Lecture 3 Flashcards
Where do teeth come from?
- -Formation begins deep within bone in a sac called the follicle
- -Ameloblasts (a type of cell) create enamel
- -Odontoblasts create dentin
What is active eruption?
The processof the tooth moving up into the mouth
What is passive eruption?
The body will compensate for teeth grinding by growing the mandibular teeth up
What is centric occlusion?
When the cusps of the upper and lower molars fit into the fossa of the other
What are the outter, or non-fossa-fitting cusps called?
Balancing cusps
What is unilateral cross-bite?
When one side of the teeth are overlapped correctly and the other side is not
What is a bi-lateral cross-bite?
When the upper arch is smaller than the lower arch causing the maxillary teeth to fit inside the mandibular teeth on both sides
What is the general rule that applies to tooth eruption, even if there is variation from the standard timetable?
- -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)
What is the first part of the tooth to form?
The occlusal surface
Does enamel ever get repaired after it is formed?
No. Once it is completed for a single tooth enamel will never be formed again for that particular tooth.
Define occlusion?
The way that the teeth fit/bite together after eruption has finished
What is a proximal contact?
The first contact that a tooth makes where it touches teeth on either side
What is mesial drift?
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
What is an embrasure?
The area where the teeth touch one another on the sides forming small triangular spaces
How far are the upper molars shifted, and in what direction, in normal occlusion?
1/2 a tooth width in the posterior direction
What is class 1 malocclusion?
- -The molar position is about the same as with normal occlusion, but the teeth are somewhat crooked
- -85% of caucasians
What is class 2 malocclusion?
The mandibular molars are shifted back (posterior) more than normal (retruded chin)
–14% of caucasions
What is class 3 malocclusion?
The mandibular molars are shifted forward (anterior) more than normal (protruding/prominent chin)
–1% of caucasians
What causes the maxillary dentition to shift distally relative to the lower teeth?
The maxillary anterior teeth are larger than the mandibular anterior teeth
What is horizontal overlap?
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
What is vertical overlap?
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
What is it called when the posterior teeth are in occlusion, but the anterior teeth do not overlap, and what causes this?
- -Anterior open bite
- -Causes: Thumb sucking, or abnormal swallowing (anterior tongue thrusts)
What is ankylosis?
- -A condition where the PDL dissolves and a tooth directly fuses to the bone
- -This prevents that tooth from being moved orthodontically
What is the third most prevalent type of cancer?
Ameloblastoma
