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 Table of Contents  
CASE REPORT
Year : 2016  |  Volume : 7  |  Issue : 3  |  Page : 386-390  

Orthodontic-orthognathic interventions in orthognathic surgical cases: "Paper surgery" and "model surgery" concepts in surgical orthodontics


Department of Plastic, Reconstructive, and Aesthetic Surgery, KK Women's and Children's Hospital, 229899 Singapore, Singapore

Date of Web Publication17-Aug-2016

Correspondence Address:
Narayan H Gandedkar
Department of Plastic, Reconstructive, and Aesthetic Surgery, Cleft and Craniofacial Centre and Dental Service, KK Women's and Children's Hospital, 100 Bukit Timah Road, 229899 Singapore
Singapore
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-237X.188575

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   Abstract 

Thorough planning and execution is the key for successful treatment of dentofacial deformity involving surgical orthodontics. Presurgical planning (paper surgery and model surgery) are the most essential prerequisites of orthognathic surgery, and orthodontist is the one who carries out this procedure by evaluating diagnostic aids such as crucial clinical findings and radiographic assessments. However, literature pertaining to step-by-step orthognathic surgical guidelines is limited. Hence, this article makes an attempt to provide an insight and nuances involved in the planning and execution. The diagnostic information revealed from clinical findings and radiographic assessments is integrated in the "paper surgery" to establish "surgical-plan." Furthermore, the "paper surgery" is emulated in "model surgery" such that surgical bite-wafers are created, which aid surgeon to preview the final outcome and make surgical movements that are deemed essential for the desired skeletal and dental outcomes. Skeletal complexities are corrected by performing "paper surgery" and an occlusion is set up during "model surgery" for the fabrication of surgical bite-wafers. Further, orthodontics is carried out for the proper settling and finishing of occlusion. Article describes the nuances involved in the treatment of Class III skeletal deformity individuals treated with orthognathic surgical approach and illustrates orthodontic-orthognathic step-by-step procedures from "treatment planning" to "execution" for successful management of aforementioned dentofacial deformity.

Keywords: Model surgery, presurgical orthodontics, surgical wafers, surgical orthodontics


How to cite this article:
Gandedkar NH, Chng CK, Yeow VK. Orthodontic-orthognathic interventions in orthognathic surgical cases: "Paper surgery" and "model surgery" concepts in surgical orthodontics. Contemp Clin Dent 2016;7:386-90

How to cite this URL:
Gandedkar NH, Chng CK, Yeow VK. Orthodontic-orthognathic interventions in orthognathic surgical cases: "Paper surgery" and "model surgery" concepts in surgical orthodontics. Contemp Clin Dent [serial online] 2016 [cited 2020 Jan 27];7:386-90. Available from: http://www.contempclindent.org/text.asp?2016/7/3/386/188575


   Introduction Top


Surgical orthodontics is one of the most challenging fields in orthodontics which involves meticulous treatment planning and execution engaging a multidisciplinary team. In a multidisciplinary team, orthodontists play a vital role in patient evaluation, data collection (photographs, study models, and radiographs), and also, in performing the "paper surgery" and "model surgery," such that a "surgical wafer" is created which facilitate surgeon to emulate the plan. Presurgical planning (paper surgery and model surgery) is the most essential prerequisite of orthognathic surgery. The diagnostic information revealed from clinical findings and radiographic assessments is integrated in the "paper surgery" to establish a "surgical-plan." Further, the "paper surgery" is emulated in "model surgery" such that surgical bite-wafers are created, which aid the surgeon to preview the final outcome and make surgical movements that are deemed essential for the desired skeletal and dental outcomes. We describe a step-by-step procedure of "paper surgery" and "model surgery" technique for successful orthognathic surgery.

Our treatment plan is essentially a composite of clinical evaluation and cephalometric (both lateral and postero-antero cephalograph) assessment. A. M. Schwarz was one of the pioneers who used "facial profile" for the clinical assessment of face with little or no use of cephalographs. Schwarz's "Gnathic profile field (GPF)" is a simple yet efficient clinical appraisal of a patient's maxillofacial profile pattern by observing patient's in profile view. [1],[2],[3],[4] Moreover, "rule of thirds" is also applied for the evaluation and correction of face. "Rule of thirds" is face horizontally divided into thirds with lines drawn at hairline, eyebrows, and base of nose and chin [5],[6],[7],[8] [Figure 1]a and b.
Figure 1: (a and b) Showing gnathic profile field and "rule of thirds"

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Skeletal movements of orthognathic surgery are planned by analyzing certain soft tissues landmarks. Although Schwarz used these landmarks for photographic or clinical assessment, we have adapted them to lateral cephalogram for the planning of orthognathic surgery. Moreover, posteroanterior (PA) cephalographs are used to assess and plan orthognathic surgery for the correction of skeletal asymmetry.

GPF essentially involves certain landmarks which are enumerated below [Figure 1]a:

  • Nasion (Na): The junction of nasal and frontal bones at the most posterior point on the curvature of the bridge of the nose
  • Orbitale (Or): A point midway between the lowest point on the inferior margin of the two orbits
  • Pogonion (Pg): The most anterior point on the contour of the chin
  • Porion (Po): The midpoint of the upper contour of the external auditory canal (anatomic porion) or a point midway between the top of the image of the left and right ear-rods of the cephalostat (Machine Porion)
  • Subnasale (Sn): It is the transition point between the nose and the upper lip. It is the projection of hard tissue A point
  • Frankfort horizontal plane: A line connecting Po to Or
  • Orbitale vertical line
  • Nasion vertical line.
Orthognathic surgical planning by applying the principles of "paper surgery" and "model surgery" is described in the following case.


   Case Report Top


A 19-year-old female presented with chief complaints of forwardly placed lower front teeth and a large lower jaw. On examination, extraorally, she showed concave profile, increased lower anterior face height, mild hypoplastic maxilla, positive lip step, incompetent lips, hyperdivergent growth pattern, and chin deviation to the left side by 4 mm [Figure 2]a-d. Intraorally, she showed Class III molar and canine relation, severe crowding of upper and lower anterior teeth, reverse overjet of 2 mm, and occlusal canting with 3 mm upward movement of cant on the left side on smiling [Figure 3]a-e. Lateral cephalograph and orthopantomograph confirmed the clinical findings [Figure 4]a and b.
Figure 2: (a-d) Pretreatment extraoral photos

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Figure 3: (a-e) Pretreatment intraoral photos

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Figure 4: (a and b) Pretreatment lateral cephalograph and orthopantomograph images

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Treatment plan

From the clinical presentation and cephalometric evaluation, it was apparent that the mandible was excessively large and Class III deformity was a combination of prognathic mandible in both vertical and anteroposterior planes and a deficient maxilla. In addition, mandible deviated to 4 mm to left side. Surgical orthodontics was planned for the correction of largely deviated mandible and deficient maxilla.

Surgical treatment plan

The decision was made to commence presurgical orthodontic treatment with extraction of all first premolars such that severe crowding would be alleviated. Once the crowding is resolved, clinical measurements and cephalographs will be taken for surgical planning.

Treatment progress

All teeth were bonded with 0.022″ preadjusted brackets (Smartclip; , 3M Unitek, St Paul, MN, USA) and all teeth were ligated with 0.010 stainless steel ligature wire. 0.014″ Ni-Ti wires were placed in the upper and lower arches were placed as initial archwires, and subsequently, wires were changed to 0.016 × 0.022 Ni-Ti archwires and were reached to 0.017 × 0.025″ stainless steel. Once the crowding was alleviated, presurgical records were taken (clinical measurement, photographs, study models, and cephalographs) [Figure 5]a and b.
Figure 5: (a and b) Presurgical lateral cephalograph and orthopantomograph

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Clinical measurements

Measurements which are more relevant to assess the extent of asymmetries are taken into account, such as canine tip to eye canthus (right and left side), chin midline, incisor show (at rest and at smile), and dental midline. In the present case, the left canine tip to left canthus distance is shorter than the right canine tip to right canthus by 3 mm, chin is deviated to the left by 4 mm, incisor show at rest is 6 mm and at smile is 11 mm, upper midline is on, and lower midline is shifted to 4 mm to the left side.

Paper-surgery planning and execution

Lateral and PA cephalographs are traced with acetate matte paper. Maxilla and mandible templates are cut out from both lateral and PA cephalographs tracings using different colors in order to differentiate various movements [Figure 6] [Figure 7] [Figure 8].
Figure 6: (a) Surgical planning is done in both sagittal and vertical planes by placing maxilla template on the original tracing. In vertical plane, the maxilla is impacted for 3 mm and in sagittal plane, the maxilla is advanced for 3 mm both at autonomic nervous system and peripheral nervous system. Once the advancement and impaction is done, the maxillary template is fixed. (b) The mandible autorotates upward and forward due to maxillary impaction (big arrow). This autorotation has to be taken into account while setting back the mandible. The pivotal point for the autorotation of the mandible is at the glenoid fossa (small arrow)

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Figure 7: The mandible is set back for 6 mm such that mandible is within the gnathic profile field

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Figure 8: (a) The maxillary deviation in the vertical plane is corrected by pivoting the maxilla at the right canine tip such that the right side is moved upward and left side is moved downward. Once this movement is achieved, the maxillary template is fixed. (b) Mandibular template is adjusted such that mandibular deviation is corrected in the transverse plane

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Measurement planes and templates

Four measurement planes (three horizontal and one vertical) are drawn on the PA tracing and one maxillary plane on the lateral cephalometric tracing and templates are cut out. Planes such as greater wing-superior orbital (GWSO) plane, orbital plane, maxillary canine plane, maxillary plane (autonomic nervous system peripheral nervous system), and a vertical plane formed by the line passing through crista galli perpendicular to the GWSO plane [9],[10] were selected as reference planes. The vertical plane running from crista galli intersecting GWSO represents maxillary and mandibular asymmetry in the transverse dimension and ascertains the degree of mandibular and maxillary skeletal and dental midline shifts in relation to stable skeletal structure of the cranium. Orbital plane could also be used to ascertain the maxillomandibular complex's transverse asymmetry provided the orbital plane is symmetrical. Maxillary canine plane represents the vertical discrepancy of the maxilla while taking maxillary canine into account. The maxillary canine plane is to be applied with prudence as the canine tooth morphology may influence the maxillary canine plane. If the canine tooth has anatomical aberrancies, such aberrancy must be taken into consideration before using the maxillary canine plane. Furthermore, the maxillary plane is used to ascertain maxillary skeletal discrepancy in both sagittal and vertical plane using lateral cephalograph tracing. [9],[10]

Five templates essentially lay down the surgical planning in the sagittal and vertical plane. Surgical planning is further explained in [Figure 6] and [Figure 7]. Once the surgical plan is ascertained, maxilla and mandible models are mounted on the articulator, and models are moved according to the planned "paper surgery" such that surgical wafer is fabricated.


   Results Top


Posttreatment images and lateral cephalographs show the planned paper and model surgery is achieved, and also, show the fulfillment of "GPF" and "rule of thirds" [Figure 9] [Figure 10] [Figure 11] [Figure 12]. The treatment resulted in a symmetrical facial form with correction of largely deviated mandible and hypoplastic maxilla to a more orthognathic facial profile. The facial midline was in line with the dental midline with achievement of proper overjet and overbite.
Figure 9: Comparison of profile images of pretreatment, presurgical, paper surgery prediction, and postsurgery

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Figure 10: (a-e) Posttreatment intraoral photos

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Figure 11: (a-d) Posttreatment extraoral photos

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Figure 12: (a and b) Posttreatment lateral cephalograph and orthopantomograph images

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   Discussion Top


This paper describes the GPF and "rule of thirds" [Figure 1]a and b application in the planning of "paper and model surgery." "GPF" and "rule of thirds" provide a simple and practical method of clinical evaluation of the soft-tissues relationship. The surgical wafers produced using this method is precise and involves the orthodontist in every single step of wafer fabrication, such that the orthodontist can control all the variables. Although using three-dimensional (3D) virtual setup, some of the steps can be commuted from manual to computerized method, however, 3D has several shortcomings, such as:

  • 3D visualization and assessment is expensive in nature which invariably requires computed tomography (CT) scanned images which might add an additional financial burden [11]
  • Stereolithography for the wafer fabrication is a must [9],[10]
  • 3D internal reference system is unreliable as it is difficult to define and can be distorted by craniofacial deformity, and also lack normative data [9],[10]
  • Additional set of skills in 3D assessment and planning is required with expensive inventory [11],[12]
  • Soft-tissues evaluation is not possible as the soft tissues analog of CT images is unreliable due to the dearth of reference and normative data [9],[10]
  • Superimposition of scanned digital cast model on the CT image is cumbersome as artifacts incorporation may lead to misalignment [12],[13],[14]
  • Unclear reference landmarks on the 3D digital cast model during transfer of initial cast model from optical scanner might lead to inherent errors. [8],[9],[15],[16],[17],[18],[19]

   Conclusion Top


Paper and model surgery provides a simple and efficient way of assessing a dentofacial deformity with routinely available chair-side tools of evaluation. Through this case report, we have shown that careful evaluation of some specific landmarks and planes can lead to efficient planning and execution leading to the correction of complex dentofacial deformity.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

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Popat H, Richmond S, Drage NA. New developments in: Three-dimensional planning for orthognathic surgery. J Orthod 2010;37:62-71.  Back to cited text no. 11
    
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Mollemans W, Schutyser F, Nadjmi N, Maes F, Suetens P. Predicting soft tissue deformations for a maxillofacial surgery planning system: From computational strategies to a complete clinical validation. Med Image Anal 2007;11:282-301.  Back to cited text no. 12
    
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Sarver DM, Johnston MW, Matukas VJ. Video imaging for planning and counseling in orthognathic surgery. J Oral Maxillofac Surg 1988;46:939-45.  Back to cited text no. 13
    
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Harrell WE Jr., Hatcher DC, Bolt RL. In search of anatomic truth: 3-dimensional digital modeling and the future of orthodontics. Am J Orthod Dentofacial Orthop 2002;122:325-30.  Back to cited text no. 14
    
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Kaipatur N, Al-Thomali Y, Flores-Mir C. Accuracy of computer programs in predicting orthognathic surgery hard tissue response. J Oral Maxillofac Surg 2009;67:1628-39.  Back to cited text no. 15
    
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Rakosi T. Therapeutic diagnosis. In: Rakosi T, Graber TM, editors. Orthodontic and Dentofacial Orthopedic Treatment. New York: Thieme; 2010. p. 1-17.  Back to cited text no. 16
    
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Proffit WR. The soft tissue paradigm in orthodontic diagnosis and treatment planning: A new view for a new century. J Esthet Dent 2000;12:46-9.  Back to cited text no. 17
    
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van Vlijmen OJ, Maal T, Bergé SJ, Bronkhorst EM, Katsaros C, Kuijpers-Jagtman AM. A comparison between 2D and 3D cephalometry on CBCT scans of human skulls. Int J Oral Maxillofac Surg 2010;39:156-60.  Back to cited text no. 18
    
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Kragskov J, Bosch C, Gyldensted C, Sindet-Pedersen S. Comparison of the reliability of craniofacial anatomic landmarks based on cephalometric radiographs and three-dimensional CT scans. Cleft Palate Craniofac J 1997;34:111-6.  Back to cited text no. 19
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]



 

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