Dental Implants -

What are they? / The component parts of an implant (fixture, abutment, prosthesis). / Basic cases (conditions, situations) where implants should not be placed.

A) What is an implant?

Dental implants are mechanical devices that have been designed to substitute for individual missing teeth. They function as an artificial tooth root, on top of which some type of dental prosthesis (a dental crown, bridge or denture) can then be placed.

A dental implant replacing a molar.

A dental implant used to replace a molar.

"Endosseous root-form" tooth implants.

The most common kind of implant placed by dentists is the "endosseous root-form" type.

  • The term "endosseous" refers to the fact that the implant is embedded within bone.
  • The term "root form" refers to the fact that the shape of the implant is somewhat similar to the shape of a natural tooth's root. (This isn't precisely accurate in the sense that some teeth have multiple roots. - See animation.)

"Osseointegrated" implants.

The term "osseointegrated" (or "osteointegrated") refers to the fact that there is a direct connection (fusion) between the surface of the implant and living bone tissue. Virtually all endosseous root-form implants are the osseointegrated type.


B) The component parts of an implant.


The fixture and abutment portions of a dental implant.

The fixture and abutment parts of a dental implant.

#1) The implant "fixture."

The fixture is that part of the implant that's embedded in and becomes fused with the jawbone.

It's the portion that lies below the gum line and, for all practical purposes, can be considered to be an artificial tooth root.

a) Fixture construction.

Osseointegrated implant fixtures are made out of the metal titanium. It may either be "commercially pure" (over 99.5% pure) or an alloy (titanium combined with aluminum and vanadium, so to improve strength and fracture resistance).

Fixtures can have a hollow or solid, and then cylindrical or screw-shaped design.

How an implant is restored.

Component parts of an implant: a) Implant fixture. b) The abutment. c) The crown.

b) Special surface treatments.

The metal surface of the fixture portion of an implant may be smooth. As an alternative, some manufacturers grit-blast, machine or etch this surface so to roughen it up at a microscopic level.

Doing so increases the total external surface area of the fixture, thus increasing the amount of bone-to-implant fusion that takes place. (The need or benefit of this extra treatment is disputed.)

c) Special fixture coatings.

The surface of a fixture is sometimes coated with a special bone-regeneration material such as hydroxyapatite. Some manufacturers feel that this helps the osseointegration (fusion) process to take place more rapidly. (The need for this is also disputed.)

X-rays showing the stages of dental implant restoration.

Components: 1) Implant fixture. 2) Abutment. 3) Crown.

#2) The implant abutment.

The abutment portion of a tooth implant is that part that lies at and above the gum line. It's the part that supports and secures the dental work (crown, bridge, denture) that's placed on it.

The abutment is typically not added to the implant fixture (screwed on) until after the osseointegration process (implant-to-bone fusion) has taken place.

(In our animation above, Image #2 shows an x-ray of an implant fixture with its abutment in place.)

#3) The dental prosthesis.

The dental prosthesis refers to the dental work (crown, bridge, denture) that the implant supports.

Depending upon its design, it may be cemented or screwed (i.e. crowns, bridgework), or else clipped or snapped (i.e. dentures), into place.

(In our animation above, Image #3 shows an x-ray of an implant that supports a dental crown.)


Who makes a good candidate for a dental implant?

Once a decision has been made that an implant will be considered as a treatment option, the dentist must make a determination about the patient's suitability for it.

Factors that must be evaluated include:

  1. The patient's health (medical conditions, medicines, age).
  2. Patient habits (smoking, tooth grinding, poor oral hygiene).
  3. Jawbone quantity and quality.


1) Medical considerations.

a) Medical conditions that contraindicate the placement of dental implants.

There are a number of conditions that typically bar elective oral surgery, and therefore preclude the placement of dental implants. Some of them include:

  • Recent myocardial infarction (heart attack) or cerebrovascular accident (stroke).   |   Valvular prosthesis (artificial heart valve) surgery.   |   Immunosuppression (a reduction in the efficacy of the immune system).   |   Bleeding/Clotting problems.   |   Active treatment of malignancy (cancer).   |   Drug abuse.   |   Psychiatric (mental) illness.
Other considerations.

Clearly any condition that places the patient at risk for further health deterioration must be resolved before an elective dental procedure such as this one is considered.

b) Medical conditions that may interfere with an implant's success.

Any condition that impairs the normal healing process can interfere with the successful placement of a dental implant.

As an example, uncontrolled diabetes mellitus delays the process of wound healing, and therefore people who have this condition do not make good candidates.

However, the mere presence of a disease does not necessarily preclude placement, or significantly alter the implant's long-term outlook, if the medical condition is controlled by treatment or medication.

c) Medicines.

The medicines that a patient takes must be evaluated before a dental implant is placed.

A dentist will need a complete listing of all of the medicines and supplements that their patient takes.

These items must be evaluated both in light of the effect that they may have upon the placement procedure as well as the healing process that takes place afterward.

Additionally, the dentist must evaluate these drugs in light of how they may interact with those drugs that the dentist typically utilizes when performing their work.

Drugs of concern.

High on a dentist's list of concerns will be those drugs that are utilized in the treatment of cancer, those that inhibit blood clotting and also bisphosphonates (a class of drugs used in the treatment of osteoporosis).

d) Age considerations.

Young adults.

As a general rule, placing tooth implants should be delayed until the age of 18 to 19 years. This age generally correlates with that time frame when an adolescent's jaw growth and development can be considered to be complete.

Advanced age.

Advanced age doesn't necessarily contraindicate the placement of dental implants but it can present challenges.

A failure to practice effective oral hygiene, a phenomenon that often accompanies advanced age, places the long-term survival of an implant at risk.

However, in the case where an elderly patient has trouble wearing or cannot tolerate a removable appliance (partial or full denture), dental implants may be a reasonable option and one that makes it possible for them to maintain adequate nutrition where otherwise they could not.


2) Patient habits that may conflict with implant placement.

a) Smokers may have lower long-term implant success rates than nonsmokers.

Many (but not all) studies have reported that the long-term success rate of tooth implants of smokers is lower than for those who don't.

Smoking may compromise the long-term success of dental implants.

Clearly, among smokers there will be a wide variation in the way each person practices their habit. And this may be the reason why the findings of some studies conflict with others.

It is, however, thought that smoking tends to reduce bone density and bone quality, as well as impair the wound healing process. And it's easy to see how these factors could affect the long-term outlook for a dental implant.

This does not mean that smoking should be considered to be an absolute contraindication for placement. But smokers need to realize that if they continue their habit they're likely at higher risk for implant failure.

If you do smoke.

Some suggested treatment protocols call for smoking cessation one week prior to, and then eight weeks following, the placement procedure. Thus helping to minimize the effect it may have on the early stages of the implant healing process (osseointegration).

b) Bruxism (tooth clenching and grinding) may compromise dental implant success.

Bruxism is a term that refers to the habit of clenching and grinding one's teeth.

The act of bruxing can result in excessive forces being directed to the bone-implant interface. And this type of biomechanical overload has been correlated with tooth implant failure.

However, a habit of bruxing should not necessarily be considered to be a contraindication for placement. But if a patient is not willing to address this issue, either by controlling their habit on their own or wearing a mouth guard appliance that can help to lessen its effects, an implant may make a poor choice.

c) Poor oral home care.

Some research studies have reported a correlation between ineffective brushing and flossing and dental implant failure. This association, however, has yet to be definitively established.

Peri-implantitis.

It is established that if bacteria are allowed to colonize in the gum tissue surrounding an implant, their presence can lead to an inflammatory response called peri-implantitis. If this condition is left untreated, it can lead to a loss of supporting bone, a loss of osseointegration (bone-to-implant fusion) and ultimately implant failure.

 

 
 
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