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Kegulian NC, Visakan G, Bapat RA, Moradian-Oldak J. Ameloblastin and its multifunctionality in amelogenesis: a review. Matrix Biol 2024:S0945-053X(24)00068-4. [PMID: 38815936 DOI: 10.1016/j.matbio.2024.05.007] [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: 04/02/2024] [Revised: 05/16/2024] [Accepted: 05/24/2024] [Indexed: 06/01/2024]
Abstract
Extracellular matrix proteins play crucial roles in the formation of mineralized tissues like bone and teeth via multifunctional mechanisms. In tooth enamel, ameloblastin (Ambn) is one such multifunctional extracellular matrix protein implicated in cell signaling and polarity, cell adhesion to the developing enamel matrix, and stabilization of prismatic enamel morphology. To provide a perspective for Ambn structure and function, we begin this review by describing dental enamel and enamel formation (amelogenesis) followed by a description of enamel extracellular matrix. We then summarize the established domains and motifs in Ambn protein, human amelogenesis imperfecta cases, and genetically engineered mouse models involving mutated or null Ambn. We subsequently delineate in silico, in vitro, and in vivo evidence for the amphipathic helix in Ambn as a proposed cell-matrix adhesive and then more recent in vitro evidence for the multitargeting domain as the basis for dynamic interactions of Ambn with itself, amelogenin, and membranes. The multitargeting domain facilitates tuning between Ambn-membrane interactions and self/co-assembly and supports a likely overall role for Ambn as a matricellular protein. We anticipate that this review will enhance the understanding of multifunctional matrix proteins by consolidating diverse mechanisms through which Ambn contributes to enamel extracellular matrix mineralization.
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Affiliation(s)
- Natalie C Kegulian
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar St., CSA 148, Los Angeles, CA 90033, USA
| | - Gayathri Visakan
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar St., CSA 148, Los Angeles, CA 90033, USA
| | - Rucha Arun Bapat
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar St., CSA 148, Los Angeles, CA 90033, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar St., CSA 148, Los Angeles, CA 90033, USA..
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2
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Vetyskova V, Hubalek M, Sulc J, Prochazka J, Vondrasek J, Vydra Bousova K. Proteolytic profiles of two isoforms of human AMBN expressed in E. coli by MMP-20 and KLK-4 proteases. Heliyon 2024; 10:e24564. [PMID: 38298721 PMCID: PMC10828707 DOI: 10.1016/j.heliyon.2024.e24564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 12/16/2023] [Accepted: 01/10/2024] [Indexed: 02/02/2024] Open
Abstract
Ameloblastin is a protein in biomineralization of tooth enamel. However recent results indicate that this is probably not its only role in an organism. Enamel matrix formation represents a complex process enabled via specific crosslinking of two proteins - the most abundant amelogenin and the ameloblastin (AMBN). The human AMBN (hAMBN) gene possesses 13 protein coding exons with alternatively spliced transcripts and the longest isoform about 447 amino acid residues. It has been described that AMBN molecules in vitro assemble into oligomers via a sequence encoded by exon 5. Enamel is formed by the processing of enamel proteins by two specific proteases - enamelysin (MMP-20) and kallikrein 4 (KLK-4). The scaffold made of AMEL and non-amelogenin proteins is cleaved and removed from the developed tooth enamel. The hAMBN is expressed in two isoforms (ISO I and II), which could lead to their different utilization determined by distinct proteolytic profiles. In this study, we compared proteolytic profiles of both isoforms of hAMBN expressed in E. coli after proteolysis by MMP-20, KLK-4, and their 1:2 mixture. Proteolysis products were analysed and cleavage sites were identified by mass spectrometry. The proteolytic profiles of two AMBN isoforms showed different results, although we have to determine that the analysed AMBN was not post-translationally modified as expressed in prokaryotic cells. These results may lead to the suggestion of potentially divergent roles of AMBN isoforms cleavage products in various cell signalling pathways such as calcium buffering or signalling cascades.
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Affiliation(s)
- Veronika Vetyskova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 16000, Prague, Czech Republic
| | - Martin Hubalek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 16000, Prague, Czech Republic
| | - Josef Sulc
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 16000, Prague, Czech Republic
- Department of Physical and Macromolecular Chemistry, Faculty of Natural Sciences, Charles University, Hlavova 8, 128 00 Prague 2, Czech Republic
| | - Jan Prochazka
- Institute of Molecular Genetics of the Czech Academy of Sciences, Videnska 5, 14000, Prague, Czech Republic
| | - Jiri Vondrasek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 16000, Prague, Czech Republic
| | - Kristyna Vydra Bousova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 2, 16000, Prague, Czech Republic
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3
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Hany U, Watson C, Liu L, Nikolopoulos G, Smith C, Poulter J, Brown C, Patel A, Rodd H, Balmer R, Harfoush A, Al-Jawad M, Inglehearn C, Mighell A. Novel Ameloblastin Variants, Contrasting Amelogenesis Imperfecta Phenotypes. J Dent Res 2024; 103:22-30. [PMID: 38058155 PMCID: PMC10734210 DOI: 10.1177/00220345231203694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023] Open
Abstract
Amelogenesis imperfecta (AI) comprises a group of rare, inherited disorders with abnormal enamel formation. Ameloblastin (AMBN), the second most abundant enamel matrix protein (EMP), plays a critical role in amelogenesis. Pathogenic biallelic loss-of-function AMBN variants are known to cause recessive hypoplastic AI. A report of a family with dominant hypoplastic AI attributed to AMBN missense change p.Pro357Ser, together with data from animal models, suggests that the consequences of AMBN variants in human AI remain incompletely characterized. Here we describe 5 new pathogenic AMBN variants in 11 individuals with AI. These fall within 3 groups by phenotype. Group 1, consisting of 6 families biallelic for combinations of 4 different variants, have yellow hypoplastic AI with poor-quality enamel, consistent with previous reports. Group 2, with 2 families, appears monoallelic for a variant shared with group 1 and has hypomaturation AI of near-normal enamel volume with pitting. Group 3 includes 3 families, all monoallelic for a fifth variant, which are affected by white hypoplastic AI with a thin intact enamel layer. Three variants, c.209C>G; p.(Ser70*) (groups 1 and 2), c.295T>C; p.(Tyr99His) (group 1), and c.76G>A; p.(Ala26Thr) (group 3) were identified in multiple families. Long-read AMBN locus sequencing revealed these variants are on the same conserved haplotype, implying they originate from a common ancestor. Data presented therefore provide further support for possible dominant as well as recessive inheritance for AMBN-related AI and for multiple contrasting phenotypes. In conclusion, our findings suggest pathogenic AMBN variants have a more complex impact on human AI than previously reported.
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Affiliation(s)
- U. Hany
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
| | - C.M. Watson
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
- North East and Yorkshire Genomic Laboratory Hub, Central Lab, St. James’s University Hospital, Leeds, UK
| | - L. Liu
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
- School of Dentistry, Clarendon Way, University of Leeds, Leeds, UK
| | - G. Nikolopoulos
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
| | - C.E.L. Smith
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
| | - J.A. Poulter
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
| | - C.J. Brown
- Birmingham Dental Hospital, Mill Pool Way, Edgbaston, Birmingham, UK
| | - A. Patel
- LCRN West Midlands Core Team, NIHR Clinical Research Network (CRN), Birmingham Research Park (West Wing), Edgbaston, Birmingham, UK
| | - H.D. Rodd
- Academic Unit of Oral Health Dentistry and Society, School of Clinical Dentistry, University of Sheffield, Sheffield, S Yorks, UK
| | - R. Balmer
- School of Dentistry, Clarendon Way, University of Leeds, Leeds, UK
| | - A. Harfoush
- School of Dentistry, Clarendon Way, University of Leeds, Leeds, UK
| | - M. Al-Jawad
- School of Dentistry, Clarendon Way, University of Leeds, Leeds, UK
| | - C.F. Inglehearn
- Leeds Institute of Medical Research, University of Leeds, St. James’s University Hospital, Leeds, UK
| | - A.J. Mighell
- School of Dentistry, Clarendon Way, University of Leeds, Leeds, UK
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Reseland JE, Heyward CA, Samara A. Revisiting ameloblastin; addressing the EMT-ECM axis above and beyond oral biology. Front Cell Dev Biol 2023; 11:1251540. [PMID: 38020879 PMCID: PMC10679718 DOI: 10.3389/fcell.2023.1251540] [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: 07/01/2023] [Accepted: 10/11/2023] [Indexed: 12/01/2023] Open
Abstract
Ameloblastin (AMBN) is best characterized for its role in dental enamel formation, regulating cell differentiation and mineralization, and cell matrix adhesion. However, AMBN has also been detected in mesenchymal stem cells in addition to bone, blood, and adipose tissue. Using immunofluorescence in a pilot scheme, we identified that AMBN is expressed in different parts of the gastrointestinal (GI) tract. AMBN mRNA and protein detection in several tissues along the length of the GI tract suggests a role for AMBN in the structure and tissue integrity of the extracellular matrix (ECM). Intracellular AMBN expression in subsets of cells indicates a potential alternative role in signaling processes. Of note, our previous functional AMBN promoter analyses had shown that it contains epithelial-mesenchymal transition (EMT) regulatory elements. ΑΜΒΝ is herein presented as a paradigm shift of the possible associations and the spatiotemporal regulation of the ECM regulating the EMT and vice versa, using the example of AMBN expression beyond oral biology.
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Affiliation(s)
- Janne E. Reseland
- Center for Functional Tissue Reconstruction (FUTURE), University of Oslo, Oslo, Norway
- Department of Biomaterials and Oral Research Laboratory, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Catherine A. Heyward
- Department of Biomaterials and Oral Research Laboratory, Faculty of Dentistry, University of Oslo, Oslo, Norway
| | - Athina Samara
- Center for Functional Tissue Reconstruction (FUTURE), University of Oslo, Oslo, Norway
- Department of Biomaterials and Oral Research Laboratory, Faculty of Dentistry, University of Oslo, Oslo, Norway
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Shao C, Bapat RA, Su J, Moradian-Oldak J. Regulation of Hydroxyapatite Nucleation In Vitro through Ameloblastin-Amelogenin Interactions. ACS Biomater Sci Eng 2023; 9:1834-1842. [PMID: 35068157 PMCID: PMC9308824 DOI: 10.1021/acsbiomaterials.1c01113] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Amelogenin (Amel) and ameloblastin (Ambn) are two primary extracellular enamel matrix proteins that play crucial roles for proper thickness, prismatic structure, and robust mechanical properties. Previous studies have shown that Amel and Ambn bind to each other, but the effect of their coassembly on the nucleation of hydroxyapatite (HAP) is unclear. Here, we systematically investigated the coassembly of recombinant mouse Amel and Ambn in various ratios using in situ atomic force microscopy, dynamic light scattering, and transmission electron microscopy. The size of protein particles decreased as the Ambn:Amel ratio increased. To define the coassembly domain on Ambn, we used Ambn-derived peptides and Ambn variants to examine their effects on the amelogenin particle size distribution. We found that the peptide sequence encoded by exon 5 of Ambn affected Amel self-assembly but the variant lacking this sequence did not have any effect on Amel self-assembly. Furthermore, through monitoring the pH change in bulk mineralization solution, we tracked the nucleation behavior of HAP in the presence of Ambn and Amel and found that their coassemblies at different ratios showed varying abilities to stabilize amorphous calcium phosphate. These results demonstrated that Ambn and Amel coassemble with each other via a motif within the sequence encoded by exon 5 of Ambn and cooperate in regulating the nucleation of HAP crystals, enhancing our understanding of the important role of enamel matrix proteins in amelogenesis.
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Affiliation(s)
- Changyu Shao
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, California 90033, United States
| | - Rucha Arun Bapat
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, California 90033, United States
| | - Jingtan Su
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, California 90033, United States
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, California 90033, United States
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6
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Kegulian NC, Langen R, Moradian-Oldak J. The Dynamic Interactions of a Multitargeting Domain in Ameloblastin Protein with Amelogenin and Membrane. Int J Mol Sci 2023; 24:3484. [PMID: 36834897 PMCID: PMC9966149 DOI: 10.3390/ijms24043484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/28/2023] [Accepted: 02/06/2023] [Indexed: 02/12/2023] Open
Abstract
The enamel matrix protein Ameloblastin (Ambn) has critical physiological functions, including regulation of mineral formation, cell differentiation, and cell-matrix adhesion. We investigated localized structural changes in Ambn during its interactions with its targets. We performed biophysical assays and used liposomes as a cell membrane model. The xAB2N and AB2 peptides were rationally designed to encompass regions of Ambn that contained self-assembly and helix-containing membrane-binding motifs. Electron paramagnetic resonance (EPR) on spin-labeled peptides showed localized structural gains in the presence of liposomes, amelogenin (Amel), and Ambn. Vesicle clearance and leakage assays indicated that peptide-membrane interactions were independent from peptide self-association. Tryptophan fluorescence and EPR showed competition between Ambn-Amel and Ambn-membrane interactions. We demonstrate localized structural changes in Ambn upon interaction with different targets via a multitargeting domain, spanning residues 57 to 90 of mouse Ambn. Structural changes of Ambn following its interaction with different targets have relevant implications for the multifunctionality of Ambn in enamel formation.
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Affiliation(s)
- Natalie C. Kegulian
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Ralf Langen
- Department of Neuroscience and Physiology, Department of Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
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7
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Early evolution of enamel matrix proteins is reflected by pleiotropy of physiological functions. Sci Rep 2023; 13:1471. [PMID: 36702824 PMCID: PMC9879986 DOI: 10.1038/s41598-023-28388-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/18/2023] [Indexed: 01/27/2023] Open
Abstract
Highly specialized enamel matrix proteins (EMPs) are predominantly expressed in odontogenic tissues and diverged from common ancestral gene. They are crucial for the maturation of enamel and its extreme complexity in multiple independent lineages. However, divergence of EMPs occured already before the true enamel evolved and their conservancy in toothless species suggests that non-canonical functions are still under natural selection. To elucidate this hypothesis, we carried out an unbiased, comprehensive phenotyping and employed data from the International Mouse Phenotyping Consortium to show functional pleiotropy of amelogenin, ameloblastin, amelotin, and enamelin, genes, i.e. in sensory function, skeletal morphology, cardiovascular function, metabolism, immune system screen, behavior, reproduction, and respiratory function. Mice in all KO mutant lines, i.e. amelogenin KO, ameloblastin KO, amelotin KO, and enamelin KO, as well as mice from the lineage with monomeric form of ameloblastin were affected in multiple physiological systems. Evolutionary conserved motifs and functional pleiotropy support the hypothesis of role of EMPs as general physiological regulators. These findings illustrate how their non-canonical function can still effect the fitness of modern species by an example of influence of amelogenin and ameloblastin on the bone physiology.
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8
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Vetyskova V, Zouharova M, Bousova K. Production of recombinant human ameloblastin by a fully native purification pathway. Protein Expr Purif 2022; 198:106133. [PMID: 35750297 DOI: 10.1016/j.pep.2022.106133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 06/16/2022] [Accepted: 06/19/2022] [Indexed: 12/29/2022]
Abstract
Ameloblastin (Ambn) is an intrinsically disordered protein (IDP) with a specific function of forming heterogenous homooligomers. The oligomeric function is led through a specific sequence encoded by exon 5 of Ambn. Due to the IDP character of Ambn to form oligomers, protein purification is subject to many challenges. Human ameloblastin (AMBN) and its two isoforms, I and II have already been purified as a recombinant protein in a bacterial expression system and functionally characterized in vitro. However, here we present a new purification protocol for the production of native AMBN in its original formation as a homooligomeric heterogeneous IDP. The purification process consists of three chromatographic steps utilizing His-tag and Twin Strep-tag affinity chromatography, along with size exclusion and reverse affinity chromatography. The presented workflow offers the production of AMBN in sufficient yield for in vitro protein characterizations and can be used to produce both AMBN isoforms I and II.
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Affiliation(s)
- V Vetyskova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo Namesti 2, 16000, Prague, Czech Republic; Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technicka 5, 166 28, Prague, Czech Republic
| | - M Zouharova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo Namesti 2, 16000, Prague, Czech Republic; Second Faculty of Medicine, Charles University, 150 06, Prague 5, V Uvalu 84, Czech Republic
| | - K Bousova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo Namesti 2, 16000, Prague, Czech Republic.
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Abstract
Biomineralization of enamel, dentin, and bone involves the deposition of apatite mineral crystals within an organic matrix. Bone and teeth are classic examples of biomaterials with unique biomechanical properties that are crucial to their function. The collagen-based apatite mineralization and the important function of noncollagenous proteins are similar in dentin and bone; however, enamel is formed in a unique amelogenin-containing protein matrix. While the structure and organic composition of enamel are different from those of dentin and bone, the principal molecular mechanisms of protein-protein interactions, protein self-assembly, and control of crystallization events by the organic matrix are common among these apatite-containing tissues. This review briefly summarizes enamel and dentin matrix components and their interactions with other extracellular matrix components and calcium ions in mediating the mineralization process. We highlight the crystallization events that are controlled by the protein matrix and their interactions in the extracellular matrix during enamel and dentin biomineralization. Strategies for peptide-inspired biomimetic growth of tooth enamel and bioinspired mineralization of collagen to stimulate repair of demineralized dentin and bone tissue engineering are also addressed.
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Affiliation(s)
- J Moradian-Oldak
- Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA
| | - A George
- Brodie Tooth Development Genetics & Regenerative Medicine Research Laboratory, Department of Oral Biology, University of Illinois at Chicago, Chicago, IL, USA
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Qin W, Wan QQ, Ma YX, Wang CY, Wan MC, Ma S, Wang YR, Wang WR, Gu JT, Tay FR, Niu LN. Manifestation and Mechanisms of Abnormal Mineralization in Teeth. ACS Biomater Sci Eng 2021; 9:1733-1756. [PMID: 34436861 DOI: 10.1021/acsbiomaterials.1c00592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tooth biomineralization is a dynamic and complicated process influenced by local and systemic factors. Abnormal mineralization in teeth occurs when factors related to physiologic mineralization are altered during tooth formation and after tooth maturation, resulting in microscopic and macroscopic manifestations. The present Review provides timely information on the mechanisms and structural alterations of different forms of pathological tooth mineralization. A comprehensive study of these alterations benefits diagnosis and biomimetic treatment of abnormal mineralization in patients.
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Affiliation(s)
- Wen Qin
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Qian-Qian Wan
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Yu-Xuan Ma
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Chen-Yu Wang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Mei-Chen Wan
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Sai Ma
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Yi-Rong Wang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Wan-Rong Wang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Jun-Ting Gu
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
| | - Franklin R Tay
- College of Graduate Studies, Augusta University, Augusta, Georgia 30912, United States
| | - Li-Na Niu
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P. R. China
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