1st Session: Alignment of Teeth (1-8, Segal)

Question 1

What 4 factors are important for tooth position?

Answer 1

Tooth size

Arch width

Surrounding soft tissue

Surrounding musculature (lips, cheeks, tongue)

Question 2

What is necessary for a neutral position in terms of forces acting on the tooth?

Answer 2

Lingual forces must be in equilibrium with the labial forces (lips and cheeks).

Question 3

What does an anterior open bit indicate in an adult?

Answer 3

A large and active tongue.

During swallowing, the tongue fills the anterior space in order to seal the mouth.

Question 4

Does the loss of a single tooth affect arch alignment?

Answer 4

Yes! The loss of a single tooth has significant effects on the stability of both arches.

Question 5

Why is there a curvature to the occlusal plane?

Answer 5

The teeth are positoned in the arches at varying degrees of inclination (ex: posterior teeth are offset from the long axis of the body).

The curvature permits maximal utilization of tooth contacts during function and dristributes forces so that the teeth all “hit” at the same time.

Question 6

What would be the main downside of having a flat occlusal plane?

Answer 6

Simultaneous function contact in more that one area of the dental arch would be impossible.

Question 7

In which direction are all teeth inclined (distally or mesially)?

Answer 7

Mesially!

Question 8

In which direction are the crowns of the mandibular posterior teeth inclined?

Answer 8

Lingual inclination!

Question 9

Which direction do the maxillary posterior teeth incline?

Answer 9

Toward the buccal.

Question 10

How long is the occlusion table in comparison to the total buccolingual width of a posterior tooth?

Answer 10

Occlusion table = 50-60% of the total buccolingual width.

Question 11

What is the basic, normal buccal-lingual relationship for interarch tooth alignment?

Answer 11

Mandibular buccal cusps occlude in the central fossae of the maxillary teeth.

Maxillary lingual cusps occlude in the central fossae of the mandibular teeth.

Question 12

What was a key point made regarding the supporting or centric cusps in relation to interach tooth alignment?

Answer 12

Without functional cusps, the jaw would close too far down.

Question 13

What is the purpose of the guiding or non-centric cusps (the non-functional cusps)?

Answer 13

They are the guiding cusps!

Help prevent from biting the cheek and tongue.

Question 14

Compare and contrast the morphology of a centric cusp and a guiding cusp on a mandibular tooth.

Answer 14

Centric cusp: round and broad

Guiding cusp: sharp (a shearing cusp)

Question 15

What does FOA stand for?

Answer 15

Functional Outer Aspect

Question 16

What is significant about the FOA (functional outer aspect) of the centric cusp in posterior teeth?

Answer 16

It is the only area of an outer incline with functional significance.

Question 17

In a normal occlusal relationship, how are the mandibular teeth positioned tot he maxillary teeth as a whole?

Answer 17

The mandibular teeth are

lingual and mesial

to their counterparts in the maxillary arch.

Question 18

How many teeth does a maxillary 3rd molar oppose?

Answer 18

1 tooth: the mandibular 3rd molar

Question 19

How many teeth does a mandibular central incisor contact?

Answer 19

They only contact 1 tooth because they are so small.

Question 20

How many teeth does each tooth occlude? And what are the exceptions?

Answer 20

Each tooth occludes with two opposing teeth.

Question 21

Where does the maxillary lingual outline (LO) hit in ideal occlusion?

Answer 21

In the central fossa (CF) line of the mandibular arch.

Question 22

Where does the mandibular buccal outline (BO) hit in ideal occlusion?

Answer 22

In the central fossa (CF) line of the maxillary arch.

Question 23

Where are the proximal contact areas in relationship to the CF line, and what function does this contribute to?

Answer 23

Proximal contact areas: buccal to the CF line

This leads to a greater lingual embrasure - a great spillway for food to aid in chewing (more efficient than using muscles!)

Question 24

Give the main ideas for each of the 3 occlusion classes:

Answer 24

Class I Occlusion: ideal

Class II Occlusion: overbite

Class II Occlusion: underbite

Question 25

Describe Class I Occlusion: where do the cusps line up?

Answer 25

Mainly, look at the 1st maxillary molar.

1. Embrasure area between maxillary 2nd premolar and the maxillary 1st molar: the mandibular 1st molar occludes in that area.
2. The mesiobuccal cups of the maxillary 1st molar is aligned directly over the buccal groove of the mandibular 1st molar.
3. The mesiolingual cups of the maxillary 1st molar is situated in the central fossa area of the mandibular 1st molar.

Question 26

What are the characteristics of Class II Occlusion?

Answer 26

Either the maxillary jaw is big or the mandibular jaw is small. Again, use the maxillary 1st molar for reference:

1. The CF line of the maxillary 1st molar occludes with the mesiobuccal cusp of the mandibular 1st molar.
2. The buccal groove of the maxillary 1st molar is aligned with the mesiobuccal cusp of the mandibular 1st molar.
3. The distolingual cusp of the maxillary 1st molar occludes in the CF line area of the mandibular 1st molar.

Question 27

What are the characteristics of Class III Occlusion?

Answer 27

What are the characteristics of a Class II Occlusion?

The mandibular jaw is either larger or moved forward. Again, use the maxillary 1st molar as reference.

1. The embrasure between the maxillary 1st molar and the maxillary 2nd premolar is filled with the distobuccal cusp of the mandibular 1st molar.
2. The mesiobuccal cusp of the maxillary 1st molar sits in the embrasure between the mandibular 1st and 2nd molar.
3. The mesiolingual cusp of the maxillary 1st molar sits in the mesial pit of the mandibular 2nd molar.

Question 28

Define canine guidance:

Answer 28

When moving side to side, the posterior teeth do not hit, just the canines touch.