occlusion videos Flashcards
occlusion is
dynamic relationship between teeth as the mandible goes through its functional movement
maxilla in occlusion
no movement
fixed to skull/ cranial base
frontal plane occlusal movemetns
shield shape
- mandible moves to working side
- mandible moves away from non working/ balancing side
overjet
horizontal overlap
overbite
vertical overlap
movement when chewing on left
- Mandible move to left
- Left has working movement
- Right has balancing/non working movement
- Side match movement direction – working movement*
- Side does not match movement direction – non working movement*
dots are centric stops
NW condyle movement
slides down the articular eminence
W condyle movement
rotates - centre of rotation for NW
protrusion movement of condyles
both condyles move forward and down articular eminence
occlusal grid
right side of mouth
mandible moves backward relative to maxilla moving forward
- Hence opposite directions
which cusp contacts where cursor is in static occlusion?
Firstly where are we
- Maxilla
- Left
- 26
so Mesial buccal cusp of 36
- (move distofacial of contact point and what it is – so distal margin ridge 26 -> mesial buccal 37)
- Lower move mesiollingual*
what movement does the blue arrow depict in dynamic occlusion?
Straight to buccal for maxilla
- Working movement
Left side of movement
- So left lateral excursive movement
how to use occlusal grid for
if the mandible is moving left, the buccal cusp of the right mandibular second premolar may contact what cusp?
contact 4 on lower
- Find 4 on upper to correspond
Mandible moving left but we have grid for right side
- Side does not match direction
- NW
Hit distobuccal surface of the lingual cusp of the maxillary first premolar
how to use occlusal grid for
In the right lateral excursion the ML cusp of the maxillary second molar passes through what structure?
Right side – working mvmt
Lingual groove mandibular second molar
how to use occlusal grid for
in a left non-working movement, the MB cusp of the right maxillary first molar will pass through what structure?
Mesial buccal not marked in so extrapolate
Non working on left is the right working and we are on right
- So working
Pass through mesial buccal mandibular first molar, central pit and groove
Alginate
irreversible hydrocolloid
- Material of choice for diagnostic casts
- Sodium or potassium salts of alginic acid which react chemically with calcium sulphate to produce insoluble calcium alginate
- Diatomaceous earth add strength
- Trisodium phosphate controls setting rate
- More bulk means less susceptibility to unwanted dimensional change
- 2-3 minutes -> remove tray
- Within 15 mins -> pour impression (in dental stone)
- 30-60 minutes -> casts set
casts
moulds of teeth in dental stone
maxillo-mandibular relations (MMR)
2 key
centric occlusion
maximum intercuspation(MI)/ centric occlusion
centric relation CR
- Position in which condyles articulate with the thinnest avascular portion in their respective discs in the most anterior-superior position against the articular eminences
- Disc – beige
- Condyle is constantly contact with
- Disc – beige
- Independent of teeth
maximum intercuspation MI/ centric occlusion
- Complete interdigitation of teeth
- Independent of condylar position
how often does MI and CR coincide
Coincide in only 10% of population
when are casts mounted in MI
Casts are mounted in MI when MI can be maintained (single fixed procedure)
- Can hand articulate
when are casts mounted in CR
- when MI is impossible to maintain (complete dentures, multiple teeth being restored or replaced) more reliable
- Cannot hand articulate
- Fully edentulous, free end saddles, malocclusions
- Cannot hand articulate
most reliable and reproducible jaw position of the mouth
CR
centric relation
occlusal harmony
want
Joint, muscles and teeth must function in harmony – like a jaw in its frame
- Hinges – TMJ
- Teeth – door and frame
- Maxilla - stationary – frame
- Mandible – moveable - door
- Handle – muscles
bimanual manipulation
one of the most accurate methods to obtain accurate CR interocclusal records
- with pt laying back, support the posterior mandible with fingers and chin with thumb
- deprogram the jaw
- condyles in most superior and anterior position and swing mandible until get one tooth contact
- deprogram the jaw
identify the first CR tooth contact and repeat until you identify a consistent first tooth contact
keep anterior teeth slightly apart in CR with leaf gauge or acrylic resin jig
- then take interocclusal record of posterior teeth with PVS (polyvinylsiloxane)
- permanent registration of relationship between upper and lower teeth - usually only posterior teeth captured so don’t have anterior
facebow record
Objective is to duplicate on the articulator the relationship of the maxillary arch to the skull and the mandible to the rotational centre of the TMJs that exists for that particular pt
- arbitrary facebow – orients maxillary cast to skull via external auditory meatus to stabilise the bow (less precise but more easy to use)
- kinematic facebow – placed on the hinge axis of the mandible (more complex)
transfers relationship of maxilla to rest of skull from pt to articulator
articulator components relation to anatomy
- upper member = maxilla
- lower member = mandible
- hinge axis = TMJ
interocclusal record - bite registration
transfer registration of maxilla and mandible
- facebow – to place maxilla
- bite reg – to place mandible
purpose of articulators, casts and interocclusal records
mounting physical representation of pt mouth outside the pt
nonadjustable articulator
- does not reproduce full range of mandibular movement – up and down alone
- distance between hinge and teeth is significant shorter than in the patient
- may result in premature contacts and incorrect ridge and groove direction of restorations
only v simple, everything in MI
semiadjustable articulator
allows you to set the Bennett angle (15o) and HCI (30o)
arcon = condyles are a part of the lower member, fossa are a part of the upper member
- mandible has condyle – anatomically accurate (picture)
nonarcon = upper and lower members are rigidly attached
HCI
HCI horizontal condylar inclination
- Vertical angle that condyles move as pt jaws function down articular eminence
30o
bennet angle
- Horizontal angle that condyle move as pt
15o
arcon semiadjustable articulator
condyles are a part of the lower member, fossa are a part of the upper member
mandible has condyle – anatomically accurate (picture)
non arcon semiadjustable articulator
- upper and lower members are rigidly attached
fully adjustable articulator
- pantograph is used to follow pt border movements
- rarely used
pouring casts from alginate
casts poured from alginate are more accurately mounted with wax records
pouring casts from elastomeric maaterials
casts poured from elastomeric materials are more accurately mounted with elastomeric materials (PVS) or ZOE paste
disclusion
imp in pros
- teeth are separating from one another in function
- protect the teeth from wear and occlusal force and trauma
2 guidance on protrusion of jaw forward
condylar guidance
incisal guidance
condylar guidance
on protrusion of jaw forward
- slope of articular eminence (can be shallow/steeper)
- represented by HCI on articular
- posterior determinant of occlusion
incisal guidance
on protrusion of jaw forward
- incisal edges of lower incisors against lingual slopes of upper incisors
- represented by a pin and guide table on articulator
- anterior determinant of occlusion
guidance in lateral movement
canine
canine guidance
- when lateral movements all posterior teeth are immediately discluded as contact occurs solely between upper and lower canine on the working side
anterior guidance refers to
both incisal and canine guidance
mutual protection occlusion
anterior guidance (incisal and canine)
during protrusive, incisal and condylar guidance provide clearance for all posterior teeth
during lateral, canines on working side and condyle on balancing side provide clearance for posterior teeth on balancing side (mandible moving away from)
guide table
use
anterior guidances must be preserved when restorative procedures change the surfaces of any ‘guiding teeth’
- e.g. full anterior crowns - true representation of natural occlusion
guide table
types
mechanical incisal guide tables insufficient information to reproduce lingual contours of maxillary anterior natural teeth
- lingual contours curved not straight
custom incisal guide table is made our of acrylic resin and provides this information
mutual protection
