Tooth‑coloured fillings.

How tooth decay progresses

Decay starts when bacteria in plaque feed on sugars and produce acid, which draws minerals out of the enamel. It usually develops slowly, over months or years, and moves through fairly predictable stages.

The earlier it is found, the more options you have. Decay between teeth often can’t be seen or felt until it is well advanced, which is why bitewing x‑rays at check‑ups are so useful.

• Early mineral loss: a chalky white or brown patch on the enamel, with the surface still intact
• Enamel decay: the patch softens and the surface may break down into a small cavity
• Dentine decay: once it reaches the softer layer under the enamel, decay tends to spread faster and the tooth may become sensitive
• Near the nerve: deep decay can inflame the pulp, which may mean root canal treatment or, in some cases, losing the tooth

Fill it now or keep an eye on it?

Not every spot of decay needs drilling straight away. If the enamel surface is still intact and the decay hasn’t reached the dentine, it can sometimes be stopped or partly reversed with fluoride, better cleaning in that area and less frequent sugar.

In that case your dentist may record the spot, compare it on x‑rays at later visits and only suggest a filling if it grows. A filling is more likely to be advised once there is a cavity, the decay has reached the dentine, food is packing into the area or the tooth has become sensitive. Your overall decay risk, such as a dry mouth or frequent snacking, also shapes the advice.

A filling repairs the damage but doesn’t treat the cause, so we will also talk about what may be driving the decay.

Why we use composite resin

Composite is a blend of resin and fine glass-like particles, shaded to match your tooth. It bonds to enamel and dentine, so the cavity can usually be shaped around the decay alone, rather than cut to a set shape to lock the filling in, as older materials required.

It goes in as thin layers, and each layer is set hard with a blue curing light. Bonding needs a clean, dry surface, so the tooth is kept isolated while we work, which is one reason a composite filling can take a little longer than people expect.

Composite has limits too. The edges can pick up stain from tea, coffee or red wine over the years, and very large composite fillings in back teeth may wear or chip sooner than a restoration made in a dental laboratory.

Front teeth and back teeth

On front teeth, appearance matters most. Your dentist may layer more than one shade to mimic the slightly translucent edge of a natural tooth, and composite can also rebuild a chipped corner or smooth a worn edge.

Back teeth take much heavier chewing forces, and fillings there often need to recreate the contact with the neighbouring tooth so food doesn’t wedge between them. A thin metal band is placed around the tooth to shape that contact. When a cavity is very wide or a cusp has broken away, a filling alone may not be strong enough, and an inlay, onlay or crown can give the tooth more support.

Old silver (amalgam) fillings

Many adults still have amalgam fillings placed years ago. Current Australian dental guidance is that amalgam fillings in good condition don’t need to be removed, and drilling out a sound filling takes away some healthy tooth along with it, which can leave the tooth weaker.

If you would like an old filling replaced for appearance, we are happy to talk it through, including that trade‑off. We generally recommend replacing an amalgam filling only when there is a clinical reason, such as:

• Decay under or around the edges of the filling
• A crack in the filling or in the tooth beside it
• A broken or missing piece
• Ongoing sensitivity that has been traced to that tooth

Sensitivity after a filling

It is common for a newly filled tooth to feel sensitive to cold, air or biting for a few days. Deeper fillings can take a few weeks to settle as the nerve recovers, and the sensitivity usually fades gradually rather than all at once.

Pain when you bite down, especially if that tooth seems to meet first, often means the filling is a little high. That is a quick adjustment, so call us rather than putting up with it. Pain that lingers after a hot or cold drink, keeps getting worse or wakes you at night can mean the nerve is inflamed, and occasionally a tooth with very deep decay goes on to need root canal treatment even after a well-placed filling.

How long fillings last

There is no fixed lifespan for a filling. A small filling on a low‑stress surface can last many years, while a large one on a molar has a harder job. We check each filling at your check‑up, and a chipped or stained edge can often be polished or repaired rather than replaced.

Things that can shorten a filling’s life include:

• New decay starting at the edges, often linked to frequent sugar or a dry mouth
• Grinding or clenching, especially at night
• Chewing ice, pens or hard lollies
• A large filling replacing much of the original tooth
• Long gaps between check‑ups

What fillings cost

Cost depends mainly on how many surfaces of the tooth the filling covers and how much rebuilding it needs. Most extras policies list fillings under general dental, and the item number reflects how many surfaces are involved.

Eligible children may be able to use the Child Dental Benefits Schedule for fillings. Whether a baby tooth needs filling at all depends on how long it has left, and our children’s dentistry page explains how we decide.