Dental erosion, particularly in the case of bacteria-induced changes in dental materials, is an area where nanoscale surface analysis is of widespread interest. Dental caries is a widespread chronic disease which affects humans and certain animals (1
). The etiology of caries is dependent on several factors, including host susceptibility, intake of carbohydrates and the presence of a bacterial flora capable of acid production. In combination with host behavior, genetic variations, cultural and social variables, caries can develop initiated by the acid induced demineralization of the enamel tooth surface (2
In this study non-contact optical profiling was used to characterize surface demineralization in tooth enamel due to mono-species bacterial biofilm activity. Although several studies have been conducted on the etching process of tooth enamel with demineralization agents using atomic force microscopy (4
), scanning electron microscopy (6
), transmission electron microscopy (9
), x-ray scanning analytical microscopy (10
) and confocal laser scanning microscopy (11
), these techniques often require significant sample preparation, imaging time or vacuum conditions and may cause problems such as charging when using SEM.; however, there has been relatively little analysis of tooth enamel using non-contact optical profilometry. To date one previous study evaluated the protective effect of fluoride components on tooth enamel treated with hydrochloric acid using optical profilometry (12
); however, to our knowledge there is no literature available for analyses of S. mutans
mono-species biofilm induced enamel demineralization using optical profilometry.
Surface metrology using non-contact, optical profilometry has been widely used in recent years for quality control in industry with applications such as data storage, semiconductors, optical telecommunication and MicroElectroMechanical Systems (MEMS) (13
). Optical profiling, or white light interferometry, is a non-destructive, highly sensitive technique typically used for surface characterization and dynamic measurements. With the capability to resolve, repeatedly, large surface areas with sub-nanometer resolution this technique was shown to be a novel complementary technique for applications in the fields of biology and biotechnology.
can be isolated from the healthy human dental bacterial flora (15
). However, under certain circumstances which have not been fully understood, S. mutans
can increase in numbers initiating an ecological shift in the bacterial biofilm composition towards a decrease in diversity (15
). This could lead to the development of dental caries (demineralization and tooth decay). S. mutans
is known to express several virulence traits, including the synthesis of glucan-polymers from dietary sucrose, promoting a relatively firm attachment to the tooth surface (1
). In addition, S. mutans
encodes specific high and low affinity transport systems for carbohydrates, which are used almost exclusively as energy and carbon sources (18
). These transport systems enable S. mutans
to take up several different carbohydrates even if they are present in low concentrations. Subsequently, these carbohydrates are metabolized and one of the end-products is lactic acid, which is excreted into the environment (1
). The lactic acid can cause a decrease in the pH as low as 4 which causes tooth enamel demineralization (20
). Thus, optical profilometry was used to measure nanometer decay in tooth enamel as a result of S. mutans
biofilm exposure and this outcome was compared to chemically induced enamel demineralization by biologically relevant organic acids, lactic acid and citric acid. Data for both surface roughness and surface height from a single study is provided, allowing comparison of the two metrics for surface loss.