ORIGINAL RESEARCH


https://doi.org/10.5005/jp-journals-10015-1910
World Journal of Dentistry
Volume 13 | Issue 2 | Year 2022

Influence of Disinfectants Use on Removable Oral Prosthesis: An In Vitro Study


Anjana Raut1, Aswini K Kar2, Arun Mohanty3, Sadananda Hota4, Purnendu Bhushan5, Sunayana Priyadarshini6

1-5Department of Prosthodontics, Kalinga Institute of Dental Sciences, KIIT (Deemed to be University), Bhubaneswar, Odisha, India

6Department of Prosthodontics, Hi-Tech Dental College and Hospital, Bhubaneswar, Odisha, India

Corresponding Author: Anjana Raut, Department of Prosthodontics, Kalinga Institute of Dental Sciences, KIIT (Deemed to be University), Bhubaneswar, Odisha, India, Phone: +91 9937036822, e-mail: anjana.raut@kids.ac.in

ABSTRACT

Aim and objective: The purpose of this study was to compare the dimensional stability of heat cured acrylic denture base resin before and after disinfecting with different disinfectants.

Materials and methods: Seventy heat cured acrylic samples were made from a preformed stainless steel metal die of dimensions 65x10x3 mm.The linear dimensions were measured before and after immersion (24 hours) in six different disinfectants with an electronic digital vernier caliper. The data was analyzed statistically using paired t- test and one-way ANOVA, Dunnette T- test.

Results: It was found that the heat cure acrylic samples did not produce any statistical changes (p > 0.05) in their linear dimension, upon immersion in six different disinfectant solutions.

Conclusion: It was found that all the disinfectants showed some amount of linear changes, but statistically insignificant (p > 0.05). Therefore, the present study strongly recommends standard disinfection protocol for all removable oral prosthesis used intra-orally to combat virulent microorganisms.

Clinical significance: Acrylic resins are most widely used for denture prosthesis for patients with missing teeth. Procedures like adjustment and denture repair produce fine particles that can be hazardous to the dental professional. It is very important to disinfect the denture to prevent cross-contamination against virulent pathogens to avoid air-borne infections. So it is necessary to know the physical changes in acrylic resin caused due to immersion in potent biocidal agents. Owing to the porous nature of denture base resin there is inherent property to absorb water and likely to undergo dimensional changes.

How to cite this article: Raut A, Kar AK, Mohanty AK, et al. Influence of Disinfectants Use on Removable Oral Prosthesis: An In Vitro Study. World J Dent 2022;13(2):166–171.

Source of support: Nil

Conflict of interest: None

Keywords: Denture base resin, dimensional stability, infection control, microorganisms, removable prosthesis

INTRODUCTION

Geriatric population due to predisposing medical conditions and comorbid state are vulnerable to air-borne infections. They are more likely to fall sick requiring hospitalization and intensive care owing to their medically- compromised systemic health. Amidst such unfavorable times oral health care needs to be addressed by everyone.

Polymethylmethacrylate (PMMA) is one of the most widely used material for denture prosthesis in geriatric patients.1 Chemical disinfection is highly effective in controlling commonly found fungi and bacteria present in the mouth. Moreover, the present pandemic has been an eye-opener towards strong disinfection and cleaning of dentures prior to intraoral use.2,3,4 Patients using removable oral prosthesis lack awareness pertaining to its duration of immersion in potent disinfectants before cleaning with toothbrush. Denture surface disinfection will minimize microbial adherence to the resin matrix and avoid cross contamination in the clinical and laboratory setup.

Dimensional stability of acrylic dentures is mainly influenced by thickness of the base, residual monomer, processing technique rather than volumetric expansion due to water sorption. Their tendency to absorb water indeed causes dimensional changes but they may not be statistically significant at times. Therefore, it is desirable to have dentures with optimum polymerization and minimal residual monomer for low water sorption. The immersion in denture disinfectants is essential for preventing cross contamination. However, there is no clarity whether disinfectants can induce significant linear changes.

The aim of the present study was to assess the dimensional stability of denture base resin (PMMA) after immersion in six different disinfectants. The null hypothesis stated there was no statistically significant difference in linear dimensions of the samples after immersion in different disinfectants.

MATERIALS AND METHODS

The present study was conducted in the Department of Prosthodontics, Kalinga Institute of Dental Sciences, KIIT-DU, Bhubaneswar, Odisha, India.

Preparation of Gypsum Molds

Four dental stone molds were prepared with preformed stainless steel metal dies which had dimensions of 65 mm in length, 10 mm in width and thickness of 3 mm.5 The dies were lubricated and were flasked using dental stone in a dental flask. The flask was closed and ensured no gap existed between metal segments of the flask. The mold cavities thus obtained were used for the preparation of heat activated acrylic resin samples.

Preparation of Resin Samples

The mix of PMMA was prepared in a mixing jar as per the manufacturer’s instructions (10 g of polymer in 4.5 mL of monomer) packed in the mold in dough stage. The trial closures were carried out using the hydropress and cellophane sheets until no flash was obtained. Later the flask was clamped and left for 1 hour before curing. The flask was immersed in water for acrylization.

Polymerization was accomplished by immersion in a water bath for 9 hours at 74°C. To avoid distortions the flask was cooled to room temperature and then deflasked. The acrylic samples were then retrieved, finished, and polished using sand paper. The dimensions and quality of the samples were verified. Seventy specimens were prepared in the similar manner. Thus the obtained seventy specimens were divided into seven groups as below:

  • Group 1: Ten specimens immersed in distilled water for 24 hours and used as control (no disinfection) group.

  • Group 2: Ten specimens were placed in 2% glutaraldehyde solution for 24 hours.

  • Group 3: Ten specimens were placed in 2% chlorhexidine gluconate solution for 24 hours.

  • Group 4: Ten specimens were placed in 1% sodium hypochlorite solution for 24 hours.

  • Group 5: Ten specimens were placed in 3.8% sodium perborate solution for 24 hours.

  • Group 6: Ten samples were placed in 7.5% povidone iodine solution for 24 hours.

  • Group 7: Ten samples were placed in 2% povidone iodine solution for 24 hours.

Measurement of Dimensional Stability

Specimens were evaluated for linear dimensional changes. The resulting linear changes were estimated by making measurements across the longest side (65 mm) of each specimen before and after disinfection.6 For this all samples of Group 1-7 were marked across the length in three lines and the length was measured. An electronic digital Vernier caliper (accuracy to 0.01 mm, Yuri Silver) was used to measure the samples. The average of three readings was taken. Later the disinfection protocol was followed as mentioned and the measurements were repeated. The average of the three readings was reported and the difference in the measurement was calculated.

Statistical Analysis

The data was analysed using SPSS Software version 16 of SPSS inc. The pairwise comparison of mean linear dimensions is done by using paired sample t-test. The comparison of mean difference before and after among the groups by one-way ANOVA. The comparison of mean difference in the disinfectant group with the control group was done by Dunnette T test.

RESULTS

The results of the present study are as follows:

Table 1 represents the data of average linear dimension of heat activated denture base resin before and after immersion (24 hours) in control agent and six disinfectants.

Table 1: Average linear measurements of heat cured acrylic samples before and after immersion
Linear Mean Standard deviation
Distilled water (control) Linear measurement before 64.72 0.116
Linear measurement after 64.73 0.101
2% Glutaraldehyde Linear measurement before 64.71 0.059
Linear measurement after 64.73 0.072
2% Chlorhexidine gluconate Linear measurement before 64.85 0.151
Linear measurement after 64.86 0.141
1% Sodium hypochlorite Linear measurement before 64.84 0.106
Linear measurement after 64.86 0.097
3.8% Sodium perborate Linear measurement before 64.84 0.106
Linear measurement after 64.86 0.097
7.5% Povidone iodine Linear measurement before 64.66 0.067
Linear measurement after 64.76 0.048
2% Povidone iodine Linear measurement before 64.77 0.047
Linear measurement after 64.78 0.052

So, the disinfectants did not produce statistical changes in linear dimension of heat cured acrylic resin.

Figure 1 depicts the bar diagram of average linear dimensions of heat activated denture base resin before and after immersion.

Fig. 1: Average linear measurements of acrylic samples before and after immersion

Table 2 shows paired sample t-test for comparison of linear measurement before and after immersion. The statistical significance of mean difference of all the groups before and after immersion has been statistically not significant.

Table 2: Paired sample "t" test for comparison of linear measurements of heat cured acrylic samples before and after immersion
Groups Mean difference before and after Standard deviation 95% Confidence interval of the difference t p
Lower Upper
Distilled water (control) -0.010 0.052 -0.037 0.037 0.000 0.988
2% Glutaraldehyde -0.020 0.027 -0.019 0.019 0.000 0.978
2% Chlorhexidine gluconate -0.010 0.052 -0.027 0.047 0.605 0.560
1% Sodium hypochlorite -0.020 0.055 -0.059 0.019 -1.152 0.279
3.8% Sodium perborate -0.020 0.055 -0.059 0.019 -1.152 0.279
7.5% Povidone iodine -0.100 0.027 -0.019 0.019 0.000 0.980
2% Povidone iodine 0.017 0.042 -0.014 0.047 1.246 0.244

Table 3 shows the comparison of mean linear difference of heat cured acrylic samples before and after immersion among the groups. Analysis of variance revealed that the mean linear difference among the seven groups did not differ significantly with a p -value 0.492. The values have been graphically shown in Figure 2.

Table 3: Comparison of mean linear difference before and after among the groups
Groups Mean Standard deviation 95% Confidence interval of the difference p
Lower Upper
Linear difference Distilled water (control) −0.010 0.052 -0.037 0.037 0.492
2% Glutaraldehyde −0.020 0.027 -0.020 0.020
2% Chlorhexidine gluconate −0.010 0.052 -0.027 0.047
1% Sodium hypochlorite −0.020 0.055 -0.059 0.019
3.8% Sodium perborate −0.020 0.055 -0.059 0.019
7.5% Povidone iodine −0.100 0.027 -0.020 0.020
2% Povidone iodine 0.017 0.042 -0.014 0.047

Fig. 2: Mean linear difference before and after among the groups

Table 4 presents the comparison of mean difference of linear measurements with the control group. Each of the comparison revealed that none of the disinfectants had statistically significant difference.

Table 4: Comparison of mean difference of linear measurements with control group
Groups Mean difference Standard error mean 95% Confidence interval of the difference p
Lower Upper
Linear difference 2% Glutaraldehyde Control 0.000 0.021 -0.054 0.054 1.000
2% Chlorhexidine gluconate Control 0.010 0.021 -0.044 0.064 0.993
1% Sodium hypochlorite Control -0.020 0.021 -0.074 0.034 0.836
3.8% Sodium perborate Control -0.020 0.021 -0.074 0.034 0.836
7.5% Povidone iodine Control 0.000 0.021 -0.054 0.054 1.000
2% Povidone iodine Control 0.017 0.021 -0.038 0.071 0.918

* The mean difference is significant at the 0.05 level

DISCUSSION

Infectious diseases have become a major concern in the field of health care in the recent pandemic period. Cross-infection from the patients to the dental professionals are through intraoral impressions, unsterilized trays, models, and the dental prostheses.7

The objective of disinfection/sterilization of any oral prosthesis is to achieve microbe-free surface or clinically inactive biofilm. The process should not involve any topographic or chemical changes in the denture, that is, alterations in linear dimension, flexural strength, surface hardness, and/or color.

The present study design attempts to assess the linear dimensional changes of denture base resin (PMMA) after immersion in distilled water, 2% glutaraldehyde, 2% chlorhexidine gluconate, 1% sodium hypochlorite, 3.8% sodium hypochlorite, 7.5% povidone iodine, 2% povidone iodine for 24 hours. Seventy acrylic samples were used in the present study. After the specified time was passed all the specimens were tested for linear dimensional changes. Chemical decontamination of dentures is commonly performed by immersing in alkaline glutaraldehyde, hypochlorite, aqueous formaldehyde, or enzymatic solutions for fixed duration of period.

Disinfectant used should cause no damage to the properties of the resin. There are many ways of disinfection recommended for dental office and laboratory before offering treatment to patients. Moreover, oral prosthesis is heat labile so only chemical disinfection is possible for them. The Council on Dental Therapeutics recommends disinfectants belonging to four categories namely chlorine solutions, formaldehyde, glutaraldehyde, and iodophors.8 However, chemical disinfectant solutions suitable for immersion of dental prostheses include: sodium hypochlorite, glutaraldehyde, chlorine dioxide, and chlorhexidine.9,10,11 Chlorhexidine is potent topical antiseptic, effective in high dilutions against a wide range of gram-positive, gram-negative bacteria, yeast, fungi, facultative anaerobes, and aerobes. Major demerit of such chemical solutions is the brownish discoloration of the prosthetic teeth and the acrylic denture base.9,11,12

Dimensional Change Analysis

The present study strongly agrees with the results of previously done study wherein it was reported that specimens of heat cured acrylic resin showed insignificant dimensional change after disinfection and were clinically irrelevant.6 This study was also in agreement with the result of another study where it was reported that dimensional changes exhibited between different chemical agents (disinfectants) were also statistically insignificant.13 The alcohol based chemical disinfectants may reduce flexural strength and staining may result due to chlorhexidine, long soaking in hypochlorite may cause bleaching.14 Another group of researchers mentioned the CDC recommendation using 0.05-0.5% sodium hypochlorite as an effective virocidal agent.15 Ten minutes immersion in 5.25% sodium hypochlorite was found to be effective against all microorganisms including spores.16,17According to results of the present study, there was no statistically significant effect of chlorhexidine gluconate and sodium hypochlorite on the dimensions of acrylic denture base resin which was in agreement with the study outcomes of Hussen et al.9

The dimensional accuracy and intraoral stability is important for the proper fit of the denture and patient satisfaction while chewing.18 There is controversy regarding the varied results of immersion in disinfectants as reported by many previous studies pertaining to physical prWoperties and clinical performance of complete and partial dentures. So it is important to know the effects of various disinfection methods for the same.14 The dimensions of the samples selected for the present study were as per the ISO 1567 standards that is 65 x 10 x 3 mm.5 Another group of researchers discussed about various acceptable methods of measuring dimensional changes which included, dial calipers, gauges, optical comparators, optical micrometers, radiographs, microscopes, or a travelling stage microscope.19

In the present study, testing of the samples for linear changes is done by making measurements across the longest side (65 mm) of each specimen before and after disinfection procedure was done using an electronic digital caliper with an accuracy of 0.01 mm. Dixon et al.20 studied the shrinkage of resin during curing and it’s expansion during storage in water. They experimented on few resins. However, only accelar 20 showed expansion during water immersion, though the changes were very small.

Similarly, the outcome of the present study showed increase in the value which was statistically insignificant. When placed in an aqueous environment denture base resin exhibited water sorption. The introduction of the water molecule within the polymerized mass causes slight expansion of the resin matrix.21 Heat cured dentures stored in water showed linear expansion of 0.1-0.2% which partially compensates for the processing shrinkage that is 0.3-0.4%. The major change in water takes place for the 1st month and the changes are insignificant after 2 months.18 The linear dimension of samples immersed in sodium hypochlorite did not show any significant changes. The study done by Sartori and Schmidt showed that immersion in chloride solution did not vary from control group in dimensional changes which was in agreement with the results of the present study.14

Five percent povidone iodine was used as a disinfectant solution for assessment of linear dimensional variations and surface texture of gypsum casts retrieved from disinfected elastomeric impressions at varied intervals. The dimensional accuracy and surface quality remained relatively unchanged after dipping in disinfectants.22 In the present study 2% povidone iodine which is readily available in the market as betadine mouthwash, and 7.5% povidone iodine which is available in the market as surgical scrub were used as disinfectants. No similar reports in the literature search coincide with the use of same materials and testing protocol that might allow a direct comparison to this study. Though there were linear changes by disinfection of acrylic resin by 2% povidone iodine and 7.5% povidone iodine in the present study but the results were found statistically insignificant, which was in agreement with the results of previous study where 1% povidone iodine was used as a disinfectant for determination of dimensional change.13

All the disinfectants used in the present study were available commercially and they were safe and suitable for disinfection of acrylic dentures both by denture wearers and dental professionals.

Limitations of the Study

An in vitro test may not always reflect dynamic intraoral conditions and cannot absolutely predict clinical performance; they are still useful in gaining and understanding knowledge. Simple rectangular specimens were used rather than a complex denture design to study dimensional stability. Secondly, the study used only few disinfectants, there is need to investigate their efficacy in chronic usage of dentures. Further studies are needed to evaluate other physical and mechanical properties of heat activated denture base resin on immersion in different disinfectants for 24 hours.

CONCLUSION

Within the limitations of this study, all the disinfectants showed some amount of linear changes, however were found to be statistically insignificant (p > 0.05) in causing clinically appreciable dimensional changes. Therefore, the study strongly recommends routine use of disinfectants for removable oral prosthesis to fight cross contamination and prevent spread of infection.

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