Allison Dooley and Nick Coller discuss the importance of remineralisation and demineralisation in the caries process
Dental caries is a complex, multifactorial process affecting the teeth that is caused by the progression of demineralization and remineralization. Although dental caries is preventable, it remains the most common chronic disease in children and is a worldwide epidemic, second only to the common cold. In the oral environment, there is a physiological equilibrium between demineralization and remineralization. Lesion progression or reversal depends upon the steadiness between demineralization, favoring pathological factors (cariogenic bacteria, fermentable carbohydrates, salivary dysfunction), and protective factors (antibacterial agents, sufficient saliva, remineralization) that tips the balance toward remineralization. As acids from cariogenic bacteria increase, the balance angles toward demineralization and net mineral loss, eventually leading to dental caries.
Preventing dental caries
In caries prevention, factors in the oral cavity must be favourable for remineralisation, which include adequate secretion of saliva and limiting frequency of sucrose consumption. Sticky foods are more harmful than non-sticky foods because they remain on the teeth. Good oral hygiene, which consists of brushing twice a day and interdental cleaning daily, in addition to regular professional hygiene appointments, is necessary to prevent dental caries. The scientific evidence recommends key techniques and topical agents for the remineralisation process.
Demineralisation process
The process of demineralisation and caries formation begins when the bacteria convert dietary carbohydrates (especially sucrose) into acids through glycolysis. Streptococcus mutans and lactobacillus are the primary microorganisms that are contributing factors in this process. Acids released by the microorganisms lower the pH of the biofilm to 5.5 (critical pH), allowing minerals to be lost from the enamel. At this pH, the saliva and plaque are no longer saturated with calcium and phosphate. This allows hydroxyapatite to dissolve. Caries lesions develop in the subsurface due to nature of the lesion’s surface. Crystals at the tooth surface are more resistant to demineralisation, leaving subsurface crystals more susceptible to undersaturation conditions as hydrogen ions diffuse from the plaque. The surface layer has better saturation conditions because of access to ions coming from the body of the lesion, plaque and saliva and also covered by the salivary pellicle, which acts as a diffusion barrier slowing down the outward diffusion of ions. The demineralisation process is not linear, however, continued cavitation eventually occurs.
Remineralisation process
The process of remineralisation is the replacement of lost minerals in hard dental tissues that can halt, slow or even reverse the caries process. The remineralisation process is a natural repair mechanism that occurs under neutral pH conditions (7.0). The buffering capacity of saliva plays a critical role in helping restore the neutral pH at the tooth surface. Usually between meals, the pH returns to higher than the critical pH, demineralisation is arrested, and calcium and phosphate mineral ions are redeposited within the carious lesion. This process forms hydroxyapatite (HAP) crystals, which are larger and more resistant to the acid attacks of demineralisation. Saliva is the primary component in caries prevention and neutralises acids formed by plaque bacteria.
Saliva naturally contains the necessary calcium and phosphate ions for preventing demineralisation and allowing remineralisation to occur. Many systemic diseases and medications contribute to hyposalivation, or xerostomia, that disrupt the balance between demineralisation and remineralisation. Natural remineralisation is often insufficient for the majority of white spot lesions when saliva is compromised. The recommendation of nutritional counselling and the use of topical agents is important.
Gold standard
Fluoride treatment, the gold standard, is a valuable technique used in caries prevention. Fluoride enhances the remineralisation process when the ions of calcium and phosphate recombine to form a strong crystal. When applied in low concentrations, fluoride increases the rate of growth and the size of enamel crystals. The accelerated rebuilding of the enamel crystals within the demineralised caries lesion initiates the remineralisation that can reverse the progression of dental caries.
There is a need for remineralisation technologies and topical agents that are able to complement fluoride in products. Combining fluoride with calcium and phosphate makes enamel more resistant to acid demineralisation than its previous state. This results in a reversal of the caries process, creating an enamel surface that is more resistant to dental caries. Scientific research on this promising combination is evolving and will continue for many years to come. Prevention of dental caries is ideal; although, effective communication and goal setting in caries-reducing techniques will lead to positive patient experiences and reduce dental caries.
Regenerative therapies
Curodont (Credentis) can self-assemble into a three-dimensional biomatrix formed from naturally occurring amino acids. This matrix exhibits a high affinity for hydroxyapatite, which allows crystallization and crystal growth of calcium phosphate. The matrix also serves as a crystallization nucleus for new hydroxyapatite crystals and, thus, as a template for new enamel.
MI Paste contains a casein phosphopeptide-amorphous calcium phosphate complex, naturally derived from milk, that releases calcium and phosphate ions to prevent caries by remineralization. When the MI Paste is applied to the teeth, it binds with existing bacteria, plaque and connective tissue to release calcium and phosphate, that support the remineralization process. Curodont and MI Paste regenerative therapies also buffer acids produced by plaque and bacteria, protect and rebuild the surface of the tooth and decrease tooth hypersensitivity.
Conclusion Dental caries is an infectious, transmissible bacterial disease. The use of regenerative therapies is recommended for the multifactorial disease process of demineralisation and dental caries that can be slowed or stopped before more extensive treatment becomes necessary.
References
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Article by Allison Dooley, RDH, ADT, MHS and Nick Coller, MA, Diploma in Dental Hygiene and Therapy
Source: Clinical Dentistry Magazine, March 2021