Available online 30 November 2022

Author links open overlay panelAbstractStatement of problem

Stone casts are subject to contamination, but whether disinfectants incorporated into the stone are effective is unclear.

Purpose

The purpose of this in vitro study was to evaluate the antimicrobial activity and the mechanical and surface properties of self-disinfecting gypsum (SDG) and gypsum mixed with 2% chlorhexidine (GCHX).

Material and methods

Antimicrobial action was evaluated using the diffusion-disk technique on Streptococcus aureus and Candida albicans 1 hour and 24 hours after pouring the gypsum. The groups were SDG, GCHX, a positive control (PC) of gypsum mixed with distilled water, and a negative control (NC) of filter paper disk soaked with 2% chlorhexidine; n=8. Inhibition halos were measured using the ImageJ software program and statistically analyzed using the repeated measures mixed ANOVA with time×group interaction. Compressive strength (CS) in MPa and surface roughness (SR) in μm (parameters: Ra - roughness average; and Sa - 3-dimensional (3D) arithmetic mean of the surface profile) tests were performed to characterize the specimens (evaluated groups: SDG, GCHX, and PC; n=10). CS data were analyzed by a 2-way ANOVA with time×group interaction, and SR data by a 1-way ANOVA (α=.05).

Results

For S aureus, there were differences between GCHX and SDG at 1 hour and 24 hours (P<.05), but no significant differences were found for C albicans (P>.05). GCHX was better than PC, except for C albicans, and showed a reduction in CS when compared with PC and SDG (P<.05) at all time intervals. The SR of GCHX increased (Ra:1.76, Sa:2.08) when compared with PC (Ra:0.89, Sa:1.12) and SDG (Ra:1.03, Sa:1.35) (Ra: P<.004 and Sa: P<.001).

Conclusions

The antimicrobial activity of GCHX against S aureus was better than that of SDG, but neither had an effect against C albicans. As for CS and SR, GCHX presented a decrease in properties when compared with PC and SDG but was within the American Dental Association #25 specification values.

Section snippetsMaterial and methods

The materials used in the study are described in Table 1. Addition silicone molds (Elite HD +; Zhermack) were used to make Ø10×2-mm disk-shaped specimens. The dental stones were previously weighed (40 g per group) on a precision digital scale (AG 200; GEHAKA) under aseptic conditions. Subsequently, they were mixed with mechanical vacuum mixing (Protécni) for 30 seconds according to the powder-to-liquid ratio recommended by the manufacturer and poured under vibration into the sterile molds.

The

Results

Figure 1 represents the agar diffusion test for visualization of the inhibition halos obtained for S aureus at 1 hour and 24 hours and C albicans at 1 hour and 24 hours. Tables 3 and 4 present the mean values of the inhibition halos for S aureus and C albicans, respectively. The results indicated that, for S aureus there were no significant differences between 1 hour and 24 hours in any of the groups (P>.05). The time×group interaction was not significant (P=.440), indicating that the evolution

Discussion

Stone casts are used routinely in dental practice for the fabrication of indirect restorations, prostheses, and orthodontic appliances. The presence of pathogens in impressions and stone casts, potentially persistent in the short and long term, can lead to transmission and cross-contamination,9,13,20,40,43 with a higher level of contamination.17,25 in the first 24 hours, a period of time in which stone casts are more likely to be manipulated.13 Strains of S aureus have been reported to remain

Conclusions

Based on the findings of this in vitro study, the following conclusions were drawn:

1.

The antimicrobial action of GCHX was better than that of SDG against S aureus; however, neither had an effect against C albicans.

2.

A reduction in the compressive strength and an increase in the surface roughness of the GCHX were found when compared with the other groups but were within the ADA #25 specifications.

3.

The SDG when compared with PC showed similar surface roughness (Ra and Sa) and reduced compressive

CRediT authorship contribution statement

Panmella Pereira Maciel: contributed to conception, design, data acquisition and interpretation, drafted and critically revised the manuscript. Cíntia de Lima Gouveia: contributed to data acquisition and interpretation, drafted and critically revised the manuscript. Iasmin Lima Marques: contributed to data acquisition and interpretation and critically revised the manuscript. Patrícia Pereira Maciel: contributed to data acquisition and interpretation and critically revised the manuscript.

Acknowledgments

The authors thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPQ (Inct Teranostica) for their support.

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© 2022 by the Editorial Council for The Journal of Prosthetic Dentistry.