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226eversible hydrocolloid alginate has remained the mostmmon impression material used in the orthodontic of-e today with continued use of plaster, namely Type IIntal Stone, for fabrication of the casts.Recent technological breakthroughs have enhanced thecess of cast fabrication and manipulation. This processl requires traditional alginate impressions to be taken inorthodontic office. Instead of being poured by the orth-

ontist, impressions are shipped overnight to one of the

able to help the orthodontist classify malocclusions, identifyaberrations, and to formulate treatment objectives. As a staticrecord of dental classification, models are used to visualizethe morphology and position of the teeth in their respectivedental arches, as well as the degree to which the teeth aremalpositioned. In addition, diagnostic set-ups of treatmentoptions are accomplished by using sectioned models. In fact,study models appear to be the major record used for treat-ment planning. Han and coworkers2 showed that there waslittle difference between the treatment plan formulated byorthodontists using only study models when compared withusing models, photographs, panoramic and lateral cephalo-metric radiographs, and a cephalometric tracing. Orthodon-tic models document initial conditions, treatment progress,

m the Department of Orthodontics, University of Maryland, BaltimoreCollege of Dental Surgery, Department of Orthodontics, Baltimore, MD.ress correspondence to Stuart D. Josell, DMD, M Dent Sci, University ofMaryland, Baltimore College of Dental Surgery, Department of Orth-igital Models: An Introduatthew J. Peluso, Stuart D. Josell, Sam W. L

Dental study models are a cornerstone in theclassify malocclusion and formulate treatmenallowed the generation of digital dental mdimensionally on a computer. These new digiwith conventional plaster study models. Thisand the advantages of their use. OrthoCADthe technology used to generate these modeand available research.Semin Orthod 10:226-238 2004 Elsevier I

he procedures for taking dental impressions andforming study models have progressed since their in-

duction in the early 1700s. Philipp Pfaff first describedimpression-taking technique by using heated sealingx to obtain a negative representation of the dentalhes that was then used to pour a cast in Plaster of Paris.1

1839, Chapin A. Harris advocated using a calcinedster to fabricate casts from wax impressions.1 In thed-19th century, other materials such as Plaster of Paris,tta-percha, and thermoplastic modeling compound be-

e popular for taking impressions.1 Reversible hydro-lloid alginate and later irreversible hydrocolloid alginateolutionized impression taking in the early 1900s by

minating many of the inadequacies of the previouslyed materials. The new materials proved to be accurate,

ensionally stable, and easy to use, while maintainingst effectiveness. Later advances brought about evenanmo

odontics, 666 West Baltimore Street, Room 3-E-08, Baltimore, MD21201-1586.

1073-8746/04/$-see frontmatter 2004 Elsevier Inc. All rights reserved.doi:10.1053/j.sodo.2004.05.007ne, and Brian J. Lorei

entarium used by orthodontists to boths. Recent technological advances havethat can be saved and viewed three-dels solve many problems encounteredoverviews the advent of digital models

emodels will be compared relative toftware capabilities, additional services,

l rights reserved.

panies offering digital models. There, a traditional plas-model is fabricated and, using CAD-CAM technology, is

nsformed into a digital, three-dimensional (3-D) image ofdentition. Within a few days, an electronic file is available

be downloaded from the Internet to a desired computer.ce downloaded, software enables the digital models to bewed and manipulated.In 2003, The American Association of OrthodontistsAO) published a list of recommended basic orthodonticords in their Clinical Practice Guidelines for Orthodonticsd Dentofacial Orthopedics. According to the AAO, pre-atment and posttreatment records should include ex-oral and intraoral photographs, dental models, intraorald/or panoramic radiographs, and cephalometric radio-phs, as well as any additional indicated tests or proce-res. Thus, study models are an integral part of the orth-d the final treatment result. Orthodontists also use thesedels to present their treatment results to colleagues and

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Digital models 227tients for the purposes of education, evaluation, and re-rch.Study models are a reliable and popular form of diag-stic record3 (Table 1). Since they are a dimensionallyurate representation of the dentition, a number of mea-

rements and analyses such as tooth size-arch length dis-pancy and prediction of permanent tooth size can betained from plaster study models. Measurements ofth size-arch length discrepancies are recorded moreurately on the study model compared with intraorally,

minating the need to estimate the amount of crowding.ditional measurements include arch widths. Models areo mounted on articulators to visualize centric relation-tric occlusion discrepancies.

Although traditional plaster study models have been usedmany years, they have many limitations. For one, plasterdy models break. Continued use for measurements andplay can wear away plaster, decreasing accuracy and in-asing the likelihood of fracture. Storage is another conceptsenting both space and time problems. Models are usually

pt in boxes for easy retrieval while keeping them fromysical and chemical damage. A busy orthodontic officey start upward of 300 cases in 1 year, requiring an entirem for model storage. Time is an exacerbating factor asll. The shortest amount of time that records should be keptased on the applicable statute of limitations period duringich a malpractice suit may be filed.4 This period of timeies from state to state and ranges from 5 to 15 years. Thistute may start at the last day of treatment or may be de-ed until the patient reaches the age of maturity. Eithery, long-term storage is required. Three hundred cases perr for 10 years equal 6000 sets of pretreatment and post-atment models. This might necessitate an off-site storageility, increasing cost. Another problem is portability. Trav-ng with even a few sets of fragile study models is a difficultk. Communication is difficult when only one set of modelsst. The treating orthodontist might have to duplicate atients models, a process that is both costly and time con-

ing, to communicate with other dentists and specialists.Digital models alleviate many of the obstacles encounteredth using plaster models (Table 1). They are not subject toysical damage and do not create any dust or other mess.

le 1 Comparison of Plaster and Digital Models

st Less egnostic setups Laborarage space Largerage costs Costly

st and efficient retrieval Yestrieval at multiple locations Nobject to physical damage Yesnsfer of models Laboraegration with office management software Notient education Yesey also require negligible storage space. The digital infor-tion for each case can be stored on an office computers

comhard drive, on portable storage devices such as CDs, or on atral server. Digital information of a set of orthodonticdy models is less than 1 megabyte in size. The softwaregrams required to view these digital models are 8 to 12gabytes in size. A typical 700-megabyte CD-R, which costss than one dollar, holds over 700 cases. A 20-gigabyte hardve that costs around one hundred dollars can hold around,000 cases. Retrieval is fast and efficient because the mod-are stored by patient name and number. Another advan-e is that it is possible to view digital models at multipleations from any office computer linked to the practicestral server,5 allowing patients to be treated at multiples with easy access to their records. The electronic files inG format contain all of the model information of numer-

s views of the models and can be transferred electronicallycolleagues, specialists, and insurance companies. This de-ases the time and expense of model duplication and ship-nt.Digital models also minimize problems when purchasing actice. It is in the best interest of patients in active treat-nt that both the incoming and outgoing clinicians haveplete copies of the patients records. With digital models,

h orthodontist can have a copy for their archives withoutexpense of model duplication. In addition to all of these

vantages, digital models are also an excellent presentationl. From the first-year resident creating a case presentation,the experienced practitioner presenting cases to a studyb, digital models enable the projection of the model im-s for all in the audience to see without the concern of

mage.Digital models are also an excellent tool for patient educa-n. The younger generation of patients currently in treat-nt are familiar with computers and are comfortable withputer-generated images. They can relate to digital mod-

and probably expect to see this technology when they visitir orthodontists. Digital models can be shown to the pa-

nt and their guardians during treatment conferences, dur-treatment, and at the conclusion of treatment to illustrateimprovement in their dentition. There are also services

t will set up secure Web sites that contain patient recordsd treatment information so that the patient can view theseages from their home. Ultimately, digital models improve

ster Models Digital Models

ive More expensiverocedure Virtual on computerrequired Negligible

NegligibleYesYesNo

uplication and shipping Transfer of digital fileYesYestiomecomelsthetieingthethaanimmunication between the clinician and the patient, en-ncing informed consent.

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228 M.J. Peluso et al.As a result of these advantages and the advances in qualityd affordability of digital radiographic and photographichnology, many orthodontic offices have implemented

puterized practice management and imaging systems.e digital models available today offer seamless integrationo most of these management and imaging systems. Digitaldels are part of the totally digital orthodontic office.

There are three basic requirements needed to utilize digitaldels. A personal computer (PC) with Internet access is thest basic requirement.6 Internet access can be DSL, cable,dial-up. It is important to note that DSL and cable Internetess can provide a fast download time of the electronicormation from the company that produces the digitaldels. Once the equipment and internet access are set up, a

signated folder must be made in the computer for theoming digital information. Finally, a software program is

eded that allows the electronic information to be retrievedd generates the images of the digital models. This softwaresually provided free of charge by the company chosen toerate the digital models.

The two major computerized model systems creating dig-l models are OrthoCAD (Cadent, Inc, Fairview, NJ) andodels (GeoDigm, Corp, Chanhassen, MN) (Table 2). Art summary of each follows:

rthoCAD

le 2 Comparison of the OrthoCAD and emodels Service

O

st of basic file Less expee size Slightly ochnology used Proprietarftware charge Nonee for return of metal impression trays Nonester copies available for additional cost Yes

es saved on companys Web server 10 Yearsips plaster to lab for appliance fabrication Yesint-to-point measurements Yesrve-length measurements Yeslton analysis Yesnaka-Johnson analysis Yesoss-sectioning tool Yesualized occlusal contacts Yestual diagnostic setup (extra cost) Yesegration with office management software Dolphin,

Sirona,ImagingOrtho IIand Ort

ftware size 8 mbipping FedEx nexster models fabricated at a later date Possibleility to create digital models from preexistinglaster models

YesthoCAD was the first company to introduce a digitaldel service to the orthodontic market in early 1999. Or-

datioCAD is operated by Cadent, Inc, located in Fairview,. This company was started by two CAD/CAM engineerso consulted with doctors and other experts to developir 3-D system. The startup software for OrthoCAD ise of charge and is about 8 megabytes in size. There are novice contracts required to allow OrthoCAD to generateital models.A practitioner can get started with OrthoCAD, log ontow.orthocad.com or call 800-577-8767. The software can be

wnloaded directly from the Internet or the company can sendD at no charge. The cost of a set of digital models from

thoCAD is approximately the laboratory charge for a set ofmed study casts. At the request of the orthodontist, Orth-

AD will send postage-paid next-day shipping kits for ship-g impressions and a bite registration. Orthodontists coulder send disposable or metal trays. OrthoCAD recom-nds using specific disposable trays, alginate, and wax bites.When OrthoCAD receives the impressions and biteistration, the models are poured and scanned through aprietary process. The maxillary and mandibular digitalts are articulated by using the bite registration that wast with the impressions. Although a wax bite is said to beeptable, it is strongly recommended that a fast setting

lyvinylsiloxane be used for bite registration since itsuracy is critical especially when making measurementsinterarch relationships, digital images are fabricatedm the digital models using stereo lithography. Within 5

CAD emodels

than emodels More expensive than OrthoCAD0 kb About 800 kbnning process Nondestructive laser scanning

NoneYesYesIndefinitelyYesYesYesYesNoYesYesYes

ent, Walrus,ce Worksiews, Oasys,

ochart, Televox,ame

Dolphin, IMS, and Vistadent

12 mbshipping UPS next-day shippingee Possible for a fee

Yeswhthefreserdig

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regprocassenaccpoaccoffroys of receiving the impressions, the electronic informa-n is posted on the OrthoCAD server as an electronic

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Digital models 229. The file, which is typically 400 to 800 kilobytes forildren and a little larger for adults, is then downloadeda designated folder on the practitioners PC or server,her automatically or manually. OrthoCAD saves the

on their server for 10 years.Plaster copies of these models can be ordered at an addi-nal price and can be shipped to either the orthodontist ora laboratory of choice for appliance fabrication at the time

impression is submitted. OrthoCAD also offers a ser-e by which digital models can be generated from previ-sly trimmed plaster casts.OrthoCADs 3-D browser software allows the cliniciane simultaneous views of the models7 (Fig 1). This en-les the models to be viewed from multiple perspectivesthe same time. These views of the models can be rotatedenlarged to evaluate tooth position and make meas-ments in any plane of space. Bolton analyses,8 Tanaka-nson analysis, tooth width, curve-length, point-to-planeasurements, and any point-to-point measurements can be

rformed (Fig 2). OrthoCAD also features a cross-sec-ning tool that can slice the digital models in any vertical or

Figure 1 OrthoCAD five simultarizontal plane to check symmetry, overjet, overbite or toasure any location (Fig 3). The Jaws Alignment Tool

a pcoibe used to move the lower jaw in different directions,s enabling assessment of the occlusal contacts (Fig 4).

e Occlusogram feature is a visual multicolor represen-ion of these occlusal contacts that displays the distancetween opposing teeth. OrthoCADs Virtual Set-Up9 (Figenables the clinician to simulate and visualize any de-ed treatment option including virtual extractions, inter-ximal reduction, expansion leveling, and to apply var-s fixed appliances. The Virtual Set-Up service option

s an additional charge, which does not include the dig-l study models.A new innovation introduced by OrthoCAD is theircket Placement System. The clinician generates a digitaldel of the desired treatment objective by using the Virtual-Up software. Based on this model, the clinician thences each bracket in the desired position virtually on theital model (Fig 6). A bracket placement wand has a min-

ure video camera that transmits high resolution images ofintraoral environment and a removable sleeve that can be

rilized (Fig 7). The system determines the relative positionthe wand versus the actual tooth and gives the practitioner

views of the digital models.canthuThtatbe5)sirproiouhaita

BramoSetpladigiatthesteof

neousositioning target and signals when the virtual placementncides with the actual placement (Fig 8). A bracket is then

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230 M.J. Peluso et al.ked in place by using the wands internal curing light.us, bracket placement becomes more accurate and timecient. There are a number of bracket systems that aregrammed into the software to correspond to the size andpe of the actual brackets. This bracket placement service

o has an additional charge. The cost for this bracket place-

Figure 2 OrthoCAD measurement tool dFigure 3 OrthoCAD cross-sectioning tool demonstrating a vertioverbite.nt system must include a cart, CPU, flat panel monitor,raoral wand with tips, wireless connection, batteryckup, onsite training, and all travel expenses for theiner.The OrthoCAD digital models may be retrievedthin many practice management and imaging software

strating tooth width measurements.cal cutting of the digital models to check overjet and

proPraOrwitinpla

renstrOrchcu

the occ

Digital models 231grams. Currently Dolphin, Vistadent, Walrus, Sirona,cticeWorks Imaging, Dr. View, Oasys, Ortho II, IMS,thochart, Televox, and OrthoSesame are compatibleth the OrthoCAD software. As the products are con-ually enhanced and the company grows, OrthoCADns to continue to add additional services to their cur-

Figure 4 OrthoCAD Jaws Alignment Tool demonstratingdifferent directions.Figure 5 OrthoCAD Virtut suite of services. Those new services include con-uction of retainers with the final records either throughthoCAD or through the orthodontists laboratory ofoice. One of the new innovations that OrthoCAD isrrently testing is a centric occlusion-centric relationO-CR) feature in their software. OrthoCAD is work-

lusal contacts after moving the mandibular model in(Cal Set-Up tool.

ingwaIIIpauc

ememReha

e place

232 M.J. Peluso et al.with the American Board of Orthodontics (ABO) to-rd the acceptance of their digital models for the Phasecertification process. Cadent, OrthoCADs parent com-ny, has developed a Crown and Bridge fabrication prod-t that is currently in alpha testing.

Figure 6 OrthoCAD Bracket Placement demonstrating ththe digital model.Figure 7 OrthoCAD Bracket Placodelsodels by GeoDigm was founded in 1996 as Interactiveflective Imaging System. It has since changed its name ands grown considerably. emodels became available to the

ment of a bracket in the desired position virtually onement System wand.

Digital models 233Figure 8 OrthoCAD Bracket Placement System visual targeting indicator.Figure 9 emodels models can be moved, rotated, and enlarged.

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234 M.J. Peluso et al.fession at the American Association of OrthodontistsAO) National Meeting in 2001. To get started with emod-, one could either log onto www.geodigmcorp.com orl 866-436-6335. The software, which is about 12 mega-tes, is downloaded over the net or will be sent on CD at noarge. Geodigm will send postage-paid next-day shipping

Figure 10 emodels measurementFigure 11 emodels cross-sectioning tool used to slics for the impressions and a bite registration. The orthodon-could either send disposable trays or metal trays.

When the impression is received by GeoDigm, a plasterdel is fabricated. That plaster model is then scanned byng a nondestructive laser scanning process that digitallyps the geometry of the casts anatomy with an accuracy of

erforming a Bolton analyses.e the digital models overjet and overbite.

0disenThbada

by24tro

tio

visual

Digital models 235.1 mm.10 A laser strip is projected onto the cast and itstortion is read by multiple cameras while the cast is ori-ted on multiple axes to expose all surfaces for scanning.e maxillary and mandibular digital casts are articulatedsed on the wax bite sent with the impressions. Within 5ys, the electronic information, which is about 800 kilo-

Figure 12 emodels Color Bite Mapping feature that is aadjusted by the clinician.Figure 13 emodels articulation feature allows either a predetertes, is posted on the GeoDigm Web server and is accessiblehours a day. The company maintains a copy of the elec-nic file on its server.Download speeds depend on the type of Internet connec-n to the orthodontists computer. A dial-up modem wille 2 to 3 minutes to download, while a DSL or cable con-

representation of occlusal relationships that can betakmined or a custom center of rotation to be chosen.

nedodothaGedoap4 wera

236 M.J. Peluso et al.ction will take about 10 seconds. Referring dentists canwnload, at no charge, the digital model software. The ortho-ntist can then give the dentist the digital files for a patientt can be viewed on this software. For an additional fee,oDigm will send the plaster model directly to the ortho-ntist or to a laboratory of the orthodontists choice forpliance fabrication. The original plaster models are kept for

Figure 14 (A, B, and C) emodels eplan demonstraeeks before being discarded. Plaster models can be gen-ted after this time for an additional fee. GeoDigm also

(Ficaners a service by which digital models can be generatedm previously trimmed plaster casts.The emodels software allows the models to be moved,ated, or enlarged to evaluate tooth position and make mea-ements in any plane of space (Fig 9). Bolton analyses,th width, curve-length measurements, and any point-to-int or point-to-plane measurements can be performed

e simulation of an extraction treatment option.offfro

rotsurtoopo

ting thg. 10). emodels also feature a cross-sectioning tool thatslice the digital models in any vertical or horizontal plane

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Digital models 237check symmetry, overjet, and overbite and to help measurey location (Fig 11). There is a Color Bite Mapping featuret is a visual representation of occlusal relationships (Fig.). An articulation feature allows either a predetermined orstom center of rotation option (Fig. 13). This allows thenician to animate articulation and evaluate occlusal con-ts during jaw closing.Probably the most useful feature of the emodels softwarehe eplan (Fig 14 A, B, and C). This feature enables thenician to simulate any desired treatment option by using atual diagnostic setup. Once a desired setup is entered,re is an animation function that can be used to illustrate topatient how the teeth will move to correct the malocclu-

n. There are two different options that the clinician has tolize this virtual diagnostic setup technology. The first op-n is to have the teeth of the digital model sectioned so thatorthodontist can manipulate the position of each individ-

l tooth, simulating various treatment outcomes. The sec-d option is the eplan service. The orthodontist simplyscribes a treatment outcome and the tooth position is

termined by GeoDigm. Currently, Dolphin, IMS, and Vis-ent (GAC) are compatible with the GeoDigm software.

One of the newest innovations that is offered by GeoDigmsystem by which the orthodontist places brackets virtu-

y on the teeth of the digital models. An indirect bondingy is then fabricated and sent to the orthodontist. Thisovation allows more accurate bracket placement.oDigm also has Icon crowns, which utilize their core tech-

Figure 14logy (software and laser scanning) to digitize the crownduction process.

a dtioaluationiagnosis, treatment goals, and mechanics are to be made

sed on these digital models, they must be as accurate, if notre, than conventional plaster models. A few studies haveluated the accuracy of digital models. A study by Garino

d Garino11 showed that there was a reduction in the dis-rsion of the variance around the means when using thethoCAD software compared with a digital caliper on ane model. Measurements included tooth size and varioush dimensions. DeLong and coworkers,12 using the Virtualntal Patient System, compared standard measurementsm the actual object and from the stone model to the mea-ements obtained from a digitized model. The resultswed that the digital models were clinically acceptable.st recently, Santoro and coworkers13 showed a significantference between plaster and digital model measurementsth respect to both tooth width and overbite. While theital model measurements were consistently smaller thanplaster model measurements, the magnitude of these dif-

ences was so small that they were not considered to benically significant. There was no significant difference inerjet measurement.Ease of use is another consideration when evaluating dig-l model systems. This, however, is highly subjective. BoththoCAD and emodels software programs are self-ex-natory and do not require any special training sessions.wever, it takes some time to become familiar with theances of each program, such as rotating the models to view

ued)anpeOrstoarcDefrosurshoModifwidigthefercliov

itaOrplaHonuesired aspect of the models and manipulating the denti-n to perform a virtual diagnostic setup.

At this time both companies are in the process of develop-ing programs for scoring the American Board of Orthodon-tics (ABO) objective cast grading system, which is used toevaluate case finishing on the Phase III clinical examination.The ABO is currently monitoring development of these pro-grams and may in the future be able to accept digital modelsfor case presentations. Several university studies are inprogress to test the accuracy of these programs and to com-pare them to manual scoring of casts. Again, it must bestressed that the accuracy of the bite registration is of theutmost importance in evaluating interarch relationships suchas overbite, overjet, occlusal contacts, and so on, which mustbe measured to evaluate case finishing.

HIPPA regulations impact the management of all orth-odontic offices utilizing digital records. Patient informa-tion must be kept private. OrthoCAD and emodelsabide by HIPPA guidelines. Both use encryption softwareto transmit patient information and have a number offirewalls protecting their databases. An orthodontistshould not leave confidential patient information on thecomputer screen in plain view of others before, during, orafter treatment.

Digital models are an accurate, efficient, and easy-to-usealternative to plaster models. With the current technologyand future applications, digital models have the potential toadvance the practice of orthodontics. They allow precisemecomachan

clinician have positive impacts on treatment. Ultimately, thisprocess leads to higher quality of treatment and greater pa-tient satisfaction.

AcknowledgmentsSpecial thanks to Dr. Thomas J. Cangialosi, Meredith Hu-men, Chris Knor from OrthoCAD, and Sean OBrien fromemodels for all of their help.

References1. Glenner RA: Dental impressions. J Hist Dent 45:127-130, 19972. Han UK, Vig KW, Weintraub JA, et al: Consistency of orthodontic

treatment decisions relative to diagnostic records. Am J Orthod Dento-fac Orthop 100:212-219, 1991

3. Stewart MB: Dental models in 3D. Orthod Prod Feb:21-24, 20014. Russell M: Destroying patient records. California Association of Orth-

odontists Website 2002 (www.caortho.org)5. Redmond WR, Redmond WJ, Redmond JR: Ortho bytes Am J Orthod

Dentofac Orthop 117:240-241, 20006. Marcel TJ: Three-dimensional on-screen virtual models. Am J Orthod

Dentofac Orthop 119:666-668, 20017. Redmond WR: Digital models: a new diagnostic tool. J Clin Orthod

35:386-387, 20018. Sheridan JJ: The readers corner. J Clin Orthod 34:593-597, 20009. Garino F, Garino B: From digital casts to digital occlusal set-up: An

enhanced diagnostic tool. World J Orthod 4:162-166, 200310. Mah J: The cutting edge. J Clin Orthod 37:101-103, 200311. Garino F, Garino B: Comparison of dental arch measurements between

stone and digital casts. World J Orthod 3:250-254, 200212. DeLong R, Heinzen, Hodges, et al: Accuracy of a system for creating

13.

238 M.J. Peluso et al.asurements and visualization of proposed treatment out-es. The ability to quickly perform diagnostic setups, to

ieve ideal bracket placement from the onset of treatment,d to facilitate better communication between patient and3-D computer models of dental arches. J Dent Res 82:438-442, 2003Santoro M, Galkin S, Teredesai M, et al: Comparison of measurementsmade on digital and plaster models. Am J Orthod Dentofac Orthop124:101-105, 2003

Digital Models: An IntroductionOrthoCADemodelsEvaluationAcknowledgmentsReferences