TERMINOLOGY, CLASSIFICATION, HISTORY AND EXAM
● Orthodontics = branch of dentistry concerned with alignment and development of teeth and jaws
Extra-oral exam
● Skeletal relationship
o AP skeletal relations (anteroposterior - maxilla and mandible in relation to each other) – zero meridian
line and Frankfort Plane
▪ 2 methods to classify skeletal pattern - palpation/bi-manual palpation OR zero meridian
methods
● I = normal relationship between maxilla and mandible
● II = mandible relatively retrusive (behind maxilla)
● III = mandible relatively protrusive (in front of maxilla)
▪ Bi-manual palpation technique:
● Index finger on cupids bow, middle finger on concavity of mandible - assess change in
inclination
● Zero-meridian method:
○ Relies on Frankfort plane (horizontal) and zero meridian line (ZML) (vertical)
● Skeletal 1 - Chin on or up to 2mm behind the ZML
● Skeletal 2 – Chin behind the ZML
● Skeletal 3 – Chin in front of the ZML
o Vertical relationship - FMPA = Frankfort mandibular plane angle; LAFH = Lower anterior face height
▪ LAFH: Glabella (mid-eyebrow) → Subnasale → soft tissue gnathion (low part of chin)
▪ Facial thirds: male 72mm, female 66mm
● Orthodontics = branch of dentistry concerned with alignment and development of teeth and jaws
Extra-oral exam
● Skeletal relationship
o AP skeletal relations (anteroposterior - maxilla and mandible in relation to each other) – zero meridian
line and Frankfort Plane
▪ 2 methods to classify skeletal pattern - palpation/bi-manual palpation OR zero meridian
methods
● I = normal relationship between maxilla and mandible
● II = mandible relatively retrusive (behind maxilla)
● III = mandible relatively protrusive (in front of maxilla)
▪ Bi-manual palpation technique:
● Index finger on cupids bow, middle finger on concavity of mandible - assess change in
inclination
● Zero-meridian method:
○ Relies on Frankfort plane (horizontal) and zero meridian line (ZML) (vertical)
● Skeletal 1 - Chin on or up to 2mm behind the ZML
● Skeletal 2 – Chin behind the ZML
● Skeletal 3 – Chin in front of the ZML
o Vertical relationship - FMPA = Frankfort mandibular plane angle; LAFH = Lower anterior face height
▪ LAFH: Glabella (mid-eyebrow) → Subnasale → soft tissue gnathion (low part of chin)
▪ Facial thirds: male 72mm, female 66mm
