Most of us know roughly what a filling is: the material that fills a hole in a tooth. If you have ever had a tooth repaired, the dentist will have asked which kind you wanted. The usual choice is dark or white. Most people wonder why white fillings cost more, and assume it is because they are unobtrusive and do not spoil the look of your teeth.
A filling is an artificial material that fills a physical hole in a tooth. Those holes usually come from treating the tooth or removing decay. Although most of us divide fillings by colour (dark and white), their proper names are amalgam and composite.
When and why is a filling placed?
A decayed tooth is one affected or damaged by caries. Caries is a progressive disease that can be treated and halted, but the surest way to stop it spreading is to remove it entirely. In everyday terms, caries is a hole in a tooth.
The dentist opens the tooth and removes the decay with special instruments, depending on how much damage it has done. Depending on how much tissue is affected, the dentist places either a permanent or a temporary filling.
A temporary filling means filling the tooth with a particular medicament. A definitive or permanent filling means filling the cavity with a filling material. Filling is necessary both to replace the damage the decay has done and to protect the tooth from further damage and decay.
How is a filling placed?
The dentist first gives the patient an anaesthetic, then removes the decay with various instruments. Once it is gone, a base is placed to protect the pulp from irritation. The dentist then applies an acid that gives the filling material a larger surface to bond to.
After that the dentist places the bonding agent and the filling material. The tooth is then adjusted to fit the bite, so that chewing is not affected and nothing feels wrong. In essence the dentist's job is to leave the tooth so that nothing feels different when you bite.
A filling is not forever; it has a lifespan. How long it lasts depends on the composite material used. Its quality also depends on where in the tooth it sits. Fillings covering a larger surface are more prone to fracture, particularly in teeth used for chewing, which are under constant pressure. The quality and durability also depend on the quality of the lamp used to cure the filling.
Types of filling
There are essentially three types, two of them common: the white (composite) filling, the dark (amalgam) filling, and glass ionomer white fillings, used mainly to repair baby teeth.
White composite fillings
Composite fillings are every dentist's first choice when a tooth needs repairing. A composite filling is considerably more durable and more resistant to fracture. It also copes well with the moderate pressure of constant chewing. These fillings work equally well in front and back teeth.
In terms of appearance, white fillings are the better option, because the repair and the replaced part of the tooth are almost invisible. White fillings come in tooth colours, and a wide range of shades lets the dentist choose the one that matches the patient's teeth.
Amalgam fillings used to be considered better and stronger. As dentistry has developed, though, these materials have advanced considerably, and today they match amalgam for quality.
Dark amalgam fillings
Amalgam fillings, or dark ones as most people call them, are what most of us think of first, alongside the recognisable smell of a dental surgery. They are an alloy of mercury, copper, aluminium and zinc, and were long considered unsurpassed because they last so well.
Placing one is almost the same process as a white filling, with one significant difference: it bonds to the tooth mechanically rather than chemically. That means more tissue has to be removed than with a composite filling.
It has been suggested that mercury may be released from an amalgam filling over time, with a potentially toxic effect on the body, but those claims are not established.
Glass ionomer white fillings
Glass ionomer fillings are rarely used in adults. They are used as a definitive filling in baby teeth. They actively release fluoride and so protect the tooth from decay. They are white and hard, but considerably less resistant to the mechanical forces of chewing, so they do not last long.
Why are white fillings better than dark ones?
White fillings are the commonest in dental practice today, because they meet every requirement: strength, resistance to pressure and biocompatibility. What makes them so popular, though, is how they look.
White fillings blend completely with the colour of the tooth and are not noticeable, which matters a great deal when a front tooth is being repaired.
White fillings also bond micro-mechanically to the tooth, which gives further support. Composite material is versatile too: besides filling cavities it works well for repairing fractured and worn teeth. In a repair the dentist removes considerably less tooth tissue than with an amalgam filling, where a much larger part of the tooth structure has to go.
There are two drawbacks: how long they last, and how long they take to place. Amalgam fillings still last considerably longer than composite ones, although the gap narrows as the technology develops. Placing a white filling happens in stages, so it can take a little longer than placing an amalgam one.
A little history of white fillings
White fillings were first introduced in the 1960s as a better-looking alternative to amalgam. They have been through many refinements since, becoming steadily stronger and more durable, and reaching today's composite fillings, used in every kind of tooth.
Questions and answers about white fillings
Here we answer the questions asked most often about white fillings: their advantages, their drawbacks and how to look after them.
- Do white fillings last longer than dark ones?
- White fillings generally do not last as long as dark amalgam ones, but new technology improves their durability from year to year.
- How long does placing a white filling take?
- It can take longer than placing a dark filling, because the process happens in stages to give a better and more durable bond.
- Are white fillings more expensive than dark ones?
- They do cost more, but they look better and are more biocompatible.
- Is placing a white filling more painful?
- No. The dentist uses an anaesthetic, and the patient does not feel the procedure itself.
- Can a dark filling be replaced with a white one?
- Yes, a dark filling can be replaced with a white one, depending on the state of the tooth and the dentist's advice.
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