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Digitally Assisted Orthognathic Surgical Planning: Denition, History, andInnovation
https://t.me/medicina_free
Fig. 9 Digital 3D model
of the dental casts
usingCBCT scanner
Fig. 10 The 3D capture of
the dentition using an
intraoral scanner. These
images are obtained by the
TRIOS 3 scanner (3Shape,
Copenhagen, Denmark)
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Renne etal. (2017) found that the TRIOS 3 scanner (3Shape, Copenhagen, Denmark)
has the greatest overall scanning speed and accuracy among the intraoral optical
scanners reviewed [17].
4.1.3 3D Soft Tissue Data
Accurate representation of the 3D facial soft tissue is particularly important for
evaluation and treatment planning in orthognathic surgery (Fig. 6). The skin and
external soft tissue of the face can be captured usinga laser scanner orstereophotogrammetrycameras. These techniques record the surface of the facewithout harmful exposure of patients to radiation [18]. Only stereophotogrammetry allows
capturing the color and texture datasimultaneously (Fig.8). Triangulated facet laser
captured models without color or texture data are commonly exported in the
Standard Tessellation Language (.STL) le format, whereas stereophotogrammetry
data are saved as (.OBJ) le format. The 3D digital image of the facial soft tissue
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can then be integrated into the 3D virtual composite model of the CT/CBCT
scansincluding the accurate 3D dental image for prediction planning.
N. M. AlOtaibi and A. F. Ayoub
4.2 Three-Dimensional Model Acquisition
andVirtual Osteotomies
The creation of the 3D model in a virtual environment is achieved using rigid point
set registration algorithms (Fig.8).The superimposition and matchingof the related
sets of 3D images is usually achieved usingthe iterative closest point (ICP) matchingalgorithm, itmaps two sets of data together which includesCBCT, dentition, and
3D stereophotogrammetry image. The method is based on identifying a set of points
on each 3D image to achieve accurate superimposition of two sets of dataand minimize the surfacedifference in all three planes. This is known as rigid registration, the
procedureis followed by translational and rotational movements for the most accurate renement of the superimposition of the images (Fig.8). Several referencescould
be appliedto match correspondingimages, this includeslandmarks, ducial points,
surface models, voxel grey intensity, or combinations of these. Various validated
software packages are available for surgical simulation, allare based on the registration algorithms to build up the 3D virtual model for orthognathic planning.This
includes, the IPS CaseDesigner (KLS Martin, Tuttlingen, Germany), ProPlan CMF
(Materialise NV, Leuven, Belgium), Invivo6 (Anatomage, Santa Clara, CA, USA),
and 3dMDvultus (3dMD LLC, Atlanta, GA, USA).
Case 1
A 33-year-old female patient with right-sided hemimandibular elongation will be
used for the 3D virtual surgical planning demonstration (Fig.11). She was referred
to our multidisciplinary dentofacial planning clinic for correction of facial asymmetry. The surgery included maxillary Le Fort I osteotomy (correction of occlusal
cant, advancement, and rotation to the left) and bilateral sagittal split osteotomy
(BSSO) asymmetric setback.
4.3 3D Prediction
Before the virtual planning, the 3D virtual model should be positioned accurately
based on the clinical examination for correct orientation of the NHP, dental and
skeletal midlines, and any occlusal cant (Fig. 12). Virtual surgical planning
wasguided bythe clinical and radiographic assessment (Figs.12 and 14). The next
step in the VPS is the digitalosteotomies (Fig.13). The decision on the magnitude
of the needed correction of the maxilla-mandibular complex was based on the clinical diagnosis and radiographic analysis. A systematic approach wasconsidered,
which included the correction of maxillary midline (yaw), followed by adjusting the
occlusal canting (roll), nalising the anterior-posterior incisor movement of the
maxilla and the the vertical adjustment (pitch). The occlusal plane can be altered to
rene and assess the anterior facial height, nal chin position, and genioplasty if
Digitally Assisted Orthognathic Surgical Planning: Denition, History, andInnovation
https://t.me/medicina_free
a
179
b
Fig. 11 Case 1 a 33-year-old female patient, her main concern was the facial asymmetry due to
right-sided hemimandibular elongation. (a) Pretreatment facial photographs clearly showing the
mandibular asymmetry and the deviation of the chin to the leftside. (b) Pretreatment intraoral
photographs of herocclusion. The lower midline is shifted signicantly to the left as a result of the
mandibular asymmetry
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N. M. AlOtaibi and A. F. Ayoub
a
b
Fig. 12 Illustrationof the 3D VSP steps of the case 1. (a) Orientation ofthe CBCT to the natural
head position (NHP). (b) Hard tissue volumetric rendering of CBCT data (top row) and soft tissue
volumetric rendering of CBCT data (bottom row) both show the mandibular asymmetryand slight
deviation of the noseto the left
needed. The vertical and sagittal positions of maxillary incisors wererechecked
before nalising he prediction planning.
The mandibular osteotomy segment was rotated to the nal occlusion. The
mediolateral rotation of the mandibular osteotomy segment hascorrected the asymmetry (Fig.14). The evaluation of the position of theproximal segment was considered at this stage (Fig.15). The VSP allowed the evaluation of bony overlap and
interferences that may require localized bone removalduring surgery. The nal
Digitally Assisted Orthognathic Surgical Planning: Denition, History, andInnovation
https://t.me/medicina_free
Fig. 13 Virtual Le Fort I osteotomy of the maxilla and bilateral sagittal split osteotomy of the
mandible
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Fig. 14 The planned surgical correction of case 1 demonstrating the correction of facial asym-
metry of thesoft tissue of the face, the jaw bones,dental midlines and the maxillaryocclusal cant
assessment of the maxillomandibular complex in threedimensions was considered
before the simulation of soft tissuechanges. Soft tissue prediction is integrated into
various VSP packages19, 20. It predicts the soft tissue changes secondary to the
surgical movements, simulates the nalprediction (Figs.16 and 17)and facilitates
the printing of the occlusal split (Fig.18). Although soft tissue prediction remains
challenging, advances in technologies continuouslyimprove the accuracy of the
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N. M. AlOtaibi and A. F. Ayoub
Fig. 15 Three dimensional planning of the maxillo-mandibular complex to correct the maxillary
occlusalcanting and mandibular asymmetry. The VSP is sused to quantify the required surgical
movements and to identify bony interferences and their imapct on the position of the proximal
segment. The arrow shows a signicant mandibular yawto correct the asymmetry
prediction algorithms. Currently, soft tissue prediction provides a satisfactoryrepresentation of the postoperative changes(Figs. 19 and 20). The main advantage of
VSP is that it produces a photorealistic 3D image of the expectedsurgical outcomes
that facilitates communication between the orthognathic team and the patient. The
predictive accuracy of VSP has been evaluated in several studies. Our team studied
the accuracy of the 3Dplanning for correction of facial asymmetry, we reported
limitedprediction errors (Fig.21)within 1mm for linear measurements and 1° for
angular measurements [22–24].It is our routine practice to show thepatients the
prediction planning to take part in the deciosn-making process of the treatment
plan(Fig. 22).
Digitally Assisted Orthognathic Surgical Planning: Denition, History, andInnovation
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Fig. 16 The 3D soft tissue prediction planning. The top row shows the 3D virtual predicted
improvement of the maxilla oowing Le Fort I osteotomy. The bottom row shows the expected soft
tissue changes due to surgicalmaxillary advancement, the small arrow points towardthe paranasal
hollowing, which is corrected by the planned surgical movement
Case 2
A 25-year-old female patient was seen atthe dentofacial planning clinic for correction of skeletal class III relationship of the jaw bones due to mandibular prognathism and mild asymmetry. This case was planned for the surgery-rst
approachfollowed by postsurgical the orthodontic treatment. The planned surgical
intervention included setbackof the mandibleand correction of the asymmetry. The
case wasplanned using VSP for the prediction of the occlusal, mandibular and soft
tissue changes. (Figs.23, 24 and 25).
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N. M. AlOtaibi and A. F. Ayoub
Fig. 17 The preoperative submental vertex view of 3D VSP, left column shows the deviation of
the chin point (white arrow) off the skeletal midline (red line) and the atness of the left malar
region. The prediction (right column) shows correction of the chin point and malar atness according to the planned movement. The bottom row shows the superimposition of soft and hard tissueof
the face
Digitally Assisted Orthognathic Surgical Planning: Denition, History, andInnovation
https://t.me/medicina_free
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a
b
Fig. 18 Digital planning and printing of the intermediateocclusal guiding split (a) and the nal
splint (b)
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N. M. AlOtaibi and A. F. Ayoub
a
b
c
Fig. 19 The improvement of facial asymmetry as predicted (a), the preoperative (b)and immedi-
ate postoperative CBCT scans (c) showing the correction of occlusal canting and mandibular
asymmetry
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