Mastication and occlusion: anatomical factors Flashcards
5 functions of mastication
- enables food bolus to be swallowed easily
- enhances digestibility of food (maybe. increase SA for enzymes & reflex stimulation of digestive juices)
- mixes food with saliva and salivary amylase
- prevents irritation of GI tract by large food masses
- ensures healthy growth and development of oral tissues
muscles of mastication table
6 components of craniomandibular articulation for mastication
- bones (1 mandible, 2 temporals)
- synovial joint (fibrocartilaginous) + capsules + disc (ginglymo-arthroidal = sliding hinge joint)
- muscles of mastication
- ligaments
- innervation
- teeth
where does TMJ sit in skull
glenoid fossa
5 types of movement made by the jaw muscles
elevation depression retraction protrusion lateral excursion
the muscles for which movement are v weak?
depressors
which muscles run through infratemporal fossa
medial and lateral pterygoid muscles
what limits range of movement of muscles 3
COL
- contour of bony surfaces
- occlusal surfaces of teeth
- ligaments
name/explain 4 ligaments (label on diagram)
- temporomandibular (thickening of lateral side of capsule)
- pterygomandibular(raphe. where buccinator muscle meets mm going to pharynx)
- sphenomandibular (sphenoid bone - lingula
- stylomandibular (thickening of investing layer of deep cervical fascia)
where/ how is tmj innervated
disc itself and fibrous tissue lack blood/ nerve supply
–> posterior capsule and periphery innervated by auriculo-temporal nerve and branch to masseter
5 elements of inflammation
rubor (red) calor (heat) dolor (pain) tumor (swelling) loss of function
explain why tmj problems often seem like ear problems
auriculo-temporal nerve supplies skin of temple, EAM, tympanic membrane
4 parts of ideal occlusion
- teeth aligned so masticatory loads are within physiological range and act through long axes of as many teeth as possible
- lateral jaw movements occur without undue mechanical interference
- in rest position the freeway space is comfortable functional for the individual concerned
- tooth alignment is aesthetically pleasing to pt
what is the relationship of the cusps in ideal occlusion
functional cusps overlap:
Palatal upper cusps in to lower fossae
Buccal lower cusps in to upper fossae
explain BULL rule
when adjusting dentures, only adjust non-functional cusps:
buccal cusp of uppers
lingual cusp of lowers
explain curve of spee
from SIDE:
curve that allows there to still be occlusion during protrusion of mandible
explain curve of wilson/ sphere of monson
curve laterally- so teeth stay in occlusion during lateral excursion
what is the neutral zone
spaces around teeth which teeth can be forced in to by excessive force by muscles eg tongue/ cheeks
what are occlusal stops
points on teeth which stop excess movement of teeth
3 locations of occlusal stops
centric
protrusive
lateral excursion
what is used to measure freeway space
willis gauge
*draw and label TMJ* attachments of TMJ capsule: a. superior b. inferior c. anterior d. posterior
a. superior: temporal bone
b. inferior: condyle
c. anterior: articular eminence (temporal bone)
d. posterior: squamotympanic fissure
where do all parts of the capsule attach to?
glenoid fossa (temporal bone)
which parts of tmj capsule attach to the disc
medially, laterally and posteriorly (NOT anteriorly- superior part of lat pterygoid muscle attaches here)
describe attachment between capsule and surrounding areas
villi filled with synovial fluid
type of material capsule is and why
fibrocartilage membrane
because it is formed in a membrane so is not hyaline cartilage
how is the TMJ innervated
avascular and no nerve supply. therefore supplied by diffusion through synovial fluid from auriculotemporal nerve
what suspends the mandible
muscles of mastication, ligaments
