Dental Plaque as a Biofilm: A Pilot Study of the Effects of Nutrients on Plaque pH and Dentin Demineralization

Abstract

Direct or in situ methods (e.g., confocal microscopy, microsensors) are used to study non-oral biofilms for almost two decades, and they have recently been introduced in the research of dental plaque. We combined a pH microsensor technique and transversal microradiography (TMR) in a pilot study where the effects of nutrient availability on plaque acidogenicity and on the development of caries-like lesions were assessed. One volunteer accumulated dental plaque for 7 days in 0.2-mm-wide and 0.8-mm-deep dentin grooves at four conditions: (1) saliva only, (2) 8 × 5 min/day dipping in 10% sucrose solution, (3) 7 × 5 min/day consumption of sweet cookies plus one meal/day, and (4) subject’s regular diet. Plaque pH versus time and depth profiles in the grooves were recorded ex vivo before and after sugar challenge. ‘Saliva’ plaque responded to sugar with slow pH decrease – minimum pH 5.6–5.8 was reached after 30 min, while sugar dipping resulted in metabolically active plaque (minimum pH 5.3–5.5 within 4–8 min). TMR analysis revealed no demineralization after these two periods. Metabolically active plaque leading to distinct lesions resulted from frequent plaque exposure to diets rich in starch and carbohydrates (groups 3 and 4). These findings strengthen the view that the plaque acidogenicity does not necessarily reflect cariogenicity, and that retention of food components may account for increased cariogenicity at plaque retention sites in the mouth.

Real-Time Microsensor Measurement of Local Metabolic Activities in Ex Vivo Dental Biofilms Exposed to Sucrose and Treated with Chlorhexidine

“…After about 10 min a minimal pH value of 4.3 was obtained. The range of pH drop we measured (from pH 7 to between pH 5.5 and 4.3) was in agreement with the results of microelectrode measurements in a dentine groove model reported by other authors (13,53,54). The degree of acidification in the biofilms will be expected to vary between individuals, as a function of both host and bacterial factors such as biofilm thickness, concentration of acidophilic bacteria, and saliva chemistry.…”

“…Consequently, this results in further acid production and a decreasing pH. Associated with this is the demineralization and lesion development of dental hard substance (54).…”

“…Microelectrodes with a tip diameter of a few micrometers offer precisely localized measurements on the microscale in three dimensions under real-time conditions (9,35). Thus far, microelectrodes have been applied for measuring plaque pH in dental research in a groove model ex vivo (53,54) and in in vitro-grown S. mutans biofilms (13,42). However, there is no information on direct measurements of oxygen distribution and consumption in dental biofilms grown in vivo in the human oral cavity.…”

Development of New Software as a Convenient Analysis Method for Dental Microradiography

“…In previous studies 11,12) , a commercially available software was used to calculate the mineral loss (ΔZ) and lesion depth (Ld) of tooth enamel. However, such commercial software is available only at a prohibitive price.…”

Qualitative analysis of re mineralized carious lesions subjected to fluoride supplement through confocal laser scanning microscope

“…Fluoride affects the caries process by enabling the formation of high quality fluorapatite that aids remineralization and inhibits glycolysis of plaque microorganisms [6]. The early attempts to incorporate fluoride into toothpastes which dates back to the 1960s and it is one of the most common and effective modes of topical fluoride delivery [7]. Hence, in the present study a non-fluoridated dentifrice has been used as a control along with two higher concentrations of fluoride, that is 500 ppm and 1000 ppm for comparison.…”