Types of Implants
Today, most dental implants are made of titanium. This metal has special qualities that make it useful for implants.
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. It 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 and fuses with it. The process is called osseointegration.
Titanium implants come with many types of surfaces. The surface is altered to improve the likelihood of osseointegration. The methods used to alter the surface include:
There are several types of implants. Root-form implants are by far the most popular. Subperiosteal implants and mini-implants are also used.
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. There are many approaches to a successful implant.
Root-form implants are called endosseous or endosteal implants. This means that they are placed in the bone. They look like screws, thick nails or cones, and come in various widths and lengths. A metal cylinder called an abutment is attached to the implant once it's solidly integrated into the jawbone. The abutment serves as a base for a crown, denture or bridge. For root-form implants to be successful, the bone needs to be deep enough and wide enough to provide a secure foundation.
Root-form implants can be inserted in two stages or one stage. The two-stage process is the traditional way. In this procedure, the implant is "buried" under the gum tissue in bone for three to four months. Then it is exposed during a second procedure so a healing cap can be placed. A crown, bridge or denture is attached to the cap later.
In a single-stage procedure, the implant is placed in the bone and remains exposed in the mouth with a healing cap on top. The cap helps guide the gum tissue as it heals around the implant.
The subperiosteal implant, which is rarely used now, may be used only in the lower jaw when you have no lower teeth and don't have enough bone for root-form implants. The subperiosteal implant is a custom-made metal frame that sits precisely on top of the bone, but under the gums. The frame includes metal spokes (abutments) that push through the gums into the mouth.
The first stage of making the implant is to make a model of your jaw. This is done in one of two ways. Sometimes an impression is taken of the bone after the tissue has been cut open. In other cases, the model is based on a computed tomography (CT) scan of the jaw. A dental lab will then use the model to make the implant.
At your second visit, the jawbone is exposed and the subperiosteal implant is placed. The tissue is stitched closed and the overdenture is temporarily cemented onto the protruding frame. The stitches can be easily removed a week later, since the overdenture does not usually sit directly on the gum. This overdenture can be either a series of crowns all connected (bridge) or a framework with acrylic and teeth (denture). It may remain temporarily cemented so the dentist can always adjust it.
These small implants are usually about 2 millimeters in diameter. This is almost half the size of many traditional root-form implants. Mini-implants consist of only one piece that screws into the bone and also extends above the gum line. They are placed in the same way as larger root-form implants. Crowns are often seated over the mini-implant right away. People often can walk out of the office and have functional, normal-looking teeth right after they are placed.
This type of implant can be used for small teeth, front teeth, pre-molars or missing teeth that are located in a narrow area. They also can be used to stabilize lower-jaw dentures. They are sometimes used when there is too little bone to place a larger implant. They also can be placed temporarily next to full-size implants. The mini-implants can hold crowns so it's possible to chew while waiting for the full-size implants to become integrated with the bone. Once this occurs, the mini-implants are removed and crowns are placed on the full-size implants.
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