Cavities explained: What they look like, how fillings work, and how to prevent them
Cavities are areas of tooth decay caused by acid from plaque bacteria, and they can be hard to spot early on. Most cavities are quick and straightforward to treat with a filling, usually taking around 30–60 minutes. You can help prevent them by brushing with fluoride toothpaste, cleaning between your teeth daily, reducing sugary snacks and drinks, and keeping up with regular check-ups.
Cavities are one of the most common and preventable dental problems
Being told you have a cavity can be frustrating, especially if you feel you already look after your teeth. But you’re far from alone. Tooth decay is one of the most common health problems in the UK, affecting millions of adults and children every year.
The good news is that cavities are usually simple to treat, and you can often prevent new ones once you understand how they form and make a few daily changes. This article explains what cavities are, how to spot them, what causes them, what happens during a filling, and how to reduce your chances of getting more.
What is a cavity?
What does a cavity look like?
People often expect cavities to be obvious, but early ones are easy to miss.
In the early stages, a cavity might appear as:
- A white, chalky patch
- A slightly rough area on the tooth surface
These signs are subtle and are often picked up by dentists during a routine check-up or on an X-ray rather than at home.
As a cavity becomes more developed, it usually looks like:
- A brown or black spot
- A small pit or visible hole
- A darker line or shadow near the gumline
You may also notice sensitivity to hot, cold or sweet things, or food catching in the same place.
When a cavity is advanced, the damage is more obvious. Part of the tooth may break away, leaving a clear hole or sharp edge. You may have lingering pain, swelling, or a bad taste – all signs it needs quick attention.
Remember that a tooth can still have decay even if it looks normal. Pain or ongoing sensitivity should always be checked.
What causes cavities?
Now that you know what a cavity is, here’s why they happen.
Cavities form when acid sits on the teeth too often or for too long. This acid comes from plaque, a sticky film of bacteria that builds up on your teeth every day. When these bacteria come into contact with sugar, they release acid that softens enamel.
What makes cavities more likely isn’t just how much sugar you have, but how often you have it. For example:
- Sipping fizzy drinks or fruit juice throughout the day
- Regular sweet snacks or biscuits at your desk
- Frequent sugary tea or coffee
Each “sugar hit” triggers another acid attack, and the enamel has less time to recover.
You can also be more prone to cavities if you have:
- Deep grooves in your teeth
- Gum recession that exposes the softer root surface
- Dry mouth (from medication or health conditions)
- A history of previous decay
These factors don’t cause cavities on their own but can make it easier for acid to do damage.
How long does a cavity filling take and what happens during treatment?
Dental fillings are one of the most common dental treatments, and they’re usually quick and comfortable.
For a typical cavity, most dentists allow around 30–60 minutes. Smaller fillings can take less time, while larger ones may need a little longer. If you need several fillings, your dentist may do them in one visit or spread them out.
Here’s what usually happens:
- Examination and X-rays: The dentist checks the tooth and may take an X-ray to see how deep the decay is.
- Numbing the area: A local anaesthetic is used to numb the tooth so you won’t feel pain.
- Removing the decay: The dentist gently removes the damaged part of the tooth and cleans the space.
- Placing the filling: The filling material – usually tooth-coloured composite – is shaped to match the tooth. Composite is set hard with a small blue light.
- Final adjustments: The dentist checks your bite and smooths the filling so it feels natural.
When the numbness wears off after a few hours, you may feel mild sensitivity, but this normally settles within a few days. If it doesn’t, your dentist can adjust the filling.
How to prevent cavities
Preventing cavities is mostly about reducing how often acid attacks your teeth and keeping plaque under control. Small daily habits make a big difference.
Brush well
Brush twice a day with a fluoride toothpaste – once before bed and once during the day. After brushing, spit out the toothpaste but don’t rinse, as rinsing washes away the fluoride that protects your teeth.
Clean between your teeth
Floss or use interdental brushes once a day. This removes plaque from areas your toothbrush can’t reach.
Watch your sugar habits
Try to keep sugary food and drinks to mealtimes and avoid snacking or sipping sugary drinks between meals. Water and milk are the safest choices during the day.
Extra protection where needed
If you’re more prone to cavities, your dentist may suggest fluoride varnish, higher-fluoride toothpaste, or protective sealants for the deep grooves in back teeth – especially for children.
Regular check-ups
Your dentist will advise how often you should be seen based on your personal risk. These visits allow early problems to be spotted and help you fine-tune your brushing and diet.
If you still get cavities despite good habits, mention it to your dentist. There may be specific causes – like dry mouth or hidden sugar in your diet – that they can help you manage.
When should I seek urgent dental help?
Most cavities don’t cause immediate emergencies, but you should get urgent advice if you have:
- Severe toothache
- Pain that wakes you at night
- Facial swelling
- A high temperature linked to a dental problem
- Difficulty swallowing or breathing
These may be signs of a more serious infection and should be checked quickly. If you’re unsure, contact your dental practice or NHS 111.
How Alpha Dental Care can help
Alpha Dental Care has practices across England offering both NHS and private dental care. Whether you’re worried about a cavity, think you might need a filling, or want advice on preventing future decay, our teams are here to help.
Your dentist will examine your teeth, explain clearly what they find, and talk you through your treatment options. They’ll also offer personalised advice to help you avoid further cavities and keep your mouth healthy.
If you’re concerned about cavities – or just feel it’s time for a check-up – booking an appointment with your nearest Alpha Dental Care practice is a great first step.
