3D Diagnosis and Treatment Planning in Orthodontics

3D Diagnosis and Treatment Planning in Orthodontics

3D Diagnosis and Treatment Planning in Orthodontics William E. Harrell, Jr. The goal of diagnosis and treatment planning in orthodontics is to plan a ...

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3D Diagnosis and Treatment Planning in Orthodontics William E. Harrell, Jr. The goal of diagnosis and treatment planning in orthodontics is to plan a course of treatment based on the initial condition of the patient’s problem(s) (ie, a problem list) and the “end of treatment” goal determined by the patient (or parents) and the orthodontist. Accurate imaging is a central part of the diagnostic and treatment planning process and also important in monitoring and documenting the treatment progress and the final outcome. Diagnostic imaging has been a part of the orthodontic patient record for decades, which has normally included two-dimensional (2D) cephalometric imaging and tracings and panoramic imaging along with 2D photographs. Traditional 3D data has been confined to study models of the teeth (plaster and more recently digital). These data sets have not been coregistered into an accurate 3D representation of the patient’s anatomy. Accurate diagnosis is the key to treatment planning and eventual treatment itself. It is essential to analyze accurate imaging data that represents the “anatomic truth” of the patient’s real anatomy. (Semin Orthod 2009;15:35-41.) © 2009 Elsevier Inc. All rights reserved.

wo-dimensional (2D) imaging has been the standard of documentation and standard of care on which numerous diagnostic analyses have been created. They include such analyses as Downs,1 Steiner,2 Tweed,3 Ricketts and colleagues,4,5 Jacobson’s WITS analysis,6 McNamara,7 and soft tissue analyses such as: Farkas,8 the Farkas/Mayes 3D facial analysis (Mayes J, personal communication, 2003), Arnett and Bergman,9 Sarver,10 and Idiculla and colleagues.11 Limitations of 2D cephalometrics have been well known since its introduction by Broadbent12 and Horfrath13 in 1931 and more recently reported by Adams and colleagues14 and Moshiri and colleagues.15 Sarver has also reported on the limitations of combining the 2D lateral cephalometric radiograph with the 2D video image process. Sarver

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Private Practice, Alexander City, AL. Address correspondence to Dr. William Edward Harrell, 125 Alison Dr., Suite 1-A Medical Arts Building, Alexander City, AL 35010. Phone: 256-234-6353; Fax: 256-234-6713; E-mail: drharrell@ aol.com © 2009 Elsevier Inc. All rights reserved. 1073-8746/09/1501-0$30.00/0 doi:10.1053/j.sodo.2008.09.004

states that “if the coordinated video cephalometric images cannot be translated into real-life measurements, then the treatment planning process has no quantitative validity.”10 Johnston in 196816 also cites the inaccuracies and inherent errors of the 2D cephalometric techniques; specifically he discusses prediction: “The ultimate accuracy of cephalometric prediction may be limited not so much by the availability of significant information, as by the error intrinsic to the method itself.” Evidence-based dental practice17-20 is a worthy goal for the dental and orthodontic professions. Evidence-based practice should be divided into three areas: (1) evidence-based diagnosis (EBD); (2) evidence-based treatment planning (EBTP); and (3) evidence-based treatment (EBT).21 Evidence-based diagnosis (EBD) should be based on the best available data and information of the time. Imaging should represent the true anatomic relationships (both in spatial and time dimensions along with the biomechanical truth) so that the diagnosis is based on accurate data and information. EBTP and EBT should also be based on the best available diagnostic data and information of the time. There are many differ-

Seminars in Orthodontics, Vol 15, No 1 (March), 2009: pp 35-41

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Figure 1. (A) Adult Class II division 1 malocclusion with mandibular deficiency and protrusive maxillary incisors. Initial treatment plan was a mandibular advancement. Patient refused surgery, so an alternative treatment plan was to extract maxillary first bicuspids and use anchorage devices attached to the zygomatic region and attachments cantilevered into the vestibule at the level of the maxillary first molars. These anchorage devices were used to maximally retract the incisors. (B) Final result of alternative treatment plan. Note the acceptable facial and dental changes. (C) Three-dimensional (3D) facial scans (3dMD, 3D Face System, Atlanta, GA) were used to document the 3D facial changes before and after treatment. The two face scans were coregistered in the glabella/forehead area (an area that is relatively stable). The color histogram shows the 3D facial changes. Note the variations in the green color representing the volumetric changes in lip fullness before and after treatment. Some asymmetrical changes can be noted in the area of the right corner of the mouth versus the left. (Color version of figure is available online.)

ent types of “treatment philosophies” in orthodontics and dentistry. Some are based on extensive clinical research, experience, expertise, and scientific research, while some are not and are based on anecdotal findings. What is effective for one practitioner may not be as effective for another. The goals of both orthodontists may be the same endpoint (ie, Class I occlusion [cuspids and/or molars], good face, nice smile, straight teeth, etc.) but they may achieve this differently or may arrive at a totally different end result, which may or may not be an acceptable treatment result. An example of two entirely different plans, which may still be acceptable, is an adult patient who has a mandibular deficiency and a retrognathic profile but who rejects

a mandibular advancement surgical treatment plan and elects instead to have maxillary first bicuspid teeth extracted and traditional orthodontic treatment mechanics or with the aid of temporary anchorage devices (TADs) to reduce the protrusion of the upper incisor teeth (Fig 1). The end-of-treatment goal for a given patient may have to be altered due to poor growth, poor cooperation, misdiagnosis, patient acceptance or nonacceptance of a particular treatment plan, and so on. As “evidence” increases with better diagnostic tools, (ie, 3D and 4D imaging, along with true biomechanical data and improved software development), treatment planning and treatment may become more consistent between practitioners. In addition, it will allow for the patients

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Figure 2. Cone beam computed tomography scan can be used to evaluate developing arch length problems. Measurements of both erupted and unerupted teeth as well as the arch length available can be analyzed and the appropriate timing of an orthodontic course of action can be determined by the practitioner. (Color version of figure is available online.)

and/or parents to better appreciate the situation and may help them understand the treatment alternatives, limitations, and cooperation needed for a more predictable treatment outcome. Working from the same accurate starting point (3D diagnostic imaging) may allow for the practitioners to consider more predictable courses of treatment based on evidence and not on subjective anecdotal findings.

How Might an Orthodontist Use 3D Technology on Routine Patients in Private Practice? Technologies, such as cone beam computed tomography (CBCT) and 3D facial imaging, are presently being used and developed that will allow 3D imaging to be done on orthodontic patients to provide an accurate representation of the anatomy. The following are some of the applications of 3D imaging presently being used and that may become “standard of care” in the near future:

Orthodontic Treatment Planning Using 3D will allow the orthodontist to automatically measure such things as the Bolton tooth size and arch length discrepancy quickly and

accurately (Fig 2). This information can also allow for evaluation of different treatment options, such as different extraction patterns (serial extraction versus later phase extraction) and for minimum, moderate, or maximum anchorage requirements. It will allow for the evaluation of possible expansion or uprighting of buccal and/or anterior segments, and/or interproximal stripping to gain arch length. In nonextraction cases, if the treatment plan calls for expansion or uprighting of the dental or skeletal arches, then the gains in arch length can be measured by the computer, and the orthodontist can decide if this treatment fits into the treatment scheme. The following accounting is of a patient who had a chief complaint of a narrow smile and crooked teeth. The lingually inclined buccal segments are evident along with the “dark buccal corridors” (Fig 3A) The diagnostic image slice in Fig 3B is a coronal section of the CBCT scan showing the lingual inclination of the buccal segments and the proximity of the buccal roots to the buccal cortical plate. Figure 3C shows the final 3D smiling face and Figure 3D the coronal cross-sections of the buccal segments, now upright over the basal bone. The orthodontist will also be able to evaluate what effects different treatment plans may have on the face in three dimensions. Treatment planning from the “outside in” may become the standard of treatment planning. In other words, evaluating the 3D facial surface and deciding what is the “best face” that can be achieved and then deciding which orthodontic and/or surgical treatment may be best for the individual patient. By having physiological attachments of the bone and teeth (“springs and coils”) to the facial surface the orthodontist and/or surgeon together can decide the best course of action (Fig 4).

Monitoring Treatment over Time The ability for the clinician to better visualize the end-of-treatment goal is attainable with 3D imaging. It is important to move the teeth in relation to the needs of the face and soft tissues, along with dental stability and temporomandibular position, so that the practitioner can treat the whole patient and not just the teeth. Accurate treatment monitoring over time is a signif-

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Figure 3. (A) The 45° upward smiling view of the patient’s 3dMD face scan showing the narrow buccal segments and “dark corridors.” (B) The corresponding diagnostic X-ray image is a coronal cross-section of cone beam computed tomography (CBCT) scan through the bicuspid area, showing the lingual inclination of these teeth and the proximity to the cortical bone, (see red arrows). (C) The 45° upward smile view of the paitent’s final 3D face showing a fuller smile with upright posterior buccal segments. (D) The corresponding diagnostic image is a coronal cross-section of final CBCT scan through the bicuspid area, showing more upright posterior segments and the location of the roots into the alveolar bone. Orthodontic biomechanics to torque the buccal segments (lingual root torque and buccal crown torque) would not only place the roots in a more desirable position but decrease the “dark buccal corridors” of the smile. (Color version of figure is available online.)

icant advantage of 3D imaging. Asymmetries are always present and can affect the end result. These are best documented before treatment begins, as compromises may need to be addressed.

Impacted Cuspid Teeth An orthodontist can use a 3D reconstructed digital model, from cone beam data, of impacted cuspid teeth to evaluate the vector of

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Figure 4. (A) An example of a Class III surgical patient, with an anterior vertical excess. The cone beam computed tomography (CBCT) scan (iCAT, Imaging Sciences, Hatfield, PA) has been coregistered with the 3D facial scan (3dMD, Atlanta, GA) in 3dMD Vultus software (3dMD). (B) Physiologic “springs and coils” are shown, which attaches the facial soft tissue to the CBCT bones and teeth. (C) Surgical simulation of craniofacial structures with mandibular setback and vertical chin reduction. (D) The 3D facial soft tissue changes are shown as a color histogram of the coregistered initial 3D face scan compared with the surgical simulation. The amount of volumetric facial changes is shown and can be measured. (Color version of figure is available online.)

force and positioning of the bracket needed to move the cuspid into proper position without impinging on the surrounding teeth, such as the maxillary central and lateral incisor roots (Fig 5). True 3D analysis and treatment planning can be made on digital computer models of the patient’s anatomy (a patient specific anatomic reconstruction [PSAR]; Fig 6), which may include teeth, skeletal structure, and facial soft tissue, along with photo textures. This type of 3D output to the orthodontist can be viewed from any angle, sliced, or made transparent to reveal underlying anatomy, individual teeth, and sections of bones. It can be adjusted by the orth-

Figure 5. Note the position of the impacted canines and the root resorption already evident on the lateral incisors. Movement of the cuspids will be distally, away from the lateral incisor roots before these teeth are brought into the arch. (Color version of figure is available online.)

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Figure 6. True three-dimensional analysis and treatment planning can be made on digital computer models of patient anatomy. (Color version of figure is available online.)

odontist for both orthodontic and orthognathic surgery treatment planning purposes. Orthodontics is beginning a path toward more accurate diagnosis and treatment planning.

References 1. Downs WB: The role of cephalometrics in orthodontic case analysis and diagnosis. Am J Orthod 38:162-182, 1952 2. Steiner CC: The use of cephalometrics as an aid to planning and assessing orthodontic treatment. Am J Orthod 46:721, 1960 3. Tweed CH: The Frankfort mandibular incisor angle (FMIA) in orthodontic diagnosis, treatment planning and prognosis. Angle Orthod 24:121-169, 1954 4. Ricketts RM: Planning treatment on the basis of the facial pattern and an estimate of its growth. Angle Orthod 27:14-37, 1957 5. Ricketts RM, Roth RH, Chaconas SJ, Schulhof RJ, Engel GA: Orthodontic Diagnosis and Planning. Vol. 1. Denver, Rocky Mountain Data Systems, Rocky Mountain Orthodontics, 1982 6. Jacobson A: The “WITS” appraisal of jaw disharmony. Am J Orthod 67:125138, 1975 7. McNamara JA Jr: A method of cephalometric evaluation. Am J Orthod 86:449-469, 1984 8. Farkas LG: In: Farkas LG, ed: Anthropometry of the Head and Face 2nd ed. New York, Raven Press, 1994 9. Arnett GW, Bergman RT: Facial keys to orthodontic diagnosis and treatment planning. Part I. Am J Orthod Dentofacial Orthop 103:299-312, 1993 10. Sarver DM: Esthetic Orthodontics and Orthognathic Surgery. St Louis, Mosby, 1998 11. Idiculla AJ, Harrell WE, Ayala J, O’Brien JM, Secchi AG: 3-dimensional morphometric facial analysis to determine the effects of altering the occlusal vertical dimension.Masters thesis, University of Pennsylvania, 2006

12. Broadbent BH: A new x-ray technique and its application to orthodontia. Angle Orthod 45-46, 1931 13. Horfrath H: Bedeutung der Roentrenfern und Abstands Aufnahme fur die Diagnostik der Kieferanomalien. Fortschr der Orthod 1:231-238, 1931 14. Adams GL, Gansky SA, Miller AJ, Harrell WE, Hatcher DC: Comparison between traditional 3-dimensional cephalometry and a 3-dimensional approach on human dry skulls. Am J Orthod Dentofacial Orthop 126:397409, 2004 15. Moshiri M, Scarfe WC, Hilgers ML, Scheetz JP, Silveira AM, Farman AG: Accuracy of linear measurements from imaging plate and lateral cephalometric images derived from cone-beam computed tomography. Am J Orthod Dentofacial Orthop 132:550-560, 2007 16. Johnston LE: A statistical evaluation of cephalometric prediction. Am J Orthod Dentofacial Orthop 38:284304, 1968 17. Shortliffe E, Perreault LE, Wiederhold G, Fagan LM: Medical Informatics: Computer Applications in Health Care and Biomedicine. 2nd ed. New York, Springer, 2001 18. Harrell WE, Hatcher DC, Bolt RL: In search of anatomic truth: 3-dimensional digital modeling and the future of orthodontics. Am J Orthod Dentofacial Orthop 122:325330, 2002 19. Harrell WE, Stanford S, Bralower P: ADA initiates development of orthodontic informatic standards. Am J Orthod Dentofacial Orthop 128:153-156, 2005 20. Ackerman M: Evidence-based orthodontics for the 21st century. J Am Dent Assoc 135:162-167, 2004 (ADA policy on evidence-based dentistry available at http://www.ada.org/ prof/resources/positions/statements/evidencebased. asp) accessed 1/25/2008 21. Harrell WE: Three-dimensional diagnosis and treatment planning: the use of 3D facial imaging and 3D conebeam CT in orthodontics and dentistry. Austral Asian Dent Pract J July/August, 2007