Evaluating the suitability of the patient's jaw for an implant. -

Bone quantity/density/quality determinations. | X-ray evaluation. 3D Cone Beam imaging. | Jawbone deficiencies that may contraindicate implant placement. | Considerations with pre-implant placement infections.

Determining implant site bone tissue quality and quantity.

A primary factor affecting the long-term success of a dental implant is the suitability of the bone in the region in which it's been placed.

As this page explains, towards making this judgment call, when laying plans for a patient's procedure the treating dentist must:

  • Evaluate the quantity (bone volume) and quality (bone density and architecture) of the tissue in the region of the planned implant.
  • Insure that the planned location for the implant in the jawbone is distant enough from neighboring anatomical structures (teeth, nerves, sinuses, etc...).
  • Determine that there is no pathology associated with the area that will interfere with the successful outcome (placement, healing and osseointegration) of the device.

Evaluation methods a dentist will use.

In determining the above factors, the dentist's method of examination will need to be twofold.

  • One aspect will involve routine clinical techniques: visualization, palpation (touching, feeling), and measuring the jawbones.
  • The other will involve the use of dental x-rays.

What type of x-rays will be needed?

A panoramic dental x-ray.

Dental x-rays are used to evaluate the jawbone for an implant.

In some cases, a simple combination of the following radiographic techniques will be satisfactory for planning and performing a patient's procedure.

1) A panoramic x-ray evaluation - This is a single large radiograph that shows both of the patient's jaws and all of their teeth (see picture).

The American Academy of Oral and Maxillofacial Radiology (AAOMR) considers a conventional panoramic evaluation to be the imaging modality of choice for initially evaluating a patient for a dental implant. (Tyndall 2012) [reference sources].

2) Supplementary periapical radiographs - These small x-rays (the kind most often taken in a dentist's office) are used to examine just small areas at a time (like those associated with just one or a few teeth) and may be needed to supplement or clarify what's noticed on the panoramic evaluation.

3D x-ray imaging.

In other cases, the dentist may feel that the additional, more-detailed information that 3D x-ray imaging can provide is needed. In dentistry, the most frequently used type is Cone Beam Computed Tomography (CBCT).

Due to the cost of this equipment, it's more common for a dental specialist (i.e. oral surgeon) to have 3D capabilities in their office rather than a general dentist. Although, a patient can be referred out for this type of imaging if needed.

Considerations.

Beyond the added expense it involves, 3D imaging also exposes the patient to added radiation. And for both of these reasons, it should never be considered just a routinely included part of a patient's treatment. The need for it must be justified. This position is endorsed by the AAOMR (Tyndall 2012).

Benefits of pre-implant placement 3D imaging.

There is no question that the 3D nature of a Cone Beam scan can provide useful information that otherwise would be impossible to collect.

  • Using CBCT cross-sectional imaging, a dentist can accurately determine the volume (height, width, shape) of the jawbone in the area of the planned implant. (2D imaging isn't able to provide jawbone width, and therefore detailed shape and volume, information.)
  • CBCT imaging allows the dentist to determine how closely different structures (teeth, nerves, sinuses, etc...) lie to the area of the proposed implant.

    Having this information can help to prevent procedural complications. And in areas where the available bone is deficient, having this information helps the dentist understand the full extent of the bone graft that will be needed. (Such as a sinus lift.)

  • The digital file created during a CBCT scan can be used to design and print (fabricate) surgical guides.

    These are temporary appliances used during the implant procedure that help a dentist to accurately orient the placement of the device (position, angle, depth, etc...) in the jawbone.


Graphic stating that a dental implant requires an adequate amount of bone.

Factors the dentist must evaluate -

1) Jawbone quantity and quality.

The dentist must determine that there's an adequate quantity of bone in the region of the planned implant, and that it's of sufficient quality.

  • Making this determination will involve evaluating the overall shape of the bone (both width and height).
  • The architecture of the bone's internal honeycomb-like structure in the region of the placement site (including the size and orientation of the spaces) must be evaluated too.
  • An estimation of the bone's density (bone mineral content) must be made too. Within the same patient, this can generally be expected to be lower for maxillary (upper) jawbone sites as opposed to mandibular (lower) ones.

    While methods of making measurements do exist, a dentist usually estimates implant-site bone density based on hints revealed by x-rays, especially CT scans, that have been taken.

 

2) Reasons why a patient's jaws may be determined to be unsuitable for implant placement.

A dentist's evaluation of their patient's jawbone may discover characteristics or reasons that make it unsuitable for their planned implant, at least initially.

a) Infection.

Especially in cases where an existing tooth occupies the location where an implant will be placed, the dentist will evaluate the tooth and its surrounding tissues for evidence of infection.

  • Generally speaking, and especially in the case of elective surgeries like implant placement, a dentist won't perform a surgical procedure in an area showing signs of active (acute phases of) infection.

    Doing so may complicate performing the procedure, aid in spreading the infection and/or hinder the healing process that follows.

    So if signs of active infection are discovered, the dentist will place a priority on limiting its extent (bringing it under control) before proceeding with any surgical steps.

  • If immediate implant placement is planned (a situation involving the removal of the existing tooth and then immediately placing the implant in the fresh extraction site), the presence of a limited infection associated with the existing tooth may or may not prove to be a contraindication.

    Based on their review of published research, the authors of some papers (Marconcini 2013, Chrcanovic 2015) have concluded that the presence of an infection (either root canal or gum disease related) may be a manageable condition and therefore doesn't necessarily contraindicate the immediate placement of dental implants as long as appropriate pre and post surgical steps are taken.

    Of course, only the treating dentist can determine if placing an immediate implant under these conditions makes an appropriate option for their patient or not.

  • Extraction of the infected tooth first, followed by a 4 to 6 month healing period, has been the approach followed historically to manage this situation.

b) Excessive bone resorption.

A natural process that takes place after tooth extraction is that of bone resorption (bone loss, atrophy). And if enough loss has taken place, there may not be enough bone quantity in which to place an implant (at least not without doing a grafting procedure first, see below).

Details.

This type of defect is often most noticeable in regions where multiple teeth have been removed, especially if several years previously. The bone in the area typically has a sunken-in appearance.

The magnitude of post-extraction bone loss can be as much as 40 to 60 percent within the first three years following the tooth's removal. Beyond that point, the rate of loss characteristically slows down substantially.

The cause of the resorption is typically attributed to disuse atrophy (decreased blood supply, localized inflammation and/or unfavorable pressure from a dental appliance, such as a partial or full denture).

c) Bone damage due to disease.

In other cases, a patient's bone deficiency may be attributed to a dental condition, such as bone loss caused by advanced periodontal disease (gum disease).

As a result of this condition, significant amounts of bone may be lost from around the person's teeth,
to the point where if they are extracted there may be an inadequate quantity of bone in which to place an implant.

d) Previous surgery.

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

e) Bone pathology.

The dentist must search for evidence of pathology within the jawbone (including tumors and cysts).

Additionally, impacted teeth and tooth root fragments (remnants of past extractions) need to be identified and removed as the dentist feels it's needed.

Animation showing that a dental implant cannot be placed in the area of the mandibular nerve.

Nearby anatomical structures must not be impinged by implant placement.

f) Anatomical considerations.

The location of anatomical structures, such as sinuses, nerves, blood vessels and the roots of adjacent teeth must be identified.

This is important because implants must be placed so they are suitably distant from these objects.


Bone grafting may be necessary before an implant can be placed.

Adequate bone must exist for an implant.

Animation showing that a dental implant cannot be placed in the area of the maxillary sinus.

In this case, bone grafting will be needed.

Since the success of a dental implant will be greatly dependent upon the bone in which it's placed, the treating dentist may feel that it's necessary for them to perform bone grafting so an adequate amount exists.

This is typically a separate procedure that must be performed (and allowed to heal) prior to placing the implant.

We discuss one such grafting procedure termed a Sinus Lift. It's frequently performed in association with placing implants that replace upper back teeth.


Evaluating the patient's soft tissues.

A portion of the dentist's clinical examination must also involve an evaluation of the soft tissues of the patient's mouth. Of course, they must find that these tissues are free of pathology and appear to be healthy.

They must also evaluate both the quantity and type of tissue that exists in the immediate area around the implant site. The right type of gum tissue (attached gingiva, gums tightly bound to the bone underneath them) must surround the implant to insure its long-term success.

 

Written by: Animated-Teeth Dental Staff

Last revision/review: 8/26/2018 - Content added.

Content reference sources.


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Comments

Is cone beam x-ray necessary?

My expenses just keep piling up.

K.V.

Really, only a dentist to whom you went to for a second opinion would be able to answer this question.

From the patient's view, we get that some services that are performed often seem just to be profit centers, or utilized just to help to pay for expensive equipment that has been purchased.

At the same time, the dentist no doubt wants everything about the procedure to be successful (and clearly 3D imaging does provide a higher level of information). And legally they are obligated to practice dentistry at the same level as other practitioners (so if most dentists would have used cone beam imaging for your case and your dentist didn't and a complication arose ...).

Per our AAOMR references above, theoretically it's expected that a dentist will initially evaluate their patient using more conventional types of radiographic exam (panoramic x-ray) and then make a decision for 3D imaging based on that.

It seems reasonable that a dentist would share with their patient what they see on that x-ray that suggests that CBCT imaging is indicated. (While we didn't mention and as you seem to suspect, yes many implants are placed without the assistance of CBCT radiography.)


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