Week 1: Access and root canal location

Question 1

Which teeth fail the most following RCT?

Answer 1

1. Upper first molars
2. Lower incisors
3. Lower canines
4. Lower first premolars
5. Lower first molars
6. C shaped molars

Question 2

Which canal is often missed in upper first molars

Answer 2

The second canal in the media buccal cusp (MB2)

So the end up only finding 3 not 4

Question 3

Why might RCT usually fail in lower incisors?

Answer 3

As in 30-40% of them there’s lingual canal that is missed or can be inaccessible

Question 4

Why might RCT in lower canines fail?

Answer 4

1. Lingual canal is missed or inaccessible

2. The canals are usually longer and so it can be harder to prepare and obturate

Question 5

Why might RCT in lower first premolars fail?

Answer 5

Difficult to locate lingual canal so can be missed

Question 6

Why might RCT in lower first molars fail?

Answer 6

Distal roots usually can two canals and the second canal is usually missed

Question 7

What is the average length of an upper first molar?

Answer 7

22mm

Question 8

How many canals and roots are there in an upper first molar?

Answer 8

99% have 3 roots

Generally 4 canals

Question 9

How many foramina are there in an upper first molar?

Answer 9

60% have 3

40% have 4

Question 10

What is the average length of a lower incisors?

Answer 10

22mm

Question 11

How many canals and roots are there in a lower incisor?

Answer 11

98% have 1 root

40% have 2 canals

Question 12

Which canal is hardest to find in a lower incisor?

Answer 12

The 2nd lingual canal

Question 13

How many foramina are there in a lower incisor?

Answer 13

90% have 1 foramen

10% have 2

Question 14

What is the average length os a lower canine?

Answer 14

27.5mm

Question 15

How may roots and canals are there in a lower canine?

Answer 15

95% have 1 root

Usually have 1 canal but 20% have 2

Question 16

What is the average length of a lower first premolar?

Answer 16

23MM

Question 17

How many roots and canals are there in a lower first premolar

Answer 17

80% have 1 root

75% have 1 canal, 24% have 2 canals and 1% has 3 canals

Question 18

In a lower first premolar with 2 canals which canal is often missed?

Answer 18

The canal that is lingually placed

Question 19

What is the average length of a lower first molar?

Answer 19

22mm

Question 20

How may ROOTS are there in a lower first molar?

Answer 20

95% have 2 roots

5% have 3 roots

Question 21

In the mesial root of a lower first molar how many CANALS are there?

Answer 21

12% have 1 canal
87% have 2 canals
1% have 3 canals

Question 22

In the distal root of a lower first molar how many CANALS are there?

Answer 22

70% have 1 canal

30% have 2 canals

Question 23

In the mesial root of a lower first molar how many FORAMINA are there?

Answer 23

60% have 2 foramina

Question 24

In the distal root of a lower first molar how many FORAMINA are there?

Answer 24

85% have only 1 foramen

Question 25

What are c shaped molars?

Answer 25

Single ribbon shaped canal with a 180 degree arc starting at messy lingual angle, sweeping around the buccal to end at the distastes aspect of the pulp chamber

Question 26

Name the different laws we can use to help us find all the canals in a tooth

Answer 26

1. Law of symmetry I
2. Law of symmetry II
3. Law of colour change
4. Law of orificle location I
5. Law of orificle location II
6. Law of orificle location III

Question 27

Which tooth is the only exception to both the law of symmetry?

Answer 27

Maxillary molars as their canals are halfway from a line drawing in a mesial distal direction through the pulp chamber floor

Question 28

How do we use the law of symmetry 1 to ensure we have located all the canals?

Answer 28

We draw a line that bisects the tooth mesial to distal and we assume that any canal we find on one side we will find in the same place on the other side

Question 29

How do we use the law of symmetry 2 to ensure we have located all the canals?

Answer 29

We draw a line that bisects the tooth mesio distally then perpendicular to this line we drawn another that separates the tooth bucco lingually
We assume that all teeth are symmetrically so if you find a canal in on one side of the tooth its mirror image will be there on the other side

Question 30

All teeth are S________

Answer 30

Symmetrical!!!!!

Question 31

What does the law of colour change state?

Answer 31

That the colour of the pulp chamber floor is always darker than the walls

Question 32

State the law of orificle location I

Answer 32

The orificles of the root canals are always located at the junction of the walls and the floor

Question 33

State the law of orificle location II

Answer 33

The orificles of the root canals are locates at the angles in the floor wall junction

Question 34

State the law of orificle location III

Answer 34

The orificles of the root canals are located at the terminus of the rot developmental fusion lines

Question 35

To be able to use the law of orificles III what must you have

Answer 35

Good magnification

Question 36

How big should the access cavity be?

Answer 36

The base of the access cavity needs to be no bigger than the footprint of the pulp chamber

Question 37

Why should we try and make the access cavity as conservative as possible (while still being able to see the entire pulp floor)

Answer 37

So that we can conserve dentine