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Computer assisted orthognath icsurg ica l trea tment p lann ing:a case report

John Eastman Grubb, DDS, MSDBecause there are a number of patients whohave significant skeletal disharmonies thatcannot be treated with conventional ortho-dontic therapy, forecasting surgical and orthodon-tic treatment objectives is becoming more impor-tant. Forecasts must be based on known soft tissuechanges that occur subsequent to dental and skel-etal repositioning.The use of manual template reconstructions de-veloped from headfilm radiographs and soft tissueestimates made from such recommendations istime-consuming and limited by human error. Com-puter assisted reconstructions allow the orthodon-tist to more efficiently and effectively perform thesetasks. Computerized treatment planning facilitatesthe storage, retrieval, modification and duplicationof cephalometric records for inter- and intraspecialtycommunication. Ithas also increased patient un-derstanding and acceptance of the recommendedtreatment procedures.In the first half of the 20th century, orthodonticdiagnosis was an exercise in classification. Patientswith similar patterns ofmalocclusion were groupedtogether based on the premise that dental andskeletal relationships were comparable. The devel-opment of the radiographic craniometer byBroadbent' allowed for the precise standardizationof anatomic landmarks and the study of growth anddevelopment of the skull. Subsequent introductionof cephalometric radiography created a method forthe description offacial disharmonies. A number ofdifferent cephalometric analyses have been devisedsince Boadbent's original work in 1934. Those that

have gained wide acceptance include Bjork.'Burstone,> Downs," Steiner,6,7,8Tweed.?" Riedel,"and Ricketts.l-" In addition, most orthodontic andoral and maxillofacial surgical postdoctoral pro-grams have borrowed portions of various analysesto develop cephalometric analyses of their own.Cephalometries has been used to assist in treat-ment planning for orthodontic and surgical care,and to quantify changes resulting from such treat-ment. The importance of accurately estimating fa-cial growth based upon facial pattern was the resultof the work of Ricketts who, in 1973,12,13tressed theimportance of predicting facial profile changes.Additional development of the concept by Bench,Hilgers and Cugino!' established a reasonablemethod of predicting facial change as a result ofgrowth, Incorporation of the ideal placement ofdental units in this growth-altered prediction trac-ing allowed for the construction of an orthodonticvisual treatment objective (VTO). The superimpo-sition of tracings enabled the orthodontist to designmechanics toachieve the treatment objective and itsresulting facial profile,By the late 1960s and early 1970s it became appar-ent that all skeletal disharmonies could not becorrected by orthodontic treatment alone. Duringthis time articles on orthognathic surgery increasedsignificantly, In 1972, McNeilPs was the first todescribe the use of surgical cephalometric predic-tion tracings, Others had previously describedtheir use in diagnosis and treatment planning, butMcNeill demonstrated the practical value of thetechnique, Robinson" attempted to quantify soft

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Grubb

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Figure 2Figure 1A-8Pretreatmentphotosat25 yr 5 mo. Note inad-equate paranasal andinfraorbitalcontoursaswell as lip incompe-tence.

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tissue change relative to skeletal movements incorrecting mandibular prognathism. By advocat-ing the use of acetate templates to move skeletalparts superimposed over the original cephalometrictracing, Fish and Epker" continued to refine thetechnique of soft tissue predictability.Bell, Profitt, and White" proposed the use ofcephalometric prediction using templates tocomplement model surgery changes, to predictchanges in bony relationships not seen on the dentalcasts, and to predict soft tissue changes.Wolford, Hilliard, and Dugan" expanded on thistopic to develop a systematic approach to predic-tion tracings. Their method combined the manipu-lation of hard tissue elements and the generation ofconsistent soft tissue predictions in a very simple,manageable format. This method is taught in manyorthodontic and oral and maxillofacial surgicalprograms today.Ricketts 13 and Walker" were among the first topublish their experiences using computers forcephalometric analysis. Their efforts were directed

The Angle Orthodontist Vol. 62 No.3 1992

Figure 2Pretreatment ceph-alometric tracingshows mandibularprognathisminrelationto SN.

at clarifying facial changes in the growing indi-vidual. Schendal, et. aJ.21 looked at soft tissuechanges of the orthognathic surgery patients andreported mean values based on data from digitizedpre and postoperative lateral headfilms. Bhatia andLowery" described an interactive on-line computeranalysis program that collected, stored, and ana-lyzed data from cephalometric radiographs. Theirprogram diagnosed dental and skeletal deformitiesand predicted posttreatment soft tissue profilechanges.Harradine and Birnie", and Walters and Walters"reviewed free-hand and photographic cutting tech-niques and compared them to computer-basedmethods of predicting the results of orthognathictreatment. They described a program that collectedand stored cephalometric data and used a graphicsplotter that would draw both existing and pre-dicted hard and soft tissue tracings.Hing" investigated the accuracy of a commer-cially available software program that includedprediction tracings. Although the program over-estimated anteroposterior changes and under-esti-mated vertical changes, the mean differences andstandard deviations tended to be less than thoseassociated with manually derived predictions.Video imaging represents a major addition to therole of computers in orthognathic surgery. Sarver,et. a126described his experiences with a video imag-ing system that permitted the manipulation of pho-tographic images to coincide with proposed hardtissue movement of orthodontic treatment and sur-gery. He noted favorable patient acceptance. Tho-mas, et. al." also noted the favorable response bypatients to video imaging. They reported that mostpatients felt that video imaging improved commu-nication between patient and surgeon, increasedpatient confidence in surgery, and enhanced thepatient-doctor relationship.A number of software programs are presentlyavailable that integrate cephalometric analysis andprediction with video imaging. The programspermit the cephalometric tracing and video imageto be altered in response to proposed orthodonticand surgical changes.The following case report incorporates the use ofcomputerized cephalometric analysis and interac-tive prediction using video imaging in the treat-ment planning and actual treatment of one patient..Treatment reportThis 25 year 5 month old woman presented witha chief complaint ofdissatisfaction with her appear-ance. Soft tissue assessment revealed a prominentchin point, inadequate paranasal and infraorbitalcontours, upturned nasal tip with sharp supra tipbreak, and lip incompetence. Intraoral tissues were

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Compute r a s sis te d p la nn in g

Figure 3 .A Figure 38

Figure 3Dhealthy with normal color and contour. She had aClass III dental and skeletal relationship. Generalphysical health was excellent and no unusual dis-abilities were reported or observed. Study castanalysis revealed a Class III dental relationshipwith the tendency for an anterior crossbite. Themandibular incisors were retroinclined. Initialintraoral radiographs were within normal limitsand revealed four partially impacted third molars.Tomograms were unremarkable with both con-dyles centered, no unusual osseous borders evi-dent, and adequate joint space.A computerized cephalometric analysis indicated

a prognathic mandible with Class III dental occlu-sion. Procumbent maxiliary incisors, the tendencyfor anterior crossbite, and mild vertical maxillaryhyperplasia were noted. Lower lip eversion andincreased lower anterior faceheightwere also noted.Treatment planningA computerized visual treatment objective was

derived and the following changes were made: 1)maxillary incisor torque was improved andprocumbency reduced; 2) mandibular incisorretroclination was eliminated; 3) the maxilla wasimpacted and advanced, moving superiorly morein the posterior then the anterior; and 4) the man-dible was set back and anterior vertical heightreduced.The process of computerized cephalometries is

quite direct. Demographic data is entered into thesystem by completing the general information datascreen. Next, the lateral cephalometric headfilm isplaced on an electronic, back lit grid called a digi-

Figure3C Figure 3A-EPretreatment studycastsFigure 4Cephalometric predic-tion tracing based onpredetermined treat-ment goals.

Figure 3E

Figure 4tizer. The digitizer isequipped with a stylus tha ttheoperator uses to trace the profile and skeletalanatomy and digitize preselected anatomic land-marks.The entry process can use verbal or graphic

prompts. Certain anatomic landmarks are alsolocated and digitized using the stylus.The points to digitize are circled in red on the

screen. The point's name, landmark location and X'-y values are displayed on the bottom of the screen.

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Figure SA Figure 58

Figure 6

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Anatomic areas are then traced or "streamed"using the stylus like a tracing pencil. These ana-tomic areas are prompted and outlined on thecomputer screen to assist the operator. By simplyfollowing the outline of the anatomic profile (on theactual x-ray) with the digitizing pen, the entry willbe completed. Study casts may also be digitized byfirst photocopying the occlusal view of each arch.Then, placing the photcopy on the digitizer, themesio-distal points ofeach tooth are digitized. Miss-ing or unerupted teeth are designated, and eachtooth appears on the screen. The individual toothmass is calculated or displayed. The entire arch isportrayed with the corresponding crowding andspacing. This interactive study feature essentiallycreates an occlusogram.After cephalometric and study cast data are en-tered into the system, a wide range of analyses andselected treatment options can be used and simu-lated. Electronic templates are created that simu-late anatomic structures. These templates includemaxillary and mandibular incisors and molars, the

The Angle Orthodontist Vol. 62 No.3 1992

Figure 5A-BPretreatment diagnos-tic set-up with removalof maxillary firstpremolars.Figure 6Superimposed pre-treatment (black) andprediction (blue) trac-ings. Note the impac-tion and rotation of themaxilla combined witha mandibular set-back.

maxilla and mandible, and the soft tissue profile.From the diagnostic set -up, pre-surgical orthodon-tic movement can be accomplished.Most skeletal problems have some form of dentalcompensation. Itisusually necessary to decompen-sate dental arches in anticipation of skeletal correc-tion. This results in the development ofa significantdental malocclusion that more closely resemblesthe skeletal discrepancies present, in preparationfor their surgical correction. Interactive use of thediagnostic set-up and surgical cephalometric pre-diction tracings is critical to effective orthognathicsurgical treatment planning.In this case, the diagnostic set-up was constructedafter considering the following criteria: 1) decom-pensate maxillary incisor procumbency and allevi-ate anterior crowding; 2)eliminate retroclination ofthe lower anterior segment; and 3) achieve properarch coordination.To accomplish these set-up goals, maxillary firstpremolars were removed. The maxillary incisorswere decompensated and crowding eliminated.The incisors were then retracted to an ideal intraarch relationship. The mandibular teeth werealigned and advanced with appropriate torqueadded to the anterior segment. Both arches werecoordinated. These changes resulted in a signifi-cant anterior crossbite that more closely resembledthe underlying skeletal discrepancy.A patient conference was held and the proposedtreatment plan and predictive records were pre-sented, including a computerized video image thatshowed the anticipated changes in facial appear-ance. The patient was advised that the informationprovided was no guarantee of actual outcome, butwas considered a reasonable expectation of treat-ment.Acti ve t rea tmentFollowing patient acceptance, treatment was ini-tiated. The maxillary first premolars and all thirdmolars were extracted. Necessary operative den-tistry was completed. The arches were banded andbonded and the teeth leveled and aligned. Based onthe diagnostic set-up and predictive visual treat-ment objective tracing, the maxillary anterior seg-ment was retracted aproximately 2 to 3 mm andde-torqued.Residual maxillary space was eliminated by slip-ping molar anchorage mesially, leaving a smallarea for the intended surgical cuts. The mandibularincisors were uprighted, aligned, and each arch wascoordinated relative to its respective skeletal base.The surgical phase oftreatment occurred approxi-mately 23 months following the initiation of activeorthodontic treatment. A Le Fort I osteotomy wasperformed to impact and move the maxilla anteri-

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orly. Bilateral sagittal split mandibular osteotomiespermitted the mandible to be moved posteriorlyand superiorly. Both jaws were stabilized usinginternal rigid fixation. Infraorbital rim implantswere placed to augment facial contours.Following surgery, the arches were coordinatedwith flexible nickel titanium edgewise wires toprevent any interferences that would hinder set-tling. Final stainless steel edgewise arch wires wereused to refine the occlusion, improve torque controland arch coordination. Settling was accomplishedwith light round wires and vertical elasticmechanics. Minor occlusal equilibration was ac-complished during these finishing stages.After 33 months of active orthodontic care, appli-ances were removed. Retention consisted of amaxillary .036 wraparound retainer worn full-timeand a direct bonded .0195 CAC braided 3-3 wireattached to each tooth. A light-activated directbonded method was used forease of placement andstrength of bonding.Posttreatment evaluationResults achieved include a Class I anterior occlu-sion and Class II molar relationship. Vertical andhorizontal overlap were within normal limits withexcellent anterior coupling. Midlines were coinci-dent and the anterior crossbite was eliminated.Radiographs revealed some root blunting of themaxillary left second premolar. Titanium platingand screw fixation were present in both jaws.Tomography revealed satisfactory condylar posi-tion and adquate joint space.Cephalometric assessment paralleled thepresurgical VTO with the maxilla impacted poste-riorly more than anteriorly (although not as muchas predicted) and brought forward. The mandiblewas moved posteriorly to articulate correctly withthe repositioned maxilla.Lip incompetence was decreased and the softtissue drape is within normal limits. Intraoralphotographs demonstrate a balanced occlusion anda normal overbite/overjet relationship.Crowding was eliminated as was the anteriorcrossbite. The midlines were coincident with eachother and the facial midline. A satisfactory softtissue profile with the elimination of lower lipeversion and incompetence was evident on thefacial photographs. A satisfactory "smile line" wasachieved as was an increased fullness of theparanasal and infraorbital areas.Superimposition of headfilms one year posttreat-ment shows excellent dental and skeletal stability.DiscussionPretreatment and presurgical prediction resultscan be achieved using manual tracings and acetate

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Compute r a ss is te d p la nn in gFigure 7Posttreatment pan-oramic radiographshows pteryqomaxu-lary fissure area withvascular clips used forhemostasis and mul-tiple boneplatesat therightmandibularangleregion to stabilize anunfavorable sagittalsplit.

Figure 8

Figure 98Figure 8Posttreatment cephalometric traclnq shows improved skeletal and softtissue balance.Figure 9A-BPosttreatment photos at 28 yr 4 mo. Note increased fullness in theparanasal area and improved lip competence.

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Figure 10A-EPosttreatment study casts.Figure 11Superimposed, computer-generated pre-treatment (blue) and posttreatment(black) cephalometric tracings.Figure 12Superimposed prediction (blue) and ac-tual posttreatment (black) tracings.

Figure 10B

Figure 10D

Fi'gure 10C

Figulre 10E

Figure 11 Figure 12template reconstructions. Computers offer an im-portant enhancement by providing informationrelevant to anticipated facial esthetic changes for avariety of surgical procedures quickly and accu-rately.Manual techniques, although reasonably accu-rate28 ,29 are understandably arduous, and time con-suming. Computerized cephalometric pretreatmentand preoperative prediction techniques are quicklyand easily prepared. With the widespread avail-

232 The Angle Orthodontist Vol. 62 No.3 1992

ability of computers and graphic spreadsheets,cephalometric data entry and access have beengreatly simplified. A number of orthodonticsurgical software programs currently on the mar-ket make it possible to: 1) accurately entercephalometric data; 2) simulate treatment; 3) pre-pare color VTOs of good quality in a fraction of thetime it takes to do these tasks manually; and 4)produce photographic images for patient review.(e.g. Prescription Planner, Orthognathic Treatment

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Comp ut er a ss is te d p la nn in g

Figure 13APlanner.)Presurgical orthodontic treatment of this case in-cluded decompensation of maxillary incisorprocumbency, elimination ofcrowding, an increasein the dental Class III discrepancy, selective spaceclosure and anchorage drain, and proper arch coor-dination. Because the diagnostic set-up occlusogramand the predictive head film are interactive, changesmade in tooth position, as in the diagnositc set-up,can be transferred to the predictive tracing on thelateral headfilm.Surgical movements included Le Fort I maxillaryimpaction and advancement. This was indicatedon the computer with selective electronic templatere-orientation. Mandibular auto-rotation and set-back osteotomy were shown by repositioning thecorresponding anatomic electronic template. Thesoft tissue changes that accompanied the dental andskeletal movements were automatically reflectedin the re-drawing of the profile based on knownnorms of soft tissue changes.Because of the computer's excellent storage ca-pacity, record retrieval is easily accomplished forany number of daily practice requirements.Rapid superimposition techniques before andduring treatment allow for improved planning andimplementation of mechanotherapy. Patient edu-cation is markedly enhanced with the system. To-day, more than ever before, itisimportant toprovidepatients with as much graphic data as possible sothat they can make intelligent, informed choicesbefore consenting to care.There are some important caveats to keep in mindwhen using an electronic system.It is unwise to assume that soft tissue forecastsachieved by any computer based system at thepresent time will be completely accurate. There-fore, it is prudent to advise the patient that the finalresult may not be exactly as forecast because of thevariables inherent in soft tissue reorganization fol-lowing surgery.Fortunately, orthodontic and maxillofacialsurgical researchers are making great strides indeveloping a more exact science. Although

Figure 138 Figure 13C

Equipment list for computerizedcephalometries and video imaging80486 computer:

5-112 floppy disk drive3-114 floppy disk drive205 Mb hard disk12 Mb RAM33 MHz clock speed17" multiscan color monitor (non-interlaced)

Color plotter printer (optional)Digitizer with stylusCablesLaser jet printerVideo capture boardVideo cablingBus mouseCamera - broadcast qualityThermal color printerAdditional software and supplies:floppy disks

power directorvirus protectionsoftwarecablingtransparency and computer paperprinter and plotter supplies

Optical disk storage, compression boards,and software will be needed aspatient filesexpand

computerization isan improvement on the manualtemplate techniques previously discussed, beautyand soft tissue interpretation isstill subjective. Therewill always be variations among clinicians.Although general anatomic parameters and estheticguidelines should be followed, the individualorthodontist's appreciation of art form will stillultimately determine the type of change that leadsto improved facial esthetics.

The Angle Orthodontist

Figure 13A-CA. Surgical treatmentobjective shows hardand soft tissue changeoverlay, with surgicacuts and magnitude ohard tissue correctionnecessary.B. Hard tissue tracingover initial photo, surgical treatment objective, and end of treatment photo.C.Comparisons of: initial soft tissue with hardtissue outline and overlay; surgical treatmentobjective tracing; andfinal soft tissue resulwith hard tissue outline and analysis overlay.

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GrubbAutho r AddressJohn Eastman Grubb, DDS345 F StreetSuite 250Chula Vista, CA 91910

J .E . G rubb is in p riva te p ra ctice in C hula Vista , C alif.H e IS D ir ecto r o f the o rtho gna thic s urgic al se ctio n o f theD epa r tm ent o f D eve lo pm enta l D entistry , U nive rs ity o fSouthe rn C alifo rnia Schoo l o f D entistry and a clinica lin str uc to r, G ra du ate O rth od on tic Depar tment , Univer -sity o f S ou the rn C a lifo rnia S cho ol o f D entis tr y.

References

AcknowledgmentsThanks to the orthognathic surgical team mem-

bers at the University of Southern California Schoolof Dentistry, Department of Graduate Orthodon-tics: Dr. Markell Kahn, Dr. Tim Smith and Dr. MelWishan. Special thanks to Dr. Kelly Cruser forconstant inspiration to publish this material.

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10. Tweed CH. The diagnostic triangle in control oftreatment objectives. Am J Orthod 1969;55:651.11. Riedel RA. Analysis of dentofacial relationships.Am J Orthod 1957;42-:103.12. Ricketts RM, Bench R ,. Hilgers J], et al. An overviewof computerized cephalometrics. Am J Orthod1972;61:1.

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