Tooth Implants and Procedures

Welcome. Our topic "Dental Implant" is organized into the following subsections and topics

What are tooth implants (dental implants)?

Dental implants (tooth implants) provide a way by which one or more missing teeth can be replaced. Dental implants function as "artificial tooth roots" on top of which a dental prosthesis, such as a dental crown, bridge or denture, can be placed. Our pages will help you understand what type of dental patient makes a good candidate for tooth implants and what factors a dentist takes into consideration when evaluating the prospective dental implant patient. Our pages also illustrate the procedure a dentist follows when they perform dental implant surgery.

What are dental implants (osseointegrated tooth implants)?

The most common type of tooth implant (dental implant) that is placed today is the "endosseous root form implant." These objects are cylindrical or screw shaped devices that are positioned into a person's jawbone. In essence, a dental implant acts as an "artificial root" on top of which a dental crown or one end of dental bridgework can be secured.

The term "endosseous" refers to the fact that the implant is embedded in the jawbone and penetrates through the gum tissue. The term "root form" refers to the fact that this type of implant is somewhat similar in shape as the root of a natural tooth. (This isn't precisely accurate in the sense that some teeth have multiple roots.)

Root form endosseous tooth implants are also described as "osseointegrated (osteointegrated) implants." The term osseointegration refers to the fact that there is a direct fixed connection between the dental implant and living bone. (More precisely, the bone is in direct contact with an implant with no Intervening layer of connective tissue at the light microscopic level.)

A tooth implant is comprised of three components:

1) The dental implant fixture.

The fixture is that portion of the implant that is embedded in and becomes anchored to (osseointegrated with) the jawbone. It is that portion of the dental implant that lies below the gum line. For all practical purposes the fixture can be considered to be an "artificial root."

Implant fixtures are constructed out of titanium and typically have a hollow or solid, cylindrical or screw shaped design. Each manufacturer will utilize a proprietary surface treatment with their implant fixtures. As a result, fixture surfaces are often machined, grit-blasted, etched or plasma sprayed. The purpose of these treatments is to microscopically roughen the fixture's surface and therefore increase its total surface area, thus providing a greater amount of bone to implant contact.

The surface of a fixture may also be coated with a biocompatible, bone-regeneration material such as hydroxyapatite. The thought associated with this coating is that it may enhance the osseointegration process by allowing it to occur at a more rapid rate. The optimal overall surface preparation, however, is still a point of debate.

2) The dental implant abutment.

The abutment aspect of a tooth implant is its stub portion that lies at and above the gum line. The dental crown or dental bridgework that the implant supports rests on top of the implant's abutment. An abutment is usually attached to (screwed into) the implant fixture 3 to 6 months after it was initially placed.

3) The dental prosthesis.

The dental prosthesis refers to the dental crown or dental bridgework that the implant supports. Depending on how this dental work has been designed, it can either be cemented or screwed into place.

Evaluating the suitability of a patient for tooth implants:

The dental examination.

Every dental implant case needs to start with an examination.

Before a dentist can determine that a patient is a suitable candidate for the placement of a tooth implant they will need to perform a clinical examination. This examination will need to include radiographs (x-rays) of the patient's teeth and jawbones.

The tooth implant examination: Evaluating the patient's jawbones.

The long-term success of a dental implant will be highly dependent upon the bone in which it is placed. Because of this the treating dentist will need to examine the patient's jawbones so to determine that both the quantity and quality of the bone in the region where the tooth implant will be positioned is adequate.

This examination will need to be twofold. One aspect will involve the visualization, palpation, and measurement of the jawbones. The other will involve the use of dental radiographs (x-rays). In many cases a combination of a panoramic and multiple periapical radiographs (the type of x-rays typically taken in dental offices) will be satisfactory for this examination. In some cases, however, the dentist may feel that they need the information that only a CT (computed tomography, CAT scan) can provide.

The patient's jawbone must offer an adequate quantity and quality of bone.

The dentist must find that there is an adequate quantity of bone in the region of the planned tooth implant and that this bone is of sufficient quality. Making this determination involves evaluating the shape of the bone (both width and height). It also involves evaluating the density of the bone (both outer cortical and inner medullary bone).

There can be situations where the treating dentist will find that the bone in the region of the planned implant is not adequate. This deficiency can be naturally occurring, such as that bone resorption (bone loss) that takes place in those regions where teeth have been extracted. This type of defect is most common in those cases where multiple teeth were extracted many years previously.

In other cases the bone deficiency can be attributed to dental disease, such as bone loss due to the effects of advanced periodontal disease (gum disease). Since the success of a dental implant will be greatly dependent upon the bone in which it is placed, the treating dentist may feel that it is necessary for them to perform a bone grafting procedure for their patient (such as a sinus lift) so to replace missing bone or add to existing bone.

As the dentist examines the patient and reviews their x-rays, they will search for other potential complications. The location of various anatomical structures, such as sinuses, nerves, blood vessels and the roots of adjacent teeth must be identified. This is important because tooth implants must be positioned in a fashion where they are suitably distant from these objects.

The dentist must also evaluate for evidence of pathology within the jawbone (such as tumors, cysts or bone disease). Impacted teeth and the presence of tooth root fragments (remnants of past extractions) need to be identified and removed as the dentist feels is indicated.

The tooth implant examination: Evaluating the soft tissues of the mouth.

A portion of the dentist's clinical examination of the dental implant candidate will involve the evaluation of the soft tissues of their mouth. The dentist must determine that these tissues are free of pathology and appear to be health. They must also evaluate both the quantity and type of the gum tissue in the immediate area where the tooth implant will be placed so to determine if it is adequate.

The dental implant examination: Evaluating the patient's oral home care habits.

The dentist's clinical examination must also involve making a judgement about the effectiveness of the patient's oral hygiene habits. Some dental research has reported an association between ineffective tooth brushing and flossing and dental implant failure. This association, however, has yet to be definitively established.

It is known 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 implant osseointegration and ultimately implant failure. A failure to practice good oral hygiene may be due to a simple lack of motivation or, at the other extreme, a true deficit in the patient's manual dexterity, possibly due to advanced age or a debilitating medical condition.

What procedure does a dentist follow when they place dental implants?

The following pages illustrate the set of steps that dentists typically follow when they place dental implants. However, variations on this basic technique do exist. With a little advanced preparation on the dentist's part, in most cases a person's dental implant surgery can be performed right in their dentist's office.

1) The dentist will access that portion of the jawbone where the dental implant will be placed.

Initially the dentist will need to access the bone that lies in the region where the tooth implant will be placed. To do so, the dentist will create a few incisions in the patient's gums that outline two separate flaps of gum tissue. The dentist will then use a hand instrument to push and peel each flap of gum tissue back, so the bone that lies underneath is revealed.

Once the gum tissue flaps have been raised, the dentist will evaluate the shape of the bone that has been exposed. Ideally this area of bone should to be relatively flat and smooth on top. If the dentist feels that the bone does not meet these conditions, they will use their dental drill to contour the bone so it takes on the needed shape.

{ In those instances where there is no question about the suitability of the gum tissue and bone in the region where the tooth implant will be placed and no concerns about being able to suitably position the implant itself, there is a chance that the surgeon can access the jawbone by way of using a tissue punch instead creating tissue flaps. This technique involves using a circular punch to create a hole through the patient's gum tissue (one slightly larger in diameter than the planned implant). The implant drilling and placement process can then be performed through this hole. }

What types of anesthesia are utilized with dental implant surgery?

Most dental implant surgeries can be performed with the dentist just administering a local anesthetic. While the general public typically refers to local anesthetic as "novocaine," it has not been used widely in dentistry for some decades. At this point in time it is most likely that the local anesthetic that a dentist will administer is lidocaine.

As you probably know, local anesthetics are administered by way of an injection (shot). In general, the anesthetic is placed in the "local" area where its effect is required. This same local anesthetic technique is the one that is used when a dentist places a filling or extracts a tooth for a patient.

2) The dentist will identify the proper location for the dental implant.

Once the bone has been accessed, the dentist will ultimately use a series of drills, each of increasing diameter, to prepare a hole into which the dental implant will be placed.

To start this process, the dentist will first use a small round bur (a dental drill bit) to make a divot in the bone. This divot both penetrates the hard, outermost layer of bone and helps to insure that the placement of the pilot drill (the first drill bit used deep inside the jawbone) is easily centered in the implant site.

3) The dentist will enlarge the hole for the tooth implant.

At this point the dentist will use a series of bone drills, each of increasing diameter, to enlarge the pilot hole to a final diameter that is capable of accommodating the tooth implant that has been selected for placement.

{ The diameter of the implant chosen for placement is dependent upon the dimensions of the bone at the implant site. In general, the dentist will want to use as large a diameter tooth implant as is reasonably possible. This is because larger diameter implants are stronger and distribute their loads to the surrounding bone more favorably than comparative smaller ones.

Most dental implants that are placed are approximately 4mm in diameter. Some dentists consider 3.25mm diameter dental implants to be the minimum size that can insure adequate implant strength. Tooth implants greater than 4mm are available but are not widely used because sufficient bone width for these implants is less frequently available. }

4) The dentist will confirm that the hole for the tooth implant is appropriate.

At the end of the drilling process an alignment pin will be placed so the dentist can confirm that the hole that has been created meets the needed alignment and depth requirements for the dental implant being placed.

5) The dentist will insert the tooth implant in the hole they have prepared.

Now that the hole has been properly prepared, the dentist can insert the dental implant in the bone. This can be accomplished by either placing the dental implant (via a special adapter) into the dentist's dental drill and letting it slowly screw the implant into place, or else by using a hand wrench and screwing it in place manually.

6) The gum tissue is positioned back around the tooth implant.

The dentist will now screw a closure cap onto the exposed portion of the dental implant that they have just placed so its internal aspects are sealed off from the oral environment. The dentist will then trim the two flaps of gum tissue and reposition them back over the patient's jawbone and around the dental implant. They will also place a few sutures (stitches) in the gum tissue to hold it in position.

The stitches are usually left in place for about seven days. After this time period the gum tissue will have healed sufficiently that the stitches can be removed (a very painless procedure). In most cases the implant is given a period of three to six months to heal (osseointegrate with the patient's bone) before it is restored.

{ In some cases the placement of a tooth implant requires two separate surgical procedures. The initial surgery involves the placement of the dental implant itself as we have just described, with the exception that at the completion of this first surgery the gum tissue flaps are positioned back so they completely cover over both the jawbone and the dental implant.

A less involved surgery (one that typically only involves manipulating gum tissue, not trimming bone) is then performed after the healing (osseointegration) of the dental implant has taken place. The purpose of this surgery is to expose the top portion of the dental implant so it can be accessed and have a dental restoration made for it. }

Restoring the Dental Implant

The dentist will create a dental restoration for the tooth implant.

In most cases a dentist will wait three to six months (while the osseointegration of the dental implant with the bone takes place) before beginning the process of restoring the implant. The precise amount of time that is allowed, however, can vary. When making a determination about the needed healing time frame, the dentist will take into consideration the type of bone in which the implant has been placed (both bone quality and quantity), the implant's size, and the type of surface treatment that the implant has received during its manufacturing process.

Once an adequate healing period has elapsed the implant can have its needed dental restoration fabricated and placed. The first step towards this goal involves removing the closure cap that was screwed onto the implant and replacing it with a suitable abutment. This abutment portion of the dental implant provides the nub over which the final dental restoration can be anchored. Then, typically, a dental crown is simply cemented in place over the abutment.

What is a Sinus Lift and why might it be needed before a tooth implant is placed?

A sinus lift is a bone grafting procedure that is sometimes performed as a part of preparing a site for a dental implant. A sinus lift is required in those instances where the amount of bone found in a patient's upper jaw (in the region originally occupied by their bicuspid or molar teeth) is inadequate to accommodate the planned implant.

There can be several reasons why the amount of bone found in the patient's upper jawbone might be insufficient to accommodate a dental implant. Some of them include:

A) The patient's normal jaw anatomy presents complications.

The relative size and shape of an individual's upper jaw as well as the current size and shape of their maxillary sinus (the size of the sinus can change with age) varies among people. While over simplified, any one person may have a combination of a relatively small upper jaw and relatively large sinus which together create a situation where there is an insufficient amount of bone for the placement of a tooth implant.

B) The patient has experienced bone loss due to gum disease.

In situations where advance periodontal disease (gum disease) is present, the bone that surrounds and supports the person's teeth is damaged. In the most severe cases, significant amounts of bone can be lost from around the person's teeth, to the point where there is no longer an adequate amount of bone in which to place a tooth implant.

C) Bone resorption associated with previous tooth extractions.

When teeth are extracted the bone that originally held the teeth in place will under go a process called resorption. The net effect of this process is that much of the bone in the region originally occupied by the tooth is lost, possibly to the point where there is an insufficient amount of bone in which to place a dental implant.

The magnitude of post tooth extraction bone loss can be as much as 40 to 60 percent within the first three years after teeth have been removed. Beyond that point, the rate of bone loss typically subsides substantially. The cause of post extraction bone resorption is typically attributed to disuse atrophy, decreased blood supply, localized inflammation and/or unfavorable pressure from a dental appliance (denture or partial denture).

D) Bone loss due to other factors.

In some cases a bone deficiency may be associated with a previous surgical procedure such as a difficult tooth extraction or the removal of a cyst or tumor.

How is the sinus lift procedure performed?

The sinus lift is a surgical procedure. The specific technique that the dentist utilizes can vary depending upon their training and experiences but traditionally the procedure has been performed as follows:

The dentist will make an incision in the patient's gum tissue on the cheek side of their upper jaw in the area where the placement of the dental implant is planned (in the region originally occupied by the patient's bicuspid or molar teeth). This incision allows the dentist to flap back the patient's gum tissue and expose the jawbone that lies underneath.

The exposed bone is cut in a fashion where a "trap door" of bone, hinged at the top, is created. This movable section of bone is then pushed gently inward and upward into the sinus cavity. This bone movement caries the sinus membrane attached to it with it, thus "lifting" the membrane (and hence the sinus floor) to a new, higher level. The empty space underneath the lifted sinus membrane is then packed with bone-graft material thus providing the new bone into which the tooth implant will be placed.

Once the bone-graft material has been positioned the gum tissue is stitched closed.

In some instances it can be possible that the dentist will place the dental implant at the same time that the sinus lift is performed. In most cases, however, a dentist will allow a healing period of six to nine months before the dental implant is placed. The specific time frame allowed for healing is dependent upon the type of bone-graft material that has been utilized.

What types of bone-graft materials are used with the sinus lift procedure?

Several different types of bone-graft materials can be utilized with the sinus lift procedure. In some instances the patient's own bone will be used, such as bone harvested from another location in the patient's mouth or else from other bones (including the hip (iliac crest) or shin bone (tibia)). In other instances prepared bone (frozen bone, freeze-dried bone, demineralized freeze-dried bone), either human or from another species (i.e. bovine), can be purchased from a tissue bank for use. Another alternative involves the use of synthetically derived graft material such as hydroxyapatite.