Dental caries in the laboratory: developing a standard testing method for future research in caries prevention

Dental caries has affected humans for millions of years and even today is present in a large portion of the world’s population. There are several factors that can cause tooth decay, but one of the main reasons is sugar consumption. As bacteria inside our oral cavity break down the carbohydrates and sugars we eat, they produce acid that seeps into the grooves and pits of our teeth and cause demineralization of the enamel. Subsequently, the enamel structure and composition is compromised and if left untreated for long enough, caries develop and can affect the dentin and pulpal layers, which contain the nerves and blood vessels, underneath the enamel. Dentists restore dental caries by removing the decayed portions and filling the cavity with amalgam or composite material to mimic the dental anatomy that was present before. Fortunately, caries can be prevented with regular oral hygiene such as brushing and flossing as well as sealants, especially in children, that can prevent pit and fissure caries in the molars. Additionally, saliva acts as a pH buffer in our mouths to reduce the acidity caused by the bacteria and the fluoride in our drinking water and toothpastes assists in the remineralization process. With all the factors involved in dental caries, research is important in broadening our knowledge of the disease. In order to conduct a study on caries, a researcher can choose to create a caries simulation model in a laboratory setting or use patients in a clinic setting. Each method has advantages and disadvantages. Choosing a model can also depend on the research question, budget, or time. The simplest model is the in vitro chemical demineralization model, in which researchers place teeth or slides of enamel or dentin into an acidic gel or solution for a specific time period before measuring the amount of demineralization that has occurred. The advantages of this model are that it is inexpensive, easily reproducible, and studies can be completed within a reasonably short time frame. The in vitro bacterial biofilm model uses several different species of bacteria that are commonly found during biofilm formation process in order to generate the type of acid that would be present in the oral environment. Although the biological in vitro model is more clinically relevant than the chemical in vitro model, one of its main disadvantages is that unlike the chemical in vitro model, there is no way for remineralization to occur because the biofilm cannot be removed and reapplied periodically. In vivo studies are typically conducted on teeth in living patients and are usually the last step used in product testing. In situ studies offer scientists a compromise between in vitro and in vivo studies in regards to its cost, duration, and clinical relevance. In this type of study, patients wear a dental appliance that contains test samples for a predetermined amount of time. The benefit of this design is that researchers have access to an active oral microcosm present in the oral cavity. Typically, clinical trials are carried out after extensive experimentation in the laboratory. In situ studies offer a middle ground between bench and clinical research models. The purpose of this study was to explore the existing models used for caries simulation and determine whether a standardized model can be developed that can be used for future research on dental caries. After reviewing the literature, there was no conclusive evidence that any one model would suffice for all types of experiments. Researchers should continue to use the most appropriate model for their particular study with the in situ model offering a compromise between in vitro and in vivo models