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Enax J, Ganss B, Amaechi BT, Schulze zur Wiesche E, Meyer F. The composition of the dental pellicle: an updated literature review. FRONTIERS IN ORAL HEALTH 2023; 4:1260442. [PMID: 37899941 PMCID: PMC10600522 DOI: 10.3389/froh.2023.1260442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 09/26/2023] [Indexed: 10/31/2023] Open
Abstract
Background The dental pellicle is a thin layer of up to several hundred nm in thickness, covering the tooth surface. It is known to protect the teeth from acid attacks through its selective permeability and it is involved in the remineralization process of the teeth. It functions also as binding site and source of nutrients for bacteria and conditioning biofilm (foundation) for dental plaque formation. Methods For this updated literature review, the PubMed database was searched for the dental pellicle and its composition. Results The dental pellicle has been analyzed in the past years with various state-of-the art analytic techniques such as high-resolution microscopic techniques (e.g., scanning electron microscopy, atomic force microscopy), spectrophotometry, mass spectrometry, affinity chromatography, enzyme-linked immunosorbent assays (ELISA), and blotting-techniques (e.g., western blot). It consists of several different amino acids, proteins, and proteolytic protein fragments. Some studies also investigated other compounds of the pellicle, mainly fatty acids, and carbohydrates. Conclusions The dental pellicle is composed mainly of different proteins, but also fatty acids, and carbohydrates. Analysis with state-of-the-art analytical techniques have uncovered mainly acidic proline-rich proteins, amylase, cystatin, immunoglobulins, lysozyme, and mucins as main proteins of the dental pellicle. The pellicle has protective properties for the teeth. Further research is necessary to gain more knowledge about the role of the pellicle in the tooth remineralization process.
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Affiliation(s)
- Joachim Enax
- Research Department, Dr. Kurt Wolff GmbH & Co. KG, Bielefeld, Germany
| | - Bernhard Ganss
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | - Bennett T. Amaechi
- Department of Comprehensive Dentistry, School of Dentistry, University of Texas Health San Antonio, San Antonio, TX, United States
| | | | - Frederic Meyer
- Research Department, Dr. Kurt Wolff GmbH & Co. KG, Bielefeld, Germany
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Robey PG, Baum BJ. Ahead of her time: The multidimensional impact of Marie Ussing Nylen. Oral Dis 2023; 29 Suppl 1:870-877. [PMID: 36151928 DOI: 10.1111/odi.14392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 09/21/2022] [Indexed: 11/26/2022]
Abstract
Marie Ussing Nylen was a trail blazing scientist and administrative leader at the US National Institutes of Health. She accomplished this when it was extremely difficult for a woman to do so. She was also a whole person - a wife, mother, and talented athlete, that is, a well-rounded person by any definition. She was a gift to dental and oral science, as well as to those fortunate enough to know and work with her.
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Affiliation(s)
- Pamela Gehron Robey
- Skeletal Biology Section, National Institute of Dental and Craniofacial Research, Bethesda, Maryland, USA
| | - Bruce J Baum
- Scientist Emeritus, National Institute of Dental and Craniofacial Research, Bethesda, Maryland, USA
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Seredin P, Goloshchapov D, Kashkarov V, Khydyakov Y, Nesterov D, Ippolitov I, Ippolitov Y, Vongsvivut J. Development of a Hybrid Biomimetic Enamel-Biocomposite Interface and a Study of Its Molecular Features Using Synchrotron Submicron ATR-FTIR Microspectroscopy and Multivariate Analysis Techniques. Int J Mol Sci 2022; 23:11699. [PMID: 36233001 PMCID: PMC9569639 DOI: 10.3390/ijms231911699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 09/26/2022] [Accepted: 09/29/2022] [Indexed: 11/17/2022] Open
Abstract
Using a biomimetic strategy and bioinspired materials, our work proposed a new technological approach to create a hybrid transitional layer between enamel and dental biocomposite. For this purpose, an amino acid booster conditioner based on a set of polar amino acids (lysine, arginine, hyaluronic acid), calcium alkali, and a modified adhesive based on BisGMA and nanocrystalline carbonate-substituted hydroxyapatite are used during dental enamel restoration. The molecular properties of the hybrid interface formed using the proposed strategy were understood using methods of multivariate statistical analysis of spectral information collected using the technique of synchrotron infrared microspectroscopy. The results obtained indicate the possibility of forming a bonding that mimics the properties of natural tissue with controlled molecular properties in the hybrid layer. The diffusion of the amino acid booster conditioner component, the calcium alkali, and the modified adhesive with nanocrystalline carbonate-substituted hydroxyapatite in the hybrid interface region creates a structure that should stabilize the reconstituted crystalline enamel layer. The developed technology can form the basis for an individualized, personalized approach to dental enamel restorations.
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Affiliation(s)
- Pavel Seredin
- Solid State Physics and Nanostructures Department, Voronezh State University, University sq.1, 394018 Voronezh, Russia
| | - Dmitry Goloshchapov
- Solid State Physics and Nanostructures Department, Voronezh State University, University sq.1, 394018 Voronezh, Russia
| | - Vladimir Kashkarov
- Solid State Physics and Nanostructures Department, Voronezh State University, University sq.1, 394018 Voronezh, Russia
| | - Yury Khydyakov
- Solid State Physics and Nanostructures Department, Voronezh State University, University sq.1, 394018 Voronezh, Russia
| | - Dmitry Nesterov
- Solid State Physics and Nanostructures Department, Voronezh State University, University sq.1, 394018 Voronezh, Russia
| | - Ivan Ippolitov
- Department of Pediatric Dentistry with Orthodontia, Voronezh State Medical University, Studentcheskaya st. 11, 394006 Voronezh, Russia
| | - Yuri Ippolitov
- Department of Pediatric Dentistry with Orthodontia, Voronezh State Medical University, Studentcheskaya st. 11, 394006 Voronezh, Russia
| | - Jitraporn Vongsvivut
- Australian Synchrotron (Synchrotron Light Source Australia Pty Ltd.), 800 Blackburn Rd, Clayton, VIC 3168, Australia
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4
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Leiva-Sabadini C, Schuh CM, Barrera NP, Aguayo S. Ultrastructural characterisation of young and aged dental enamel by atomic force microscopy. J Microsc 2022; 288:185-192. [PMID: 35621144 DOI: 10.1111/jmi.13126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/28/2022] [Accepted: 05/19/2022] [Indexed: 11/28/2022]
Abstract
Recent advances in atomic force microscopy (AFM) have allowed the characterisation of dental-associated biomaterials and biological surfaces with high-resolution. In this context, the topography of dental enamel - the hardest mineralised tissue in the body - has been explored with AFM-based approaches at the micro-scale. With age, teeth are known to suffer changes that can impact their structural stability and function; however, changes in enamel structure because of ageing have not yet been explored with nanoscale resolution. Therefore, the aim of this exploratory work was to optimise an approach to characterise the ultrastructure of dental enamel and determine potential differences in topography, hydroxyapatite (HA) crystal size, and surface roughness at the nanoscale associated to ageing. For this, a total of six teeth were collected from human donors from which enamel specimens were prepared. By employing intermittent contact (AC mode) imaging, HA crystals were characterised in both transversal and longitudinal orientation (respect to surface plane) with high-resolution in environmental conditions. The external enamel surface displayed the presence of a pellicle-like coating on its surface, that was not observable on cleaned specimens. Acid-etching exposed crystals that were imaged and morphologically characterised in high-resolution at the nanoscale in both the external and internal regions of enamel in older and younger specimens. Our results demonstrated important individual variations in HA crystal width and roughness parameters across the analysed specimens; however, an increase in surface roughness and decrease in HA width was observed for the pooled older external enamel group compared to younger specimens. Overall, high-resolution AFM was an effective approach for the qualitative and quantitative characterisation of human dental enamel ultrastructure. Future work should focus on exploring the ageing of dental enamel with increased sample sizes to compensate for individual differences as well as other potential confounding factors such as behavioural habits and mechanical forces. Lay abstract: Currently, advanced microscopy techniques such as atomic force microscopy (AFM) can be used to characterise surfaces relevant to dentistry with great detail. Among these surfaces of interest, dental enamel - the hardest mineralised tissue in the body- is important as it protects the deeper areas of the tooth from harmful stimuli such as sudden temperature changes, bacterial penetration, and chemical attack. Also, dental enamel is an important surface for the adhesion of some types of dental restorations; thus, its structure and organisation is highly relevant for both dental scientists and clinicians. With age, teeth are known to suffer changes that can impact their structural stability and function; however, changes in enamel structure as a result of ageing have not yet been explored with nanoscale resolution. It is necessary to develop and optimise AFM-based techniques in order to process specimens from dental samples across different age groups for ageing-associated nanoscale studies in the future. Therefore, the aim of this investigation was to optimise an approach to characterise the ultrastructure of dental enamel and determine potential differences in enamel topography, hydroxyapatite (HA) crystal size, and surface roughness at the nanoscale associated to ageing. For this, human enamel specimens obtained from a total of six teeth were collected and analysed with AFM, and HA crystals were characterised in both transversal and longitudinal orientation with high-resolution in environmental conditions. Upon AFM observation, sound superficial enamel displayed the presence of a pellicle-like coating on its surface, that was not observable after specimens were cleaned. Furthermore, acid-etching exposed HA crystals that were imaged and morphologically characterised in high-resolution at the nanoscale across different regions of enamel in older and younger specimens. We observed important individual variations in HA crystal width and roughness parameters across the analysed specimens and groups, suggesting individual as well as age-associated differences. Overall, high-resolution AFM was an effective approach for the qualitative and quantitative characterisation of human dental enamel ultrastructure at the nanometer range with minimal sample preparation. This proof-of-concept work can pave the way for future studies employing increased sample sizes to compensate for individual differences and population level factors. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Camila Leiva-Sabadini
- School of Dentistry, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christina Map Schuh
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Nelson P Barrera
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Sebastian Aguayo
- School of Dentistry, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile.,Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
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Fabritius-Vilpoux K, Enax J, Mayweg D, Meyer F, Herbig M, Raabe D, Fabritius HO. Ultrastructural changes of bovine tooth surfaces under erosion in presence of biomimetic hydroxyapatite. BIOINSPIRED BIOMIMETIC AND NANOBIOMATERIALS 2021. [DOI: 10.1680/jbibn.21.00017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Enamel and dentin are susceptible to acids from food sources leading to dental erosion, a global problem affecting millions of individuals. Particulate hydroxyapatite (HAP) on the tooth surface can influence the effects of acid attacks. Standardized bovine enamel and dentin samples with artificial saliva are used in an in vitro cyclic demineralization–remineralization protocol to analyze the structural changes experienced by tooth surfaces using high-resolution scanning electron microscopy and to evaluate the potential of a HAP-based oral care gel in the protection of teeth from erosive attacks. The interfaces between HAP particle and enamel HAP crystallites are investigated using focused ion beam preparation and transmission electron microscopy. The results show that erosion with phosphoric acid severely affects enamel crystallites and dentin tubules, while artificial saliva leads to remineralization effects. The HAP-gel forms a microscopic layer on both enamel and dentin surfaces. Upon acid exposure, this layer is sacrificed before the native tooth tissues are affected, leading to significantly lower degrees of demineralization compared to the controls. This demonstrates that the use of particulate HAP as a biomaterial in oral care formulations can help protect enamel and dentin surfaces from erosive attacks during meals using a simple and effective protection principle.
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Affiliation(s)
- Kathia Fabritius-Vilpoux
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
| | - Joachim Enax
- Research Department, Dr. Kurt Wolff GmbH & Co. KG, Bielefeld, Germany
| | - David Mayweg
- Department of Physics, Chalmers University of Technology, Göteborg, Sweden; Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
| | - Frederic Meyer
- Research Department, Dr. Kurt Wolff GmbH & Co. KG, Bielefeld, Germany
| | - Michael Herbig
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
| | - Dierk Raabe
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
| | - Helge-Otto Fabritius
- Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany; Bionics and Materials Development, Hamm-Lippstadt University of Applied Sciences, Hamm, Germany
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Bijle MN, Pichika MR, Mak KK, Parolia A, Babar MG, Yiu C, Daood U. Concentration-Dependent Multi-Potentiality of L-Arginine: Antimicrobial Effect, Hydroxyapatite Stability, and MMPs Inhibition. Molecules 2021; 26:6605. [PMID: 34771014 PMCID: PMC8586951 DOI: 10.3390/molecules26216605] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/17/2021] [Accepted: 10/17/2021] [Indexed: 11/16/2022] Open
Abstract
This study's objective was to examine L-arginine (L-arg) supplementation's effect on mono-species biofilm (Streptococcus mutans/Streptococcus sanguinis) growth and underlying enamel substrates. The experimental groups were 1%, 2%, and 4% arg, and 0.9% NaCl was used as the vehicle control. Sterilised enamel blocks were subjected to 7-day treatment with test solutions and S. mutans/S. sanguinis inoculum in BHI. Post-treatment, the treated biofilms stained for live/dead bacterial cells were analysed using confocal microscopy. The enamel specimens were analysed using X-ray diffraction crystallography (XRD), Raman spectroscopy (RS), and transmission electron microscopy (TEM). The molecular interactions between arg and MMP-2/MMP-9 were determined by computational molecular docking and MMP assays. With increasing arg concentrations, bacterial survival significantly decreased (p < 0.05). The XRD peak intensity with 1%/2% arg was significantly higher than with 4% arg and the control (p < 0.05). The bands associated with the mineral phase by RS were significantly accentuated in the 1%/2% arg specimens compared to in other groups (p < 0.05). The TEM analysis revealed that 4% arg exhibited an ill-defined shape of enamel crystals. Docking of arg molecules to MMPs appears feasible, with arg inhibiting MMP-2/MMP-9 (p < 0.05). L-arginine supplementation has an antimicrobial effect on mono-species biofilm. L-arginine treatment at lower (1%/2%) concentrations exhibits enamel hydroxyapatite stability, while the molecule has the potential to inhibit MMP-2/MMP-9.
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Affiliation(s)
| | - Mallikarjuna Rao Pichika
- Pharmaceutical Chemistry, School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (M.R.P.); (K.-K.M.)
| | - Kit-Kay Mak
- Pharmaceutical Chemistry, School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (M.R.P.); (K.-K.M.)
| | - Abhishek Parolia
- Clinical Dentistry Division, School of Dentistry, International Medical University, Kuala Lumpur 57000, Malaysia;
| | - Muneer Gohar Babar
- Children and Community Oral Health, School of Dentistry, International Medical University, Kuala Lumpur 57000, Malaysia;
| | - Cynthia Yiu
- Paediatric Dentistry, Faculty of Dentistry, The University of Hong Kong, Hong Kong;
| | - Umer Daood
- Clinical Dentistry Division, School of Dentistry, International Medical University, Kuala Lumpur 57000, Malaysia;
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Orilisi G, Tosco V, Monterubbianesi R, Notarstefano V, Özcan M, Putignano A, Orsini G. ATR-FTIR, EDS and SEM evaluations of enamel structure after treatment with hydrogen peroxide bleaching agents loaded with nano-hydroxyapatite particles. PeerJ 2021; 9:e10606. [PMID: 33575125 PMCID: PMC7849511 DOI: 10.7717/peerj.10606] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 11/28/2020] [Indexed: 01/04/2023] Open
Abstract
Background Tooth whitening is one of the most requested dental treatments, but it still presents some side effects. Indeed, the bleaching agent can generate patients’ discomfort and dental hard tissue damages, not achieving an efficient and long-lasting treatment with optimum whitening effect. To overcome these limitations, the bleaching agents containing nano-hydroxyapatite can represent a reliable solution to avoid these detrimental effects. Methods In this study, human third molars were treated with commercial bleaching agents, containing nano-hydroxyapatite (nHA) and 6% (at-home treatment), 12% and 18% (in-office treatments) of hydrogen peroxide (HP), named respectively G1, G2 and G3. The results were evaluated descriptively and analytically using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS), comparing the treated groups with a commercial gel containing 10% carbamide peroxide (CONV) and with a non-treated control group (CTRL). Results ATR-FTIR analysis revealed a similar composition in carbonates and phosphates for CTRL, G1 and G2 groups, which showed no significant differences in their spectral profiles; an increased amount of organic matter was found in G3, while CONV displayed an intermediate behavior. SEM analysis did not highlight significant changes in the enamel microstructure of G1 and CONV when compared to CTRL; the pattern observed in G2 presented a slight increase of enamel irregularities, while G3 displayed a partial removal of the aprismatic layer and microporosities. No evident effects due to nHA were observed in the structure of the hydroxyapatite component of G1, G2 and CONV, if compared to CTRL, while G3 showed a slight loss of crystallinity. In all groups, EDS identified slight changes in the concentration of chemical elements O and Ca, while the Ca/P ratio was similar when compared to CTRL. Conclusion The obtained results suggest that the application of the tested commercial bleaching agents, with a concentration of HP up to 12%, does not alter the morphological and chemical composition of the enamel surface and maintains its crystallinity.
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Affiliation(s)
- Giulia Orilisi
- Department of Clinical Sciences and Stomatology, Polytechnic University of Marche, Ancona, Italy
| | - Vincenzo Tosco
- Department of Clinical Sciences and Stomatology, Polytechnic University of Marche, Ancona, Italy
| | - Riccardo Monterubbianesi
- Department of Clinical Sciences and Stomatology, Polytechnic University of Marche, Ancona, Italy
| | - Valentina Notarstefano
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy
| | - Mutlu Özcan
- Division of Dental Biomaterials, Center for Dental and Oral Medicine, Clinic for Reconstructive Dentistry, University of Zurich, Zurich, Switzerland
| | - Angelo Putignano
- Department of Clinical Sciences and Stomatology, Polytechnic University of Marche, Ancona, Italy
| | - Giovanna Orsini
- Department of Clinical Sciences and Stomatology, Polytechnic University of Marche, Ancona, Italy
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Bijle MN, Abdalla MM, Ashraf U, Ekambaram M, Yiu CKY. Enamel remineralization potential of arginine-fluoride varnish in a multi-species bacterial pH-cycling model. J Dent 2020; 104:103528. [PMID: 33188848 DOI: 10.1016/j.jdent.2020.103528] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 10/23/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022] Open
Abstract
OBJECTIVES To examine the enamel fluoride uptake and remineralization potential of arginine-fluoride (Arg-NaF) varnishes in a simulated clinical condition using a multi-species bacterial pH-cycling model. METHODS L-Arginine (at 1 %, 2 %, and 4 % by wt.) was incorporated in a 5 % NaF varnish. Experimental and control groups were: 1 % Arg-NaF; 2 % Arg-NaF; 4 % Arg-NaF; NaF and no treatment. Artificial incipient caries-like lesions were formed on 30 enamel specimen blocks (n = 6). The specimens underwent multi-species bacterial pH-cycling in an artificial mouth system using oral biofilm reactor for 72 h after treatment. The specimens were evaluated for mineral density using micro-CT, Ca/P ratio with SEM-EDX, enamel fluoride uptake (EFU) and plaque fluoride uptake (PFU). RESULTS Increasing concentrations of Arg in NaF varnish significantly increased the EFU of incipient caries-like lesions (p < 0.001). The PFU for 1 % Arg-NaF was significantly higher than 4 % Arg-NaF and the control NaF (p < 0.05). Post pH-cycling, Ca/P ratio with 1 %/2 % Arg-NaF was closest to hydroxyapatite (1.67). Mineral gain and % remineralization of 1 %/2 % Arg-NaF was significantly higher than the control NaF varnish (p < 0.05). CONCLUSION The prebiotic L-arginine (at 1 %/2 % by wt.) in a 5 % NaF varnish enhanced the enamel fluoride uptake and remineralization potential of the conventional 5 % NaF varnish. CLINICAL SIGNIFICANCE The Arg-NaF varnish addresses the limitations of fluorides on cariogenic biofilms. The Arg-NaF varnish appears a promising caries-preventive regimen that counters the pathogenic biofilms by Arg and promotes remineralization with fluorides. In high caries-risk patients, professional application of Arg-NaF varnish might aid to alleviate the global burden of dental caries.
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Affiliation(s)
| | - Mohamed Mahmoud Abdalla
- Paediatric Dentistry, Faculty of Dentistry, The University of Hong Kong, Hong Kong. Lecturer, Dental Biomaterials, Faculty of Dental Medicine, Al-Azhar University, Cairo, Egypt.
| | - Usman Ashraf
- Paediatric Dentistry, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
| | - Manikandan Ekambaram
- Paediatric Dentistry, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
| | - Cynthia Kar Yung Yiu
- Paediatric Dentistry, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
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Koldehoff J, Swain MV, Schneider GA. The geometrical structure of interfaces in dental enamel: A FIB-STEM investigation. Acta Biomater 2020; 104:17-27. [PMID: 31917293 DOI: 10.1016/j.actbio.2019.12.040] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 12/20/2019] [Accepted: 12/31/2019] [Indexed: 11/26/2022]
Abstract
In this study a high resolution structural analysis revealed that enamel prisms are surrounded by an interface that is discontinuous with frequent mineral to mineral contact separated by gaps. This contact manifests either by crystallites bridging the boundary between prismatic and interprismatic enamel or continuous crystallites curving and bridging the interprismatic enamel to the prisms. The geometrical resolution of this TEM investigation of the interfaces is ≤2 nm as a basis for micromechanical models. Within this resolution, contrary to existing structural descriptions of dental enamel structure in materials science literature, here the crystallites themselves are shown to be either in direct contact with each other, sometimes even fusing together, or are separated by gaps. Image analysis revealed that on average only 57 ± 15% of the interface consists of points of no contact between crystallites. This work reveals structural features of dental enamel that contribute important understanding to both the architecture and mechanical properties of this biological material. A new structural model is proposed and the implications for the mechanical properties of dental enamel are discussed. STATEMENT OF SIGNIFICANCE: In this study a high resolution structural analysis, employing focused ion beam and transmission electron microscopy revealed that enamel prisms are surrounded by interfaces that are discontinuous with frequent mineral to mineral contact separated by gaps. Although the interfaces in enamel have been investigated previously, existing studies are lacking in detail considering the geometry and morphology of the interfaces. We think that this result is of great importance when it comes to the understanding of the mechanical properties. In our opinion the concept of soft sheaths is no longer feasible. The resulting observations are included in a new structural model which provides new qualitative insights into the mechanical behavior. Existing analytical models were applied to simulate the new geometrical structure.
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Abstract
Enamel is the hardest and most resilient tissue in the human body. Enamel includes morphologically aligned, parallel, ∼50 nm wide, microns-long nanocrystals, bundled either into 5-μm-wide rods or their space-filling interrod. The orientation of enamel crystals, however, is poorly understood. Here we show that the crystalline c-axes are homogenously oriented in interrod crystals across most of the enamel layer thickness. Within each rod crystals are not co-oriented with one another or with the long axis of the rod, as previously assumed: the c-axes of adjacent nanocrystals are most frequently mis-oriented by 1°-30°, and this orientation within each rod gradually changes, with an overall angle spread that is never zero, but varies between 30°-90° within one rod. Molecular dynamics simulations demonstrate that the observed mis-orientations of adjacent crystals induce crack deflection. This toughening mechanism contributes to the unique resilience of enamel, which lasts a lifetime under extreme physical and chemical challenges.
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11
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Yilmaz ED, Koldehoff J, Schneider GA. On the systematic documentation of the structural characteristics of bovine enamel: A critic to the protein sheath concept. Dent Mater 2018; 34:1518-1530. [DOI: 10.1016/j.dental.2018.06.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 05/24/2018] [Accepted: 06/07/2018] [Indexed: 11/28/2022]
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12
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Shahmoradi M, Swain MV. Micro-CT analysis of naturally arrested brown spot enamel lesions. J Dent 2017; 56:105-111. [DOI: 10.1016/j.jdent.2016.11.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 11/09/2016] [Accepted: 11/19/2016] [Indexed: 11/28/2022] Open
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13
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Abdallah MN, Eimar H, Bassett DC, Schnabel M, Ciobanu O, Nelea V, McKee MD, Cerruti M, Tamimi F. Diagenesis-inspired reaction of magnesium ions with surface enamel mineral modifies properties of human teeth. Acta Biomater 2016; 37:174-83. [PMID: 27060619 DOI: 10.1016/j.actbio.2016.04.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 03/09/2016] [Accepted: 04/06/2016] [Indexed: 11/18/2022]
Abstract
UNLABELLED Mineralized tissues such as teeth and bones consist primarily of highly organized apatitic calcium-phosphate crystallites within a complex organic matrix. The dimensions and organization of these apatite crystallites at the nanoscale level determine in part the physical properties of mineralized tissues. After death, geological processes such as diagenesis and dolomitization can alter the crystallographic properties of mineralized tissues through cycles of dissolution and re-precipitation occurring in highly saline environments. Inspired by these natural exchange phenomena, we investigated the effect of hypersalinity on tooth enamel. We discovered that magnesium ions reacted with human tooth enamel through a process of dissolution and re-precipitation, reducing enamel crystal size at the surface of the tooth. This change in crystallographic structure made the teeth harder and whiter. Salt-water rinses have been used for centuries to ameliorate oral infections; however, our discovery suggests that this ancient practice could have additional unexpected benefits. STATEMENT OF SIGNIFICANCE Here we describe an approach inspired by natural geological processes to modify the properties of a biomineral - human tooth enamel. In this study we showed that treatment of human tooth enamel with solutions saturated with magnesium induced changes in the nanocrystals at the outer surface of the protective enamel layer. As a consequence, the physical properties of the tooth were modified; tooth microhardness increased and the color shade became whiter, thus suggesting that this method could be used as a clinical treatment to improve dental mechanical properties and esthetics. Such an approach is simple and straightforward, and could also be used to develop new strategies to synthesize and modify biominerals for biomedical and industrial applications.
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Affiliation(s)
| | - Hazem Eimar
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada
| | - David C Bassett
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada
| | - Martin Schnabel
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada
| | - Ovidiu Ciobanu
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada
| | - Valentin Nelea
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada
| | - Marc D McKee
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada; Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, H3A 0C7 Montreal, QC, Canada
| | - Marta Cerruti
- Department of Mining and Materials Engineering, McGill University, H3A 0E8 Montreal, QC, Canada
| | - Faleh Tamimi
- Faculty of Dentistry, McGill University, H3A 0C7 Montreal, QC, Canada.
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Abstract
Enamel proteins form a scaffold for growing hydroxyapatite crystals during enamel formation. They are then almost completely degraded during enamel maturation, resulting in a protein content of only 1% (w/v) in mature enamel. Nevertheless, this small amount of remaining proteins has important effects on the mechanical and structural properties of enamel and on the electrostatic properties of its surface. To analyze how enamel proteins affect tooth erosion, human enamel specimens were deproteinated. Surface microhardness (SMH), surface reflection intensity (SRI) and calcium release of both deproteinated and control specimens were monitored while continuously eroding them. The deproteination itself already reduced the initial SMH and SRI of the enamel significantly (p < 0.001 and p < 0.01). During the course of erosion, the progression of all three evaluated parameters differed significantly between the two groups (p < 0.001 for each). The deproteinated enamel lost its SMH and SRI faster, and released more calcium than the control group, but these differences were only significant at later stages of erosion, where not only surface softening but surface loss can be observed. We conclude that enamel proteins have a significant effect on erosion, protecting the enamel and slowing down the progression of erosion when irreversible surface loss starts to occur.
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15
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Effect of tooth bleaching agents on protein content and mechanical properties of dental enamel. Acta Biomater 2015; 20:120-128. [PMID: 25841347 DOI: 10.1016/j.actbio.2015.03.035] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 03/24/2015] [Accepted: 03/28/2015] [Indexed: 11/23/2022]
Abstract
This study investigated the effect of two bleaching agents, 16% carbamide peroxide (CP) and 35% hydrogen peroxide (HP), on the mechanical properties and protein content of human enamel from freshly extracted teeth. The protein components of control and treated enamel were extracted and examined on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Marked reduction of the protein matrix and random fragmentation of the enamel proteins after bleaching treatments was found. The mechanical properties were analyzed with Vickers indentations to characterize fracture toughness, and nanoindentation to establish enamel hardness, elastic modulus and creep deformation. Results indicate that the hardness and elastic modulus of enamel were significantly reduced after treatment with CP and HP. After bleaching, the creep deformation at maximum load increased and the recovery upon unloading reduced. Crack lengths of CP and HP treated enamel were increased, while fracture toughness decreased. Additionally, the microstructures of fractured and indented samples were examined with field emission gun scanning electron microscopy (FEG-SEM) showing distinct differences in the fracture surface morphology between pre- and post-bleached enamel. In conclusion, tooth bleaching agents can produce detrimental effects on the mechanical properties of enamel, possibly as a consequence of damaging or denaturing of its protein components.
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Abdallah MN, Light N, Amin WM, Retrouvey JM, Cerruti M, Tamimi F. Development of a composite resin disclosing agent based on the understanding of tooth staining mechanisms. J Dent 2014; 42:697-708. [DOI: 10.1016/j.jdent.2014.03.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 02/24/2014] [Accepted: 03/09/2014] [Indexed: 12/11/2022] Open
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17
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Zwier N, Huysmans MCDNJM, Jager DHJ, Ruben J, Bronkhorst EM, Truin GJ. Saliva Parameters and Erosive Wear in Adolescents. Caries Res 2013; 47:548-52. [PMID: 23774653 DOI: 10.1159/000350361] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 02/24/2013] [Indexed: 11/19/2022] Open
Affiliation(s)
- N Zwier
- College of Dental Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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