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Mandibular central & lateral incisors

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samah khaled

The document summarizes the morphology of mandibular incisors. It describes the features of central and lateral incisors, including their number, size, eruption timing, contact points, and root characteristics. It also discusses variations that can be seen clinically, such as missing teeth, ectopic eruption, peg-shaped teeth, and fusion. Complications like calculus deposition, attrition, and implant challenges are mentioned. The morphology of the pulp cavities and clinical considerations for mandibular incisors are summarized.

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Dental morphology Dr. Samah Khaled
Mandibular incisors
Central incisors Lateral incisors  2 in number, 1 on each side from the midline.  Smallest of all teeth  1st permanent teeth to erupt with 1st molars.  Mesially the 2 centrals contact each other.  Distally they contact the lateral incisors.  2 in number, 1 on each side.  Small but a little larger than centrals.  From mesial they contact central incisor.  From distal they contact the canines.
Chronology • Central incisor Lateral incisor Appearance of enamel organ 5 m.i.u First evidence of calcification 3 - 4 months. Crown completed 4 - 5 years. Eruption 6 – 7 Ys. 7 – 8 Ys. Root completion 9 Ys. 10 Ys.
Lower central incisor
1.Labial aspect 1. Geometric outline:  Trapezoidal with the smallest side cervically. 2. Outlines: A. Mesial & Distal  They taper evenly from the contact areas to the narrow cervix giving the crown fan shaped appearance. B. Incisal  Straight and is at nearly a right angle to the long axis of the tooth  The only incisor where both mesioincisal and distoincisal angles are sharp and at right angles.  Distoincisal angle is barely more rounded than the mesioincisal angle.
1.Labial aspect 3. Contact areas:  Mesial and distal contacts nearly at the same height.  In incisal third near the mesioincisal and distoincisal angles. 4. Surface anatomy:  The labial surface is smooth and more convex.  In the cervical third represented by cervical ridge, and flattens out toward the incisal third.  The developmental grooves may or may not be present. When present, they appear as very faint furrows in newly erupted teeth.
1.Labial aspect 5. Cervical line: Is symmetrically and evenly convex toward the root 6. Root:  Single, Slender and Straight.  The mesial and distal root outlines are straight with the mesial and distal outlines of the crown down to the apical portion.  The root surface is regular and convex and extremely flattened on its mesial and distal surfaces.  The apical third of the root terminates in a small pointed taper, in most cases curving distally.  Sometimes the roots are straight.
2.Lingual aspect:  The crown is narrower on the lingual than on the labial surface (lingual convergence).  The mesial, distal and incisal outlines closely resemble those of the labial aspect and they are regular and symmetrical.  The lingual aspect is shallow:  Less prominent smooth, small and centered cingulum  Less prominent marginal ridges than maxillary incisors.  The incisal ridge is narrow and rounded or worn flat.  Shallow lingual fossa. No lingual pit.  The cervical line is convex toward the root.  The root is slightly narrower on the lingual side than on the labial side.
3. Mesial aspect: 1. The geometric outline Triangular or wedge-shaped but the curvature labially and lingually is less than that found on maxillary incisors. 2.outlines: A. The labial outline: Almost straight, except near cervical third where it is convex (cervical ridge). The labial surface is inclined lingually. B. The lingual outline: ‘S’ shaped. It is convex over the cingulum, in the cervical third. In the middle and incisal thirds the lingual outline is slightly concave. C. The incisal outline: The lingual outline of the narrow incisal ridge is convex (rounded) or flat because of attrition. Incisal ridge center is slightly lingual to the root axis.
3. Mesial aspect: 3. Height of contour (crest of curvature):  Labial→→ Junction of cervical and middle thirds.  Lingual→→ Middle of cervical third. The cervical line: on the mesial and distal surface is marked and convex incisally about one third the length of the crown. 3. The contact area: located half way from labial to lingual and in the incisal third, very close to the incisal edge. It has an ovoid shape. Root: The labial and lingual outlines of the root are nearly straight from the cervical line to the middle third; then tapers to the rounded or pointed apex. Which is with long axis. Flat surface with a broad and deep longitudinal developmental depression, that is deeper at the junction of the middle and apical thirds.
Mandibular central & lateral incisors
 Distal surface is very similar to the mesial surface.  The cervical line is less curved about 1mm less than on the mesial surface.  The developmental depression on the distal surface of the root is more marked, with a deeper and more well-defined developmental groove at its center than the one on the mesial surface. 4. Distal aspect:
 The geometric outline: Roughly diamond-shaped.  The crown tapers lingually, therefore, the labial outline is wider than the lingual outline.  The labiolingual diameter > mesiodistal diameter  The labial surface of the crown is slightly convex at incisal third.  The lingual surface of the crown is slightly concave at the incisal third with centered, smooth, and convex cingulum.  The incisal ridge (edge) is straight and at right angles to a line passing labiolingually.  There is bilateral symmetry (mesial and distal), which is a ch.ch feature of lower central incisor.  Newly erupted teeth show mamelons which wear off upon mastication. 5. Incisal aspect
 Since this tooth supplements the mandibular central incisor so its design is similar.  It is a little wider mesiodistal than the mandibular central incisor.  Crown is slightly longer from the incisal edge to the cervical line.  The incisal edge follows the mandibular arch, giving the crown a slightly twisted appearance on its root.  Lateral incisor has slightly longer, thicker and wider root in all dimensions.  The root appears very narrow mesiodistally, and tapers gradually from cervical line toward pointed apex which may slightly to the distal. Lateral Incisor
 larger and wider than central mesiodistally. The facial surface is less symmetrical than the facial surface of the mandibular central incisor.  The crown is tilted distally on the root, giving the impression that the tooth has been bent at the cervix.  This makes the distal outline of the crown shorter than the mesial outline.  The mesial C.A near the incisal edge and the distal just cervical to the level of the mesial one.  The incisal edge slopes cervical downward (distal sloping) from the mesioincisal angle toward the distoincisal angle which is rounded. Labial aspect
 The cingulum is quite large but blends in smoothly with the rest of the surface so the cingulum and marginal ridges more prominent on lateral than central.  The cingulum is more offset to the distal, and as a result, the curvature of the cervical line is also offset distally.  The concavity in the lingual aspect is slightly more when compared to mandibular central incisor. Lingual aspect
 Like the central, the crown presents a triangular outline.  The incisal edge is on or lingual to the midline from mesial.  the distolingual twist of the incisal ridge places the distal portion at the ridge somewhat more lingual than on the mesial.  The distal surface is shorter than the mesial.  The cervical line curvature in both mesially and distally is slightly less than the central incisors.  The distal contact area is more cervically located than on the mesial. Mesial & Distal aspects:
 crown is broader labiolingually than mesiodistally.  It not bilaterally symmetrical.  The incisal edge is not straight and it curves toward the lingual in its distal portion (distolingual twist) giving the crown the appearance of being slightly twisted on its root.  This twist corresponds to the curvature of the mandibular dental arch.  The distal half of the incisal edge is bent lingually, so that the distoincisal angle is more lingual in position than the mesioincisal angle.  The cingulum is slightly off-center to the distal. Incisal aspect
Pulp cavities of mandibular incisors:  Mostly they have one root with single root canal.  Mesiodistal section  Narrow with widest part incisally then taper till ending in apical foramen  pulp horns are prominent at first then decrease in height with continuous deposition of dentin.  Labiolingual section:  Pointed incisally, becomes widest at mid cingulum level.  The canal is widest cervically then tapers till a narrow foramen.  Cervical cross section:  Rounded, oval or elliptical.  Midroot cross section:  Ovoid and constricted.
 There may be a variation:  It is rare to have bifurcated root.  The root canal divides into 2 canals that then join to open in 1 apical foramen.
Clinical considerations What can we see in the dental clinic? 1. Congenitally missed teeth. 2. Ectopic eruption. 3. Peg shaped teeth. 4. Talon cusp. 5. Fusion or twining. 6. Calculus deposition. 7. Attrition. 8. Challenge in implants
Missing lateral
Ectopic eruption (lingual to deciduous ones) Lateral distal to canine
Peg shaped
Talon cusp Additional cusp located on buccal or lingual surface of anterior teeth , composed of enamel dentine and a pulp horn.
Calculus deposition Periodontal pocket then Periodontitis then gingival recession then tooth loss
Fusion 2 enamel organs fused together Attrition of incisal surface
 Weakest and smallest teeth in the mouth  There’s usually not enough space for a regular dental implant due to mesiodistal restrictions; roots on either side don’t allow enough space for implant placement.  There are buccolingual restrictions as well, since the ridge frequently atrophies in the anterior area of mandible.  Recently mini implants are used .
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Mandibular central & lateral incisors

  • 3. Central incisors Lateral incisors  2 in number, 1 on each side from the midline.  Smallest of all teeth  1st permanent teeth to erupt with 1st molars.  Mesially the 2 centrals contact each other.  Distally they contact the lateral incisors.  2 in number, 1 on each side.  Small but a little larger than centrals.  From mesial they contact central incisor.  From distal they contact the canines.
  • 4. Chronology • Central incisor Lateral incisor Appearance of enamel organ 5 m.i.u First evidence of calcification 3 - 4 months. Crown completed 4 - 5 years. Eruption 6 – 7 Ys. 7 – 8 Ys. Root completion 9 Ys. 10 Ys.
  • 6. 1.Labial aspect 1. Geometric outline:  Trapezoidal with the smallest side cervically. 2. Outlines: A. Mesial & Distal  They taper evenly from the contact areas to the narrow cervix giving the crown fan shaped appearance. B. Incisal  Straight and is at nearly a right angle to the long axis of the tooth  The only incisor where both mesioincisal and distoincisal angles are sharp and at right angles.  Distoincisal angle is barely more rounded than the mesioincisal angle.
  • 7. 1.Labial aspect 3. Contact areas:  Mesial and distal contacts nearly at the same height.  In incisal third near the mesioincisal and distoincisal angles. 4. Surface anatomy:  The labial surface is smooth and more convex.  In the cervical third represented by cervical ridge, and flattens out toward the incisal third.  The developmental grooves may or may not be present. When present, they appear as very faint furrows in newly erupted teeth.
  • 8. 1.Labial aspect 5. Cervical line: Is symmetrically and evenly convex toward the root 6. Root:  Single, Slender and Straight.  The mesial and distal root outlines are straight with the mesial and distal outlines of the crown down to the apical portion.  The root surface is regular and convex and extremely flattened on its mesial and distal surfaces.  The apical third of the root terminates in a small pointed taper, in most cases curving distally.  Sometimes the roots are straight.
  • 9. 2.Lingual aspect:  The crown is narrower on the lingual than on the labial surface (lingual convergence).  The mesial, distal and incisal outlines closely resemble those of the labial aspect and they are regular and symmetrical.  The lingual aspect is shallow:  Less prominent smooth, small and centered cingulum  Less prominent marginal ridges than maxillary incisors.  The incisal ridge is narrow and rounded or worn flat.  Shallow lingual fossa. No lingual pit.  The cervical line is convex toward the root.  The root is slightly narrower on the lingual side than on the labial side.
  • 10. 3. Mesial aspect: 1. The geometric outline Triangular or wedge-shaped but the curvature labially and lingually is less than that found on maxillary incisors. 2.outlines: A. The labial outline: Almost straight, except near cervical third where it is convex (cervical ridge). The labial surface is inclined lingually. B. The lingual outline: ‘S’ shaped. It is convex over the cingulum, in the cervical third. In the middle and incisal thirds the lingual outline is slightly concave. C. The incisal outline: The lingual outline of the narrow incisal ridge is convex (rounded) or flat because of attrition. Incisal ridge center is slightly lingual to the root axis.
  • 11. 3. Mesial aspect: 3. Height of contour (crest of curvature):  Labial→→ Junction of cervical and middle thirds.  Lingual→→ Middle of cervical third. The cervical line: on the mesial and distal surface is marked and convex incisally about one third the length of the crown. 3. The contact area: located half way from labial to lingual and in the incisal third, very close to the incisal edge. It has an ovoid shape. Root: The labial and lingual outlines of the root are nearly straight from the cervical line to the middle third; then tapers to the rounded or pointed apex. Which is with long axis. Flat surface with a broad and deep longitudinal developmental depression, that is deeper at the junction of the middle and apical thirds.
  • 13.  Distal surface is very similar to the mesial surface.  The cervical line is less curved about 1mm less than on the mesial surface.  The developmental depression on the distal surface of the root is more marked, with a deeper and more well-defined developmental groove at its center than the one on the mesial surface. 4. Distal aspect:
  • 14.  The geometric outline: Roughly diamond-shaped.  The crown tapers lingually, therefore, the labial outline is wider than the lingual outline.  The labiolingual diameter > mesiodistal diameter  The labial surface of the crown is slightly convex at incisal third.  The lingual surface of the crown is slightly concave at the incisal third with centered, smooth, and convex cingulum.  The incisal ridge (edge) is straight and at right angles to a line passing labiolingually.  There is bilateral symmetry (mesial and distal), which is a ch.ch feature of lower central incisor.  Newly erupted teeth show mamelons which wear off upon mastication. 5. Incisal aspect
  • 15.  Since this tooth supplements the mandibular central incisor so its design is similar.  It is a little wider mesiodistal than the mandibular central incisor.  Crown is slightly longer from the incisal edge to the cervical line.  The incisal edge follows the mandibular arch, giving the crown a slightly twisted appearance on its root.  Lateral incisor has slightly longer, thicker and wider root in all dimensions.  The root appears very narrow mesiodistally, and tapers gradually from cervical line toward pointed apex which may slightly to the distal. Lateral Incisor
  • 16.  larger and wider than central mesiodistally. The facial surface is less symmetrical than the facial surface of the mandibular central incisor.  The crown is tilted distally on the root, giving the impression that the tooth has been bent at the cervix.  This makes the distal outline of the crown shorter than the mesial outline.  The mesial C.A near the incisal edge and the distal just cervical to the level of the mesial one.  The incisal edge slopes cervical downward (distal sloping) from the mesioincisal angle toward the distoincisal angle which is rounded. Labial aspect
  • 17.  The cingulum is quite large but blends in smoothly with the rest of the surface so the cingulum and marginal ridges more prominent on lateral than central.  The cingulum is more offset to the distal, and as a result, the curvature of the cervical line is also offset distally.  The concavity in the lingual aspect is slightly more when compared to mandibular central incisor. Lingual aspect
  • 18.  Like the central, the crown presents a triangular outline.  The incisal edge is on or lingual to the midline from mesial.  the distolingual twist of the incisal ridge places the distal portion at the ridge somewhat more lingual than on the mesial.  The distal surface is shorter than the mesial.  The cervical line curvature in both mesially and distally is slightly less than the central incisors.  The distal contact area is more cervically located than on the mesial. Mesial & Distal aspects:
  • 19.  crown is broader labiolingually than mesiodistally.  It not bilaterally symmetrical.  The incisal edge is not straight and it curves toward the lingual in its distal portion (distolingual twist) giving the crown the appearance of being slightly twisted on its root.  This twist corresponds to the curvature of the mandibular dental arch.  The distal half of the incisal edge is bent lingually, so that the distoincisal angle is more lingual in position than the mesioincisal angle.  The cingulum is slightly off-center to the distal. Incisal aspect
  • 20. Pulp cavities of mandibular incisors:  Mostly they have one root with single root canal.  Mesiodistal section  Narrow with widest part incisally then taper till ending in apical foramen  pulp horns are prominent at first then decrease in height with continuous deposition of dentin.  Labiolingual section:  Pointed incisally, becomes widest at mid cingulum level.  The canal is widest cervically then tapers till a narrow foramen.  Cervical cross section:  Rounded, oval or elliptical.  Midroot cross section:  Ovoid and constricted.
  • 21.  There may be a variation:  It is rare to have bifurcated root.  The root canal divides into 2 canals that then join to open in 1 apical foramen.
  • 22. Clinical considerations What can we see in the dental clinic? 1. Congenitally missed teeth. 2. Ectopic eruption. 3. Peg shaped teeth. 4. Talon cusp. 5. Fusion or twining. 6. Calculus deposition. 7. Attrition. 8. Challenge in implants
  • 24. Ectopic eruption (lingual to deciduous ones) Lateral distal to canine
  • 26. Talon cusp Additional cusp located on buccal or lingual surface of anterior teeth , composed of enamel dentine and a pulp horn.
  • 27. Calculus deposition Periodontal pocket then Periodontitis then gingival recession then tooth loss
  • 28. Fusion 2 enamel organs fused together Attrition of incisal surface
  • 29.  Weakest and smallest teeth in the mouth  There’s usually not enough space for a regular dental implant due to mesiodistal restrictions; roots on either side don’t allow enough space for implant placement.  There are buccolingual restrictions as well, since the ridge frequently atrophies in the anterior area of mandible.  Recently mini implants are used .