OCS Chap 3 TMJ Flashcards
mm involved in elevation (closing)
masseter, temporalis, medial pterygoid, superior fibers of lateral pterygoid (stabilize the disc)
mm involved in depression (opening)
inferior fibers of lateral pterygoid, suprahyoids, infrahyoids (indirectly)
mm involved in protrusion
superficial masseter, medial pterygoid, lateral pterygoid
mm involved in retrusion
deep fibers of masseter, temporalis, suprahyoids (digastrics)
lateral excursion
ipsilateral temporalis and masseter, contralateral medial and lateral pterygoids
normal amount of depression
40 to 45 mm for males
45 to 50 mm for females (4 fingers width)
functional is 35 mm or 3 fingers width
depression arthrokinematics
early phase depression - anterior rotation of condylar head in the inferior joint cavity
late phase superior cavity - anterior translation of the disk and the condylar head along the articular eminence
opposite for elevation
protrusion arthrokinematics
mandibular condyle (head) and disk translate anteriorly and inferiorly
opposite for retrusion
lateral excursion arthrokinematics
spinning of the ipsilateral condyle and horizontal anterior translation of the contralateral condyle
anterior disk displacement with reduction (ADDwR)
disk rests in front of the condylar head while the mouth is closed
during opening the disk reduces back,
during closing the disk moves posteriorly until it cant causing a second click (reciprocal clicks)
anterior disk displacement without reduction (ADDwoR)
disk may stay displaced in front of the condyle throughout the movement of mouth opening and closing, due to a progressive decrease in elasticity of the posterior stratum fibers
no clicks
may limit mouth opening (if the disk is blocking full anterior translation) or no limitation (if the disk is completely displaced anteriorly)
posterior disk displacement
rare
occurs after wide opening of the mouth
lateral pterygoid mm is overly stretched
demo open-lock (inability to close mouth)
orthognathia
branch of oral medicine dealing with the cause and treatment of malposition of the bones of the jaw
stomatognathic system
structure of the mouth, teeth, jaw and associated soft tissues
overbite
measure by the portion of the mandibular central incisors that is covered by the maxillary central incisors when the mandible is in its maximally occluded position
overjet
horizontal distance between the maxillary arch and the mandibular arch
normal value is 3 to 6mm
lateral excursion
horizontal distance between the dividing lines of the mandibular central incisors and the maxillary central incisors measured by asking the patient to move the mandible to one side
normal lateral excursion is 25% of the amount of mouth opening
C curve indicates
capsular pattern
S curve indicates
poor motor control or asymmetry of condylar head rotation or translation in an individual w/ ADDwR
deflection
indicated that during opening of the mouth, the mandible deflects to one side w/o returning to the central position at the end of mouth opening (pt w/ ADDwoR)
also occur due to capsular restriction or unilateral hypomobility (deflection towards ipsilateral side)
occulsion
functional relationship between the maxillary teeth and the mandibular teeth
Class 1 occulsion
normal teeth alignment
Class 2 occulsion
excessive overjet of more than 6 mm
Class 3 occulsion
mandibular arch protrudes in front of the maxillary arch (underbit)