What is tooth decay, and what causes cavities?
Tooth decay is a common disease, caused by bacteria, that damages the hard tissues of the tooth: enamel, dentin and sometimes cementum.
It is extremely common: according to US data, about 90% of adults aged 20 to 64 have had decay in their permanent teeth, and about one in five has untreated decay (Dye B et al., 2015; CDC, 2024).
Decay starts when certain mouth bacteria break down carbohydrates and sugars and produce acids that soften the enamel. Over time this gradually destroys tooth tissue, forms a hole in the tooth (cavity) and lets infection spread into deeper layers. Without treatment, decay can cause irreversible damage.
What causes cavities? The main factors are a diet rich in sugar and processed carbohydrates, poor oral hygiene, too little fluoride, dry mouth and genetic factors. Decay is not a one-time event but a gradual process that can take months or even years, depending on each person's risk factors.
Types of tooth decay
Primary decay
Primary decay is the most common type: it appears on a surface that has never been treated and shows as discoloration and dark spots. It usually develops on the chewing surfaces of molars or between teeth, where brushing is less effective, and is treated effectively with fillings when caught early.
Secondary (recurrent) decay
Secondary decay develops next to existing fillings or crowns, usually because of microscopic leakage that lets bacteria in.
Early childhood decay
Early childhood decay affects babies and young children, mainly in baby teeth. It is often caused by prolonged use of a bottle containing sweetened drinks, especially at bedtime.
Root decay
Root decay appears on roots exposed by gum recession and is more common in older adults.
Rampant decay
Rampant decay progresses very quickly, usually because several risk factors combine.
Signs of a cavity: tooth decay symptoms and diagnosis
Recognizing the symptoms early is key to stopping decay before it causes complications. Early signs include increased sensitivity to temperature, sweet or acidic foods, pain when chewing and color changes on the tooth surface. With black stains on teeth, dark spots may be visible on the enamel or in the grooves of the molars.
As decay progresses, cavity pain may become spontaneous, sometimes with swelling or a fistula (a small "pimple") on the gum. An unpleasant taste or bad breath can also point to advanced decay. In children, tooth decay may show as difficulty eating, disturbed sleep or loss of appetite.
Diagnosis combines a visual clinical exam, gentle dental instruments and X-rays when needed. These detect decay even where it cannot be seen, such as between teeth or under existing fillings. The routine exam also assesses your personal risk factors: diet, oral hygiene, fluoride use and saliva.
How tooth decay damages a tooth
Untreated decay causes progressive damage that worsens over time.
Enamel demineralization
The first damage is demineralization of the enamel, the tooth's natural armor; once it is breached, the more sensitive inner layers are exposed. At this stage, before a hole forms, fluoride can still stop the process.
The dentin
Decay then reaches the dentin, a softer material that breaks down faster than enamel, and in advanced cases it reaches the pulp, which contains the nerves and blood vessels.
The pulp
When decay reaches the pulp, it causes inflammation and infection that can lead to death of the pulp, an abscess and severe pain. The infection can spread to nearby tissues and, in rare cases, cause life-threatening complications. Untreated decay can also spread within the tooth and to neighboring teeth.
| Layer affected | Possible treatment |
|---|---|
| Enamel, early stage (no cavity) | Fluoride, sealants and good oral hygiene, without drilling |
| Enamel and dentin (cavity formed) | Filling; when a large part of the tooth is destroyed, an inlay, onlay or crown |
| Pulp | Sometimes pulp capping; in most cases a root canal and a restoration |
| Tooth that cannot be restored | Extraction, then replacing the missing tooth |
In the long term, untreated decay (rotten teeth) can lead to tooth loss, difficulty chewing and speaking, and visible damage that affects self-confidence. Prevention is always preferable, and early treatment avoids major damage and more complex work later.
How is tooth decay treated?
Treatment depends on how deep the decay has gone: the earlier it is diagnosed, the simpler and more conservative the treatment. Treating decay early prevents it from spreading deeper, where it can reach the nerve.
Early stage: fluoride and stronger enamel
At first the enamel loses minerals and a white, chalky spot appears, before any cavity forms. According to the American Dental Association, fluoride helps repair the damage acids do to enamel, a process called remineralization (ADA MouthHealthy, Fluoride). At this stage, non-invasive treatments such as professional fluoride and sealants can stop decay and even reverse it, without drilling (Slayton RL et al., 2018).
Filling
Once decay has made a hole, the decayed tissue is removed and the tooth is restored with a tooth-colored composite filling that restores its shape and function.
Inlay / onlay or crown
When decay has destroyed a significant part of the tooth, a regular filling is not enough: an inlay or onlay restores part of the tooth, and a crown covers all of it. The aim is always to keep as much healthy tooth as possible, following minimally invasive principles.
Root canal
When decay reaches the pulp, an intermediate solution called pulp capping can sometimes keep the tooth alive. When the nerve is irreversibly damaged, a root canal is done to save the tooth, followed by a restoration.
Extraction
When a tooth is too damaged to be restored, it is extracted, and replacing the missing tooth is then discussed. Seeing a dentist early avoids this stage in most cases.
Examination, treatment plan and price quote
detailed and personalized
During the consultation, Dr Haim Aseriel examines your teeth, explains all the options and gives you a transparent price quote, with no obligation. The clinic is at 12 HaTnufa Street, Jerusalem.
How to prevent cavities
Preventing tooth decay starts with good daily oral hygiene, and continues with diet and regular check-ups.
01
Fluoride and brushing
Brushing twice a day for two minutes with a fluoride toothpaste, and cleaning between the teeth every day (floss or an interdental brush), is the first line of defense against cavities (ADA, Home Oral Care, 2024). Fluoride strengthens enamel and makes it more resistant to acid attacks.
02
Eating habits
Reducing sugary foods and drinks significantly lowers the risk of decay. Mouth bacteria turn sugars into acids that damage enamel, so keep sweets to mealtimes rather than snacking throughout the day. Drinking water after something sweet helps rinse away residue and lower acidity.
03
Regular check-ups
Regular visits and professional cleaning are essential to prevent decay. Cleaning removes plaque and tartar that brushing cannot, and check-ups catch decay at its earliest stage, when treatment is simpler and less costly. Sealants on molars and fluoride varnish add protection.
04
Dry mouth and early spots
Treating underlying issues such as dry mouth matters too, because saliva is a natural defense against decay; saliva substitutes or products that stimulate saliva can help. White spots on teeth can be an early sign of decay and should be checked promptly.
Think you have tooth decay? Seeing a dentist early makes treatment simpler. When decay already causes severe pain, ask for an urgent appointment with an emergency dentist; when a hole has formed, a suitable dental restoration is needed.
At the clinic, at 12 HaTnufa Street in Talpiot, south Jerusalem, the first exam assesses the decay visually and with X-rays when needed, then a plan is built around its severity and your preferences, explained in English, with a calm, supportive approach for anxious patients. The aim is not only to treat existing decay but also to give you the knowledge to prevent new cavities. Opening hours: Sun 8:00–19:00 · Mon 9:00–19:00 · Tue–Wed 9:00–21:00 · Thu 8:30–21:00 · Fri 8:00–14:00.
Tooth decay: questions and answers
Tooth decay is caused by certain mouth bacteria that break down sugars and carbohydrates and produce acids that soften the enamel. The main risk factors are a diet rich in sugar and processed carbohydrates, poor oral hygiene, too little fluoride, dry mouth and genetic factors.
Early signs of tooth decay include increased sensitivity to temperature, sweet or acidic foods, pain when chewing and changes in the color of the tooth surface. As decay progresses, spontaneous pain may appear, and sometimes swelling or a fistula (a small "pimple") on the gum.
No. In its early stages, tooth decay is "silent" and progresses without noticeable symptoms, which is why regular check-ups matter. Pain usually appears once decay has reached the deep layers of the tooth, close to the nerve, and urgent treatment may then be needed.
Decay that has broken through the enamel and formed a cavity does not heal naturally and must be restored by a dentist. At a very early stage, when there is only demineralization of the enamel, the process can be stopped and even reversed with fluoride and better oral hygiene. Home remedies cannot repair a cavity that has already formed.
Cavities are prevented mainly by brushing twice a day with fluoride toothpaste and cleaning between the teeth with floss. Reducing how often you eat and drink sugary foods and drinks significantly lowers the risk of tooth decay.
Sources
- Dye B et al., NCHS Data Brief, 2015 – View the study
- Centers for Disease Control and Prevention, 2024 Oral Health Surveillance Report – View the page
- American Dental Association (MouthHealthy), Fluoride – View the page
- American Dental Association, Home Oral Care, 2024 – View the page
- Slayton RL et al., Journal of the American Dental Association, 2018 – View the study
