Podcast
Questions and Answers
What characteristic distinguishes the incisor crown in terms of its dimension?
What characteristic distinguishes the incisor crown in terms of its dimension?
- Labiolingual dimension is equal to mesiodistal
- Labiolingual dimension is less than mesiodistal
- Labiolingual dimension is greater than mesiodistal (correct)
- Labiolingual dimension is inconsistent with mesiodistal
How does the incisal edge relate to the labiolingual bisecting line in incisors?
How does the incisal edge relate to the labiolingual bisecting line in incisors?
- It shows no correlation with the bisecting line
- It is parallel to the labiolingual bisecting line
- It is twisted from a right angle (correct)
- It is angled at 45 degrees
What is a common developmental anomaly seen in incisors?
What is a common developmental anomaly seen in incisors?
- Talon's cusp (correct)
- Lingual fossa
- Creased enamel
- Bifurcation of the root
What is true about the apical third of the incisor root?
What is true about the apical third of the incisor root?
Which feature assists in distinguishing right from left incisors?
Which feature assists in distinguishing right from left incisors?
What indicates the central incisor's developmental consistency?
What indicates the central incisor's developmental consistency?
What happens to the root structure as it tapers apically?
What happens to the root structure as it tapers apically?
What does the lingual fossa indicate about an incisor?
What does the lingual fossa indicate about an incisor?
What distinct feature characterizes the labial aspect of permanent mandibular central incisors?
What distinct feature characterizes the labial aspect of permanent mandibular central incisors?
Which statement accurately describes the morphology of the permanent mandibular lateral incisors?
Which statement accurately describes the morphology of the permanent mandibular lateral incisors?
What is the significance of the incisal ridge positioning in relation to the long axis of the root for mandibular incisors?
What is the significance of the incisal ridge positioning in relation to the long axis of the root for mandibular incisors?
Which of the following correctly describes the root morphology of the permanent mandibular central incisors?
Which of the following correctly describes the root morphology of the permanent mandibular central incisors?
Which aspect of the permanent mandibular lateral incisor is characterized by a well-developed marginal ridge?
Which aspect of the permanent mandibular lateral incisor is characterized by a well-developed marginal ridge?
How does the root of the permanent mandibular lateral incisors compare to that of the central incisors in terms of shape?
How does the root of the permanent mandibular lateral incisors compare to that of the central incisors in terms of shape?
Which characteristic is unique to the incisal aspect of permanent mandibular incisors?
Which characteristic is unique to the incisal aspect of permanent mandibular incisors?
What is the typical feature of the cervical line in the distal aspect of permanent mandibular central incisors?
What is the typical feature of the cervical line in the distal aspect of permanent mandibular central incisors?
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Study Notes
Arch Traits
- Mandibular incisors are narrower mesiodistally
- Central and lateral incisors are nearly equal in size
- Roots are smaller mesiodistally and oblong in cross-section
Permanent Mandibular Central Incisor
Labial Aspect
- Narrowest mesiodistally of all incisors
- Bilaterally symmetrical
- Smooth surface, convex in cervical third, flattened in incisal third
- Three mamelons
- Mesioincisal and distoincisal angles are at 90 degrees
- Both height of contour are within the incisal third
- Mesial and distal outlines are almost straight lines
- CEJ is convex cervically
- Root is narrow and conical
Distal Aspect
- Vertical root axis
- Trapezoidal facial form with shortest side towards the cervix
- Cervical line curved apically
Mesial Aspect
- Sharp distoincisal angles
- Sharp mesioincisal angle
- Crown bilaterally symmetrical
- Mesial and distal outlines taper evenly towards the cervix
- Single conical root
Lingual Aspect
- Shallow fossa, less prominent cingulum, and marginal ridges
- Lingual convergence of crown
Mesial Aspect
- Labial HOC within the cervical third
- From HOC towards the incisal edge, the labial outline is straight
Distal Aspect
- CEJ is 1 mm less curved
Lingual Aspect
- Incisal ridge lingual to the long axis of the root
- Concavoconvex lingual outline
- Height of lingual contour at the cervical third on the cingulum
- Cervical line curves incisally
Permanent Mandibular Lateral Incisor
Labial Surface
- Slightly wider than the central incisor
- Lack of bilateral symmetry
- MI angle is sharp, DI angle rounded with the distal HOC more cervically situated
- Distoincisal angle rounded
- Mesiodistal dimension is 1 mm greater than the central incisor
- Incisal ridge slopes downwards in a distal direction
- Mesial outline longer than distal outline
- Crown bilaterally asymmetrical with the distal side slightly larger
- Conical root
- Root apex
Mesial Aspect
- Well-developed marginal ridge
Distal Aspect
- Narrower lingual surface due to lingual convergence of the crown
- Shallow lingual fossa without grooves
- Cingulum
- Lingual convergence of the root
Lingual Aspect
- Triangular proximal form
- Incisal ridge lingual to the root axis line
- Mesial contact area at the incisal third nearer to the incisal ridge
- Concavoconvex lingual outline
- Height of lingual contour at the cervical third on the cingulum
- Labiolingually broad root
- Distal contact area also within the incisal third but cervically placed than the mesial contact area
- Cervical line on distal is less curved
Mesial and Distal Aspects
- Nearly identical to that of the central incisor
Incisal Aspect
- Triangular or ovoid
- Labial surface is flat compared to maxillary incisors
- Seldom labial lobe groove
- Long axis of the incisal edge is perpendicular to the labiolingual line
- Mesial outline is equal to the distal outline in length
- More of the labial surface is seen due to lingual inclination of the crown
- Incisal ridge perpendicular to the labiolingual bisecting line
- Crown shows lingual convergence
- Oval incisal form
- Crown bilaterally symmetrical
- Lingual fossa
- Cingulum
- Labiolingual dimension greater than mesiodistal
Root
- Straight from the cervix to the middle third, then tapers apically
- Convex mesiodistally, flattened labiolingually
- Developmental grooves on both the mesial and distal surfaces, deeper on the distal
- Pointed apex
- Apical third is usually straight, sometimes exhibits distal curvature
Identification
- Right and left: Symmetry of the tooth makes a judgement on right and left unreliable
- CEJ, root apex taper, grooves deeper on the distal root
- Central vs lateral: When viewed occlusally, the incisal ridge is at a right angle to the line bisecting the crown labiolingually
Variations
- Consistent in development, rarely absent
- Small tooth
- Short root
- Bifurcation of the root
Developmental Anomalies
- Talon's cusp
- Missing
- Fusion between mandibular central and lateral incisors
- Gemination
Pulp
- Bifurcation of the canal because of the root proximal grooves
Variations
- Two canals in a single root
- Long root
- Small size of the tooth
- Bifurcation of the root into labial and lingual divisions
Incisal Aspect
- The incisal edge is 'twisted' from the 90-degree angle with the labiolingual line
- Distoincisal angle is more towards lingual
Pulp
- Similar to that of the central incisor
Root
- Similar to that of the central incisor but longer
Identification
- Right and left, and central vs lateral: Two significant features assist in identification, even in a worn tooth. The incisal edge is 'twisted' relative to the labiolingual bisecting line anticipating the curvature of the dental arch. Also, the cingulum will be shifted towards the side from whence the tooth has come.
Anomalies
- Congenitally missing
- Fusion between mandibular central and lateral incisor
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