From a patient's viewpoint, dentures are successful if they look good, feel good and function well.
Dentists, on the other hand, have a second concern when providing dentures. They want to prevent future problems that sometimes result from wearing dentures.
The problems related to the wearing of dentures can be grouped under three headings:One - Soft tissue damage
The amount of tissue affected can range from small patches to sizeable areas. There can be mild or severe inflammation of the mouth. Other soft tissue damage may be caused by mechanical irritation from the dentures, fungus infections and, sometimes, tumours. Fungal contamination of denture surfaces is very common but adjacent soft tissue is not always infected. Infected tissues may show either an angry redness or a white plaque.Two - Jaw joint changes
If the dentures do not fit properly, a wrong bite may cause changes in the jaw joint. The result can be joint pain, headache, neck pain and pain in facial muscles. These problems are often severe enough to interfere with day-to-day living.Three - Bone atrophy
Atrophy of a bone means it is shrinking in size. When atrophy occurs in the jaw bone, it may be due in part to pressure from the dentures. This is the most serious of common denture problems because it can not be reversed.
The problems caused by dentures may be due to a combination of factors. These causes often include improperly made dentures, poor denture hygiene, abnormal clenching and grinding of the teeth, incorrect chewing, wearing dentures at night, lack of follow-up dental supervision and some medical disorders.
As mentioned already, atrophy of the jaw bone is the most serious problem related to dentures. When other bones in the body are stressed, they can form new bone tissue which re-shapes the bone. This is not so for jaw bone under dentures.
When this bone has the constant wear and tear of chewing and other stresses put on it, it gradually erodes. The process is called resorption when the bone literally dissolves away under pressure. If osteoporosis (which is a condition where all the body’s bones may lack density) or other medical problems are present, the bone atrophy may be even greater.
Nature did not design the human jaws to support dentures. If teeth are extracted, all that remains is an irregular bony ridge covered with a thin layer of soft tissue (mucosa) and many nerve (Fig. 1a,1b) endings. These nerve endings cause pain when the mucosa is compressed between a hard denture and the saw-edged bone. (Fig. 2).
The broad palate of the upper jaw covers more area than the lower jaw. This larger area of the upper jaw helps to spread the stresses of chewing, thus reducing pressure on any given area of the jaw. The lower jaw does not have this advantage and is at greater risk of resorption because the load is concentrated in a smaller area along a ridge which consists mainly of porous bone.
Without regular dental supervision, an ill-fitting denture can destroy bone by imbedding itself into the lower jaw as time passes. Jaw-bone atrophy occurs leaving behind useless flabby tissue that does not adequately support a denture (Fig. 3).
Bone shrinkage is greatest during the first ten to twelve months after the extractions. It continues as a slower but steady life-long gradual bone loss with the jaws becoming less and less ideal for supporting dentures.
Except in people who already have osteoporosis, it is difficult to predict who will suffer severe bone loss. Obviously a history of severe bone loss with dentures should instil caution in both patient and dentist. The elderly, and women (particularly those past menopause) are likely most susceptible. All patients should be considered at risk for bone loss since prevention is more effective than a cure.
Denture construction - Dentures must be designed to spread biting and chewing stresses evenly over as great an area of each jaw as possible. The way the teeth meet during biting must be precisely calculated for each person. Tooth contact must be even and allow smooth sliding of the lower teeth against the uppers during jaw movements without the dentures becoming dislodged. Upper and lower front teeth should not make contact during relaxed, restful closure of the jaws.
Plastic artificial teeth, rather than porcelain, are the preferred choice. They match more closely the wear of natural teeth allowing better self-adjustment as dentures settle. They are also more hygienic since a bond forms between the plastic teeth and plastic base preventing a minute space at the gum-line where stain can form. Dentists often find it helpful to give patients written instructions about denture use and care.
Dentists are working to overcome the problems of bone resorption for denture wearers. They are having some success with techniques to build up the ridge of bone so it can provide better support for dentures.
If you wear dentures, there are several ways you can help to prevent bone loss from occurring.
Denture wearers do not need to be alarmed by information about problems they could encounter. Properly constructed dentures that are checked regularly for correct fit and bite, and are well cared for, are not harmful to the mouth.
You and your dental team all share a responsibility for your good oral health. The practitioner who constructs the dentures must make them fit properly. Your dentist cares for your natural teeth and dentures as well as checking the health of your mouth. Your ongoing role is to prevent bone loss by learning how to care for your dentures and your oral health.