Introduction
Taking impressions is a basic, important step for dental prosthesis and orthodontic treatment ( Punj, Bompolaki & Garaicoa, 2017 ). Alginate impression material is a type of irreversible elastic impression material with good fluidity, elasticity, plasticity, and dimensional accuracy. It has become the most widely-used impression material because of its low price and ease of use ( Cervino et al., 2018 ). During impression making, dental impression materials invariably come in contact with the patient’s saliva and blood, which can contain potentially pathogenic microorganisms such as Streptococcus , Staphylococcus , Escherichia coli , Mycobacterium tuberculosis , in addition to hepatitis B and C viruses, human immunodeficiency virus (HIV), and herpes simplex virus ( Chidambaranathan & Balasubramanium, 2019 ; Flanagan et al., 1998 ). Until 1991, the recommended disinfection method was simply rinsing the dental impressions under running tap water ( Oosthuysen, Potgieter & Fossey, 2014 ). However, this method only eliminates about 40% of microorganisms, leaving a significant risk of infection ( McNeill, Coulter & Hussey, 1992 ). Proper disinfection protocols are necessary to prevent cross-infection between clinicians, patients, and laboratory personnel ( Ganavadiya et al., 2014 ). Recognizing this, the American Dental Association (ADA) and the Centers for Disease Control (CDC) now recommend immediate disinfection of impression materials after removal from the mouth to mitigate the spread of infectious diseases ( Aeran et al., 2015 ).

Currently, there is no universally accepted “gold standard” method for disinfecting dental impressions ( Cervino et al., 2018 ). Due to the nature of alginate, sterilization by heat is not feasible, leaving cold chemical disinfection as the only available option. Immersing or spraying impressions with chemical disinfectants is commonly practiced in clinical settings, and studies have demonstrated that disinfectants can effectively reduce the microbial count on alginate impressions ( Al-Enazi & Naik, 2016 ). However, immersion disinfection may result in dimensional changes ( Guiraldo et al., 2012 ; Iwasaki et al., 2016 ) and affect the accuracy ( Ud Din et al., 2022 ) of the dental cast prosthesis due to alginate imbibition and synergistic effects. To address this issue, spray disinfection using chemical disinfectants has gained popularity for disinfecting alginate impression materials. Commonly used chemical disinfectants include chlorhexidine, alcohol, glutaraldehyde, and sodium hypochlorite ( Lagla Abata et al., 2024 ; Qiu et al., 2023 ). However, the aerosols generated during the spray disinfection process can release harmful substances into the air, potentially causing irritation and occupational exposure ( Slaughter et al., 2019 ). Long-term use of bleach has been linked to non-allergic adult-onset asthma symptoms in some individuals ( Matulonga et al., 2016 ). Extensive or prolonged exposure to chemical disinfectants can cause skin irritation, hypersensitivity, and damage ( Chia Shi Zhe et al., 2016 ). Moreover, the by-products of chemical disinfection are harmful to the environment ( Li et al., 2023 ), and these disinfectants can corrode metal trays ( Nagamatsu et al., 2016 ). Therefore, a disinfectant is needed that can effectively eliminate microorganisms on dental impressions without compromising their physical properties and dimensional accuracy while also ensuring occupational safety.

In recent years, there has been a growing focus on the identification and development of new medicines derived from natural products. Many studies have reported that a significant number of drugs in the development stage are extracted from natural sources, with approximately 80% originating from plants ( Coy-Barrera, Ogungbe & Schmidt, 2023 ; Liang, Luo & Luesch, 2019 ). This search for natural medicines not only promotes human health but also supports economic development and habitat conservation.

This study explores the use of pure, natural extract compounds as a disinfectant for alginate impression material ( Wu et al., 2014 ), based on previous research efforts. This study specifically investigates chlorogenic acid (CA), a phenolic compound belonging to the hydroxycinnamic acid family ( Naveed et al., 2018 ). CA is commonly found in various foods and medicines, including traditional Chinese herbal medicines, like “honeysuckle” ( Santana-Gálvez, Cisneros-Zevallos & Jacobo-Velázquez, 2017 ). CA possesses a broad range of biological activities, such as antioxidant, anti-inflammatory, and blood pressure-lowering effects ( Gupta et al., 2022 ; Tajik et al., 2017 ), making it a safe naturally-derived compound. Recent studies have demonstrated that CA has potential as an effective antimicrobial agent by directly targeting bacterial cell wall and cell membranes to cause irreversible osmotic damage ( Liu et al., 2019 ; Lou et al., 2011 ; Lu et al., 2020 ). It has shown promising results as an anti-inflammatory agent in different chronic and acute inflammatory conditions, such as mastitis ( Feng et al., 2023 ) and osteoarthritis ( Liu et al., 2017 ). CA plays a therapeutic role in periodontal inflammatory diseases by influencing proteasome activity and the growth of Porphyromonas gingivalis ( Tsou et al., 2019 ). CA has also been used for disinfection purposes in polydimethylsiloxane microfluidic devices ( Ren et al., 2015 ), showing superior antimicrobial effects against both gram-positive and gram-negative bacteria compared to gentamicin. A recent study on the dental unit waterlines demonstrated CA’s significant inhibitory effect on opportunistic pathogens such as Mycobacterium ( Li et al., 2024 ). Another previous study demonstrated CA’s antioxidant and anti-diabetes benefits in humans, and found that CA would not harm the human body ( Faria et al., 2020 ).

Alginate impression material is a special functional material that replicates the complex oral environment. Alginate impression material disinfectants must have good antimicrobial efficacy without affecting the physical properties of the impression material or the accuracy of the gypsum model. If the disinfectant changes the physical properties of the material, affecting the accuracy of the final restoration system, then the disinfectant’s antimicrobial properties are meaningless. Therefore, any study of disinfectants for impression materials must assess the physical properties of impression materials and the accuracy of the plaster model after use. In this study, four physical properties—elastic recovery, compressive strain, initial setting time, and fluidity—were selected for assessment, according to the ISO 21563 standard ( Standardization, 2021 ) and the American National Standards Institute (ANSI)/ADA specification No. 18 for irreversible hydrocolloid impression material ( Dental Materials, 1992 ). Gram-positive bacteria, gram-negative bacteria, and fungi were used to evaluate the antimicrobial effect of CA on different microorganisms. CA has not been used for the disinfection of any hydrocolloid impression material in dentistry prior to this study. This study provides valuable insights on CA as a safe and effective alginate impression disinfectant, and as a traditional Chinese medicine impression disinfectant.