Cavities (Holes in Teeth): Causes, Symptoms and Treatment

What Are Cavities (Tooth Decay)?

Every tooth has three main layers. The outer layer — enamel — is the hardest substance in the human body and acts as a protective shell. Beneath this sits dentine, a softer, yellowish layer containing microscopic tubes that connect to the nerve. At the centre lies the pulp, which houses the blood supply and nerve tissue that keep the tooth alive.

Tooth decay begins with a process called enamel demineralisation. When you eat or drink anything containing sugar or starch, bacteria in the mouth produce acid as a byproduct. This acid dissolves minerals from the enamel surface, weakening it over time. Saliva naturally helps repair this damage by depositing minerals back into the enamel — a process called remineralisation. However, when acid attacks happen more frequently than the mouth can repair, the enamel breaks down and a cavity forms.

Some people develop more cavities than others, even with similar diets and hygiene habits. This relates to individual factors such as saliva composition, the depth of natural grooves in the teeth, the types of bacteria present, and how tightly the teeth are spaced. Genetics play a role in enamel thickness and quality, which influences how resistant teeth are to bacterial acid attack.

Early intervention is key. When decay is identified at the white spot stage, it can often be reversed with improved oral hygiene and professional fluoride application. Once a cavity has formed, the damaged tooth structure cannot repair itself and professional treatment is required to prevent the decay from progressing deeper into the tooth.

What Causes Cavities?

Tooth decay is not caused by a single factor. It develops when several conditions come together — bacteria, a food source for those bacteria, time, and a susceptible tooth surface. Understanding each factor helps you take practical steps to reduce your risk.

The Role of Bacteria

Your mouth naturally contains hundreds of species of bacteria. Many are harmless, but certain types — particularly Streptococcus mutans — thrive on sugars and produce acid as a waste product. These bacteria form a sticky film called plaque that clings to tooth surfaces. When plaque remains undisturbed, the acid it produces sits directly against the enamel, gradually dissolving its mineral structure. Over time, this sustained acid attack creates the conditions for a carious lesion to develop.

Dietary Factors

Frequent sugar consumption is the single most significant dietary risk factor for dental caries. Each time you consume something sugary or starchy, bacteria produce acid for approximately 20 to 30 minutes. Fizzy drinks, fruit juices, sweets, biscuits and dried fruit are particularly high-risk because they contain concentrated sugars or cling to the teeth. Snacking frequently between meals extends the total time your teeth are exposed to acid, giving saliva less opportunity to neutralise and repair the enamel.

Poor Oral Hygiene

Inadequate brushing and flossing allows plaque to accumulate on tooth surfaces and in the spaces between teeth. Plaque that is not removed hardens into calcite deposits that trap more bacteria against the enamel. Areas between teeth are particularly vulnerable because they are difficult to clean with a toothbrush alone, which is why interdental cleaning is essential for preventing cavities in these hidden spots.

Dry Mouth (Reduced Saliva)

Saliva plays a crucial protective role in oral health. It washes away food particles, neutralises bacterial acid and delivers minerals that help repair early enamel damage. When saliva flow is reduced — a condition known as dry mouth or xerostomia — teeth lose this natural defence. Common causes include certain medications (such as antihistamines, antidepressants and blood pressure treatments), medical conditions affecting the salivary glands, and habitual mouth breathing.

Other Risk Factors

Several additional factors increase vulnerability to tooth decay in both adults and children. Deep natural grooves (fissures) on the chewing surfaces of back teeth trap bacteria and food debris in areas that are difficult to clean. Exposed root surfaces, which lack the protective enamel covering, are especially prone to root surface caries in older adults with gum recession. Worn or failing fillings can develop gaps at their margins where bacteria accumulate, leading to recurrent decay. Acid reflux and eating disorders that cause frequent vomiting expose teeth to stomach acid, accelerating enamel erosion.

Signs and Symptoms of Cavities

Recognising the signs of tooth decay early gives you the best chance of simpler, more conservative treatment. Symptoms depend on the stage of decay and the tooth surface affected.

Early Stage Symptoms

• White spots on teeth — Chalky white patches on the enamel surface indicate mineral loss (demineralisation) and are the earliest visible sign of decay beginning
• No pain at this stage — Early enamel changes are often painless, which is why many early-stage cavities are only detected during routine dental examinations
• Reversible with intervention — At this stage, improved hygiene and fluoride treatment may halt or reverse the damage before cavitation occurs

Progressive Stage Symptoms

• Sensitivity to sweet, hot or cold — As decay penetrates deeper, the tooth becomes reactive to temperature changes and sugary food or drink
• Visible holes or pits — You may feel a rough spot, catch food in a new area, or see a visible opening in the tooth surface
• Brown, black or white staining — A black spot on a tooth or dark discolouration often indicates active or arrested decay beneath the surface
• Pain when biting down — Discomfort on biting suggests the decay has progressed into the dentine, closer to the nerve

Advanced Stage Symptoms

• Persistent toothache — Continuous or throbbing pain that does not subside indicates the decay has likely reached the pulp
• Spontaneous pain without trigger — Pain that occurs without eating or drinking suggests nerve involvement or the beginning of an abscess
• Swelling around the tooth — Facial or gum swelling may indicate infection has spread beyond the tooth into the surrounding tissues
• Pus or bad taste — A persistent unpleasant taste or discharge near a tooth suggests abscess formation requiring prompt treatment

Types of Cavities by Location

Cavities can develop on different surfaces of the tooth, and each type presents differently. Understanding where decay tends to occur helps explain why certain areas need particular attention during your daily cleaning routine.

Pit and Fissure Cavities (Biting Surfaces)

Occlusal cavities develop on the chewing surfaces of premolars and molars, where deep natural grooves and pits trap food particles and bacteria. These fissures can be so narrow that toothbrush bristles cannot reach the base, allowing plaque to build up undisturbed. Pit and fissure cavities are common in both children and adults and are often the first type of decay to develop in newly erupted permanent teeth.

Smooth Surface Cavities

Smooth surface cavities occur on the flat outer surfaces of teeth or, more commonly, on the contact areas between adjacent teeth. An interproximal cavity — a cavity between teeth — is one of the most frequently diagnosed types because these areas are difficult to clean without floss or interdental brushes. These hidden cavities can grow substantially before becoming visible or symptomatic, which is why bitewing assessment during dental check-ups is valuable for early detection.

Root Cavities

Root surface caries develop on the exposed root surfaces of teeth, which lack the hard enamel covering that protects the crown. The root surface is made of cementum and dentine, both of which are softer and more susceptible to acid attack. Root cavities are more common in older adults who have experienced gum recession, exposing areas of the tooth that were previously protected beneath the gum line.

Stages of Tooth Decay

Tooth decay is a progressive condition. Understanding its stages helps you recognise why early-stage cavity detection and prompt treatment matter for preserving your natural teeth.

Diagnosis and Assessment

Accurate cavity detection is the first step toward effective treatment. Your dentist uses a combination of clinical methods to identify decay, assess its extent and determine the most appropriate course of action.

• Visual examination — Your dentist looks carefully at each tooth surface for discolouration, visible holes, rough areas and changes in enamel texture that indicate active or arrested decay
• Gentle probing — A fine-tipped dental explorer is used to check tooth surfaces for soft spots, catch points and areas where the enamel has broken down
• Bitewing assessment — Small bitewing images allow your dentist to evaluate the areas between teeth and beneath existing restorations, where hidden cavities commonly develop
• Sensitivity testing — Temperature and pressure tests help assess whether the pulp is healthy, inflamed or no longer vital, which guides the treatment decision

Cavity Treatment Options

The right treatment for a cavity depends on its size, location and how far the decay has progressed. Identifying decay early means simpler, more conservative treatment that preserves more of your natural tooth structure. Your dentist will explain all available options clearly before any treatment begins.

Fluoride Treatment (Early Decay)

When decay is detected at the earliest stage — before a cavity has actually formed — professional fluoride treatments can help reverse the damage. Concentrated fluoride applied directly to the tooth surface promotes remineralisation, strengthening the enamel and halting the progression of early carious lesions. This conservative approach avoids the need for drilling and filling entirely.

Dental Fillings

A dental filling is the most common treatment for an established cavity. Your dentist removes the decayed tissue, cleans the prepared area and restores the tooth with a durable filling material. Modern composite (white) fillings are matched to the shade of your natural teeth, providing both strength and a discreet appearance.

• Decayed tissue is carefully removed under local anaesthetic
• The tooth is restored with tooth-coloured composite material that bonds directly to the tooth
• The procedure is typically completed in a single appointment

Dental Crowns

When decay has destroyed a large portion of the tooth, a standard filling may not provide sufficient support. In these cases, a dental crown — a custom-made cap that covers the entire visible portion of the tooth — restores its shape, strength and function.

• Protects remaining tooth structure from further fracture
• Restores full chewing function and bite stability
• Usually requires two appointments — preparation and fitting

Root Canal Treatment

When decay reaches the pulp chamber, the nerve tissue becomes inflamed or infected. Root canal treatment removes the damaged pulp, cleans and shapes the root canals, and seals the tooth to prevent reinfection. A root canal for cavity-related pulp damage preserves the natural tooth and avoids the need for extraction.

• Removes infected pulp tissue and eliminates pain
• Preserves the natural tooth in the jaw
• A crown is usually placed afterwards to protect and strengthen the treated tooth

Tooth Extraction

Extraction is considered a last resort when the tooth structure is too severely damaged to be restored, or when infection cannot be adequately treated. Your dentist will only recommend removal when the tooth genuinely cannot be saved. Following extraction, replacement options including bridges, dentures and implants are discussed to restore function and prevent neighbouring teeth from shifting. In some emergency situations, extraction may be carried out by our tooth extraction service to provide relief from severe pain.

Cavities Before and After

Professional treatment restores teeth affected by decay to a comfortable, functional state. While every case is different, patients can generally expect the following outcomes after cavity treatment:

• Decayed tissue removed — All softened, damaged tooth material is carefully removed, leaving only healthy tooth structure
• Tooth structure restored — The cavity is filled with durable, tooth-coloured material that blends with the natural tooth
• Function and comfort improved — Normal chewing and biting are restored, and sensitivity typically resolves
• Pain resolved — Treatment addresses the source of discomfort, not just the symptoms
• Further progression prevented — Sealing the cavity stops bacteria from reaching the deeper layers of the tooth

Visit our smile gallery to see examples of restorative dental work. Individual results depend on the extent of the decay and the type of treatment provided.

Can You Reverse Tooth Decay?

The answer depends on how far the decay has progressed. In its earliest stage — when demineralisation has produced white spots on the enamel but the surface remains intact — the process can be slowed, halted or even reversed. Improved oral hygiene, reduced sugar intake and professional fluoride application help the enamel absorb minerals and rebuild its structure.

However, once the enamel surface has broken down and a cavity has formed, the damage is permanent. Tooth enamel does not contain living cells, so it cannot regenerate or repair a hole once one develops. At this point, professional treatment — typically a filling — is the only way to restore the tooth and prevent the decay from progressing into the dentine and pulp.

This distinction is important because it reinforces the value of regular dental check-ups. Catching decay at the white spot stage gives you the opportunity to reverse it without any drilling or filling. Waiting until pain develops usually means the decay has already progressed well beyond the reversible stage.

How to Prevent Cavities

Tooth decay is largely preventable. A combination of good daily habits and professional preventive care significantly reduces your risk of developing cavities at any age.

Effective Oral Hygiene

• Brush twice daily — Use a fluoride toothpaste and brush for at least two minutes, covering all surfaces of every tooth
• Clean between teeth daily — Use floss or interdental brushes to remove plaque and food from areas your toothbrush cannot reach
• Use fluoride mouthwash — A fluoride rinse used at a different time to brushing provides additional mineral protection for the enamel

Dietary Choices

• Reduce sugar frequency — It is the number of sugary episodes per day, not the total amount, that matters most for cavity risk
• Limit sugary drinks and snacks — Fizzy drinks, fruit juices, sweets and biscuits are among the highest-risk items for tooth decay
• Choose tooth-friendly snacks — Cheese, nuts, raw vegetables and plain yoghurt are less likely to contribute to acid attack
• Drink water between meals — Water helps wash away food particles and dilute acid in the mouth

Professional Preventive Care

• Regular check-ups — Routine dental examinations allow your dentist to detect early signs of decay before cavities develop
• Professional cleaning — Regular appointments with a dental hygienist remove plaque and calculus from areas that are difficult to clean at home
• Dental sealants for children — Protective dental sealants applied to the chewing surfaces of back teeth seal off deep grooves and fissures, preventing bacteria and food from accumulating
• Professional fluoride application — Concentrated fluoride varnish applied at your dental appointment strengthens enamel and helps resist acid attack

Additional Measures

• Chew sugar-free gum — Chewing after meals stimulates saliva flow, which helps neutralise acid and wash away food particles
• Drink fluoridated water — Tap water in many parts of the UK contains added fluoride that provides ongoing protection for tooth enamel
• Address dry mouth — If you experience persistent dry mouth, speak to your dentist about strategies to increase saliva flow and reduce decay risk

When to See a Dentist About Cavities

You do not need to wait for pain before seeing a dentist. Many cavities develop silently and are only detected during routine examination. However, the following signs indicate that you should arrange a dental appointment:

• Toothache or spontaneous pain that occurs without a clear trigger
• Sensitivity to hot, cold or sweet food and drink
• Visible holes, pits or dark spots on a tooth surface
• Pain when biting or chewing on a particular tooth
• A persistent bad taste in the mouth or swelling around a tooth
• Food catching in a new area that was previously smooth

Even without symptoms, attending regular dental check-ups is the most effective way to catch decay early and maintain long-term oral health. Book a consultation with our dental team at St Paul's Medical & Dental. For guidance on our fee structure, visit our treatment fees page.

Frequently Asked Questions About Cavities