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INTRODUCTION ď Ž
Successful treatment of the orthognathic surgical patient is dependent on careful diagnosis
ď Ž
Cephalometrics can be an aid in the diagnosis of skeletal and dental problems and a tool for simulating surgery and orthodontics by the use of acetate overlays (Tracing sheets). www.indiandentalacademy.com
HISTORY
Earlier Cephalometric analysis highlighting dentofacial patterns and dysplasias are
Wylie’s analysis (1947) Down’s analysis (1956) Steiner’s analysis However,
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Analysis to help diagnose and plan for orthognathic surgeries came in late seventies and early eighties.
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Cephalometrics for orthognathic surgery burstone 1978 april Journ. of oral surg
Quadrilateral analysis-
By Di-paolo AJO-DO
1984 Dec
Proportionate mesh analysis
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AJO 1987 JUN
More recent venture into Cephalometric treatment planning and predictions has been VIDEOIMAGING
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COGS – Cephalometrics for Orthognathic Surgery
Developed at university of Connecticut
Based on a system from Indiana University and further developed by additions at Connecticut
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COGS – Cephalometrics for Orthognathic Surgery
Developed by Charles Burstone et al
Presented first in Journal of Oral Surgery. 1978 April
Followed by Soft tissue Cephalometric Analysis for Orthognathic surgery in Journal of Oral Surgery. 1980 www.indiandentalacademy.com
Data derived from samples obtained from Child Research Centre, Univ. of Colorado school of medicine.
Sample type: Northern european descent
Sample Size = 27
16 females 11 males
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Plane of Reference for comparison ď Ž
A constructed plane called Horizontal Plane which is surrogate Frankfort Horizontal plane constructed by drawing a line 70 from SN plane
ď Ž
Most measurements will be made from projections either parallel or perpendicular to the Horizontal Plane www.indiandentalacademy.com
COGS Chosen landmarks and measurements can be altered by various surgical procedures. The appraisal includes all facial bones and a cranial base reference.
Rectilinear measurements can be readily transferred to a study cast for mock surgery. www.indiandentalacademy.com
ď ą Critical facial components can be examined. ď ą Standards and statistics are available for variations in age and sex from 5 to 20 ď ą Consists of a series of measurements that can be computerised.
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H-Plane
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Cranial Base
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Cranial Base Males
Females
Ar-Ptm ( || to HP)
37.1 + 2.8
32.8 + 1.9
Ptm-N ( || to HP)
52.8 + 4.1
50.9 + 3.0
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Horizontal Measurements
N-A-Pg www.indiandentalacademy.com
Horizontal Measurements Males
Females
N-A-Pg angle
3.9 + 6.4
2.6 + 5.1
N-A ( || to HP )
0.0 + 3.7
-2.0 + 3.7
N-B ( || to HP )
-5.3 + 6.7
-6.9 + 4.3
N-Pg ( || to HP)
-4.3 + 8.5
-6.5 + 5.1
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Vertical Measurements
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Vertical Measurements N-ANS ( 1 to HP) ANS-Gn ( 1 to HP) PNS-N ( 1 to HP) MP – HP angle Upper incisor-NF(1 to NF) Lower incisor-MP(1 to MP) Upper molar-NF (1 to NF) Lower molar-MP (1 to MP)
Males 54.7 + 3.2 68.6 + 3.8 53.9 + 1.7 23.0 + 5.9 30.5 + 2.1 45.0 + 2.1 26.2 + 2.0 35.8 + 2.6
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Females 50.0 + 2.4 61.3 + 3.3 50.6 + 2.2 24.2 + 5.0 27.5 + 1.7 40.8 + 1.8 23.3 + 1.3 32.1 + 1.9
Maxilla and Mandible
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Maxilla and Mandible Males
Females
PNS-ANS (|| to HP) Ar-Go (linear)
57.7 + 2.5
52.6 + 3.5
52.0 + 4.2
46.8 + 2.5
Go-Pg (linear)
83.7 + 4.6
74.3 + 5.8
B-Pg (|| to MP)
8.9 + 1.7
7.2 + 1.9
Ar-Go-Gn angle
119.1 + 6.5
122.0 + 6.9
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Dental Measurements
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Dental Males
Females
6.2 + 5.1
7.1 + 2.5
A-B ( 1 to OP)
-1.1 + 2.0
-0.4 + 2.5
Upper incisor – NF angle
111.0 + 4.7
112.5 + 5.3
Lower incisor – MP angle
95.9 + 5.2
95.9 + 5.7
OP upper – HP angle OP lower – HP angle
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The Arnett’s way
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Soft tissue Cephalometric Analysis ď Ž
By William Arnett and Robert Bergman AJODO 1999
ď Ž
Sequale to Facial keys to orthodontic diagnosis and treatment planning. Part I and II AJODO 1993 www.indiandentalacademy.com
“We only treat what we are educated to
see. The more we see, the better the treatment we render our patients�
-Arnett.... www.indiandentalacademy.com
Arnett and Bergman....... “When attention is directed only to bite correction, facial balance may not improve and can deteriorate. The orthodontist's job is to balance occlusal
correction,
temporomandibular
joint
function, periodonal health, stability, and facial balance while moving the teeth to correct the bite.�
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Format for examination of face
Natural head posture, Centric relation (uppermost condyle position), Relaxed lip posture True Vertical Line ( TVL )
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Arnett and Bergman
By examining the patient in this format, reliable obtained
facial-skeletal that
data
enhances
can
be
diagnosis,
treatment planning, treatment, and quality of results. www.indiandentalacademy.com
Why the Natural head position?
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Natural
head
posture
is
preferred
because of its demonstrated accuracy over intracranial landmarks.
Natural head posture has a 2째 standard deviation compared with a 4째 to 6째 standard deviation for the various intracranial landmarks in use.
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Why Centric Relation??
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Why relaxed lip position??
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ď Ž
The patient should be in the relaxed lip position because it demonstrates the soft tissue, relative to hard tissue, without muscular compensation for dentoskeletal abnormalities.
ď Ž
Vertical disharmony between lip lengths and skeletal height (vertical maxillary excess, vertical maxillary deficiency, mandibular protrusion, mandibular retrusion with deep bite) can not be assessed without the relaxed lip posture. www.indiandentalacademy.com
Existing positions and needed changes in upper incisor exposure, interlabial gap, lip length, and proportion are lost in the closed lip position.
Closed
lip
position
may
be
adequate
for
normoskeletal cases but is totally inadequate for skeletal disharmony assessment
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What is TVL and Why TVL??
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True Vertical Line ( TVL ) ď Ž
It is a Vertical line passing through the Subnasale with natural head posture.
ď Ž
It may be used to quantify favorable or unfavourable change in the profile after overjet reduction and has a potential role in post treatment analysis and research
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Soft tissue Cephalometric Analysis
Data base: Based on 46 white models
Males Females
= 20 = 26
All models had natural class I occlusion and reasonably well balanced facially
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Metallic Markers are placed on right side of face to mark key midface structures. i.e
1. 2. 3.
Orbital rim marker The alar base marker The subpupil marker
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Soft tissue Cephalometric Analysis Composed of five components 1. Dentoskeletal factors 2. Soft tissue structures 3. Facial length 4. Projections to TVL 5. Harmony values
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Dento skeletal factors
Have a large influence on the facial profile. When in normal range individually produce a balanced and harmonious nasal base, lip, soft tissue A’ and B’, and chin relationship.
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Dento skeletal Factors Females
Males
Mx occlusal plane
95.6 + 1.8
95.0 + 1.4
Mx1 to Mx occlusal plane
56.8 ± 2.5
57.8 ± 3.0
Md1 to Md occlusal plane
64.3 ± 3.2
64.0 ± 4.0
Overjet
3.2 ± .4
3.2 ± .6
Overbite
3.2 ± .7
3.2 ± .7
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Dento skeletal factors
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Soft tissue structures ď Ž
Soft tissue thickness in combination with dentoskeletal factors largely control lower facial esthetic balance.
ď Ž
Nasolabial angle and upper lip angle are important in assessing the upper lip and may be used by the orthodontist as part of the extraction decision. www.indiandentalacademy.com
Soft Tissue Structures Females
Males
Upper lip thickness Lower lip thickness PogonionPogonion’ Menton-Menton’
12.6 ± 1.8
14.8 ± 1.4
13.6 ± 1.4
15.1 ± 1.2
11.8 ± 1.5
13.5 ± 2.3
7.4 ± 1.6
8.8 ± 1.3
Nasolabial angle
103.5 ± 6.8
106.4 ± 7.7
Upper lip angle
12.1 ± 5.1
8.3 ± 5.4
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Soft tissue structures
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Facial length ď Ž
The presence and location of vertical abnormalities is indicated by assessing maxillary height, mandibular height, upper incisor exposure and overbite.
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Facial Length Nasion’-Menton’ Upper lip length Interlabial gap Lower lip length Lower 1/3 of face Overbite Mx1 exposure Maxillary height Mandibular height
Females 124.6 ± 4.7 21.0 ± 1.9 3.3 ± 1.3 46.9 ± 2.3 71.1 ± 3.5
Males 137.7 ± 6.5 24.4 ± 2.5 2.4 ± 1.1 54.3 ± 2.4 81.1 ± 4.7
3.2 ± .7 4.7 ± 1.6 25.7 ± 2.1 48.6 ± 2.4
3.2 ± .7 3.9 ± 1.2 28.4 ± 3.2 56.0 ± 3.0
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Facial Length
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Projections to TVL
They are antero-posterior measurements of soft tissue and represent the sum of the dentoskeletal position plus the soft tissue thickness overlying that hard tissue landmark. The horizontal distance for each individual landmark, measured perpendicular to the TVL, is termed the landmark’s absolute value.
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Projections to TVL Females
Males
Glabella
–8.5 ± 2.4
–8.0 ± 2.5
Orbital rims
–18.7 ± 2.0
–22.4 ± 2.7
Cheek bone
–20.6 ± 2.4
–25.2 ± 4.0
Subpupil
–14.8 ± 2.1
–18.4 ± 1.9
Alar base
–12.9 ± 1.1
–15.0 ± 1.7
Nasal projection Subnasale
16.0 ± 1.4
17.4 ± 1.7
0
0
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Projections to TVL
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Projections to TVL A point’ Upper lip anterior Mx1 Md1 Lower lip anterior B point’ Pogonion’
Females –0.1 ± 1.0 3.7 ± 1.2
Males –0.3 ± 1.0 3.3 ± 1.7
–9.2 ± 2.2 –12.4 ± 2.2 1.9 ± 1.4
–12.1 ± 1.8 –15.4 ± 1.9 1.0 ± 2.2
–5.3 ± 1.5 –2.6 ± 1. 9
–7.1 ± 1.6 –3.5 ± 1.8
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Harmony Values ď Ž
Created to measure facial structure balance and harmony.
ď Ž
It is the position of each landmark relative to other landmarks that determines the facial balance.
ď Ž
The harmony values represent the horizontal distance between two landmarks measured perpendicular to the true vertical www.indiandentalacademy.com
HV examines four areas of balance
Intramandibular parts. Interjaw Orbits to jaws The total face
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Intramandibular Relations These values assess chin projection relative to other mandibular structures.
Females
Males
Md1-Pogonion’
9.8 ± 2.6
11.9 ± 2.8
Lower lip anteriorPogonion’ B point’-Pogonion’
4.5 ± 2.1
4.4 ± 2.5
2.7 ± 1.1
3.6 ± 1.3
Throat length (neck throat point to Pog’)
58.2 ± 5.9
61.4 ± 7.4
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Harmony Values
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Inter jaw Relations Females
Males
Subnasale’Pogonion’
3.2 ± 1.9
4.0 ± 1.7
A point’-B point’
5.2 ± 1.6
6.8 ± 1.5
Upper lip anterior-lower lip anterior
1.8 ± 1.0
2.3 ± 1.2
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Orbit to Jaws Females
Males
Orbital rim’- A point’
18.5 ± 2.3
22.1 ± 3
Orbital rim’Pogonion’
16.0 ± 2.6
18.9 ± 2.8
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Harmony Values
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Full Facial Balance Females
Males
Facial angle
169.3 ± 3.4
169.4 ± 3.2
Glabella’-A point’
8.4 ± 2.7
7.8 ± 2.8
Glabella’Pogonion’
5.9 ± 2.3
4.6 ± 2.2
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Note Landmark values are dependent on TVL placement. HOWEVER
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Harmony values are independent of the position of the TVL thus making it very reliable
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SURGICAL-ORTHODONTIC CEPHALOMETRIC PREDICTION TRACING By Epker and Fish (1980 JCO) adopted in part from the mechanics developed by Ricketts for cephalometric analysis, growth prediction and visual treatment objective construction as presented by Bench, Gugino, and Hilgers. (Bioprogressive therapy)
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Cephalometric Prediction Tracing for Mandibular Advancements.
Why do prediction tracings for mandibular surgery?
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1)
2)
3)
To accurately assess the profile esthetic results which will result from the proposed surgery, To consider the desirability of simultaneous adjunctive procedures such as genioplasty, suprahyoid myotomy, etc., To help determine the sequencing of surgery and orthodontics (i.e., if the surgery is done first will it be more difficult or easier to do the indicated orthodontics), www.indiandentalacademy.com
4)
To help decide what type of orthodontics might best be employed (i.e., extraction versus non-extraction)
5)
To determine the anchorage requirements should extraction treatment be chosen
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The Cephalometric x-ray from which the prediction tracing is to be done should be taken with the patient's lips in REPOSE
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Step I: Trace the Stable Structures. ď Ž
The first step in producing a prediction tracing is to overlay a piece of acetate paper on the original cephalometric tracing and trace all structures which will not be significantly altered by the surgery and/or orthodontics
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ď Ž
For mandibular surgery, these structures will include the deep cranial features, the maxilla, the maxillary occlusal plane, the mandibular ramus and the profile to the base of the nose. Draw in Frankfort Horizontal and a line from nasion to indicate the optimum facial depth, i.e., 89° in females, 90° in males
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Step 2 - Add Skeletal Portion Changed by Surgery ď Ž
Slide the prediction tracing to the left and rotate it slightly to position bony pogonion at the optimum facial depth, keeping the mandibular occlusal plane in proper relation to the maxillary occlusal plane.
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ď Ž
Once a satisfactory position is achieved, trace the distal portion of the mandible, the corpus axis, and the soft tissue chin in this position (Fig. 2B).
There is little change in soft tissue chin thickness, so the soft tissue chin may be drawn in just as it was originally www.indiandentalacademy.com ď Ž
Step 3 - New A-Po Line. ď Ž
Construct a new line from Point A to pogonion. If a genioplasty is to be included in the procedure, the anterior portion of this altered chin, be it bone or alloplast, is now construed to be pogonion for purposes of placing the teeth.
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Step 4 - Placing the Teeth. ď Ž
First the lower incisor is placed in its optimum position
1
millimeter
ahead of the A-Po line, 1 millimeter above the occlusal plane, and at 22 degrees to the A-Po line. www.indiandentalacademy.com
Step 4 - Placing the Teeth. ď Ž
Old and new mandibles are then superimposed on Corpus Axis at PM and the change in lower incisor position is noted. Arithmetically adding twice this change to the crowding already present allows calculation of the arch length deficiency or excess. Thus, the anterior-posterior position of the lower first molar can be determined and the molar is traced in this position.
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ď Ž
The upper first molar is then placed in the desired occlusion and the upper incisor is likewise placed in the optimum position with its long axis 5 degrees more upright than the new facial axis (dotted line on the prediction tracing) .
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Step 5 - Tracing the New Lip Contours. ď Ž
Once the teeth are placed, the lip contours are traced to correspond to the new incisor positions.
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ď Ž
Once completed, the prediction tracing must be viewed as a goal toward which one is working.
ď Ž
Once the prediction tracing is as you like it, the prediction tracing can be superimposed upon the original tracings, registering on the structures not significantly altered by the surgery and/or orthodontics, and the previously stated five basic reasons to do prediction tracings for mandibular surgery can be deliberately and intelligently assessed
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Cephalometric Prediction for Maxillary Superior Repositioning.
ď Ž
Why do prediction tracings for maxillary surgery cases?
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It is even more important to do prediction tracings for maxillary surgery cases, especially when the primary direction of movement is vertical, to ascertain the effects of the prescribed surgery on the mandible.
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ď Ž
The decision to superiorly reposition the maxilla is made primarily from their esthetic features. The amount of superior repositioning is based upon the upper tooth to lip measurement which is made clinically. Still,
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We need to know if the maxilla should be moved posteriorly or anteriorly along with the upward movement
We need to know what orthodontics will be necessary.
Furthermore, we need to know if autorotation alone will produce an adequate chin or if we will wish to add a genioplasty or consider simultaneous mandibular advancement.
These questions can be answered from a prediction tracing. www.indiandentalacademy.com
Step 1 - Trace the Stable Structures.
ď Ž
As is the case with all prediction tracings, we again begin by tracing the structures which will not be modified either surgically orthodontically
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or
Step 2 - Determination of Ideal Vertical Position for the Upper Incisor. ď Ž
the measurement of the amount of upper central incisor exposed, i.e., that from stomion of the upper lip to incisal edge, be made clinically with the patient standing in a relaxed posture.
ď Ž
This is the single most important measurement in preparation for superior repositioning of the maxilla and can be confirmed cephalometrically. www.indiandentalacademy.com
Once the amount of incisor exposed beneath the upper lip is determined, the "ideal" amount of superior repositioning of the upper incisor can be determined by the formula x=
y-2 0.8
where X is the amount of superior repositioning necessary
Y is the amount of upper incisor showing.
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This formula is used because the upper lip tends to shorten approximately 20% of the amount of superior surgical repositioning; thus, a 1:1 relationship between the amount of tooth showing
and
the
amount
of
necessary does not exist. www.indiandentalacademy.com
repositioning
ď Ž
If the superior movement is to be accompanied by posterior movement of the incisors and an acute nasolabial angle is present, the lip will not shorten quite as much as predicted.
ď Ž
Conversely, with an obtuse nasolabial angle and anterior movement of the incisor, the lip will tend to shorten slightly more. www.indiandentalacademy.com
These slight variations may be disregarded,
unless
the
anterior-
posterior change is more than 6 millimeters.
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Step 2 - Determination of Ideal Vertical Position for the Upper Incisor. ď Ž
Once the desired amount of vertical incisor repositioning is determined, draw a line parallel to Frankfort horizontal on the prediction tracing to represent the desired vertical position
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Step 3 - Autorotation of the Mandible. ď Ž
Superimpose the original and
prediction
and,
keeping
tracings the
mandibular condyle in the same position, rotate the prediction
tracing
clockwise until the occlusal plane is 1 mm above the line indicating the desired position incisor. www.indiandentalacademy.com
of
the
upper
ď Ž
Trace the mandible in this position. The corpus axis and the occlusal plane are also traced in at this time
ď Ž
The change in point A and the soft tissue chin contour must be carefully studied at this time. To allow easier observation of these features, one may wish to trace, with dotted lines, the soft tissue chin, the lower incisor, and Point A. www.indiandentalacademy.com
Step 4 - Genioplasty Determination ď Ž
ď Ž
ď Ž
The next feature which must be noted is the new soft tissue chin position. (This is where the chin autorotates to.) If the chin is adequate, then genioplasty is not necessary. However, if the chin is still weak, either mandibular advancement or some type of genioplasty must be added to the treatment plan for optimum esthetics. Conversely, if the chin is too strong, then some procedure to reduce it may be required.
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Step 4 - Genioplasty Determination ď Ž
Cephalometric
criteria
which may be used to help
determine
optimum anteroposterior
soft-
tissue chin position.
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ď Ž
For bony genioplasties, the
ratio
posterior
of
anterior-
soft
tissue
change to bony change is about 0.6:1, thus, if 5 millimeters more chin is desired, advancement millimeters required. www.indiandentalacademy.com
a
bony of will
8 be
If alloplastic material is to be added, this ratio approaches 1:1 thus 5 millimeters of alloplast will produce 5 millimeters more soft tissue chin.
Dann, J.A. and Epker, B.N.: Proplast Genioplasty: A Retrospective Study of Treatment Results, Angle Orthodontist, [47:173, 1977.] www.indiandentalacademy.com
ď Ž
Once the amount of genioplasty has been determined, the new A-Po line can be constructed using the genioplasty as a new pognonion and either the old Point A or new Point A as discussed previously.
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Step 5 - Placement of Teeth In Ideal Positions. ď Ž
The lower incisor is placed in relationship to the symphysis of the mandible, the occlusal plane and the APO plane. The arch length requirements and realistic results dictate its location. www.indiandentalacademy.com
Step 6 - Nasal Outline ď Ž
With superior repositioning of the maxilla, the nasal tip is generally elevated
slightly.
This
is
more
pronounced if the maxilla is moved upward
and
pronounced
if
forward,
less
upward
and
backward. The lower border of the nose is relatively unchanged though it too may be elevated a small amount. Accordingly, the prediction tracing should be placed on the original with the fixed landmarks superimposed and the nasal outline traced
with
alterations www.indiandentalacademy.com
the
aforementioned
Step 7 - Upper Lip. The upper lip reacts to superior repositioning in the following ways:
The length from subnasale to upper lip stomion shortens 1/5 of the amount of superior repositioning,
The thickness increases by 1/3 of the amount of incisor retraction, and
The lip thins out slightly if the upper incisor is moved forward, but in all but the most extreme instances this is unnoticeable. www.indiandentalacademy.com
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ď Ž
To trace the new upper lip one should superimpose on the fixed cranial structures and study the change in incisor position. If the upper incisor is retracted such that it lies posterior to an imaginary line from the labial surface to Point A on the original tracing, then lip support has been reduced and one should trace the new lip in the following manner:
ď Ž
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Divide the vertical distance from old incisor tip to new incisor tip into fifths and the anteriorposteriordistance into thirds. Move the prediction tracing down 1/5 and forward 2/3 and draw in the new lip vermillion. Connect the new lip vermillion to the previously traced subnasale in an artistic manner. Subnasale is affected so little by superior repositioning that for prediction it can be considered a fixed point. www.indiandentalacademy.com
If the upper incisor has moved directly up the line from the labial surface to Point A of the original tracing, then lip support is unchanged and one should trace the new lip in the following manner:
ď Ž
Divide the vertical distance from old incisor tip to new incisor tip into fifths. Move the prediction tracing down 1/5 and trace the new lip, connecting it to subnasale as above.
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If, the upper incisor is forward of the line from labial surface to Point A of the original tracing, then lip support has been increased and the new lip is traced as follows:
Divide the vertical distance from old incisor tip to new incisor tip into fifths. Move the prediction tracing down 1/5. Then, While maintaining this vertical position, rotate and slide the prediction tracing such that the long axis of the upper incisor in the prediction tracing is parallel to, and the labial surface is flush with, the line from the labial surface to Point A of the original tracing. Trace the new lip in this position This effectively maintains the original lip thickness. www.indiandentalacademy.com
Step 8 - Lower Lip.
In most instances the lower lip vermillion is traced in the same relation to the lower incisors as existed prior to treatment.
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Step 8 - Lower Lip. Superimpose the lower incisor on the prediction tracing over that on the original and trace the lower lip. Where the lower incisors are retracted 5 millimeters or more, the lip tends to thicken slightly. Thus the lower incisors are not exactly superimposed, but the prediction tracing is moved slightly to the lingual of an exact superimposition (i.e., the lip thickens slightly) and the lip traced in this position
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Some artistic freedom must be employed when dealing with a hypotonic lip. the hypotonic lip may increase mildly in tonicity following production of lip competence and added support for the lip via augmentation genioplasty. IN SUCH CASES then the lip would be traced slightly thinner for purposes of prediction
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Step 9 - Chin. ď Ž
If no genioplasty is projected, the soft tissue chin will be relatively unaffected by treatment and should be traced by simply superimposing on the mandibular symphysis.)
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ď Ž
If a sliding genioplasty is done, the chin is traced by first superimposing on the original symphysis and then sliding the prediction tracing back 6/10 of the amount of the genioplasty and tracing the new chin contour.
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ď Ž
If an alloplastic implant is added, the new chin contour can be determined by simply superimposing the alloplastic implant on the original symphysis and tracing the chin
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ď Ž
Once the tracing is completed, we again must study it to determine if indeed we have achieved a satisfactory result.
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ď Ž
To once again gain optimum appreciation for the proposed changes superimposition of the original and prediction tracing is done again superimposing on the structures not significantly altered by the surgery and/or orthodontics.
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ď Ž
Frequently, it is necessary to do several prediction tracings, trying different surgical approaches to a problem (i.e., superior repositioning vs. superior repositioning with genioplasty vs. superior repositioning with mandibular advancement) before one can determine which result is best.
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Conclusion ď Ž
Certainly it is better to retreat a patient on paper than to wish that a different surgical approach had been employed after the fact
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