3-D Cephalometric Planes 6

3-D Cephalometric Planes

Gwen R. J. Swennen

6.1 3-D Cephalometric Planes 230

6.2 Set-up of 3-D Cephalometric Planes 240 CHAPTER 6

CHAPTER 6

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6

Once virtual definition of the 3-D cephalometric hard and soft tissue landmarks has been accomplished, 3-D cephalometric planes can be automatically com- puted. 3-D cephalometric hard and soft tissue planes can be used for both qualitative and quantitative assess- ment of craniofacial morphology.

The 3-D virtual scene approach allows the genera- tion of several types of 3-D cephalometric planes that are automatically computed based on one or more 3-D cephalometric hard tissue (Chap. 4) or soft tissue (Chap. 5) landmarks, with regard to the virtual cephalograms or the 3-D cephalometric reference planes (Chap. 3):

▬A 3-D cephalometric plane computed from one 3-D cephalometric landmark is defined by a plane that passes one landmark and that is parallel to one of the 3-D cephalometric reference planes

▬A 3-D cephalometric plane computed from two 3-D cephalometric landmarks is defined by a plane that passes two landmarks and that is perpendicular to one of the 3-D cephalometric reference planes

▬A 3-D cephalometric plane computed from three 3-D cephalometric landmarks is defined by a plane that passes three landmarks (e.g. maxillary plane, mandibular plane, facial midplane)

▬A 3-D cephalometric plane computed from four 3-D cephalometric landmarks is defined by a plane that passes two landmarks and the mean of two other landmarks (e.g. Frankfort horizontal plane)

▬A 3-D cephalometric plane computed from more than four 3-D cephalometric landmarks is defined by a plane that passes the means of different pairs of landmarks (e.g. occlusal plane)

In this chapter important craniofacial 3-D cephalo- metric planes are described whose accuracy and relia- bility has been tested (Chap. 7). Other 3-D cephalomet- ric hard and soft tissue planes can easily be computed depending on the clinical or research purpose.

6.1

3-D Cephalometric Planes

Frankfort horizontal Plane: FH-Pl

Virtual Definition of the Frankfort horizontal Plane

The Frankfort horizontal plane is defined by a plane that passes both Orbita (Orbita_r and Orbita_l) land- marks and the mean of the two Porion (Porion_rand Porion_l) landmarks.

Fig. 6.1. Orbita_r,Orbita_land the mean of Porion_rand Porion_ldefine the Frank- fort horizontal plane (linked virtual lateral and frontal cephalograms, patient K.C.)

Figs. 6.2, 6.3. Orbita_r,Orbita_land the mean of Porion_rand Porion_ldefine the Frankfort horizontal plane [linked virtual lateral and frontal cephalograms to 3-D hard (6.2) and soft (6.3) tissue representations, patient K.C.]

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6.1 3-D Cephalometric Planes

Figs. 6.4, 6.5. Frankfort horizontal plane [linked virtual lateral cephalogram to 3-D hard (6.4) and soft (6.5) tissue representations, patient K.C.]

Fig. 6.6. Frankfort horizontal plane (3-D hard tissue representation, patient K.C.)

Fig. 6.7. Frankfort horizontal plane (3-D soft tissue representation, patient K.C.)

Maxillary Plane: Mx-Pl Virtual Definition of the Maxillary Plane

The maxillary plane is defined by a plane that passes the Anterior Nasal Spine and both Posterior Maxillary Point (PMP_r–PMP_l) landmarks.

Fig. 6.8. Anterior Nasal Spine and both Posterior Maxillary Point (PMP_r– PMP_l) landmarks define the maxillary plane (linked virtual lateral and frontal cephalo- grams, patient K.C.)

Figs. 6.9, 6.10. Anterior Nasal Spine and both Posterior Maxillary Point (PMP_r-PMP_l) landmarks define the maxillary plane [linked virtual lateral and frontal cephalograms to 3-D hard (6.9) and soft (6.10) tissue representations, patient K.C.]

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6.1 3-D Cephalometric Planes

Figs. 6.11, 6.12. Maxillary plane [linked virtual lateral cephalogram to 3-D hard (6.11) and soft (6.12) tissue representations, patient K.C.]

Fig. 6.13. Maxillary plane (3-D hard tissue representation, patient K.C.) Fig. 6.14. Maxillary plane (3-D soft tissue representation, patient K.C.)

Occlusal Plane: Occ-Pl Virtual Definition of the Occlusal Plane

The occlusal plane is defined by a plane that passes (1) the mean of Upper Incisor_r– Upper Incisor_land Lower Incisor_l – Lower Incisor_l landmarks, (2) the mean of Upper Molar Cusp_rand Lower Molar Cusp_rlandmarks and (3) the mean of Upper Molar Cusp_r and Lower Molar Cusp_rlandmarks.

Fig. 6.15. Tooth-related landmarks that define the occlusal plane (linked vir- tual lateral and frontal cephalograms, patient K.C.)

Figs. 6.16, 6.17. Tooth-related landmarks that define the occlusal plane [linked virtual lateral and frontal cephalograms to 3-D hard (6.16) and soft (6.17) tissue representations, patient K.C.]

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6.1 3-D Cephalometric Planes

Figs. 6.18, 6.19. Occlusal plane [linked virtual lateral cephalogram to 3-D hard (6.18) and soft (6.19) tissue representations, patient K.C.]

Fig. 6.20. Occlusal plane (3-D hard tissue representation, patient K.C.) Fig. 6.21. Occlusal plane (3-D soft tissue representation, patient K.C.)

Mandibular Plane: Md-Pl Virtual Definition of the Mandibular Plane

The mandibular plane is defined by a plane that passes the Menton and both Gonion (Go_r– Go_l) landmarks.

Fig. 6.22. Menton and both Gonion (Go_r – Go_l) landmarks define the mandibular plane (linked virtual lateral and frontal cephalograms, patient K.C.)

Figs. 6.23, 6.24. Menton and both Gonion (Go_r– Go_l) landmarks define the mandibular plane [linked virtual lateral and frontal cephalograms to 3-D hard (6.23) and soft (6.24) tissue representations, patient K.C.]

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6.1 3-D Cephalometric Planes

Figs. 6.25, 6.26. Mandibular plane [linked virtual lateral cephalogram to 3-D hard (6.25) and soft (6.26) tissue representations, patient K.C.]

Fig. 6.27. Mandibular plane (3-D hard tissue representation, patient K.C.) Fig. 6.28. Mandibular plane (3-D soft tissue representation, patient K.C.)

Facial Midplane Virtual Definition of the Facial Midplane

The facial midplane is defined by a plane that passes the Sella, Nasion and Menton landmarks.

Fig. 6.29. Sella, Nasion and Menton landmarks define the facial midplane (linked virtual lateral and frontal cephalograms, patient K.C.)

Figs. 6.30, 6.31. Sella, Nasion and Menton landmarks define the facial midplane [linked virtual lateral and frontal cephalograms to 3-D hard (6.30) and soft (6.31) tissue representations, patient K.C.]

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6.1 3-D Cephalometric Planes

Figs. 6.32, 6.33. Facial midplane [linked virtual lateral cephalogram to 3-D hard (6.32) and soft (6.33) tissue representations, patient K.C.]

Fig. 6.34. Facial midplane (3-D hard tissue representation, patient K.C.) Fig. 6.35. Facial midplane (3-D soft tissue representation, patient K.C.)

6.2

Set-up of 3-D Cephalometric Planes

Fig. 6.36. Set-up of 3-D cephalometric reference system in conjunction with the Frankfort horizontal plane, maxillary plane, occlusal plane and mandibular plane (3-D hard tissue and transparent soft tissue surface representation, patient K.C.)

Fig. 6.37. Set-up of 3-D cephalometric reference system in conjunction with the Frankfort horizontal plane, maxillary plane, occlusal plane and mandibular plane (3-D soft tissue representation, patient K.C.)