Permanent Dentition Tooth Morphology

Permanent Dentition Tooth Morphology

• Dental Notation System:
  • 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 (upper right quadrant/upper left quadrant)
  • 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 (lower right quadrant/lower left quadrant)
• Tooth Anatomy:
  • Cusp: the pointed projection on the chewing surface of a tooth
  • Cusp Tip (ct): the highest point of a cusp
  • Mesial Slope (ms): the smooth incline of the cusp towards the front of the mouth
  • Distal Slope (ds): the smooth incline of the cusp towards the back of the mouth
  • Cusp Incline: the angled side of the cusp
  • Developmental Groove: a prominent groove on the tooth surface that forms during tooth development
  • Fossa: pits or hollows on the tooth surface, sometimes associated with grooves or enclosed by ridges
  • Pulp Chamber: the central part of the tooth containing the pulp, located within the crown
  • Root Canal: extensions of the pulp chamber within the roots of the tooth
  • Pulp Horns: extensions of the pulp chamber that extend under the cusps

Upper Permanent Incisors and Canines

• Upper Central Incisors:
  • Chronology: initial calcification 3-4 months after birth, crown completion 4-5 years, eruption 7-8 years, root completion 10 years
  • Labial View: large, smooth, slightly convex crown, incisal edges sharp, mesial & distal incisal angles rounded, mamelons present in newly erupted teeth
  • Palatal View: concave surface, mesial & distal marginal ridges, cingulum (convex bulge) with a cingulum pit, crown enamel margin undulates
  • Mesial View: cervical undulation, single, tapering root, one root canal with two pulp horns
• Upper Lateral Incisors:
  • Chronology: initial calcification 10-12 months after birth, crown completion 4-5 years, eruption 8-9 years, root completion 11 years
  • Labial View: smaller than central incisor, narrower cervically, rounded distal-incisal angle
  • Palatal View: pronounced marginal ridges, large cingulum with a more pronounced cingulum pit
  • Mesial View: cervical undulation, one tapering root, one root canal with two pulp horns
• Upper Canine:
  • Chronology: initial calcification 4-5 months after birth, crown completion 6-7 years, eruption 11-12 years, root completion 13-15 years
  • Labial View: single cusp, convex surface, distal slope longer than mesial slope, distal surface bulbous
  • Palatal View: concave surface, pronounced marginal ridges, large cingulum, mesial & distal fossae,
  • Distal View: cervical undulation, one long tapering root, one root canal with no pulp horns, prominent distal root groove
• Comparison of 11, 12, 13 (Labial & Palatal Views):
  • Central Incisor: larger, more prominent incisal edges, smaller cingulum
  • Lateral Incisor: smaller, less prominent incisal edges, larger cingulum

Upper First Molar

• Palatal View: cusp of Carabelli (additional cusp on mesial cusp), central groove sometimes divided into two, palatal groove, palatal wall more curved than buccal wall
• Buccal View: equilateral crown, mesio-distal dimension similar to bucco-palatal, oblique ridge extending from disto-buccal to mesio-palatal cusps
• Occlusal View: oblique ridge divides the occlusal surface into two, distinct groove patterns, deep groove from occlusal to palatal surface separating the disto-palatal cusp
• Root Structure: one large palatal root, one mesio-buccal root, one mesio-lingual root

Lower Incisors and Canines

• Lower Central Incisor: resembles upper central incisor. The key difference is that the labial surface is not convex, and the incisal edges are not as sharp
• Lower Lateral Incisor: similar to upper lateral incisors
• Lower Canine: similar to upper canine. Key differences: mesial & distal cusp inclines are shorter

Lower Molars

• Lower First Molar:
  • Buccal View: mesio-buccal cusp larger than disto-buccal cusp, two developmental grooves, mesial groove deeper and longer than distal groove
  • Lingual View: mesio-lingual cusp larger than disto-lingual cusp, central groove zig-zagging between cusps, small lingual groove, overall oval shape
  • Mesial View: buccal wall curved, lingual wall straight, wide, grooved mesial root
  • Distal View: distal cusp visible, short marginal ridge to distal cusp, narrow distal root with no groove
• Lower Second Molar:
  • Buccal View: 4 cusps (mesio-buccal, disto-buccal, mesio-lingual, disto-lingual), mesio-buccal cusp higher than disto-buccal
  • Lingual View: mesio-lingual cusp higher than disto-lingual cusp, cusps interdigitate, overall rectangular shape, cross-shaped groove pattern
  • Mesial View: wider mesially than distally, two roots (mesial & distal), mesial root wider and often grooved, buccal surface curved, lingual surface straight
  • Distal View: distal root narrower, 3-4 root canals, buccal and lingual grooves
• Lower Third Molar:
  • Buccal View: variable size and form, 4, 5, or 6 cusps, roots show marked distal inclination, often fused
  • Mesial View: curved, convex buccal wall, bulbous crown, broader mesial root
  • Distal View: narrower distal root

Comparison of Lower Molars

• Lower First Molar: mesio-buccal cusp larger than disto-buccal cusp, two developmental grooves buccally, overall crown shape is oval
• Lower Second Molar: similar cusp configurations, overall crown shape is rectangular

Summary of Key Points

• Permanent Dentition: 32 teeth in adults, 8 in each quadrant, designated by a numerical system
• Tooth Surface Features: Cusps, cusp inclines, developmental grooves, fossae
• Pulp Anatomy: pulp chamber, root canals, pulp horns
• Upper Incisor Characteristics: two central incisors, two lateral incisors
• Upper Canine Characteristics: one canine per side
• Upper Molar Characteristics: two molars (first and second)
• Lower Incisor Characteristics: two central incisors, two lateral incisors
• Lower Canine Characteristics: one canine per side
• Lower Molar Characteristics: three molars (first, second, and third)
• Third Molars (Wisdom Teeth): variable eruption and development

Permanent Tooth Anatomy

• Incisors:
  • Upper Central Incisors (11, 21):
    • Labial: Smooth, sharp mesio-incisal angles, rounded disto-incisal angles. Mamelons (bumps) present on newly erupted teeth.
    • Palatal: Concave with marginal ridges, a central cingulum (raised area), and sometimes a cingulum pit.
  • Upper Lateral Incisors (12, 22):
    • Similar to central incisors, but smaller and more symmetrical.
  • Lower Central Incisors (31, 41):
    • Smaller than upper, more symmetrical, and narrower.
  • Lower Lateral Incisors (32, 42):
    • Similar to lower central incisors but larger, more rectangular.
• Canines:
  • Upper Canines (13, 23):
    • Single cusp with a longer distal slope.
    • Labial: Convex.
    • Palatal: Prominent marginal ridges and fossae.
  • Lower Canines (33, 43):
    • Smaller, less pronounced than their upper counterparts, but sharper cusp tip.
• Premolars:
  • Upper First Premolars (14, 24):
    • Two cusps (buccal larger than palatal), usually two roots.
    • Mesial slope of buccal cusp is longer.
    • Developmental grooves on occlusal surface.
  • Upper Second Premolars (15, 25):
    • Two cusps (buccal larger than lingual), often a single root.
    • Occlusal surface has a mesial and distal groove and marginal ridges.
  • Lower First Premolars (34, 44):
    • Usually two cusps, a single root, and a central developmental groove.
  • Lower Second Premolars (35, 45):
    • Three cusps, one root, and one prominent central developmental groove.
• Molars:
  • Upper First Molars (16, 26):
    • Four main cusps in a rhomboidal shape.
    • Mesio-palatal cusp is largest, disto-palatal is smallest.
    • Often features an extra fifth cusp (Cusp of Carabelli).
  • Upper Second Molars (17, 27):
    • Four main cusps, generally smaller than first molars.
    • Usually a fifth cusp (Cusp of Carabelli).
  • Lower First Molars (36, 46):
    • Five cusps (three buccal, two lingual).
    • Mesio-buccal cusp is the largest.
    • Two roots.
  • Lower Second Molars (37, 47):
    • Four main cusps.
    • Usually two roots.
  • Third Molars (wisdom teeth):
    • Vary in shape and size, with 3 or 4 cusps.
    • Erupt between 17-21 years old.
• Tooth Surfaces:
  • Labial/Buccal: Surface facing lips/cheeks.
  • Lingual/Palatal: Surface facing tongue (lingual) or palate (palatal).
  • Mesial: Surface closest to the midline.
  • Distal: Surface farthest from the midline.
  • Developmental Grooves: Found on occlusal surfaces, divide cusps.
  • Fossae: Small depressions, often at the intersection of grooves.

Clinical Applications of Permanent Tooth Anatomy

• Diagnosing Caries: Understanding tooth anatomy helps identify common caries locations (pit and fissures, cingulum pits).
• Eruption Sequences: Recognizing normal eruption patterns helps identify developmental issues.
• Restorative Treatment: Accurate restoration of occlusal anatomy is crucial.
• Orthodontics: Knowing tooth size and shape is critical for proper orthodontic treatment planning.
• Eruption Dates:
  • Each tooth has specific dates for initial calcification, crown completion, eruption, and root completion.
  • This knowledge helps anticipate normal development and identify potential issues.