Level II Unit B Summary--integrated

Dentofacial Proportions

A systematic examination of facial and dental appearance¹ should be done in the following three steps:

1. Facial proportions in all three planes of space (macro-esthetics). Examples of problems that would be noted in this first step would be asymmetry, excessive or deficient face height, mandibular or maxillary deficiency or excess, and so on. In performing this evaluation, keep in mind that both the evolutionary and prenatal development of the face can provide additional insight into the origin and significance of unusual facial morphology.
2. The dentition in relation to the face (mini-esthetics). This includes the display of the teeth at rest, during speech, and on smiling. It includes such assessments as excessive gingival display, inadequate anterior tooth display, inappropriate gingival heights, and the extent of the buccal corridors (the dark spaces in the corners of the mouth beyond the teeth).
3. The teeth in relation to one another (micro-esthetics). This includes assessment of tooth proportions in height and width, gingival shape and contour, connectors and embrasures, black triangular holes, and tooth shade

Describe ideal proportions from full-face (symmetry) and lateral (A-P/vertical) aspects.

01 - Facial Form Analysis 10 6 Orthodontic Diagnosis L4 Level II Unit B

Points of view

Facial form analysis is completed from the frontal view and the lateral view . This can be considered macroesthetics in the systematic examination of facial and dental appearance

Frontal View

• Categories analyzed
  • Symmetry
  • Vertical and transverse facial proportions
  • Tooth display

Symmetry

Jaw Asymmetry

• In terms of deviation of the mandible, a up to a 3mm deviation of the chin is not easily noticable but 4mm is very likely to be noticed

Dental Midline Asymmetry

• Dental midline off the center of the face becomes noticable when it exceeds about 3mm

Transverse facial Proportions

• Analyzing transverse facial proportions is to evaluate proportions across the width of the face. This is where the facial fifths are important

An ideally proportional face can be divided into central, medial, and lateral equal fifths

• The separation of the eyes and the width of the eyes should be equal
• Nose and chin should be centered within the central fifth (width of the nose should be same or slightly wider than the central fifth)
• the interpupillary distance should equal the width of the mouth

Vertical Facial Proportions

Vertical facial proportions are best evaluated in the context of the facial thirds. The lower third can be further subdivided into thirds

• The three vertical faction regions should be about the same size

  • Hairline to the bridge of the nose (upper third)
  • Bridge of the nose to bottom of nose (mid-face)
  • Bottom of nose to bottom of chin (lower face)

• In modern populations the lower third of the face is usually slightly longer than the central third

• Lower facial thirds

• From the base of the nose to the mouth : ideally one-third of the total height

• From mouth to the bottom of chin is two-thirds Image 1: Normal vertical proportions, frontal view.

Tooth display

Tooth display falls under step 3 “Mini-esthetics”. Conversely Miniesthetics can be subdivided into parts

1. Anterior tooth display
2. Transverse dimensions of the smile relative to the upper arch (buccal corridor)
3. The smile arc
4. Close up dental appearance (proportions and shape of teeth and gingival contours )

Anterior Tooth Display

• Maxillary Incisor display at rest
  • can be zero but is usually 2-4 mm
• Maxillary Incisor display on smile
  • Ideal: slightly below the gingival margin with 2mm of tooth coverage so that most but not quite all of the upper incisor can be seen (i.e. between 75% - 100 % exposure of the incisor)
  • acceptable range is 1mm up to 4 mm coverage of the incisor crown

Posterior Tooth Display: Buccal Corridors

• Buccal corridor: The distance between the maxillary posterior teeth and the inside of the cheek

Measurement

This one depends on gender but ideal is :

• males : 15 -24 mm
• females 10 - 17 mm

**Smile Arc

The Relationship of the curvature of the lower lip on smile to the contour of the maxillary dentition

• The ideal smile arc is where the curvature of the lowerlip matches the contour of the maxillary dentition
• Nomenclature
  • Ideal smile arc: termed consonant
  • Non - ideal/ flattened : termed non- consonant

Lateral View

Analyzed in the lateral view:

• A - P Jaw Relationships
• Incisors protrusion or retrusion
• Vertical facial thirds

The three goals of lateral facial profile analysis :

1. Establishing whether the jaws are propotionately positioned in the anteroposterior plane of space
2. Evaluation of lip posture and incisor prominence
3. Reevaluation of vertical facial proportions and evaluation of mandibular plane angle

A - P Jaw relationships from lateral view facial analysis

Patient Head Position

Make sure the patient is in natural head position

To evaluate draw two lines:

1. Dropped from bridge of the nose to base of upper lip
2. Extending from base of upper lip to the point of the chin

• A convexity in the lines indicates class II jaw relationships
• A concavity indicates Class III jaw relationships
• If they are straight it indicates a Class I jaw relationship ideal

Lip Posture and Incisor Prominence

This is the third goal of profile analysis: judging whether the incisors provide proper lip support, or are retrusive/protrusive.² Evaluate with the lips relaxed, viewing the profile.

• Observe the upper lip relative to a true vertical line through the concavity at the base of the upper lip (soft tissue point A).
• Observe the lower lip relative to a true vertical line through the concavity between the lip and chin (soft tissue point B).
• If a lip is significantly forward of its reference line → protrusive; if behind → retrusive.

When is incisor protrusion "excessive"?

Dental protrusion is judged excessive only when the lips are simultaneously prominent (forward of soft tissue A/B), incompetent (separated at rest by >3–4 mm), and strained on closure.² Lips that touch at rest, or that are separated but not forward of A/B, do not indicate excessive protrusion.

• Orthodontic tooth movement changes lip prominence: moving incisors facially increases lip support and prominence; moving them lingually decreases it.² This is a primary determinant of whether arch expansion vs. extraction is chosen to relieve crowding.

Image 1: Upper lip relative to its base (soft tissue point A) and lower lip relative to its base (soft tissue point B).	Image 2: Severely protrusive incisors in both arches — the soft tissue profile reflects the protrusion.
Image 3: Protrusive incisors on smile.	Image 4: After premolar extraction and incisor retraction — reduced lip prominence.

Describe methods, objectives, and limitations of facial form analysis.

01 - Facial Form Analysis L4 Level II Unit B

Method — A systematic clinical inspection done in two views: frontal (full-face) for symmetry, transverse/vertical proportions and tooth display; and lateral (profile, in natural head position) for A-P jaw relationships, vertical proportions/mandibular plane, and lip-incisor relationships.² Sketching the profile can help a beginner “see” the jaw relationship more accurately.

Objectives — Answer the six key questions of facial form analysis:²

1. A-P position of each jaw and how they relate to each other.
2. Vertical facial proportions, especially the lower third.
3. Is the face symmetric?
4. Is the upper arch centred in the face; are the buccal corridors wide/normal/narrow?
5. Are the incisors positioned correctly vertically relative to the lips (optimal display)?
6. Do the incisors give proper lip support, or are they retrusive/protrusive?

The overarching purpose is orthodontic triage — sorting patients by severity and prognosis, deciding whom to treat versus refer.² It is the diagnostic step where facial-form and space analysis overlap: a space-analysis result can only be interpreted once incisor A-P position is known.²

Limitations³

• Soft-tissue variation — soft-tissue thickness does not perfectly mirror the underlying skeleton, so inferences can mislead.
• Ethnicity — esthetic norms (e.g., lip prominence, profile convexity) differ between population groups.
• It is a clinical estimate — cephalometric analysis is needed when precise measurement of the jaw/tooth relationships is required.

Perform a facial form analysis.

01 - Facial Form Analysis Workbook

Step-by-step walkthrough²⁴

1. Frontal view — symmetry. Look for mandibular deviation (chin off-midline ≥4 mm is noticeable) and dental midline deviation (noticeable >3 mm). Note the location (most asymmetry involves the mandible).
2. Frontal view — proportions. Check the facial fifths (transverse) and facial thirds (vertical); subdivide the lower third (nose-base→mouth = 1/3, mouth→chin = 2/3).
3. Frontal view — tooth display. Incisor display at rest (≈2–4 mm), on social smile (75–100% of crown + small gingival show is ideal), buccal corridors (narrow/OK/wide), and smile arc (consonant vs. flat).
4. Profile — A-P jaws (NHP). Drop a line nose-bridge→upper-lip base and another upper-lip base→chin: straight = Class I; convex = Class II; concave = Class III.
5. Profile — vertical. Reassess facial thirds and estimate the mandibular plane angle (steep → long face/open-bite tendency; flat → short face/deep-bite tendency).
6. Profile — lip/incisor. Judge lip prominence vs. soft-tissue A/B and lip competence/strain to decide if incisors are retrusive, normal or protrusive.
7. Summarise the positive findings (the problem list) and triage.

Worked example (OrthoInstruction profile patients)

• **Patient 6⁵: skeletal A-P = Class II; vertical = long face; lip support = OK. → A child whose mandibular deficiency + long face would dominate the treatment plan.
• **Patient 7⁵: Class II, long face, upper lip OK but lower lip excessive → lower-incisor protrusion contributing to overjet.
• **Patient 9⁵: Class III (large mandible + some maxillary deficiency), normal vertical, inadequate upper lip support.

Image 1: Profile Patient #6 — Class II, long face.	Image 2: Profile Patient #7 — Class II, long face, excessive lower lip.

Cephalometric Analysis

02 - Cephalometric Tracing Techniques 03 - Cephalometric Superimposition 10 6 Orthodontic Diagnosis L4 Level II Unit B

Discuss the history and two major uses of cephalometric radiography.

History Cephalometrics was introduced in 1934 by Hofrath in Germany and Broadbent in the US . The original purpose was research on growth patterns in the craniofacial complex.

Important advantages of cephalometric radiography:

1. The radiographic view makes it possible to directly view the relationship of the dental arches to the underlying jaw structures, and to evaluate the relationship of the jaws to each other and to the cranial base.
2. Serial cephalometric radiographs make it possible to evaluate both growth changes and response to treatment in way that was not possible previously

Identify and trace landmarks for the cranial base, maxilla, mandible, and dentition.

Landmark glossary (UNC/UWA standard)

Definitions consolidated from the Workbook glossary⁴ and the tracing module.⁶ A good cephalometric landmark (1) can be identified accurately on a ceph, and (2) represents a known part of one of the five functional units.

Cranial base

• Sella (S) — centre of the bony crypt (sella turcica) of the sphenoid that houses the pituitary; posterior end of anterior cranial base. Stable (does not change after age 7).
• Nasion (N/Na) — anterior end of the fronto-nasal suture (junction of nasal and frontal bones); front end of anterior cranial base.
• Porion (P) — most superior point of the external auditory meatus (machine porion).
• Orbitale (Or) — lowest point on the inferior bony orbital rim (average both sides).

Maxilla

• ANS — tip of the anterior nasal spine; most anterior point of the nasal floor.
• Point A — deepest (innermost) point on the premaxillary contour between ANS and the incisor; junction of skeletal maxilla and dentoalveolar process.
• PNS — tip of the posterior nasal spine (palatine bone); junction of hard and soft palate.

Mandible

• Point B — deepest point on the anterior mandibular contour between incisor and bony chin.
• Pogonion (Pg) — most anterior point of the bony chin.
• Menton (Me) — most inferior point of the symphysis.
• Gnathion (Gn) — midpoint of the inferior chin contour, halfway between Pg and Me (bisector of mandibular and facial planes).
• Gonion (Go) — most outward/everted point at the junction of ramus and body (centre of the gonial-angle curvature).

Dentition — U1 (max central incisor tip), L1 (mand central incisor tip), U6 (max 1st molar mesial cusp tip), L6 (mand 1st molar mesial cusp tip).

Reference planes — SN (sella–nasion), FH/Frankfort (Or–Porion), Palatal plane PP (ANS–PNS), Occlusal plane OP (molars/premolars), Mandibular plane MP (Go–Gn), Y-axis (S–Gn, path of downward-forward facial growth). Superimposition landmarks — the inferior alveolar nerve canal (IAN) and the crypt of the unerupted 3rd molar are stable mandibular references.⁴

Landmarks

Landmarks come from the 5 functional units of the craniofacial complex . The 5 units are:

1. The crainum and cranial base
2. The skeletal maxilla and nasomaxillary complex
3. the skeletal mandible
4. the maxillary teeth and alveolar process
5. the mandibular teeth and alveolar process

Image 1: Anatomic location of major cephalometric landmarks.	Image 2: Linear measurements frequently made on a ceph tracing.
Image 3: Angular measurements frequently made on a ceph tracing.

Landmarks of the cranial base

There are two main landmarks :

1. Sella (s)
   • Indicates the posterior end of the anterior cranial base, and is located in the center of the cavity of sella turcica
2. Nasion (Na)
   • Indicates the front end of the anterior cranial base, and is located at the anterior end of the junction between the nasal and frontal bones

Image 1: Sella, the center of sella turcica, the midline depression in the sphenoid bone that houses the pituitary gland.	Image 2: Nasion, the anterior-superior point at the junction of the nasal and frontal bones.

Landmarks of the Maxilla

The three main landmarks for the maxilla are

1. Anterior nasal spine (ANS)
   • Inidcates the front end of the maxilla, and is located at the tip of the anterior nasal spine
2. Point A (A)
   • Associated with the anterior maxilla, located at the innermost point of the contour of the premaxilla between the anterior nasal spine and the incisor tooth
3. Posterior Nasal spine (PNS)
   • Indicates the posterior end of the maxilla and is located at the tip of the posterior spine of the palatine bone, at the junction of the hard and soft palates

Image 1: Close-up view of the maxilla as seen in a ceph.	Image 2: Anterior maxilla landmarks.
Image 3: Posterior maxilla landmark.

Landmarks of the Mandible

There are 5 important landmarks for position and orientation of the mandible (image 1):

Point B (B) – indicates the anterior part of the bony base of the mandibular dentition, and is located at the innermost point on the contour of the mandible between the incisor tooth and bony chin (image 2).

Pogonion (Pg) – the most anterior point on the contour of the chin (image 3).

Menton (Me) – the most inferior point on the mandibular symphysis (i.e., the bottom of the chin) (image 3).

Gnathion (Gn) – the center of the inferior contour of the chin, halfway between pogonion and menton (image 3).

Gonion (Go) – indicates the angle of the mandible, and is located at the center of the inferior contour of the mandibular angle (image 4).

Image 1: Close-up of mandible as seen on a ceph.	Image 2: B point, the junction between the skeletal mandible and the alveolar process.
Image 3: Landmarks on the chin.	Image 4: The landmark for the back of the body of the mandible.

Landmarks of the dentition

Four landmarks typically represent the a-p and vertical position of the incisor and molar teeth in each arch:

Upper incisor (U1) – maxillary central incisor tip)

Lower incisor (L1) – mandibular central incisor tip)

Upper molar (U6) – maxillary 1st molar, mesial cusp tip

Lower molar (L6) – mandibular 1st molar, mesial cusp tip

Image 1: Close-up view of the maxillary and mandibular teeth as seen on a ceph, with the tooth landmarks identified.	Image 2

Completing Tracings

• Sella (s)
  • Appears as a depression in the sphenoid bone that contains the pituitary gland
    • Draw the contour of the depression in the bone extending anteriorly and posteriorly over the edges of the concavity then mark pint S in the center of the concavity .. Make sure to extend the line forward along the floor of the anterior cranial base to help do superimpositions
• Nasion (N)
  • Draw the outer surface of the nasal and frontal bones past the junction , then draw a suture between the bonest. Identify point NA as the place where these lines intersect

Image 1: Outline of sella turcica.	Image 2: Tracing the fronto-nasal junction to locate nasion.

• ANS
  • Trace the superior and inferior surfaces of the anterior nasal spine and mark its tips as ANS. Then follow the external contour of the bone downward toward the upper incisor, and mark point A at the depth of this concave line
• Point A
  • At the junction between the skeletal maxilla and the maxillary dentoalveolar process, is the innermost point on the contour of the premaxilla between the ans and the incisor
• PNS
  • Trace the inner contour of the anterior maxillary alveolar process and continue posteriorly along the roof of the mouth to the end of the bony outline. Mark the end of the palatal bone contour as PNS

Image 1: Tracing the contours of the anterior maxilla to locate ANS and point A.	Image 2: Tracing the contour of the posterior maxilla to locate PNS.

• Point B
  • Trace the bony chin. Include the inner aspect of the symphysis. Follow the external contour of the bone from the chin upward toward the incisor and mark point B as the depth of the concave line
• Pogonion
  • The most prominent point on the anterior aspect of the bony chin.
• Mention is the most inferior point on the bony chin
• Gnathion
  • the point on the anterior inferior contour of the chin halfway between pogonion and mention

Image 1: Tracing the contour of the mandibular symphysis to locate point B.	Image 2: Locating pogonion, gnathion and menton (top to bottom order) on the contour of the bony chin.

• Gonion
  • Center of the inferior contour of the mandibular angle
    • Follow the lower border of the mandible posteriorly around the mandibular angle and up the posterior surface of the ramus. Mark the center of the curvature at the gonial angle point Go

• Orbitale
  • Trace the orbital rims , and trace the most inferior point on the lower border of the orbit. OR if you you can see both sides separately trace both and locate the point halfway between the two sides
• IAN and crown of unerupted third molar
  • these structures are useful as stable areas for superimposition

Image 1: Tracing the orbital rim to locate point Or. Don’t confuse the dotted line behind the orbit with the orbital rim—a common tracing mistake.	Image 2: Tracing the outline of the neurovascular bundle below where it enters the lower part of the ramus, and the outline of a third molar at the stage of crown formation.

• Drawing lips and incisor teeth
  • its important to get the root inclination correct

Evaluate if incisors are retrusive, proper, or protrusive relative to supporting bone.

Upper incisors

• The relationship of the upper incisor to the NA line is used to establish the position of the maxillary dentition relative to the maxilla
• both the millimeter distance and the inclination of the long axis of the incisor to the line are measures

Lower incisors

• The position of the lower incisor relative to the mandible is established by similar measurements to the line NB as the upper oens. In addition the prominence of the chin is establisehd by measuring the millimeter distance from the NB line to pogonion, the most prominent point of the bondy chin

Evaluate jaw relationships to the cranial base and each other.

The objective of cephalometric analysis is to establish the relationship of the facial units in the antero-posterior and vertical planes of space

Vertical Proportions

This is also known as the Sassouni analysis

Five horizontal reference lines :

1. S-N, the inclination of the anterior cranial base
2. True horizontal, the visual axis which is drawn perpendicular to the true vertical through the lower border of the orbit (Or)
3. ANS-PNS, the palatal plane
4. Functional occlusal plane, drawn along the occluding surfaces of the posterior teeth
5. Go-Gn, the mandibular plane

In a well-proportioned face the horizontal anatomic planes tend to converge toward a single point.

• If the planes intersect relatively close to the face and diverge quickly as they pass anteriorly the facial proportions are long anteriorly and short posteriorly this is known as : *skeletal open bite *
• If the planes are nearly parallel so that they converge far behind the face and diverge only slowly as they pass anteriorly, there is a skeletal predisposition toward anterior deep bite and the condition is termed *skeletal deep bite *

Anterior - Posterior Proportions

N- Perpendicular

Examining the position of the N perpendicular relative to point A or point B is a good way to quickly analyze A-P relatinships

• Point A
  • Should be one or slightly in front of the line
  • 2mm in front with a range of 0-4 mm
• Point B
  • should be slightly but not very far behind it
  • 2mm behind with a range of -4 to 0 mm
• Difference between the lines through points a and B shouldn’t be more than 4mm otherwise the teeth can’t occlude properly

ANB angle

• draw NA and NB lines and measure angle between them to judge how greater the difference aw position is ( normal is 2.8 degrees in whites and 5.5 degrees in blacks )
• ANB relates the maxilla to the mandible in the sagittal plane:
  • < 1° → mandible further forward than maxilla (concave profile, Class III)
  • 1–5° → mandible in line with maxilla (straight profile, Class I)
  • > 5° → mandible behind maxilla (convex profile, Class II)

SNA and SNB

• Can be measured to determine whether the maxilla or the mandible was in the wrong position
• Lines to draw: the S–N line (sella → nasion, the anterior cranial base) is the common reference arm for both. Then add the N–A line (nasion → point A) and the N–B line (nasion → point B); each angle is read at the vertex at nasion.
  • SNA = angle between S–N and N–A → relates the A-P position of the maxilla to the cranial base.
    • < 77° → maxilla further back than normal (retrognathic)
    • 77–85° → orthognathic
    • > 85° → maxilla further forward than normal (prognathic)
  • SNB = angle between S–N and N–B → relates the A-P position of the mandible to the cranial base.
    • < 75° → mandible further back than normal (retrognathic)
    • 75–85° → orthognathic
    • > 85° → mandible further forward than normal (prognathic)
  • SNA norms
    • 81 degrees in white
    • 84.7 degrees in black
  • SNB norms
    • 78.2 degrees in white
    • 79.2 degrees in black

Image 1: The ANB angle is an estimator of the a-p relationship of the jaws. It is quite small in patients with normal jaw relationships, like this one.	Image 2: The SNA and SNB angles indicate the degree of protrusion of the jaws relative to the cranial base, but they must be used carefully because the reference standards assume a normal inclination of SN, and we have seen already that this is not always correct.

Maxillary incisor to SN

• U1 to SN plane measures maxillary incisor angular

Mandibular incisor to Go-GN

• Mandibular incisor to Go-GN measures the angulation of the lower incisors

Additional incisor / chin measurements

Definitions and norms (Normal White / Normal Black) from the Workbook analysis sheet⁴ and Ch.6.¹

Measurement	What it means	Normal value
Interincisal angle	Angle between the long axes of the upper and lower incisors. A low angle = both incisors proclined (bimaxillary protrusion); a high angle = upright/retroclined incisors (often Class II div 2 / deep bite).	126.8° (W) / 113.8° (B); lecture quotes ≈131°7
Maxillary incisor to NA	A-P position (mm, facial surface to NA line) and angulation (long axis to NA) of the upper incisor relative to the maxilla.	3 mm / 22–23° (W) / 7.4 mm / 24.1° (B)
Mandibular incisor to NB	A-P position (mm, facial surface to NB line) and angulation (long axis to NB) of the lower incisor relative to the mandible. Protruded if linear >4 mm; proclined if angle >25°.7	5.4 mm / 27.3° (W) / 11.4 mm / 36.7° (B)
Pogonion to N-perpendicular	Position of the bony chin (Pg) relative to the true-vertical line through nasion — gauges chin prominence; integrates with lower-incisor protrusion (incisor may sit ≈2 mm ahead of Pg, not much more).	−4 to −2 mm

Compare measurement analysis versus template analysis.

02 - Cephalometric Tracing Techniques 10 6 Orthodontic Diagnosis

Both methods compare a patient to a reference group of individuals with ideal occlusion — they hold the same information, but display it differently.⁸

	Measurement analysis	Template analysis
Origin	Downs analysis (Univ. of Illinois) and successors	Bolton templates (Broadbent) — average proportions at each age of 16 M + 16 F with ideal faces (unisex)
How norms are expressed	A table of numbers (mean angles/distances for the patient’s racial/ethnic group)	A composite tracing of the average proportions
How comparison is done	Measure the patient’s angles/distances and compare each to the norm	Superimpose the template on the patient’s tracing/ceph and simply observe the differences
Strength	Quantifies exactly how far the patient deviates	Fast; gives an immediate gestalt of where and how the patient differs
Modern workflow	Digitise 40–50 landmarks; software outputs measurements	Software (e.g., SmartCeph) calls up the age/cranial-base-matched Bolton template over the digital ceph in a couple of clicks — no digitising needed

• Templates are matched by anterior cranial base length (developmental status), not chronologic age.⁸
• The mesh diagram is a graphical template variant used to show deviation from an “ideal” profile.⁹
• Key point: neither is an end in itself. Cephalometric analysis “shouldn’t become a numbers game” — the goal is to describe the relationships of the facial components, not to chase a standard set of measurements.⁸

Complete overall, maxillary, and mandibular superimpositions on composite tracings.

03 - Cephalometric Superimposition

Purpose. Overlay a tracing of the same patient from two time points to see changes in jaw and tooth relationships, and to determine whether each change is from growth, dental maturation, or orthodontic tooth movement (or surgery).¹⁰ Tracing first reduces the overwhelming information in a raw ceph to a manageable level — superimposing the radiographs themselves just produces a blur.¹⁰ All change is shown relative to the registration point/line, and the interpretation must always be reconciled with clinical findings.

By convention the initial tracing is green, the final tracing is blue; the composite is retraced in black (initial) and red (final).¹⁰

Image 1: Cranial-base (overall) superimposition.	Image 2: Maxillary and mandibular regional superimpositions, same patient.

1. Overall (cranial-base) superimposition

• Register on the S–N line at sella (S). Place the final tracing on the initial, match at S, then rotate so the S-N lines coincide.¹⁰
• Why these points are stable: the area around S is unaffected by growth after age 7 (cranial base follows the neural growth curve), so it is an ideal stable reference for orthodontic patients (who are older than 7). Nasion does drift forward with growth, which is exactly why we register at S rather than at N — otherwise forward growth of N would mask the true forward growth of the face below it.¹⁰¹¹
• Shows changes in the jaws and soft-tissue profile relative to the cranial base (i.e. overall facial growth + any growth modification from treatment).

2. Maxillary superimposition

• Register on the lingual contour of the palate (behind the upper incisors) and keep the palatal plane (ANS–PNS) level; do not make the teeth coincide.¹⁰
• Cancels out skeletal change, so it isolates movement of the maxillary teeth relative to the maxilla (A-P and vertical). Because you register on the palate and level the palatal plane, you cannot see palatal remodelling or PNS movement here.¹⁰

3. Mandibular superimposition

• Register on three internal landmarks: the lingual contour of the symphysis (anteriorly), the inferior alveolar (mandibular) canal, and the crypt of the unerupted 3rd molar.¹⁰
• Why: metallic-implant studies show these internal structures do not move as the mandible grows, whereas the surface remodels heavily — Go in particular can shift surprisingly far. So you must not rely on the mandibular plane (Go–Gn) for registration.¹⁰¹¹
• Isolates movement of the mandibular teeth relative to basal bone, and also shows condylar growth and gonial-angle remodelling (note resorption at the angle even while the ramus lengthens).

Digital cephs

Digitised cephs are superimposed by the same principles in software (e.g., Dolphin Imaging); you just select the registration line/point and the program overlays the tracings. Interpretation is still done by the human “analog computer.”¹⁰

Describe changes in composite tracings related to growth or treatment.

03 - Cephalometric Superimposition

Reading a composite — the central skill: decide whether each observed change is skeletal growth, eruption, or orthodontic tooth movement.¹⁰

• Cranial-base superimposition → overall facial/jaw growth and soft-tissue change.
• Maxillary superimposition → upper-tooth movement vs. the maxilla.
• Mandibular superimposition → lower-tooth movement vs. the mandible plus condylar growth/ramus remodelling.
• Tooth changes in the regional views = a combination of eruption + tooth movement; if a tooth moved in the regional view but the regional bone didn’t, it was true tooth movement, whereas downward travel of a molar seen only on the cranial-base view reflects the jaw growing down.

Patient #1 — Class II treated with headgear ¹

Class II treated with extra-oral headgear (to restrain the maxilla) + brackets on the upper incisors to close spaces.

• Cranial base: maxilla grew downward only (headgear minimised forward growth) and the upper lip became less prominent; the mandible grew down and forward (unaffected by the headgear) → favourable Class II → Class I correction. Mandibular plane angle increased a little (undesirable — it offsets some of the forward growth).
• Maxillary: upper anteriors retracted; upper molar stayed put A-P but erupted downward (a bit more than ideal).
• Mandibular: lower molars held their A-P position in the mandible; slight uprighting of lower incisors; large condylar growth.
• Conclusion: the molar correction came mostly from favourable mandibular growth while the headgear held the maxilla/upper teeth back — not from moving the lower teeth forward.

Image 1: Pt #1 cranial-base — differential mandibular growth.	Image 2: Pt #1 maxillary — incisors retracted, molar erupted.
Image 3: Pt #1 mandibular — favourable ramus growth, small tooth change.	Image 4: Cranial-base superimposition over one year — downward-backward maxillary and downward mandibular growth.

Patient #2 — long-face Class III, surgical timing ¹

A long-face skeletal Class III patient being prepared for orthognathic surgery. Here the superimposition decides when to operate: the closer the tracings overlap in the unregistered areas, the less growth has occurred — meaning growth has stopped and surgery is safe. Operating too early risks continued Class III growth pushing the mandible forward again.

• Very little change over the year (only minor tooth movement from pre-surgical orthodontics) → ready for surgery.
• Maxillary: upper molar was intruded (orthodontic levelling); upper incisor moved forward slightly.
• Mandibular: lower incisors were intruded to level the arch.

Image 1: Pt #2 cranial-base — minimal growth → safe to proceed with surgery.	Image 2: Pt #2 maxillary — molar intruded pre-surgically.

Space Analysis

Identify the four major assumptions of space analysis regarding growth.

Tanaka- Johnston Prediction table assumptions

1. There is a correlation between the size of erupted mandibular incisors and the size of the remaining unerupted maxillary and mandibular canines and premolars
2. The patient fits the population for the prediction table (caucasian/ Northern European decent )
3. All succedaneous teeth are developing normally
4. Assumption that the arch dimensions do not increase in growth.
5. Position of the incisors wlil not change in a way that increases or decreases arch circumference and available space
6. Assumption that the mesial shift of first molars can be predicted accurately (at least in a child with a class I skeletal pattern)

Discuss why accuracy decreases in non-Class I jaw relationships.

There are two main reasons as to why accuracy decreases in non-class I jaw relationships

Reason 1

The first reason is due to assumption 5 that the position of the incisors will not change in a way that increases or decreases arch circumference and available space

• In class II the lower incisors will tip facially
  • this increases space in the lower arch while upper incisors may move either facially or lingually
• In class III patients the lower incisors are likely to tip lingually
  • this increases space in the lower arch
  • upper incisors often tip facially, increasing space in the upper arch

Reason 2

• Assumes that a mesial shift of molars can be predicted accurately
• The different partn of molar shift in children with skeletal class II or class III growth patterns restricts the applicability of space analysis

Identify necessary diagnostic materials.

1. Dental casts
2. Sketched or digital image of patients profile
3. Measuring Instrument : Boley gauge
4. A space analysis form (form 42)
5. Pencil

Perform a space analysis as described in the practical exercise.

Workbook L4 Level II Unit B

Purpose: measure the space available between the first permanent molars and compare it to the space required (erupted incisors measured directly + canines/premolars estimated from the Tanaka-Johnston table) to give an arch-length discrepancy.⁴

Materials: dental casts (or digital images), a sketch/image of the patient’s profile, a (modified, pointed) Boley gauge, a space-analysis form, pencil.⁴

Prerequisite: an accurate cast of a child in mixed dentition (all permanent first molars and incisors erupted); trim the cast to establish the correct occlusal relationship before measuring.⁴

Step-by-step walkthrough (per arch)⁴

1. Space available — measure the arch in 4 segments (a, b, c, d) along the line of occlusion from mesial of one first molar to mesial of the other; sum them.
   • Regions a–d are straight-line approximations of the curved arch — two per side: a posterior segment (molar → canine) and an anterior segment (canine → midline) on the right (a, b) and left (c, d) — used because a curved arch can’t be measured accurately in one straight pass.
2. Incisor width — measure the mesiodistal width of each erupted permanent incisor; sum (the 4 lower incisors are the predictor).
3. Estimate unerupted teeth (Tanaka-Johnston) — estimated width of canine + 2 premolars per quadrant = ½ (Σ 4 mandibular incisor widths) + 10.5 mm (mandibular arch) or + 11.0 mm (maxillary arch); then ×2 per arch. The same lower-incisor sum predicts both arches.
4. Space required = incisor widths + estimated canine/premolar widths.
5. Discrepancy = space available − space required (negative = crowding, positive = spacing).
6. Molar shift adjustment — for Class I patients with end-to-end molars, add the expected mesial drift (subtract from the discrepancy).⁴
7. Adjust for skeletal class, molar occlusion and lip support (see below).

Step	What you record
Space available	a + b + c + d (mm)
Space required	Σ incisors + estimated (C + P1 + P2) ×2
Discrepancy	available − required (− = crowding)
Adjustments	molar shift, incisor protrusion/retrusion, lip support

Refining the discrepancy⁴

• Skeletal class (from profile analysis) projects incisor stability and its space implications: Class I → incisors stay stable; Class II → incisors tip facially, increasing available space; Class III → incisors tip lingually, reducing available space.
• Molar relationship should correlate with the skeletal class. In a skeletal Class I: a Class II molar relationship indicates maxillary space loss; a Class III molar relationship indicates mandibular space loss/shortage.
• Leeway space — Class I skeletal only = (C + D + E) − (3 + 4 + 5) (surplus of the primary canine + molars over their permanent successors). Confirm on the cast: drop a vertical line at the MB cusp tip of the upper permanent 1st molar and another at the buccal groove of the lower permanent 1st molar; the gap is the distance to be closed for Class I occlusion, achieved by mesial shift of the lower 1st molar, greater mandibular than maxillary growth, or both.

Worked example (Step 2, Ackerman-Proffit casts) ¹

Symmetric arches, moderate crowding ≈ −6 mm in both arches. This raw number is not yet a treatment decision — it must be interpreted in the light of incisor protrusion/retrusion and buccal-corridor width before deciding expansion vs. extraction.

Interpret results considering retrusive or protrusive incisors.

Workbook 01 - Facial Form Analysis

The arch-length number is meaningless until you know the A-P incisor position (from facial-form or cephalometric analysis), because moving incisors changes arch circumference:¹²²

Incisor position now	What it implies for the space number	Treatment leaning
Protrusive (lips over-supported, forward of A/B)	Incisors should be retracted, which reduces arch length → effective crowding is worse than the raw number	Favours extraction; arch expansion contraindicated
Normal	Raw number is taken at face value	Treat per discrepancy magnitude
Retrusive (lips under-supported, inadequate)	Incisors can be proclined/advanced, which gains arch length → effective crowding is less than the raw number	Favours non-extraction / expansion

• Lip support / posture read from the profile — prominence of the lips relative to the base of the nose and chin (±Ricketts’ E-line, nose tip → soft-tissue chin): over-supported/protrusive lips → protrusive incisors (retracting them lessens lip protrusion but reduces arch space); under-supported/retrusive lips → retrusive incisors (proclining them adds lip support and gains arch space).⁴
• This is the formal link between the space-analysis and facial-form objectives.

Systematic Description

Identify the five major characteristics of systematic malocclusion description.

Contemporary Orthodontics (sixth edition) Annotations

The five major characteristics of the systemic malocclusion description , also known as the Ackerman and Proffit Classification

1. Dentofacial appearance
2. Teeth/Arch form
3. Transverse characteristics
4. Sagittal (A-P)
5. Vertical

1. Dentofacial appearance

• Dentofacial appearance consists of
  • Symmetric analysis
  • Proportionality
  • Profile
    • concave
    • straight
    • convex
  • Lips
    • protrusive
    • normal
    • retrusive
  • Incisor display
    • Excessive
    • Normal
    • Inadequate

2. Teeth / Arch Form

The analysis of the the teeth /arch form consists of

• Alignment

• symmetry

• Crowding

• Spacing

• when doing this sort of analysis, its helpful to categorize that there are two important lines in the dentition 05 - Ackerman-Proffit Classification

  1. functional line of occlusion (Angle’s line)
  2. Esthetic line of dentition
     • runs along the outer surface of the upper teeth

Image 2, functional and esthetic lines of occlusion: Green line, esthetic line of the dentition; red line, functional line of occlusion (Angle’s line)

3. Transverse

• Transverse analysis consists of noting transverse deviations (i.e. too wide or too narrow )
  • buccal
  • palatal
    • unilateral
    • bilateral
  • Dental
  • Skeletal

4. Sagittal (a-p)

• Sagittal analysis consists mostly of angles classes of maloclussion
  • Class I (normal)
  • class 1 with anterior displacement
  • Class II division 1
  • Class II division 2
  • Class III
  • Dental or skeletal

5. Vertical

• Vertical deviation consists of
  • Open bite, anterior
  • open bite, posterior
  • Deep bite, anterior
  • Collapsed bite, posterior
  • Dental
  • Skeletal

6. Relationships Between the ackerman classifications

• There are three more relationships: Yaw , roll and pitch
• YAW:
  • horizontal plane
  • describes trans-sagittal plane
  • “looks like a sprinkler”
• Pitch
  • Vertical plane
  • describes the saggito-vertical plane
  • “looks like a pitchers arm ”
• Roll
  • Describes vertico-transverse plane

Relate incisor crowding to incisor protrusion.

05 - Ackerman-Proffit Classification 10 6 Orthodontic Diagnosis

Crowding and protrusion are two expressions of the same arch-length discrepancy — the difference between the size of the teeth and the space available to align them.¹³

• If crowded teeth are aligned within the existing arch by proclining (advancing) the incisors, arch circumference increases and the crowding is relieved — at the cost of protrusion. So crowding can be “converted” into protrusion.
• Conversely, retracting protrusive incisors reduces arch length and re-creates crowding.
• Therefore “my teeth stick out” and “my teeth are crooked” are the same problem measured differently (Calvin Case’s historical critique of Angle).¹³
• Practical consequence: adding protrusion to the classification does not change how crowding is measured — it changes how the arch-length discrepancy is interpreted (and is why extraction may be needed rather than always expanding the arch).¹³

Differentiate skeletal versus dental posterior crossbites, Class II/III malocclusions, and open/deep bites.

05 - Ackerman-Proffit Classification 10 6 Orthodontic Diagnosis L4 Level II Unit B

In every plane of space the key diagnostic question is “is this primarily a skeletal (jaw) or a dental (tooth) problem?” — because the answer dictates the treatment plan. Two patients can have analogous malocclusions (the teeth look identical, same Angle class) yet non-homologous causes (one dental, one skeletal) that must be treated differently.¹³

Trait	Skeletal (jaw-based)	Dental (tooth-based)
Posterior crossbite	Narrow maxilla → narrow palatal vault (“rule of thumb”: thumb won’t fit). Maxillary teeth lean facially in partial compensation. (Or a too-wide mandible — confirm with mandibular intermolar width.)1314	Normal-width palatal vault; maxillary teeth simply tipped lingually. Intermolar width alone does not distinguish — palatal-vault width does.1314
Class II	Jaw discrepancy — mandibular retrusion / maxillary protrusion seen on profile + ceph; teeth well-related to their own jaw.13	Normal jaws; upper teeth displaced anteriorly and/or lower teeth lingually on a normal skeletal base.
Class III	Large/prominent mandible and/or deficient maxilla (concave profile, reverse overjet).13	Normal jaws; maxillary teeth retroclined and/or mandibular teeth proclined.
Open bite (anterior)	Long anterior face height; palatal plane rotated down posteriorly, mandible rotated down-back, steep MP angle; incisors erupted normally/excessively. Do not correct by elongating incisors.1314	Localised failure of anterior alveolar/incisor eruption on normal facial proportions (e.g., habit/thumb-sucking); normal face height.
Deep bite (anterior)	Short anterior face height, low (flat) mandibular plane angle, long posterior face height (skeletal deep-bite jaw pattern).13	Excessive incisor vertical overlap on normal facial proportions — over-eruption of incisors / under-eruption of posteriors.

• Distinguishing dental vs. skeletal open bite clinically: check facial height, lip competence, tooth display, then confirm cephalometrically (skeletal = long face + increased vertical planes).¹⁴
• Skeletal open bite = obtuse gonial angle, longer ramus/cranial base; skeletal deep bite = decreased vertical facial height and flat cephalometric planes.¹⁴

---

Sources / Footnotes

Footnotes

1. Contemporary Orthodontics 6e, Ch.6 — Orthodontic Diagnosis. ↩ ↩²

2. 01 - Facial Form Analysis — lateral view: A-P jaw relationships, lip-tooth relationships, six critical questions, orthodontic triage. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

3. L4 Level II Unit B — facial form analysis methods, objectives and limitations (soft-tissue variation, ethnicity). ↩

4. Workbook — cephalometric glossary, UNC/UWA analysis sheet (norms), space-analysis form and Tanaka-Johnston procedure. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

5. 01 - Facial Form Analysis — profile exercise patients #6–#10 (worked facial-form cases). ↩ ↩² ↩³

6. 02 - Cephalometric Tracing Techniques — landmark definitions and tracing of cranial base, maxilla, mandible, dentition. ↩

7. L4 Level II Unit B — incisor evaluation: interincisal angle (~131°), 1-NA, 1-NB (proclined >25°, protruded >4 mm). ↩ ↩²

8. 02 - Cephalometric Tracing Techniques — measurement (Downs) vs. template (Bolton) analysis, digital cephs. ↩ ↩² ↩³

9. L4 Level II Unit B — mesh diagram / template comparison. ↩

10. 03 - Cephalometric Superimposition — overall/maxillary/mandibular technique, registration rationale, Patient #1 and #2 interpretation, digital cephs. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

11. 03 - Cephalometric Superimposition — stability of S (registration at sella, not nasion) and of internal mandibular landmarks (IAN canal, 3rd-molar crypt, lingual symphysis). ↩ ↩²

12. 05 - Ackerman-Proffit Classification — Step 2 alignment/symmetry, arch-length discrepancy interpreted with incisor protrusion/retrusion. ↩

13. 05 - Ackerman-Proffit Classification — crowding vs. protrusion as one arch-length discrepancy; skeletal vs. dental differentiation in all three planes; analogous vs. homologous. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

14. L4 Level II Unit B — differential diagnosis of crossbites, Class II/III, and skeletal vs. dental open/deep bite. ↩ ↩² ↩³ ↩⁴ ↩⁵