-a to A 60-j
  • A 90-a to A 90-j
  • A 120-a to A 120-j
  • A 180-a to A 180-j
Similarly, Group B, C and D samples were designated for identification and use. 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.

Disinfection of C. Albicans with U-V light unit is done as follows . From the prepared C. Albicans cell suspension, 0.01 ml were spread on to addition silicone impression material samples using a calibrated wire loop of 4 mm diameter and exposed to U-V light at 15, 30, 60, 90, 120 and 180 s with 8, 16 and 24 Watts respectively. 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 U-V treatment was then determined with the help of microscope.

Procedure for disinfection of C. Albicans with direct current glow discharge unit is done as follows. From the prepared C. Albicans cell suspension, 0.01 ml were spread onto addition silicone impression material using a calibrated wire loop of 4 mm diameter and exposed to direct current glow discharge at 15, 30, 60, 90, 120 and 180 s respectively with vacuum pressure 0.1 m barr and current 1amp standardized. After exposure, the impression material was swabbed on 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 treatment was then determined using a microscope.


   Results Top


Mean and standard deviation were estimated from the sample for each study group. Mean values were compared between different study groups by either one way ANOVA followed by Tukey- Honestly significant difference (HSD) procedure or Student's independent t-test/Mann-Whitney u-test appropriately. In the present study, P < 0.005 was considered as the level of significance.

Inference 1

For Group A, the mean no of colonies at 15 s time (114.9 + 4.7) was significantly higher than 30 s time (88.8 + 4.6), 60 s time (66.8 + 4.8), 90 s time (24.2 + 5.3), 120 s time (2.6 + 1.2) and 180 s time (0.0 + 0.0) ( P < 0.05). Again, the mean no of colonies at 30 s time was significantly higher than 60 s, 90 s, 120 s and 180 s ( P < 0.05). Further, the mean no of colonies at 60 s time was significantly higher than 90 s, 120 s and 180 ( P < 0.05). Also, the mean no of colonies at 90 s time was significantly higher than 120 s and 180 s time ( P < 0.05). However, there was no significant difference in mean no of colonies between 120 s time and 180 s time.

Inference 2

For Group B, the mean no of colonies at 15 s time (55.1 + 5.1) was significantly higher than 30 s time (36.9 + 5.5), 60 s time (20.0 + 3.3), 90 s time (9.9 + 3.4), 120 s time (0.0 + 0.0) and 180 s time (0.0 + 0.0) ( P < 0.05). Again, the mean no of colonies at 30 s time was significantly higher than 60 s, 90 s, 120 s and 180 s ( P < 0.05). Further, the mean no of colonies at 60 s time was significantly higher than 90 s, 120 s and 180 ( P < 0.05). The mean no of colonies at 90 s time was significantly higher than 120 s and 180 s time ( P < 0.05). However, there was no significant difference in mean no of colonies between 120 s time and 180 s time.

Inference 3

For Group C, the mean no of colonies at 15 s time (25.3 + 6.1) was significantly higher than 30 s time (9.8 + 4.0), 60 s time (4.4 + 2.1), 90 s time (0.0 + 0.0), 120 s time (0.0 + 0.0) and 180 s time (0.0 + 0.0) ( P < 0.05). Again, the mean no of colonies at 30 s time was significantly higher than 60 s, 90 s, 120 s and 180 s ( P < 0.05). Further, the mean no of colonies at 60 s time was significantly higher than 90 s, 120 s and 180 ( P < 0.05). The mean no of colonies at 90 s time was significantly higher than 120 s and 180 s time ( P < 0.05). However, there was no significant difference in mean no of colonies between 120 s time and 180 s time.

Inference 4

For Group D, the mean no of colonies at 15 s time (314.5 + 16.9) was significantly higher than 30 s time (210.6 + 5.7), 60 s time (185.6 + 8.3), 90 s time (154.8 + 5.4), 120 s time (117.1 + 8.2) and 180 s time (82.3 + 9.4) ( P < 0.05). Again, the mean no of colonies at 30 s time was significantly higher than 60 s, 90 s, 120 s and 180 s ( P < 0.05). The mean no of colonies at 60 s time was significantly higher than 90 s, 120 s and 180 ( P < 0.05). The mean no of colonies at 90 s time was significantly higher than 120 s and 180 s time ( P < 0.05). Further the mean no of colonies at 120 s time was significantly higher than 180 s time.

Inference 5

For 15 s time, the mean no of colonies in Group 1 (114.9 + 4.7) was significantly higher than Group 2 (55.1 + 5.1) and Group 3 (25.3 + 6.1) ( P < 0.05). Further, the mean no of colonies in Group 2 (55.1 + 5.1) was significantly higher than Group 3 (25.3 + 6.1) ( P < 0.05). For 30 s time, the mean no of colonies in Group 1 (88.8 + 4.6) was significantly higher than Group 2 (36.9 + 5.5) and Group 3 (9.8 + 4.0) ( P < 0.05). Further, the mean no of colonies in Group 2 (36.9 + 5.5) was significantly higher than Group 3 (9.8 + 4.0) ( P < 0.05). For 60 s time, the mean no of colonies in Group 1 (66.8 + 4.8) was significantly higher than Group 2 (20.0 + 3.3) and Group 3 (4.4 + 2.1) ( P < 0.05). Further, the mean no of colonies in Group 2 (20.0 + 3.3) was significantly higher than Group 3 (4.4 + 201) ( P < 0.05). For 90 s time, the mean no of colonies in Group 1 (24.2 + 5.3) was significantly higher than Group 2 (9.9 + 3.4) and Group 3 (0.0 + 0.0) ( P < 0.05). Further, the mean no of colonies in Group 2 (9.9 + 3.4) was significantly higher than Group 3 (0.0 + 0.0) ( P < 0.05). For 120 s time, the mean no of colonies in Group 1 (2.6 + 1.2) was significantly higher than Group 2 (0.0 + 0.0) and Group 3 (0.0 + 0.0) ( P < 0.05). Further, the mean no of colonies in Group 2 (0.0 + 0.0) was significantly equal to Group 3 (0.0 + 0.0) ( P < 0.05). For 180 s time, the mean no of colonies in Group 1 (0.0 + 0.0) was significantly equal to Group 2 (0.0 + 0.0) and Group 3 (0.0 + 0.0) ( P < 0.05).

Inference 6

For 15 s time, the mean no of colonies in Group C (25.3 + 6.1) was significantly lower than Group D (314.5 + 16.9) ( P < 0.0001). For 30 s time, the mean no of colonies in Group C (9.8 + 4.0) was significantly lower than Group D (210.6 + 5.7) ( P < 0.0001). For 60 s time, the mean no of colonies in Group C (4.4 + 2.1) was significantly lower than Group D (185.6 + 8.3) ( P < 0.0001). For 90 s time, the mean no of colonies in Group C (0.0 + 0.0) was significantly lower than Group D (154.8 + 5.4) ( P < 0.0001). For 120 s time, the mean no of colonies in Group C (0.0 + 0.0) was significantly lower than Group D (117.1 + 8.2) ( P < 0.0001). For 180 s time, the mean no of colonies in Group C (0.0 + 0.0) was significantly lower than Group D (82.3 + 9.4) ( P < 0.0001).


   Discussion Top


Fungi are ubiquitous in the environment and some cause infection in humans. Some investigators report that C. Albicans is the most common cause of fungal infections in immuno compromised patients. [5] Estimates of the incidence of candida in oral flora of a normal population have been reported in the literature to be between 40% and 60%. These values could differ significantly in carcinoma patients and also in those who have immunocompromised status. Prosthodontist must prevent systemic candidiasis via nosocomial spread and for this, effective sterilization and disinfection must be carried out.

Many commercially available disinfectants [8] are used for immersion disinfection. Some disinfectant solutions may cause significant changes in impression, particularly with over exposure. These solutions may be corrosive to metals, produce irritating vapors, depending on the disinfectant used. Hence, alternatives methods for disinfection of impressions have been suggested and practiced.

Effectiveness of Ultra-violet [6] rays in disinfection depends on a number of factors. Among these are time, intensity, humidity and direct access to the organism. Since dental prostheses provide a number of sites for shielding microorganisms from direct exposure to U-V light from only one direction, it is imperative that, U-V light must be reflected so that items within the disinfection unit will be exposed to U-V radiation from many directions. Frequent orientation of an item between exposures in the unit also increases the chances of killing microorganisms that may be "shadowed". [4]

Plasma treatment is a safe and environmentally friendly alternative to traditional cleaning methods. Plasma technology has also been considered for disinfection and sterilization of medical devices. Plasma can be defined as a partially or wholly ionized gas with a roughly equal number of positively and negatively charged particles. The most convenient aspect of plasma technology is the potential for simultaneous surface modification and sterilization in biomedical device fabrication. Plasma sterilization may be suitable for medical implants and devices that are sensitive to temperature, radiation and chemicals. In the plasma surface modification process, glow discharge plasma is created by evacuating a reaction chamber and then refilling it with a low-pressure gas. The gas is then energized by one of the following types of energy: Radio frequency, microwaves, alternating current or direct current. The present study evaluated direct current glow discharge method.

This comparative study was undertaken and the relative efficacy of direct current glow discharge and U-V disinfection unit was evaluated. The ability to decrease the colonies of C. Albicans species was studied.

Results revealed that, Group A samples which were exposed to U-V light with 8 watts, exhibited proportionate decrease in the number of colonies with each greater time of exposure. The number of colonies of C. Albicans was totally decreased to zero when 180 s exposure was used. Group B samples which were exposed to U-V light with 16 watts, exhibited proportionate decrease in the number of colonies with each greater time of exposure. The number of colonies of C. Albicans was totally decreased to zero when 120 s exposure was used. Group C samples, which were exposed to U-V light with 24 watts, exhibited total absence of C. Albicans colonies at 90 s exposure.

When U-V light exposure was used, the most suitable wattage of maximum efficacy resulting in total absence of C. Albicans colonies was 3750 μw/cm 2 . The appropriate time of exposure at which U-V light was efficient to kill C. Albicans maximally was 90 s, when 24 watt tube (3750 μw/cm 2 ) was used.

As far as Group D samples were concerned, (samples exposed to direct current glow discharge) there was a proportionate decrease in number of C. Albicans colonies with exposure to direct current glow discharge for more seconds. It was also observed that at the maximum time of 180 s of exposure to direct current glow discharge, the mean number of colonies was 82.3 + 9.4 ( P < 0.05). while, with U-V light, mean number of colonies at 90 s exposure with wattage of 24 was zero.

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. The results of the study are in agreement with the studies by Ishida, et al. (1991) [5] and Robert Boylan, et al. (1987). [4]

Thus, the present study clearly reveals the efficacy of ultraviolet light in disinfecting the surface of elastomeric impression by decreasing the colony counts of C. Albicans coated over the surface of an elastomeric impression material.


   Summary Top


This study was done to evaluate the efficacy of U-V light and direct current glow discharge in decreasing the colony counts of C. Albicans after coating the elastomeric impression material with C. Albicans colonies. A circular steel master die (dimensions: Diameter-30 mm, thickness-3 mm) was fabricated. Samples were prepared with addition silicone medium body material (aquasil). They were coated with C. Albicans colonies with standardization. Three different tubes were used in U-V light unit corresponding to 8 watts, 16 watts, and 24 watts. This permitted differential wattage application in the chamber. The times of exposure were 15, 30, 60, 90, 120 and 180 s. Similar method in timing the exposure was followed while using direct current glow discharge exposure to samples.

The results were tabulated and statistically analyzed. It was found that U-V light exposure more efficiently decreases the colony counts of C. Albicans on samples than direct current glow discharge exposure.


   Conclusion Top


In the present study, the comparative analysis of the efficacy of U-V light exposure and direct current glow discharge exposure, in decreasing the colony counts of C. Albicans was made with variable times of exposure and varying wattage application in the U-V light unit. The following conclusions are drawn from the study.

  1. Exposure to direct current glow discharge maximally decreased the count of C. Albicans colonies.
  2. Exposure to U-V light more effectively decreased the count of C. Albicans colonies.
  3. The maximum killing efficiency with U-V light exposure was observed with 24 watts (3750 μw/cm 2 )
  4. The greater the wattage used, the lesser was the time required to decrease the colony count of C. Albicans to zero.
  5. By comparison, U-V light could be a better method of disinfection than direct current glow discharge.


 
   References Top

1.Thouati A, Deveaux E, Iost A, Behin P. Dimensional stability of seven elastomeric impression materials immersed in disinfectants. J Prosthet Dent 1996;76:8-14.  Back to cited text no. 1
    
2.Shipman B. Clinical evaluation of oral Candida in cancer chemotherapy patients. J Prosthet Dent 1979;41:63-7.  Back to cited text no. 2
    
3.Baysan A, Whiley R, Wright PS. Use of microwave energy to disinfect a long-term soft lining material contaminated with Candida albicans or staphylococcus aureus. J Prosthet Dent 1998;79:454-8.  Back to cited text no. 3
    
4.Boylan RJ, Goldstein GR, Schulman A. Evaluation of an ultraviolet disinfection unit. J Prosthet Dent 1987;58:650-4.  Back to cited text no. 4
    
5.Ishida H, Nahara Y, Tamamoto M, Hamada T. The fungicidal effect of ultraviolet light on impression materials. J Prosthet Dent 1991;65:532-5.  Back to cited text no. 5
    
6.Spire B, Dormont D, Barré-Sinoussi F, Montagnier L, Chermann JC. Inactivation of lymphadenopathy-associated virus by heat, gamma rays, and ultraviolet light. Lancet 1985;1:188-9.  Back to cited text no. 6
    
7.Connor C. Cross-contamination control in prosthodontic practice. Int J Prosthodont 1991;4:337-44.  Back to cited text no. 7
    
8.Guidelines for infection control in the dental office and the commercial dental laboratory. Council on dental therapeutics. Council on prosthetic services and dental laboratory relations. J Am Dent Assoc 1985;110:969-72.  Back to cited text no. 8
    



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