Oral Anatomy & Tooth Morphology – Comprehensive Bullet-Point Notes

Hard & Soft Tissues Covered

• Lecturer’s roadmap (p.2) – course will span:
  • Hard tissues • Soft tissues • Mouth & oral cavity • Gingiva + PDL • Tissues of the tooth • Numbering systems • Tooth surfaces • Tooth characteristics • “Mountains & Valleys” (elevations ∧ depressions)

Skeletal Framework of the Oral Cavity

• Maxilla (p.3)
  • Articulates with: Ethmoid, Frontal, Lacrimal, Nasal, Palatine, Inferior nasal conchae, Sphenoid, Temporal, Vomer, Zygomatic, Parietal, Occipital, Mandible via dentition.
  • Key features: Palatal process, Palatine suture, Frontal process, Alveolar process, Zygomatic process, Canine & Incisive fossae.
• Mandible (p.4)
  • Same cranio-facial bony neighbours + TMJ.
  • Landmarks: External oblique line, Body, Alveolar process, Mental foramen.

Extra-Oral Soft-Tissue Landmarks – “The Lips”

• Names/locations appear twice (p.5-6) – critical for charting lesions or esthetic work.
  • Nasolabial fold, Subnasale, Philtrum & Philtral column, Cupid’s bow, Philtral dimple, Tubercle, Vermilion border (junction skin ↔ mucosa).
  • Cutaneous vs mucosal lips; white skin roll; labiomental crease; oral commissure.
• Terminology: “Labial” = toward the lips.

Intra-Oral Soft-Tissue Survey

• Palate & Oropharyngeal Gate (p.7)
  • Hard palate, Soft palate, Palatine raphe, Uvula, Rugae.
  • Anterior pillar of fauces = palatoglossal arch; Posterior pillar = palatopharyngeal arch.
  • Tonsils, Pterygomandibular raphe, Retromolar pad, Dorsal tongue.
• Tongue (p.8)
  • Dorsal vs Ventral.
  • Lingual frenum; openings of Wharton’s duct (sub-mandibular gland).
  • “Lingual” = toward tongue.
• Frenum Attachments (p.9,10)
  • Labial frenum – may cause diastema when high/short.
  • Buccal frenum – cheek-side.
  • Clinical exercise: decide if attachment is normal or pathological.
• Gingival & Vestibular Regions (p.11-15)
  • Mucogingival junction (keratinized ↔ non-keratinized).
  • Attached gingiva, Free gingiva, Gingival sulcus (potential space; probed diagnostically; $1–3\,\text{mm}$ healthy).
  • Interdental papilla; Buccal corridor concept (esthetic width of posterior “dark space”).
  • “Selfie” exercise – orient students.

Periodontal Ligament (PDL) Complex (p.16)

• Fiber groups + orientation:
  • Alveolar crest, Horizontal, Oblique (bulk load bearing), Apical, Inter-radicular, Trans-septal, Gingival group.
• Functions: suspends tooth, absorbs shock, supplies proprioception, can remodel (bone ↔ cementum).
• Radiographically appears as $0.1–0.25\,\text{mm}$ radiolucent line.

Tissues of the Tooth (p.18-24)

• Enamel
  • $\approx95\%$ hydroxyapatite; hardest body substance; thickest occlusally/incisally; thinnest at CEJ; rods perpendicular to DEJ except cervically (p.19).
• Cementum
  • External root layer; $50–65\%$ mineralized; thinnest cervically; sharpey’s fiber insertion (p.20).
• Dentin
  • $\approx70\%$ mineralized; bulk tissue; tubules with odontoblastic processes; hydrodynamic theory of pain (p.21).
• Pulp
  • Vascular-nerve CT; housed within chamber + canals; functions: Formative, Sensory, Nutritive, Defensive (p.22).
• Junctions (p.23)
  • CEJ (“cervical line”): enamel ↔ cementum; steeper mesially, flattens posteriorly.
  • DEJ: enamel ↔ dentin interface.
• Anatomic vs Clinical Crown/Root (p.24-25)
  • Anatomic defined by tissue covering; clinical varies with eruption/gingival level.

Tooth Classification & Numbering (p.27-35)

• Permanent formula:
  • Classes per quadrant: Incisors (2), Canine (1), Premolars (2), Molars (3). Total $32$.
• Primary (deciduous) formula: Incisors (2), Canine (1), Molars (2). Total $20$.
• Universal System (US):
  • Permanent $1–32$ clockwise UR→UL→LL→LR.
  • Primary $A–T$ similarly.
• Palmer: quadrant brackets + numbers $1–8$ (permanent) or letters $A–E$ (primary) from midline.
• International (FDI): two-digit code: quadrant (1-4 permanent; 5-8 primary) + tooth position $1–8$/$1–5$.
• Knowing three systems is essential for chart transfer, board exams, and international cases.

Tooth Surface Terminology (p.38-44)

• “Outer/Facial”
  • Labial (anterior) vs Buccal (posterior).
• “Inner/Lingual”
  • Lingual (mand.&max.) vs Palatal (maxillary only).
• Biting surfaces
  • Incisal edge (anteriors) ; Occlusal surface (posteriors).
• Gingival reference levels
  • Cervical, Apical.
• Proximal surfaces
  • Mesial (toward midline) ; Distal (away).
• Try-it diagram (p.43) – label directions clinically.

Division into Thirds & Spatial Angles (p.45-46)

• Crown can be divided (facial & lingual views) into Cervical, Middle, Incisal/Occlusal thirds; proximally into Facial, Middle, Lingual thirds; root into Cervical, Middle, Apical.
• Line angle = intersection of two surfaces (e.g., mesiolabial).
• Point angle = intersection of three (e.g., mesiobucco-occlusal).
• Dimensions: incisocervical, mesiodistal, buccolingual – used for measurements, wax-ups.

Tooth Elevations – “Mountains” (p.47-55)

• Cusps – pyramidal elevations with cusp tip (molars, premolars, also canine).
• Ridges (non-pyramidal):
  • Triangular ridge – cusp tip → central groove.
  • Transverse ridge – buccal triangular + lingual triangular join (posterior teeth except max. molars).
  • Oblique ridge – special to maxillary molars (ML ↔ DB cusps).
  • Buccal/Labial ridges – cervico-occlusal on facial of posteriors/canine.
  • Marginal ridges – mesial/distal borders (orientation differs anterior vs posterior).
• Cingulum – cervical lingual bulge on all anterior teeth; developmental from single lobe.
• Newly erupted traits:
  • Mamelons – 3 facial incisal tubercles (incisors).
  • Perikymata – horizontal enamel growth lines, denser cervically.

Tooth Depressions – “Valleys” (p.56-59)

• Sulcus – broad V-shaped depression btw buccal & lingual ridges, runs mesiodistally.
• Grooves
  • Central groove – BU↔LI cusp separator.
  • Developmental vs Supplemental (named/unnamed).
• Fossa(e) – shallow basins; posterior teeth have central, mesial, distal fossae; anterior have single lingual fossa; pits often in depth – caries prone.

Foundational Occlusal Anatomy (p.60-65)

• Long Axis – imaginary line through center of root; reference for restorations, orthodontics.
• Crests of Curvature/Height of Contour
  • Greatest bulge facial-lingual; protective role in deflecting food; if reduced → gingival trauma.
  • On mesial contact areas more incisal/occlusal than distal.
• Embrasures – 4 per contact (facial, lingual, occlusal/incisal, gingival). Lingual usually largest; gingival = interproximal space w/ papilla.
• Furcations – root trunk division: bifurcation (2 roots) vs trifurcation (3).
• Lobes – developmental segments; most teeth from 4 lobes, exceptions (5 lobes):
  • Mand. 1st molar (5 cusps) ; Max. 1st molar often cusp of Carabelli ; Mand. 2nd premolar (Y-type) etc.

Clinical/Practical Connections

• Recognizing soft-tissue landmarks critical for injections, pathology screening & esthetic dentistry.
• CEJ & crestal bone relationships guide crown lengthening surgery.
• PDL fiber orientation explains mobility after ortho forces.
• Numbering systems: miscommunication can lead to wrong-tooth extraction—know them all!
• Understanding cuspal/ridge morphology dictates occlusal anatomy in restorations; mis-carved grooves → premature contacts.
• Embrasure & height-of-contour errors in crowns trap food → perio issues.

Ethical & Professional Implications

• Accurate charting (numbers, surfaces) is legal record.
• Respect soft tissues; over-contoured restorations breach biologic width (ethical duty to avoid iatrogenic disease).
• Knowledge of developmental grooves guides fissure-sealant placement – preventive responsibility.

Handy Numerical/Statistical References

• Healthy sulcus depth $\le 3\,\text{mm}$.
• Enamel mineralization $\approx 95\%$, Dentin $\approx 70\%$, Cementum $50–65\%$.
• PDL width $0.1–0.25\,\text{mm}$; thickens under function, thins with non-use.

Study Tips & Next Steps

• Take your own intra-oral photos (“selfie” assignment) and label every landmark to cement terminology.
• Practice drawing tooth outlines, marking line/point angles.
• Use tooth model to palpate ridges, sulci, fossae.
• Quiz with all three numbering systems; convert random teeth quickly.
• Relate each anatomical term to a clinical scenario (e.g., “Where would I place a matrix band? Which embrasure?”).