Introduction

A dental implant is a surgically implanted device. It replaces the lost roots of a tooth to which an artificial tooth, partial denture, or denture can be attached. Traditional procedures for replacing missing teeth include partial dentures, complete removable dentures, or fixed bridges that attach to existing teeth or rest on the gums. However, for individuals who have a weakened jawbone, who cannot manage removable dentures or cannot properly chew food, implants maybe the best option.

Background

In dentistry, the word Implant refers to a device that is set into, or sits on top of the jawbone. An Abutment is the device attached to the implant and is the contact between the implant and the prosthesis. The artificial tooth (or teeth) attached to the abutment is called a Prosthesis.

The implant procedure for replacing a tooth is a three-step process. The first step is the placement and subsequent healing (integration) of the implant to the jawbone. Next an abutment is attached to the implant. Finally, a prosthesis is attached to the abutment. The same procedure is followed when multiple implants are used for a partial or full denture.

Implant designs fall into three main categories: endosseous, subperiosteal and transosteal. Within the categories, 50 implant subtypes exist. Abutments are also numerous in design. They range from fixed (cemented) and fixed-removable (screw or clip retained) designs, to removable affixed by o-rings, clips, or snap designs. The most common implants used today are endosseous implants. These implants are surgically inserted into the jawbone and fuse with the bone. The most common endosseous implant used today is the rootform implant.

Rootform implants are considered by some clinicians as the standard of care in oral implantology. The implant, a screw shaped like the original root, is screwed into the patient's jawbone. The screw's shape and size are based upon the tooth being replaced and/or the size and shape of the remaining jawbone. The implant is generally made out of titanium alloys, aluminum oxide, vitallium, commercially pure titanium or sapphire. Once the implant has been placed into the jawbone, a few months is required for the implant and the bone to fuse. This fusing creates a solid, secure implant to which an abutment can be attached.

Before the prosthesis phase, a temporary crown or healing abutment is attached to the implant for up to eight weeks. Gum tissue grows around the temporary crown and into the shape that the new tooth will have. After the implant has fused, an impression of the tissue shape and the implant is taken. From this impression a permanent tooth is fabricated. The permanent-fabricated tooth is then cemented to a custom abutment that is then screwed onto the implant.

Other types of implants are used when specific reasons have been identified. Primarily, these implants are used for weak and/or broken jaws and are not commonly used. These include ramusframe implants which are surgically implanted into the lower jawbone, subperiosteal implants which rest on top of the jawbone but under the gums, and the transosseous implants which pass through the entire jawbone.

Who should have implants?

Any toothless area can be considered for dental implants. Determining whether implants are an option and the type of implants to use include: the patient's requirements and expectations, the amount of additional work needed (i.e., bone grafting), the dentist's skill, and the long-term prognosis. A discussion with a dentist is required to decide if the toothless area is a good location for an implant.

Reasons for not having an implant include:

· inadequate bone space

· existing bone that does not meet implant criteria

· diabetes, pituitary and adrenal insufficiency and hypothyroidism, which may cause considerable healing problems

· an inability to fight infections

· diseases such as tuberculosis and sarcoidosis

· heart disease that may cause healing and management problems

· bone disease such as histiocytosis X, Paget's disease and fibrous dysplasia because of poor implant and bone fusion

· a history of uncontrolled bleeding

· certain types of Periodontal disease

Also, a person who smokes regularly will usually have a lower success rate than nonsmokers.

Complications

Complications after implant surgery are usually of short duration and generally occur within the first few days of the implant placement. Complications usually include swelling, pain, bleeding, possible infection, partial numbness at implant sites, and nausea. Nerve disturbances, which may be permanent, and bone fracture can also occur. Complications can occur during fusing, when sites and implants become exposed or are intentionally left exposed, therefore, oral hygiene becomes an important factor in reducing complications.

Rejection occurs in about one out of 20 implants. Causes of rejection are sometimes unknown, but disturbance of the site during the healing process can be a factor. Overheating of the bone or poor surgical technique during surgery may also be a cause of rejection. It is known that smokers have an increased chance of rejection.

Complications can also result after the implants, abutments, and prostheses are put into use. Although slight marginal bone loss commonly occurs with dental implants, it can also occur due to excessive loads on the implants caused by heavy chewing or the grinding of teeth. Fractures of the implant or abutment components can also occur, and a night guard may be needed to protect the implant, abutment and new prosthesis.

All other complications with implants are usually associated with the prosthesis. The most common complication is screw loosening. Other complications include: fracturing of the screw, porcelain or acrylic materials, and metal frameworks; clip and/or attachment loosening and fracturing; and placement realignments after surgery. Higher failure rates were found in shorter implants and were seen more often in certain bone types than in others.

Overall, approximately 95% of implants survive surgical and abutment placement. Approximately 90% are still in use after five years and 85% are still being used between five and 10 years. Although data are limited, more than 75% survive beyond 10 years.

Benefits

Benefits of having a dental implant include not having to alter adjacent teeth because a bridge will be attached to them. Another benefit is not experiencing the looseness of traditional dentures. Implants are easier to clean around than the cleaning and flossing required for bridges. For some people, knowing that they have natural looking, and feeling teeth are the most important benefits. In severely damaged or weak-boned jaws, some implants can strengthen the jaw and become the only option for full mouth reconstruction.

Cost

Cost to the consumer for dental implants are dependent upon the number of implants, type and design of the implant, and the materials used. Generally, the cost of an individual rootform implant (one tooth) in Minnesota is approximately $1,600. For total mouth reconstruction (up to 14 implants), the cost approaches tens of thousands of dollars.16 In comparison, a standard one-tooth, 3 unit bridge costs approximately $2,000, with an estimated cost of $650 per additional tooth added.

Nationally, the cost varies from approximately $1,000 for one implant, to a high of $80,000 for full mouth reconstruction. The estimated cost for inserting, maintaining, and replacing a prosthesis for an implant is twice the cost of the implant itself, and ten times greater than traditional dentures. Traditional crowns and dentures have lower costs associated with them.

In a mid-1990 study, total actual costs were compared using four different treatments for persons having persistent problems with their traditional lower denture. The options included: a lower overdenture on two permucosal (endosseous) implants, a lower overdenture on a transmandibular (transosseous) implant, a new lower traditional denture after surgical reconstruction, and a new lower traditional denture without any reconstruction.

Total actual costs included examinations, surgery, hospital costs, prosthodontics (jaw and mouth reconstruction), materials, and overhead. The cost for each treatment was approximately: $7,605 to $8,830 for the transmandibular; $3,711 for the endosseous; $3,808 for preprosthetic surgery with a new traditional denture; and $1,205 for a new traditional denture (without preprosthetic surgery).