Saturday, October 6, 2012
Replacing Lost Teeth
Patients lose teeth due to a number of reasons. Some are as a result of an accident where a blow to the face can involve teeth. Some cases involve a severe loss of tooth structure, due to a history of caries (cavities) where a tooth may fracture under normal biting pressure. In rare cases an adult permanent tooth may never have erupted and the surviving 'baby' tooth may fracture from over-function.
The concern facing the dentist is what procedure to follow to replace the missing tooth/ teeth. This of course involves discussion of options with the patient. Factors such as the cost of treatment, the condition of the surrounding tooth, bone and gum tissue is important. There are also some situations where overall impracticality for oral reasons may preclude many options.
A viable choice may be to simply leave a space. In some cases cost and appliance choice exclusions may promote this choice. Replacing a missing front tooth provoke a have a greater sense of urgency than a non-visible posterior tooth. Depending on the location of the tooth, or missing teeth the choices take a different path.
Let us discuss a single lost tooth. One option is a bridge between the teeth on either side and dummy tooth to replace the lost tooth. This is called a three unit bridge, bridges are named by the elements involved, the fore mentioned three unit bridge but also 4-5-6-7 unit bridges, etc. In a bridge the teeth on either side of the lost tooth are prepared, the teeth are 'carved' using the dental handpiece and likely a diamond imbedded preparation burr. The prepared teeth could be considered as almost miniatures of the original teeth. But the prepared teeth are shaped so that a crown cast in the laboratory, can be slipped over the remaining structure. There is considerable care and experience needed to produce a good final crown preparation by both the dentist and the laboratory. The margin should be placed to the gum for cleanliness and appearance, the preparation should not be too deep so as to avoid the nerve. In some cases a root canal treatment is required to ensure proper retention of a crown. This involves removing tooth nervous tissue and a build up of lost structure with one of the polymer materials. The biting surface should be reduced sufficiently so as to allow the laboratory enough thickness on the biting surface on which the tooth is built up.
A detailed impression is made of the prepared tooth/teeth. A polyester, rubber-like material is used. Dental materials are such that they provide a consistent accuracy and reproduction of the tooth structure. The impression is poured and the laboratory uses the model as a basis for the new crown(s). A laboratory manufactured crown or bridge is 'cemented ' on the prepared tooth / teeth by a strong biologically neutral cementing material. Patients are carefully instructed in the care of their new appliance. Even an excellent crown can have a susceptible margin for intra oral decay.
Some cases can be very successful using implants. This involves surgically placing a retainer implant into the bone where the tooth was lost. In some cases there can be a need for bone augmentation, when there is not enough remaining bone to secure an implant. Some dentists do their own surgery; but, many prefer to refer to specialists such as periodontists (gum specialists) or oral surgeons. After the implant is secure in the tissue, (a time frame of several months to close to a year in challenging cases) the patient comes in for an impression. It is similar to the regular crown impression but added components are required. In a healing implant the surgeon places what is called a "healing coping." This looks like the top part of a golf tee sitting and attached to the implant. It is in fact screwed into the implant. At the impression appointment the healing coping is unscrewed and a part called the impression coping is placed in the implant. The goal is to take an impression of this coping, the impression material is injected and the tray holding the material has an opening so when the impression material sets, the impression coping can be unscrewed. The implant has a 'key' on the top opening and the impression coping fits into this. This ensures an accurate placement of the final crown. The position of the implant crown in the lab and in the patient are very accurately determined. This is transferred to a laboratory where the position of the implant, relative to other teeth in the patient,can be transferred to a poured impression. The lab then makes a coping to hold a crown. When the final coping and crown are returned to the clinic the dentist enters the final stage. The healing coping is again unscrewed and the tooth replacement coping is screwed into the implant. The tooth coping has "keys" that correspond to the position of the lab work. These are lined up, the coping tightened and an x-ray determines if it is properly seated. Then a 'ratchet' type wrench insures the crown portion is tightly seated. Then the crown is 'cemented' in a similar manner to the crown on a natural tooth.
An advantage of implants is that natural tooth structure is not reduced and they tend to last longer as natural teeth that have been reduced may weaken over time. But, a big impediment is the increased cost of an implant. The surgery, laboratory fees and the crown portion can be more than most three unit bridges. Some insurance companies do not cover implants. Determine this, with your dentist, before proceeding.
Other options can include partial dentures. These come in two varieties, one is all plastic and another had a light weight cast metal frame. The latter is more retentive and will last longer. But again cost can be a factor and many patients opt for the plastic variety. These are termed removable appliances. Unlike bridges or crowns they are removed for brushing or sleeping.
A partial denture is a thin cast frame that has teeth replacing lost teeth. It either crosses the palate in upper dentures or runs along the lower inside jaw. On the biting surface of the teeth there is a depression made in the surface, this retains the partial frame under conditions where a patient chews. As well both types have clasps that run like half rings around a tooth. They retain the dentures. In most situations where there is solid tooth structure patients have normal function as well as a good appearance. The well prepared partial dentures is such that the replacement teeth restore lost tooth function.
A complete denture is when all teeth have been removed for what ever reasons. The upper complete denture covered the palate and when well fitted it has a suction like retention and most patients have a good experience with this appliance. A lower complete denture is a bit more of a challenge. When people lose lower teeth the bone around the teeth can regress. That is, it basically shrinks and almost disappears. On the upper arch there is sufficient underlying bone to not make this a sensitive issue. But, in the lower arch the ridge can be very flat and awkward. Today many patients are having implants placed to help retain lower dentures. These can really make a great functional difference.
The options for tooth replacement depend on the number of teeth and their placement in the arches, the overall oral and general health of the patient, and budgetary considerations. If you find yourself in such a situation where you need to replace a part of the dentition, it may involve asking friends and acquaintances of their success in this area. Ask for a consultation, an evaluation and an estimate of the fees. It is also a good idea to seek a second or even a third or more opinion. If you are ensured consult with you carrier before you begin so that you know you benefits. Don't go by fees alone, try to assess what you feel about the dentist and the office.
Dentistry does offer many great options so there is no need to have less than you feel you deserve.
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