An In Vitro Study to Compare the Surface Roughness of Two Polyvinylsiloxane Impression Materials Following Ultraviolet Irradiation or Chemical Disinfection

INTRODUCTION

Impression materials in dentistry are used to register the form and relation of the teeth and the surrounding oral tissues. To prevent the possible spread of infectious diseases like HIV AIDS, Hepatitis B, etc., the American Dental Association (ADA) and the Centers for Disease Control (CDC) have recommended disinfection of dental impressions.^1,2 A number of physical and chemical methods have been proposed for the disinfection of dental impressions. Physical action yields an increase in temperature, which may result in distortion of impression materials, and hence chemical disinfection is believed to be the simplest and an effective form of infection control. As per the ADA guidelines, the impression must be rinsed thoroughly to remove saliva, blood, and debris. This is followed by immersion in a disinfecting agent like glutaraldehyde, iodophor, or hypochlorite.³

Certain microbial forms, for instance, bacterial spores, are not eliminated by chemical disinfection alone. Hence, alternative methods have been introduced such as steam autoclave, microwave, ethylene oxide gas autoclave, gaseous ozone, and radiofrequency glow discharging.^4,5 In recent years, ultraviolet (UV) radiation has become an effective way of disinfecting impressions as they are effective in destroying the microorganisms and the bacterial spores while preserving the quality of the material.⁶

The SARS-CoV-2 virus that has caused outbreaks globally has not yet been specifically evaluated for its vulnerability to ultraviolet irradiation. However, several studies on related coronaviruses, as well as the SARS coronavirus, have shown that they are greatly susceptible to ultraviolet radiation inactivation.⁷ An accurate impression of the dental tissues is a major requirement for the precise adaptation of the dental prosthesis. Polyvinylsiloxane elastomeric impression materials have excellent physical and mechanical properties and hence are the materials of choice for all impression procedures in dentistry.⁵

An impression with irregularities or surface defects may result in an ill-fitting prosthesis. In order to prevent plaque and calculus buildup and also improve esthetics, a smooth intaglio surface is desirable. Any irregularities on the intaglio surface of the prosthesis might influence its fit. Such irregularities may result from alterations in the material’s properties following disinfection procedures.^8,9

The rationale of this study was to assess the outcome of chemical disinfection and ultraviolet irradiation on the surface roughness of two different polyvinylsiloxane elastomeric impression materials. The null hypothesis was that ultraviolet irradiation and chemical disinfection do not have any effect on the surface roughness of polyvinylsiloxane elastomeric impression materials.

MATERIALS AND METHODS

RESULTS

One-way ANOVA was carried out to compare the mean surface roughness among the different subgroups in group I (Elite HD+) and group II (Aquasil), respectively (Table 1 ). The surface roughness was found to be the highest in group Ic (0.540) and the lowest in group IIa (0.26745). The Tukey HSD test revealed that the difference in the surface roughness values was statistically significant at 0.00 level (p < 0.05) (Table 2 ). In general, the control groups (group Ia and group IIa) presented the lowest surface roughness values and the chemical group (group Ic and group IIc) presented the highest surface roughness values.

DISCUSSION

This null hypothesis was rejected as there was a statistically significant difference in the surface roughness of the polyvinylsiloxane elastomers when subjected to chemical disinfection and ultraviolet irradiation. Generally, dental impressions are disinfected by immersing them in an appropriate disinfectant solution or by spraying. Spraying leads to pooling of the disinfectant solution and hence not effective in disinfection. Hence, the immersion method was used in this study. Previous studies have demonstrated that polyvinylsiloxane impressions can be effectively disinfected on immersion with 2% glutaraldehyde for 10 minutes. Glutaraldehyde acts by fixation of the cell membrane and blocking the release of cellular components, thus killing the microorganisms.³

Ultraviolet irradiation has shown to be an effective method of inactivating the microorganisms while preserving the quality of material. Ultraviolet light results in the formation of thymine-containing photoproducts in the DNA of affected cells. Studies have shown that the UV chamber can be safely used for the disinfection of the polyvinylsiloxane impression material without affecting its dimensional stability.^10,11 The disinfection procedure can result in change in the properties of the material leading to changes in the surface roughness. Several studies have evaluated the surface roughness of gypsum casts^8,9,12 obtained from elastomeric impressions. Studies on the measurement of surface roughness directly on the impressions are inadequate.

A significant difference in the surface roughness was observed within the control group for the two materials. The Elite HD+ specimens showed higher surface roughness values compared to the Aquasil specimens, which may be due to differences in the chemical composition in addition to the size, shape, and amount of the filler particles. Both the chemically disinfected and ultraviolet irradiated groups showed increased surface roughness values; however, greater increase was found for the chemically disinfected groups.

Since studies on the evaluation of surface roughness of polyvinylsiloxane impressions are limited, direct comparisons with the results obtained in this study cannot be made. Since chemical disinfection has limited success, ultraviolet radiation may be considered as an alternative to sterilize elastomeric impressions. However, before arriving at definite conclusion regarding the surface roughness, further research involving greater sample sizes is necessary.

CONCLUSION

Ultraviolet irradiation sterilization of polyvinylsiloxane elastomeric impressions could be considered an effective method compared to chemical disinfection since chemical disinfection results in a rougher impression surface. Among the two materials, Aquasil showed lower surface roughness compared to Elite HD+.

REFERENCES

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