Lecture 3

Question 1

Where do teeth come from?

Answer 1

• -Formation begins deep within bone in a sac called the follicle
• -Ameloblasts (a type of cell) create enamel
• -Odontoblasts create dentin

Question 2

What is active eruption?

Answer 2

The processof the tooth moving up into the mouth

Question 3

What is passive eruption?

Answer 3

The body will compensate for teeth grinding by growing the mandibular teeth up

Question 4

What is centric occlusion?

Answer 4

When the cusps of the upper and lower molars fit into the fossa of the other

Question 5

What are the outter, or non-fossa-fitting cusps called?

Answer 5

Balancing cusps

Question 6

What is unilateral cross-bite?

Answer 6

When one side of the teeth are overlapped correctly and the other side is not

Question 7

What is a bi-lateral cross-bite?

Answer 7

When the upper arch is smaller than the lower arch causing the maxillary teeth to fit inside the mandibular teeth on both sides

Question 8

What is the general rule that applies to tooth eruption, even if there is variation from the standard timetable?

Answer 8

• -People’s variation is consistent. If eruption is delayed, the rest of the teeth will come later also.
• -Mandibular teeth usually come in before maxillary (even through both mandibular and maxillary 1st molars are listed at 14 months the mandibular molar will usually precede the maxillary slightly)

Question 9

What is the first part of the tooth to form?

Answer 9

The occlusal surface

Question 10

Does enamel ever get repaired after it is formed?

Answer 10

No. Once it is completed for a single tooth enamel will never be formed again for that particular tooth.

Question 11

Define occlusion?

Answer 11

The way that the teeth fit/bite together after eruption has finished

Question 12

What is a proximal contact?

Answer 12

The first contact that a tooth makes where it touches teeth on either side

Question 13

What is mesial drift?

Answer 13

When a tooth is lost
for an extended period of time the other
teeth tend to collapse into the place left
by the extracted tooth. The majority of
this movement is towards
the midline. Thus MESIAL drift

Question 14

What is an embrasure?

Answer 14

The area where the teeth touch one another on the sides forming small triangular spaces

Question 15

How far are the upper molars shifted, and in what direction, in normal occlusion?

Answer 15

1/2 a tooth width in the posterior direction

Question 16

What is class 1 malocclusion?

Answer 16

• -The molar position is about the same as with normal occlusion, but the teeth are somewhat crooked
• -85% of caucasians

Question 17

What is class 2 malocclusion?

Answer 17

The mandibular molars are shifted back (posterior) more than normal (retruded chin)
–14% of caucasions

Question 18

What is class 3 malocclusion?

Answer 18

The mandibular molars are shifted forward (anterior) more than normal (protruding/prominent chin)
–1% of caucasians

Question 19

What causes the maxillary dentition to shift distally relative to the lower teeth?

Answer 19

The maxillary anterior teeth are larger than the mandibular anterior teeth

Question 20

What is horizontal overlap?

Answer 20

As the name implies, it is the horizontal distance between the upper and lower teeth.

• -About 2mm in Class 1
• -Larger in Class 2
• -Negative value in Class 3

Question 21

What is vertical overlap?

Answer 21

The distance which the upper and lower teeth cover one another

• -In a normal bite the upper anterior teeth will cover about 2-3 mm of the lower teeth (about 30%)
• -Deep bite is when the upper teeth cover much more than 30% of the lower teeth

Question 22

What is it called when the posterior teeth are in occlusion, but the anterior teeth do not overlap, and what causes this?

Answer 22

• -Anterior open bite

- -Causes: Thumb sucking, or abnormal swallowing (anterior tongue thrusts)

Question 23

What is ankylosis?

Answer 23

• -A condition where the PDL dissolves and a tooth directly fuses to the bone
• -This prevents that tooth from being moved orthodontically

Question 24

What is the third most prevalent type of cancer?

Answer 24

Ameloblastoma

Question 25

What is reverse pull head gear used for?

Answer 25

To pull the front teeth forward

Question 26

How quickly can Rapid Palatal Expansion work?

Answer 26

Sometimes in as short as 2 weeks

Question 27

What percentage of people who obtain orthodontic treatment experience a relapse?

Answer 27

70%

Question 28

How long does it take to train for the Invisalign course?

Answer 28

8 hours