Oral bio mandibular incisors

• Permanent Mandibular Incisors


  Anterior teeth, first and second tooth from midline, central incisor closest to midline, lateral incisor second from midline

  
• Central and Lateral incisors of the same arch

  Resemble each other more than any Incisor of the other arch
• Major Functions of Incisors

  • Mastication: Biting /cutting/incising
  • Esthetics: Size, shape, color
  • Phonetics: Speech
• Permanent Mandibular Incisors


  • Simplest and least variable
  • Smallest Permanent teeth
  • Central is smaller than lateral (Opposite in maxillary incisors)
  • Resemble each other to a greater extent than maxillary incisors
  • Crowns relatively longer Incisocervically and narrow mesiodistally when compared to maxillary incisors

  
• Permanent Mandibular Central Incisor

  • Adjacent to the midline in the lower arch
  • Mesial contact with each other
  • Distal contact with Lateral incisors
  • Smallest crown of permanent dentition
  • Narrowest mesiodistal dimension
  • Symmetrical, mesial and distal halves identical

  
• Permanent Mandibular Central Incisor

  • Function: Biting, cutting, incising, phonetics, esthetics
• Outline of Permanent Mandibular Central Incisor

  • From Labial/ Lingual aspect: Trapezoidal/rectangular
  • From the Proximal aspects: Triangular
  • From the Incisal aspect: Diamond

  
• Developmental Table for Permanent Mandibular Central Incisors

  1. 3 to 4 months: Initiation of calcification

  2. 4 to 5 years: Completion of Enamel

  3. 6 to 7 years: Eruption

  4. 9 years: Completion of root

  
• Labial Aspect of Permanent Mandibular Central Incisor

  • Trapezoidal outline
  • Imbrication lines: not always present
  • Developmental depressions: Not always present
  • Convexity is greatest in the cervical third
  • Height of Contour: Cervical third
• Mesial margin (outline) of Permanent Mandibular Central Incisor

  • Nearly straight line
  • Sharpest mesioincisal angle
  • Crest of curvature at incisal third near incisal edge at contact area near the mesioincisal angle
• Distal margin (outline) of Permanent Mandibular Central Incisor

  • Also straight line
  • Sharp distoincisal angle almost same like mesial
  • Crest of curvature in incisal third same as mesial
• Incisal outline of Permanent Mandibular Central Incisor

  • Mamelons, when present always three in number
  • After incisal wear, straight, perpendicular to the long axis of the tooth

  
• Cervical margin (CEJ) of Permanent Mandibular Central Incisor


  • Curves evenly towards the root
  • Developmental depressions absent, sometimes very faint depressions present near incisal margin
• Lingual aspect of Permanent Mandibular Central Incisor

  • Mesial, distal and incisal outline: closely resemble the labial aspect
  • Cervical margin: slightly greater depth of curvature apically
  • Surface is generally smooth, less prominences than maxillary incisors
  • Slight concavity or lingual fossa
  • Indistinct marginal ridges
  • No grooves, pits or fissures
  • Cingulum present not very prominent
  • Height of contour: Cingulum/ Cervical third
• Lingual fossa of Permanent Mandibular Central Incisor

  Boundaries: Proximally: Mesial and Distal marginal ridges, Cervically: Cingulum, Incisally: Incisal edge
• Mesial aspect of Permanent Mandibular Central Incisor


  • Outline: Triangular
  • Crown appears offset towards Lingual
  • Incisal edge is usually straight but can be rounded located lingual to the center of the root
  • The profile of incisal edge is has inclination towards labial, opposite to lingual slope of maxillary incisors

  
• Labial outline of Mesial aspect of Permanent Mandibular Central Incisor

  • Straight to slightly Convex
  • Height of contour cervical third

  
• Lingual outline of Mesial aspect of Permanent Mandibular Central Incisor


  • Slight 'S' Shaped curvature, convexity due to cingulum, and concavity due to lingual fossa
  • Height of contour Cingulum

  
• Cervical outline of Mesial aspect of Permanent Mandibular Central Incisor


  • Curves evenly towards incisal
• Incisal outline of Mesial aspect of Permanent Mandibular Central Incisor

  • Incisal edge straight to rounded

  
• Height of contour of Permanent Mandibular Central Incisor

  Located in incisal third at contact area
• Contact area of Permanent Mandibular Central Incisor

  • Located in incisal third near incisal margin
  • Centered labiolingually
  • Roughly ovoid, long Incisocervically
  • Narrow labiolingually
  • Only contact area with mesial-mesial contact at midline
• Distal aspect of Permanent Mandibular Central Incisor

  • Resembles mesial surface except: Cervical margin does not curve far Incisally (less deep)
  • Distal contact area also resembles the mesial side which is unique in mandibular central incisors only

  
• Incisal aspect of Permanent Mandibular Central Incisor

  • Outline: Diamond shape
  • Incisal edge straight
  • Crown is offset towards lingual, more labial side visible
  • Mesial and distal surface symmetrical
  • Tooth is wider labiolingual than mesiodistal
  • Cingulum slight offset to distal otherwise symmetrical

  
• Root of Permanent Mandibular Central Incisor

  • Single and straight
  • Tapers to sharp apex
  • Cross-section of root: Wider mesiodistally, Central portion of mesial or distal surface is concave also called root concavity or longitudinal grooves
  • Near cervical line: Roughly rectangle with rounded corners
  • Mid root section: ovoid
• Variations and anomalies of Permanent Mandibular Central Incisor Great variability in lingual inclination of the labial surface

  • Anomalies are very rare

  • Occasionally bifurcated root is found with labial and lingual branch
• Permanent Mandibular Lateral Incisor

  • Second tooth from the midline in the upper arch
  • Mesial contact with central incisor
  • Distal contact with canines
  • Resemble central incisors but larger in all aspects

  
• Functions of Permanent Mandibular Lateral Incisor

  Supplement central incisor in function. Biting, cutting, incising, phonetics, esthetics
• Developmental Table for Permanent Mandibular Lateral Incisors

  1. 3 to 4 months: Initiation of calcification

  2. 4 to 5 years: Completion of Enamel

  3. 8 years: Eruption

  4. 10 years: Completion of root

  
• Labial Aspect of Permanent Mandibular Lateral Incisor

  • Same as Central incisor with few exceptions: Mesioincisal angle: sharp, Distoincisal angle : rounded, Distal margin is slightly shorter than mesial margin, Contact area on distal surface is more cervical located but still in incisal third
• Lingual aspect of Permanent Mandibular Lateral Incisor

  • Lingual outlines same as labial aspect and its central counterpart except: Cingulum more offset towards distal, Cervical line is also offset distally
• Mesial and distal aspect of Permanent Mandibular Lateral Incisor

  • Two surfaces similar to their counterpart on central incisor with few exceptions: Distal surface is slightly shorter than mesial surface, Cervical line curvature of distal surface is slightly less than its central counter part and mesial surface, Distal contact area more cervically located: Near junction of incisal and middle thirds
• Incisal aspect of Permanent Mandibular Lateral Incisor

  • Incisal edge not straight mesiodistally, Cervical line is curved towards lingual in its distal aspect, Cingulum offset to distal, Give appearance od crown being twisted on its root
• Root of Permanent Mandibular Lateral Incisor

  • Length is greater than central incisor, Root is slightly thicker and wider, Root concavities may be present on mesial and distal surfaces of root, If present distal root concavity is more pronounced, At cervical line and Mid-root section: Ovoid, wider labiolingually than mesiodistally
• Variations and anomalies of Permanent Mandibular Lateral Incisor