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Article http://pubs.acs.org/journal/acsodf
Physicochemical and Antibacterial Characterization of a Novel Fluorapatite Coating Ahmed Alhilou,†,‡ Thuy Do,‡ Laith Mizban,† Brian H. Clarkson,§ David J. Wood,*,† and Maria G. Katsikogianni*,†,∥ †
Biomaterials and Tissue Engineering Research Group and ‡Microbiology and Cell Biology Research Group, School of Dentistry, University of Leeds, Clarendon Way, Leeds LS2 9LU, West Yorkshire, U.K. § Cariology, Restorative Sciences, and Endodontics, School of Dentistry, University of Michigan, Ann Arbor 48109-1078, United States ∥ Advanced Materials Engineering, Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, U.K. S Supporting Information *
ABSTRACT: Peri-implantitis remains the major impediment to the long-term use of dental implants. With increasing concern over the growth in antibiotic resistance, there is considerable interest in the preparation of antimicrobial dental implant coatings that also induce osseointegration. One such potential coating material is fluorapatite (FA). The aim of this study was to relate the antibacterial effectiveness of FA coatings against pathogens implicated in peri-implantitis to the physicochemical properties of the coating. Ordered and disordered FA coatings were produced on the under and upper surfaces of stainless steel (SS) discs, respectively, using a hydrothermal method. Surface charge, surface roughness, wettability, and fluoride release were measured for each coating. Surface chemistry was assessed using X-ray photoelectron spectroscopy and FA crystallinity using X-ray diffraction. Antibacterial activity against periodontopathogens was assessed in vitro using viable counts, confocal microscopy, and scanning electron microscopy (SEM). SEM showed that the hydrothermal method produced FA coatings that were predominately aligned perpendicular to the SS substrate or disordered FA coatings consisting of randomly aligned rodlike crystals. Both FA coatings significantly reduced the growth of all examined bacterial strains in comparison to the control. The FA coatings, especially the disordered ones, presented significantly lower charge, greater roughness, and higher area when compared to the control, enhancing bacteria−material interactions and therefore bacterial deactivation by fluoride ions. The ordered FA layer reduced not only bacterial viability but adhesion too. The ordered FA crystals produced as a potential novel implant coating showed significant antibacterial activity against bacteria implicated in peri-implantitis, which could be explained by a detailed understanding of their physicochemical properties. bone in the tissues surrounding an implant.”5,6 Recent data have shown that peri-implantitis affects 20% of patients and 10% of implant sites,7 making it a serious challenge in longterm implant dentistry. This condition that causes progressive bone loss could eventually lead to severe disfigurement and poor aesthetics, which is extremely challenging to manage and treat.8 Bacterial adhesion and biofilm formation on the implant surface are the essential initial steps in the pathogenesis of periimplant disease and the primary etiological factor of implant failure.9 Various anaerobic bacteria, including Porphyromonas gingivalis (P. gingivalis), Fusobacterium nucleatum (F. nucleatum),
1. INTRODUCTION Tooth loss is a significant event that can have a detrimental impact on an individual’s well-being and social life. Osseointegrated dental implants are an increasingly viable and successful treatment option for restoring edentulous spaces, demonstrating success rates of up to 96.8%.1−3 Worldwide, it is estimated that one million endosseous dental implants are placed per year and around 110 manufacturers produce over 440 implant brands.4 It should be noted, however, that clinical complications or failures do occur, and this poses a challenge to both the clinician, in terms of management, and the patient. Implant failure refers to the disruption between the mineralized bone and the implant. The causative factors include chronic bacterial infection known as peri-implantitis, which is defined as “an inflammatory reaction in the oral cavity with loss of supporting © 2016 American Chemical Society
Received: June 16, 2016 Accepted: August 1, 2016 Published: August 26, 2016 264
DOI: 10.1021/acsomega.6b00080 ACS Omega 2016, 1, 264−276
ACS Omega
Article
and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), have been shown to be implicated in periimplantitis.10,11 Because of the growing development of bacterial resistance to antibiotics, there is a considerable interest in the preparation of antimicrobial materials.12TherTherefore, there is great interest in developing an antimicrobial biomimetic implant surface that could prevent bacterial colonization from the outset. Bioceramics and metals have been of particular interest to researchers. Hydroxyapatite (HA) has long been investigated and, as a result, is the most widely used bioceramic in medicine and dentistry because of its strong affinity to bone tissue. This property improves the implant−bone interface and thus favors early osseointegration.13−15 HA, however, does not possess antimicrobial properties, and its use has declined after reports of HA coating delamination from oral implants, resulting in poor performance and uncertain long-term success.16 As a result of these limitations, fluoride-containing apatite coatings have become an area of interest. Chen et al. (2006) successfully synthesized fluorapatite (FA) crystals that resembled enamel prismlike structures, using the hydrothermal technique. The advantage of these FA microrods is that their composition is similar to the apatite crystals found in dental hard tissues.17 FA demonstrates better biocompatibility and bioactivity when compared with HA.18−20 This bioceramic also exhibits lower resorption rates in situ21 and has the potential to release fluoride ions, which have osteoinductive22 and antibacterial properties.23 Indeed, FA has been shown to improve the rate of bone apposition in early osteogenesis.24 These promising findings suggest that FA implant coatings may be clinically advantageous and have led to an increased interest in the application of FA as a dental implant coating. However, current research regarding this material is not comprehensive.25 For instance, there are controversies as to whether partially fluorinesubstituted hydroxyapatite (FHA; Ca10(PO4)6(OH)2−2xF2x, 0
Article http://pubs.acs.org/journal/acsodf
Physicochemical and Antibacterial Characterization of a Novel Fluorapatite Coating Ahmed Alhilou,†,‡ Thuy Do,‡ Laith Mizban,† Brian H. Clarkson,§ David J. Wood,*,† and Maria G. Katsikogianni*,†,∥ †
Biomaterials and Tissue Engineering Research Group and ‡Microbiology and Cell Biology Research Group, School of Dentistry, University of Leeds, Clarendon Way, Leeds LS2 9LU, West Yorkshire, U.K. § Cariology, Restorative Sciences, and Endodontics, School of Dentistry, University of Michigan, Ann Arbor 48109-1078, United States ∥ Advanced Materials Engineering, Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, U.K. S Supporting Information *
ABSTRACT: Peri-implantitis remains the major impediment to the long-term use of dental implants. With increasing concern over the growth in antibiotic resistance, there is considerable interest in the preparation of antimicrobial dental implant coatings that also induce osseointegration. One such potential coating material is fluorapatite (FA). The aim of this study was to relate the antibacterial effectiveness of FA coatings against pathogens implicated in peri-implantitis to the physicochemical properties of the coating. Ordered and disordered FA coatings were produced on the under and upper surfaces of stainless steel (SS) discs, respectively, using a hydrothermal method. Surface charge, surface roughness, wettability, and fluoride release were measured for each coating. Surface chemistry was assessed using X-ray photoelectron spectroscopy and FA crystallinity using X-ray diffraction. Antibacterial activity against periodontopathogens was assessed in vitro using viable counts, confocal microscopy, and scanning electron microscopy (SEM). SEM showed that the hydrothermal method produced FA coatings that were predominately aligned perpendicular to the SS substrate or disordered FA coatings consisting of randomly aligned rodlike crystals. Both FA coatings significantly reduced the growth of all examined bacterial strains in comparison to the control. The FA coatings, especially the disordered ones, presented significantly lower charge, greater roughness, and higher area when compared to the control, enhancing bacteria−material interactions and therefore bacterial deactivation by fluoride ions. The ordered FA layer reduced not only bacterial viability but adhesion too. The ordered FA crystals produced as a potential novel implant coating showed significant antibacterial activity against bacteria implicated in peri-implantitis, which could be explained by a detailed understanding of their physicochemical properties. bone in the tissues surrounding an implant.”5,6 Recent data have shown that peri-implantitis affects 20% of patients and 10% of implant sites,7 making it a serious challenge in longterm implant dentistry. This condition that causes progressive bone loss could eventually lead to severe disfigurement and poor aesthetics, which is extremely challenging to manage and treat.8 Bacterial adhesion and biofilm formation on the implant surface are the essential initial steps in the pathogenesis of periimplant disease and the primary etiological factor of implant failure.9 Various anaerobic bacteria, including Porphyromonas gingivalis (P. gingivalis), Fusobacterium nucleatum (F. nucleatum),
1. INTRODUCTION Tooth loss is a significant event that can have a detrimental impact on an individual’s well-being and social life. Osseointegrated dental implants are an increasingly viable and successful treatment option for restoring edentulous spaces, demonstrating success rates of up to 96.8%.1−3 Worldwide, it is estimated that one million endosseous dental implants are placed per year and around 110 manufacturers produce over 440 implant brands.4 It should be noted, however, that clinical complications or failures do occur, and this poses a challenge to both the clinician, in terms of management, and the patient. Implant failure refers to the disruption between the mineralized bone and the implant. The causative factors include chronic bacterial infection known as peri-implantitis, which is defined as “an inflammatory reaction in the oral cavity with loss of supporting © 2016 American Chemical Society
Received: June 16, 2016 Accepted: August 1, 2016 Published: August 26, 2016 264
DOI: 10.1021/acsomega.6b00080 ACS Omega 2016, 1, 264−276
ACS Omega
Article
and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), have been shown to be implicated in periimplantitis.10,11 Because of the growing development of bacterial resistance to antibiotics, there is a considerable interest in the preparation of antimicrobial materials.12TherTherefore, there is great interest in developing an antimicrobial biomimetic implant surface that could prevent bacterial colonization from the outset. Bioceramics and metals have been of particular interest to researchers. Hydroxyapatite (HA) has long been investigated and, as a result, is the most widely used bioceramic in medicine and dentistry because of its strong affinity to bone tissue. This property improves the implant−bone interface and thus favors early osseointegration.13−15 HA, however, does not possess antimicrobial properties, and its use has declined after reports of HA coating delamination from oral implants, resulting in poor performance and uncertain long-term success.16 As a result of these limitations, fluoride-containing apatite coatings have become an area of interest. Chen et al. (2006) successfully synthesized fluorapatite (FA) crystals that resembled enamel prismlike structures, using the hydrothermal technique. The advantage of these FA microrods is that their composition is similar to the apatite crystals found in dental hard tissues.17 FA demonstrates better biocompatibility and bioactivity when compared with HA.18−20 This bioceramic also exhibits lower resorption rates in situ21 and has the potential to release fluoride ions, which have osteoinductive22 and antibacterial properties.23 Indeed, FA has been shown to improve the rate of bone apposition in early osteogenesis.24 These promising findings suggest that FA implant coatings may be clinically advantageous and have led to an increased interest in the application of FA as a dental implant coating. However, current research regarding this material is not comprehensive.25 For instance, there are controversies as to whether partially fluorinesubstituted hydroxyapatite (FHA; Ca10(PO4)6(OH)2−2xF2x, 0
