Efficacy of the dual-action GA-KR12 peptide for remineralising initial enamel caries: an in vitro study

Remineralising enamel caries with a novel peptide: An in vitro study

OBJECTIVE

To evaluate the antibacterial and remineralising effects of GAPI peptide on artificial enamel caries.

METHODS

Human enamel blocks were exposed to Streptococcus mutans biofilm to create artificial carious lesions. The blocks were randomly assigned to either the GAPI treatment group or the deionised water control group, treated twice daily for 21 days. The viability, growth kinetics, and morphology of S. mutans biofilms were assessed using confocal laser scanning microscopy (CLSM), colony-forming unit (CFU) counting, and scanning electron microscopy (SEM). Lesion depth, mineral loss, calcium-to-phosphorus ratio, Knoop hardness, enamel surface morphology, and crystal characteristics of enamel lesions were determined using micro-computed tomography (Micro-CT), SEM-energy dispersive spectroscopy (EDS), a microhardness tester, SEM, and X-ray diffraction (XRD).

RESULTS

CLSM showed that the dead-to-live ratio of S. mutans was 0.8 ± 0.1 in the GAPI group and 0.4 ± 0.1 in the control group (p < 0.001). The Log CFUs were 6.9 ± 0.7 in the GAPI group and 8.1 ± 0.5 in the control group (p = 0.002). SEM revealed confluent growth of S. mutans in the control group but not in the GAPI group, which also exhibited cell damage. Micro-CT showed that the lesion depth (µm) was 142 ± 11 in the GAPI group and 178 ± 20 in the control group (p < 0.001), with mineral loss (gcm⁻³) of 1.1 ± 0.1 and 1.5 ± 0.1, respectively (p < 0.001). SEM-EDS indicated that the calcium-to-phosphorus ratio was 1.71 ± 0.02 in the GAPI group and 1.67 ± 0.03 in the control group (p = 0.006). Additionally, Knoop hardness was 302 ± 22 in the GAPI group and 242 ± 17 in the control group (p < 0.001). SEM revealed an orderly pattern of enamel rods in the GAPI group, and XRD showed better crystallisation of hydroxyapatite in the GAPI group compared to the control group.

CONCLUSION

GAPI exhibits antibacterial and remineralising properties against artificial enamel caries.

CLINICAL SIGNIFICANCE

If the anti-caries properties of GAPI are confirmed in clinical studies, it could be used for caries prevention.

Antibacterial and mineralising properties of copper tetraamine fluoride on dentine caries: A laboratory study

OBJECTIVE

To investigate the antibacterial, mineralising, and discolouring properties of copper tetraamine fluoride (CTF) on artificial dentine caries.

METHOD

Demineralised human dentine blocks were treated with CTF, silver diamine fluoride (SDF, positive control) and water (negative control) before they were subjected to cariogenic challenge with Streptococcus mutans biofilm. The morphology, viability, and growth kinetics of the biofilm were assessed by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and colony-forming unit (CFU) counting. The lesion depths, mineral loss, chemical structure, and crystal characteristics were measured using micro-computed tomography, Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The discolouring property on demineralised dentine was assessed by spectrophotometry. One-way analysis of variance with the Bonferroni post hoc test was performed to assess and compare the data.

RESULTS

SEM revealed confluent bacterial growth covering the surface of dentine treated with Water but not CTF and SDF. CLSM showed the dead-to-live ratio of the biofilm treated with CTF, SDF and Water were 0.7 ± 0.1, 0.8 ± 0.1 and 0.5 ± 0.1 (p < 0.001, CTF, SDF>Water). The Log10 CFU values of the biofilm treated with CTF, SDF and Water were 7.8 ± 0.1, 7.8 ± 0.1 and 8.1 ± 0.2 (p < 0.001, CTF, SDF

CONCLUSION

CTF inhibited Streptococcus mutans. It mineralised but not discoloured artificial dentine caries.

CLINICAL SIGNIFICANCE

If CTF is successfully translated into clinical application, it may be a non-discolouring anti-caries agent for clinicians to arrest dentine caries.

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Key Words

• Antibacterial
• Caries
• Dentine
• Fluoride
• Remineralization

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MESH Headings

• Dentin/drug effects
• Humans
• Biofilms/drug effects
• Dental Caries/microbiology
• Anti-Bacterial Agents/pharmacology
• Streptococcus mutans/drug effects
• X-Ray Microtomography
• Spectroscopy, Fourier Transform Infrared
• Microscopy, Electron, Scanning
• Quaternary Ammonium Compounds/pharmacology
• Quaternary Ammonium Compounds/chemistry
• X-Ray Diffraction
• Silver Compounds/pharmacology
• Microscopy, Confocal
• Cariostatic Agents/pharmacology
• Cariostatic Agents/therapeutic use
• Cariostatic Agents/chemistry
• Fluorides, Topical/pharmacology

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Affiliation(s)

Veena Wenqing Xu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Iris Xiaoxue Yin Faculty of Dentistry, University of Hong Kong, Hong Kong, China
John Yun Niu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Ollie Yiru Yu Faculty of Dentistry, University of Hong Kong, Hong Kong, China
Mohammed Zahedul Islam Nizami Faculty of Dentistry, University of Hong Kong, Hong Kong, China; Department of Mineralized Tissue Biology and Bioengineering, The ADA Forsyth Institute, Cambridge, MA, USA.
Chun Hung Chu Faculty of Dentistry, University of Hong Kong, Hong Kong, China.

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In Vitro Models Used in Cariology Mineralisation Research-A Review of the Literature

BACKGROUND

Dental caries remains a significant global health problem. One of the fundamental mechanisms underlying the development and progression of dental caries is the dynamic process of demineralisation/remineralisation. In vitro models have played a critical role in advancing our understanding of this process and identifying potential interventions to prevent or arrest dental caries. This literature review aims to provide a structured oversight of in vitro mineralisation models which have been used to study the tooth demineralisation/remineralisation process.

METHODS

Publications from 2019 to 2023 were screened to identify articles reporting the use of in vitro models to study the demineralisation/remineralisation of tooth caries. The included studies were methodologically assessed for their information on (i) substrate, (ii) lesion formation, and (iii) mineralisation models.

RESULTS

The most reported substrates used in the studies were human teeth along with bovine incisors. Acetic/lactic buffers were the most common solutions to induce caries lesions. pH cycling was the most frequently used mineralisation model for simulating the daily change within the oral environment. This review discussed the advantages and limitations of various approaches.

CONCLUSIONS

Standardisation of in vitro mineralisation models is crucial for enabling effective comparison between studies and advancing caries research.

Changes in enamel hardness, wear resistance, surface texture, and surface crystal structure with glass ionomer cement containing BioUnion fillers

This study investigated the potential of BioUnion filler containing glass ionomer cement (GIC) to enhance the properties of enamel surrounding restorations, with a specific focus on the effect on hardness. The hardness of the bovine enamel immersed in the cement was measured using Vickers hardness numbers. Following sliding and impact wear simulations, the enamel facets were examined using confocal-laser-scanning microscopy and scanning-electron microscopy. Surface properties were further analyzed using energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). A significant increase in Vickers hardness numbers was observed in the BioUnion filler GIC after 2 days. Furthermore, the mean depth of enamel facets treated with BioUnion filler GIC was significantly less than that of untreated facets. Characteristic XRD peaks indicating the presence of hydroxyapatite were also observed. Our findings imply that GIC with BioUnion fillers enhances the mechanical properties of the tooth surface adjacent to the cement.

Antimicrobial Peptides Targeting Streptococcus mutans: Current Research on Design, Screening and Efficacy

Antimicrobial peptides (AMPs) are small-molecule peptides that play a vital role in the nonspecific immune defense system of organisms. They mainly kill microorganisms by physically destroying the cell membrane and causing the leakage of contents. AMPs have attracted much attention as potential alternatives to antibiotics due to their low susceptibility to resistance. Streptococcus mutans (S. mutans) is one of the main causative agents of human dental caries. The design, screening, and efficacy evaluation of AMPs targeting S. mutans offer new possibilities for the prevention and treatment of oral diseases, especially dental caries, in the future. This article reviews AMPs from different sources that have inhibitory effects on S. mutans, discusses the mechanism of action of AMPs against S. mutans biofilms, and focuses on the research progress of screening methods, design modification, and biological activity evaluation of AMPs. We hope to provide insights and reference value for the development of new biologics.

The Anti-Caries Effects of a Novel Peptide on Dentine Caries: An In Vitro Study

This study aimed to investigate the antibiofilm and remineralising effects of peptide GAPI on artificial dentin caries. After creating artificial carious lesions, eighty dentine blocks were randomly assigned for treatment twice daily with GAPI (GAPI group) or deionised water (control group). Both groups underwent a 7-day biochemical cycle. Scanning electron microscopy (SEM) showed S. mutans with damaged structures that partially covered the dentine in the GAPI group. The dead-live ratios for the GAPI and control groups were 0.77 ± 0.13 and 0.37 ± 0.09 (p < 0.001). The log colony-forming units for the GAPI and control groups were 7.45 ± 0.32 and 8.74 ± 0.50 (p < 0.001), respectively. The lesion depths for the GAPI and control groups were 151 ± 18 µm and 214 ± 15 µm (p < 0.001), respectively. The mineral losses for the GAPI and control groups were 0.91 ± 0.07 gHAcm-3 and 1.01 ± 0.07 gHAcm-3 (p = 0.01), respectively. The hydrogen-to-amide I ratios for the GAPI and control groups were 2.92 ± 0.82 and 1.83 ± 0.73 (p = 0.014), respectively. SEM micrographs revealed fewer exposed dentine collagen fibres in the GAPI group compared to those in the control group. Furthermore, X-ray diffraction (XRD) patterns indicated that the hydroxyapatite in the GAPI group was more crystallised than that in the control group. This study demonstrated GAPI's antibiofilm and remineralising effects on artificial dentin caries.

Antibacterial Properties of the Antimicrobial Peptide Gallic Acid-Polyphemusin I (GAPI)

A novel antimicrobial peptide, GAPI, has been developed recently by grafting gallic acid (GA) to polyphemusin I (PI). The objective of this study was to investigate the antibacterial effects of GAPI on common oral pathogens. This laboratory study used minimum inhibitory concentrations and minimum bactericidal concentrations to assess the antimicrobial properties of GAPI against common oral pathogens. Transmission electron microscopy was used to examine the bacterial morphology both before and after GAPI treatment. The results showed that the minimum inhibitory concentration ranged from 20 μM (Lactobacillus rhamnosus) to 320 μM (Porphyromonas gingivalis), whereas the minimum bactericidal concentration ranged from 80 μM (Lactobacillus acidophilus) to 640 μM (Actinomyces naeslundii, Enterococcus faecalis, and Porphyromonas gingivalis). Transmission electron microscopy showed abnormal curvature of cell membranes, irregular cell shapes, leakage of cytoplasmic content, and disruption of cytoplasmic membranes and cell walls. In conclusion, the GAPI antimicrobial peptide is antibacterial to common oral pathogens, with the potential to be used to manage oral infections.

Bioactive Materials for Caries Management: A Literature Review

Researchers have developed novel bioactive materials for caries management. Many clinicians also favour these materials, which fit their contemporary practice philosophy of using the medical model of caries management and minimally invasive dentistry. Although there is no consensus on the definition of bioactive materials, bioactive materials in cariology are generally considered to be those that can form hydroxyapatite crystals on the tooth surface. Common bioactive materials include fluoride-based materials, calcium- and phosphate-based materials, graphene-based materials, metal and metal-oxide nanomaterials and peptide-based materials. Silver diamine fluoride (SDF) is a fluoride-based material containing silver; silver is antibacterial and fluoride promotes remineralisation. Casein phosphopeptide-amorphous calcium phosphate is a calcium- and phosphate-based material that can be added to toothpaste and chewing gum for caries prevention. Researchers use graphene-based materials and metal or metal-oxide nanomaterials as anticaries agents. Graphene-based materials, such as graphene oxide-silver, have antibacterial and mineralising properties. Metal and metal-oxide nanomaterials, such as silver and copper oxide, are antimicrobial. Incorporating mineralising materials could introduce remineralising properties to metallic nanoparticles. Researchers have also developed antimicrobial peptides with mineralising properties for caries prevention. The purpose of this literature review is to provide an overview of current bioactive materials for caries management.

Peptide Designs for Use in Caries Management: A Systematic Review

The objective of this study was to review the design methods that have been used to create peptides for use in caries management. Two independent researchers systematically reviewed many in vitro studies in which peptides were designed for use in caries management. They assessed the risk of bias in the included studies. This review identified 3592 publications, of which 62 were selected. Forty-seven studies reported 57 antimicrobial peptides. Among them, 31 studies (66%, 31/47) used the template-based design method; 9 studies (19%, 9/47) used the conjugation method; and 7 studies (15%, 7/47) used other methods, such as the synthetic combinatorial technology method, the de novo design method and cyclisation. Ten studies reported mineralising peptides. Seven of these (70%, 7/10) used the template-based design method, two (20%, 2/10) used the de novo design method, and one study (10%, 1/10) used the conjugation method. In addition, five studies developed their own peptides with antimicrobial and mineralising properties. These studies used the conjugation method. Our assessment for the risk of bias in the 62 reviewed studies showed that 44 publications (71%, 44/62) had a medium risk and that 3 publications had a low risk (5%, 3/62). The two most common methods for developing peptides for use in caries management that were used in these studies were the template-based design method and the conjugation method.

Peptides in Dentistry: A Scoping Review

Currently, it remains unclear which specific peptides could be appropriate for applications in different fields of dentistry. The aim of this scoping review was to scan the contemporary scientific papers related to the types, uses and applications of peptides in dentistry at the moment. Literature database searches were performed in the following databases: PubMed/MEDLINE, Scopus, Web of Science, Embase, and Scielo. A total of 133 articles involving the use of peptides in dentistry-related applications were included. The studies involved experimental designs in animals, microorganisms, or cells; clinical trials were also identified within this review. Most of the applications of peptides included caries management, implant osseointegration, guided tissue regeneration, vital pulp therapy, antimicrobial activity, enamel remineralization, periodontal therapy, the surface modification of tooth implants, and the modification of other restorative materials such as dental adhesives and denture base resins. The in vitro and in vivo studies included in this review suggested that peptides may have beneficial effects for treating early carious lesions, promoting cell adhesion, enhancing the adhesion strength of dental implants, and in tissue engineering as healthy promotors of the periodontium and antimicrobial agents. The lack of clinical trials should be highlighted, leaving a wide space available for the investigation of peptides in dentistry.

Growing Global Research Interest in Antimicrobial Peptides for Caries Management: A Bibliometric Analysis

Objective: Researchers are studying the use of antimicrobial peptides as functional biomaterials to prevent and treat dental caries. This study aims to investigate the global research interest in antimicrobial peptides for caries management. Methods: Two independent investigators systematically searched with keywords ('Caries' OR 'Dental caries') AND ('Antimicrobial peptide' OR 'AMP' OR 'Statherin' OR 'Histatin' OR 'Defensin' OR 'Cathelicidin') on Web of Science, PubMed and Scopus. They removed duplicate publications and screened the titles and abstracts to identify relevant publications. The included publications were summarized and classified as laboratory studies, clinical trials or reviews. The citation count and citation density of the three publication types were compared using a one-way analysis of variance. The publications' bibliometric data were analyzed using the Bibliometrix program. Results: This study included 163 publications with 115 laboratory studies (71%), 29 clinical trials (18%) and 19 reviews (11%). The number of publications per year have increased steadily since 2002. The citation densities (mean ± SD) of laboratory study publications (3.67 ± 2.73) and clinical trial publications (2.63 ± 1.85) were less than that of review articles (5.79 ± 1.27) (p = 0.002). The three publication types had no significant difference in citation count (p = 0.54). Most publications (79%, 129/163) reported the development of a novel antimicrobial peptide. China (52/163, 32%) and the US (29/163, 18%) contributed to 50% (81/163) of the publications. Conclusion: This bibliometric analysis identified an increasing trend in global interest in antimicrobial peptides for caries management since 2002. The main research topic was the development of novel antimicrobial peptides. Most publications were laboratory studies, as were the three publications with the highest citation counts. Laboratory studies had high citation counts, whereas reviews had high citation density.