Cranial nerves and foramina

Topics: Temporomandibular joint, Medial pterygoid muscle, Teeth Pages: 12 (1628 words) Published: October 11, 2013


Intraarch—prox contact betw teeth
tooth inclination: inclined to receive closing force along axes
occlusal plane curvature (Curves of Spee & Wilson)
Spee— anteroposterior
mand canine→along buccal cusp tips
affects posterior cusp height
**protects against protrusive interferences

Wilson—translateral curve
lingual inclination of mand posteriors
**protects against lateral interferences

Interarch—arch length: max and mand arches the same
arch width: max slightly > mand

Centric cusps—i.e. functional cusps: mand=buccal
fnxn: vertical dimension of occlusion (VDO)
support of facial height
aligned with opposing for mastication

Non-centric cusps—i.e. non-functional cusps: mand=lingual
fnxn: ↓tissue impingement
maintain bolus of food on occlusal table
mand stability in MI (max intercuspation)

some rules: (remember we’re speaking about the functional cusps only!)

mand mesial cusp occludes w/: max marg ridge
mand distal cusp occludes w/: max fossa
max mesial cusp occludes w/: mand central fossa
max distal cusp occludes w/: mand distal marg ridge

mand tooth# + max tooth # = 33 (to deduce which teeth are in occlusion)

mandibular movement pattern determined by: Anterior guidance & TMJ guidance

Groove rules:
1. Working grooves are at right angles to the central groove
2. Non-working grooves are usually oblique to the central groove
3. During protrusive mvmt, centric cusp usually moves parallel to central groove

Three axis of reference for mandibular mvmt:

1. Horizonal axis: occurs in sagittal plane
first 20-25 mm = pure rotation

2. Vertical axis: occurs in horizontal plane
lateral movements
doesn’t occur naturally

3. Sagittal axis: occurs in frontal plane
lateral movements
doesn’t occur naturally

2 types of condylar mvmt:

Rotational mvmt—first stage of opening
first 20-25 mm
occurs w/in inferior cavity of TMJ
fully or semi-adjustable articulator using facebow + CR interocclusal record

Tranlational mvmt—2nd stage of opening
moves down articular eminence while opening to max limit
occurs w/in superior cavity of TMJ
fully or semi adjustable articulator using a protrusive interocclusal record

*usually both mvmts occur simultaneously

TMJ—Fixed factor
influences movement of the post mandible
pathology & trauma can alter

Anterior guidance—Variable factor
influences mvmt of anterior mandible
altered by: pathology, trauma, and dental procedures
determined by exact positioning of anterior teeth

1. Vertical Overlap (VO): sagittal plane
↑ vertical overlap ↑longer post cusps may be
↓ vertical overlap ↓shorter post cusps must be
2. Horizontal Overlap (FHO): sagittal plane
.005-.5 mm = post cusps may be long
> .5 mm = post cusps must be short

Condylar guidance—eminentia angle: Fixed Factor
glenoid fossa anatomy: medial, superior, posterior walls
medial wall determines inward mvmt of orbiting condyle during lateral excursion
orbiting condyle: on non-working side
rotating condyle: on working side

↑divergence of two planes = post cusps may be longer
↑parallel the two planes = post cusps must be shorter

mandibular lateral translation (aka Bennett Movement)
if no well positioned canines, working & non working groove may be positioned as simple arcs with an apex in central groove, if no immediate side shift
if no well positioned canines, working & non working groove must be positioned more distally in the max arch and the central groove must be wider if no immediate side shift

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