Download with Pantomography in the Assessment

Lee H. Silverstein, DDS, MS/Roger Sr. Melkonian,
DDS/Michael D. Lefkove, DDS
DDS/David
Kurtzman,
DDS/Jerry
J. Garnick,
Linear Tomography in Conjunction
with Pantomographyin the Assessment
of Dental Implant Recipient Sites
- bstract
A
omography provides a three-dimensional unobstructed and anatomically accurate picture of
the region being viewed. Tomography is a radiographic technique in which a "slice" or section
of a given internal body structure is imaged in a pre-determined plane. The advantage of
utilizing a tomographic evaluation along with a pantomographic survey is that the clinician
may examine the exact position or depth in all three planes of visualization. This radiographic modality
can also reveal the quality and quantity of alveolar bone in a pre-determined implant site. This
information would allow the clinician better to diagnose, plan treatment, and place dental implants
more precisely. Therefore, the utilization of laminar or computerized tomography along with
pantomography for more precise visualization and accurate measurement of available alveolar bone of
the buccal-lingual and labial-palatal perspective will be discussed and illustrated.
Key words. Tomography, X-ray.
Introduction
Proper diagnosis and treatment planning are of
paramount importance for precise placement of
dental implants. The general objective is to place
implants in alveolar sites that are favorable to
achieving osseointegration. Areas in which the
alveolar bone is of inadequate height, width, or
where implant placement will likely compromise
anatomical structures-such
as the mandibular
nerve, maxillary sinuses (Fig. 1), or regions of
severe alveolar bony undercuts (Figs. 2A, 2B)should be accurately identified and assessed, as
concluded by Shulman (1988), Stella and
Tharanon (1990), and Lindh and Petersson (1989).
The attainment by clinical observation and
palpation of the "third dimension" has proven to
be inadequate because of the various thicknesses
of the soft tissue overlying the bony maxilla and
mandible, according to Beman (1989). To some
extent, the third dimension can be ascertained by
utilization of a calibrated probe and sounding
through anesthetized tissue to the depth of the
alveolar bone, as reported by Petrokowski and
Pharoah (1989).
Discussion
Radiography plays an important
role in
osseointegrated implantologz. Since the individual
anatomy of the jaw is so variable, it is imperative
that the dentist have a clear view of the jaw in the
area where the implant will be placed.
Currently,
the most commonly
used
radiographic survey for pre-implant placement is
the panoramic radiograph (Fig. 3). This film is an
adequate "survey" film for viewing the maxillary
and mandibular bone content, density, and form,
as well as the sinuses, dentition survey,
impactions, osseous diseases, and generalized
symmetries, as reported by Petrokowski and
Pharoah (1989). The pantomographic film,
however, can be "user-inadequate", meaning that
this radiographic technique is very susceptible to
distortions, for many reasons. The panoramic
radiograph most commonly used for edentulous
patients is a magnified and distorted image of
both the maxillary and mandibular arches. These
distortions can be critical for implant position and
depth and, hence, implant success or failure.
The panoramic radiograph is also only a two-
Journal of Oral Implantology
I 11
Figure 1. Pantomographic survey imaged with a 25o/o
measured maEnillcatlon with tracing of the anatomical
structures of the head region.
Figure 28. Tomogram showing a cross-section of a
mandible with a severe lingual alveolar bony undercut.
P IN
A CRY LI CS UR G IC AL
S T E NT
,
.
S O F TIIS SU E
sEVERE
'-rrcunr,.jjii
AVAILABLE
ALVEOLARBONE
(x SECT|ON)
MANDIBULAR
BODY
Figure 2A. Illustration of a cross-sectional tomogram of a
mandible, taken in an anterior-posterior direction,
demonstrating a severe lingual alveolar bony undercut.
dimension al
view
t hat
does
not
indic at e
the
dimension"-of the
buccal-lingual width-"third
recipient implant site {Figs. 4A-4D). Subsequently,
radiographic
for a full three-dimensional
assessment of the recipient site to be obtained, an
adjunctive radiographic technique which could
obtain the desired information by taking thinly
sliced tomographic projections (Fig. 5) taken in the
anteroposterior (coronal) and lateral (sagittal)
dimensions is necessary (Figs. 6A-6D). This type
of imaging is referred to as tomographic
radiography. Tomographs can be either linearso-called "conventional", as described by
112 Vol. XX/No. TWo/1994
Figure 3. Diagrarn/illustration
of a panoramic radiograph
clearly showing vital anatomical structures.
Rosenberg (1967)-or computerized, as described
by Schwarz et al. (1989).
Conventional tomography as reported by Coin
(I974) is a radiographic technique in which a
"slice" or section (Figs. 7A-7C) of a given internal
body structure is imaged in a pre-determined
plane. Radiographic tomography provides a threedimensional unobstructed and anatomically
precise picture of the site being imaged by the
technique of shadow separation, which is achieved
by coordinating beam and film movements around
a fulcrum. In this manner, as reported by
Christen et a,I. (1972), only the tissue layer
positioned at the fulcrum plane is shown clearly;
tissue layers above and below the plane are
blurred. This differentiation reveals the quantity
and quality of bone in this pre-determined plane
which is of paramount importance in the
treatment planning of a site for the placement of
dental implants.
In order consistentlv to obtain the desired
AVAILABLEALVEOLAR
BONE
SOFTT
- - - YA C R Y LIC
S U R G I CAL
STENT
Figure 4A. Pantomographic survey of the anterior maxilla
for analysis of proposed implant sites.
PIN
Figure 4D, Illustration ofa cross-sectional tomographic
imag-e through the anterior ms*illa, revealing an
insuflicient width of crestal alveolar bone at-proposed
implant site.
Ygttt. 4B. Corresponding tomographic frontal image of
the anterior marilla through th- pioposed implant-sites.
Figure 5. Illustration
tomography.
Figure 4C. Cross-sectional tomographic image through the
anterior mndll4, showing an inadequate wia-th of alvlotar
bone at proposed implant sites.
of the concept of linear ..slice',
information from tomographic radiography
necessary for precise implant site evaluation and
l-lace-men-t, a protocol such as the following,
elucidated by Petrokowski and pharoah (lggg),
should be adhered to:
(A) low-radiation dosage, as advocated by
Richards and Colquitt (lg8l), Skoczylos jt
aL (1989), and Clark et at. (1990), in
which linear tomography exposes the
patient to l2O mrads;
(B) precise A-P (coronal) and lateral (sagittal)
tomographic views;
(C) relatively inexpensive to the patient; and
(D) utilizes a surgical stent that has repeatable
positioning for both pre- and post_surgical
radiographic evaluation (Fig. g).
Journal of Oral Implantology
f fg
witln a 25o/o
Fioure 6.{. Panoramic radiograph imaged
anatomical
tracing.of
wilh
cation,
;ajnifi
;:;;J
implant recipient sites.' indicating
;;";d
;T;;;;;
h"tght of alieolar bone in two dimensions'
;;;il;l"
Fi€ure 68. Photograph of pre-sur,gicalstent and
in tne proposed implant
;;ei;6;i"
-"."t.ito""tta
recipient sites.
tracing illustrating-the
Figure 6D. Dia$rammatic
radiograph taken in
tomogiaphic
.
ilE;;t;..ti";";f
"it1gr"
of a single implant
orilntation
t"terior'post"erior
pi"-"i""
.
site.
FiEureTA.Illustrationofamid-sagittal(laterat)sectionofsites'
indicating-proposed implant
il".;;"il;;
-.-"aitr.,
AVAII-ABLE
ALVEOLARBONE
mid-sagittal
Fi€ure 6C. Tomogram with tracin-gs showing of available
it po"t"tior maxilla and lack
a;:;il;;".ion
in i*prant reclpient sites at loo/omeasured
l;;;il;;;
magnification.
114 Vol. XXlNo. T\rol1994
tomography
Figure 78. Illustration of a cross-sectional
the sur,gical
lafen through the mandible with both
-stent
precis-e siteand buccal;Jd;;
;fit indlcating the
of proposed implant placement'
fi"g;J."ghation
Figure 7C. Tomogram
showing a cross-section
of a
mandible
with a radiopaque
marker over the proposed
implant
sites. This image revealed that the proposed
implant
trajectory
was too far lingual and should be placed
more buccally.
Figure 98. Sagittal tomogram with tracing showing a midsagittal section of mandible and available height of
alveolar bone in proposed implant recipient sites with a
loolo measured magnification.
Figure 8. Photograph of a pre-surgical diagnostic stent
with a radiographic marker placed in the proposed site of
dental implant placement.
Figure 9C. Cross-sectional tomogram taken in an anteriorposterior coronal orientation, indicating a significant
mylohyoid (lingual) concavity not detectable on a
panoramic radiograph.
Figure 9A. Pantomographic survey with pre-surgical
implant stent placed in mouth, with tracing of anatomical
structures indicating height of available alveolar bone
around implant recipient sites in a two-dimensional
orientation with a 25olomeasured magnification,
Figure 9D. Cross-sectional tomogram taken in an anteriorposterior coronal orientation, revealing a significant
buccal and lingual ledge of alveolar bone that necessitates
modification prior to implant placement.
Journal
of Oral Implantology
115
Many renowned lecturers who surgically place
dental implants have utilized either computerized
or laminar tomography as an adjunct to
pantomograptric films. These clinicians have
stated that, on numerous occasions. the
anticipated implant sites determined to be
acceptable when viewing a pantomographic
radiograph were abandoned or changed after a
comparison of the sites was made with
tomographic images (as illustrated in Figs. 9A9D). Many of the reasons for this phenomenon
were described by Jeffcoat et at. (199I), in which
these authors
stated that tomographic
radiography:
(A) allows the clinician to demonstrate the
medio-lateral width of bone;
(B) allows the borders of the maxillary sinus
to be determined precisely at the implant
site;
{C) allows the clinician to demonstrate the
medio-lateral position of the mandibular
canal;
(D) minimizes, if not eliminates, angular
distortion; and
(E) allows for a surgical stent to be
transferred from patient to a cast of the
patient for the surgical placement
marking.
Conclusion
In summation, osseointegrated dental implants
have been proven to be a successful mode of
replacing teeth. For precise and predictable
planning of the placement of dental implants,
especially in the maxilla and posterior mandible,
both the restorative dentist and surgeon should
require more diagnostic information than that
supplied by a pantomographic survey and
periapical radiographs. These aforementioned twodimensional
r adiographs do not provide
information on bone thickness or the location of
vital structures in a buccal-lingual dimension.
Therefore, it is also necessary to use imaging
techniques,
i.e., linear or computerized
tomography, that accurately display the size and
buccal-lingual location of the mandibular and
incisive canals, the maxillary sinus, and the shape
and density of the alveolar ridges and cortical
plates. The sites intended for implant placement
that are imaged with both pantomographic and
tomographic films should also be referenced with
radiographic markers and surgical stents. This
would allow for precise magnification and location
of implant sites with the advent of fiber-optic
alignment
systems that were heretofore
unavailable. Therefore, these films can be traced
and measured for the anatomical accuracy
116 Vol. XX/No. Two/1994
essential for proper diagnosis, treatment planning,
and surgical placement of dental implants.
-References
( 1989).
Beman
CL
Osseointegration,
complications, prevention, recognition and
treatment. Dent CLtnNorthAm 33:636-663.
Christen EE, Curry TS III, Nunnally J (1972). tur
introduction to the physics of diagnostic
radiology. Philadelphia: Lea & Febiger, f 96-
ztt.
Clark DE, Danforth RA, Barnes RW, Burtch ML
(1990). Radiation absorbed from dental implant
radiologr: A comparison of linear tomography,
CT scan, and panoramic and intra-oral
techniques. J Oral Implantol 16:156-154.
Coin
CG (197 4). Tomography
of the
temporomandibular joint. Joint Dent Photogr
Radtogr 47:23-33.
Jeffcoat M, Jeffcoat RL, Reedy MS, Lincoln B
t1991). Planning interactive implant treatment
with 3-D computed tomography. J Am Dent
Assoc 122:40-44.
Lindh C, Petersson A ( 1989). Radiologic
examination for location of the mandibular
canal: A comparison between panoramic
radiography and conventional tomography. Int
J Orat MaxttLofac Implants 5: I 5 -29,
Petrokowski CG, Pharoah NJ (1989). Presurgical
radiographic assessment of implants. J Prosthet
Dent6l:59-64.
Richards A, Colquitt W (1981). Reduction in
dental x-ray exposure during the past 60 years.
J Am DentAssoc lO3:7 l3-7 18.
Rosenberg HM (f 967). Laminography: methods
and application in oral diagnosis. J Am Dent
Assoc 74:88-96.
Schwarz MS. Rothman SL. Chafez N. Rhodes M
(1989). Computed tomography in dental
implantation surgery. Dent CLin North Am
33:565-597.
Shulman LB (1988). Surgical considerations for
implant dentistry. J Dent Educ 52:712-720.
Skoczylos LJ, Preece JW, Langlais RP, et aI.
(1989). Comparison of x-radiation doses
between conventional
and rare earth
panoramic radiographic techniques. Oral Surg
Oral Med OraI Pathol63:776-781.
Stella JP, Tharanon W (1990). A precise
radiographic method to determine the location
of the inferior alveolar canal in the posterior
edentulous mandible: Implications for dental
implants. Int J Oral MaxilloJac Implants 5:1529.
Dr. Lee Srluerstein rs an assistant professor at the
Medical CoILege oJ Georgia, Dept. oJ Periodontics,
and is tn prtuatu practice at 195O lVorth Park PLace,
Sutte 4OO, Attanta, GA 30339. Dr. Roger W.
Melkonian, a Jorrner associate proJessor at Emory
Uniuersitg's Dept. oJ Oral Medicine and
Radtographg, is nou in priuate practice at Head
and Neck Dtagnostic Assoctates, Atlanta, GA. Dr.
Jerrg Garnick is chairman of the Department oJ
Periodontics, Medicat Cotlege oJ Georgia, SctwoL oJ
Dentistry. Dr. Michael LeJkoue is in prtuate practice
in Atlanta, GA. Dr. Dauid Kurtzman i"s in priuate
practice in Atlanta, GA.
Journal of Oral Implantologr
Ll7
Wesley E. Shankland, II, DDS, MS
The Position of the Mental Foramen
in Asian Indians
A
- bstract
he modal or most common position of the mental foramen in the human mandible with
respect to teeth appears to be below the second premolar regardless of race or age. The
position of this structure was investigated in a sample of Asian Indians of unknown age or
sex. In this studv. 75.360/oof 138 mandibular sides exhibited the position of the mental
foramen to be located directly below the second premolar. In addition, 6.620/oof the mandibles
possessed accessory mental foramina. The results of this study do not support those reported in some
commonly used textbooks on anatomy, anesthesia, and anthropolog/ concerning the position of the
mental foramen in the human mandible.
Key words. Mandible, Mental Foramen, Mental Nerve, Anatomy, Asian Indians.
Introduction
The identification and actual location of the
mental foramen are quite important in clinical
dentistry as well as in microscopic and
macroscopic evaluation of the morphology and
maturity of the human mandible. For the
clinician, accurate location of this structure is
important in anesthesia for surgical, operative
dental, or diagnostic procedures (Edward, 1962:
Luebke et aL., 1964; Fishel et aL., 1976: Neuner,
1976: Grossman, 1978; Anderson et al., 1991;
Shankland, 1993). Information about this defined
skeletal landmark in pre-natal and post-natal
development is important to the embryologist and
anatomist for monitoring developmental changes
(Kjaer, 1989). The physical anthropologist relies
upon the mental foramen in the identification of
species (Simonton, 1923: Dart, 1954), races
(Wang et aL., 1986; Green, 1987; Green and
1989), and
Darvell, 1988; Kekere-Ekun,
determining ages (Gershenson et aL., 1986).
The mental foramen marks the termination of
the mandibular canal in the mandible, through
which the inferior alveolar nerve and vessels pass.
At this point, the mandibular canal actually
bifurcates and forms the mental and incisive
canals (Fawcett, 1895). The incisive canal
continues its course through the body of the
118 Vol. XX/No. Two/1994
mandible to the symphysis, where, generally, a
plexus of nerve branches forms and the main
trunk is lost (Starkie and Stewart, l93l; Carter
and Keen, l97l). Through the mental foramen
pass the mental nerve, the larger of the two
terminal nerves of the inferior alveolar, and the
mental artery and vein. At or near the orifice of
the foramen, the mental nerve divides generally
into two or three branches (Gray, 1977), and as
many as five have been observed by this writer. In
rare occasions, the mental foramen may be absent
(de Freitas et aL., f 979).
(Brash and
Many standard textbooks
Jamieson, 1943; Grant, 1958; Thoma, 1969;
Romanes. 1972: Hiatt and Gartner. 1987:
Bennett, 1988; DuBrul, f 988) continue to list the
location of the mental foramen inaccurately as
between the apices of the first and second
mandibular premolar teeth, usually just below the
apex of the first premolar (El-Najjar and
McWilliams, 1978), or below the premolar region
(Bass, 1987: White and Folkens, l99r).
The purpose of this study was to determine the
most common (modal) position of the mental
foramen in Asian Indians. This informatlon is
important because, to this writer's knowledge, it
has not been reported as of yet in this group of
humans. In addition, accurate location of the
mental foramen in this and other populations is