Caries-Preventive Agents Induce Remineralization of Dentin in a Biofilm Model

Abstract

The aim was to study remineralization in dentin underneath a biofilm. This was done in a constant depth film fermentor (CDFF) which was modified so that two treatments can be applied simultaneously in one experiment. Forty-five Streptococcus mutans biofilms were grown in grooves in dentin. Growth medium (3.7 g/l BHI, 1.5 mM calcium and 25 mM PIPES) was administered alternately with 2% sucrose pulsing 4 × 30 min/day. Fluoride at 135 ppm as NaF only or in a mixture with 0.2% chlorhexidine was applied for 2 × 5 min/day. The treatments started 5 days after inoculation and lasted 15 days. Five specimens per group were removed at various time points. The biofilms were checked for viability (by plating) and acid content (by capillary electrophoresis). The dentin specimens were analysed for mineral loss and lesion depth (by transversal microradiography). Fluoride treatment had no effect on the viability but reduced lactic acid production by 75%. The mixture treatment reduced the viability by 80% and the lactic acid content by 93% on the first day and later reduced the two parameters to below the detection limits. Significant differences in changes in mineral loss and lesion depth were observed between the treatment groups. Partial remineralization but deeper lesions were observed in the fluoride group, while nearly complete remineralization was seen in the mixture group. In conclusion, the CDFF S. mutans biofilm model can be used as a de- and remineralization biofilm model, and the split mode is particularly suitable for testing caries-preventive agents.

Evidence of an in vitro Coupled Diffusion Mechanism of Lesion Formation within Microcosm Dental Plaque

“…Biofilms grown in the CDFF have been used to model various response variables implicated in the caries process [Pratten et al, 1998b;Dibdin and Wimpenny, 1999;Wilson, 1999;McLean et al, 2007] including responses to fluoride and sucrose [Embleton et al, 1998;Deng et al, 2005]. However, those biofilms resulting from a microcosm inoculum have yet to be explored.…”

Role of Host-Derived Proteinases in Dentine Caries and Erosion

“…Partial remineralization (especially at the lesion surface) but deeper lesions were observed in the fluoride group, while nearly complete remineralization was seen in the fluoride-CHX group in a biofilm model [Deng et al, 2005]. Even though the significantly better outcome with fluoride-CHX may be caused by the antimicrobial effect of CHX, it is tempting to speculate that CHX may also have contributed to the remineralization process, especially since fluoride also significantly reduced bacterial lactic acid production [Deng et al, 2005]. It should be noted that fluoride alone inhibits MMPs in a dose-response manner , which helps to explain why its action to prevent dentine erosion depends on the maintenance of the DOM [Ganss et al, 2004].…”

“…CHX also inhibits release of the non-collagenous proteins decorin, biglycan and dentine sialoprotein from the demineralized dentine matrix by MMP-3 [Khaddam et al, 2014], which might contribute to the remineralization seen with CHX. Partial remineralization (especially at the lesion surface) but deeper lesions were observed in the fluoride group, while nearly complete remineralization was seen in the fluoride-CHX group in a biofilm model [Deng et al, 2005]. Even though the significantly better outcome with fluoride-CHX may be caused by the antimicrobial effect of CHX, it is tempting to speculate that CHX may also have contributed to the remineralization process, especially since fluoride also significantly reduced bacterial lactic acid production [Deng et al, 2005].…”

Relationship between Gap Size and Dentine Secondary Caries Formation Assessed in a Microcosm Biofilm Model

“…A CDFF was used to grow microcosm biofilms as described elsewhere [Deng and ten Cate, 2004;Deng et al, 2005]. Briefly, the CDFF consists of a glass vessel with a stainless-steel end-plate, with ports for the entry of medium (defined medium mucin, DMM [Wong and Sissons, 2001]), sucrose (10%, 8 !…”

“…DMM = Defined medium mucin; TMR = transverse microradiography. over 180° and reverse, separating composite restored discs from GI discs, as described by Deng et al [2005]. After this separation, the CDFF ran for 14 days more (whole experiment duration 18 days) under the same regimen of sucrose exposure and medium refreshment.…”