MANY PERSONS expressed surprise to learn, at a recent lecture I presented, that harmful oral habits can significantly impact on a person, to the extent that the damage can be permanent. Similarly, there could be change in the facial appearance of a person when some harmful habits are practised during the individual’s formative years, although there are many dental problems which have strong genetic influence.
In dentistry, numerous differences in the dento-facial characteristics of individuals are encountered, so that one is often moved to wonder whether oral health, as a condition, is inherited. Even within a family, some members have a high prevalence of dental caries, while others may be caries-free. Such observations make it difficult to answer the question on the hereditary basis of oral disease.
Regardless of abnormal or normal individual states, how do these differences come about? To deal with this question, it is necessary to turn to genetics. When we examine a specific characteristic or disease in the oral region, we often find it in the consequence of two principal factors: Genetic and environmental.
Both ABO blood type and hemophilia are solely determined by the action of genes, and no environmental factors are involved. Conversely, diseases like cholera and AIDS can infect anyone, regardless of their genetic makeup. Asthma, however, is an example of a disease thought to have a genetic basis, but which requires certain environmental factors, such as climatic conditions and pollens, for induction.
Likewise, the size and shape of teeth and different degrees of susceptibility to tooth decay depend on both genetic and environmental factors. Common diseases such as dental caries and periodontal (gum) disease are infectious in nature, because the germ responsible for tooth decay can be transmitted from one person’s mouth to another. However, the problems are often considered to be mainly environmental. But even this being the case, researchers are convinced that the genetic aspects that influence the degree of susceptibility should not be overlooked.
The basic element in genetics is the gene. It is found in the nucleus of every cell. A body containing many genes is a chromosome. Humans have 46 chromosomes in each cell. Chromosomes are made in pairs, which closely resemble each other. There are 23 such pairs, of which one pair concerns sex. One set of chromosomes comes from one of either parent. Each of the thousands of genes is responsible for a specific attribute. For example, there is a gene for the colour of the eyes, one for the shape of the nose, one for the colour of the skin etc. Environmental factors may alter the composition of genes, which, when it occurs, is known as mutation. Cancer is a classic example of a condition caused by a gene mutation which was triggered by an external agent.
After the alteration occurs in a gene, the change will be transmitted to descendants, and that is why there may be certain conditions, such as heart disease and diabetes, that tend to perpetuate in families.
There are many dental and maxillo-facial diseases that are mainly transmitted along genetic lines. During the years of my experience working at the Department of Oral and Maxillo-facial surgery, I can readily cite two common examples: Facial keloid (abnormal proliferation of scar tissue) is seen almost exclusively in Afro-Guyanese, and cleft lip/palate almost exclusively in Indo-Guyanese.
So, the next time one wonders how come they brush and floss often and still they have cavities, they can consider that the problem may have been inherited from a parent.