Surface treatments of titanium dental implants for rapid osseointegration

Background: From an ecological viewpoint, the oral cavity, in fact the oro-pharynx, is an ‘open growth system’. It undergoes an uninterrupted introduction and removal of both microorganisms and nutrients. In order to survive within the oro-pharyngeal area, bacteria need to adhere either to the soft or hard tissues in order to resist shear forces. The fast turn-over of the oral lining epithelia (shedding 3 ×/day) is an efficient defence mechanism as it prevents the accumulation of large masses of microorganisms. Teeth, dentures, or endosseous implants, however, providing non-shedding surfaces, allow the formation of thick biofilms. In general, the established biofilm maintains an equilibrium with the host. An uncontrolled accumulation and/or metabolism of bacteria on the hard surfaces forms, however, the primary cause of dental caries, gingivitis, periodontitis, peri-implantitis, and stomatitis.

Objectives: This systematic review aimed to evaluate critically the impact of surface characteristics (free energy, roughness, chemistry) on the de novo biofilm formation, especially in the supragingival and to a lesser extent in the subgingival areas.

Methods: An electronic Medline search (from 1966 until July 2005) was conducted applying the following search items: ‘biofilm formation and dental/oral implants/surface characteristics’, ‘surface characteristics and implants’, ‘biofilm formation and oral’, ‘plaque/biofilm and roughness’, ‘plaque/biofilm and surface free energy’, and ‘plaque formation and implants’. Only clinical studies within the oro-pharyngeal area were included.

Results: From a series of split-mouth studies, it could be concluded that both an increase in surface roughness above the Ra threshold of 0.2 μm and/or of the surface-free energy facilitates biofilm formation on restorative materials. When both surface characteristics interact with each other, surface roughness was found to be predominant. The biofilm formation is also influenced by the type (chemical composition) of biomaterial or the type of coating. Direct comparisons in biofilm formation on different transmucosal implant surfaces are scars.

Conclusions: Extrapolation of data from studies on different restorative materials seems to indicate that transmucosal implant surfaces with a higher surface roughness/surface free energy facilitate biofilm formation.

Effect of material characteristics and/or surface topography on biofilm development

Restriction digestion fragments of DNAs extracted from 14 representative strains of Saccharomonospora azurea, “Saccharomonospora caesia,” Saccharomonospora cyanea, Saccharomonospora glauca, and Saccharomonospora viridis and six “Saccharomonospora”-like isolates were separated by electrophoresis, Southern blotted onto nylon membranes, and hybridized by using two rRNA gene probes cloned from Streptomyces griseus subsp. griseus KCTC 9080. The following four restriction endonucleases were used: Bam HI, Sal I, Pvu II, and Xho I. The resultant five ribotype patterns were considered species specific. The genomic diversity revealed by ribotyping indicates that this method can be used to both characterize and identify saccharomonosporae. All of the test strains contained DNA with three rRNA gene clusters.

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Identification of Saccharomonospora strains by the use of genomic DNA fragments and rRNA gene probes

Adhesion of microbes, such as bacteria and fungi, to surfaces and the subsequent formation of biofilms cause multidrug-tolerant infections in humans and fouling of medical devices. To address these challenges, it is important to understand how material properties affect microbe-surface interactions and engineer better nonfouling materials. Here we review the recent progresses in this field and discuss the main challenges and opportunities. In particular, we focus on bacterial biofilms and review the effects of surface energy, charge, topography, and stiffness of substratum material on bacterial adhesion. We summarize how these surface properties influence oral biofilm formation, and we discuss the important findings from nondental systems that have potential applications in dental medicine.

Effects of Material Properties on Bacterial Adhesion and Biofilm Formation

Understanding cytokine immunobiology is central to the development of rational therapies for destructive inflammatory diseases such as rheumatoid arthritis (RA) and periodontitis. The classical interleukin-1 (IL-1) family cytokines, IL-1alpha and IL-1beta, as well as IL-18, play key roles in inflammation. Recently, other members of the IL-1 family have been identified. These include six cytokines whose genes are located downstream of the genes for IL-1alpha and IL-1beta on chromosome 2 (IL-1F5-10) and also IL-33, which is the ligand for ST2, a member of the IL-1R/Toll-like receptor (TLR) receptor superfamily. IL-1F6, IL-1F8 and Il-1F9 are agonists and, along with their receptor IL-1Rrp2, are highly expressed in epithelial cells suggesting a role in immune defence in the skin and the gastrointestinal (GI) tract including the mouth. Synovial fibroblasts and articular chondrocytes also express IL-1Rrp2 and respond to IL-1F8, indicating a possible role in RA. IL-33 is associated with endothelial cells in the inflamed tissues of patients with RA and Crohn's disease, where it is a nuclear factor which regulates transcription. IL-33 is also an extracellular cytokine: it induces the expression of T helper 2 (Th2) cytokines in vitro and in vivo as well as histopathological changes in the lungs and GI tract of mice. Therapeutic agents which modify IL-1 cytokines (e.g. recombinant IL-1Ra) have been used clinically and others are at various stages of development (e.g. anti-IL-18 antibodies). This review highlights the emerging data on these novel IL-1 cytokines and assesses their possible role in the pathogenesis and therapy of destructive inflammatory disorders such as RA and periodontitis.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2249.2007.03441.x

The expanding family of interleukin-1 cytokines and their role in destructive inflammatory disorders

Surface free energy and bacterial retention to saliva-coated dental implant materials--an in vitro study.

Periodontal disease and inflammatory dermatoses, such as psoriasis, are characterized by the accumulation of dense inflammatory infiltrates immediately beneath the epithelial cell layer of the gingiva and skin, respectively. Dermatologists are increasingly aware that the epidermal keratinocyte probably contributes to inflammatory disease progression by secreting a number of pro-inflammatory cytokines and expressing various adhesion molecules. In psoriatic lesions, it is now believed that epidermal keratinocytes may also act as antigen-presenting cells and participate directly in the superantigenic activation of T-cell clones, some of which may initiate, contribute to, or maintain the disease process. Although the role of the host response in periodontal disease has been extensively studied over the years, very little is known about the contribution of the gingival keratinocyte to the inflammatory response. The available published information is discussed in this review, and we suggest that, like its epidermal counterpart, the gingival keratinocyte may participate actively in the pathogenesis of periodontal disease.

Jean-Jacques Morrier

Papers

Surface free energy and bacterial retention to saliva-coated dental implant materials--an in vitro study.

Interactions Between Non-Immune Host Cells and the Immune System During Periodontal Disease: Role of the Gingival Keratinocyte:

Antimicrobial activity of Ca(OH)2 dental cements: an in vitro study.

Automatic enumeration of adherent streptococci or actinomyces on dental alloy by fluorescence image analysis.

Strategies for rehabilitation in the treatment of dentinogenesis imperfecta in a child: A clinical report