Anatomy of Permanent Incisors and Canines W2

Question 1

What are three important features and functions of the incisors?

Answer 1

2 Central and 2 Lateral in both MX and MN

1) Thin blade-like crowns adapted to cutting/shearing of food
2) Incise the food - for function
3) Have incisal edges and ridges instead of cusps

Question 2

What defines mamelons on incisors?

Answer 2

3 facial developmental lobes are separated by developmental grooves. (Junctions of mamelon lobes- can be seen from incisal view)
Mamelons form when the enamel fuses while the tooth is still developing under the gums. Lobes fuse before the tooth pokes through the gum tissue. These little serrations of enamel help the tooth poke through the gums so the entire tooth can erupt.

Question 3

Incisors usually erupt in arch pairs (within 6 months), how many roots do incisors have?

Answer 3

Single root

Question 4

Within what time frame is root development usually complete in central and lateral incisors?

Answer 4

Usually complete 2 years post eruption
Usually 2/3 complete at clinical emergence (eruption)

Question 5

Label each incisor relationship in occlusion (anterio-posterior)

Answer 5

Question 6

Identify the term for each of the incisor occlusal relationships below:

Answer 6

Question 7

A) What is the other term for canine?
B) Describe the roots of canines, which canine can have x2 roots.

Answer 7

A) Cuspid- single cusp
B) Single root- longest roots in the dentition. Mandibular canine can be bifurcated.

Question 8

What is known as the “cornerstone” of the dental arch AND why?

Answer 8

Canine/cuspid. Robustness makes them the most stable in the mouth used for seizing and tearing food.

Question 9

What are incisal edges/ridges replaced by in canines?

Answer 9

Cusp tips and line margins

Question 10

What does premature loss of canine result in?

Answer 10

Accentuation of the naso-labial fold (cosmetic value)

Question 11

What are two unique structures of canines and their related functions?

Answer 11

1) Labially the canine is convex in all directions- promotes self-cleansing
2) Long root- strong anchorage tends to preserve them throughout life

Question 12

Describe a Class I canine-occlusal relationship

Answer 12

When the mesial slope of the upper canine coincides with the distal slope of lower canine.

Question 13

What are the key differences in maxillary canine and mandibular canine?

Answer 13

Maxillary canine in the upper jaw and erupts between 10-11 years of age. They typically have a larger crown and longer root than the mandibular canines Whereas the mandibular canines in the lower jaw erupt between 9-10 years of age and are typically smaller in crown size and shorter in root length.

Question 14

Describe the the labial area of maxillary central incisors and lateral incisors?

Answer 14

Labial Central:
Convex mesial-distal, cervical-incisor
x4 marginal lines
Two angles Mesioincisal sharper than distal incisal.
Mesial margin longer than distal margin.
Square/rectangular

Labial Lat:
Surface MORE convex
Narrower mesiodistally and shorter cervicoincisally
Angles MI and DI more round but mesial is still sharper than distal.
Incisal line more sloped not as straight as MX
Smaller more condensed

Question 15

What are the key stages in development of permanent central incisors?

Answer 15

MN: 3,1. 4,1
First sign of Calc 3-4 months. Crown complete 4-5. Erupts 6-7. (Succeed MX)

MX: 1,1. 2,1
First sign of calc 3-4 months. Crown complete 4-5. Erupts 8-9.

Question 16

Differences between labial areas of Central MX vs Central MN?

Answer 16

Central max:
Labial: convex on all surfaces. x4 marginal ridges. Two line angles- Mesioincisal is sharper than distalincisal. Mesial margin longer than distal margin. More square/rectangular. Mamelons first eruption.

Central man:
Labial: smaller than MX. Narrow at cervical end - fans out can become triangular. It’s x2 longer than it is wider. Less convex. Same angles. STRAIGHT incisal edge. Mamelons less pronounced.

Question 17

How does root formation help determine whether the tooth is left or right position?

Answer 17

The root curves distally- that is away from the midline of the face.

Question 18

What are two unique features of maxillary lateral incisors appearance?

Answer 18

1) Compared to mandible can be peg shaped (pointy)
2) Hypodontia of maxillary lateral incisors

Question 19

Which two anterior teeth are more prone to lingual pits? AND What is the name for these pits?

Answer 19

Max and Man lateral incisors. Foramen caecum- pit towards tooth root

Question 20

Differences between lingual areas of Central MX vs Central MN?

Answer 20

MX: Concave middle to incisal 1/3. Lingual fossa deepest toward incisal.
Convex in cervical 1/3 due to cingulum. Sometimes two shallow ridges (depressions) at incisal area).

MN: Smooth. rarely has pits. Less defined cingulum. Margins less defined. Less concave mesial to distal. More concave incisal to cervical.

Question 21

On a proximal position regarding contact areas of Central and Lateral Maxillary Incisors - what can be identified?

Answer 21

Mesial and distal sides are convex at 1/3 of incisal area on both incisors. However, lateral incisors distal side is more convex/round due to its proximal contact with canine.

Question 22

What differs in the labial surface of Central MN vs Lateral MN?

Answer 22

Central is narrower at cervical end and fans out slightly- and is x2 longer in length than width.
Lateral is larger mesial-distally. and taller than central MN. ***It’s also wider messy-distal by 1mm.

Question 23

In the maxillary canines, what lobe makes the cingulum? AND how does the lingual surface of the canines differ to the incisors?

Answer 23

Palatal lobe makes cingulum. Cingulum is more pronounced than incisors. Lingual surface is smooth and lingual ridge is developed.

Question 24

How does the mandibular canine differ from the maxillary canine?

Answer 24

Labially: Cusp tip on MX (covers 1/3 of crown) is larger than MN (covers 1/5).
Cusp tip is more sharp/pointy in MX than MN.

Lingually: MX develops lingual ridge, more convex- more pronounced cingulum and marginal ridges compared to MN

Question 25

Describe the contact proximal areas of canines

Answer 25

wedge shaped crown. Distal contact is 1/3 mid compared to 1/3 incisors on incisors (therefore larger contact area distally on canines than incisors).
In mandibular canine- cervical line curves toward incisors.

Question 26

What is the development of the MX vs MN canines?

Answer 26

MX: 1st calc= 4-5 months. Crown complete 6-7 years. Erupt: 11-12 years.
MN: 4-5 months. 6-7 years. Erupt 9-10 years.

Question 27

What are the differences in root shape in MX and MN canines?

Answer 27

MX has a thicker root. Triangular cross-section. x2 depressions that look like two roots. Apex is blunt.

MN: has a longer root. Sometimes bifurcated. Apex is pointed.

Question 28

Lingual differences of Lateral vs Central incisors (generally for both upper and lower sets).

Answer 28

Centrals are more smooth. Laterals have more defined cingulum, lingual fossa and are more concave. They can have foramen caecum pits. And are more prone to cavities than centrals.

Question 29

What is the difference between lateral incisors roots of MN vs MX?

Answer 29

MN: x2 grooves (longitudinal and distal) that give appearance of two roots.

Question 30

In relation to mamelons- label the diagram for what’s included in describing their development.

Answer 30

Question 31

For incisors- how much of the root is developed at initial eruption AND when does root completion occur?

Answer 31

2/3 root developed at eruption. Root completed 2 years after eruption.

Question 32

Identify which class of incisor occlusion relationship (classes) these sets of teeth are.
Class II (div 1), Class II (div 2), Class III- and explain what each class means.

Answer 32

Class II div 1 = if lower incisors positioned too far posteriorly = over jet big
Class II div 2 = if lower incisors positioned too far posteriorly = retro inclining
Class III = if lower incisors positioned too far anteriorly.

Question 33

Describe optimal occlusion of incisors and what class is this?

Answer 33

Class I= mandibular incisal edge occludes against cingulum or lingual fossa region of maxillary incisors.

Question 34

What is the difference between overjet and overbite?

Answer 34

Over jet- = 1-3 mm to 10mm is horizontal misalignment (angle)
Over bite = vertical misalignment - (no angle)

Question 35

What are each of these incisor occlusion relationships?

Answer 35

Top = overjet
Middle = overbite
Bottom = Openbite

Question 36

What is happening in this image?

Answer 36

Impacted maxillary canines. Due to the sequence of eruption of canines. More common in maxillary canines as they erupt out of usual sequence - at 11-12 years. And at this age premolars have already erupted. Which affects room in arch for canines to propulse.

Question 37

Label and describe this image.

Answer 37

Used to describe the incisor relationship in occlusion anterior-posterior.

Question 38

Look at the OPG, what age would you expect this child to be? Why?

Answer 38

6-7 years.
Permanent central incisors maxillary and mandibular have erupted and lateral incisors have erupted. Canines MN and MX have began calcification

Question 39

What is the difference between MX lateral and MX central incisors?

Answer 39

• MI and DI angles are more rounded than in centrals
• Labial surface more convex than in central
• Narrower mesiodistally and shorter cervicoincisisally
• Incisal line slopes more on mesial aspect than in central

Question 40

What are the differences between the mesial and distal sides of incisors?

Answer 40

Sharper incisal edge on mesial angle.

Rounder distal incisal angle.