Computerized interactive orthodontic treatment planning Richard D. Faber, D.D.S., MS.,* Chartes J. Burstone, D.D.S., MS.,** and David J. Solon&e, Ph.D.*** Melville, N. Y., and Farmington, Corm.

C

omputer programsfor digital computersare now being used in orthodontics for cephalometricanalysisand for data-retrievalsystems.Cephalometricanalysis using a computer program is a relatively well-defined problem. The skeletal landmarksare converted into coordinatesin a geometric space and an analysis is chosen. A computer program can then be written to calculatethe desiredanglesand distances.If standardsare availablefor the analysis,then the resultscan be comparedto a table of standardsthat are already stored in the computer. Interventionby the clinician is not requiredonce the coordinatepoints are selectedand the data are entered into the program. This processresults in time saving to the busy clinician. It takes approximately30 to 60 secondsto digitize a lateral headfilm. The data retrieval systemsthat are currently in use are located in major teachingcenters and are used for rapid accessto large banks of growth and cephalometricdata. Record systems also fall into the retrieval systemarea, and someof theseare now availableas a serviceto the orthodontic clinician in practice via various entry modes. Computerizedpatient diagnosishas long beenworked at in medicine and is beginning to take strides in orthodontics. Computerizedprogramsfor diagnosisgo a step beyond a data-retrievalsystem, since they require the definition of meaningful criteria to establish conclusionsabout the stored data base. The treatmentplanning of an orthodontic patient must be precededby threedistinct steps:(1) records, suchas models, headfilms, etc., are obtained; (2) data are collected from theserecordsand directly from the patient; and (3) data and/or secondarilyderived data are comparedwith standardsto establisha differential diagnosisfor the patient. The computer program performs well in the storing of vast amounts of data and organizing them rapidly into predeterminedcategories.The drawing of conclusionsfor a differential diagnosis and treatment planning is a more sophisticatedproblem. At the presentstate of the art there has been only limited successin achieving thesegoals. It is fair to statethat although the computerprogram can greatly aid in amassingand organizing the diagnostic data baseinformation, it is still the clinician who must assimilateand soundly interpret the results. The field of computerized orthodontic treatment planning is at present one of the *Present address: 425 Broad Hollow Rd., Melville, N.Y.; Assistant Professor, Department of Children’s Dentistry, School of Dental Medicine, State University of New York at Stony B-k. **Professor aad Head, Department of Or&&unties, Scheol of Dental Medicine, University of Connecticut. ***Director, Bioengineering Laboratory, Department of Orthodontics, School of Dental Medicine, University of Connecticut.

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Computerized interactive treatment planning

37

INPUT PATIENT CLINICAL EXAM MODELS GROWTH INFORMATION DIGITIZED DATA

OUTPUT TREATMENT PLAN EcMENT

ORTHODONTIST Fig. 1. Interactive systems concept.

“vogue” areas.This step is unfortunatelya quantumjump both for computerprograms and orthodonticclinicians at the presentstateof the art. The treatment-planningprocess, although conceptuallydefined by many, is not defined to the detailed level requiredto allow a “machine” (computerprogram)to makeall the key decisions.The complexity of the problem becomesapparentwhen we begin to look at the multifactorial subjective variablesof clinical judgment, suchas facial esthetics,stability, and the weighting of the importanceof treatmentobjectives. The problem of computerizedtreatmentplanning itself suggeststhat an interactive approachshould be undertaken.Cyberneticsciencesuggeststhat, in casesof undefined functions in feedbackloops, operatorinterventionis a solution.15This allows the computer program to do the routine, readily definabletasks and yet allows the orthodontic clinician to make the key decisionsfor each step in establishinga logical treatmentplan for the patient. This approachrealistically utilizes the optimum performanceof both the computerand the clinician to a maximum. The term interactive systemimplies that a trained orthodontic clinician is an active figure in the feedback loop for each major treatmentdecision(Fig. 1). A graphicdisplay terminal is usedto allow the orthodontistto visualize the treatmentchangesthat are being planned for the patient. The configured systemis a real-time systemsimulation, sincethe clinician is actively conversingwith the computerprogramduring its execution. It is an important philosophicalpoint that the orthodonticclinician be included in the programsteps. This approachis unique in orthodontics,although for many yearsit has been usedin engineeringsystemdesignin areasof both industrial and scientific application for problemswith undefinedvariablesand functions. The purposeof this researchendeavoris to developan integratedsimulation system with the capability of planningorthodontictreatmentby meansof a computerizedinteractive graphicssystem.The systemhas beendevelopedto include the orthodonticclinician for makingkey decisionsand usingthe computerprogramto performthe routinetasksand calculations. Review of the literature

The literature related to the usesof digital computersin dental scienceis relatively small. A survey’of the presentusesof computersin dentistryshowedthat the applications

38

Faber, Burstone.

und Solonche

fall into four major categories: data-storage and retrieval systems, analytic systems, simulations, and real-time systems. There is almost no mention in the literature of the use of computer systems for interactive simulation programming to aid the researcher or clinician in orthodontic treatment planning for the patient. The major thrust of the computer applications to orthodontics has been in an area that is loosely termed computerized cephalometrics. This category of applications involves two areas. The first is the study of growth and development and growth prediction of the facial skeleton on both a longitudinal and a crosssectional basis to see if growth trends and patterns can be established. The second is the cephalometric anaylsis of patients who are to be treated orthodontically with comparison of measurements to available standards. The latter use has gained some prominence with its availability as a commercial service to practicing dentists and orthodontists.* Although the dental literature contains no direct references to interactive uses of computers in treatment planning, some of the reported work on simulations and analysis does help to support the basic concepts that are utilized in this project. The use of computer programs developed to do a cephalometric analysis has been reported by several investigators. 3-6 A lateral head plate tracing is converted into X-Y coordinate points, either by hand or by an electronic digitizer. A digitizer is a device that converts X-Y coordinate points on a graph to electronic signals that signify the numerical coordinate locations of these points in a geometric space. This is usually done by placing a pointing device at the location to be converted and transmitting this location to an electronic device that converts the physical location to an electrical analog and thus to an X-Y coordinate. These data are then fed into a digital computer. Once the data are stored in the computer in its X-Y coordinate form, any number of mathematical manipulations can be performed to measure the angles and distances between sets of points. If a data bank of standards is available,7-g then the measured data can be compared to the standards and, relative to the standard, “diagnostic” information is obtained. The concept of digitized information has been used in the study of dental arch form.‘O, I1 The arch form is digitized by inputting the cusp tip X-Y coordinate positions, and measurements of arch form and arch width are done automatically by a computer program. In the case of simulation,” if a curve for the arch form has been predetermined, then teeth can be moved along the curve and arch length or available space can be determined. The drawback to this type of simulation is that the mathematical general curve shape for the arch form that is fitted to the X-Y coordinates is either parabolic” or a trifocal ellipse, l2 which is an approximation to the arch form. To date, no major study has shown that the arch form for the human dentition actually approaches a mathematically defined curve in its entirety. An in-depth review of the literature revealed that no satisfactory model has been developed that includes as components the facial skeleton, dentition, and soft-tissue drape of the face. However, models for the individual component parts (lateral skull, soft tissue, arch form, frontal skull) have been reported on in the literature.‘0-‘3 The study of growth and growth prediction using the digital computer has been limited. The major thrust has been on skeletal patterns of lateral head films.gs 13,I4 These studies generally look at the changes of the lateral facial skeleton with age to get at the problem of growth prediction.16* I7 In general, it can be stated that the use of computers to analyze orthodontic data base

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Computerizedinteractive treatmentplanning 39

AND

KEYBOARD

I I DISC DRIVERS

I

PLOTTER

HARDCOPY

l PHONE

I

UN I T

Fig. 2. Systems configuration. The orthodontist’s communication link to the computer is via the blocks on the left of the illustration. The cephalometric data are entered via the digitizer. The orthodontist communicates with the system via the graphics terminal keyboard. Output is supplied via the plotter and hardcopy unit.

information is in a formative stageof development.The application of computersand graphicdisplaysfor orthodontictreatmentplanning is at presentunreportedin the literature, althoughthis approachhas been suggestedby Walker.‘, l3 The computer and its application The word computer has come to mean many different things to different people. Before embarkingon a discussionof computersystemsynthesis,it is important to understand the basic terminology. Digital computer systemsare usually composedof two parts-the hardwareand the software, to use commonjargon. The hardwareis the fixed unchangeablecomponentof the system. It is usually composedof the electronicequipment. The softwarecomponentof the systemis the programthat is written to perform the varioustasksinvolved in the solution of a particularproblem. The softwareis changeable to meet the particular needsof a user. A specializedhardwaresystemhas beensynthesizedto meet the specializedproblem

40

Faber, Burstone, and Solonche

Am. J. Onhod. .Junuan~ 197x

Fig. 3. Digitizing points for input to the computer program. Also illustrated is the point set used to construct the graphic display and calculations.

needsof interactive orthodontic treatmentplanning. The systemis illustrated in Fig. 2. The heart of the systemis a ComputerAutomation Alpha-16 m ini computerwith 24k of memory. The computer acts as the central processorfor the peripheralequipmentthat interfaceswith it, including the orthodontist. The major communicationdevice used by the operatoris a Tektronix 4010-1 graphic display terminal and keyboard. It is via this terminal that the operator commandsthe systemprogramoperation,interfaceswith the treatment-planningprogram, and is able to view the graphicsimulationthat is provided. The digitized dataareenteredinto the system via a Summagraphicstablet digitizer. The digitizer convertsthe x-y Cartesiancoordinates to electronicdata signalsand inputs the data directly into the computer. This is done by touching the pen-sensingdevice to the desiredlocation on the digitizer tablet as shown in Fig. 3. A HoustonInstrumentDigital Plotter is usedto obtain final hard copy actual-size(1: 1) tracingsof the treatmentplan. Copiesof the graphic terminal display can be obtainedby utilizing the Tektronix 4610 hard copy unit. Thesecopiesare approximatelythree-quarter scale(1:0.75). The data and programsare storedon a Diablo Series40 disk drive with a storagecapacityof 50,OOOK bits. The disk file systemis directly addressablefor programs and data. The entire systemis capableof communicationvia telephonemodemsto large databanksthat are storedon the University of ConnecticutUnivac 1106computersystem. The system is also capableof operation by remote operatorsvia a modem telephone system. The software that has been utilized in the system can actually be divided into two parts-the executive software and the treatment-planningsoftware. Since it is not the purposeof this article to discussthe specific technicaldetails of the executivesoftware, suffice it to say that the program is written in the BASIC computer languageand that

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Computerized interactive treatment planning

Number 1

:--

-

ESTABLISH GROWTH I

41

PREDICTION

OPERATOR- 1

Fig. 4. Outline of treatment planning steps and software.

TEK-10, the Tektronix graphic program, was used in part along with some system executive software that was supplied by the manufacturerof the computer. The treatment-planningsoftwarefor the interactive systemis outlined in Fig. 4, which shows an over-all flow chart of the major program steps. The details of each step will be describedin the discussionsection, with an example of a case. The presentstudy limits itself to treatmentplanning on a lateral head plate to obtain an estimateof lower incisor position. The lateral skull and soft tissue model that has been developedto do this is illustrated in Fig. 3. It consistsof forty-sevenpoints that are enteredas digitized data for the graphicsprogram. The model has beendevelopedto get a minimum numberof points and yet be useful and meaningful clinically. The Frankfort horizontal usedfor coordinate

42

Faber, Burstone. ‘t’tI”E K ”;Il

Am. J. &thud.

und Solonche 1’ OF

~~ttltltcTII:IIT

C’Et=‘rr’TIlEt4T i>F I‘IPTHOD~:~t~T II:‘:.

Junut1rv 197x HkHLTH !:EttTEF L.ATEPwL HEHL~PLHTE

1 FEctTMEt(T

F’LHtI

Fig. 5. Establishing a treatment occlusal plane. Data are inputted at 2.1 and 2.2 as noted by (7). Effect of change on A-B to occlusal plane is noted in new AB (OP).

referenceis a fixed plane that is offset from the S-N line by 7 degrees.The human engineeringaspectsof the program have been designedto make operationas simple as possible. The treatment pknning

program

Prior to going into a detailed description of the treatment planning program, it is important to set some philosophicalground rules. It is not the purposeof this article to substantiateor disproveany given assumptionsusedfor treatmentplanningbut, rather, to developa logical systemsengineeringapproachwhich is applicableto treatmentplanning in keeping with the specific needs of the individual patient. The mathematicsand geometryof the situationcan only describethe size, position, and angularrelationshipsof the parts in space.This can be done with a computerprogram,but the linal judgment and integration of the data still cannot be defined to the discrete levels required by the program, and thus thesedecisionshave been left for the trained orthodontic clinician to make. The program is designedto work with the clinician. It organizesand presentsthe primary databaseinformation in a meaningfulform. It calculatesand organizessecondary or derived data baseinformation. It alerts the operatorto the important criteria for each decisionand computesupdatesof the requiredmeasurements.The progmmthen displays and simulateswhat the operatordesireson the graphic display and recomputesthe effect of the changeon the relevant measurements. It is fundamentalto understandthat the computer with its program is an aid to the orthodontist and, as such, is only one facet of the completetreatment-planningprocess.

Volume 13 Number 1

Computerizedinteractive treatmentplanning 43 UNI’.FRSITY DEPMTMENT

OF CONNECTICUT HE(ILTl-4 CENTER OF ORTbWONTICS LFlTERQL HEfWPLATE

3 0 CMTA BfhSE TO ESTQBLISH

HWfWF

TREEATNENT PLAN

lOTATION ORIGINGIL

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UERTICClL CoNsIDERf4TIONS 13bWWlE.‘N-ME B >INTERLIWIAL WF C,INTERMXIUARY OR F AMXOfj BPROFILE

\ -5.6 -2.5

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RELATIVE TO NEW ImoP) (MN) Ebl N-a-PG (OK) N W PINS-ME/N-MEC % )

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IN Wl t? Ll

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CG+lPl.ETECYES=l~t@=S~

Fig. 6. Establishing mandibular rotation. Data are inputted in 3.1. Effect of change is noted as “new” AS (OP), N-A-PG, ANS-ME/N-ME.

The programmakesthe assumptionthat, prior to formulating a treatmentplan, the clinician has collected a completedata base(records,models, x-ray films, clinical examination) on the patient and formulateda list of the patient’s problemsthat requiretreatment. The treatment-planningsoftwarehasbeenwritten with modularizedpackagesfor each major step, so that as basicresearchin variousareasbecomesavailablethat is pertinentto a particular step it may be included in the program updateswith relative ease. The programsub-stepsthemselvesalso function as separatesoftwaremodules. The remainderof this discussionwill attemptto illustrate, via an exampleof a patie,nt with a Class II, Division 1 malocclusion, how the program aids the orthodontist in formulating a treatmentplan. Figs. 5 through7 are copiesof what the operatorseeson the Tektronix 4010-l display terminal. Prior to beginning the program, the orthodontist collects the data base. Using the lateral headfilm tracing, he marksthe appropriatelandmarksas shownin Fig. 3. He then startsthe programand entersthe data with the digitizer pen as shown in Fig. 3. Oncethe data are entered,the operatorcan correctany of the points he has enteredif an error has occurredin entry. The first stepof the programrequiresthe operatorto establisha growth prediction for his patient and input incrementalgrowth data. Much controversyhasarisenrecentlyabout growth prediction.16,l7 It is not the primary purposeof this programto forecastgrowth but, rather, that in stepsof the treatmentplan wheregrowth factorsarerelevantvariables, someestimatebe made. A simple schemehas beenchosento input the growth-prediction data. Using developmentalage of the patient, growth incrementsare selectedfrom tables of longitudinal values and fed to the program. The incrementaldata allow a three-part

44

Faber, Burstone, and Solonche UN1 k‘Et% I TY OF COtI(ECT I CUT HEKTH CENTER MFwRTMEttT OF @RTH@DONTICS LATERkl HEADPLATE TREATMENT FL&N 5 0 DQTF, &SE

TO EST%!LISH

w-P POSITIaj

OF LWER

5 1 OATA BASE TO ESTABLISti ICECIL PRCFILE~LIP A W O S E FORM MI SIZE PmasIuABIaL f+MiLE c FacIK CONVEXITY D~ERTICW HEIOFT FFK;E E)SEX fM@ ETHNIC CMRIXTERISTICS 5 2 ESTGl3LIStt IDEAL PROFILE

INCISOR

I

PROTRuSICN)

LL PROTRlJSION CHANGE m +:> 7+3 LL PROTRUSION Cl&GE M M +> NO=0 )

Rg. 7. Establishing ideal profile. Data for lip protrusion changes ammtemd in 5.2 and simulated. Step 5.3 allows for corrections of soft-tissue drape calculations if

growth construction.Cranial basegrowth is along the . M idfacial growth occurs as horizontal incrementsto A point and vertical inc 4 io ANS. The mandibular ‘Tj%einput schemeselected prediction is along the Y-axis angle to Frankfort horiz allows the input of any type of growth data that the operator&sires. The second step (2.0 as noted in Fig. 5) of the program requires the operator to establisha cant for the treatmentplane of occlusionas shown in Fig. 5. This decision is divided into two parts (2.1 and 2.2, as shown). Initially, the clinician determinesthe patient’snaturalplaneof occlusion,using databaseinformatiun. Once this hasbeendone, the clinician considersthe other factors that m ight enter into modification of the occlusal plane. Thesefactors are estheticconsiderations,periodontalconsiderations,and denture apical baserelationships.As illustrated in Fig. 5, the data base,along with the standards and measuredvalues, is displayedon the screen. As the operatormodifiesthe cant of occlusalplane, the new measurements are printed on the display. The simulationmovesthe occlusalplane as the operatorindicates,so that he can see what the changewill entail. In the samplecasedepictedin Fig. 5 the natural plane of occlusion was moved + 1 m m . Aatter than the inputted occlusal plane (center rotation is the mesiobuccalcusp of the maxiflary molar and changemeasuredin m illimeters at the maxillary incisor) (Step 2.1). After cons~mtiou of the modificationfactors, it was decidedto move the plane + 1 m m . flatter than the naturalplane as illustrated (Step 2.2). Once the treatmentocclusalplanehas beenselectedat the end of this step, it is used for all the calculation and simulation that follows. The third stepof the program(Step 3.0) is to establishmar&buIar rotation. Since the hinging of a mandibleopenor closedua li requires a growing patient, exeeptin casesto be treatedsurgically, growth is included in this step. As shown in Fig. 6, the data bases

Volume 13 Number 1

Computerizedinteractive treatmentplanning 45

are listed for the horizontal and vertical factors for a standard,the original, and growth. The tracing on the display showsthe original maxilla, the growth maxilla, and the growth mandible.In the exampleshownin Fig. 6 the mandibleis hingedclosed2 mm. (Step3. I), and the effects of this on the pertinent variablesare printed out as new data. The fourth stepof the programis to establishthe level of the treatmentocclusalplane, and it is not shown. This step requiresknowledge about the patient’s growth and the mandibularrotation from the previousstep. The data baseagain keys the clinician to the pertinent information from his data base,and the intermaxillary spaceafter rotation and growth is computed. The fifth step of the treatmentplan is to establishthe anteroposteriorposition of the lower incisor. This decisionhas beendivided into two substeps(5.2 and 5.4). First, the ideal profile is determined(Fig. 7), and then the factors to support that profile are evaluated.In Fig. 7 the data basefor the establishmentof a profile is seen.Many of these factors are subjectivebut are listed for completeness.The profile is selectedby inputting upper and lower lip protrusionchanges.An Sn-Pgline is included only for reference.In the example(Step 5.2) the upperlip was retracted2 mm. and the lower lip was protruded 3 mm. Oncethe profile is chosen,then inputs for the tissue-drapethicknessof the upperand lower lips can be updated. The secondpart of Step 5 is not illustrated. The data base includesa table of tissuethickness,standards,and the considerationsfor perioralfunction and stability. The programmakesa position estimateof the lower incisor basedon tissue drape, thickness,and overbite to supportthe desiredprofile. The stimulation then draws the new positions. At this point the operatoris given the option of overridingthe selected position on the basisof the presentedinformation and his clinical examinationdata. The sixth step of the treatmentplan not shown is to give a summaryof the treatment changesthat the orthodontisthas selectedfor the patient. Summary and conclusions

The developmentof a computerizedinteractivegraphicssystemfor organizingdata base information and doing orthodontic treatmentplanning has been presented.Since other investigatorshave looked at the requirementsof an orthodonticdata baseand the problem of diagnosis,it was thought that the problem of treatmentplanning would be a challenge.The systemwas developedwith the philosophythat the computercould be an aid to the orthodontistin organizingand displaying the information requiredfor a complete treatmentplan rather than a dictator of treatment, as others have proposed.The interactiveapproachof the orthodontistas a key figure in the feedbackdecisionloop in a real-time computersystemfor orthodontictreatmentplanning is a unique feature. The interactiveapproachto orthodontictreatmentplanning has resultedin: 1. A detailed definition of the treatment-planningproceduresrequired for implementationon a digital computer. 2. A definition of the interactivestepsand the order requiredto allow a trained orthodontistto obtain a useful treatmentplan. 3. A clinically useful two-dimensionalmathematicalmodel of the lateral skull and soft tissue. 4. A demonstrationof the feasibility of an interactive approachto orthodontic treatmentplanning. The advantagesthat are inherentin such a systemare:

46

Faber, Burstone,

and Solonck

1. 2. 3. 4. 5. 6. 7.

A more thorough data basethat is integratedwith the treatmentplan. A detailed treatmentplan that has included all stepsfor examination A graphic visualization of the projectedtreatmentchanges. A simulation that allows changesto be made easily. Control of the decisionsby the orthodontic clinician. Storageand retrieval of data as required for each step. A time savings to the busy clinician since, when he sits down to do the treatmentplan, the data are presentedin an orderly and organizedfashion. It may not be too far in the future that the cost and technical advancesin computer terminal technologywill put a computerterminal or computersystem in the realm of the private practitioner’s office. Certainly, the costshave come down considerablyin the past several years and will continue to do so as the usagerate increases.This will certainly increaseboth the demandand the feasibility of such a system. REFERENCES 1. Faber, R. D.: Computers in dentistry, unpublished data, University of Maryland, 1972. 2. Rocky Mountain Data Systems: RMDS computerized cephalometric manual, ed. 2, August, 1972. 3. Cleall, J. F., and Chebib, F.: Coordinate analysis applied to orthodontic studies, Angle Orthod. 41: 214-218, 1971. 4. Walker, G., and Kowalski, C. J.: Computer morphometrics in craniofacial biology, Comput. Biol. Med. 2: 235-249, 1972. 5. Solow, B.: Computers in cephalometric research, Comput. Biol. Med. 1: 41-49, 1972. 6. Krogman, W. M.: Use of computers in orthodontic analysis and diagnosis: A symposium, AM. J. ORTHOD. 61: 219-254,

1972.

7. Walker, G.: Cephalometrics and the computer, J. Dent. Res. 46: 1211, 1967. 8. Ricketts, R. M.: The evolution of diagnosis to computerized cephalometrics, AM. J. ORTHOD. 55: 795-803, 1969.

9. Solow, B.: Automatic processing of growth data, Angle Orthod. 39: 186-197, 1969. 10. Currier, J. H.: A computerized geometric analysis of human dental arch form, AM. J. ORTHOD. 56: 164-169,

1969.

11. Biggerstaff, R. H.: Computerized diagnostic setups and simulations, Angle Orthod. 40: 28-36, 1970. 12. Brader, A.: Dental arch form related with intraoral forces: PR = C, AM. J. ORTHOD. 61: 541-561, 1972. 13. Walker, G., and Kowalski, C. J.: A two dimensional coordinate model for the quantification, description, analysis, prediction, and simulation of craniofacial growth, Growth 35: 191-211, 197 1. 14. Savara, B. S.: Use of computer techniques in the study of growth, Adv. Oral Biol. 4: 1-9, 1970. 15. Parin, V. V., and Bayevskiy, R. M.: Introduction to medical cybernetics, National Aeronautics and Space Administration, NADS TT F-459, July, 1967. 16. Greenberg, L. Z., and Johnston, L. E.: Computerized prediction: The accuracy of a longrange forecast, AM. J. ORTHOD. 67: 243-252, 1975. 17. Shulohof, F. J., and Bagha, L.: A statistical evaluation of the Ricketts and Johnston growth forecasting methods, AM. J. ORTHOD. 67: 258-276, 1975. 425 Broad Hollow Rd., Melville, N.Y. I1746