development of normal occlusions 1 Flashcards
stage of gum pads:
from birth until completion of deciduous dentition (0-2 1/2 years)
deciduous dentition :
2 1/2 to 6 years
mixed dentition :
6 to 12 years
maxillary gum pad and mandibular gum pad shape :
maxillary : horse shoe
mandibular: U
alveolar part of maxillary gum pad is separated on its palatal side from hard palate by:
dental or gingival groove ( continuous horizontal groove)
mandibular grooves are ____ in relation to maxillary
less defined
groove distal to canine segment continuing on buccal side of the gum pad:
lateral sulcus
which typr of growth in the first year of life allows gum pads to increase in arch width ?
lateral growth , which finally permits incisors to errupt with good alignment . this process is helped by molding effect of upper lip
calcification of deciduous teeth begin ___
early in 4th month IUL
What is the first tooth to erupt ?
mandibular central incisor at about 6-7 months
primary maxillary central : 8 months
both maxillary and mandibular lateral : 9 months
first deciduous molars: 14-15 months
canine : 18 months \
2nd molar: 24 months
most primary arches are ___ in shape
ovoid
what is the primate space?
additional spacing over the generalized spacing of the deciduous dentition found mesial to the maxillary canines and distal to the mandibular canines
what is responsible for the closing of the mandibular primate space?
eruption of permanent mandibular first molar
what is responsible for the closing of the maxillary primate space?
the eruption of the maxillary central incisor
what sort of occlusion of the anterior teeth can be seen at around 3 years of age ?
excessive overbite . it is self correcting through :
-eruption of deciduous molars
-attrition of incisors
-forward movement of mandible as it catches up to maxillary growth
slide 35??
flush terminal plane of distal surfaces of both maxillary and mandibular second primary molars is due to
the mandibular 2nd primary molar being wider mesiodistally than the maxillary one
what are the complications that may be present if the flush terminal plane remians ?
it will lead to an end to end relationship of the first permanent molars when they erupt distal to the second deciduous molars and arrive to occlusion
in case of absence of spacing in deciduous dentition :
no space will be available for early mesial migration of mandibular first permanent molar. so the mandibular first permanent molar will remain in an end to end relationship till shedding of mandibular deciduos decond moalrs
mesial step in deciduous dentation is important because it allows for
In such a case the distal surface of the mandibular primary second molar assumes a distinct mesial step terminally in relation to that of the maxillary allowing the first permanent molars to erupt in normal molar relationship.
describe the processes of early mesial shift :
1.) closure of primate space distal to mandibular canine \
2.) As a result of natural occlusal wear of the cusps of the deciduous incisors, the mandible is allowed to move forward by its forward component of growth.
causes resulting in distal step:
thumb sucking , excessive growth of maxilla
accessional teeth+ non sucedaneous
first transitional period of mixed dentition :
-eruption of permanent molaras and eruption / transition/ exchange of permanent incisors—> shifting of flush terminal plane
second transitional period :
-replacement of deciduous molars and canine by permanent canine and premolars following 2 events :
-leeway space of nance
-ugly duckling stage
how does the early mesial shift of the erupting first molar occur?
by utilizing normal physiological spaces between deciduous molars/ primate spaces
mechanism of later mesial shift of erupting first molars:
leeway space of nance
permanent incisors develop____ to primary incisors .
lingually , because they require more space since they are larger. this extra space required is known as the incisor liability
size difference between maxillary primary and permanent incisors?
between mandibular primary and permanent incisors=?
7mm
5mm
incisor liability is provided by :
-spacing of deciduous incisors
-increase in inter-canine width
-change in inter-incisal inclination or angulation ( from 150 degrees (deciduous incisor ) to 123 degrees in the permanent incisor
stable phase ( lasts for 1.5 years from 8-9.5 y) in which the maxillary and mandibular arches consist of sets of deciduoud and permanent teeth :
inter-transitional period
second transitional period is from :
age 9-10. includes shedding of primary C,D,E till emergance of permanent 3,4,5,7
-usual sequence
: maxilla:
-4-3-5 or 4-5-3
:mandible:
3-4-5
establishment of occlusion occurs in which stage ?
second transitional period
how is the dental arch affected in second transitional period?
its length is reduced just prior to eruption of 2nd molar by mesial eruptive forces
leeway space:
difference of mesiodistal thickness between primary canines , primary first and second molars and permanent canine , and premolars ( primary is less thick )
leeway space of upper arch and of lower arch :
maxillary :0.9mm
mandibular: 1.7 mm
how is the leeway space utalized?
Some of this Leeway space is taken by the distal movement of the larger permanent canine falling into the primate space, while other part is utilized by the late mesial shift of the mandibular molars in order to establish a normal molar relationship.
when does the ugly duckling stage occur?
8-9 years
why does the ugly duckling stage occur?
erupting canines impinge on roots of lateral incisors causing them to flare and causing a mild diastema ( less than 3mm , no intervention required ) it is a self correcting anomaly
