Dental Implants

Dental implants have been around for 50 years. The old type of implant consisted of a metal alloy. One type was placed inside the bone (blade implant) and another on top of the bone (subperiosteal). These were unpredictable and difficult to place.

In the late 1950's a young Swedish orthopedic surgeon, Professor Per-Ingvar Branemark, was doing a research project in which he placed open titanium chambers into the tibial bones of rabbits. He was studying how bone revascularizes as it heals. When he attempted to remove the titanium chambers he found that they were stuck to the bone (ankylosed). He was intrigued by this and studied the phenomenon. He discovered that the elemental metal titanium could bond with live bone cells. He eventually designed an implant system for the human jaw made from pure titanium. The first ones were placed in the front of the lower jaw. Some of these implants are still in place today at over 30 years of service. Professor Branemark termed these implants "osseointegrated", after the way the bone actually bonds or attaches to the titanium surface. The Branemark implant system was introduced to the United States in 1985. Since this time other titanium implant systems have been developed. Osseointegrated implants are now commonly used, and are very predictable. They are used to replace single teeth and multiple teeth. They can support single crowns, bridges, and dentures.

The Surgical Procedure

The implant sites are sized using a gentle drilling sequence. The titanium implant is then placed into the jaw. The implant is left alone for 3 to 6 months to allow the bone to grow and attach to the implant surface.

The implant is then uncovered after the healing period (3 to 6 months). A healing abutment (post) will be placed into the implant, and the gums will heal around it. Your Dentist will take an impression of your implant position after your gums heal. The dental laboratory will make a model of your teeth and implants and fabricate replacements. Your dentist will then fit your new tooth or teeth.

Clinical Application for Implants

1. Single crowns
A single implant can replace a missing tooth and prevent the cutting down of adjacent teeth for a 3 unit conventional fixed bridge.

2. Replacement of multiple missing teeth

Implants can be placed in multiple sites and restored separately or attached together with fixed bridges.

3. Stabilization of dentures

A. Upper Jaw (maxilla)

Bar supported denture.

• 4 implants can support a bar, which the full upper denture can snap onto. 4 implants are generally not strong enough to have the palate (roof of mouth) of the denture removed as it is needed for support. Otherwise too much stress will be placed on the implants and this can lead to failure.

6 to 8 implants in the maxilla can also support a bar. The maxillary denture can have the palate (roof of mouth) removed in these cases due to the increased number of implants. This will enhance the taste of food and feel less bulky.

Fixed Prosthetics (Permanently attached teeth)

6 to 8 implants can be utilized to support a fixed hybrid prosthesis. This consists of a cast metal base on which denture teeth and pink acrylic is placed. This is secured to the implant with screws and cannot be removed by the patient. It sits slightly above the tissue so that the implant abutment posts can be cleaned. This works well in cases where the amount of bone available is limited. Generally this is the case in the patients who have worn dentures for a long period of time. The jawbone will resorb (melt away) slowly over time due to the lack of tooth roots to stimulate it and also because of the pressure from denture function. The placement of dental implants will prevent further bone resorption.

6 to 8 implants can also be utilized to support a conventional fixed bridge. This can be done in cases where there is sufficient bone available. If the bone resorption results in a significant amount of ridge height loss, the teeth placed on the implants will be too long and look misshapen. In cases like this it is better to have the fixed hybrid (see above) placed.

B. Lower Jaw (mandible)

2 implants

2 implants in the chin area can support a small bar or 2 trailer hitch type attachments (see illustration). These will increase stability and keep the denture from sliding. The back portion of the denture will move up and down with chewing due to the limited number of implants placed.

4 implants

4 implants can be placed in the chin area for support of a bar. The denture will snap onto the bar. This bar is big enough to fully support the denture and prevent movement. This is much more stable than the 2-implant case (see illustration).

5 implants

5 implants in the chin area (anterior mandible) can support a fixed hybrid (highwater) prosthesis. This consists of a metal cast base with pink acrylic and denture teeth processed onto it. This is retained by screws attached to the implant abutments. This acts like a fixed bridge. It sits above the tissue and is extremely stable.

6 to 8 implants

• If there is sufficient bone available in the lower jaw a higher number of implants can be placed. This will provide sufficient support for the placement of a fixed porcelain bridge.

FAQ

What are implants?

They are titanium screws or cylinders. They range in size from 3.2 mm to 6.5 mm in diameter. They also come in different lengths (7mm to 16 mm).

Can they get cavities or gum disease?

You'll never have to worry about cavities with implants. Implants can develop periodontal disease (gum disease). It is known as periimplantitis. However, implants seem to be less susceptible to gum disease than teeth.

When can I place teeth on my implants?

The lower jaw generally requires a 3-month healing period for the implants while the upper jaw may need 6 months. The bone in the upper jaw is of poorer quality (softer). In the meantime a temporary prosthesis can be worn to replace the missing tooth or teeth. These are usually removable. Care must be taken to make sure they fit correctly. The temporary partial denture cannot hit on the implant when closing or chewing. This can cause failure of the implant by not allowing the bone to attach. This is called a failure to osseointegrate.

Full dentures can also be worn over the implants. The dentures are relined with a soft material. Sometimes the patients are asked to leave their denture out for one week after the surgery to allow for healing of the gum incisions.

Does it hurt?

The procedure is usually less painful than a tooth extraction. A high percentage of patients do not need any pain medicine after implant surgery.

How long do they last?

There are a number of factors that can effect this:

Generally implants are very stable and predictable. Under ideal conditions, they can last a lifetime. The first ones placed by Professor Branemark have been functioning for more than 30 years.

Wear and tear can take place. Abutment screws can break and the crowns or denture teeth can wear out. There will be maintenance required on the implants and teeth (crown, dentures, etc.) over the years.

What are abutments?

Abutments are what attaches to the implant and sticks in the mouth. There are different sizes and shapes. Your restorative dentist will pick the appropriate one for your case. The teeth will fit onto the abutment.

Can anybody have dental implants placed?

The jaw shape (anatomy) needs to be examined by the surgical specialist. Adequate ridge width and height are required for implant support. Bone melts away when teeth are lost. The maxilla (upper jaw) has air cavities in the posterior (back) portion. These are called the maxillary sinuses. They enlarge when the back teeth are lost taking away bone height that could support implant placement. The maxillary (upper jaw) anterior ridge and mandibular (lower jaw) ridge can also resorb (melt) when teeth are lost resulting in a loss of height and width. This may require the addition of bone through various grafting procedures. This allows the surgeon to place the implants in their ideal location.

Age is only a factor in the growing patient. As a person matures, the jaw bone and teeth move down and forward in the upper jaw, and up and forward in the lower jaw. Implants are ankylosed (fused to the bone) and do not move with the growing jaw. This means that the implant will eventually become malpositioned if placed during jaw growth. A general rule for the minimum age for implant placement is 16 years of age for girls and 18 years of age of boys.

Old age is not a factor as long as the patient is stable healthwise. Uncontrolled diabetes and heavy steroid therapy are contraindications.