Evaluation of two different self-disinfection alginate impression material

Accurate dental impressions are crucial for successful dental treatments. Alginate, a common and affordable impression material, is susceptible to contamination and requires disinfection, which can cause dimensional changes. This study aimed to address this by incorporating antimicrobial agents, povidone-iodine (PV-I) and silver nanoparticles (AgNPs), directly into the alginate to create self-disinfecting materials. The null hypothesis was that adding PV-I and AgNPs would negatively affect the mechanical properties and accuracy of the alginate impressions. The widespread use of conventional alginate necessitates effective disinfection protocols to prevent cross-contamination. Existing methods, such as spraying or immersion, often lead to dimensional instability and compromise the accuracy of the final casts. Self-disinfecting alginate offers a potential solution to this problem by eliminating the need for post-impression disinfection. This approach could improve workflow efficiency while maintaining the accuracy and reliability of dental impressions. The selection of PV-I and AgNPs was based on their established antimicrobial properties and potential compatibility with alginate. PV-I, a well-known broad-spectrum antimicrobial agent, has been used extensively in various clinical settings. AgNPs, known for their antimicrobial and antiviral effects, are gaining popularity in biomedical applications due to their effectiveness at low concentrations. This research aimed to compare the efficacy of these two agents in a self-disinfecting alginate formulation and assess their impact on the material's mechanical properties.

Previous research highlights the importance of accurate dental impressions and the challenges associated with conventional disinfection methods for alginate impressions. Studies have demonstrated that disinfection techniques, such as immersion in disinfectant solutions or spraying, can cause dimensional changes and affect the accuracy of the final gypsum models. Several studies have explored the use of self-disinfecting impression materials to address these limitations. These studies have focused on incorporating various antimicrobial agents into the alginate matrix, aiming to reduce or eliminate the need for post-impression disinfection. The effectiveness and potential effects on the mechanical properties of the alginate have been variable across studies, depending on the concentration and type of antimicrobial agent used. The existing literature provides a foundation for investigating the use of PV-I and AgNPs as potential self-disinfecting agents in alginate impression materials. Studies have demonstrated the broad-spectrum antimicrobial activity of both PV-I and AgNPs against various microorganisms, including bacteria and fungi. However, further research is needed to evaluate their efficacy in a self-disinfecting alginate formulation and to assess their potential impact on the mechanical properties of the material.

The study employed three groups of alginate: a control group (additive-free), a povidone-iodine (PV-I)-containing group, and a silver nanoparticle (AgNP)-containing group. AgNPs were synthesized via chemical reduction of silver nitrate with glucose in the presence of polyvinylpyrrolidone (PVP). The synthesized AgNPs were characterized using UV-Vis spectroscopy and transmission electron microscopy (TEM) to determine their size and distribution. For the alginate preparations, 0.45 g of alginate powder was mixed with 1 mL of either water (control), 10% PV-I, or 0.05% AgNP suspension. Discs (5 mm diameter) were cut from each preparation and tested for antimicrobial activity using the disc diffusion method against *Staphylococcus aureus*, *Escherichia coli*, and *Candida albicans*. Surface detail reproduction was assessed according to ISO 1563:1990 using a copper mold with engraved lines of varying depths (50, 20, and 75 µm). Six samples from each group were evaluated based on their ability to reproduce the 50 µm line. Elastic recovery was also evaluated according to ISO 1563:1990 using a segmented cylindrical mold. A material testing machine measured the recovery of samples after 20% deformation. Data were statistically analyzed using SPSS software (version 20.0), applying a significance level of p ≤ 0.05. The Shapiro-Wilk test assessed data distribution, with Duncan's multiple range and Tukey post-hoc tests used for group comparisons when ANOVA results were significant. The study followed ethical guidelines, receiving approval from the Research Ethics Committee at the Faculty of Pharmacy, Delta University for Science and Technology.

The antimicrobial testing demonstrated that both AgNP-alginate and PV-I-alginate exhibited broad-spectrum antimicrobial activity against *S. aureus*, *E. coli*, and *C. albicans*, significantly surpassing the control group (p ≤ 0.05). Specifically, both experimental alginates showed significantly greater activity against *S. aureus* (Gram-positive) compared to *E. coli* (Gram-negative). PV-I-alginate exhibited significantly greater activity against *C. albicans* than AgNP-alginate. The surface detail reproduction test showed that all samples, irrespective of the added antimicrobial agent, successfully reproduced the 50 µm line, meeting the ISO 1563 specification. The elastic recovery test revealed no statistically significant differences (p > 0.05) in mean elastic recovery values among the control, PV-I-alginate, and AgNP-alginate groups. The values were close to the minimum 95% recovery specified by ANSI/ADA specification no. 18-1992. The pH of the PV-I alginate mixture was measured as 6.8, indicating that the alginate effectively buffered the acidic pH of the PV-I.

The findings reject the null hypothesis, indicating that the incorporation of PV-I and AgNPs into alginate does not significantly impair its mechanical properties. Both antimicrobial agents effectively sanitized the alginate without compromising its ability to reproduce fine details or its elastic recovery. The superior activity against Gram-positive bacteria aligns with previous research. The slightly lower elastic recovery of PV-I alginate compared to the control, although not statistically significant, may be due to reduced water availability caused by the water-soluble PV-I. The observed antimicrobial activity is attributed to the mechanism of action of each agent: AgNPs release Ag+ ions, which interact with negatively charged microbial cell membranes, and PV-I inactivates bacterial cellular mechanisms. The study successfully demonstrated the feasibility of self-disinfecting alginate, offering a potential solution for improving infection control protocols in dentistry.

This study successfully demonstrated that both povidone-iodine and silver nanoparticles can be incorporated into alginate impression material to create a self-disinfecting product without compromising its accuracy or elastic recovery. While both agents proved effective, PV-I's lower cost and greater accessibility may make it a more practical choice for widespread use. Future research could explore optimizing the concentration of these agents to maximize antimicrobial efficacy while further minimizing any potential impact on material properties. Investigating long-term stability and shelf life of the self-disinfecting alginate would also be valuable.

The study's scope was limited to in vitro testing. Further in vivo studies are necessary to confirm the clinical efficacy and safety of these self-disinfecting alginate formulations. The study examined a limited range of microorganisms; additional testing with a broader spectrum of oral pathogens would strengthen the findings. The study focused on specific concentrations of PV-I and AgNPs; further investigation into a wider range of concentrations could reveal optimal formulations.