
Part I of William Harrell’s article (Orthotown Magazine, November 2009) on 3D imaging looked at the traditional 2D imaging of two similar cases (Class I Bimaxillary Protrusion). Part II reveals the three-dimensional diagnostic information. Does the 3D information change your treatment plan in any way and/or reveal additional information, which could be important to know in the overall management of these cases?
Case 1
The following is the three-dimensional information on Case 1 (read Part I of Dr. Harrell’s series in the November issue of Orthotown Magazine here). The CBCT data can be reformatted to reveal Axial, Coronal and Sagittal views and also Rendered 3D volumes.
Now, do you consider this case “routine“ by the 3D information you see here? Did this information “change your treatment plan?“ What are your treatment plan(s) now after seeing the 3D information?
Notice the “perceived root length“ of the upper incisors in
the panoramic view (Figure 1B) and compare this to the cross
sectional information of the incisors in Figures 3A – 3E. Note
the protrusive upper incisors, conical root anatomy and the 1:1
crown to root ratio of upper centrals (normal is 1:2 crown-to-root
ratio).8 Note the protrusive lower anterior teeth and small
labio-lingual width of the alveolar bone that houses the lower
incisors. The root thickness seems to be close to the same width
as the labio-lingual alveolar bone. Does this information change
your treatment plan in any way?
The following figures are 3dMD (3dMD, Atlanta, GA)
facial scan showing this patient in various perspectives. The initial
treatment plan I was considering on clinical exam was
extraction of four first bicuspids and four TADS to maximally
retract the incisors to reduce the bimaxillary protrusion and
retract the “full lips.“ After reviewing the 3D information, especially
the cross-sections of the upper and lower incisors, I chose
to treat this case non-extraction, align her teeth and close
diastema, leave her lips full, at this time. Then when she is older
(16-18 years old), if the patient so desires, consider a genioplasty.
Note the “lack of full lips“ when the chin is moved forward
in the 3D facial scans in Figures 3F-3I.
Case 2
The following is the three-dimensional information on Case 2
(read Part I of Dr. Harrell’s series in the November issue of
Orthotown Magazine). The CBCT data can be reformatted to reveal
Axial, Coronal and Sagittal views and also Rendered 3D volumes.
Now, do you consider this case “routine“ by the 3D information
you see here?
Did this information “change your treatment plan“?
What are your treatment plan(s) now after seeing the
3D information?
Note in this case that her upper incisor crown to root ration
is 1:2, which is normal8 and there seems to be enough labio-lingual
alveolar thickness in order to “retract“ the lower anterior teeth. So in this instance I would consider four first bicuspids
and TADs to retract the anterior teeth and reduce lip fullness.
Upon further evaluation of the DICOM data, this patient’s
airway seemed to be small due to enlarged tonsils and adenoids
(See Figures 4G - I). Does this “incidental“ information make
any difference in the overall treatment plan? What are the possible
long term effects of respiratory pattern on craniofacial
growth?9 The relationship between the amount of nasal obstruction
which has to be present before it effects facial growth is still
not clear.10 This dichotomy might be related to the imaging
modalities used and measured in earlier studies (i.e. 2D lateral
cephalometrics) versus what we might find when looking at the
three-dimensional airway and studying the air flow and turbulence
patterns created with various airway conditions and its
possible effects on growth.
This two-part article shows two similar cases which most
orthodontists would consider “routine“ and not necessarily in need
for 3D information. After considering the 3D information, the
treatment plan on case 1 changed from four bicuspid extraction
and maximum retraction to non-extraction and a genioplasty.
Case 2 led to referral to ENT for tonsil and adenoidectomy.
You don’t know what you don’t know, you don’t know what
you can’t see and what you can’t see, you cannot diagnose!
“Routine cases“ might not be as routine as we think. It is better
to know than not to know what the anatomic truth really is. 3D
imaging might help keep us out of trouble.
References
8. Grossmann Y, Sadan A. The prosthodontic concept of crown-to-root ratio: A
review of the literature. J Prosthet Dent 2005; 93:559-62
9. McNamara, JA, Influence of respiratory pattern on craniofacial growth, Angle
Orthodontist, Oct 1981 (Vol. 51, Issue 4, Pages 269-300)
10. Vig KWL , Nasal obstruction and facial growth: the strength of evidence for
clinical assumptions, AJODO, June 1998 (vol 113, Issue 6, pgs 603-611
11. Ogawa et al. “ Evaluation of cross-section airway configuration of obstructive
sleep apnea.“ Oral Surg, Oral Med Oral Path 103;2007:102-8
12. Lowe AA, Gionhaku N, Takeuchi K and Fleetham JA. “ Three-dimensional
CT reconstructions of tongue and airway in adult subjects with obstructive sleep
apnea.“ Am J Orthod Dentofacial Orthop.“ 1986;90(5) 364-74
13. Avrahami E, Englender, M. “ Relation between CT axial cross-sectional area of
the oropharynx and obstructive sleep apnea syndrome in adults. Am J
Neuroradiol. 1995;16(1):135-40
14. Consentini T, Le Donne R, Mancini D, Colavita N. “ Magnetic resonance
imaging of the upper airway in obstructive sleep apnea. Radiol Med
2004;108:404-16
15. Li HY, Chen NH, Wang CR, Shu YH, Wang PC. “Use of 3-dimensional computed
tomography scan to evaluate upper airway patency for patients undergoing
sleep-disordered breathing surgery.“ Otolaryngol Head Neck Surg
2003;1294):336-42 |
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