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As dental implant reconstruc-tion has evolved into a main-stream
alternative to replace miss-ing teeth, bone grafting techniqueshave
also evolved as an ancillaryprocedure for site development,sinus
augmentation, and guided bone regeneration. Concurrently,imaging
technologies have beendeveloped which allow unsur-passed inspection
of the dental-alveolar complex, providing clini-cians with
innovative tools to planfor dental implant reconstruction.The
ability to diagnose and treatdental implants have been
foreverchanged by the ability to assesspatient anatomy using
ComputedTomography (CT), Cone Beam(CBCT), and interactive
treatmentplanning software within the uni-versal standard language
of data
called DICOM (Digital Imagingand Communications inMedicine).
This increased abilityhas been expanded to includeappraisal of bone
grafting receptorand donor sites through innova-tions in the
interpretation of threedimensional data.
In the completely edentulousmandible or maxilla, the use of CBCT
technology is an essentialtool for assessing anatomy inpreparation
for implants or graft-ing. The ability to visualize theextent of a
defect from variousangles, views, and 3-D reconstruc-tions has
helped to define a newset of diagnostic paradigms. Atwo-dimensional
panoramic recon-struction of the maxilla can pro-vide a good scout
film of theanatomy; however, as a two-dimensional modality, it has
inher-ent limitations and distortion. Theright and left maxillary
alveolar bone height can be approximated,and the relative size of
the bilater-al maxillary sinuses or extent of pnuematization can be
assessed inrelation to the underlying bone
and nasal cavity. However, it isnot until all possible
two-dimen-sional and 3-D views have beenexamined that the actual
boneanatomy can be appreciated andassessed in relation to the
plannedreconstruction.
Using CBCT, several different
Volume 20, Number 6 June 2009
Bone Grafting Assessment: Focus on the Anterior and Posterior
Maxilla Utilizing Advanced 3-D Imaging Technologies
By Scott D. Ganz, DMD
EDITOR
Arun K. Garg, DMDEditor in Chief
EDITORIAL ADVISORS
Editor Emeritus: Morton L. Perel, DDS, MScD
Renzo Casselini, MDTProfessor of Restorative DentistryLoma Linda
UniversityLoma Linda, CA
Leon Chen, DMD, MSPrivate PracticeLas Vegas, NV
Scott D. Ganz, DMDPrivate Practice of Prosthodontics,
MaxillofacialProsthetics and Implant DentistryFort Lee, NJ
Jim Kim, DDS, MPH, MSPrivate Practice of PeriodonticsDiamond
Bar, CA
Sachin Mamidwar, MD, MSCo-Founder and General Manager, Orthogen,
LLCSpringfield, NJ
Carl E. Misch, DDS, MDSCo-Director, Oral ImplantologyUniversity
of Pittsburgh School of Dental Medicine
Peter Moy, DMDPrivate Practice,West Coast Oral and Maxillofacial
Surgery Centerand Center for OsseointegrationLos Angeles, CA
Myron Nevins, DDSAssociate Professor of PeriodontologySchool of
Dental MedicineHarvard UniversityBoston, MA
Paul Petrungaro, DDS, MSPrivate Practice of PeriodonticsChicago,
IL
Andre Saadoun, DDS, MSPrivate Practice of PeriodonticsParis,
France
All images contained within this issue are fromDr. Ganzs
practice.
NOW AVAILABLE ON-LINE!Go to www.ahcmedia.com/online.html for
access.
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views can provide invaluable infor-mation as to the patients
anatomicalpresentation. They include the axial,cross-sectional,
panoramic, and 3-Dviews. The axial view helps to revealthe true
magnitude of atrophy exhibit-ed in the anterior maxilla of a
patientwearing a complete denture ( seeFigure 1). Scrolling through
the cross-sectional images, allows for an exami-nation of the
extremely thin strip of cortical bone representing the
residualalveolar ridge supporting a completedenture ( see Figure
2). Moving posteri-orly, the lack of remaining vertical bone height
beneath the maxillarysinus is evident ( see Figure 3a). Thesinus
can be examined for pathology,thickening of the membrane, widthand,
in some instances, theosteomeatal complex can be clearlyvisualized.
Additionally, the extent of sinus pneumatization can be visual-ized
and substantiated through undis-torted measurements available
withinthe diagnostic tools of the software.Sometimes overlooked,
but certainlyimportant, are the significant arteriesthat supply
vascularization to themaxillary sinus. These include
theposterior/superior alveolar artery, the
anterior superior alveolar artery, andthe infraorbital artery.
In a significantpercentage of CT/CBCT scans, thesevessels can be
detected and differenti-ated in terms of vertical position on
the external wall of the sinus, as wellas a superficial,
intraosseous, or intra-sinus location ( see Figure 3b). The
loca-tion and diameter of these vesselsshould be an important
considerationwhen performing a sinus augmenta-tion because of the
potential risk of bleeding during the procedure. Whenpossible,
depending upon the soft-ware utilized, a 3-D reconstruction of the
maxilla is the final step to confirmthe actual maxillary anatomy (
seeFigure 4a). Looking down upon themaxillary arch, the volume and
asym-metry of the right and left maxillarysinus can be fully
appreciated, as theyare delineated from the nasal cavity(see Figure
4b). The treatment alterna-tives for this type of clinical
presenta-tion are narrowed considerably oncethese images are
assimilated, yet theseoptions will be based upon accurateknowledge
of the anatomy, and can be decided well in advance of the sur-gical
intervention.
Sinus Grafting Assessment Advanced imaging technologies
greatly enhance planning and execu-tion of sinus augmentation
proce-dures. In the cross-sectional view, the
amount of bone volume necessary can be accurately determined by
measur-ing from the lateral to the medial wall,and the height
necessary to supportan implant ( see Figure 5a).
Additionally, the surgical access win-dow can be planned in
advance of the procedure. Using the sinus graftsoftware tool, a
simulated implant can be placed within the sinus and a sim-ulated
graft can be software-generatedto fill the cavity ( see Figure
5b)(SimPlant; Materialise Dental, GlenBurnie, Md). Using advanced
clip-ping features, the 3-D reconstructedmaxilla can be sliced to
view the sin-gle realistic simulated implant sittingin the sinus
(green) with a yellowabutment projection aiding the posi-tion to
emerge through the plannedrestoration ( see Figure 6a).
Informationon graft volume can then be calculat-ed by filling the
sinus cavity with sim-ulated bone to help predict the typeand
quantity of bone required forproper augmentation ( see Figure
6b).
Using low-dose CBCT, post aug-mentation scans can be taken to
veri-fy the quality of the bone augmenta-tion, to determine medial
fill, densi-ty, height and width of the graft, andif perforations
or graft leakageoccurred. These unparalleled viewscan be of great
value for all clinicianswho are interested in achieving ahigher
degree of accuracy with sur-
gical augmentation procedures and,when post-operative CBCT scans
aremade available, understanding actu-al treatment outcomes in
threedimensions. The post-augmentation
Dental Implantology Update June 2009
42
Dental Implantology Update (ISSN 1062-0346) is published monthly
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scan can be utilized to properlyassess the newly created graft
vol-ume and surrounding structures forsubsequent implant placement
( seeFigure 7a). Undistorted measure-ments help provide valuable
infor-mation which could not be deter-mined without these advanced
inter-active tools. Once verified, the pre-cise length and diameter
of the mostappropriate implant can be simulat-ed to take advantage
of the most
available bone ( see Figure 7b). Theability to slice through the
3-D recon-struction provides yet another valu-able interactive view
verifyingimplant placement within the zoneof the Triangle of Bone
(TOB)described in various articles since1995 (see Figure 7c).
Block Bone Graft Assessment: Receptor and Donor Sites
The use of CT and CBCT has beendemonstrated to be invaluable
insmall bone defects, and also large bone defects, when planning
for eitherparticulate or block grafting proce-dures. Proper
assessment of large bony defects can be essential to long-term
restorative success. It is not onlyimportant to visualize the
defect itself
but it is critical to understand therestorative requirements of
the regionso that the graft can be properly con-figured. A 3-D
reconstructed viewreveals loss of four maxillary incisorswith
concurrent loss of substantialalveolar ridge volume ( see Figure
8).Depending upon philosophy andtraining, three or four implants
wouldideally be required to support the
missing four anterior teeth. However,without a diagnostic
wax-up, it could be difficult to place the implants with-in the
desired restorative envelopewhile avoiding embrasures and,
withresultant, proper emergence profilesfor soft tissue maintenance
and esthet-ic appearance. This would be especial-ly significant if
the patient has a highlip and smile line. To achieve
truerestoratively driven implant dentistry,the position of the
teeth must be
appreciated prior to placing a graft oran implant.Through the
use of diagnostic
wax-ups and barium sulfate scan-ning appliances, the tooth
positioncan be visualized on the scan. Often,patients are scanned
without a tem-plate, which does not relate thedesired tooth
position to the under-lying residual defect. The evolution
June 2009 Dental Implantology Update
43
Figure 1: Axial view of severely atrophic anterior maxilla.
Figure 2: Cross-sectional view of thin alveolar crestal bone.
Figure 3b: Location of intraosseous vessel on wall of
sinus.Figure 3a: Maxillary sinus volume as seen in
cross-section.
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of the virtual tooth, or virtual occlu-sion, has added a new and
impor-tant tool set for interactive treatmentplanning. When several
teeth aremissing, more control of the processis required and, thus,
these virtualtools must continue to evolve intostrategic diagnostic
modalities. Dueto the volumetric loss of buccal boneand to support
the ideal, occlusion
implants need to be placed facial tothe residual bone,
necessitating asubstantial amount of graft thick-ness. The position
of the four miss-ing virtual incisor teeth should becreated in the
ideal position, so thatthe simulated implants can be posi-tioned to
best support the anticipat-ed restoration ( see Figure 9).However,
there is insufficient bone
to cover the exposure of threads onthe facial aspect of the
implants or toallow the implants to be fixated. Thenext step would,
therefore, be to sim-ulate the bone graft volume neces-sary to
surround and fixate theimplants after graft maturation.Using a
simulated j-graft blockgraft shape, measurements can bemade from
the ideal implant posi-
tion to determine the thickness of graft required to support the
implantand the surrounding soft tissue.Once a virtual implant,
virtual abut-ment, and virtual tooth have beenplaced, additional
measurements can be made from the outer aspect of theimplant to the
outer aspect of thegraft ( see Figure 10a). With such alarge
volumetric defect crossing the
midline of the anterior maxilla, itmight be desirable to place
morethan one block bone graft, or use areinforced membrane, to
containparticulate grafting material. For thisexample, bilateral
simulated bonegrafts placed to support fourimplants, abutments, and
the desiredposition of the restorations can beseen in Figure 10b.
Of note, are the
fixation screws that have also beenstrategically placed to help
stabilizethe grafts. The precision of this plan-ning can not be
underestimated.
Utilization of 3-D scans can alsohelp locate graft donor sites
in theposterior ramus or the symphysis.The thickness of the facial
corticalplate and the location of the inferioralveolar nerve help
to identify a safe
Dental Implantology Update June 2009
44
Figure 4a: Three dimensional reconstruction of maxilla. Figure
4b: Bi-lateral sinus volume, and nasal cavity in3-D view.
Figure 5b: A simulated bone graft can be generated tosurround an
implant placed within the sinus.
Figure 5a: The width and height of the sinus can be mea-sured in
the cross-sectional view.
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and adequate donor site in theramus ( see Figure 11a). The
proximityto the path of the nerve, the thick-ness of the cortical
plate, and thedensity of the medullary bone can befully
appreciated. The shape and sizeof the graft can then be
pre-deter-mined and assessed for fit in thereceptor site ( see
Figure 11b). Usingthe same process, donor sites can beevaluated in
the anterior symphysisof the mandible. Once the graft has been
harvested from either theramus, the symphysis, or a bone bank, the
receptor site is prepared toreceive the graft. To continue
theplanning process, virtual positioningof the fixations screws
helps toensure intimate fit and stability of the graft. The
cross-sectional clip-
ping of the 3-D reconstructionshows how two fixation screws have
been planned, the relationship between the simulated implant to
beplaced (after the graft has matured),and the underlying
pre-existing alve-olus ( see Figure 12a). The 3-D recon-structions
further emphasize theplanning capabilities inherent
instate-of-the-art treatment planningsoftware by revealing the
entiretooth-abutment-implant complexwithin the simulated grafted
recep-tor site ( see Figure 12b). To ensureaccuracy of placement
and to deter-mine proper embrasures, the enve-lope of the teeth
should be complete-ly visualized in the occlusal view of the 3-D
reconstruction with the fourvirtual maxillary incisors ( see
Figure
13). An actual bilateral graft proce-dure demonstrates the
planning con-cepts presented in this paper ( seeFigure 14).
ConclusionImaging technology has
advanced significantly in the pasttwo decades. Both CT and
ConeBeam CT scanning have gained
acceptance as necessary pre-surgicalplanning tools for placement
of den-tal implants and for an understand-ing of the patients three
dimension-al bony anatomy for grafting proce-dures. When using
software associ-ated with the CBCT scan machine,details of the
patients anatomy canallow for inspection of the area of interest by
utilizing several different
June 2009 Dental Implantology Update
45
Figure 6a: A realistic implant (green) and abutment pro- jection
(yellow) positioned within the sinus.
Figure 6b: To determine the volume of bone necessarythe software
generated bone graft fills the sinus.
Figure 7b: Undistorted measurements help provide valu-able
information regarding the placement of an implantwithin the new
graft.
Figure 7a: Post augmentation scan allows for assessmentof the
graft placement.
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June 2009 Dental Implantology Update
47
Figure 10b: Bilateral simulated bone grafts placed toreconstruct
the anterior maxilla in anticipation of sup-
porting four teeth.
Figure 11a: Donor sites can be identified in the posteriorramus
through cross-sectional assessment of the path of the nerve and the
cortical bone thickness.
Figure 12a: Cross-sectional "clipping" shows how two fixa-tion
screws are planned to secure the simulated bone graft.
Figure 11b: The shape and size of the donor graft can be
pre-determined.
Figure 12b: The implant-abutment-crown complex andthe fixated
bone graft in a slice of the 3-D reconstruction.
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6. Mandelaris GA, Rosenfeld A. The
expanding influence of computed
tomography and the application of
computer-guided implantology.
Pract Proced Aesthet Dent .
2008;20:297-305.
7. Ganz SD. Using interactive tech-
nology: in the zone with the
Triangle of Bone. Dent Implantol
Update . 2008;19:33-38.
8. Sharan A, Madjar D. Maxillarysinus pneumatization
following
extractions: a radiographic study.
Int J Oral Maxillofac Implants .
2008;23:48-56.
9. Wallace SS. Maxillary sinus aug-
mentation: evidence-based decision
making with a biological surgical
approach. Compend Contin Educ
Dent . 2006;27:662-668.
10. Sharan A, Madjar D. Correlation
between maxillary sinus floor
topography and related root posi-
tion of posterior teeth using
panoramic and cross-sectional
computed tomography imaging.
Oral Surg Oral Med Oral Pathol
Oral Radiol Endod . 2006;102:
375-381.
11. Ganz SD. Presurgical planning
with CT-derived fabrication of sur-
gical guides. J Oral Maxillofac
Surg . 2005;63:59-71.
12. Pikos MA. Mandibular block auto-
grafts for alveolar ridge augmenta-
tion. Atlas Oral Maxillofac Surg
Clin North Am . 2005;13:91-107.
13. Pikos MA. Atrophic posterior maxilla
and mandible: alveolar ridge
reconstruction with mandibular
block autografts. Alpha Omegan .
2005;98:34-45.
14. Ganz SD. The replacement of a
unilateral partial denture with an
implant-supported fixed prosthe-
sis: a clinical report. Implant Dent .
1998;7:159-16
Dental Implantology Update June 2009
48
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Figure 13: The envelope of the virtual occlusion aids
indetermining embrasures, and insures implant positioningwithin the
body of each tooth.
Figure 14: An actual bilateral bone graft in the anteriormaxilla
demonstrates the outcome of proper planning.
