Morphology of Permanent Incisors Flashcards
Incisors
the two teeth (central and lateral)in each quadrant closest to the midline
-with the mesial surface of right central incisors
contacting the mesial of left central incisors
(unless a space or diastema exists)
diastema
space between maxillary or central incisors
primate spaces
present in primary teeth
-nothing to worry about, want spaces because teeth that will erupt there will be larger and need this space
Most commonly spaces are mesial to the maxillary canine and distal of the mandibular canine
maxillary central incisors
R 8 9 L
-crown: LONGEST incisor crown
maxillary lateral incisors
R 7 10 L
mandibular central incisors
R 25 24 L
mandibular lateral incisors
R 26 23 L
incisor functions
- Cut food
- Articulate speech
- Support lips (esthetic)
- Guide mandible during movement
Mamelons (incisors)
3 Mamelons reflect 3 Labial Developmental
lobes for incisors (before wear)
What characteristics do ALL incisors have from the Facial view?
• Relatively straight incisal edge • Rectangular shape: longer incisocervically than mesiodistally • Taper narrower from contact to cementoenamel junction (CEJ) • CEJ curves toward apex • Root tapers to apex and are longer than the crown
Which characteristics are typical of ALL incisors from the Facial view (EXCEPT Mandibular centrals)?
• Distal crown surface is more convex than mesial • Mesioincisal line angle is sharper than distoincisal • Distal contact is located more cervically than on mesial • Incisal edges slope cervically to distal
Characteristics of ALL incisors from the Lingual view
• Lingual surface narrower (seen best incisally) • Marginal ridges converge toward cingulum • Lingual fossa
Characteristics of ALL incisors from Proximal views
•Wedge shaped (triangular) outline • Height of contour in cervical third facially and lingually (cingulum) • Lingual outline is “S” • CEJ curves incisally • Root tapers to apex
Characteristics of ALL incisors from the Incisal view
• Concave lingual fossa incisal to cingulum • Incisal edge runs across between widest points on mesial and distal • Labial outline is broader (less convex) than lingual • Marginal ridges converge toward cingulum
Arch Traits: Mandibular incisors
– Smaller crowns – Flatter proximal outlines – Contacts closer to incisal edge – Roots relatively longer (compared to crowns) – Relatively wider crowns faciolingually – Smoother lingual surfaces – Incisal edges that are more likely lingual to midroot axis
Incisal Wear
More incisal ridge faceting on Labial of Mandibular incisors vs. Lingual of Maxillary incisors
Maxillary Incisors from the Labial view: Crown Shape
- Maxillary central has wider (2.0), longer (.5) crown
- Maxillary lateral is relatively narrower mesiodistally
- Maxillary lateral is more often missing or PEG shaped
Maxillary Incisors from the Labial view: Proximo-incisal angle
-Maxillary central has mesioincisal angle at nearly right angle -Maxillary lateral has both mesioincisal and distoincisal angles more rounded than on centrals
Maxillary Incisors from the Labial view: Proximal Contact Area
-Mesial contacts are in
incisal third, but lateral
contacts are more
cervical than central
-Maxillary central distal contact is at junction of incisal and middle third, lateral is more cervical: may be in middle thir
Maxillary Incisors from the Labial view: Root-to-Crown Proportions/Ratios
-Maxillary central root is not much longer than crown -Maxillary lateral root is relatively longer than on central
Maxillary Incisors from the Labial view: Root Shape
-Maxillary central root is shorter, thicker, more cone shaped (ice cream cone) -Maxillary lateral root more likely to bend distally at apex; central not as likely -Centrals have triangular shaped cross section and laterals are more oval
Maxillary Incisors from the Lingual View: Lingual Fossa
Maxillary laterals are more likely to have deeper lingual fossae and pits than centrals
Maxillary Incisors from the Lingual View: Cingulum
-Maxillary central incisor cingulum is more developed and is off center toward the distal (best seen from incisal view) -cingulum of maxillary lateral incisor is more centered
Maxillary Incisors from the Lingual View: Marginal Ridges
-Maxillary lateral incisor has the distal marginal ridge appear shorter than mesial (more so than on centrals) due to slope of incisal edge toward distal -on central this is also due to distal placement of cingulum
Variations in Maxillary Incisors
Shovel Shaped
and Double Shovel Shaped
Maxillary Incisors from the Lingual View: Accessory (Lingual) Ridges and Grooves
Possible on Maxillary Incisors
-smoke, drink coffee, easily stained
Maxillary Incisors from the Lingual View: Root Shape
Roots taper narrower
toward the lingual
Maxillary Incisors from the Proximal Views: Incisal Edge
-Incisal edge labial or at midroot axis line -Maxillary centrals (from distal view) may have distoincisal edge is lingual to the axis due to distolingual twist of incisal edge (shows better on incisal view)
Maxillary Incisors from the Proximal Views: Cervical Line
-As on all anterior teeth, the mesial CEJ curves more than the distal ( seen clearly here on a canine lingual view) - Largest CEJ curve for all teeth is mesial of maxillary central incisor (up to3.5 mm)
Maxillary Incisors from the Proximal Views: Height (Crest) of Contour
Both maxillary central and lateral incisors have the heights of contour (facial and lingual) in the cervical third
Maxillary Incisors from the Proximal Views: Root
*known for no depression on root surface; if slight depression, will be on MESIAL
-Maxillary central root has a flatter lingual outline in the cervical third, then tapers - Laterals have more overall uniform taper -No root depression on distal, rare shallow depression on mesial
Maxillary Incisors from the Incisal View: Crown Proportion Faciolingually vs. Mesiodistally
-Both maxillary incisors have mesiodistal greater than the faciolingual, but more so for the maxillary centrals -Laterals are closer to equal for FL and MD
Maxillary Incisors from the Incisal View: Outline Shape of Crowns
-Maxillary central has a triangular crown outline (because the facial surface is flatter) -Maxillary lateral has a more round or oval outline
Maxillary Incisors from the Incisal View: Incisal Ridge Contour
-Maxillary central exhibits a distolingual twist of the incisal edge; the lateral does not -Maxillary central has cingulum distal to root midroot axis line
Maxillary Incisors from the Incisal View: Labial Contour
Maxillary lateral has
more labial curvature
(is more convex) than
the central incisor
Mandibular Incisors from the Labial View: Crown Shape
-Mandibular central is symmetrical, don’t need to determine R vs L
-Mandibular lateral is
larger than central
-3 mamelons (before wear) on mandibular incisors
Mandibular Incisors from the Labial View: Incisal Proximal Angles
-Mandibular central has mesioincisal angle = distoincisal angle -Lateral has distoincisal angle more rounded than mesioincisal angle
Mandibular Incisors from the Labial View: Proximal Contact Areas
-Mandibular central has mesial and distal contact at SAME level (incisal third close to incisal edge) • Mandibular lateral has mesial contact more incisal than distal (incisal third, more cervically than central) • All contacts in incisal third
Mandibular Incisors from the Labial View: Root-to-Crown Proportion
Mandibular incisor roots appear to be longer relative to the crown than maxillary incisor roots
1.45 root crown ratio
Mandibular Incisors from the Labial View: Root Shape
-Distal bend of root tip is more common than mesial bend -Roots are narrow mesiodistally
Mandibular Incisors from the Lingual View: Lingual Anatomy (Marginal Ridges, Fossae, and
Cingulum)
-All mandibular incisors have
minimal marginal ridges and fossa depth (compared to maxillary incisors)
Mandibular Incisors from the Lingual View: Cingulum
Mandibular lateral cingulum is more distal to the midroot axis than on centrals (best seen incisally)
Mandibular Incisors from the Lingual View: Root Shape
Both mandibular incisors
roots are narrower from
lingual and have mesial
and distal root depressions (better appreciated comparing mesial and distal views)
Mandibular Incisors from the Proximal View: Incisal Edge
Mandibular lateral incisor (mesial view) has the distolingual corner of the incisal edge showing lingually due to the distolingual TWIST; centrals do not
Mandibular Incisors from the Proximal View: Cervical Line
CEJ curves toward
incisal more on the
MESIAL than distal
Mandibular Incisors from the Proximal View: Height (Crest) of Contour
-Buccal and lingual contours for both centrals and laterals are in the cervical third -All mandibular incisors have smooth lingual surfaces with shallow fossae
Mandibular Incisors from the Proximal View: Roots
-Mandibular roots are much wider faciolingually than mesiodistally, especially compared to maxillary incisors -Both mandibular incisors have mesial and distal root depressions (distal is deeper) -Both mandibular incisors cross sections of root are “Kidney” or “Bow” shaped
Mandibular Incisors from the Incisal View: Crown Proportions
ALL mandibular incisors
have the faciolingual
dimension greater than
the mesiodistal
Mandibular Incisors from the Incisal View: Crown Outline
Mandibular central
incisors are
symmetrical; laterals
are no
Mandibular Incisors from the Incisal View: Incisal Ridge Contour (Alignment)
Lateral incisor has an
incisal edge with a
distolingual TWIST;
central does not
Mandibular Incisors from the Incisal View: Cingulum
Mandibular lateral
incisor has a cingulum
distal to midroot axis;
central does not
Mandibular Incisors from the Incisal View: Labial Contour
All have convex facial
contour and lingual
contour decidedly
convex (more curved)
