Overview

Almost everyone will experience some form of tooth decay, also known as dental caries or cavities, in their lifetime. According to the World Health Organization (WHO), tooth decay is one of the most common chronic diseases worldwide. Tooth decay results from the destruction of the hard surfaces of teeth caused by acid produced by bacteria, leading to cavities and tooth damage.¹ This condition can cause pain, discomfort, and a lower quality of life, making eating and speaking properly difficult.² 

Although proper oral hygiene, a healthy diet, and adequate fluoride are the most common ways to prevent tooth decay, sometimes, those are not enough. Genetics also play a significant role in dental health and can explain why some people are more prone to tooth decay than others. 

Understanding if someone has a genetic predisposition for a disease can help prevent or detect it earlier. If someone has symptoms, knowing their genetic profile can predict future health outcomes and guide treatment. This article explores how genes influence the risk of tooth decay and considers their potential impact on treatment approaches.

Why do teeth decay?

Tooth decay is mainly caused by bacteria naturally found in our mouths. These bacteria form communities on the tooth surface, creating a soft, white film called dental plaque. Plaque bacteria get nutrients from saliva, food, and each other. Consuming sugar regularly disrupts these communities and promotes the growth of bacteria that thrive on sugar. These bacteria produce acids that dissolve the tooth's enamel by erosion/demineralisation, which leads to cavities eventually. If left untreated, tooth decay can cause pain, infection, and tooth loss.¹

Several risk factors contribute to tooth decay, including:

• Diet: The frequent consumption of sticky foods and drinks high in sugars, like milk, ice cream, candy, chips, and sugary beverages, promotes bacterial acid production that attacks and wears down teeth
• Poor oral hygiene: Not brushing teeth soon after eating or drinking can allow plaque to form quickly, leading to decay and gingivitis
• Lack of fluoride: Fluoride helps prevent and reverse early tooth damage. It's found in many public water supplies, toothpaste, and mouth rinses, but not usually in bottled water
• Age: Cavities are common in young children, teenagers, and older adults. However, as teeth wear down and gums recede with age, the risk of decay increases
• Tooth location: Decay often occurs in the back teeth (molars and premolars) because they have grooves and multiple roots that trap food and are harder to clean than the front teeth
• Dry mouth: Saliva helps prevent decay by washing away food and plaque. Certain medications, medical conditions, and treatments can reduce saliva production, increasing the risk of cavities
• Heartburn: Acid reflux can bring stomach acid into the mouth, wearing away enamel and increasing the risk of decay
• Eating disorders: Conditions like anorexia and bulimia cause tooth erosion and cavities due to stomach acid from repeated vomiting and reduced saliva production

How genes affect your health

Your genes play a crucial role in determining many aspects of your appearance, like eye colour and height, as well as how your body functions, such as your blood type. Some genes are associated with diseases that may be common in your family history. Additionally, genes can affect how your body responds to infections, medications and treatments, as well as to lifestyle choices, like smoking or alcohol consumption. Understanding how genes are passed down can help explain their influences. 

Our bodies contain cells with 23 pairs of chromosomes, which are inherited from our parents and carry genes that determine traits. Here are some key points about how genes are passed down:³

• Inheritance patterns: Traits are inherited through dominant or recessive genes or via sex chromosomes (X or Y). For example, one defective gene from a parent can cause a dominant trait (e.g., dentinogenesis imperfecta). Both parents must pass on a defective gene for a recessive trait to appear (e.g., cystic fibrosis). Therefore, sex-linked genes on the X or Y chromosomes affect inheritance differently in males and females
• Chromosomal anomalies: Disorders like Down syndrome, caused by chromosomal abnormalities, affect multiple genes and can lead to several physical and developmental issues
• Genes and environment: Many common diseases, including dental problems, result from complex interactions between genes and environmental factors, like diet and stress
• Genotype vs. phenotype: Genes influence traits, however, environmental factors can affect how these traits appear (phenotype). Epigenetics involves changes in gene expression without altering DNA, which influences how genes interact with the environment
• Genetic influence: Twin studies can help estimate the genetic influence on traits by comparing identical and non-identical twins and showing the influence of genetics versus the environment

How can genes affect tooth decay risk?

Genes can influence the likelihood of developing tooth decay by affecting several factors, such as:^4,5

• Taste preferences: The taste receptor 2 member 38 (TAS2R38) gene affects taste preferences, especially for bitter flavours. Variations in this gene can influence a person's preference for sugary foods, which can increase the risk of cavities
• Sugar consumption: The glucose transporter 2 (GLUT2) gene helps regulate sugar intake by sensing glucose levels. Certain variations in the GLUT2 gene are linked to higher sugar consumption, which is a known risk factor for tooth decay
• Enamel strength: Genes involved in enamel formation, such as for proteins enamelin (ENAM) and amelogenin (AMELX), play critical roles in the development and strength of enamel. Variations in these genes can lead to weaker enamel, making teeth more susceptible to decay
• Immune response: Genes like mannose-binding lectin 2 (MBL2) affect the immune system. Variations in the MBL2 gene can alter the effectiveness of mannose-binding lectin, which is a protein that helps protect against infections, including those in the mouth
• Saliva composition: The carbonic anhydrase 6 (CA6) gene influences the pH balance of saliva. Genetic differences in the CA6 gene can affect saliva’s ability to neutralise acids, impacting the likelihood of developing cavities. In addition, genes like aquaporin 5 (AQP5) affect saliva production and composition, which are crucial for protecting teeth from decay
• Oral bacteria: Studies, especially twin studies, show that bacteria in dental plaque are largely influenced by genetics, especially in early life and during the development of primary and secondary teeth. Certain bacteria that are beneficial for oral health, such as Prevotella pallens, Veillonella species, Pasteurellaceae, and Corynebacterium durum, are largely controlled by genetics. These bacteria can help maintain a healthy oral environment^6,7

How significant is the impact of genes on the risk of tooth decay? 

Behaviour and environmental factors play a role in determining the risk of dental decay, regardless of genetic predisposition. Environmental factors, like diet, play an increasing role over time. Archaeological research shows that the diversity of oral bacteria decreased significantly with the advent of agriculture around 10,000 years ago and even more after the Industrial Revolution.^8,9 Both periods introduced more carbohydrate-rich foods into human diets, which would ultimately lead to an increase in decay-causing bacteria like Streptococcus mutans, Streptococcus. sobrinus, and Lactobacillus species, which are major contributors to tooth decay.⁸

Currently, the impact of genetics on cavity risk is not fully understood. While genetic tests for carrier risk hold promise in identifying at-risk individuals before disease onset, they can't reliably predict the risk of oral diseases like dental decay and gum disease. Currently, the most reliable ways to predict cavities are:

• The presence of existing cavities
• Dietary habits 
• Oral hygiene
• Harmful bacteria levels 
• Socioeconomic status
• Oral health awareness

In the future, it is possible that genetic information could improve personalised treatment strategies and reshape how dental decay is managed.³

Summary

Tooth decay is a common issue caused by bacteria in the mouth that feed on sugars and produce acids that damage teeth and create cavities. While good oral hygiene and diet are important for cavity prevention, genetics can also play a role. 

Genes can influence factors like immune response, taste preferences, oral bacteria, and enamel strength, which affects your risk of tooth decay. Understanding genetic predispositions for dental decay may help with early detection and personalised treatments. However, current genetic tests for predicting decay risk are limited, so clinical evaluations are still the main tools for managing and diagnosing oral health effectively.