Dental Anatomy – Oral Cavity & Tooth Landmarks (Week 1)

Purpose of Dental-Anatomy Knowledge

• Hygienists must perform thorough extra- & intra-oral exams.

  • Findings are used to design a client-centred care-plan.

• Competencies to master:

  • Identification of all oral landmarks.

  • Complete tooth nomenclature (surfaces, divisions, lobes, grooves, ridges, pits, etc.).

  • Understanding curvatures, proximal contacts, embrasures, col areas & their clinical impact.

  • Evaluation of the effects of abnormal curvatures/embrasures on periodontal health.

Oral Cavity – General Overview

• Dual function: beginning of digestive tract & shared pathway with respiratory system.

• Extends from lips/cheeks → palatine tonsils → oropharynx.

• Two main divisions:

  1. Vestibule – space between lips/cheeks & teeth/alveolar ridges.

  2. Oral cavity proper – interior to alveolar ridges & back to tonsillar pillars.

Vestibule Specifics

• Boundaries: lips (anterior), cheeks (lateral); superior ridge of bone (posterior-superior); zygomatic-alveolar crest (anterior-superior).

• Contains key soft-tissue structures (frenula, mucosa variations).

Lips

• Vermilion border: junction of dry skin & wet mucosa.

• Vermilion zone: darker, full central portion.

• Philtrum: midline depression from nose → upper lip.

• Labial commissures: corners where upper & lower lips meet.

Labial/Buccal Frenum

• Connective-tissue folds (non-muscular) anchoring lips/cheeks to alveolar mucosa.

• Excessive “frenum-pull” can create diastemas or gingival recession.

• Frenectomy indicated if function or periodontal health is compromised.

Mucosa Types & Junctions

• Alveolar mucosa: reddish, loose, easily movable; high vascularity.

• Attached gingiva: keratinized, bound to bone; paler.

• Mucogingival junction (MGJ): scalloped line dividing the two.

• Muco-buccal fold: depth of vestibule where mucosa reflects onto alveolar process.

Fordyce Granules

• Misplaced sebaceous glands embedded in mucosa.

• Appear as yellowish papules on labial/buccal mucosa; benign.

Exostoses

• Localized, hereditary bony protuberances on cortical plates of maxilla/mandible.

• May be single/multiple, uni- or bilateral; typically canine → molar region.

Oral Cavity Proper – Maxilla/Palate Region

Hard Palate

• Composition: palatine processes of maxilla + horizontal plates of palatine bones.

• Covered by keratinized epithelium; may be vaulted (high U-shape), flat, wide, or narrow.

• Palatine rugae: transverse epithelial ridges for food manipulation & speech.

• Median palatine raphe: midline ridge from incisive papilla → posterior border.

• Incisive papilla: single midline bulge posterior to central incisors; covers incisive foramen/foramina of Scarpa.

• Greater palatine foramina: lingual to maxillary 2ᵉˢᵗ & 3ʳᵈ molars.

• Fovea palatinae: twin depressions flanking posterior nasal spine.

Soft Palate & Fauces

• Posterior, non-keratinized, contains adipose & minor salivary glands.

• Muscular submucosa critical for speech & swallowing; elevates to close nasopharynx.

• Anterior/Posterior faucial pillars (palatoglossal/palatopharyngeal folds): muscular arches forming lateral borders of fauces.

• Palatine tonsils: lymphoid masses between pillars – immune defense.

• Uvula: midline muscular extension from soft palate.

Distal Palatal Landmarks

• Maxillary tuberosity: bony bulge distal to last maxillary molar.

• Retromolar pad: dense tissue distal to mandibular 3ʳᵈ molars.

• Palatal torus (torus palatinus): benign midline excess bone projection.

Tongue & Floor of Mouth

• Tongue musculature: intrinsic & extrinsic muscles for speech, mastication, deglutition.

• Division: anterior \tfrac{2}{3} (body) vs posterior \tfrac{1}{3} (pharyngeal).

  • Surfaces: dorsal (top), ventral (underside), lateral borders.

• Lingual frenum: anchors tongue base to floor.

  • Ankyloglossia (“tongue-tie”): short frenum attached near tip → restricted motion.

• Sublingual caruncle: small papilla at frenum base; ducts for submandibular & sublingual glands.

• Floor mucosa = thinnest oral epithelium → rapid absorption (clinical drug delivery).

Mandibular Tori & Coronoid Process

• Mandibular tori: bilateral lingual bony outgrowths in premolar region; radiographically visible.

• Coronoid process: anterior mandibular ramus projection; enters vestibule on wide opening.

  • Clinical considerations: may impinge on film holders, trays; adjust radiographic angulation & impression technique.

Tooth Landmarks (Part B)

Functional Roles of Teeth

• Chewing (mastication) → initiates digestion.

• Protect oral cavity from injury.

• Speech/phonetics.

• Esthetics – facial support & smile appearance.

Macro-Structure

• Crown: part covered by enamel.

  • Anatomic crown: entire enamel-covered region, erupted or not.

  • Clinical crown: portion visible in mouth (may increase with recession).

• Root: portion covered by cementum; may be

  • Single, bifurcated \rightarrow 2 roots, or trifurcated \rightarrow 3 roots.

  • Apex: terminal tip where neurovascular bundle enters.

• Cemento-enamel junction (CEJ): boundary joining crown & root.

Root Supporting Apparatus

• Periodontal ligament (PDL): collagen fibers inserting into cementum & alveolar bone (tooth socket = alveolus) to suspend tooth.

Tooth Tissues

1. Enamel

   • 96\% inorganic hydroxyapatite; 4\% organic + water.

   • Hardest body tissue; smooth & self-cleansing; protects against mild acids/bacteria.

2. Dentin

   • Main bulk; in crown & root.

   • 70\% inorganic, 30\% organic/water; second hardest.

3. Cementum

   • 65\% inorganic, 23\% organic, 12\% water.

   • Rough surface for PDL attachment; thinnest at CEJ, thicker apically.

4. Pulp (soft tissue)

   • Vascular, lymphatic, connective & nerve tissue + odontoblasts.

   • Functions: nutrition, innervation (sensation), dentin formation/repair, immune defense.

Pulp Anatomy Terms

• Pulp cavity: entire internal space.

• Pulp chamber: section in crown.

• Pulp canal (root canal): canal within each root to apex.

• Pulp horns: pointed projections following cuspal shape.

Nomenclature of Tooth Surfaces

• Facial – faces lips/cheeks.

  • Labial (anterior) vs Buccal (posterior).

• Lingual – faces tongue (mandibular) / Palatal (maxillary).

• Proximal surfaces:

  • Mesial: toward midline.

  • Distal: away from midline.

• Occlusal (posterior) / Incisal (anterior) – chewing edges.

Crown & Root Division Thirds

• Horizontally (crown): Incisal/Occlusal – Middle – Cervical.

• Vertically (crown): Facial – Middle – Lingual thirds.

• Root: Cervical – Middle – Apical thirds.

Line Angles & Point Angles

• Line angle: junction of two surfaces (e.g., mesiolabial, distolingual).

  • Anterior teeth have 6 named line angles; posterior teeth have 8.

• Point angle: junction of three surfaces (e.g., mesiobucco-occlusal).

  • Each posterior tooth exhibits 4$$ point angles.

Morphologic Landmarks

• Cusps: major pointed eminences.

• Cingulum: cervical bulge on lingual of anterior teeth.

• Tubercles: small extra enamel projections.

• Fossa(e): concave depressions (e.g., lingual fossa on incisors, central fossa on molars).

• Developmental grooves: primary linear junctions of lobes.

• Supplemental grooves: less distinct, shallow branches.

• Pits: pinpoint depressions at groove junctions or fossa centers.

• Fissures: deep clefts due to incomplete lobe fusion.

Ridges

1. Marginal ridge – mesial/distal elevations on occlusal (posterior) or lingual (anterior) surfaces.

2. Triangular ridge – cusp tip → central groove (posterior teeth).

3. Transverse ridge – union of two triangular ridges running bucco-lingually.

4. Oblique ridge – union of triangular ridges running diagonally (notably maxillary molars).

Curvatures & Contours – Functional Significance

• Prevent disease by deflecting food & minimizing stagnation.

• Shield gingiva & PDL from trauma; disperse occlusal forces.

• Aid self-cleansing via tongue, cheeks, saliva flow.

• Evolutionary adaptation involves:

  • Optimal size/location of proximal contacts & embrasures.

  • Adequate CEJ curvature.

  • Proper facial/lingual contours for plaque control.

Proximal Contacts

• Located at widest mesial/distal crown areas (anterior contacts more incisal).

• Functions:

  • Prevent food impaction & bacterial buildup.

  • Stabilize arch by sharing interproximal bone.

  • Resist displacement from occlusal/traumatic forces.

• Loss via caries/periodontal disease affects neighboring teeth’s health.

Interproximal Spaces (Triangular Spaces)

• Bounded by proximal surfaces + alveolar bone; normally filled by interdental papilla (gingiva).

• Provide vascular supply & bony support.

• Cervical embrasure arises if papilla/bone lost (periodontal disease, orthodontic movement) → plaque & food accumulation risk.

Embrasures (Spillways)

• Openings incisal/occlusal to contact areas.

• Four per contact: facial, lingual, occlusal/incisal, cervical (when papilla missing).

• Benefits:

  • Direct food away from contacts → minimize impaction.

  • Dissipate occlusal forces.

  • Facilitate self-cleansing via salivary flushing & muscular action.

  • Provide gentle gingival stimulation without trauma.

Self-Cleansing Mechanisms

• Enamel smoothness & convex crown shape.

• Cusp action (e.g., canine pierces; premolars grind).

• Muscular movement (tongue, cheeks) moves bolus over molars then posteriorly.

• Deep pits/fissures that exceed natural cleaning may warrant sealants.

Clinical Notes & Pathology Alerts

• Frenum pull → recession, spacing; evaluate for frenectomy.

• Ankyloglossia → speech & feeding issues; may need surgical release.

• Exostoses / Tori → limit prosthesis seating, complicate radiographs; benign unless ulcerated.

• Coronoid process interference → adapt projection angles or tray size.

• Soft-palate anatomy impacts airway management & reflex gagging.

• Abnormal curvatures/contacts predispose to caries & periodontal breakdown.

Next Steps / Preparation for Week 2

• Review Week 1 Q&A sheet.

• Download & explore “Bone Box” application.

• Master oral-cavity terminology list provided.

• Continuous self-check: locate every landmark intra-orally & on radiographs/models.