Chapter 4: Study of dental arches

Question 1

Functions of anterior teeth

Answer 1

• Aesthetics
• Phonetics
• Initiates the mastication
• Anterior, incisal and canine guidance

Question 2

Functions of posterior teeth

Answer 2

• Elevations: cusps, ridges, and planes (slopes)
• Depressions: fossa and pits, fissures

Question 3

What is a pit?

Answer 3

It is a sharp pinpoint depression on the surface of the enamel

Question 4

What is a fossa?

Answer 4

An irregular depression or concavity on the surface of the tooth

Question 5

What are functional pits and fossa?

Answer 5

They are the pits and fossa that receive the active cusp
- Upper: mesial pit
- Lower: distal fossa

Question 6

What is an inclined plane?

Answer 6

It is the sloping area found between 2 cusp ridges

Question 7

Each cusp has 2 inclined planes. True or False

Answer 7

False, each cusp has 4 inclined planes

Question 8

What cusps are working cusps?

Answer 8

The upper palatal and the lower buccal cusps

Question 9

What do active cusps do?

Answer 9

They support the VDO and stabilise the arch

Question 10

Other names for working cusps

Answer 10

active, cutting, functional, centric, supporting cusps

Question 11

Other names for non-working cusps

Answer 11

non-active, protecting, non-functional, non-centric, guiding cusps

Question 12

What cusps are the non-working cusps?

Answer 12

Upper buccal and lower lingual cusps

Question 13

The active cusps function correctly when following the vertical axis. True or False

Answer 13

True

Question 14

Match the letters with the numbers:

1. Marginal ridges
2. Central ridges
3. Triangular ridges

A. form the cusp
B. in the mesial and distal areas of the occlusal surface of premolars and molars
C. towards the major fissure and buccally

Answer 14

1. B
2. C
3. A

Question 15

Each cusp has _____ cusp ridges extending in different directions from its tip

Answer 15

4

Question 16

Normally the cusp ridge that extends towards the central portion of the occlusal surface is also a _____ _____

Answer 16

Triangular ridge

Question 17

What is the line going from the first tooth to the last one called?

Answer 17

The main groove

Question 18

The ____ ____ will use the main groove to start the protrusion movement.

Answer 18

Active cusp

Question 19

What do we have on each side of the axial line?

Answer 19

Slopes

Question 20

Definition of a fissure

Answer 20

A long depression on the surface of the tooth

Question 21

Definition of a groove

Answer 21

A shallow linear depression on the surface of a tooth

Question 22

Match the letters with the numbers:

A. Central/Developmental grooves
B. Supplemental grooves

1. They extend from mesial to distal and they serve as an escape for protrusive movements
2. They are less distinct and do not mark the junction of primary parts
3. They provide supplementary anatomy and increase the masticatory effectiveness
4. They are shallow grooves between the primary parts of the crown or root

Answer 22

1. A
2. B
3. B
4. A

Question 23

Where are the working grooves in the upper molars?

Answer 23

• From central fossa to buccal in upper molars
• From central fossa to lingual in lower molars

Question 24

_____ grooves are non-working grooves

Answer 24

Oblique

Question 25

Working grooves transverse the main fissure. True or False

Answer 25

True

Question 26

On the working side, we are using _____ grooves

Answer 26

Straight

Question 27

On the non-working side, we are using _____ grooves

Answer 27

Lateral or Oblique

Question 28

Match the letters with the numbers: 1. Working side 2. Non-working side A. Pivoting B. Balancing

Answer 28

1. A 2. B

Question 29

Match the letters with the numbers: 1. Sagittal plane 2. Frontal plane 3. Horizontal plane A. It is the buccal inclination of the maxillary teeth and the lingual inclination of the mandibular teeth. B. It is an imaginary plane joining the incisal edges of the front teeth and the cusps of the premolars and molars. C. It is the mesial inclination of the mandibular teeth and the upper double inclination, that is mesial in anterior teeth and distal in posterior teeth of the maxilla.

Answer 29

1. C 2. B 3. A

Question 30

What is the Spee curve?

Answer 30

The Spee is an imaginary line joining the incisal edges of the teeth and the active cusps of the molars and premolars. It is concave in the mandible and convex in the maxilla.

Question 31

What is the Wilson curve?

Answer 31

It is an imaginary line that results in joining the buccal and lingual cusps on both sides of the arch

Question 32

What do the Spee and Wilson curves promote?

Answer 32

Posterior disocclusion in natural teeth

Question 33

What plane is also known as the occlusal plane?

Answer 33

The horizontal plane

Question 34

What plane is almost parallel to Camper?

Answer 34

The horizontal plane

Question 35

The occlusal plane will pass over all cusps. True or false

Answer 35

True. The occlusal plane will pass over all cusps not only the active ones

Question 36

What is shorter the mandible or the maxilla? And why?

Answer 36

The mandible is slightly shorter because the incisors are narrower

Question 37

The upper arch occludes buccally, and each tooth occludes with 1 antagonist. True or False

Answer 37

False. The upper arch occludes buccally, and each tooth occludes with 2 antagonists.

Question 38

What is an overjet?

Answer 38

Length in mm of the incisal edge of the upper incisors to the labial surface of the lower incisors.

Question 39

What is an overbite?

Answer 39

Part of the vestibular surface of the lower central incisor is covered by the maxillary central incisor. The normal value is 1/3.

Question 40

Class 1 angle definition

Answer 40

- MV cusp of 16 to the buccal fissure of 46 - MP cusp of 16 to central fossa of 46 - The upper canine cusp between the lower canine and the first premolar

Question 41

Class 2 of angle definition

Answer 41

- MV cusp of 16 to mesial buccal fissure of 46 - MP cusp of 16 to the marginal ridge of 45-46

Question 42

Class 3 of angle definition

Answer 42

- MV cusp of 16 to distal buccal fissure of 46 - MP cusp of 16 to the marginal ridge of 46-47

Question 43

What is the origin of alignment between arches?

Answer 43

- Muscle strength: lips, muscles of the face and tongue thrusting - Habits and para functions

Question 44

What gives the teeth long term stability

Answer 44

- Interproximal contacts - Occlusal contacts