Development Of Occlusion Flashcards
When does preemergent eruption begin?
When root formation has started
Emergence, the movement when a cusp or an incisal edge of a tooth first penetrates the gingiva, usually occurs when ___% of the final root length is established.
75%
True or false… postemergent eruption haunts once it comes into occlusion.
False. It continues to to equal the rate of the vertical growth of the face.
On average, a molar tooth erupts about __mm after having reached the occlusal contact
10mm
Short-term eruption of teeth seems to follow a ___ rhythm, mainly occurring during the ___ hours of sleep. Tooth eruption and secretion of ___ and ___ hormones are correlated in its day-night pattern.
Circadian
Early
Growth and thyroid hormones
Primary dentin is fully formed by the age of ___ with the calcificaiton of the primary roots completed ___ later
2.5 years old
1 year later
The first primary tooth to erupt are the ____, which emerge at ___ months.
Lower central incisors
7 months
Where are the primate spaces located in the primary dentition?
Between the upper primary laterals and canines
Between the lower primary canines and first molars
It is estimated that if the total amount of space per dental arch is only 0-3mm, there is a ___% probability of crowding in the permanent dentition.
50%
In about 80% of children with a mesial-step terminal plane less than 2mm, ___ results.
Angle Class 1 molar relationship
If the mesial-step terminal plane is more than 2mm, a ___ molar relationship results in 20% of subjects.
Class 3
A flush terminal plane results in either a class 1 (___% of subjects) or a class 2 (___% of subjects) molar relationship
56%
44%
A distal-step terminal plane almost invariably results in a ___ molar relationship in the permanent dentition.
Class 2
Define angle class 1 molar relationship. What is the difference between Class 1 normal occlusion, and class 1 malocclusion.
Mesiobuccal cusp of upper first molar occuldes with the buccal groove of the lower first molar.
They both have the same molar relationship, but the latter is also characterized by crowding, rotations, and other positional irregularities.
Define angle class 2 molar relationship. What is the difference between division 1 and division 2?
MB cusp of the upper molar occludes anterior to the buccal groove of the lower first molar.
Division 1 - the upper incisors at labially tilted, creating significant overjet.
Division 2 - the upper central incisors are lingually inclined and the lateral incisors are labially inclined. When measured from the central incisors, overjet is within normal limits.
As a general rule, a tooth should erupt once ___ of the root is formed.
2/3rds
What occurs during the first transitional period?
First molars and all permanent incisors are present
What is the second transitional period?
First period - lower canines with upper and lower first premolars.
Second period - upper and lower second premolars, followed shortly by maxillary canines
Third period - second molars erupt
In both the maxilla and mandible, the permanent incisors develop and erupt on the ___ side of the roots of the primary incisors.
Lingual/palatal
How is the space deficit between primary and permanent incisors solved?
First, the upper incisors generally erupt to a wider dental arch circumference than the primary incisors, which is the most effective way to gain space for these teeth.
Second, when the central permanent incisors erupt they push the lateral incisors distally. The same thing happens when the laterals erupt which pushes the canines distally.
The transverse growth of the maxilla at its midpalatal suture also allows for space-gaining.
In the mandible, pushing takes place as it does in the maxilla. However the lower anterior teeth do not generally erupt to a wider dental arch circumference than the primary teeth, and no transverse growth can take place. Crowding is commonly seen once the lower permanent incisors have erupted.
If considerable spacing in the primary dentition (>5-6mm) does not exist, crowding is commonly seen once the permanent lower incisors have erupted. This is called ___
Physiological crowding
Describe the “ugly duckling” stage.
A normal spacing condition seen in the upper front areas. This is due to lateral incisors tipped distally due to pressure of the erupting canines on their roots. Once the permanent canines erupt, the upper spaces usually close and uprighting of the lateral incisors can be seen.
How is space secured for nonsuccedaneous teeth?
In the upper arch, space is created for the molars by bone apposition at the free posterior border of the maxilla. Also, the transverse palatal suture may make a contribution.
For the lower molars, bone apposition occurs on the posterior side of the mandibular ramus while bone resorption occurs on the anterior ramus.
Also, upper and lower first molars usually drift forward because of excess space due to the leeway space. This anterior drift of the first molars opens up space for the second molars to erupt.
How much leeway space is typically provided?
1-1.5mm of space in each upper quadrant
2-2.5mm of space in each lower quadrant
Leeway space is provided due to the size discrepancy of primary molars and permanent premolars.