O r t h o d o n t i c P re p a r a t i o n f o r Or t h o g n a t h i c S u r g e r y Brent E. Larson, DDS, MS KEYWORDS Orthodontics Orthognathic surgery Treatment planning
KEY POINTS Orthodontic preparation is critical to the success of orthognathic surgery. Recognition and correction of existing dental compensations allows full correction of skeletal discrepancies. Presurgical orthodontic goals are important to define at the start of treatment and may not always include complete arch leveling or space closure, or ideal interdigitation. Orthodontic preparation dictates the skeletal movements that are possible at the time of surgery. Different malocclusion types have characteristic dental compensations that can be identified and described. Proper planning, monitoring, and communication between surgeon and orthodontist are critical to avoid potential pitfalls in the orthodontic preparation.
INTRODUCTION
PRESURGICAL GOALS
Proper orthodontic preparation is critical to the outcome of orthognathic surgical treatment (Box 1, Table 1). All orthodontic tooth movement should be planned before treatment, even if some movements are completed after the surgery. The ultimate goal is to create a situation in which the teeth are in proper position relative to their underlying skeletal bases.1 This goal creates a presurgical dental discrepancy that is at least as great as the skeletal discrepancy so that the occlusion acts as a guide for the surgeon to produce the optimal position of the skeletal parts during surgery. Because normal physiologic processes tend to compensate for the skeletal problem, significant tooth movement is generally needed to create the most esthetic and balanced outcome for the patient. Patients undergoing orthognathic treatment with orthodontic preparation should be well informed about the orthodontic procedures and what to expect from treatment and retention.2
There is no universal agreement among orthodontists and surgeons about the goals of orthodontic treatment before surgery. Some teams prefer nearly ideal interdigitation of presurgical plaster models before proceeding, whereas others are content to do the detailed finishing after surgery. In general, the guiding principle is that the teeth need to be moved sufficiently to allow the maxilla and mandible to be put in the desired position.3 If this general principle is used as a guide, it is possible to define certain parameters of presurgical goals.
Natural physiologic adaptation, or previous orthodontic treatment, often places teeth in a position that reduces the dental discrepancy compared with the skeletal difference. This adaptation, or compensation, needs to be removed before surgery. An example is the need to upright the lower
Disclosures: None. Division of Orthodontics, School of Dentistry, University of Minnesota, 6-320 Moos Tower, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA E-mail address: [email protected] Oral Maxillofacial Surg Clin N Am 26 (2014) 441–458 http://dx.doi.org/10.1016/j.coms.2014.08.002 1042-3699/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.
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Box 1 General concepts of orthodontic preparation for orthognathic surgery Three Concepts and a Corollary 1. Whenever possible, treatment should be planned so that the orthodontic and surgical relapse tendencies are in opposite directions. 2. Incisors should be positioned relative to their respective skeletal bases rather than external references. 3. Tooth movement is usually in the exact opposite direction for surgical versus nonsurgical treatment. Corollary: starting treatment without deciding whether to treat with or without surgery is generally a bad idea.
incisors in a class II patient in whom the incisors were initially proclined to minimize the overjet.
Alignment of Arches Gross crowding, spaces, or rotations are corrected.
Coordinate Arches If the maxilla and mandible are to be treated as single pieces, the shape and dimensions are made compatible so that they will occlude reasonably following surgery. If one or both jaws are to be treated segmentally, the individual segments should be arranged so that the arches will be compatible following the planned surgical movement of the segments. The general principle is that the teeth must not interfere with the planned skeletal movement, and they must be within reasonable distance for postsurgical orthodontic finishing. This principle means that not all orthodontic movement must be complete before surgery. For this reason it is also important to consider what the presurgical goals may not be.
Table 1 Goals of presurgical orthodontics (see text for complete description) Should Include
May Not Include
Decompensation of dentition Alignment of arches
Full closure of all spaces Perfect occlusion of surgical models Leveling of arches
Coordination of arches
Full Closure of All Spaces Some spacing may be desirable at the time of surgery to allow extra overjet to ensure canine seating (eg, distal to upper lateral incisors) or to allow room for postsurgical leveling without forward movement of the lower incisors. A small degree of spacing also creates flexibility during postsurgical finishing to create optimal occlusal relationships if the surgical outcome deviates from the plan.
Perfect Occlusion of Surgical Models Ideal occlusion may be the desired end result, but spending a great deal of time to achieve this perfection before surgery and then again after surgery may increase treatment time. It has been reported that the orthodontic preparation for surgery averages 17 months.4 In addition, some tooth movements can be accomplished most efficiently after surgery. For example, proclining lower incisors to decompensate a class III malocclusion can be faster and easier following surgery when soft tissue pressures are working with the desired tooth movement rather than against it.5
Leveling of Arches The decision whether to level the lower arch before or after surgery should be based on planning for the desired vertical change. Presurgical leveling allows mandibular advancement with minimal clockwise rotation of the mandibular, which helps promote horizontal movement and chin prominence. However, maintaining the curve of Spee requires the creation of a tripod occlusion on the incisors and molars at the time of surgery, which increases the vertical dimension and increases clockwise rotation. In some cases, this postsurgical leveling produces more desirable vertical changes and minimizes chin prominence, and trying to produce a perfect occlusion at the time of surgery prevents the optimal outcome. It is important to understand that the decision to level or not to level the lower arch before surgery has an important impact on the final chin position and lower face height (see Figs. 2 and 7).6
THREE CONCEPTS AND A COROLLARY FOR ORTHODONTIC PREPARATION Whenever Possible, Treatment Should Be Planned so that the Orthodontic and Surgical Relapse Tendencies Are in Opposite Directions The idea is to be well informed regarding possible posttreatment changes that will affect the stability of the final correction. When possible, it makes sense to plan orthodontic movements in a direction that causes any orthodontic change to be in
Orthodontic Preparation for Orthognathic Surgery the opposite direction to the expected surgical change. For example, if the maxilla is to be surgically expanded in a transverse direction, the surgical posttreatment tendency is to narrow slightly after treatment.7 Expanding the maxillary dentition orthodontically, either intentionally or inadvertently, has a relapse tendency in the same direction and therefore is additive to the surgical change. In contrast, if the arch is constricted orthodontically, the orthodontic relapse tends to expand the arch slightly. If this is combined with a surgical tendency to narrow, the resultant changes are offsetting rather than additive and greatly contribute to the stability. This same concept applies to the vertical position of incisors when preparing to surgically correct an anterior open bite. The preferred movement is to intrude the incisors further before surgery so that after treatment their tendency to slightly extrude offsets any skeletal tendency for recurrence of the open bite.
Incisors Should Be Positioned Relative to Their Respective Skeletal Bases Rather than External References Orthodontists are used to making judgments of dental position from cephalometric radiographs. Often the inclination of incisors is made to cranial base references (eg, Upper Incisor [U1]–SellaNasion [SN]) or other more distant landmarks (eg, U1–NA). Because these references may change as a result of the planned surgery, the outcome may not be what was envisioned if these distant references are used. This could happen if the upper incisor inclination was planned relative to the SN plane, but maxillary impaction is done with the posterior maxilla impacted more than the anterior. In this case, an ideal presurgical inclination relative to SN results in upper incisors that are more upright than desired after the differential impaction. Planning the incisor inclination relative to the palatal plane may be more appropriate because the palatal plane moves with the incisors during surgery.
Tooth Movement in Preparation for Surgery is Usually in the Opposite Direction to that for Nonsurgical Treatment In general, the lower incisors are proclined in class II patients because of the compensation described earlier. If the orthodontist treats a class II patient without surgery, the compensations are maintained, or even increased, during treatment. For a surgical treatment plan the lower incisors are retroclined to remove the compensation and to put them in ideal position relative to the skeletal base. This means incisor proclination for nonsurgical treatment versus retroclination for a surgical
plan. The same concept applies in the transverse plane and vertical plane for other problems. This observation that the direction of movement is opposite for surgical and nonsurgical solutions leads to the corollary. Starting treatment without deciding whether to treat with or without surgery is generally a bad idea.
TECHNIQUE/PROCEDURE The application of these concepts is shown by example in the most frequently encountered types of surgical setups.
Class II: High or Normal Mandibular Plane Angle Treated with Surgical Mandibular Advancement These patients are generally characterized by an increased mandibular plane angle, a retrusive mandible and chin, and lower face height that is normal or slightly increased. The most common dental compensations are proclined lower incisors and a slightly narrow maxillary dental arch caused by the maxillary teeth occluding with a narrower part of the mandible than ideal. Example: patient A.G. (Fig. 1). Problem list 1. Skeletal class II 2. High angle tendency 3. Severe chin deficiency 4. Upper and lower arch crowding 5. Dental compensations a. Mildly proclined lower incisors b. Increased lower arch curve of Spee Important considerations to prepare A.G. for mandibular advancement. Maintain upper incisor position: based on clinical assessment of incisor display at rest and at smile as well as cephalometric analysis and treatment simulation (Fig. 2). Maximize forward chin movement with surgery: requires pretreatment leveling to allow advancement along the occlusal plane without clockwise distal segment rotation (see comparison in Fig. 2). Resolve upper and lower crowding without change in upper incisor position, and maintain or upright lower incisor. Requires extraction of lower premolars. Treatment results and impact of orthodontic preparation The results of treatment of A.G. are shown in the photographs and in the cephalometric
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Fig. 1. Patient A.G. before treatment.
superimposition in Figs. 3 and 4. Proper planning and mechanics allowed resolution of the crowding without significant change in incisor inclination, which required premolar extraction in the lower arch to provide arch space and archform change in the maxilla with vertical upper incisor control. Pretreatment leveling of the lower arch resulted in the desired mandibular advancement along the occlusal plane without the distal segment rotation that would have increased the mandibular plane angle. A dramatic improvement in the facial profile was achieved by maximizing the forward chin expression and adding an additional genioplasty (Fig. 5).
Class II high angle: orthodontic preparation tips Determine upper incisor position (usually procline); vertical placement determined by smile arc Plan lower incisor target (usually uprighting to remove compensation); often requires lower premolar extraction to achieve incisor target Orthodontically level before surgery to maximize forward chin projection and minimize increase in lower face height (see Fig. 2)
Fig. 2. Difference between postsurgical leveling (A) and presurgical leveling (B) for patient A.G. Note the distinct difference in the movement of the chin (arrows) with the same amount of molar advancement.
Orthodontic Preparation for Orthognathic Surgery
Fig. 3. Treatment changes for patient A.G. Note the leveling of the lower arch by incisor intrusion and the resulting forward movement of the chin (genioplasty added). Also, the upper incisor position was largely unchanged as per the original treatment plan.
Class II: Low Mandibular Plane Angle Treated with Surgical Mandibular Advancement These patients are generally characterized by a decreased mandibular plane angle, a retrusive mandible with a well-developed chin, and a reduced lower face height. The mentolabial fold is often accentuated. The most common dental
compensations are a class II division 2 incisor appearance with the characteristic upright upper incisors and dental deep bite. Like other class II patients, they may have a slightly narrow maxillary dental arch caused by the maxillary teeth occluding with a narrower part of the mandibular arch.
Fig. 4. Final facial and intraoral views of patient A.G. The molar relationship is class III and canines are class I, which was the result of the removal of lower premolars to position the lower incisors properly.
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Fig. 5. Patient A.G. before (A) and after (B) treatment in profile view.
Example: patient R.P. (Fig. 6) Problem list 1. Class II division 2 dental relationship 2. Class II skeletal: mandibular deficiency 3. Slightly reduced lower face height: welldeveloped chin 4. Mild upper and lower crowding 5. Dental compensations a. Very upright upper incisors b. Increased lower curve of Spee 6. Previously extracted lower incisor
Fig. 6. Patient R.P. before treatment.
Important considerations to prepare R.P. for mandibular advancement: Procline upper incisor: based on clinical assessment of incisor display at rest and at smile as well as cephalometric analysis and treatment simulation. Direct chin forward and downward with surgery: requires posttreatment leveling to allow advancement with clockwise distal segment rotation (see comparison in Fig. 7).
Orthodontic Preparation for Orthognathic Surgery
Fig. 7. Difference between presurgical leveling (A) and postsurgical leveling (B) for patient R.P. Note the distinct difference in the movement of the chin (arrows) with the same amount of molar advancement. Postsurgical leveling provides better profile change by increasing lower face height and minimizing the chin advancement.
Resolve upper and lower crowding while providing the desired upper incisor position; maintain or upright lower incisor. Requires no extraction of premolars to meet target because lower incisor previously removed. Removal of third molars at the beginning of treatment to allow complete healing before surgery. Treatment results and impact of orthodontic preparation Fig. 8 top row shows the appearance of R.P. before surgery with very different upper and lower
occlusal planes because of planned postsurgical leveling. These divergent planes are managed during surgery with the planned distal segment and made possible by a surgical setup that provides a tripod contact only on incisors and molars. Postsurgical leveling happened rapidly because the lower arch was leveled into open space rather than against occlusal contact. The results of the treatment of R.P are shown at the bottom of Fig. 8 and in Fig. 9. The upper incisors were proclined into the desired position for smile esthetics and the surgical rotation decreased the mentolabial fold and avoided excess chin prominence.
Fig. 8. Patient R.P. before surgery (top) and after treatment (bottom). Note the divergent upper and lower occlusal planes before surgery, showing the intentional lack of leveling, and then the coincident occlusal planes after treatment when the lower arch is leveled to match the upper.
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Fig. 9. Patient R.P. before (A) and after (B) treatment in profile view. Note subtle improvement in profile from proper planning of mandibular advancement surgery.
Class II low angle: orthodontic preparation tips Determine upper incisor position: usually requires proclination; vertical placement determined by smile arc. Plan lower incisor target: often requires lower premolar extraction to provide lower incisor uprighting. Level after surgery to increase lower face height, open mentolabial fold, and reduce increase in chin projection (see Fig. 7).
Class III: Treated with Surgical Maxillary Advancement and/or Mandibular Setback Class III patients needing surgery present with some combination of maxillary deficiency and/or mandibular excess. The specific surgical procedures to correct the disharmony are selected by the surgeon, orthodontist, and patient based on facial esthetics, airway concerns, and dental arch widths (ie, if expansion is needed, a maxillary surgery is most desirable). The characteristic incisor compensations that must be removed are proclined upper incisors and retroclined lower incisors. There is often an element of transverse compensation with the maxillary posterior teeth buccally inclined and the mandibular teeth lingually inclined. It is important to recognize the compensations in all planes of space to properly plan treatment. Patients who present with a
component of mandibular excess also often have some degree of mandibular asymmetry. Assessment of dental and skeletal midlines by careful examination or cone beam computed tomography (CBCT) analysis is critical. Example: patient E.B. (Fig. 10) Problem list 1. Skeletal class III, maxillary deficient 2. High mandibular plane angle 3. Bilateral posterior crossbite 4. Upper and lower arch crowding 5. Dental compensations a. Mildly proclined upper incisors b. Retroclined lower incisors Important preparation:
considerations
for
orthodontic
Maintain or upright upper incisors: based on clinical assessment of E.B.’s smile, and cephalometric analysis. Procline lower incisors to decompensate and create space for alignment. Use class II elastics presurgically to help with decompensation. Create negative overjet equal to the underlying skeletal discrepancy to allow full surgical correction. Fig. 11 show the difference in skeletal change that occurs with adequate incisor decompensation. Removal of third molars at the beginning of treatment to allow complete healing before surgery.
Orthodontic Preparation for Orthognathic Surgery
Fig. 10. Patient E.B. before treatment.
Treatment results and impact of orthodontic preparation Photographs of the treatment finish show the esthetic improvement obtained with full correction of the skeletal position (Fig. 12). There was not a significant lower curve of Spee so the arches could be well coordinated before surgery. The upper incisors were maintained in their pretreatment inclination and the lower incisors proclined to decompensate. The vertical control of incisor position was important during orthodontic preparation to maximize smile esthetics and control the anterior face height.
Class III: orthodontic preparation tips Determine upper incisor position: usually retrocline and vertical placement determined by smile arc; may require premolar extractions to decompensate Plan lower incisor target: usually significant proclination is required to remove compensation; usually nonextraction to meet incisor target Must consider transverse: incomplete anteroposterior correction leads to relative transverse problem
Fig. 11. Difference between no incisor decompensation (A) and presurgical incisor decompensation (B) for patient E.B. The magnitude of surgical movement of the maxilla (arrows) is nearly 3 times with proper incisor decompensation. This decompensation allows full correction of the skeletal deformity (B).
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Fig. 12. Patient E.B. before (A) and after (B) treatment in profile view.
Vertical Maxillary Excess Treated with Surgical Maxillary Impaction Patients opting for surgery to correct skeletal vertical maxillary excess usually present with excessive incisor display at repose and excessive gingival display at full smile. The downward position of the maxilla results in downward and backward rotation of the mandible so that the lower face height is increased and the mandibular plane angle is also increased. The incisor compensation is variable and must be carefully assessed, but often the lower
incisor is proclined if the mandibular rotation has resulted in a class II condition. An anterior open bite may be present but is not always seen. Example: patient M.O. (Fig. 13) Problem list 1. Increasing gingival display on smile 2. Anterior dental open bite 3. Facial convexity with an increase in lower face height 4. Late vertical growth following previous orthodontic treatment
Fig. 13. Patient B.O. before treatment, showing increase in vertical maxillary excess from age 13 years and 6 months to 16 years and 2 months.
Orthodontic Preparation for Orthognathic Surgery 5. Dental compensations a. Mildly upright upper incisors b. Mildly proclined lower incisors Important preparation.
considerations
for
orthodontic
Plan desired final U1 position: consider active upper lip. a. Take care not to affect upper incisors too much because this can prematurely age the face Consider that a differential maxillary impaction will tend to upright upper incisors. With M.O., this uprighting is desired (Fig. 14). Differential maxillary impaction leads to mandibular autorotation. Depending on the reference landmarks, this rotation appears to upright the mandibular incisors.
Fig. 14. Surgical planning on patient B.O. showing uprighting of upper incisors, which occurs from impacting the maxilla more posteriorly than anteriorly. Also note the upward and forward autorotation of the mandible as a result of the surgical maxillary impaction.
Treatment results and impact of orthodontic preparation Photographs of the treatment finish in profile reveal the improved facial balance from the slight reduction in lower face height combined with an advancement genioplasty (Fig. 15). The gingival display at full smile is still 3 mm, but is age appropriate along with the 3-mm tooth to lip measurement at repose. The arches were well coordinate from previous orthodontic treatment.
Fig. 15. Patient B.O. before (A) and after (B) treatment in profile view.
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Vertical maxillary excess: orthodontic preparation tips Determine upper incisor position: may be no significant inclination change required; vertical placement determine by smile arc Autorotation of mandible brings chin up and forward Avoid extrusion of incisors in open bite situations: may require segmental surgery Genioplasty often desirable for lip balance and profile improvement
Maxillary Transverse Deficiency Treated with Surgical Expansion Skeletal maxillary transverse deficiency occurs most commonly in association with other skeletal problems rather than in isolation. This skeletal discrepancy is most easily viewed and measured in a frontal section of a CBCT volume image. The typical compensations, which are often overlooked without three-dimensional imaging, include buccal tipping of upper posterior teeth and lingual tipping of lower posterior teeth. If these teeth are not decompensated before surgery, transverse stability can be a problem. On occasion, this decompensation is difficult to fully achieve presurgically. In these cases, the surgical movement should overcorrect the dental relationship to allow
Fig. 16. Patient A.C. before treatment.
postsurgical decompensation. This plane of space may be the most important plane in which to ensure that orthodontic and surgical relapse tendencies are in the opposite direction because the stability of maxillary skeletal expansion is not as favorable as that of many other orthognathic procedures.7 Example: patient A.C. (Fig. 16) Problem list 1. Bilateral posterior crossbite 2. Skeletal maxillary transverse deficiency 3. Mild class III tendency 4. Nongrowing 5. Visible posterior attrition Important preparation:
considerations
for
orthodontic
Assess inclination of upper and lower posterior teeth (Fig. 17). a. In general avoid dental expansion in upper arch: may constrict Plan overcorrection of surgical expansion to plan for expected postsurgical change.
Treatment results and impact of orthodontic preparation Photographs of the treatment finish reveal little change in facial proportions or balance at repose. The vertical position of the upper incisor is unchanged, but the broader archform fills the buccal
Orthodontic Preparation for Orthognathic Surgery
Maxillary transverse deficiency: orthodontic preparation tips Seldom the only skeletal issue: consider anteroposterior relationships and their impact on the transverse plane. Class III correction generally improves the transverse relationship but class II correction may worsen. Decompensate: tip upper molars palatally before surgical expansion. Overcorrect surgically to accommodate expected postsurgical rebound.
COMMON PITFALLS IN PREPARING SURGICAL SETUPS
Fig. 17. Coronal slice of CBCT through the upper first molars of patient A.C. showing the skeletal transverse discrepancy and the resultant posterior crossbite.
corridors to provide improved smile esthetics (Fig. 18). The posterior crossbite has been resolved and the frontal intraoral view in Fig. 18 shows optimal molar torque as a result of properly planned orthodontic preparation.
Most problems, or pitfalls, encountered in the orthodontic preparation stage of an orthognathic treatment plan are caused by failure in one of 3 categories: (1) planning, (2) monitoring, or (3) communication. Common issues in each of these categories are listed in Box 2. Most of these pitfalls are preventable if they are thoughtfully considered before treatment and the orthodontist/surgeon team is committed to following the plan. Fig. 19 shows the surgical treatment of a young man with a class II malocclusion caused by mandibular deficiency. A treatment plan was
Fig. 18. Patient A.C. following 2-piece Le Fort I surgery to transversely expand the maxilla. Note the proper molar inclination that is only possible if the skeletal base is widened sufficiently to eliminate molar compensation. In addition, smile esthetics are improved by filling buccal corridors properly.
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Box 2 Tips to avoid common pitfalls related to planning, monitoring, and communication Planning 1. Agree on surgery timing (patient, surgeon, and orthodontist) a. Start now or plan for future? If future, define decision trigger? b. Start presurgical orthodontics based on desired surgery date. 2. Consider third molar removal a. Needed before surgery? If so, when? 3. Determine specific presurgical orthodontic target: need to know which way to go a. Upper incisor position b. Lower incisor position c. Transverse coordination d. If segmental cuts, is additional space to be provided? Monitoring 1. Growth monitoring a. Serial radiographs taken at planned interval: assign to orthodontist 2. Third molar removal a. If needed, who makes sure it is done? Assign to orthodontist or surgeon 3. Monitor presurgical orthodontic progress: assign to orthodontist a. Upper incisor position: assess clinically for vertical position, progress cephalogram b. Lower incisor position: progress cephalogram c. Transverse coordination: progress models 4. Segmental cut areas: assess clinically and/or with radiographs Communication 1. Everyone knows detailed plan at the start of treatment (patient, surgeon, and orthodontist) a. Agreed on at the beginning; avoid changes without good reason 2. Oral and maxillofacial surgeon included from the beginning a. Build team confidence with patient: prove communication 3. Inform each visit: progress relative to plan a. Review expected surgical timing b. Ask about changes in personal plans/schedule that may affect timing c. Schedule tentative surgical date early, then make it happen
selected that included mandibular advancement surgery. The simulated outcome was accomplished because of good monitoring and communication between orthodontist and surgeon. The pitfall was in the planning, in which the lower incisors were not decompensated as part of the orthodontic preparation. This omission resulted in a full dental correction to class I, but the chin was directed forward only marginally. Better planning
could have incorporated incisor decompensation into the orthodontic preparation and therefore directed the mandibular advancement further forward and less downward. Another common pitfall is shown in Fig. 20. In this situation, the plan (simulated result) included uprighting of the upper and lower incisors as part of the orthodontic preparation. Because of a failure in monitoring, the planned incisor position
Orthodontic Preparation for Orthognathic Surgery
Fig. 19. Common pitfall of planning. Lack of lower incisor decompensation and presurgical leveling before mandibular advancement surgery failed to maximize forward chin movement. The plan was achieved, but more thoughtful planning could have maximized the surgical result to not only correct occlusion but to maximize facial change.
was not achieved and the surgical result left more lip fullness than was envisioned. In this situation, the plan was well documented and the communication was good, but the monitoring of the preparation was lacking. Communication failure may be the most common pitfall in the orthognathic surgical process. Although it seems simple, it takes effort to make sure that the orthodontist, surgeon, and patient are always updated on the plan and the progress relative to the plan. A simple way to make sure that this occurs is to reinforce the plan and evaluate the progress at each presurgical orthodontic
visit. Any deviation from the expected progress should be communicated to the surgeon so that there are no surprises at the time of the expected surgery. A team focus on planning, monitoring, and communication can minimize most common pitfalls that occur in preparation for surgery.
TREATMENT SIMULATION Treatment simulation is not a new concept for planning orthodontic preparation for surgical procedures. In the past, the simulation was done
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Fig. 20. Common pitfall of monitoring. The original plan included significant incisor uprighting to reduce dental protrusion. This uprighting was not accomplished before surgery so although a good occlusal result was achieved the lip protrusion was not addressed as planned.
with acetate tracings and overlays on lateral cephalometric films. The top row of Fig. 21 shows the before and after lateral views as well as the acetate simulation that was used to plan orthodontics and surgery some years ago. This method works well, but is time consuming and requires experience and an artistic touch. More contemporary
cephalometric simulation (see Fig. 21D) uses digital tools to easily simulate growth, drag and drop teeth, and allow prediction of soft tissue movements. Soft tissue prediction, although useful for patient education, is challenging and there are many potential errors that could affect the usefulness of the prediction.8
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Fig. 21. Cephalometric surgical simulation, which is useful for planning orthodontic tooth movement in preparation for surgery. The top row shows a patient before treatment (A) and after treatment (B), as well as the handdrawn acetate prediction used to plan the orthodontic and surgical treatment (C). (D) A more contemporary cephalometric surgical prediction using digital software tools.
Cephalometric simulation Advantages Fast if done with contemporary software tools Includes tooth position, jaw position, and soft tissue Can link to profile photograph Disadvantages
More recently, advanced surgical simulation methods have become available that use threedimensional imaging and sophisticated modeling (Fig. 22). Indications are that surgical simulations using CBCT data may improve surgical predictability.9 These methods are reviewed elsewhere in this issue (see articles by Swennen, and Franco, Farrell and Tucker) and are likely to become the standard in the coming years.
Two-dimensional Does not provide direct tooth position information for archform Soft tissue prediction questionable, particularly lower lip
SUMMARY Proper orthodontic preparation is critical to the success of orthognathic surgical procedures. Understanding the dental compensations that tend to be
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Fig. 22. Three views of more sophisticated imaging and software simulation tools available for simulation of surgery and the orthodontic tooth movements needed to maximize the surgical result.
associated with certain malocclusion types helps to construct an appropriate treatment plan for each individual that maximizes the surgical benefit and stability. The use of a collaborative, team approach that includes proper planning, ongoing monitoring of progress, and communication between professionals and with the patient is critical.
5.
6.
REFERENCES 1. Troy BA, Shanker S, Fields HW, et al. Comparison of incisor inclination in patients with class III malocclusion treated with orthognathic surgery or orthodontic camouflage. Am J Orthod Dentofacial Orthop 2009; 135(2):146.e1–9. 2. Williams AC, Shah H, Sandy JR, et al. Patients’ motivations for treatment and their experiences of orthodontic preparation for orthognathic surgery. J Orthod 2005;32(3):191–202. 3. Sabri R. Orthodontic objectives in orthognathic surgery: state of the art today. World J Orthod 2006; 7(2):177–91. 4. Luther F, Morris DO, Hart C. Orthodontic preparation for orthognathic surgery: how long does it take and
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why? A retrospective study. Br J Oral Maxillofac Surg 2003;41(6):401–6. Choi JW, Lee JY, Yang SJ, et al. The reliability of a surgery-first orthognathic approach without presurgical orthodontic treatment for skeletal class III dentofacial deformity. Ann Plast Surg 2013. [Epub ahead of print]. Larson BE. The effects of presurgical incisor position of pogonion movement during mandibular advancement - a simple model. J Dent Res 1992;71:294 [abstract: 1507]. Proffit WR, Turvey TA, Phillips C. The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension. Head Face Med 2007;3:21. Kolokitha OE, Chatzistavrou E. Factors influencing the accuracy of cephalometric prediction of soft tissue profile changes following orthognathic surgery. J Maxillofac Oral Surg 2012; 11(1):82–90. Tucker S, Cevidanes LH, Styner M, et al. Comparison of actual surgical outcomes and 3-dimensional surgical simulations. J Oral Maxillofac Surg 2010; 68(10):2412–21.
KEY POINTS Orthodontic preparation is critical to the success of orthognathic surgery. Recognition and correction of existing dental compensations allows full correction of skeletal discrepancies. Presurgical orthodontic goals are important to define at the start of treatment and may not always include complete arch leveling or space closure, or ideal interdigitation. Orthodontic preparation dictates the skeletal movements that are possible at the time of surgery. Different malocclusion types have characteristic dental compensations that can be identified and described. Proper planning, monitoring, and communication between surgeon and orthodontist are critical to avoid potential pitfalls in the orthodontic preparation.
INTRODUCTION
PRESURGICAL GOALS
Proper orthodontic preparation is critical to the outcome of orthognathic surgical treatment (Box 1, Table 1). All orthodontic tooth movement should be planned before treatment, even if some movements are completed after the surgery. The ultimate goal is to create a situation in which the teeth are in proper position relative to their underlying skeletal bases.1 This goal creates a presurgical dental discrepancy that is at least as great as the skeletal discrepancy so that the occlusion acts as a guide for the surgeon to produce the optimal position of the skeletal parts during surgery. Because normal physiologic processes tend to compensate for the skeletal problem, significant tooth movement is generally needed to create the most esthetic and balanced outcome for the patient. Patients undergoing orthognathic treatment with orthodontic preparation should be well informed about the orthodontic procedures and what to expect from treatment and retention.2
There is no universal agreement among orthodontists and surgeons about the goals of orthodontic treatment before surgery. Some teams prefer nearly ideal interdigitation of presurgical plaster models before proceeding, whereas others are content to do the detailed finishing after surgery. In general, the guiding principle is that the teeth need to be moved sufficiently to allow the maxilla and mandible to be put in the desired position.3 If this general principle is used as a guide, it is possible to define certain parameters of presurgical goals.
Natural physiologic adaptation, or previous orthodontic treatment, often places teeth in a position that reduces the dental discrepancy compared with the skeletal difference. This adaptation, or compensation, needs to be removed before surgery. An example is the need to upright the lower
Disclosures: None. Division of Orthodontics, School of Dentistry, University of Minnesota, 6-320 Moos Tower, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA E-mail address: [email protected] Oral Maxillofacial Surg Clin N Am 26 (2014) 441–458 http://dx.doi.org/10.1016/j.coms.2014.08.002 1042-3699/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.
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Box 1 General concepts of orthodontic preparation for orthognathic surgery Three Concepts and a Corollary 1. Whenever possible, treatment should be planned so that the orthodontic and surgical relapse tendencies are in opposite directions. 2. Incisors should be positioned relative to their respective skeletal bases rather than external references. 3. Tooth movement is usually in the exact opposite direction for surgical versus nonsurgical treatment. Corollary: starting treatment without deciding whether to treat with or without surgery is generally a bad idea.
incisors in a class II patient in whom the incisors were initially proclined to minimize the overjet.
Alignment of Arches Gross crowding, spaces, or rotations are corrected.
Coordinate Arches If the maxilla and mandible are to be treated as single pieces, the shape and dimensions are made compatible so that they will occlude reasonably following surgery. If one or both jaws are to be treated segmentally, the individual segments should be arranged so that the arches will be compatible following the planned surgical movement of the segments. The general principle is that the teeth must not interfere with the planned skeletal movement, and they must be within reasonable distance for postsurgical orthodontic finishing. This principle means that not all orthodontic movement must be complete before surgery. For this reason it is also important to consider what the presurgical goals may not be.
Table 1 Goals of presurgical orthodontics (see text for complete description) Should Include
May Not Include
Decompensation of dentition Alignment of arches
Full closure of all spaces Perfect occlusion of surgical models Leveling of arches
Coordination of arches
Full Closure of All Spaces Some spacing may be desirable at the time of surgery to allow extra overjet to ensure canine seating (eg, distal to upper lateral incisors) or to allow room for postsurgical leveling without forward movement of the lower incisors. A small degree of spacing also creates flexibility during postsurgical finishing to create optimal occlusal relationships if the surgical outcome deviates from the plan.
Perfect Occlusion of Surgical Models Ideal occlusion may be the desired end result, but spending a great deal of time to achieve this perfection before surgery and then again after surgery may increase treatment time. It has been reported that the orthodontic preparation for surgery averages 17 months.4 In addition, some tooth movements can be accomplished most efficiently after surgery. For example, proclining lower incisors to decompensate a class III malocclusion can be faster and easier following surgery when soft tissue pressures are working with the desired tooth movement rather than against it.5
Leveling of Arches The decision whether to level the lower arch before or after surgery should be based on planning for the desired vertical change. Presurgical leveling allows mandibular advancement with minimal clockwise rotation of the mandibular, which helps promote horizontal movement and chin prominence. However, maintaining the curve of Spee requires the creation of a tripod occlusion on the incisors and molars at the time of surgery, which increases the vertical dimension and increases clockwise rotation. In some cases, this postsurgical leveling produces more desirable vertical changes and minimizes chin prominence, and trying to produce a perfect occlusion at the time of surgery prevents the optimal outcome. It is important to understand that the decision to level or not to level the lower arch before surgery has an important impact on the final chin position and lower face height (see Figs. 2 and 7).6
THREE CONCEPTS AND A COROLLARY FOR ORTHODONTIC PREPARATION Whenever Possible, Treatment Should Be Planned so that the Orthodontic and Surgical Relapse Tendencies Are in Opposite Directions The idea is to be well informed regarding possible posttreatment changes that will affect the stability of the final correction. When possible, it makes sense to plan orthodontic movements in a direction that causes any orthodontic change to be in
Orthodontic Preparation for Orthognathic Surgery the opposite direction to the expected surgical change. For example, if the maxilla is to be surgically expanded in a transverse direction, the surgical posttreatment tendency is to narrow slightly after treatment.7 Expanding the maxillary dentition orthodontically, either intentionally or inadvertently, has a relapse tendency in the same direction and therefore is additive to the surgical change. In contrast, if the arch is constricted orthodontically, the orthodontic relapse tends to expand the arch slightly. If this is combined with a surgical tendency to narrow, the resultant changes are offsetting rather than additive and greatly contribute to the stability. This same concept applies to the vertical position of incisors when preparing to surgically correct an anterior open bite. The preferred movement is to intrude the incisors further before surgery so that after treatment their tendency to slightly extrude offsets any skeletal tendency for recurrence of the open bite.
Incisors Should Be Positioned Relative to Their Respective Skeletal Bases Rather than External References Orthodontists are used to making judgments of dental position from cephalometric radiographs. Often the inclination of incisors is made to cranial base references (eg, Upper Incisor [U1]–SellaNasion [SN]) or other more distant landmarks (eg, U1–NA). Because these references may change as a result of the planned surgery, the outcome may not be what was envisioned if these distant references are used. This could happen if the upper incisor inclination was planned relative to the SN plane, but maxillary impaction is done with the posterior maxilla impacted more than the anterior. In this case, an ideal presurgical inclination relative to SN results in upper incisors that are more upright than desired after the differential impaction. Planning the incisor inclination relative to the palatal plane may be more appropriate because the palatal plane moves with the incisors during surgery.
Tooth Movement in Preparation for Surgery is Usually in the Opposite Direction to that for Nonsurgical Treatment In general, the lower incisors are proclined in class II patients because of the compensation described earlier. If the orthodontist treats a class II patient without surgery, the compensations are maintained, or even increased, during treatment. For a surgical treatment plan the lower incisors are retroclined to remove the compensation and to put them in ideal position relative to the skeletal base. This means incisor proclination for nonsurgical treatment versus retroclination for a surgical
plan. The same concept applies in the transverse plane and vertical plane for other problems. This observation that the direction of movement is opposite for surgical and nonsurgical solutions leads to the corollary. Starting treatment without deciding whether to treat with or without surgery is generally a bad idea.
TECHNIQUE/PROCEDURE The application of these concepts is shown by example in the most frequently encountered types of surgical setups.
Class II: High or Normal Mandibular Plane Angle Treated with Surgical Mandibular Advancement These patients are generally characterized by an increased mandibular plane angle, a retrusive mandible and chin, and lower face height that is normal or slightly increased. The most common dental compensations are proclined lower incisors and a slightly narrow maxillary dental arch caused by the maxillary teeth occluding with a narrower part of the mandible than ideal. Example: patient A.G. (Fig. 1). Problem list 1. Skeletal class II 2. High angle tendency 3. Severe chin deficiency 4. Upper and lower arch crowding 5. Dental compensations a. Mildly proclined lower incisors b. Increased lower arch curve of Spee Important considerations to prepare A.G. for mandibular advancement. Maintain upper incisor position: based on clinical assessment of incisor display at rest and at smile as well as cephalometric analysis and treatment simulation (Fig. 2). Maximize forward chin movement with surgery: requires pretreatment leveling to allow advancement along the occlusal plane without clockwise distal segment rotation (see comparison in Fig. 2). Resolve upper and lower crowding without change in upper incisor position, and maintain or upright lower incisor. Requires extraction of lower premolars. Treatment results and impact of orthodontic preparation The results of treatment of A.G. are shown in the photographs and in the cephalometric
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Fig. 1. Patient A.G. before treatment.
superimposition in Figs. 3 and 4. Proper planning and mechanics allowed resolution of the crowding without significant change in incisor inclination, which required premolar extraction in the lower arch to provide arch space and archform change in the maxilla with vertical upper incisor control. Pretreatment leveling of the lower arch resulted in the desired mandibular advancement along the occlusal plane without the distal segment rotation that would have increased the mandibular plane angle. A dramatic improvement in the facial profile was achieved by maximizing the forward chin expression and adding an additional genioplasty (Fig. 5).
Class II high angle: orthodontic preparation tips Determine upper incisor position (usually procline); vertical placement determined by smile arc Plan lower incisor target (usually uprighting to remove compensation); often requires lower premolar extraction to achieve incisor target Orthodontically level before surgery to maximize forward chin projection and minimize increase in lower face height (see Fig. 2)
Fig. 2. Difference between postsurgical leveling (A) and presurgical leveling (B) for patient A.G. Note the distinct difference in the movement of the chin (arrows) with the same amount of molar advancement.
Orthodontic Preparation for Orthognathic Surgery
Fig. 3. Treatment changes for patient A.G. Note the leveling of the lower arch by incisor intrusion and the resulting forward movement of the chin (genioplasty added). Also, the upper incisor position was largely unchanged as per the original treatment plan.
Class II: Low Mandibular Plane Angle Treated with Surgical Mandibular Advancement These patients are generally characterized by a decreased mandibular plane angle, a retrusive mandible with a well-developed chin, and a reduced lower face height. The mentolabial fold is often accentuated. The most common dental
compensations are a class II division 2 incisor appearance with the characteristic upright upper incisors and dental deep bite. Like other class II patients, they may have a slightly narrow maxillary dental arch caused by the maxillary teeth occluding with a narrower part of the mandibular arch.
Fig. 4. Final facial and intraoral views of patient A.G. The molar relationship is class III and canines are class I, which was the result of the removal of lower premolars to position the lower incisors properly.
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Fig. 5. Patient A.G. before (A) and after (B) treatment in profile view.
Example: patient R.P. (Fig. 6) Problem list 1. Class II division 2 dental relationship 2. Class II skeletal: mandibular deficiency 3. Slightly reduced lower face height: welldeveloped chin 4. Mild upper and lower crowding 5. Dental compensations a. Very upright upper incisors b. Increased lower curve of Spee 6. Previously extracted lower incisor
Fig. 6. Patient R.P. before treatment.
Important considerations to prepare R.P. for mandibular advancement: Procline upper incisor: based on clinical assessment of incisor display at rest and at smile as well as cephalometric analysis and treatment simulation. Direct chin forward and downward with surgery: requires posttreatment leveling to allow advancement with clockwise distal segment rotation (see comparison in Fig. 7).
Orthodontic Preparation for Orthognathic Surgery
Fig. 7. Difference between presurgical leveling (A) and postsurgical leveling (B) for patient R.P. Note the distinct difference in the movement of the chin (arrows) with the same amount of molar advancement. Postsurgical leveling provides better profile change by increasing lower face height and minimizing the chin advancement.
Resolve upper and lower crowding while providing the desired upper incisor position; maintain or upright lower incisor. Requires no extraction of premolars to meet target because lower incisor previously removed. Removal of third molars at the beginning of treatment to allow complete healing before surgery. Treatment results and impact of orthodontic preparation Fig. 8 top row shows the appearance of R.P. before surgery with very different upper and lower
occlusal planes because of planned postsurgical leveling. These divergent planes are managed during surgery with the planned distal segment and made possible by a surgical setup that provides a tripod contact only on incisors and molars. Postsurgical leveling happened rapidly because the lower arch was leveled into open space rather than against occlusal contact. The results of the treatment of R.P are shown at the bottom of Fig. 8 and in Fig. 9. The upper incisors were proclined into the desired position for smile esthetics and the surgical rotation decreased the mentolabial fold and avoided excess chin prominence.
Fig. 8. Patient R.P. before surgery (top) and after treatment (bottom). Note the divergent upper and lower occlusal planes before surgery, showing the intentional lack of leveling, and then the coincident occlusal planes after treatment when the lower arch is leveled to match the upper.
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Fig. 9. Patient R.P. before (A) and after (B) treatment in profile view. Note subtle improvement in profile from proper planning of mandibular advancement surgery.
Class II low angle: orthodontic preparation tips Determine upper incisor position: usually requires proclination; vertical placement determined by smile arc. Plan lower incisor target: often requires lower premolar extraction to provide lower incisor uprighting. Level after surgery to increase lower face height, open mentolabial fold, and reduce increase in chin projection (see Fig. 7).
Class III: Treated with Surgical Maxillary Advancement and/or Mandibular Setback Class III patients needing surgery present with some combination of maxillary deficiency and/or mandibular excess. The specific surgical procedures to correct the disharmony are selected by the surgeon, orthodontist, and patient based on facial esthetics, airway concerns, and dental arch widths (ie, if expansion is needed, a maxillary surgery is most desirable). The characteristic incisor compensations that must be removed are proclined upper incisors and retroclined lower incisors. There is often an element of transverse compensation with the maxillary posterior teeth buccally inclined and the mandibular teeth lingually inclined. It is important to recognize the compensations in all planes of space to properly plan treatment. Patients who present with a
component of mandibular excess also often have some degree of mandibular asymmetry. Assessment of dental and skeletal midlines by careful examination or cone beam computed tomography (CBCT) analysis is critical. Example: patient E.B. (Fig. 10) Problem list 1. Skeletal class III, maxillary deficient 2. High mandibular plane angle 3. Bilateral posterior crossbite 4. Upper and lower arch crowding 5. Dental compensations a. Mildly proclined upper incisors b. Retroclined lower incisors Important preparation:
considerations
for
orthodontic
Maintain or upright upper incisors: based on clinical assessment of E.B.’s smile, and cephalometric analysis. Procline lower incisors to decompensate and create space for alignment. Use class II elastics presurgically to help with decompensation. Create negative overjet equal to the underlying skeletal discrepancy to allow full surgical correction. Fig. 11 show the difference in skeletal change that occurs with adequate incisor decompensation. Removal of third molars at the beginning of treatment to allow complete healing before surgery.
Orthodontic Preparation for Orthognathic Surgery
Fig. 10. Patient E.B. before treatment.
Treatment results and impact of orthodontic preparation Photographs of the treatment finish show the esthetic improvement obtained with full correction of the skeletal position (Fig. 12). There was not a significant lower curve of Spee so the arches could be well coordinated before surgery. The upper incisors were maintained in their pretreatment inclination and the lower incisors proclined to decompensate. The vertical control of incisor position was important during orthodontic preparation to maximize smile esthetics and control the anterior face height.
Class III: orthodontic preparation tips Determine upper incisor position: usually retrocline and vertical placement determined by smile arc; may require premolar extractions to decompensate Plan lower incisor target: usually significant proclination is required to remove compensation; usually nonextraction to meet incisor target Must consider transverse: incomplete anteroposterior correction leads to relative transverse problem
Fig. 11. Difference between no incisor decompensation (A) and presurgical incisor decompensation (B) for patient E.B. The magnitude of surgical movement of the maxilla (arrows) is nearly 3 times with proper incisor decompensation. This decompensation allows full correction of the skeletal deformity (B).
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Fig. 12. Patient E.B. before (A) and after (B) treatment in profile view.
Vertical Maxillary Excess Treated with Surgical Maxillary Impaction Patients opting for surgery to correct skeletal vertical maxillary excess usually present with excessive incisor display at repose and excessive gingival display at full smile. The downward position of the maxilla results in downward and backward rotation of the mandible so that the lower face height is increased and the mandibular plane angle is also increased. The incisor compensation is variable and must be carefully assessed, but often the lower
incisor is proclined if the mandibular rotation has resulted in a class II condition. An anterior open bite may be present but is not always seen. Example: patient M.O. (Fig. 13) Problem list 1. Increasing gingival display on smile 2. Anterior dental open bite 3. Facial convexity with an increase in lower face height 4. Late vertical growth following previous orthodontic treatment
Fig. 13. Patient B.O. before treatment, showing increase in vertical maxillary excess from age 13 years and 6 months to 16 years and 2 months.
Orthodontic Preparation for Orthognathic Surgery 5. Dental compensations a. Mildly upright upper incisors b. Mildly proclined lower incisors Important preparation.
considerations
for
orthodontic
Plan desired final U1 position: consider active upper lip. a. Take care not to affect upper incisors too much because this can prematurely age the face Consider that a differential maxillary impaction will tend to upright upper incisors. With M.O., this uprighting is desired (Fig. 14). Differential maxillary impaction leads to mandibular autorotation. Depending on the reference landmarks, this rotation appears to upright the mandibular incisors.
Fig. 14. Surgical planning on patient B.O. showing uprighting of upper incisors, which occurs from impacting the maxilla more posteriorly than anteriorly. Also note the upward and forward autorotation of the mandible as a result of the surgical maxillary impaction.
Treatment results and impact of orthodontic preparation Photographs of the treatment finish in profile reveal the improved facial balance from the slight reduction in lower face height combined with an advancement genioplasty (Fig. 15). The gingival display at full smile is still 3 mm, but is age appropriate along with the 3-mm tooth to lip measurement at repose. The arches were well coordinate from previous orthodontic treatment.
Fig. 15. Patient B.O. before (A) and after (B) treatment in profile view.
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Vertical maxillary excess: orthodontic preparation tips Determine upper incisor position: may be no significant inclination change required; vertical placement determine by smile arc Autorotation of mandible brings chin up and forward Avoid extrusion of incisors in open bite situations: may require segmental surgery Genioplasty often desirable for lip balance and profile improvement
Maxillary Transverse Deficiency Treated with Surgical Expansion Skeletal maxillary transverse deficiency occurs most commonly in association with other skeletal problems rather than in isolation. This skeletal discrepancy is most easily viewed and measured in a frontal section of a CBCT volume image. The typical compensations, which are often overlooked without three-dimensional imaging, include buccal tipping of upper posterior teeth and lingual tipping of lower posterior teeth. If these teeth are not decompensated before surgery, transverse stability can be a problem. On occasion, this decompensation is difficult to fully achieve presurgically. In these cases, the surgical movement should overcorrect the dental relationship to allow
Fig. 16. Patient A.C. before treatment.
postsurgical decompensation. This plane of space may be the most important plane in which to ensure that orthodontic and surgical relapse tendencies are in the opposite direction because the stability of maxillary skeletal expansion is not as favorable as that of many other orthognathic procedures.7 Example: patient A.C. (Fig. 16) Problem list 1. Bilateral posterior crossbite 2. Skeletal maxillary transverse deficiency 3. Mild class III tendency 4. Nongrowing 5. Visible posterior attrition Important preparation:
considerations
for
orthodontic
Assess inclination of upper and lower posterior teeth (Fig. 17). a. In general avoid dental expansion in upper arch: may constrict Plan overcorrection of surgical expansion to plan for expected postsurgical change.
Treatment results and impact of orthodontic preparation Photographs of the treatment finish reveal little change in facial proportions or balance at repose. The vertical position of the upper incisor is unchanged, but the broader archform fills the buccal
Orthodontic Preparation for Orthognathic Surgery
Maxillary transverse deficiency: orthodontic preparation tips Seldom the only skeletal issue: consider anteroposterior relationships and their impact on the transverse plane. Class III correction generally improves the transverse relationship but class II correction may worsen. Decompensate: tip upper molars palatally before surgical expansion. Overcorrect surgically to accommodate expected postsurgical rebound.
COMMON PITFALLS IN PREPARING SURGICAL SETUPS
Fig. 17. Coronal slice of CBCT through the upper first molars of patient A.C. showing the skeletal transverse discrepancy and the resultant posterior crossbite.
corridors to provide improved smile esthetics (Fig. 18). The posterior crossbite has been resolved and the frontal intraoral view in Fig. 18 shows optimal molar torque as a result of properly planned orthodontic preparation.
Most problems, or pitfalls, encountered in the orthodontic preparation stage of an orthognathic treatment plan are caused by failure in one of 3 categories: (1) planning, (2) monitoring, or (3) communication. Common issues in each of these categories are listed in Box 2. Most of these pitfalls are preventable if they are thoughtfully considered before treatment and the orthodontist/surgeon team is committed to following the plan. Fig. 19 shows the surgical treatment of a young man with a class II malocclusion caused by mandibular deficiency. A treatment plan was
Fig. 18. Patient A.C. following 2-piece Le Fort I surgery to transversely expand the maxilla. Note the proper molar inclination that is only possible if the skeletal base is widened sufficiently to eliminate molar compensation. In addition, smile esthetics are improved by filling buccal corridors properly.
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Box 2 Tips to avoid common pitfalls related to planning, monitoring, and communication Planning 1. Agree on surgery timing (patient, surgeon, and orthodontist) a. Start now or plan for future? If future, define decision trigger? b. Start presurgical orthodontics based on desired surgery date. 2. Consider third molar removal a. Needed before surgery? If so, when? 3. Determine specific presurgical orthodontic target: need to know which way to go a. Upper incisor position b. Lower incisor position c. Transverse coordination d. If segmental cuts, is additional space to be provided? Monitoring 1. Growth monitoring a. Serial radiographs taken at planned interval: assign to orthodontist 2. Third molar removal a. If needed, who makes sure it is done? Assign to orthodontist or surgeon 3. Monitor presurgical orthodontic progress: assign to orthodontist a. Upper incisor position: assess clinically for vertical position, progress cephalogram b. Lower incisor position: progress cephalogram c. Transverse coordination: progress models 4. Segmental cut areas: assess clinically and/or with radiographs Communication 1. Everyone knows detailed plan at the start of treatment (patient, surgeon, and orthodontist) a. Agreed on at the beginning; avoid changes without good reason 2. Oral and maxillofacial surgeon included from the beginning a. Build team confidence with patient: prove communication 3. Inform each visit: progress relative to plan a. Review expected surgical timing b. Ask about changes in personal plans/schedule that may affect timing c. Schedule tentative surgical date early, then make it happen
selected that included mandibular advancement surgery. The simulated outcome was accomplished because of good monitoring and communication between orthodontist and surgeon. The pitfall was in the planning, in which the lower incisors were not decompensated as part of the orthodontic preparation. This omission resulted in a full dental correction to class I, but the chin was directed forward only marginally. Better planning
could have incorporated incisor decompensation into the orthodontic preparation and therefore directed the mandibular advancement further forward and less downward. Another common pitfall is shown in Fig. 20. In this situation, the plan (simulated result) included uprighting of the upper and lower incisors as part of the orthodontic preparation. Because of a failure in monitoring, the planned incisor position
Orthodontic Preparation for Orthognathic Surgery
Fig. 19. Common pitfall of planning. Lack of lower incisor decompensation and presurgical leveling before mandibular advancement surgery failed to maximize forward chin movement. The plan was achieved, but more thoughtful planning could have maximized the surgical result to not only correct occlusion but to maximize facial change.
was not achieved and the surgical result left more lip fullness than was envisioned. In this situation, the plan was well documented and the communication was good, but the monitoring of the preparation was lacking. Communication failure may be the most common pitfall in the orthognathic surgical process. Although it seems simple, it takes effort to make sure that the orthodontist, surgeon, and patient are always updated on the plan and the progress relative to the plan. A simple way to make sure that this occurs is to reinforce the plan and evaluate the progress at each presurgical orthodontic
visit. Any deviation from the expected progress should be communicated to the surgeon so that there are no surprises at the time of the expected surgery. A team focus on planning, monitoring, and communication can minimize most common pitfalls that occur in preparation for surgery.
TREATMENT SIMULATION Treatment simulation is not a new concept for planning orthodontic preparation for surgical procedures. In the past, the simulation was done
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Fig. 20. Common pitfall of monitoring. The original plan included significant incisor uprighting to reduce dental protrusion. This uprighting was not accomplished before surgery so although a good occlusal result was achieved the lip protrusion was not addressed as planned.
with acetate tracings and overlays on lateral cephalometric films. The top row of Fig. 21 shows the before and after lateral views as well as the acetate simulation that was used to plan orthodontics and surgery some years ago. This method works well, but is time consuming and requires experience and an artistic touch. More contemporary
cephalometric simulation (see Fig. 21D) uses digital tools to easily simulate growth, drag and drop teeth, and allow prediction of soft tissue movements. Soft tissue prediction, although useful for patient education, is challenging and there are many potential errors that could affect the usefulness of the prediction.8
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Fig. 21. Cephalometric surgical simulation, which is useful for planning orthodontic tooth movement in preparation for surgery. The top row shows a patient before treatment (A) and after treatment (B), as well as the handdrawn acetate prediction used to plan the orthodontic and surgical treatment (C). (D) A more contemporary cephalometric surgical prediction using digital software tools.
Cephalometric simulation Advantages Fast if done with contemporary software tools Includes tooth position, jaw position, and soft tissue Can link to profile photograph Disadvantages
More recently, advanced surgical simulation methods have become available that use threedimensional imaging and sophisticated modeling (Fig. 22). Indications are that surgical simulations using CBCT data may improve surgical predictability.9 These methods are reviewed elsewhere in this issue (see articles by Swennen, and Franco, Farrell and Tucker) and are likely to become the standard in the coming years.
Two-dimensional Does not provide direct tooth position information for archform Soft tissue prediction questionable, particularly lower lip
SUMMARY Proper orthodontic preparation is critical to the success of orthognathic surgical procedures. Understanding the dental compensations that tend to be
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Fig. 22. Three views of more sophisticated imaging and software simulation tools available for simulation of surgery and the orthodontic tooth movements needed to maximize the surgical result.
associated with certain malocclusion types helps to construct an appropriate treatment plan for each individual that maximizes the surgical benefit and stability. The use of a collaborative, team approach that includes proper planning, ongoing monitoring of progress, and communication between professionals and with the patient is critical.
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REFERENCES 1. Troy BA, Shanker S, Fields HW, et al. Comparison of incisor inclination in patients with class III malocclusion treated with orthognathic surgery or orthodontic camouflage. Am J Orthod Dentofacial Orthop 2009; 135(2):146.e1–9. 2. Williams AC, Shah H, Sandy JR, et al. Patients’ motivations for treatment and their experiences of orthodontic preparation for orthognathic surgery. J Orthod 2005;32(3):191–202. 3. Sabri R. Orthodontic objectives in orthognathic surgery: state of the art today. World J Orthod 2006; 7(2):177–91. 4. Luther F, Morris DO, Hart C. Orthodontic preparation for orthognathic surgery: how long does it take and
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why? A retrospective study. Br J Oral Maxillofac Surg 2003;41(6):401–6. Choi JW, Lee JY, Yang SJ, et al. The reliability of a surgery-first orthognathic approach without presurgical orthodontic treatment for skeletal class III dentofacial deformity. Ann Plast Surg 2013. [Epub ahead of print]. Larson BE. The effects of presurgical incisor position of pogonion movement during mandibular advancement - a simple model. J Dent Res 1992;71:294 [abstract: 1507]. Proffit WR, Turvey TA, Phillips C. The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension. Head Face Med 2007;3:21. Kolokitha OE, Chatzistavrou E. Factors influencing the accuracy of cephalometric prediction of soft tissue profile changes following orthognathic surgery. J Maxillofac Oral Surg 2012; 11(1):82–90. Tucker S, Cevidanes LH, Styner M, et al. Comparison of actual surgical outcomes and 3-dimensional surgical simulations. J Oral Maxillofac Surg 2010; 68(10):2412–21.
