Why do dentures sometimes fracture?

Millions of people around the world wear dentures successfully. Problems do arise from time to time, often because of overdue maintenance. This occurs in the same way any appliance in daily use needs periodic maintenance and eventual replacement.

Fractures occur commonly and are normally a symptom of an underlying problem. Fractures should not occur in dentures under one year old. However, if the denture is provided immediately after surgery, then fracture is highly likely unless planned maintenance is carried out after approximately eight weeks. This is because all fractures that occur in the mouth happen because of changes that have taken place there, causing the denture to constantly over-flex during mastication. The healing process and shrinkage of the jaw bones cause changes within the mouth.

Maintenance is often a reline of the denture. This can be localised to an area known to have changed shape, or a total reline, where the whole "fit surface" (the surface that fits the contour of the gums) is renewed.

During a denture's lifetime it may be relined once or twice, after which replacing the denture should be considered.

The plastic denture base has a certain amount of natural flexibility to reduce the likelihood of a fracture. As the denture gets older this reduces and becomes more brittle. This is another reason dentures can fracture as they get older.

Dentures sometimes fracture for reasons other than shrinkage of the gums. If a plastic denture fractures even after relining, the solution may be to use a metal denture base for additional strength.

Generally speaking, the smaller the denture (that is the less teeth it replaces), the greater the risk of fracture, and the shorter its life expectancy. The larger the denture, the stronger it can be made.

When a denture replaces most or all of the natural teeth, the masticatory efficiency of the wearer is drastically reduced - possibly as much as an 80% reduction in the ability to chew food.

Smaller dentures therefore have to "work" in a much harsher environment where masticatory forces are still very high. Fractures and wear in this situation are therefore more likely.

High quality acrylic denture teeth (as used by Bath Denture Service) are sufficiently hard to oppose natural teeth when chewing. They are sufficiently "soft" not to do damage to the opposing teeth. Less expensive teeth can be used, but shorten the life expectancy of the denture because they tend to be much softer and wear at a much quicker rate.

Why make a denture?

There are four main reasons why a denture would be prescribed.

• For aesthetic reasons, eg after a traumatic accident or unexpected loss of front teeth. A denture may be provided relatively quickly so that a patient’s confidence and dignity can be restored while initial healing takes place.

• Where many natural teeth have been lost, a denture may be prescribed to help restore some masticatory efficiency. Digestive problems can arise when a person is swallowing food without chewing it properly first.

• A natural tooth can continue to erupt if the tooth opposing that tooth (in the opposite jaw) has been lost. The denture would fill this "gap" and therefore prevent "over eruption" of opposing teeth from occurring. Likewise, teeth in the same jaw will also move into the gaps left by lost teeth, so a denture would help to stop this happening.

• The teeth are the natural "spacers" that separate the upper and lower jaws. When many natural teeth have been lost, the lower jaw will rise and move forward slightly, giving a "witch-like" appearance. Dentures can restore the face to natural proportions and in doing so hopefully prevent any pain arising from the jaw joints (tempromandibular joints), just below the ears.

Dentures may be prescribed when large restorations have failed, for example a large bridge, or single crowns. Dentures can sometimes be the only solution to a dental problem or they may be a temporary part of a long complex treatment, such as the placement of dental implants.

Why not make a denture?

Any foreign body in the mouth has the potential to do damage to the surrounding tissues, the gums and the existing teeth. Examinations of dentures have shown varying deposits of plaque and tartar. There is a clinical judgement to be made as to whether the benefits of wearing a denture outweigh the potential damage a denture could cause. This judgement would be made by a dentist after discussing with the patient the treatment options and examining the tissues of the mouth. This may be done in conjunction with dental x-rays.

Many dentists believe from past research that approximately ten teeth in each jaw, giving twenty opposing contacts is the minimum sufficient for chewing purposes. This is known as the "shortened dental arch". Obviously if the teeth are lost at the front of the mouth, aesthetic reasons might dictate the prescription of a denture.

Design of the denture, its shape, size and materials used for its construction are very important. What is also equally important is denture and oral hygiene by the patient after the denture is supplied, so that possible damage caused is minimalized.