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

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

Currently, zirconia is widely used in biomedical area as a material for prosthetic devices because of its good mechanical and chemical properties. Largely employed in clinical area for total hip replacement, zirconia ceramics (ZrO(2)) are becoming a prevalent biomaterial in dentistry and dental implantology. Although titanium is used in dental implantology currently, there is a trend to develop new ceramic-based implants as an alternative to monolithic titanium. This article reviews the evolution and development of zirconia through data published between 1963 and January 2008 in English language. Articles were identified via a MEDLINE search using the following keywords: zirconia, zirconia/biocompatibility, zirconia/osseointegration, zirconia/periointegration, zirconia/review, and zirconia/bacterial adhesion or colonization. This review of the literature aims at highlighting and discussing zirconia properties in biological systems for their future use in dental implantology. In conclusion, zirconia with its interesting microstructural properties has been confirmed to be a material of choice for the "new generation" of implants, thanks to its biocompatibility, osseoconductivity, tendency to reduce plaque accumulation, and interaction with soft tissues, which leads to periointegration. However, scientific studies are promptly needed to fulfill gaps like long-term clinical evaluations of "all zirconia implants," currently leading to propose an alternative use of "hybrid systems" (i.e., titanium screw with zirconia collar) and also bacterial colonization of zirconia. Moreover, there is a permanent need for consistent information about topography and chemistry of zirconia allowing easier cross-product comparisons of clinical devices.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/jbm.b.31147

Zirconia: Established facts and perspectives for a biomaterial in dental implantology.

Objectives: The aim of the present in vitro and human in vivo study was twofold: first, to evaluate the initial biofilm formation on different titanium implant surfaces by means of two highly sensitive fluorescent techniques and, second, to correlate these findings to different surface properties.

Materials and methods: In vivo biofilm formation was induced on purely machined (Pt) and on sand-blasted and acid-etched titanium (Prom) specimens, which were mounted buccally on individual splints and worn by six study participants for 12 h. In vitro bacterial adhesion was also investigated after incubation with Streptococcus sanguinis suspension (37°C, 2 h). Adherent bacteria were quantified by the following fluorescence techniques: Resazurin staining in combination with an automated fluorescence reader or live/dead cell labeling and fluorescence microscopy. Surface roughness (Ra) was determined with a perthometer, and surface free energy (SFE) was measured with a goniometer.

Results: Prom showed a significantly higher median Ra (0.95 μm) and a significantly lower median SFE (18.3 mJ/m2) than Pt (Ra=0.15 μm; SFE=39.6 mJ/m2). The in vitro and in vivo tests showed a significantly higher bacterial adhesion to Prom than to Pt, and the initial biofilm formation on Pt corresponded to the circular surface modifications on the machined substratum. Both observations may be attributed to the predominant influence of surface roughness on bacterial adhesion. No significant differences in the percentage of dead cells among all adhering bacteria were found between Prom (23.7%) and Pt (29.1%). Ectopic solitary epithelial cells from the oral mucosa – strongly adhering to the substratum – were found on each Prom specimen, but not on any of the Pt surfaces.

Conclusions: Initial bacterial adhesion to differently textured titanium surfaces is primarily influenced by Ra, whereas the influence of SFE seems to be of only minor importance. Therefore, the micro-structured parts of an implant that are exposed to the oral cavity should be highly polished to prevent plaque accumulation. Both tested fluorometric techniques proved to be highly sensitive and reproducible in the quantification of biofilm formation on titanium implant surfaces.

To cite this article:
Burgers R, Gerlach T, Hahnel S, Schwarz F, Handel G, Gosau M. In vivo and in vitro biofilm formation on two different titanium implant surfaces.
Clin. Oral Impl. Res. 21, 2010; 156–164
doi: 10.1111/j.1600-0501.2009.01815.x

Florence Mabboux

Papers

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