Cheat Sheet - Facial Analysis
Frontal View (Full-Face)
Symmetry Thresholds
- Mandibular / chin deviation: up to 3 mm off-midline is NOT easily noticeable; ≥4 mm is very likely noticed.
- Dental midline: off the centre of the face becomes noticeable when it exceeds ~3 mm.
- Most asymmetry involves the mandible — note the location.
| Feature | Not noticeable | Noticeable |
|---|---|---|
| Chin / mandibular deviation | ≤3 mm | ≥4 mm |
| Dental midline shift | ≤~3 mm | >~3 mm |
Facial Fifths (Transverse) — Where the Lines Go
- An ideally proportioned face divides into central, medial, and lateral equal fifths (5 equal vertical columns).
- The separation of the eyes and the width of each eye should be equal (each = one fifth).
- The nose and chin are centred within the central fifth; nose width = or slightly wider than the central fifth.
- The interpupillary distance should equal the width of the mouth.
Facial Thirds (Vertical)
- Three equal thirds: hairline → bridge of nose (upper third); bridge of nose → base of nose (mid-face); base of nose → bottom of chin (lower face).
- In modern populations the lower third is usually slightly longer than the central third.
- Lower-third subdivision: base of nose → mouth = one-third; mouth → bottom of chin = two-thirds.
Tooth Display (Mini-Esthetics)
| Parameter | Ideal / norm |
|---|---|
| Maxillary incisor display at rest | can be 0 but usually 2–4 mm |
| Maxillary incisor display on smile | ideal = lower lip slightly below the gingival margin with ~2 mm coverage so 75–100% of the incisor shows; acceptable = 1 mm of gingival show up to 4 mm of crown coverage |
| Buccal corridor (gap: maxillary posteriors ↔ inside of cheek) | males 15–24 mm; females 10–17 mm |
| Smile arc (lower-lip curve vs maxillary incisal contour) | ideal = matching = “consonant”; flattened = “non-consonant” |
Profile / Lateral View
Assess in natural head position.
Soft-Tissue Points to Use
- Soft-tissue point A = the concavity at the base of the upper lip.
- Soft-tissue point B = the concavity between the lower lip and the chin.
- E-line (Ricketts) = a line from the nose tip → soft-tissue chin — used to assess how each lip relates to nose & chin.
A-P Jaw Relationship — the Two Lines
- Line 1: from the bridge of the nose → base of the upper lip.
- Line 2: from the base of the upper lip → point of the chin.
- Straight = Class I (ideal); convex = Class II; concave = Class III.
Lip Posture / Incisor Prominence
- Assess with the lips relaxed. Observe the upper lip vs a true-vertical line through soft-tissue A, and the lower lip vs a true-vertical through soft-tissue B.
- Lip significantly forward of its reference line = protrusive; behind = retrusive.
- Moving incisors facially increases lip support/prominence; lingually decreases it (a primary determinant of expansion vs extraction).
Pitfall — when is protrusion "excessive"?
Incisor 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.
Lips that touch at rest, or are separated but not forward of A/B, do NOT indicate excessive protrusion.
Mandibular Plane Angle (Clinical Estimate)
- Steep MP → long-face / open-bite tendency.
- Flat MP → short-face / deep-bite tendency.
- Normal = 25* , (22- 28*)
Closing Checklist — Six Key Questions
- A-P position of each jaw and how they relate to each other.
- Vertical facial proportions, especially the lower third.
- Is the face symmetric?
- Is the upper arch centred in the face; are the buccal corridors wide/normal/narrow?
- Are the incisors positioned correctly vertically relative to the lips (optimal display)?
- Do the incisors give proper lip support, or are they retrusive/protrusive?
Source: Level II Unit B Summary—integrated · L4 Level II Unit B · Workbook · 01 - Facial Form Analysis · 10 6 Orthodontic Diagnosis