Intro to masticatory systems Flashcards
Functional disturbances of masticatory system include:
- swallowing habits (ex. tongue thrusting)
- chewing patterns
- Bruxism (clenching and grinding)
Causes of open bite
- faulty postural performance of the associated musculature
- digit sucking habits
- tongue thrusting
- Obstructed Nasorespiratory function
- unfavorable growth patterns
- imbalances between occlusal and eruptive forces
Condyle inclination throughout the lifetime
As patient ages, the condylar inclanation increases to about 20-30 degrees. As children, it is FLAT and thus easier to move around. At old age, condyle is flat once again
____ is static, while ___ is dynamic
OCCLUSION is static, hie articulation is DYNAMIC
Define occlusion
static.
relationship between Mx and Md teeth in contact
Define articulation
- dynamic
- relationship of teeth to their antagonists during mandibular movements (eg. mastication)
Each primary tooth occludes with 2 teeth in the opposite arch, except for:
Primary Mc central incisors
Primary Mx 2nd molars
The relationship of the 2nd primary mx molar to 2nd primary md molar indicates what?
future positioning of permanent molars. Flush - (distal of mx and md 2nd molars line up in a straight line) indicates development of class I molar relationship in permanent dentition Distal step - (distal border of mx 2nd molar is mesial to the distal border of the md 2nd molar) indicates dev. of class II Mesial step - (distal border of mx 2nd molar is distal to md 2nd molar) indicates class III
Why is spacing in permanent dentition important?
in order to accommodate the permanent dentition
Primate space:
-exists in Mx and Md anterior segment
-Md: distal to primary canines
Ms: mesial to primary canines
Leeway space:
Space difference between total mesiodistal width of primary molars and total mesiodistal width of permanent premolars
-sum of M-D premolars < sum of M-D primary molars
molar class I occlusion
-Describes posterior segment
MB cusp of Mx 1st M interdigitates with B groove of Md 1st M
canine class I
- describes anterior segment
- cusp of Mx canine interdigitates between Md canine and Md 1st PM
Class II malocclusion
Md arch is DISTAL to idea position of the Mx arch by at least 1/2 cusp
Div 1: proclined Mx laterals
Div 2: retroclined Mx laterals
Class III
Md arch is MESIAL to the ideal position of Mx arch by at least 1/2 a cusp
-Associated with anterior and/or posterior crossbite
Anterior crossbite
“underbite”
-Mx anteror teeth occlude lingual to mandibular anterior teeth
Posterior crossbite
Buccal cusp tips of Mx posterior contact Md posterior teeth
-transverse discrepancy between Mx arch width and Md arch width
Goals of good occlusion
- optimal function
- absence of disease
Ideal dental arch form
U shaped
Ideal incisal relationship
correct overjet: about 2mm
Correct overbite: 20-30% of cervicoincisal length of Md incisor
Teeth should follow curve of _____ anterioposteriorly, and curve of ____ mediolaterally
Teeth should follow curve of SPEE anterioposteriorly, and curve of WILSON mediolaterally
3 arch form shapes
square, tapered (towards anterior), ovoid
Overjet vs overbite
Overjet: horizontal overlap.
Overbite: vertical overlap
Negative percentage of overbite indicates
an open bite
overbite value of or close to 100% is called
deep (impinging) bite
Causes for deep bite maloclussions
- overeruption of the Mx incisor
- incisor angulation
- excessive overjet
- undereruption of the molars
- Md ramus height
- Failure of natural eruption
prolonged thumb sucking can lead to
anterior open bite due to negative pressure created within the mouth
In an ideal occlusal scheme, occlusal forces would be borne predominantly by ____ teeth
posterior
Supporting or centric holding cusps
lingual cusps of Mx posterior teeth
-buccal cusps of Md posterior teeth
(when teeth are in normal alignment)
Non-supporting or non-centric holding cusps
Buccal cusps of Mx posterior teeth and lingual cusps of Md posterior teeth
