Cephalometics

Question 1

Cephalometrics

Answer 1

Interpretation of lateral head films taken under standardized conditions

Question 2

Uses of cephalometrics

Answer 2

Diagnosis of skeletal and dental malocclusions

planning orthodontic treatment

evaluation of orthodontic treatment results

prediction and evaluation of growth related changes

Question 3

Cephalostat

Answer 3

Distance between xray source and midsagittal plane of patient is kept constant at 5 feet

Distance between midsagittal place and film is 15cm

Pt’s head is positioned w/ frankfort horizontal plane parallel to the floor

Question 4

Patient position

Answer 4

Bilateral ear rods are placed in the auditory meatus

Midsaggital plane is vertical and perpendicular to the xray beam and parallel to the film

Line connecting superior border of external auditory meatus to the infraorbital rim (Frankfort Horizontal plane) is parallel to the floor

Question 5

Answer 5

Sella (Se): geometric center of the pituatary fossa

Nasion (Na): most anterior point of the frontonasal suture

Basion (Ba): Lowest point on the anterior rim of foramen magnum

SN plane: line joining Se and Na, anterior cranial base

Question 6

Answer 6

Porion (Po): most superior point on the external auditory meatus

Orbitale (Or): most inferior point on the orbit

Pterygomaxillare (Ptm): jxn of the pterygomaxillary fissure and foramen rotundum

Frankfort Horizontal Plane: Line joining Po and Or

Question 7

Answer 7

Anterior nasal spne (ANS): anterior tip of the sharp bone process of the maxilla at the lower border of the nasal opening

Posterior nasal spine (PNS): posterior spine of the palatine bone

Subspinale (Point A): the most posterior midline point in the concavity of the maxilla

Supramentale (Point B): The most posterior midline point in the concavity of the mandible

Question 8

Answer 8

Pogonion (Pog): The most anterior point on the chin

Menton (Me): The lowest point on the symphysis of the mandible

Ganthion (Gn): Midpoint of the anterior and inferior points on the chin

Question 9

Answer 9

Gonion (Go): Point on the curvature of the angle of the mandible located by bisecting the lines tangent to the posterior ramus and the inferior border of the mandible

Lines joining the tips of the incisal edges and the roots of upper and lower incisors

Question 10

Answer 10

N’: soft tissue nasion

Pronasale: most prominent point on the nose

Subspinale (Sn): point at which the columella merges with the upper lip

Question 11

Answer 11

Labrale superius (Ls): most anterior point on upper lip

Stomion superius (Stms): most inferior point on the upper lip

Stomion inferius (Stmi): most superior point on the lower lip

Labrale inferius (Li): Median point on the lower margin of the lower lip

Question 12

Answer 12

Superior Labial sulcus (SLS): the point of greatest concavity in the midline of the upper lip

Inferior labial sulcus (ILS): the point of greatest concavity in the midline of the lower lip

Soft tissue pogonion (Pog’)

Soft tissue menton (Me’)

chin throat point

Question 13

Answer 13

SNA: Sella-Nasion-A point angle

relation of maxilla to the cranial base

normal value: 82 +/- 2

greater value indicates prognathic maxilla

lesser value indicates retrognathic maxilla

relative to cranial base

Question 14

Answer 14

SNB: Sella-Nasion-Point B angle

position of mandible relative to cranial base

normal value 80 +/- 2

greater value indicates prognathic mandible

lesser value indicates retrognathic mandible

relative to cranial base

Question 15

Answer 15

ANB: A point-nasion-B point angle

relation of maxilla to mandible

normal value: 2 +/- 2 degrees

greater value indicates class II relation

lesser value indicates class III relation

doesnt indicate which jaw is affected

Question 16

Answer 16

mandibular plane angle (FMA):

angle formed by FH plane with mandibular plane (Gonion-Gnathion)

indicates the direction of growth of the mandible in relation to the FH plane

normal value: 26 +/- 4

Question 17

Answer 17

SN-MP:

angle formed by sella-nasion plane with mandibular plane (gonion-gnathion)

indicates the direction of mandibular growth in relation of the cranial base

normal base: 32 degrees

Question 18

Answer 18

U1-NA (mm):

indicates the proclination of upper incisor w/ respect to the nasion

normal value: 4mm

U1-SN (degrees):

indicates the inclination of upper incisor w/ respect to cranial base

helps in planning for incisor retraction during orthodontic treatment

Question 19

Answer 19

L1-NB (mm):

indicates lower incisor proclination w/ respect to nasion point

normal value: 4mm

L1-MP (degrees):

indicates lower incisor inclination w/ respect to mandibular plane

helps in planning treatment mechanics

normal value: 90 +/- 7 degrees

lower incisor inclination helps in planning orthodontic treatment in many cases

Question 20

Answer 20

E line: Esthetic line

plane extending from soft tissue tip of nose to soft tissue chin

determines balance between nose, lips and chin

normal value:

U lip - E line: -6 +/- 2mm

L lip - E line: 2 +/- 2 mm

(at 9 yrs of age, lips become less protrusive w/ age)

Helps in planning for lip retraction

Question 21

Superimpositions

Answer 21

Evaluation of growth changes

evaluation of effect of treatment mechanics

superimpositions on stable cephalometric landmarks (sella, Ptm, anterior cranial base) for skeletal changes

superimposition on maxillary plane (ANS-PNS) and internal maxillary structures and lower border of mandible along w/ developing third molar and inferior canal for dental changes