Many studies have shown that slightly acidic hypochlorous acid water (SAHW) has a good disinfection effect. For example, the study by Zhang Xueli et al. showed that the killing rate of 200 mg/L SAHW on Staphylococcus aureus and Escherichia coli on alginate impression materials reached 99.9% within 10 minutes, and the killing rate of the two species on silicone rubber impression materials also reached 99.9% . In addition, non-electrolytic slightly acidic hypochlorous acid water spray disinfection also showed a good bactericidal effect, with killing rates of 4.09 and 5.26 for Candida albicans and Streptococcus mutans, respectively.
Regarding the effect of slightly acidic hypochlorous acid water on impression accuracy, there are some differences in research results:
Alginate impression material : The study by Zhang Xueli et al. showed that the root mean square error (RMS) value of alginate impression material increased after immersion disinfection in 200 mg/L SAHW, indicating that its dimensional stability may be affected. In addition, other studies have also pointed out that alginate impression materials are sensitive to environmental humidity and prolonged immersion may cause dimensional changes.
Silicone rubber impression material : Silicone rubber impression material is less sensitive to disinfectants, and studies have shown that it has better dimensional stability. For example, after immersion disinfection with 200 mg/L SAHW, the RMS value of silicone rubber impression materials changed little, and no significant dimensional changes were observed. The silicone rubber impression material showed less dimensional change, indicating that it has a protective effect on the dimensional stability of the material during the sterilization process.
Compared with sodium hypochlorite (NaClO): Although sodium hypochlorite has a significant disinfection effect, it may have an adverse effect on the dimensional stability of the impression material. For example, alginate impression materials may show linear dimensional changes after disinfection by immersion in sodium hypochlorite. In contrast, the disinfection effect of slightly acidic hypochlorous acid water is comparable to that of sodium hypochlorite, but has less impact on impression accuracy.
Compared with glutaraldehyde: Although glutaraldehyde has a good disinfection effect, it has a greater impact on the dimensional stability of the impression material and may cause deformation of the impression material. Slightly acidic hypochlorous acid water achieves a better balance between disinfection effect and dimensional stability.
Comprehensive analysis showed that slightly acidic hypochlorous acid water (SAHW) showed good bactericidal effect in oral impression disinfection and had little effect on the dimensional stability of alginate and silicone rubber impression materials. However, for alginate impression materials, controlled soaking time is recommended to avoid the potential risk of dimensional changes.
Therefore, immersion disinfection in slightly acidic hypochlorous acid water is an effective method for oral impression disinfection, especially suitable for clinical scenarios with high requirements for impression accuracy.
Comparison with other disinfectants
The study showed that different disinfectants had different effects on the dimensional stability of silicone rubber and polyether impression materials. For example, after soaking in peracetic acid, the dimensional details and accuracy of silicone rubber and polyether impression materials were well maintained, while the specific effects of slightly acidic hypochlorous acid water were not mentioned in detail in the study. However, from the overall trend, slightly acidic hypochlorous acid water, as a mild disinfectant, may be superior to strong oxidants such as peracetic acid to a certain extent.
Impact of disinfection methods
Studies have shown that when slightly acidic hypochlorous acid water is used to disinfect oral impressions by spraying, it can effectively kill microorganisms and has little effect on the dimensional stability of the impression materials. This further supports the protective effect of slightly acidic hypochlorous acid water on the dimensional stability of materials during the disinfection process.
The influence of impression accuracy
Slightly acidic hypochlorous acid water: The study found that the RMS error value of slightly acidic hypochlorous acid water for alginate impression materials increased with the extension of immersion time, but the RMS error value of silicone rubber impression materials did not change much. This shows that slightly acidic hypochlorous acid water has different effects on the accuracy of different impression materials.
Glutaraldehyde: Glutaraldehyde caused the smallest dimensional change in VPES elastic impression material, and its dimensional change was within an acceptable range at 10 and 30 minutes of immersion time, indicating that glutaraldehyde has an advantage in maintaining impression accuracy.
Sodium hypochlorite: Sodium hypochlorite has little effect on the dimensional changes of silicone rubber impression materials, but it has a greater effect on the dimensional changes of alginate impression materials.
BLUEWAV recommends that when using SAHW for disinfection, the water temperature should be kept at 20-22°C to avoid dimensional changes caused by excessive temperature. Since slightly acidic hypochlorous acid water has good antibacterial effect and is easy to operate, it can still be used as the preferred disinfection method. But you need to be careful to control the soaking time and avoid exceeding 30 minutes.
Based on the above research results, the following are specific operational suggestions given by BLUEWAV :
Soaking time: The soaking time of alginate impression material in slightly acidic hypochlorous acid water (SAHW) should be controlled within 30 minutes to avoid a significant increase in dimensional deviation.
Water temperature control: Ensure that the water temperature of SAHW is maintained at 20-22℃ to avoid shortened solidification time and dimensional changes caused by excessive temperature.
slightly acidic hypochlorous acid water with an effective chlorine mass concentration of 200 mg/L for disinfection, and avoid using disinfectants with too high concentrations.
Subsequent processing: The alginate impression material should be immediately cast into plaster after disinfection to reduce dimensional deviation caused by changes in environmental humidity.
When the effective chlorine mass concentration of slightly acidic hypochlorous acid water is 200 mg/L, the disinfection effect on alginate impressions is better .
It is mentioned that sodium hypochlorite solution with an effective chlorine concentration of 500 mg/L can also be effectively disinfected, but it is not clearly stated whether it is suitable for oral impressions.
Best soaking time:
According to the results, the disinfection effect of slightly acidic hypochlorous acid water on alginate impressions varies at different immersion times. Specifically:
When immersed for 10 min, the RMS value of the alginate impression decreased significantly, indicating a better disinfection effect.
When immersed for 20 min, the RMS value of the alginate impression decreased further, but the difference was not significant compared with that at 10 min.
After immersion for 30 min, the RMS value of the alginate impression did not change much, indicating that the disinfection effect tended to be stable.
Therefore, a 10-minute immersion time may be the best choice, which can effectively disinfect and reduce the impact on impression accuracy.
in conclusion:
The optimal concentration of slightly acidic hypochlorous acid water for oral impression disinfection is 200 mg/L, and the optimal immersion time is 10 minutes.
♯ Long-term effects of slightly acidic hypochlorous acid water on oral impression materials
Slightly acidic hypochlorous acid water shows good safety and effectiveness in the disinfection of oral impression materials. For alginate impression materials, although long disinfection time may affect the accuracy, proper control of disinfection time can reduce this effect. For other materials such as silicone rubber and resin, slightly acidic hypochlorous acid water has an ideal disinfection effect and will not have a significant negative impact on their performance.
Slightly acidic hypochlorous acid water has certain advantages in the long-term use of oral impression materials, especially in reducing the negative impact on material properties.
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