Address for correspondence:

O. SorelCentre de soins dentaires2, place Pasteur35000 Rennes cedexsorelolivier@wanadoo.fr

DOI: 10.1051/odfen/2013207 J Dentofacial Anom Orthod 2013;16:307� RODF / EDP Sciences

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Determining the spatial positionof the maxilla:Using the Ditramax� system

Olivier SOREL

The symmetry of the construction planfor a human being goes way back to thevery beginning of the evolution of life onearth. Ontogeny reproduces to some ex-tent phylogeny. 500 Ma (million years ago)during the Cambrian Period, the chordate

nervous system appears most notably inStomochordates that gave rise to verte-brates. The notochord is a cartilaginousrod, located on the dorsal side, thatsupports and protects the neural tubeand that will evolve into the spinal column

Figure 1Bicephalic eagle of theEmperors of the Orientpainted on the ceiling of thevestibule of the LascarisPalace, an aristocratic dwell-ing in Nice dating from thefirst half of the XVIIe century.This representation is con-structed so as to maintainperfect axial symmetry thatthe two heads sublimelyepitomize.

Article available at http://www.jdao-journal.org or http://dx.doi.org/10.1051/odfen/2013207

in vertebrates. This cord determinesthe axes of symmetry: the cephalo-caudal axis, the dorso-ventral axisand the axis of right-left symmetry(fig. 1).

This symmetry is global and isexpressed almost perfectly in theregion of the cephalic extremity ofman. But trying to trace these axes ofsymmetry can turn out to be a verydelicate undertaking. The notion ofsymmetry is difficult to grasp becausethe landmark points are never per-fectly aligned and when examinedmeticulously, symmetry is a chimera.Dyssymmetry is the rule; our eye isaccustomed to accept these imperfec-tions that in no way detract from theappearance of the face.

In any therapeutic treatment planinvolving the use of prosthetic ororthodontic rehabilitation for cases of

‘‘normal’’ dyssymmetry, it is still ne-cessary to know how to assess it interms of diagnosis, etiology and prog-nosis. In adults, the head is fullyformed and diagnosis is usually suffi-cient. In children, in adolescents andcertain progressive forms in adults(condylar hypoplasia) it is of the ut-most importance to look for theetiology of the dyssymmetry in orderto make a prognosis about its evolu-tion, to take this into account whenplanning treatment and to adapt thistherapeutic response to the needs ofthe individual.

The clinical examination is the basisof any diagnostic approach (Fig. 2). Itprovides information from a perspec-tive that is accessible to everyone: thepractitioner, the patient and all con-cerned. This is when our treatmentchoices will have an impact on the

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Figure 2Facial photograph of a subject with normal dyssymmetry on which an axis was traced to divide the face into twohalves, (b) photographic montage of the right facial half with the same right half reversed and printed next to theoriginal right facial half and (c) the same montage made from the left facial halves. The appearance of these twohemifaces displays the differences in the scope of ‘‘normal’’ symmetry, note the differences at the levels of the ovalshape of the face, the mouth, and the nose. Without these montages, the differences would be imperceptible.

OLIVIER SOREL

2 Sorel O. Determining the spatial position of the maxilla: Using the Ditramax�system

daily lives of our patients. Certainly,because of this, a meticulous level ofobservation is so important.

Additional assessments will help usby providing less subjective data thatcomplete, refine and inform thosealready drawn from the clinical exam-ination and therefore allow us toexclude or to confirm our clinicalhypotheses. At this point, a diagnosiscan be established.

In this context, using the Ditramax�

System can be an additional aid inorthodontics for assessing the posi-tion of the maxillary arch within theface.

The problem presented by dyssym-metry resides in the difficulty inchoosing reference points. The devel-opers of the Ditramax� system chose

to anchor a bitefork on the maxillaryarch (retained by clenching with theopposing arch) with a metallic tail thatcomes out of the mouth and on whichslides a triple axis adjustable gimbal(wheels) that connects the bitefork tothe frame.

The frame is therefore put in placebased on the characteristics of thepatient. The ‘‘horizontal’’ plane isoriented along the axis of the bi-pupillary line, a plexiglass guide rulerslides vertically so as to allow foradjustments on the center of thepupils. The position of frame must beadjusted by tilting it around the axis ofthe bitefork so that the two pupilsalign with the guide ruler. The anchorscrew is then tightened (Fig. 3).

Next the frame is centered byadjusting the lateral anchor screwsuch that the median saggital planeis on the bi-pupillary line (Fig. 4).

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Figure 3After placing the bitefork in the mouth (held by thepatient by biting on it), the frame is secured andoriented based on the patient’s characteristics. The‘‘horizontal ‘‘ plane is oriented based on the axis of thebi-pupillary line by tilting the frame around the axis ofthe bitefork so that the two pupils line up with theguide ruler.

Figure 4The frame is centered either on the median saggitalplane or midway between the inter-pupillary length, byadjusting the side wheel.

DETERMINING THE SPATIAL POSITION OF THE MAXILLA: USING THE DITRAMAX� SYSTEM

J Dentofacial Anom Orthod 2013;16:307. 3

The last step consists in adjustingthe horizontal with the saggital plane:the reference point chosen is theplane of Camper, a plane that passesthrough the tragions and the sub-nasalpoint. In order to do this, it isnecessary to align the two stems ofCamper parallel to the plane of Cam-per by adjusting the gimbal with thewheel (Fig. 5).

The next step consists in transfer-ring the data onto the model.

Then the Camper stems are re-moved from the frame and a markerguide is added to it (three levels offixation are possible). The frame isinstalled on the mounting table bysliding it into the preset mortises. Themodel is placed on the bitefork andthe marks are made with a graphite

point stylus: laterally parallel to theCamper plane and anteriorly parallel tothe bi-pupillary line (Fig. 6). The verticalguide makes it possible to trace themedian saggital plane (Fig. 7).

Even though we fully understandthe benefits of these marks for man-ufacturing a prosthesis, they are alsovery useful in orthodontics wheredetermining treatment objectives re-mains the crucial factor.

In every case, Ditramax�2 providessimple and useful data that completethe clinical examination where it iseasy to make mistakes especially dueto parallax. On the other hand, incases of extreme dyssymmetry thataffects the entirety of cranio-facialstructures its usefulness is morelimited (Fig. 8).

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Figure 5Regulation of the horizontal alignment in the saggitalplane: the reference chosen is the plane of Camperpassing through the tragions and the subnasal point . Inorder to do this it is necessary to align the two stems ofCamper parallel to the plane of Camper by adjusting thegimbal using the wheel attached to the transverse axis.

Figure 6The stems of Camper are unscrewed from the frameand replaced by a marking guide (three levels of fixationare possible). The frame is put into place on themounting table to slide in the preset mortises.The model is set onto the bitefork and is scribed by agraphite stylus on the marking guide.

OLIVIER SOREL

4 Sorel O. Determining the spatial position of the maxilla: Using the Ditramax�system

The Ditramax� was designed byprosthetic technicians4,5. This tool isvery available and easy to use. Thesystem makes it possible to tracelines on the maxillary model thatsituates it in space in relationship tothe particularities of the patient’s face.This remedies the major defect of theAmerican size orthodontic models thatonly have dento-dental referencepoints (plane of occlusion and the lastlower molars). Planas had alreadyproposed a spatial orientation in orderto better take into account the dento-maxillo-facial architecture. The Ditra-max� is a method that connects these

three entities by adhering to classicorthodontic models.

We should keep in mind that assoon as we choose a point of view,we become dependent on it and thisview can bias our perception. Thecomprehensive investigation dis-cussed here generated by the clinicalexamination and completed by addi-tional assessments is the tried andtrue way for arriving at a diagnosis.

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Figure 7The vertical guide allows tracing of the median saggitalplane (1). The horizontal guide laterally allows tracing ofa line parallel to the plane of Camper (2) and anteriorly aline parallel to the bi-pupillary line (3). The divergencebetween the tracing and the base of the model clearlydelineates the usefulness in linking its orientation tothe anatomical landmarks of the face.

Figure 83D reconstruction from a scan of the face, frontal view.Image clearly visualizes the hypo-development of theleft half of the face as compared to the right half. Thisasymmetry affects the whole cranio-facial complex asshown in the asymmetry of the vault (orange arrow)and the inversion of the obliqueness of the ‘‘horizontal’’planes. In this particular case, the bi-pupillary landmarkseems to reach its limits by accentuating a plane thatcontributes to the asymmetry. Its high locationmagnifies the deviation of structures that are thefarthest from this line (chin, top of the skull shown bythe yellow arrows).

DETERMINING THE SPATIAL POSITION OF THE MAXILLA: USING THE DITRAMAX� SYSTEM

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REFERENCES

1. Margossian P, Laborde G, Koubi S, Couderc G, Maille G, Botti S, Dinardo Y, MarianiP. Communication des donnees esthetiques faciales au laboratoire de prothese :le systeme Ditramax�. Real Clin 2010;21:149-155.

2. Margossian P. Les references esthetiques et fonctionnelles en prothese fixee. Clinic2010 ; cahier 1, vol 31:633-684.

3. Margossian P, Laborde G, Koubi S, Couderc G, Mariani P. Use of the Ditramax systemto communicate esthetic specifications to the laboratory. Eur J Estht Dent 2011;6:188-196.

4. Margossian P, Koubi S, Maille G, Loyer E, Laborde G, Laurent M. La communicationcabinet/laboratoire cle du succes prothetique. L info Dentaire vol 94 n32-26 septembre2012.

5. Simonet P. Rehabilitation bimaxillaire par CFAO. 25 Cas complexes en ImplantologieStrategie Therapeutique 4, Espace ID.

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OLIVIER SOREL

6 Sorel O. Determining the spatial position of the maxilla: Using the Ditramax�system