A dental implant is an artificial tooth root replacement and is used in prosthetic dentistry. There are several types. The most widely accepted and successful is the osseointegrated implant, based on the discovery by Swedish Professor Per-Ingvar Brånemark that titanium could be successfully incorporated into bone when osteoblasts grow on and into the rough surface of the implanted titanium. This forms a structural and functional connection between the living bone and the implant. A variation on the implant procedure is the implant-supported bridge, or implant-supported denture

Procedure

A typical implant consists of a titanium screw, with a roughened surface. This surface is treated either by plasma spraying, etching or sandblasting to increase the integration potential of the implant. At edentulous (without teeth) jaw sites, a pilot hole is bored into the recipient bone, taking care to avoid vital structures (in particular the inferior alveolar nerve within the mandible).

This pilot hole is then expanded by using progressively wider drills. Care is taken not to damage the osteoblast cells by overheating. A cooling saline spray keeps the temperature of the bone to below 47 degrees Celsius (approximately 117 degrees Fahrenheit). The implant screw can be self-tapping, and is screwed into place at a precise torque so as not to overload the surrounding bone. Once in the bone, a cover screw is placed and the operation site is allowed to heal for a few months for integration to occur.

After some months the implant is uncovered and a healing abutment and temporary crown is placed onto the implant. This encourages the gum to grow in the right scalloped shape to approximate a natural tooth's gums and allows assessment of the final aesthetics of the restored tooth. Once this has occurred a permanent crown will be constructed and placed on the implant.

An increasingly common strategy to preserve bone and reduce treatment times includes the placement of a dental implant into a recent extraction site. In addition, immediate loading is becoming more common as success rates for this procedure are now acceptable. This can cut months off the treatment time and in some cases a prosthetic tooth can be attached to the implants at the same time as the surgery to place the dental implants.

Complementary procedures

Sinus lifting is a common surgical intervention nowadays. The Oral surgeon thickens the adequate part of atrophic maxilla towards the sinus with the help of bone transplantation or bone expletive substance and as a result of it we enable the implantation.

Bone replacement will be necessary in case of lack of adequately thick bone, which could hold the implant. Substances used during the process of bone replacement can be the own bone of the patient (auto transplantation) or artificially produced bone expletive substance. The intervention can be carried out in the maxilla and mandible as well.

Considerations

For dental implant procedure to work, there must be enough bone in the jaw, and the bone has to be strong enough to hold and support the implant. If there is not enough bone, be may need to be added with a procedure called bone augmentation. In addition, natural teeth and supporting tissues near where the implant will be placed must be in good health.

In all cases, what must be addressed is the functional aspect of the final implant restoration, the final occlusion. How much force per area is being placed on the bone implant interface? Implant loads from chewing and parafunction can exceed the physio biomechanic tolerance of the implant bone interface and/or the titanium material itself, causing failure. This can be failure of the implant itself (fracture) or bone loss, a "melting" of the surrounding bone.

The restorative dentist must first determine what type of prosthesis will be fabricated. Only then can the specific implant requirements including number, length, diameter, and thread pattern be determined. In other words, the case must be reversed engineered by the restoring dentist prior to the surgery. If bone volume or density is inadequate, a bone graft procedure must be considered first.

Computer simulation software based on CAT scan data allows virtual implant surgical placement based on a barium impregnated prototype of the final prosthesis. This predicts vital anatomy, bone quality, implant characteristics, the need for bone grafting, and maximizing the implant bone surface area for the treatment case creating a high level of predictability. Computer cad/cam milled or stereo lithography based drill guides can be developed for the implant surgeon to facilitate proper implant placement based on the final prosthesis occlusion and aesthetics.

Success rates

Dental implant success is related to operator skill, quality and quantity of the bone available at the site, and also to the patient's oral hygiene. Various studies have found the 5 year success rate of implants to be between 75-95%. Patients who smoke experience significantly poorer success rates.

Failure

Failure of a dental implant is usually related to failure to osseointegrate correctly. A dental implant is considered to be a failure if it is lost, mobile or shows peri-implant bone loss of greater than one mm in the first year after implanting and greater than 0.2mm a year after that. Dental implants are not susceptible to dental caries but they can develop a periodontal condition called peri-implantitis where correct oral hygiene routines have not been followed. Risk of failure is increased in smokers. For this reason implants are frequently placed only after a patient has stopped smoking as the treatment is very expensive. More rarely, an implant may fail because of poor positioning at the time of surgery, or may be overloaded initially causing failure to integrate.

Contraindications

There are no absolute contraindications to implant dentistry, however there are some systemic, behavioral and anatomic considerations that should be considered.

Uncontrolled type II diabetes is a significant relative contraindication as healing following any type of surgical procedure is delayed due to poor peripheral blood circulation. Anatomic considerations include the volume and height of bone available. Often an ancillary procedure known as a block graft or sinus augmentation are needed to provide enough bone for successful implant placement.

There is new information about Bisphosphonates (taken for osteoporosis and certain forms of breast cancer) which put patients at a higher risk for developing a delayed healing syndrome called osteonecrosis. Implants may be contraindicated in patients who take this class of drug.

Bruxism (tooth clenching or grinding) is another contraindication. The forces generated during bruxism are particularly detrimental to implants while bone is healing; micromovements in the implant positioning are associated with increased rates of implant failure. Bruxism continues to pose a threat to implants throughout the life of the recipient. Natural teeth contain a periodontal ligament allowing each tooth to move and absorb shock in response to vertical and horizontal forces. Once replaced by dental implants, this ligament is lost and teeth are immovably anchored directly into the jaw bone. This problem can be minimized by wearing a custom made mouthguard (such an NTI appliance) at night.

Bone grafting is a surgical procedure that replaces missing bone with material from the patient's own body, an artificial, synthetic, or natural substitute. Bone grafting is used to repair bone fractures that are extremely complex, pose a significant risk to the patient, or fail to heal properly.

Tissue source

Autologous bone is typically harvested from the iliac crest of the pelvis.

Allograft bone from cadavers or live donors may also be used. Allograft is typically sourced from a bone bank.

Grafts may be made from hydroxylapatite, a naturally occurring mineral that is also the main mineral component of bone.

Synthetic grafts may be made from bioactive glass.

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. AnADA 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.

When you get implants, more than one dental professional may treat you. The implants will be placed in your jawbone by a surgeon (an oral surgeon or a periodontist). A prosthodontist or general dentist will make your crowns, bridges or dentures, which will look like natural teeth. The surgeon will coordinate your treatment with your general dentist or prosthodontist to decide what implants to use, how many implants you need and where they should be placed.

Because there are different types and manufacturers of implant devices, the approach your dentists use may differ from the description presented here. The following describes the steps that a dentist typically takes when placing an implant.

Before Placing an Implant
Not all people are good candidates to get dental implants. A person who is most suitable is someone who is in good health, has healthy gums, and has enough bone in his or her jaw to allow an implant to be placed in the jawbone. To determine if you are suitable to get an implant, you will have to be examined by a dental professional.

Some people are interested in getting implants to replace teeth that have been missing for a number of years. Others may need implants to replace teeth that were extracted recently because of severe decay, periodontal (gum) disease, infection or injury. In some cases, the teeth can be extracted and the implant placed at the same time. However, if you have a severe infection in a tooth root or your gums, your dentist may wait a few months after removing the teeth to allow the area to heal.

Before a dental implant is placed, you may need to have the bone in the area built up to increase the chance of success. This is a common procedure called bone grafting or augmentation. You may have the bone graft done and get the implants at the same time, but your dental specialist may decide to do the bone-graft procedure first and give the bone time to heal before placing the implants. If the bone graft is done first, you will need 4 to 12 months to heal before having the implants placed in your jawbone. However, you can wear your dentures or bridge during this time, so you won't be without teeth.

Placing the Implants
Most implants are placed using a two-step process, although some newer implants can be placed in one step. What follows, is a description of how the two-step process works.

The First Surgery 
You may be given antibiotics and pain medication to take before the surgery. Your dentist will use local anesthesia for the procedure and will offer you sedation if you want it. You can be sedated by taking medication by mouth, or the medication can be delivered through an intravenous line (a needle attached to a small tube placed in a vein in your arm).

Illustration of an implant in the bone

See photos

To place the implants, the surgeon first will make an incision (cut) in your gums to expose the bone. He or she then will drill a hole in the bone for the implant, and place the implant in the hole. The surgeon probably will take an X-ray of the area to make sure the implant is where it should be. The surgeon will then stitch (suture) your gum closed over the implant. The time required for this procedure depends on the number of implants being placed and whether or not bone grafting is being done at the same time. In most cases, placing a single dental implant requires about one hour. You will feel some pain after this procedure. The level of discomfort depends on the person, but generally it has been described as relatively mild.

If the implant is placed in the front of your mouth, your dentist will give you a temporary denture or bridge so that you do not have to be without teeth. He or she will discuss options with you before the surgery.

After your surgery, your surgeon will give you antibiotics and pain medication. He or she also will give you instructions to follow. These will include:

  • Don't spit, suck on straws or smoke. This can dislodge blood clots and slow healing.
  • Eat only soft food to avoid injuring your gum tissues.
  • Don't try to clean the implant area for the next one to two weeks, but clean the rest of your mouth normally. Your dentist may give you an antibacterial rinse to help keep the area clean.

You will return to the surgeon 7 to 10 days later to have your stitches removed.

After the implant is placed in your jaw, you will have to wait several months for the bone to bond with the implant. This usually takes 3 or 4 months in the lower jaw and 5 or 6 months in the upper jaw. During this time, the head of the implant usually remains hidden under your gum.

The Second Surgery 
After the implants have integrated (attached) with the surrounding bone, you are ready for the second surgery. After giving you local anesthesia, your surgeon will make a small incision in the gum to expose the implant. He or she will remove a protective screw from the implant and replace it with a metal healing abutment (collar). The healing abutment looks like a small metal cylinder that sits above your gums in the area where your tooth would be and maintains the space so that the gums heal correctly around the implant.

In a very small percentage of cases, the implants will not have successfully bonded with the bone. If this happens, your dentist either can remove the implants and immediately replace them with slightly wider ones, or remove them and allow the area to heal for several months before making a second attempt.

Some dentists are now using one-stage implants. These implants are placed in the jaw and remain exposed in the mouth so that no second surgery is needed.

Restoration 
Generally, you will go to your dentist or prosthodontist two or three weeks following the second surgery to start the process of having your crown, bridge or denture made.

Complications From Surgery
Any surgery carries the possibility of complications. Complications of implant surgery include bleeding, infection and injury to nerves, sinuses (located above your upper teeth) or nasal cavity.

When implants are used to replace lower teeth, your dentist could nick the nerve that runs through the jawbone during drilling. This can cause pain or numbness. If numbness occurs, it usually affects the lower part of the lip and chin or one side of the tongue. It can last for several months until the nerve heals or it may be permanent.

In the upper jaw, there is the possibility of drilling through the jawbone into one of your sinuses or nasal cavity, which could result in an infection. To avoid this, special X-rays will be taken prior to your surgery will help the surgeon to determine where the nerves, sinuses and nasal cavity are located.

Implant Failure
Implant surgery is successful more than 90% of the time.

Occasionally, an implant fails to bond with the surrounding bone. This is usually discovered at the second stage surgery when the implant is uncovered and the surgeon finds it is loose. In this case, the “failed” implant has to be removed. Another implant can be placed either immediately or at a later visit.

Potential reasons for implants failing to integrate with surrounding bone include:

  • Surgical trauma
  • Infection around the implant
  • Smoking — This appears to decrease blood flow to the healing gums and bone, which could interfere with the bonding process.
  • Lack of healthy bone — If there is not enough bone for the implant to remain stable, the implant may move around within the bone and bonding will not occur.
  • Titanium allergies — These are extremely rare.

Problems also can develop years after implants are placed. For example, just like natural teeth and gums, the gums around implants can become infected by bacteria, leading to a form of periodontal disease called periimplantitis. If left untreated, this condition can cause bone loss, which could cause the implant to become loose and have to be removed. Generally, this situation can be treated using procedures that are very similar to those used to treat periodontal disease affecting natural teeth.

Another type of complication that can happen over time is the implant-supported restoration (crown, bridge or denture) can break, or the implant itself can fracture. This usually happens if your bite (the way your teeth come together) is not aligned properly. If your bite is off, too much force might be placed on the restoration or implant. Broken restorations often can be repaired. However, a fractured implant has to be removed.

A broken implant or an implant that fails because of an infection can be replaced with a new implant.

Who Is an Implant Candidate?

If you're interested in replacing your missing teeth, or a single missing tooth, dental implants may be an option for you. Not everybody, however, is a good candidate for implants. A good candidate should have the following:

  • Good health
  • Healthy gums
  • Enough bone to anchor the implants in the jaw — Some people who have lost bone in their jaw still can get implants, but first the bone must be rebuilt using special procedures.
  • Be committed to taking very good care of the implanted teeth and surrounding gums — Daily brushing and flossing are essential. Regular visits to the dentist for follow-up are also important.

Some people may not be good candidates for implants. They include:

  • Young patients whose jawbones have not developed completely
  • Pregnant women
  • Heavy smokers — Smoking impedes healing in the mouth and can reduce the likelihood that implants will be successful.
  • Alcohol or substance abusers
  • Patients who have received high-dose irradiation of their head or neck
  • People with chronic diseases or systemic problems, including high blood pressure, diabetes, connective-tissue diseases, hemophilia and significant immune deficiencies, among others — You still may be a good candidate for implants even if you have one of these conditions. It depends on the extent and severity of the condition.
  • Patients who take certain medications such as steroids or drugs that suppress the immune system
  • People who severely grind or clench their teeth — These habits can place too much pressure on the implants and increase the risk of failure.

Your dentist can evaluate you to see if you would be a good candidate to receive implants.

Being Evaluated
Implant therapy involves a team that includes the surgeon (usually an oral surgeon or a periodontist) who places the implant or implants, and the restorative dentist (a general dentist or prosthodontist) who specializes in making crowns and bridges. The restorative dentist will make the crowns, bridges or dentures that will be supported by the implant or implants. The first step in your treatment is to make an appointment with one of these professionals for an evaluation. He or she will coordinate your treatment with the other members of the implant team.

Your initial evaluation will include an examination of your mouth and teeth and a thorough review of your medical and dental histories. You mouth will be X-rayed, and you might have a computed tomography (CT) scan, which will provide information on your bone density (how much bone you have in your jaw) and the shape of your jaw. Finally, you'll discuss the options available to you with your dentist, talk about the procedure, and its cost and possible complications. Your dentist will work with you to develop a treatment plan that is customized to your particular needs and preferences.

DID YOU KNOW?

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