Preventing and arresting caries with anti-caries agents using artificial caries models

Abstract

Several demineralisation-remineralisation models simulating the cariogenic challenges have been developed for cariology research. This study started with a literature review to provide an overview of the mechanistic studies on de-/re-mineralisation for cariology research. The review found that most mechanistic studies were studies in vitro using chemical models and microbial culture models. Although the chemical models are generally basic, they are mostly inexpensive, efficient, reproducible and stable. Apart from chemical models, microbial models are also common. They involved cariogenic bacteria, which is a critical and essential factor in aetiology of caries formation. Microbial models also allow a controllable and constant environmental condition of the study. The second review was performed to investigate the dental plaque biofilm and laboratory microbial models used in cariology. Enamel erosion can occur in the demineralisation process in in vitro studies. To prevent unwanted enamel erosion, the effects of fluoride on two common chemical cariogenic models were investigated in the first laboratory study. The results of the study indicated that the chemical cariogenic model using an acetate buffer solution created a deeper subsurface demineralised zone on enamel than the lactate buffer solution model did. An acetate buffer can cause erosion on the enamel surface, which can be prevented by adding a low concentration of fluoride. Hence, the following laboratory study used the acetate buffer solution with fluoride to create artificial caries. The second laboratory study evaluated the enhanced remineralising effect of 38% silver diamine fluoride (SDF) solution by adding 5% sodium fluoride (NaF) varnish on artificial caries lesion on enamel using a chemical model. The results indicated that the combination of SDF and NaF had similar resistance to demineralisation compared with SDF alone on enamel caries. The third laboratory study investigated the remineralising and antibacterial effect of the combination of SDF solution and NaF varnish on artificial dentine caries lesions using a microbial culture model. This study found that dentine caries treated with SDF with or without sodium fluoride had similar resistance to demineralisation, but SDF alone had stronger biofilm growth-inhibiting effect than SDF with sodium fluoride. Therefore, the recommendation to apply sodium fluoride varnish on top of SDF on caries lesion was not supported according to the results of second and third laboratory studies. As an alternative treatment to SDF, silver nitrate solution followed by NaF varnish had a similar effect as SDF on arresting dentine caries. Functionalized tricalcium phosphate (fTCP) was introduced into the NaF varnish to improve the remineralising effect of sodium fluoride. The fourth laboratory study investigated the bacterial inhibition effect and remineralising effect of silver nitrate and NaF with fTCP using a microbial culture model. The results of this study revealed that silver nitrate and NaF with fTCP reduced the progress of artificial dentine caries by cariogenic biofilm. Furthermore, the addition of NaF with fTCP had no impact on the antibacterial effect of silver nitrate.