August 04, 2021
The enamel covering the tooth is the hardest substance in the human body. This layer of hard tissue is capable of withstanding the different acidic changes and biting forces. For a tooth to decay, the enamel has to be broken down first. This is done through a combination of factors that degrade the surface of the enamel. These factors include bacterial accumulation on the tooth surface, consumption of foods that accelerate the degradation, reduction in salivary flow and poor oral hygiene maintenance.
Tooth decay or caries is a gradual process. It involves the tooth losing its mineralized content, becoming porous and eventually becoming susceptible to carious degradation. The first visible sign of a tooth being susceptible to carious lesion is its appearance as a white spot lesion. This chalky white discoloration is what is termed as incipient caries. Incipient literally means to begin to develop or form. In this case, it is the beginning of the development of a carious lesion. However, this stage of tooth decay is the least harmful and the tooth can be reversed to its original surface texture.
The initiation of caries is a result of loss of minerals from the tooth surface. This loss occurs as a result of ionic exchanges that take place between the oral fluids and the surface of the tooth. These exchanges are facilitated by the dietary habits and decrease in the salivary flow rate. When the pH drops and the oral cavity becomes acidic, it welcomes the accumulation of certain bacterial species that favourably grow in these conditions. These bacteria are able to degrade the enamel matrix, and subsequently progress further if untreated.
Dental caries begin as incipient lesions, after which the lesion reaches the dentin (hard tissue under the enamel) and later to the pulp (soft tissue housing blood vessels and nerves) where it becomes painful, necrotic and may invade the surrounding bony tissues. The management of dental caries, irrespective of its extent was initially thought to be removing the carious lesion with the help of the dental drill (airotor) or spoon excavator, and later restoring the tooth with a suitable dental cement. However, microscopic advances have now shown that the incipient lesions do not require such extensive treatments and the tooth can heal itself through remineralizing actions.
"A dentist should become a physician first to understand the oral environment in detail before becoming a surgeon to repair the ultimate damage that may result from the later stages of the disease."
This is exactly what a dentist does before opting for a treatment plan for white spot lesions. Clinically, if the lesion has not progressed to the dentin, that non-invasive approach must be opted for. These treatment modalities aim at remineralizing the affected tooth. Once a diagnosis is confirmed through clinical examination, radiographs and in some cases through transillumination, the dentist then determines the right mineralizing agent depending on the extent of the incipient caries and the number of teeth affected.
Fluoride is commonly used in these cases. When fluoride binds to the tooth surface, it forms fluorapatite, a substance that is highly resistant to caries. In the process, the caries progression also ceases. Another promising agent is the CPP-ACP (casein phosphopeptide-amorphous calcium phosphate). It increases the pH of the lesion, thereby not letting the bacteria to thrive. It has an anti-cariogenic action, where the ACP is localized to a tooth surface. From here, it acts as a reservoir for constant supply of minerals. Moreover, when combined with fluoride agents, it forms amorphous calcium-fluoride phosphate which shows an even better remineralizing action.
Novamin, containing calcium sodium phosphosilicate is also capable of remineralizing incipient lesions. Newer materials like nano hydroxyapatite, that chemically bind to the tooth surface have ensured that there is no subsequent development of secondary caries. Resin infiltration is also another technique, where the enamel is subjected to acid etching, after which a suitable resin material is added that binds with the created resin tags. This enhances the strength of the tooth and prevents it from being subjected to further decay.
Incipient caries when diagnosed and managed early can be fruitful in avoiding extensive treatment procedures like pulp capping, root canal treatment, etc. A regular 6 month visit to the dentist can help in detecting these lesions early. Remineralization of the teeth is thus targeted when the incipient caries has not progressed to the dentin.