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.
The primary molars are on average ___mm larger than the second premolars
2mm
Sometimes the lower second molars erupt before the second premolars. What can this cause?
This may cause anterior drift of the first permanent molars too early and, as a consequence, space loss for the second permanent premolars. Therefore, it is preferable that the second premolars erupt before the second permanent molars.
Since the leeway’s space provides the space needed for the upper canines, they should erupt [after/before] the permanent first premolars. If not…
After
If not, lack of space may cause the upper canines to erupt too labially
During the eruption of the maxillary permanent incisors, intercanine dimension increases on average by ___mm. Befor or at the time of eruption of the permanent canines another increase of __mm takes place in the canine-to-canine distance. This increase is caused by the distalizing pressure of the erupting permanent incisors on the permanent canines and growth in width of the maxilla at the midpalatal suture.
3mm
2mm
What is different between the upper and lower arches in determining the intercanine distance?
In the lower dental arch, a comparable increase of the intercanine distance occurs during the eruption of the permanent incisors (3mm on average). However, unlike the upper arch, no additional increase in the canine-canine distance takes place in the lower arch during the later stages of dental development. This early establishment of the lower intercanine distance has an important clinical bearing in that attempts to increase lower intercanine distance by orthodontics usually results in relapse.
How is dental arch width typically measured?
Distance between the corresponding contralateral teeth at the cusp tips.
Another measurement can be made at the palatal/lingual gingival level of the teeth; this measurement describes the width of the bony arch.
What is secondary crowding?
Increase of existing crowding in the lower anterior area found in the late teens or early 20s. This crowding occurs before or simultaneously with the emergence of 3rd molars.
What contributes to secondary crowding?
Maxillary and mandibular differential growth. Growth of the maxilla ceases earlier than growth of the mandible. Because of overbite, lower anterior teeth cannot move forward to the extent of the lower jaw growth but tilt lingually to a small circumference, which results in crowding.
in addition, the maturation of soft tissues that occurs during the teenage period may increase the pressure from lips, causing crowding.
More forward drift takes place in the lower dentition than in the upper arch, which also increases crowding.
True or false… delayed tooth eruption is possible, but premature tooth eruption is more common.
False.. it is the other way around… premature tooth eruption is possible, but delayed tooth eruption is more common.
Reasons for delayed tooth eruption bay be divided into rare systemic factors and more frequent local factors. What are some of local factors?
Supernumerary teeth
Heavy fibrous gingival tissue because of premature loss of a primary tooth
Crowding
Sclerotic alveolar bone
Ankylosis of a tooth
As a general rule, if a permanent tooth has erupted but its counterpart does not within 6 months, an eruption problem is evident and further investigation is recommended.
True or false… ankylosis is more common in the primary teeth than the permanent
True (especially primary molars)
What are the most common ectopically erupted teeth?
Upper first molars and canines followed by lower canines, upper premolars, lower premolars, and upper lateral incisors.
Which teeth have the longest path of eruption?
Maxillary canines
What percent of maxillary canines are impacted?
About 2%
Interestingly, nearly 50% of patients with palatal located upper canines also present with ___.
Peg laterals or congenitally missing upper laterals
What is the typical eruption problem of the second permanent molars?
If space is not adequate for the upper second molars, they often told buccally and distally before their emergence and eventually erupt too buccally. On the contrary, lower second molars tend to tilt lingually
External forces on teeth (cheeks, lips, tongue) are not completely in balance. However, periodontally healthy teeth do not move, why?
The balancing factor is the PDL.
Thus, if if support from the alveolar bone and PDL is reduced, teeth are prone to move.
During the period between 8 and 18 years of age, anterior and posterior face height increases by about ___mm.
20mm
WHat happens if growth of anterior and posterior face is not in balance?
Either anterior or posterior growth rotation of the mandible occurs. This is followed by overeruption of posterior or anterior teeth in posterior or anterior rotation patterns respectively.
It has been found that anterior facial height may continue to increase still between ages __ and ___
25 and 45 (and probably beyond in healthy individuals0
True or false… It has been found that dental implants in the upper front area may exhibit major vertical steps in the same amount in persons with early (15-21 years) or late (40-55) implant placement .
True. Therefore, from the occlusal development point of view, placement of dental implants should be postponed as long as possible.
What are the most common congenitally missing permanent teeth?
1) lower second premolars
2) upper laterals
3) upper second molars
True or false… DAPs (Dental anomaly patterns) are commonly associated with each other.
True. Thus when one DAP is found, a closer look of the patient should be taken to see if there are any other DAPs
Does variation in tooth size have an effect on occlusion?
Variation in tooth size is a relatively common finding and may have an effect on occlusion.
What is the prevalence of “tooth size discrepancy”? Which teeth show the largest variation in size?
About 5%
Upper permanent laterals. If they are significantly smaller or larger than average, ideal occlusion is difficult to establish.
