What Does a Dental Cavity Look Like? Signs, Stages & Pictures Explained

What Is a Dental Cavity?

A dental cavity — also called dental caries or tooth decay — is a permanently damaged area in a tooth caused by acid-producing bacteria. These bacteria feed on sugars and starches from food, producing acids that gradually erode tooth enamel. Over time, this process creates a hole in the tooth structure.

According to the Public Health Agency of Canada, tooth decay is one of the most widespread chronic health conditions affecting Canadians across all age groups. More than 90% of adults will experience at least one cavity in their lifetime.

Without treatment, a cavity does not heal on its own. It spreads deeper through the enamel, into the dentin layer, and eventually reaches the pulp — the nerve-filled centre of the tooth — leading to infection, severe pain, and potential tooth loss.

The good news: cavities caught early require only a simple filling. Cavities caught in the white-spot stage may not require any drilling at all.

What Does a Dental Cavity Look Like?

The appearance of a cavity changes significantly as it progresses. Some cavities are visible to the naked eye; others can only be detected through dental X-rays. Here is what to look for at each stage.

Cavity Colours: A Quick Reference

• White or chalky spots — earliest stage; mineral loss but no hole yet
• Yellow or light brown — enamel decay beginning; pit or rough texture forming
• Dark brown — dentin decay; visible pit or hole
• Black — advanced decay; significant structural damage

Because surface stains from coffee, tea, or tobacco can look similar to early cavities, a dental examination is always needed to confirm whether a discolouration is decay or surface staining.

Can You See a Cavity at Home?

Some cavities on the biting surfaces of back teeth may become visible once they break through the enamel. However, many cavities form in locations impossible to see without professional tools:

• Between teeth (interproximal cavities)
• Beneath old fillings or crowns
• At or below the gum line
• On the roots of teeth in patients with gum recession

The Ontario Dental Association recommends routine dental X-rays as part of every comprehensive examination specifically because most cavities are invisible until they have caused significant damage.

The 5 Stages of Cavity Formation

Cavities do not appear overnight. They develop through five distinct stages, each representing deeper structural damage and requiring more involved treatment if left unaddressed.

Stage 1 — Demineralization (White Spot Stage)

What it looks like: Chalky white or opaque spot on the enamel surface, often near the gum line. No hole has formed yet.

Symptoms: Usually none. Mild sensitivity to sweets possible.

Treatment needed: This is the only reversible stage. Fluoride treatments, remineralizing toothpaste, and improved oral hygiene can repair the enamel before a cavity fully develops. No drilling required.

Stage 2 — Enamel Decay

What it looks like: Yellow or light brown discolouration. A small pit or rough area may develop on the tooth surface.

Symptoms: Sensitivity to cold drinks or sweets. Mild discomfort while eating.

Treatment needed: A dental filling. The decayed portion is removed and the tooth is restored. This is still an early, straightforward treatment.

Stage 3 — Dentin Decay

What it looks like: Clearly visible hole or pit. Dark brown to black colouring. Food frequently gets stuck in the area.

Symptoms: Sharp pain when chewing. Increased sensitivity to hot and cold. Persistent discomfort.

Treatment needed: Dental filling, or an inlay/onlay if the decay is extensive. Decay spreads faster through dentin than enamel, so prompt treatment is critical at this stage.

Stage 4 — Pulp Damage

What it looks like: Large dark hole. The tooth may appear broken or crumbling. Gums around the tooth may be swollen.

Symptoms: Constant toothache, often waking patients at night. Pain without any food trigger. Bad taste or odour from the tooth.

Treatment needed: Root canal treatment to remove infected pulp tissue and seal the tooth. A dental crown is usually placed afterward.

Stage 5 — Dental Abscess

What it looks like: Visible swelling of the gum, jaw, or face. The tooth may have broken. A pimple-like bump (fistula) may appear on the gum.

Symptoms: Severe, throbbing pain. Swelling of the jaw or neck. Fever. Difficulty swallowing in serious cases.

Treatment needed: Emergency dental care. Antibiotics to control infection followed by root canal or extraction. Untreated dental abscesses can spread to surrounding bone and tissue and, in rare cases, become life-threatening.

How Long Does It Take a Cavity to Form?

Cavity formation timelines vary considerably between patients. Several factors determine how quickly decay progresses.

The Acid Attack Begins in 20 Minutes

Plaque begins to form on teeth within 20 minutes of eating. When plaque bacteria encounter sugar or starch, they immediately begin producing acid — and that acid begins demineralizing enamel within the same sitting. This is why frequent snacking is significantly more damaging than eating the same total amount of sugar in fewer, larger meals: each eating occasion triggers a new acid attack cycle.

Typical Cavity Formation Timeline

• White spot stage: Weeks to months of repeated acid exposure
• Enamel cavity: 6 months to 1 year from demineralization if untreated
• Dentin decay: 1–3 years from initial enamel breakdown
• Pulp involvement: 3+ years in adults; faster in children due to thinner enamel

Factors That Speed Up Cavity Formation

• Frequent snacking or sipping sugary/acidic drinks throughout the day
• Inadequate brushing or flossing allowing plaque to accumulate
• Dry mouth (reduced saliva = less natural acid neutralisation)
• Deep grooves on molars that trap food and plaque
• Gum recession exposing softer root surfaces
• Previous cavities or fillings (margins can develop new decay)

Factors That Slow Cavity Formation

• Fluoride exposure (toothpaste, mouthwash, professional treatments)
• Good saliva flow — saliva naturally neutralises acid and remineralises enamel
• Consistent brushing twice daily and flossing once daily
• Dental sealants on back teeth
• Regular professional cleanings every 6 months

The critical takeaway: because early-stage cavities cause no pain, the only reliable way to catch them before they require significant treatment is through regular dental examinations with X-rays. By the time you feel pain, the cavity has almost always reached the dentin or beyond.

10 Signs of a Cavity You Should Never Ignore

Recognising symptoms early dramatically reduces the complexity and cost of treatment. Here are the ten warning signs most commonly reported by patients at Apple Tree Dental in London, Ontario.

1. Tooth Sensitivity to Hot or Cold

A sharp, sudden ache when eating ice cream or drinking hot coffee is often the first symptom patients notice. As enamel erodes, the dentin beneath becomes exposed. Dentin contains microscopic channels called dentinal tubules that transmit temperature sensations directly to the nerve, producing that characteristic sharp sting.

2. Sensitivity to Sweet Foods or Drinks

A reaction specifically triggered by sugar — a brief sting or tingling that fades within seconds — is a reliable early warning of enamel decay. Acid-producing bacteria are most active in the presence of sugar, making sweet sensitivity a meaningful clinical signal.

3. Spontaneous Toothache or Lingering Pain

A recurring ache that comes and goes without an obvious trigger, or constant throbbing pain, suggests decay approaching or reaching the pulp. Spontaneous pain — pain that starts without eating or temperature stimulation — warrants same-day dental attention.

4. Pain When Biting or Chewing

Discomfort on a specific tooth when biting down typically means decay has entered the dentin layer. The pressure of chewing compresses the damaged structure, causing a characteristic sharp pain that differs from generalised jaw soreness.

5. Visible Holes or Pits in the Tooth

A depression, pit, or rough area you can feel with your tongue — especially on the biting surfaces of back teeth — indicates that decay has broken through the enamel. A filling is required at this stage without exception.

6. Dark Spots or Staining That Won’t Brush Away

Brown, grey, or black discolouration that persists despite brushing may indicate structural decay rather than surface staining. Surface stains from coffee or tobacco sit on enamel; cavity discolouration reflects breakdown within the tooth structure. Only a dentist can confirm which type you have.

7. White Chalky Spots (Early Stage Warning)

An opaque, chalky-white area on an otherwise healthy-coloured tooth is the earliest visible sign of enamel demineralisation. At this pre-cavity stage, fluoride treatment can still reverse the damage — no drilling needed. These spots are most visible on front teeth and are often first noticed by a dentist rather than the patient.

8. Persistent Bad Breath or Unpleasant Taste

Bacteria living inside decayed tooth structure produce sulfur compounds that cause a consistent bad odour or taste that does not resolve with brushing or mouthwash. If bad breath is localised — traceable to one area of the mouth — a cavity or infection may be the source.

9. Swollen or Tender Gums Around One Tooth

Localised gum swelling, redness, or tenderness concentrated around a single tooth — particularly at the gum line — can signal that decay has advanced to the point of affecting surrounding tissue. Gum swelling alongside tooth pain is an indication to seek dental care promptly.

10. A Broken, Chipped, or Unexpectedly Rough Tooth Edge

If part of a tooth chips off without significant trauma, or you notice a newly sharp edge with your tongue, advanced decay may have hollowed out the internal tooth structure, making it brittle under normal chewing pressure. Teeth do not naturally chip without cause.

What Causes Dental Cavities?

Dental decay results from a specific chain of events involving bacteria, diet, and time. Understanding each factor helps explain both why cavities form and how to interrupt the process.

The Cavity Formation Process

1. Plaque accumulates — Plaque, a sticky biofilm of bacteria, forms on teeth surfaces every day. It begins building up within 20 minutes of eating.
2. Bacteria consume sugar — Bacteria in plaque feed on carbohydrates (sugars and starches) from food and drink. Sugar does not damage teeth directly — bacteria do.
3. Acid is produced — As bacteria metabolise sugar, they produce lactic acid as a waste product. This acid attacks tooth enamel.
4. Enamel loses minerals — Each acid attack lasts approximately 20–30 minutes and causes enamel to lose calcium and phosphate (demineralisation).
5. Saliva partially repairs the damage — In between eating, saliva neutralises acid and deposits minerals back into enamel (remineralisation).
6. The balance tips toward decay — When acid attacks are more frequent or severe than saliva can repair, permanent enamel damage accumulates and a cavity eventually forms.

Main Contributing Causes

• Poor oral hygiene — Infrequent or incomplete brushing and flossing allows plaque to remain on teeth and harden into tartar (calculus), which cannot be removed by brushing alone
• High sugar and starch diet — Frequent consumption of sugary drinks, candy, bread, crackers, and other fermentable carbohydrates provides continuous fuel for acid-producing bacteria
• Frequent snacking — Each eating occasion triggers an acid attack. Sipping a soft drink over 2 hours causes far more damage than drinking the same amount in 5 minutes
• Dry mouth (xerostomia) — Saliva is the mouth’s natural defence against decay. Medications, medical conditions, and mouth breathing that reduce saliva flow significantly raise cavity risk
• Inadequate fluoride exposure — Fluoride incorporates into enamel, making it harder and more resistant to acid. Low fluoride intake — from toothpaste, water, or professional treatments — removes a key protective factor
• Deep tooth grooves — The pits and fissures on back molars are naturally difficult to clean and prone to plaque accumulation
• Infrequent dental visits — Professional cleanings remove tartar that cannot be brushed away, and examinations catch early decay before it becomes extensive
• Gum recession — Exposed root surfaces have softer cementum rather than enamel, making them significantly more vulnerable to decay
• Existing dental work — Old fillings can develop micro-gaps at their margins over time, allowing bacteria to enter underneath

Assess Your Tooth Decay Risk

Not everyone faces equal cavity risk. Certain factors significantly increase your likelihood of developing decay. Review the list below honestly to understand your personal risk profile.

Higher Risk Factors

• Consuming sugary or acidic foods and drinks more than 3–4 times per day
• Brushing less than twice daily or skipping flossing
• Dry mouth caused by medications (antihistamines, antidepressants, blood pressure medications)
• Previous cavities in the past 3 years
• Visible tartar buildup along the gum line
• No dental visit in the past 12 months
• Orthodontic appliances (braces, retainers) that make cleaning more difficult
• Gum recession exposing root surfaces
• Diabetes or other systemic conditions affecting saliva production
• Smoking or using tobacco products (reduces saliva and oral immunity)

Lower Risk Factors

• Brushing twice daily with fluoride toothpaste
• Flossing once daily
• Using a fluoride mouthwash
• Professional dental cleaning every 6 months
• No cavities in the past 3 years
• Drinking fluoridated tap water
• Dental sealants on molar teeth

If you identify with three or more higher-risk factors, we recommend scheduling an examination at Apple Tree Dental in London, Ontario sooner rather than later. Early detection at this stage saves significantly on treatment costs and complexity.

How to Prevent Cavities

Dental cavities are largely preventable. The following evidence-based habits, recommended by both the Canadian Dental Association and the American Dental Association, form the foundation of effective cavity prevention at any age.

Daily Oral Hygiene Essentials

• Brush twice daily — Use a soft-bristled brush with fluoride toothpaste. Brush for a minimum of two minutes, ensuring you cover all tooth surfaces. Brush last thing at night without eating or drinking afterward.
• Floss once daily — Flossing removes plaque and food debris from between teeth where your toothbrush cannot reach. Interdental brushes or water flossers are equally effective alternatives.
• Use fluoride mouthwash — A fluoride-containing rinse used after brushing adds an additional protective layer, especially for patients with moderate to high cavity risk.
• Wait before brushing after acidic foods — Acid temporarily softens enamel. Brushing immediately after consuming acidic food or drinks (citrus, soda) can accelerate enamel wear. Wait 30–60 minutes.

Dietary Habits That Protect Teeth

• Reduce snacking frequency — Each eating occasion triggers a 20–30 minute acid attack. Consolidating snacks into fewer sittings gives saliva time to neutralise acid and remineralise enamel.
• Choose water over sugary drinks — Soft drinks, sports drinks, fruit juices, and flavoured coffee are among the most cavity-promoting beverages due to their combination of sugar and acid. Water — especially fluoridated tap water — is the best between-meal drink.
• Eat calcium-rich foods — Dairy products, leafy greens, and almonds support enamel mineralisation. Cheese in particular raises mouth pH after meals, actively counteracting acid.
• Limit sticky carbohydrates — Crackers, chips, dried fruit, and sticky candy cling to tooth surfaces and provide prolonged acid exposure. If consumed, brush soon afterward.
• Chew sugar-free gum after meals — Xylitol-containing gum stimulates saliva flow, which neutralises acid and washes away food debris. The xylitol itself also inhibits Streptococcus mutans bacteria.

Professional Preventive Treatments

• Professional cleaning every 6 months — Removes tartar that cannot be brushed away and allows early decay to be detected before it requires drilling.
• Fluoride treatments — Applied at the dental office, professional fluoride varnish provides a concentrated remineralising treatment that significantly reduces cavity risk, particularly for children and high-risk adults.
• Dental sealants — A thin plastic coating applied to the deep grooves of back molars. Sealants prevent food and bacteria from lodging in these hard-to-clean areas. Highly effective for children aged 6–14 but beneficial at any age.
• Dental X-rays — The only reliable method for detecting cavities between teeth, under fillings, and in the earliest stages before symptoms develop.

Cavities in Children: Early Childhood Caries

Tooth decay in children — clinically known as Early Childhood Caries (ECC), or commonly called baby bottle tooth decay — is the most common chronic infectious disease of childhood. It affects children before the age of six and can develop as soon as the first baby tooth erupts.

Why Children Are More Vulnerable

• Baby teeth have thinner, softer enamel than adult teeth, making them faster to decay
• Children are often unable to brush effectively without adult supervision
• Frequent exposure to milk, formula, or juice — especially during nighttime feeding — creates prolonged acid exposure
• The bacteria that cause cavities (Streptococcus mutans) can be transmitted from parent to child through shared utensils, kissing, or cleaning a pacifier in an adult’s mouth

Consequences Beyond the Teeth

Early childhood tooth decay has consequences that extend well beyond appearance. Untreated decay in baby teeth can cause:

• Severe pain affecting eating, sleep, and concentration at school
• Speech development difficulties
• Infection spreading to the permanent teeth developing beneath
• Bone infection in serious untreated cases
• The need for treatment under general anaesthesia

Prevention in Young Children

• Begin brushing with a tiny smear of fluoride toothpaste as soon as the first tooth appears
• Never put a baby to bed with a bottle containing milk, formula, or juice
• Transition from bottle to cup by age one
• Book the first dental visit by age one, or within six months of the first tooth erupting
• Ask about fluoride varnish applications at your child’s dental visits
• Ask about dental sealants when first permanent molars erupt (around age 6)

The Canadian Dental Association recommends children visit a dentist within six months of their first tooth appearing. Apple Tree Dental’s family dentistry team in London, Ontario sees patients of all ages, including infants and toddlers.

Dental Filling Materials: Which Is Right for You?

When a cavity is diagnosed, your dentist will remove the decayed tooth material and restore the tooth using a filling. Several materials are available, each with distinct advantages depending on the location of the cavity, your budget, and your dental insurance coverage.

Composite Resin (Tooth-Coloured Filling)

Best for: Front teeth and visible areas; small to medium cavities on any tooth.

Composite resin is the most widely used filling material today. It matches the natural colour of teeth, bonds directly to the tooth structure (meaning less healthy tooth needs to be removed), and sets immediately under a curing light. Composite is slightly less durable than amalgam under heavy chewing stress but is preferred for aesthetic reasons and its minimal tooth removal requirement.

Amalgam (Silver Filling)

Best for: Back teeth (molars and premolars) subject to heavy chewing forces; patients with limited budgets or no insurance.

Amalgam is a mixture of metals including silver, tin, copper, and mercury. It is exceptionally durable, typically lasting 10–15 years or more, and is generally lower in cost. Amalgam fillings are dark silver in colour and therefore less preferred for visible teeth. They have an excellent track record of safety and effectiveness confirmed by decades of clinical use.

Ceramic / Porcelain (Inlay or Onlay)

Best for: Larger cavities requiring more extensive restoration; patients prioritising both aesthetics and durability.

Ceramic restorations match tooth colour with greater precision than composite resin and are highly resistant to staining. They are typically fabricated in a dental laboratory and require two appointments. Cost is higher than composite or amalgam.

Gold

Best for: Patients prioritising maximum longevity; back teeth with heavy bite forces.

Gold inlays and onlays are among the most durable restorations available, lasting 15–20 years or more. They are biocompatible and cause minimal wear on opposing teeth. The significant drawbacks are high cost and gold colouring, making them uncommon in modern practice.

Glass Ionomer Cement

Best for: Baby teeth; cavities near the gum line; temporary restorations.

Glass ionomer releases fluoride, providing ongoing protection against further decay. It bonds well to tooth structure but is not as strong as composite resin and wears more quickly under bite forces.

Your dentist at Apple Tree Dental will recommend the most appropriate material based on the location and size of your cavity, bite forces in that area, aesthetic considerations, and your insurance coverage. No single material is best for every situation.

How Much Does a Cavity Filling Cost in Ontario?

Understanding dental filling costs in advance helps patients plan their care and avoid delaying treatment due to financial uncertainty. Here are current typical ranges for London, Ontario.

Typical Dental Filling Costs in Ontario

Costs vary based on the number of tooth surfaces affected, the specific tooth location, and your dental insurance plan. Many Ontario dental insurance plans cover 50–80% of basic restorative treatment including composite and amalgam fillings.

The Cost of Waiting

A cavity treated at Stage 2 (enamel decay) typically costs $150–$250. The same cavity treated at Stage 4 (pulp involvement) requires a root canal and crown costing $1,500–$3,000 or more. Treating cavities early is not just better for your teeth — it is significantly more affordable.

To inquire about filling costs or your insurance coverage at Apple Tree Dental, contact our South London or North London location directly.

Can You Eat After a Dental Filling?

Yes — you can eat after a dental filling, but timing and food choices matter depending on the type of filling placed.

Composite Resin Filling

Composite fillings harden immediately under a curing light during the appointment. You can eat as soon as the local anaesthetic wears off — typically 1–2 hours after leaving the clinic. Until sensation returns fully, avoid the treated side to prevent accidentally biting your cheek or tongue.

Amalgam Filling

Amalgam takes longer to fully harden and reach its final strength. Dentists recommend waiting at least 24 hours before chewing on the treated tooth. Eat soft foods and use the opposite side of the mouth during this time.

Temporary Filling

Temporary fillings can be eaten over after 1–2 hours, but hard, sticky, and crunchy foods should be avoided entirely. Temporary materials are designed to be removed at a follow-up appointment and are not built to withstand normal chewing forces.

Foods to Avoid After Any Filling (First 24 Hours)

• Sticky foods — caramel, chewing gum, toffee (can pull at the filling)
• Very hard foods — ice, hard candy, crusty bread
• Very hot or very cold foods and drinks (tooth may be temporarily sensitive)
• Chewy foods that require prolonged biting pressure

Sensitivity After a Filling Is Normal

It is normal to experience some sensitivity to temperature and pressure for a few days to two weeks after a filling. This typically resolves on its own. If sensitivity persists beyond two weeks, worsens, or is accompanied by throbbing pain, contact Apple Tree Dental — the bite may need a minor adjustment, or the tooth may require further assessment.

When Should You See a Dentist?

The most important dental appointment is a routine checkup — because early cavities have no symptoms and routine X-rays are the only way to find them. However, the following symptoms indicate you should contact a dentist promptly rather than waiting for your next scheduled visit.

See a Dentist Soon (Within a Week)

• Tooth sensitivity that has lasted more than two weeks
• A visible dark spot, hole, or pit in a tooth
• Persistent bad taste or bad breath from one area of the mouth
• A filling or crown that feels loose or has partially come out
• Pain when biting down on a specific tooth

See a Dentist Today (Same Day or Emergency)

• Throbbing pain that wakes you at night
• Swelling of the gum, jaw, or face
• Fever alongside tooth pain
• Difficulty opening your mouth or swallowing
• A tooth that has broken or cracked significantly
• A pimple-like bump on the gum near a tooth that has been hurting

Apple Tree Dental offers emergency dental care at both our London, Ontario locations. Do not wait when pain or swelling is present.

Frequently Asked Questions

What are the first signs of a cavity?

The earliest signs are white chalky spots on the enamel (visible on front teeth), mild sensitivity to sweet foods, and a slightly rough texture on a tooth. Many first-stage cavities cause no symptoms at all and are only detected during a dental X-ray.

Can you have a cavity with no pain?

Yes — the majority of early to mid-stage cavities cause no pain. Pain typically begins only when decay reaches the dentin or pulp, which represents moderate to advanced decay. This is why regular dental checkups are essential even when your teeth feel fine.

Can a cavity heal on its own?

Early-stage enamel demineralisation (the white spot stage) can be reversed with fluoride treatments and improved oral hygiene before a hole forms. Once a cavity has formed — meaning the enamel has broken down and a hole exists — it cannot self-heal and requires professional treatment.

How long does it take to fill a cavity?

A routine single-surface composite filling at Apple Tree Dental typically takes 30–60 minutes including freezing time. Larger cavities or multiple fillings in one appointment take longer. Root canal treatment involves two or more appointments.

Does getting a cavity filled hurt?

Local anaesthetic is applied before any drilling, so the procedure itself is not painful. You may feel pressure during the filling. Some sensitivity is normal for a few days afterward and typically resolves on its own.

How often should I get my teeth checked for cavities?

Most adults benefit from a dental examination and cleaning every six months. Patients with a history of frequent cavities, dry mouth, or other risk factors may benefit from more frequent visits. Your dentist at Apple Tree Dental will recommend an appropriate recall schedule based on your individual risk profile.

What is the difference between a cavity and tooth decay?

Tooth decay refers to the overall process of enamel breakdown caused by acid from bacteria. A cavity is the physical hole that forms in the tooth as a result of that decay process. Tooth decay precedes cavity formation — early decay can be reversed; a cavity cannot.

Are baby teeth cavities worth treating?

Yes. Untreated cavities in baby teeth cause pain, affect eating and speech development, and can spread infection to the developing permanent teeth underneath. Baby teeth also hold space for permanent teeth; premature loss due to decay can cause crowding and alignment problems in the adult dentition.