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The primary goal of implant dentistry is
not to achieve osseointegration, but to
replace the tooth, or the lost anatomy to
proper function and aesthetics1,2.
In order to achieve this goal it is necessary to
visualize the final result prior to placing a
scalpel to the patient. Various techniques
have been proposed to help locate the
proper position of the fixture in relation to
the ultimate tooth position and emergence
profile of the final restoration. The fixture
location is also dictated by a combination of factors including available height
and width of bone, and considerations as
to the density, or quality of that bone3-9.
During the early learning curve of implant dentistry, some clinicians assumed
that the "osseointegrated" state of a
titanium fixture indicated bone interfacing with 100% of the implant's surface
area. Many clinicians are still under this
misconception. The anatomy and physiology of the bone itself, whether mandible or maxilla does not exist as 100%
bone in its pre-implant state. The bone
consists of marrow space, blood vessels, fat cells, and other non-mineral entities. Current research confirms that the
bone-implant interface falls far below
100%, and can range from 25% - 75%
depending on the classification (Type I-IV) and location10,11,12. The clinician must
have a full understanding that the implant
fixture replaces, and acts only as the
root. The prosthetic, transmucosal components allow this new "root" to support
the clinical prosthetic crown or prosthesis. Long-term survival of an implant
fixture is therefore dependent upon the
amount of bone in direct contact with the
fixture, the fixture size, and the subsequent forces applied to that fixture under
function, and load. Consequently, the
implant must be placed in a position
which would enhance and maximize the
potential volume of surrounding bone.
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Fig. I (above left) The natural tooth illustrated in its alveolar housing, the extraction socket, and the implant replacement. The amount of bone as illustrated does not exist clinically Fig. 2 (above right)The implant follows the path of the extraction socket. After healing, the abutment post is placed, followed by the final prosthetic crown.
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The natural tooth root in its alveolar bone
housing, may appear to have an ample
quantity of bone thickness between the root itself and the buccal or lingual plate [FIG. 1].
Once the tooth has
been lost1 the clinician may visualize
replacing the natural tooth with an implant fixture, within
the residual socket
site [FIG.2]. The
technique for the
placement of implants into immediate extraction
sites has been well
documented in
the literature13-16.
However the most
common visual concept of the three dimensional,
cross sectional view of the actual bone
anatomy surrounding the natural tooth
root is seriously flawed.
N E X T+
P A G E |
The Triangle of Bone
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Fig. 3 (left) Three cross-
sectional images from a CT Scan
film of a natural tooth
in its alveolar housing.
Fig. 5 (left) A computer
enhancement to help
highlight the information
Th the CT Scan image.
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Fig. 4 (above) Close-
up view of a single
cross-sectional image.
Contrast the amount of
buccal or palatal plate
with the illustration in
Figure 1.
Fig. 6 (above) If the implant follows the socket site, it may perforate
the buccal cortical plate of bone and lead to a poor prognosis.
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Dr. Scott D. Ganz has published extensively. delivered presentations worldwide, and is a Clinical Attending at Hackensack Medical Center. Dr. Ganz completed a three-year
Maxillofacial Prosthetic Residency at M.D. Anderson Cancer Center in Houston, Texas, and currently maintains a private Prosthetic and Implant practice in Fort Lee, New Jersey. He is a Fellow of the American Academy of Maxillofacial Prosthetics and a Diplomate of the International Congress of Oral Implantologists. Dr. Ganz's chairside patient education guide. An Illustrated Guide. to Understanding Dental Implants is now available. Call (201)
592-8228 for more information.
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