January 24, 2007

Implant

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Implants are devices that replace the roots of missing teeth, and are used to support crowns, bridges or dentures. Implants are placed in your jawbone surgically. Most of the time, implants feel more natural and secure than other methods of replacing missing teeth, such as dentures.
There are many reasons why it's important to replace missing teeth:

Having all of your teeth can make you more self-confident. You don't worry that people notice that you have teeth missing.

When teeth are lost, the area of the jawbone that held those teeth starts to erode. Over time, you can lose so much bone that your jaw will need a bone graft to build up the bone in your jaw before your dentist can place implants or make a denture that fits properly.

Tooth loss affects how well you chew and what foods you are able to eat. Many people who have missing teeth have poor nutrition, which can affect overall health.


The loss of teeth can change your bite, that is the way your teeth come together. Changes in your bite can lead to problems with your jaw joint, called the temporomandibular joint.
Losing teeth can lead to changes in your speech, which also can affect your self-confidence.
There are several types of implants, including root form, blade form, Ramus frame and subperiosteal implants.

Root-form implants are the most common type used today. A root-form implant looks like a small cylinder or screw and is made of titanium. After an implant is placed in the jawbone, a metal collar called an abutment eventually is attached to it. The abutment serves as a base for a crown, denture or bridge.

The key to the success of all implants is a process called osseointegration, in which the bone in the jaw bonds with the implant. Titanium is a special material that the jawbone accepts as part of the body.

The ability of titanium to fuse with bone was discovered accidentally. In 1952, a scientist named Per-Ingvar Brånemark was using titanium chambers screwed into bones as part of his research to discover how bone healed after an injury. When he tried to remove the titanium chambers, he found they had become bonded to the bone.


This discovery led Dr. Brånemark to do further research into how titanium implants might work. In 1965, the first root-form implants were placed in people. Other types of implants also have been used for the past 30 to 40 years. There are many implant systems available, made by various dental manufacturers.


Success
Available studies indicate that surgical placement of root-form implants is successful more than 90% of the time. When these implants fail, the problems usually occur within the first year after surgery. After that, only about 1% of all implants fail each year.


Implants have become increasingly popular since the American Dental Association (ADA) endorsed them in 1986. Between 1986 and 1999, the number of implant procedures tripled. An ADA survey found that the average number of implants placed by a dentist who does the procedure was 56 per year in 1999, compared with 18 in 1986. According to the survey, in 1999, 90% of oral surgeons, 68% of periodontists, 10% of prosthodontists and 8% of general dentists had performed implant procedures.


It is now estimated that between 300,000 and 400,000 implants are placed every year in the United States.


Implants Versus Alternatives
Depending on your particular problem, implants can be more expensive than the alternatives (denture or bridge). An implant plus a crown costs between $1,500 and $4,000. The fees will depend on many factors. Insurance companies generally do not cover this cost, although you should always check with your insurer.

While the upfront cost for implants can be more than for other types of restorations, the investment can pay off in the long run. You do not necessarily need an implant for every missing tooth. Your dentist can discuss how many implants you will need.
Other benefits of implants include:

Feel — Because implants are imbedded in your bone, they feel more like your natural teeth than bridges or dentures.

Convenience — You will not need to worry about denture adhesives or having your dentures slip, click or fall out when you speak.

Nutrition — You will be able to chew better with implants. Chewing can be difficult with regular dentures, especially ones that don't fit perfectly. A regular upper denture also covers your palate, which can reduce your sense of taste.

Self-esteem — Because implants are so much like your natural teeth, you will think about them less. Your self-esteem and confidence will be improved because you will not have to worry about denture problems or people noticing that you have missing teeth. Regular dentures also can affect your speech, which can make you less self-confident when talking with others.
Types of Implant
Today, most dental implants are made of titanium, a metal that has special qualities that make it useful for this purpose.

Titanium develops a thin film on its surface that protects it from corrosion. It is resistant to acids, salt solutions and oxygen, among other things. Titanium also is almost completely nonmagnetic and is extremely strong for its weight.

Perhaps most important, the body does not reject titanium implants as foreign objects. When implants are placed in bone, the bone grows around the implant in a process called osseointegration.

Titanium implants come with many types of surfaces, including acid etched, plasma sprayed, acid etched and grit blasted, and hydroxyapatite coated. Hydroxyapatite is a part of what bone is made from. It bonds with bone in a process called biointegration.
There are several types of implants.

Root-Form Implant
These are the most popular type of implant. Root-form implants are called endosseous or endosteal implants, meaning they are placed in the bone. They look like screws, thick nails or cones, and come in various widths and lengths. For root-form implants to be successful, the bone needs to be deep enough and wide enough to provide a secure foundation.

Your dentist decides which type of implant to use based on the quality of the bone in your jaw and the type of crown, bridge or denture that will be placed on the implant.

Root-form implants can be inserted in a two-stage process — the traditional way of placing them — or in a single-stage procedure. In the two-stage procedure, the implant is “buried” under the gum tissue for three to four months and then exposed during a second surgical procedure. In a single-stage procedure, the implant is placed in the bone and remains exposed in the mouth.

Ramus-Frame Implant
This type of implant can be used if the lower jawbone is too thin for a root-form or subperiosteal implant. A Ramus-frame implant is embedded in the jawbone in the back corners of the mouth (near the wisdom teeth) and near the chin. Once it is inserted and the tissue heals, a thin metal bar is visible around the top of the gum. Dentures are made that can fit onto this bar. Ramus-frame implants also can stabilize weak jaws and help to prevent them from fracturing.

Transosseous Implant
Transosseous implants originally were designed to be used in people who had very little bone in their lower jaws and who had no bottom teeth. However, they are rarely used today because placing them requires extensive surgery, general anesthesia and hospitalization. Also, their use is limited to the lower jaw. Placing transosseous implants involves inserting two metal rods from below the chin, through the chin bone, until they are exposed inside the mouth. The rods that can be seen inside the mouth are used to attach a denture. Most clinicians today prefer to use bone grafts and one of the other endosseous implant methods described earlier instead of the transosseous method because they are equally effective and do not require the level of surgery needed when placing transosseous implants.

Blade-Form Implant
This type of implant also is known as a plate-form implant. It is a type of endosseous implant (placed in the bone), but it is used less frequently than a root-form implant. Blade-form implants are flat rectangles of metal with one or two metal prongs on one long side. A blade implant is placed in the jaw so that the prong(s) stick out into the mouth where they will support crowns or bridges.
Adapted from: Columbia University Medical Center, School of Dental & Oral Surgery

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