What is a filling?
Decay begins when acids produced by bacteria in plaque dissolve the mineral in tooth enamel. Once the damage passes through the enamel into the softer dentine beneath, the tooth cannot repair itself, and the cavity grows. A filling removes the affected tissue and replaces it with a material that seals the tooth against further bacterial invasion.
Fillings are also used to repair teeth damaged by wear, erosion, chipping or a cracked restoration. The aim is always the same: remove what is compromised, protect what is healthy, and restore a surface that works in the bite.
Small cavities near the surface can be treated straightforwardly. Where decay has reached the nerve, a filling alone is not enough and root canal treatment is needed first. The examination and radiograph establish which situation applies.
Who may need this treatment
A filling may be needed when:
- A tooth is sensitive to sweet, hot or cold food and drink.
- A dark spot, pit or visible hole is present on a tooth surface.
- Food lodges repeatedly in one place between the teeth.
- An old filling has worn, cracked, fallen out or darkened at the margins.
- A cusp or corner has chipped away from a tooth.
- A radiograph shows decay that is not yet causing symptoms.
The treatment process
Examination and imaging
The tooth is examined and radiographed so the extent of decay is known before it is removed. Sometimes the true size of a cavity is only apparent once the overhanging enamel is cleared.
Anaesthesia
Local anaesthesia is used where needed, so the tooth can be worked on without discomfort.
Removing the damaged tissue
Decayed and unsupported tooth structure is removed until sound enamel and dentine remain. The cavity is shaped so the filling material will be retained and the margin can be sealed.
Placing the material
The filling material is placed in layers. Tooth-coloured composite is hardened with a curing light and shaped to reproduce the anatomy of the tooth; other materials are packed and finished in different ways.
Checking the bite
The patient is asked to close and the marks are checked with articulating paper. A filling that stands even slightly high can cause tenderness, so the bite is adjusted until it is even.
Finishing and review
The margins are polished so that plaque is less likely to accumulate, and the tooth is reviewed afterwards to confirm it has settled.
Benefits of treatment
Removing the affected tissue and sealing the cavity prevents the damage from extending deeper into the tooth.
A restored tooth loses the exposed dentine surface that was causing sensitivity to sweet, hot or cold.
The tooth can bear normal biting and chewing load again rather than being avoided.
Composite materials can be matched to your natural shade, so the restoration is not obvious.
Modern materials allow decay to be removed selectively and the remaining tooth structure retained.
Treating decay promptly is what prevents a tooth from becoming unsalvageable later.
Seeing the extent before removing anything
The size of a cavity is not obvious from the surface. Radiographs show decay between teeth and estimate its depth, and magnification and good illumination let the dentist see the dentine–enamel junction and identify unsupported enamel before it fractures.
Where a restoration needs to be larger, the material choice changes. Bonded composites suit small and moderate cavities; for heavily broken-down teeth, an inlay, onlay or crown may be more predictable. The bite is verified with articulating paper at the end of every filling, because a high restoration is a common cause of post-treatment tenderness.
- Radiographs before and after to document the restoration
- Bright, unobstructed illumination of the working field
- Isolation to keep the area dry while bonding
- Layered placement with proper curing between layers
- Bite verified and margins polished at completion
Comfortable, straightforward appointments
Comfort is a clinical decision, not a courtesy — it shapes how treatment is planned and how it is carried out.
Questions About Dental Fillings
The questions patients ask most often about this treatment, answered directly.
How long do fillings last?
It varies with the material, the size of the restoration, the forces on the tooth and your hygiene. Margins can wear or stain over time, which is why fillings are inspected at routine examinations and replaced when they no longer seal.
Will my tooth be sensitive afterwards?
Some sensitivity to temperature is common for a period after a deep filling, and it usually reduces as the tooth settles. Persistent or worsening pain, or tenderness on biting, should be reported so the tooth and the bite can be checked.
Why does my old filling look dark at the edges?
Staining or a visible line at the margin often indicates that the seal has deteriorated and bacteria have started to track underneath. Replacing the restoration before deeper decay develops is usually simpler than waiting.
Can decay come back under a filling?
Yes, and it can develop without much warning. That is the reason routine examinations include checking the margins of existing restorations and taking radiographs at appropriate intervals.