What Causes Tooth Decay and How Can It Be Prevented?

Tooth decay is one of the most common health problems in the world, and it affects not only children but people of every age. Most of us assume that sugar is the sole culprit; in reality, the true determinant is how many times a day the teeth are exposed to acid. When bacterial plaque, sugary foods and time come together, a silent process begins in the tooth enamel — and if it goes unnoticed, it can advance all the way to the innermost layer of the tooth.

In this article we cover how tooth decay forms and which stages it goes through, the factors that pave the way for it, the symptoms at each stage, the ways to prevent it, and which treatments are applied at the clinic depending on the stage; in the final section we answer the most frequently asked questions.

What Is Tooth Decay and How Does It Form?

Tooth decay is a disease that occurs when acids produced by bacteria on the tooth surface dissolve the hard tissues of the tooth. Three components must come together for it to develop: bacterial plaque accumulating on the tooth surface, fermentable carbohydrates (sugar and starch) that these bacteria use as food, and sufficient time. Every time the bacteria in plaque meet sugar, they release acid into the environment; this acid begins to dissolve the calcium and phosphate minerals in the enamel. After each meal, saliva works to neutralise the environment and replace the lost minerals; but if the acid attacks come more often than saliva can repair, the balance tips towards decay.

Decay does not appear all at once; it passes through distinct stages. The first stage is the white spot (initial) lesion, where mineral loss begins on the enamel surface; it appears as a chalky-white, matt patch on the tooth, and at this stage there is not yet a hole. If the process is not stopped, the enamel layer breaks through and enamel decay turns into a small cavity. Once the decay reaches the softer dentine layer beneath the enamel, it progresses much faster; in the final stage it can reach the pulp — the tooth's bundle of vessels and nerves — leading to inflammation and an abscess at the root tip.

This distinction between stages is critically important for treatment. The mineral loss of the white spot stage can be halted, and even partially regained, through a process called remineralisation, supported by fluoride and the reparative effect of saliva. Once a hole (cavitation) has formed in the enamel, however, this tissue cannot renew itself; the lost part must be cleaned and restored by a dentist.

What Causes Tooth Decay?

Although the mechanism of decay is the same in everyone, certain factors speed the process up considerably. The best known is diet; but what matters here is not so much the amount of sugar consumed as its frequency. Every sugary food or drink starts an acid attack in the mouth that lasts roughly half an hour. Snacking at intervals throughout the day, or sipping sweetened tea or coffee slowly over a long period, leaves the teeth in an almost uninterrupted acidic environment; eating the same sweet in one sitting at the end of a meal puts far less strain on the enamel.

The second important factor is saliva. Saliva neutralises acids, washes the tooth surfaces and carries the minerals needed to repair the enamel. This is why conditions that reduce salivary flow — the side effects of some medications, mouth breathing, insufficient fluid intake, or health problems that cause dry mouth — increase the risk of decay. Since salivary flow naturally decreases during sleep, going to bed without brushing and snacking just before bedtime are particularly risky.

Personal and structural factors also add to the picture. The deep, narrow grooves (fissures) on the chewing surfaces of the molars, areas that are hard to clean because of crowded alignment, and structurally weaker enamel all make plaque accumulation and decay easier. Pregnancy is also a period that calls for extra attention: hormonal changes make the gums more sensitive, nausea and vomiting bring the teeth into contact with stomach acid, and the need for frequent snacking can increase the number of acid attacks. During this period it is important to tighten up oral care and not to neglect dental check-ups.

What Are the Symptoms of Tooth Decay, and What Is Felt at Each Stage?

The most deceptive aspect of decay is that in its early stage it usually causes no sensation at all. A white spot lesion does not hurt; it is generally noticed only on close inspection or during a dentist's examination. The absence of pain does not mean the absence of decay — on the contrary, this symptom-free period is the stage at which decay is easiest to stop. This is precisely where the real value of regular dental check-ups lies.

As decay progresses, the symptoms usually appear in the following order:

• Chalky-white patches on the tooth surface that turn yellow and then brown over time
• Brief twinges and sensitivity with sweet, hot or cold foods and drinks
• A rough spot, chipped edge or small hole on the tooth surface that you can feel with your tongue
• Pain that increases when biting and chewing
• Dark brown-to-black discolouration of the tooth
• Persistent bad breath and a bad taste in the mouth
• In the advanced stage, throbbing pain that starts on its own and worsens at night, and swelling of the face

Some of these symptoms can also point to other problems; cold sensitivity, for example, can also arise from gum recession or enamel wear. Whether the source of the complaint is decay can only be determined through a dentist's examination; so rather than interpreting the symptom yourself and waiting, going in for a check-up is the safest course.

How Can Tooth Decay Be Prevented?

The essence of protecting yourself from decay can be summed up under two headings: reducing the number of acid attacks and strengthening the conditions that support enamel repair. The steps that can be built into daily life are clear:

• Brush your teeth twice a day for two minutes each time with a fluoride toothpaste; fluoride makes the enamel more resistant to acids and supports the repair of initial lesions.
• Use dental floss or an interdental brush every day for the surfaces between the teeth that the brush cannot reach; a significant share of cavities starts at these contact points between teeth.
• Try to limit sugary and acidic foods and drinks to mealtimes; reducing how often you snack between meals directly lowers the number of acid attacks.
• Drink enough water throughout the day; water both rinses the mouth and supports saliva production.
• Do not skip brushing before bed, and after brushing do not eat or drink anything other than water.
• Do not neglect regular dental check-ups and, when needed, professional dental scaling; hardened plaque cannot be removed at home, and its surface paves the way for new deposits.

Fissure sealants applied to the deep grooves of the molars can also be a protective option, particularly for teeth prone to decay. Who this application is suitable for is determined through a dentist's examination, taking the structure of the teeth and the risk of decay into account.

Why Does Tooth Decay Progress Faster in Children?

The enamel layer of baby teeth is thinner than that of permanent teeth; as a result, decay in children's teeth can progress much faster and reach the deep tissues of the tooth in a short time. Baby-tooth cavities dismissed with the thought that "they will fall out anyway" can cause pain and difficulty eating, and can also harm the health of the permanent tooth developing underneath and the position in which it will erupt.

Baby bottle tooth decay, a condition specific to young children, is linked to the baby falling asleep with milk, formula or sweetened drinks: reduced salivary flow during sleep leaves the teeth in prolonged contact with the sugary liquid, causing cavities that spread rapidly, especially on the front teeth. Starting to clean from the moment the first tooth erupts, avoiding the habit of putting the baby to sleep with a bottle, and going for dental check-ups at an early age are the foundations of prevention. If you have a concern about your child's teeth, a paediatric dentistry examination both assesses the current situation and allows age-appropriate fluoride and fissure sealant applications to be planned.

How Is Tooth Decay Treated at the Clinic?

The treatment of decay depends on the stage at which it is caught; the dentist therefore first determines the depth of the decay through an examination and, if deemed necessary, an X-ray. At the initial (white spot) stage, since no hole has yet formed, the tooth is not filled; instead, the lesion is managed with fluoride applications and adjustments to oral care and eating habits, with the aim of halting it, and it is monitored with regular check-ups.

In decay that has advanced into the enamel or dentine and formed a cavity, the decayed tissue is cleaned out and the lost part is restored with a filling. Once the decay reaches the pulp, a filling alone is no longer enough; to save the tooth without extracting it, root canal treatment — in which the inflamed vessel-and-nerve tissue is removed — comes into consideration. In cases where the tooth has lost too much substance and cannot be restored, extraction is the last resort; how the resulting gap will be addressed after extraction is planned separately.

The picture here is clear: the earlier decay is caught, the simpler the treatment and the more of the tooth's own tissue is preserved. Which treatment is appropriate for you is determined through a dentist's examination, taking the depth of the decay and the overall condition of the tooth into account.

In summary, tooth decay is a disease that begins silently through the combination of plaque, sugar and time — and one that can be stopped when caught early. If you notice white patches, sensitivity or discolouration on your teeth — or if you have not been for a check-up in a long while — it is worth not putting off a dental examination.

Frequently Asked Questions About Tooth Decay

Does tooth decay go away on its own? Only initial lesions at the white spot stage can be halted, with fluoride support and good oral care. Once a hole has formed in the enamel, the decay will not heal on its own or with home remedies; a dentist's examination is needed so it can be treated before it progresses.

What should be done about a tooth that is just starting to decay? A matt white patch you notice on a tooth is a good reason to see a dentist without delay. If the lesion really is at the initial stage, the aim is to halt its progression with fluoride applications, a review of brushing habits and a reduction in snacking frequency; the appropriate approach is determined through an examination.

What happens if a decayed tooth is not treated? Decay does not stop on its own; it advances from the enamel to the dentine and from there to the pulp. A problem that could be solved with a simple filling can, over time, turn into an inflammation requiring root canal treatment, an abscess, or even the loss of the tooth. As long as the decay remains in the mouth, it also poses a risk to the neighbouring teeth.

What helps with the pain of a decayed tooth? Until you can reach a dentist, gently cleaning the area, not chewing hard things with that tooth and avoiding extremes of hot and cold may bring temporary relief; before using a painkiller, you should consult a doctor or pharmacist. None of these is a treatment, however; even if the pain eases, the decay continues to progress, and you should be examined as soon as possible.

Does tooth decay cause bad breath? Yes, it can. Food debris and bacteria collecting in the cavity can lead to persistent bad breath and a bad taste in the mouth. As we noted in our article on the causes of bad breath, odour that originates from decay is only permanently resolved by treating the decay.

How is tooth decay recognised? In the early stage there are chalky-white patches; as it progresses, brown-to-black discolouration, a hole and sensitivity appear. Some cavities, however — especially those developing between the teeth and under old fillings — may not be visible from the outside at all. A definitive diagnosis is made through a dentist's examination and, if deemed necessary, an X-ray.