Physicochemical and Antibacterial Characterisation of a Novel Fluorapatite Coating

Peri-implantitis remains the major impediment to the long-term use of dental

implants. With increasing concern over growing 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 surface 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 by X-ray

photoelectron spectroscopy and FA crystallinity by X-ray diffraction. Antibacterial

activity against periodontopathogens was assessed in vitro using viable counts,

confocal and scanning electron (SEM) microscopies. SEM showed that the

hydrothermal method produced FA coatings predominately aligned perpendicular to

the SS substrate or disordered FA coatings consisting of randomly aligned rod-like

crystals. Both FA coatings significantly reduced the growth of all the examined

bacterial strains in comparison to the control. The FA coatings, and especially the

disordered ones, presented significantly lower charge, higher roughness and 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. 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.