When a single tooth is lost and must be replaced there are few alternatives. A tooth may be replaced with a removable device (a denture), a device that is permanently attached to other teeth (a fixed bridge), or a dental implant may be used to replace the root of the tooth and a crown or cap may be attached to it. While any of these techniques usually provide satisfactory results, the implant-supported crown is the solution that will look and feel the most like the tooth it replaces.
A dental implant is a piece of titanium usually shaped like a screw or a cylinder. When used as a dental implant, titanium is so biocompatible that parts of bone cells actually attach to the implant. Dental x-rays and microscopy show that there is no space between the titanium and bone after healing.
There are a few steps involved in replacing a tooth this way. First, the dentist who will make the crown and the oral surgeon must evaluate the patient's medical history. Many medical conditions and smoking may interfere with healing and cause the bone not to knit to the implant. About five implant in a hundred will fail in the first year. These failures are usually due to the patient's health.
The surgeon must be sure that there is enough healthy bone to support the implant and crown. Inadequate bone may be added to with bone grafts, which may be the patient's own bone from another area, natural bone from another source, or man-made materials. Bone grafting may be done at the same time the implant is placed or a few months before. The surgeon will decide if grafting is necessary as well as the best time and material for each patient's condition.
Implant crowns are made by general dentists and prosthodontists (dentists who specialize in replacing and rebuilding teeth) and dental lab techs. Before surgeons place the implant, they usually rely on the restoring dentist to tell them exactly where the tooth will be. This is done by making a device called a surgical stent that attaches to the other teeth and directs the surgeon where to place the pilot hole for the implant. Patients often hand-carry this device to the surgeon so that they are sure that the device is there when the surgeon needs it.
The surgery is usually done in two visits. The first procedure is to make a very exacting hole in the bone to accept the implant. The implant should be a very tight fit and is either screwed into the bone or pressed firmly into place. The gum is closed over the implant to allow the bone to knit to the titanium implant. Two to six months later, the gum is opened by the surgeon to allow the restoring dentist access to the implant.
About two weeks after the implant is uncovered, the restoring dentist takes an impression of the teeth and the implant. The impression is sent off to a dental lab where the crown is custom made by dental technicians per the dentist's prescription. The crown is usually ready to deliver to the patient's mouth in two to three weeks.
Each of the above steps is very important. Should any measurement, impression or device be off by a fraction of a millimeter the final product may not be satisfactory.
Dental implants are often used for other purposes than to provide support for a single crown. For example:
The state-of-the-art in the replacement of lower teeth has become the full denture supported by two to four implants . The implants maintain the bony support for the denture and can retain the denture in place with devices that look like coat snaps.
Many people have had their entire upper and lower teeth replaced with implants and fixed bridgework.
Implants may be used in orthodontics to provide an anchor for braces where the patient is missing teeth.
It is always a good idea to ask your dentist for his or her opinion on how best to replace your tooth. Whether it is by implant, bridge or denture, the best time to replace that tooth is now.
Dr. David Leader is the Chairman of the Health Advisory Committee of the Lynnfield Schools, a member of the Professional Advisory Committee of Tri-CAP Head Start, and is a member of the Mass Dental Society Council on Dental Care and Benefits Programs.