General dentistry

Decay is a continuous process, not an on-off state. It starts as demineralisation in the enamel — at this stage it is only a chalky white patch with no cavity, and it is entirely reversible with topical fluoride and a change in eating habits. No drilling, no filling.

Once the enamel surface collapses into a cavity, the process cannot be reversed and a filling is required. If the cavity reaches dentine it spreads much faster, because dentine is softer than enamel. By the time it reaches the pulp chamber the only option left is root canal treatment — several times the cost, and the tooth permanently loses its blood supply.

The entire value of a six-monthly check-up sits here. It is not a ritual reminder; it is how a lesion is caught while it can still be handled with fluoride or a small filling, rather than at the stage that needs a root canal and a crown.

People tend to think a scale and polish is about whiter teeth and fresher breath. Those are side benefits. The medical reason is to prevent periodontal disease, the leading cause of tooth loss in adults — ahead of decay.

The mechanism goes like this: plaque mineralises into calculus at the neck of the tooth and spreads below the gum margin. Its rough surface holds bacteria against the gum tissue, causing chronic inflammation. Prolonged inflammation gradually resorbs the alveolar bone supporting the root. Bone that has resorbed does not grow back, and at some point the tooth loosens and is lost — even though it never had a single cavity.

What makes this dangerous is that the process is nearly painless until late. The one early sign you can see yourself is bleeding when you brush. Bleeding gums are not normal, and they are not caused by a hard toothbrush — they are inflamed gum tissue.

Directly placed composite shrinks slightly as it sets. In a small cavity that shrinkage is negligible. In a large cavity covering much of the biting surface, the accumulated shrinkage pulls on the cusps, causing pain on biting, creating microscopic gaps at the margin, and over time potentially cracking the wall of the tooth.

For those larger cavities, the more durable answer is an inlay or onlay — a ceramic restoration made outside the mouth from an impression, then bonded in. Because it is fully set before bonding, it does not shrink, it restores the correct contact point with the neighbouring tooth, and it withstands chewing loads far better.

The practical dividing line: a cavity that leaves enough sound tooth wall is well served by composite; one that has lost a wall or a load-bearing cusp is better served by an inlay or onlay; and a root-treated tooth with substantial structure loss should be crowned to protect it from a vertical fracture.