How do genetic factors influence oral health

It is widely known that it is not just our appearance that we inherit from our parents, but also an increased risk of diseases and health conditions. While there are thousands of genetic disorders, from diabetes to migraine, we rarely consider dental health as a cause of concern. Ahead of World Oral Health Day, which is celebrated on March 20 every year, we've got Dr Sharon Colaco Dias, Prosthodontist and Implantologist, head of dental medicine at Manipal Hospital in Bangalore to outline how genetic factors influence oral health.

What is the connection between oral health and genetic factors? How can genetic factors affect the size, shape, and colour of your enamel?
The most common oral diseases are dental cavities and gum disease. Almost every aspect of oral health is affected to a degree by your genes. Studies have shown that about 60 per cent of tooth decay appears to involve genetic factors. These genetic factors can change the levels of proteins in the tooth, which can affect the size, shape, and colour of your enamel. Depending on this, the enamel becomes weaker and more susceptible to developing cavities.

Can oral diseases be directly inherited from parents?
Many common diseases are not inherited as a single gene defect, but instead are the result of modifications in gene expression or gene-environment interactions which affects one's body including the oral cavity. Enamel and dentine structure, immune response, salivary content and volume, oral microflora, dental arch morphology (width, length, and shape) and alignment contribute to the multifactorial and complete cause of dental diseases.

Are there any markers that can be identified?
Research studies have concluded that the heredity of our defence response pattern may be an important factor in developing gum diseases. In order to achieve the best results from gum treatment, one must not only be able to identify genetic determinants but also learn to modify, control or modulate the immune response. At present, the clinical application of the effect of genetics on gum disease is minimal.

What are some of the common diseases that may arise from genetic factors?
Dental caries is one of the most fundamental chronic diseases that is influenced by a complex interplay of both genetic and environmental factors. Most of the factors affecting susceptibility to dental caries are influenced by genetics. In addition, genetics accounts for up to 65 per cent of inter-individual variation in dental caries experience. One of the primary genes to have an association with caries susceptibility is amelogenin. Different levels of expression of amelogenin, correlate directly with variable enamel hardness, i.e., an increase in amelogenin is directly proportional to an increase in the hardness of enamel and vice versa.

The hazardous paths of the teeth, jaw development, and dental movement after eruption will contribute to the dental arch details that form due to the influence of genetic, epigenetic, and environmental factors. Genetic factors mostly influence dental arch variation from the primitive stage of organ development. Disturbances in gene interactions will result in abnormalities or variations of dental arch shape and size. The dental arch variation results from a combination of the development of tooth position and jaws. Yet, after the eruption, environmental factors include intraoral functional pressures such tongue pressure, lip and cheek force, and oral habits predominantly affect tooth position (thumb sucking, tongue thrusting, mouth breathing, lip biting). On the other hand, the jaw and alveolar bones as the dental arch base are greatly influenced by genetic and epigenetic factors that have crucial roles in dental arch development.

How are gums affected?
Genetics has influenced gum diseases and also holds a significant role in the predisposition and progressiveness of the condition. At least 50 per cent of the vulnerability of gum disease involving bone loss is attributed to heredity or genetic factors. The role played by genetics to damage the immune response system of our tissues during gum diseases has been proved.

There are two types of gum disease. One occurs in young adults and another type in elderly people. Childhood (early onset) gum disease is often genetic, and the likelihood of inheriting gum disease from families is high, as indicated by genetic studies. This is known as Juvenile periodontitis. Elderly gum disease was thought to have a less genetic influence. But a recent study implies that genetics influences the amount of bone loss and pocket depth in elderly gum disease too. Certain systemic health disorders predispose the patient's susceptibility to acquiring gum disease, which may present clinically in a chronic or aggressive form. For example, Neutrophil defects predispose to rapid and severe bone loss in gum disease. A high susceptibility to developing gum disease with bone loss has been associated with conditions such as Down syndrome (trisomy 21), Chediak-Higashi syndrome and Papillon-Lefevre syndrome.

How is teeth alignment impacted?
The alignment of teeth usually resembles one of the parents. Due to the occlusion the upper and lower teeth fit together (bite). The upper teeth typically cover the lower teeth. Misaligned teeth are called Malocclusion. This can occur because of your difference in jaw shape which could be hereditary which means it runs through families. Jaw shape and size might be inherited from one parent, while teeth size and shape might be inherited from another parent. It can be caused by the difference in the size of the upper and lower jaws or between the jaw and tooth size. It causes teeth overcrowding or abnormal bite patterns which results in difficulty in chewing or biting, hence bacteria can harbour in the nooks and corners created by the overcrowded teeth, increasing the risk of decaying teeth and developing cavities.

Although weak, the available evidence shows that the heritability factors are determinants for the variations within the same arch, namely, arch morphology and crowding. Between the arch variations like cross bite, the deep bite has environmental factors as determinants rather than genetic factors.

Genetics play an important role in dentistry. Whenever it seems necessary, a genetic consultation should be added as part of the dental treatment.

What role does genetics play in determining the amount of saliva produced? How does it help teeth fight off acid erosion?
Genes have an influence on the quality and quantity of saliva produced. Saliva can be thick and mucous (sticky) or thin and clear (non- sticky). This has an impact on the cleansing properties of saliva. If it is thick, it tends to cleanse less and hence has more chances of plaque formation and vice versa. The PH of the saliva is also an important factor that contributes to dental problems. The normal PH of saliva is relatively neutral. Studies have shown that as the saliva becomes acidic there are more chances of having gum disease and dental caries. Most of the time in diabetic patients the saliva is acidic, hence they have more chance of having gum disease than non-diabetic patients.

The genetic variations contribute to changed levels of calcium and phosphorus in saliva which is the key structure of the tooth. Hence when these levels are decreased, the tooth becomes weak and the ability to fight off acid erosion decreases. The genetic variation of enamel formation genes may influence the dynamic interactions between the enamel surface and the oral cavity. For example, a decrease in calcification (chalky enamel) of some teeth like incisor and molar has traditionally been thought to have an environmental cause. However, recent studies suggest that genetic variants might contribute to an individual's risk for this condition.

Also Read: How to help your children prepare for exams, and cope with anxiety and stress