Dental Fillings Explained: Materials, the Procedure and Aftercare

A filling is the most common way to repair a tooth damaged by decay. The idea is simple: remove the decayed part of the tooth, then rebuild the missing shape with a durable material so you can chew normally and bacteria cannot move deeper. The details, though, from how the cavity is found to which material is used, are worth understanding before you sit down for one.

How a cavity forms and is found

Bacteria in plaque feed on sugars and starches and produce acids. Repeated acid attacks draw minerals out of enamel. At first this shows up as a chalky white spot, which can sometimes be reversed with fluoride and better habits. If demineralisation continues, the surface breaks down and a cavity forms. Once decay reaches the softer dentin layer underneath enamel, it can spread faster, and eventually it can approach the pulp, the living tissue at the centre of the tooth.

Dentists find cavities by looking at and feeling the tooth surfaces, and by using bitewing X-rays, which show decay between back teeth that is invisible to the eye. Small cavities do not always hurt, which is why regular checkups catch many before you notice anything. Early lesions confined to enamel are sometimes monitored rather than filled; ask your dentist whether that is an option for you.

Filling materials compared

There is no single "best" filling material. The right choice depends on where the tooth is, how big the cavity is, how much biting force it takes, your risk of new decay, cost and coverage, and your own preferences.

Amalgam fillings that are intact and not decayed underneath do not usually need to be replaced just because of the material. Removing a sound filling also removes healthy tooth structure. If you are concerned, discuss it with your dentist, who can explain current guidance and the trade-offs.

What happens during the appointment

1. Numbing. The dentist usually numbs the area with a local anaesthetic, first applying a numbing gel so the injection is more comfortable. Very small or shallow fillings are sometimes done without it.
2. Removing decay. A dental drill or other instrument removes the decayed tooth structure. Some dentists use a rubber dam, a thin sheet that isolates the tooth and keeps it dry.
3. Shaping. The cavity is shaped to hold the chosen material. For composite, the tooth is etched and a bonding agent applied.
4. Placing the material. Composite is placed in layers, each hardened with a blue curing light. Amalgam is packed in and carved while soft.
5. Checking the bite. You bite on thin coloured paper so the dentist can find and smooth any high spots.
6. Polishing. The surface is smoothed so it feels natural against your tongue.

A straightforward filling often takes somewhere between 20 minutes and an hour, depending on size and how many teeth are being treated.

After your filling

Your lip, tongue and cheek may stay numb for a few hours. Avoid hot drinks and chewing until the numbness wears off so you do not bite or burn yourself. Composite fillings are fully hardened when you leave; with amalgam, dentists often suggest avoiding hard chewing on that side for the rest of the day.

Some sensitivity to cold, pressure or sweets for a few days, or even a couple of weeks, is common, particularly with deeper fillings. It should gradually improve. Call your dentist if:

• Your bite feels high or the tooth hurts sharply every time you close.
• Sensitivity is getting worse rather than better.
• You develop a throbbing ache, pain that wakes you at night, or swelling.
• The filling feels rough, cracked or loose, or food keeps catching.

A high bite is an easy fix: the dentist smooths it in a short visit. Worsening pain can mean the nerve is inflamed, which occasionally happens with deep cavities and may need further treatment.

How long fillings last

Fillings do not last forever. Their lifespan depends on the material, the size of the filling, how hard you bite or grind, and how well the edges are kept free of new decay. Large fillings in back teeth take a lot of stress. When a filling replaces a big share of a tooth, your dentist may suggest an onlay or a crown instead because the remaining walls of the tooth are at risk of cracking.

The best way to make any filling last is to prevent new decay around it: fluoride toothpaste twice a day, daily cleaning between teeth, fewer sugary snacks and drinks between meals, and regular checkups so small leaks are found early. If you grind your teeth, ask whether a night guard might protect your dental work.

Questions to ask before a filling

How large is the cavity, and can you show me on the X-ray? Is this something we could monitor instead? Which material do you recommend here, and why? What is the estimated cost, and what will my plan cover for each material? A dentist who welcomes these questions is a dentist worth keeping.