Transcript
Cephalometric radiography
Islam Kassem
ikassem@dr.com
• Cephalometric radiography is a standardized and reproducible form of skull radiography used extensively in orthodontics to assess the relationships of the teeth to the jaws and the jaws to the rest of the facial skeleton.
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Standardization was essential for the development of cephalometry
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Main indications
1-Orthodontics
2-Orthognathic
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1-Orthodontics
1- Initial diagnosis — confirmation of the underlying skeletal and/or soft tissue abnormalities
2-Treatment planning
3- Monitoring treatment progress, e.g. to assess
anchorage requirements and incisor inclination
4- Appraisal of treatment results
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2-Orthognathic surgery
1- Preoperative evaluation of skeletal and soft
tissue patterns
2- To assist in treatment planning
3-Postoperative appraisal of the results of
surgery and long-term follow-up studies.
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Equipment
• Cephalostat (or craniostaf)
• Cassette (usually 18 x 24 cm).
• Aluminium wedge filter.
• X-ray generating apparatus.
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Main radiographic projections
1-True cephalometric lateral skull
2- Cephalometric postero-anterior of the jaws
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1-True cephalometric lateral skull
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Cephalometric tracing /digitizing
• The outline and inclination of the anterior teeth
• The positional relationship of the mandibular
and maxillary dental bases to the cranial base
• The positional relationship of the dental bases
to one another, i.e. the skeletal patterns
• The relationship between the bones of the
skull and the soft tissues of the face.
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One-shot cephalometric imaging
Multiple image format including exclusive 30x30 cm Autotracing
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Main Cephalometric points
• Sella (S). The centre of the sella turcica, • (determined by inspection). • Orbitale (Or). The lowest point on the infraorbital margin. • Nasion (N). The most anterior point on the frontonasal
suture. • Anterior nasal spine (ANS). The tip of the anterior nasal
spine. • Subspinale or point A. The deepest midline point between
the anterior nasal spine and prosthion. • Prosthion (Pr). The most anterior point of the alveolar crest
in the premaxilla, usually between the upper central incisors.
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• Infradentale (Id). The most anterior point of the alveolar crest, situated between the lower central incisors.
• Supramentale or point B. The deepest point in the bony outline between the infradentale and the pogonion.
• Pogonion (Pog). The most anterior point of the bony chin. • Gnathion (Gn). The most anterior and inferior point on the bony
outline of the chin, situated equidistant from pogonion and menton.
• Menton (Me). The lowest point on the bony outline of the mandibular symphysis.
• Gonion (Go). The most lateral external point at the junction of the horizontal and ascending rami of the mandible.
• Note: The gonion is found by bisecting the angle formed by tangents to the posterior and inferior borders of the mandible.
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Posterior nasal spine (PNS). The tip of the posterior spine of the palatine bone in the hard palate.
Articulare (Ar). The point of intersection of the dorsal contours of the posterior border of the
mandible and temporal bone.
Porion (Po). The uppermost point of the
bony external auditory meatus, usually regarded
as coincidental with the uppermost point of the
ear rods of the cephalostat.
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Main cephalometric planes and angles
Frankfort plane. A transverse plane through the skull represented by the line joining porion and orbitale. Mandibular plane. A transverse plane through the skull representing the lower border of the horizontal ramus of the mandible. There are several definitions: • A tangent to the lower border of the mandible • A line joining gnathion and gonion • A line joining menton and gonion.
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Maxillary plane. A transverse plane through the skull represented by a joining of the anterior and posterior nasal spines. SNplane. A transverse plane through the skull represented by the line joining sella and nasion. SNA. Relates the anteroposterior position of the maxilla, as represented by the A point, to the cranial base. SNB. Relates the anteroposterior position of the mandible, as represented by the B point, to the cranial base. ANB. Relates the anteroposterior position of the maxilla to the mandible, i.e. indicates the anteroposterior skeletal pattern — Class I, II or III.
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Maxillary incisal inclination. The angle between the long axis of the maxillary incisors and the maxillary plane.
Mandibular incisal inclination. The angle
between the long axis of the mandibular incisors and the mandibular plane.
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CEPHALOMETRIC ANALYSIS
ANALYSIS UTILIZING THE CEPHALOMETRIC TRACING
1) Describe the subject’s dento-facial morphology
2) Quantitative description of morphological deviations
3) Make diagnostic and treatment planing decisions
2) Evaluate change over time - treatment induced and growth process
Morphological Description
• Skeletal - horizontal and vertical
• Dental - horizontal and vertical
• Comparing individual subject’s tracing to the “ideal”
Cephalometric Evaluation
• Identification of anatomic landmarks
• Landmarks: stable reference structures and maxillary and mandibular skeletal and dental
• Graphically relating the dento-facial elements to these reference structures
• Angular and or linear measurements
METHODS OF CEPHALOMETRIC ANALYSIS
• Two basic approaches
• Metric approach - use of selected linear and angular measures
• Graphic approach - “overlay” of individual’s tracing on a reference template and visual inspection of degree of variation
Metric Method - Use of selected linear and
angular measures
Graphic Method - Use of a Composite
Template
GOALS OF CEPHALOMETRIC ANLYSIS
• Evaluating relationships, both horizontal and vertical of 5 major functional components of the face:
• the cranial base;
• the maxilla; the mandible,
• the maxillary and mandibular dento-alveolus
REFERENCE LINES
• Frankfort’s Horizontal (porion to orbitale)
• Sella - Nasion line
• True horizontal plane
• True vertical plane
sella nasion
porion orbitale
Reference Lines
SKELETAL HORIZONTAL - MAXILLA
SNA 82 ± 2 deg
NA TO FH 90 ± 3 deg
s n
a
F H
SKELETAL HORIZONTAL - MANDIBLE
s n
b
P g
F H
SNB 80 ± 2 deg
N-PG TO FH
88 ± 6 deg
SKELETAL HORIZONTAL - MAXILLA TO MANDIBLE
N
A
B
ANB 2 ± 2 deg
SKELETAL VERTICAL
F H
S
G N M E
G O
FH TO GOGN 22 ± 5 deg
Y AXIS 59 ± 6 deg
LFH 55% OF TFH
DENTAL - UPPER TO LOWER INCISOR
INTERINCISAL 130 ± 5 deg
DENTAL - MAXILLARY INCISOR
F H
N
A
U1 TO FH 110 ± 5 deg
U1 TO NA 22deg
U1 TO NA 4mm
DENTAL - MANDIBULAR ANTERIOR
GO
GN
B
N
L1 TO NB 25deg
L1 TO NB 4mm
L1 TO GOGN 91 ± 6deg
SOFT TISSUE
NASOLABIAL ANGLE 102 ± 8 deg
L.LIP TO E PLANE -2 ±2mm
Limitations of the Metric Method
• Stable reference structures are only relatively stable
• Validity of landmarks
• Error in landmark identification
Graphic Method
• Template
• Changes between 2 time points
Superimposition Method - on the cranial
base
Maxillary and mandibular superimposition
Limitations of Cephalometric Analysis
• Individual variability
• Ethnic variability
• Gender variability
2-Cephalometric postero-anterior of the jaws
• This projection is identical to the P view except that it is standardized and reproducible. This makes it suitable for the assessment of facial asymmetries and for preoperative and postoperative comparisons in orthognathic surgery involving the mandible.
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ikassem@dr.com
Thank you
• You can get the lecture on
• http://www.slideshare.net/islamkassem
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