OCCLUSION BLOCKS Flashcards
occlusion block is composed of :
-trial denture base ( base material which accurately fits cast)
-occlusion rim (arch shaped material occupying space of patients previous dentition
uses of occlusion blocks :
1.) record jaw (centric and eccentric) relation
2.) support lip structure
3.) orientation of occlusal plane
4.) providing matrix for arranging teeth
5.) selecting size and position of artificial teeth by aid of midline , highlip line , canine line
markings that help in selecting size and position of artificial teeth in occlusion blocks:
1.) midline
2.) high lip line
3.)canine line
trial denture base should be minimum thickness that allows for rigidity
examples of temporary trial denture bases
-shellec (thin plastic sheet, easily breaks )
-self cure and light cure acrylic resin (self cure can cause allergic reaction with excess monomer and light cure is susceptible to shrinkage )
-vacuum formed vinyl( difficult to trim and requires expensive equipment )
-baseplate wax (liable to deformation )
-swaged tin
examples of permanent trial denture bases ?
1.) metallic ( gold alloys and cobalt chromium alloys)
2.) non metallic : heat cured acrylic resin ( no shrinkage )
advantages of heat cured resin denture base :
1.) strong and rigid
2.) requires minimum finishing and polishing
3.) minimum dimensional changes during processing
disadvantages of heat cured resin denture base:
1.) time consming
2.) warpage due to 2nd processing attached to teeth
warpage of heat cured denture base during 2nd processing when attaching to acrylic teeth can be avoided by using ____
self curing acrylic resin
advantages of metal bases:
-no warpage , high strength and accuracy , less deformation in function
-hygienic (less tissue changes under base), easily kept clean
-good thermal conductivity
disadvantages of metal bases:
expensive
difficult relining (adding new layer)
time consuming
uses of trial denture base:
1,) carries occlusion rim where jaw relation will be recorded
2.) carries artificial teeth to help the try in stage
3.) checks the accuracy of the final impression
most common material used for occlusal rim:
wax
disadvantages of using wax for occlusion rim:
liable to distortion
inaccurate results in patients with heavy biting force
material other than wax used for occlusion rim :
modeling plastic / molding compound
disadvantages of using modeling compound for occlusion rim :
-takes longer time for trimming and adjustments
-residual pigments can be transferred from compound to final denture (brown)
maxillary rim measurments for
-anterior height:
-anterior width:
-posterior height :
-posterior width :
anterior height : 20-22mm
width:6-8mm
posterior height((shorter): 16-18mm
width(wider): 8-10mm
-wax is centralized over crest of ridge
-slightly labial inclination of the labial contour
mandibular rim measurements for posterior height :
2/3 way up the retromolar pad , if it was higher or lower then the patent might accidently bite huis tongue or the denture may be displaced
-no labial inclination
the vertical relation of the jaw includes:
-resting vertical dimension
-occlusal vertical dimention (under force)
-interocclusal rest space( freeway space)( difference between them) usually 2-4mm
horizontal jaw relations of the jaw:
-centric relation ( mandible is at middle of maxilla)
-maxmial inter-cuspal position (occlusion )
-eccentric relation (protrusion , left and right)
2 points from which vertical dimension is taken :
-above mouth at tip of nose
- below ,maximum convexity at chin
what are some short term variables that may affect resting vertical dimension measurements ?
- head position ( if head is positioned resting on its back then it will increase)
-respiration
stress (muscle contraction causes measurment to be less)
long term variables affecting resting vertical dimension measurement
-loss of proprioceptors( nerves in periodontium giving the patient spatial awareness in his mouth )—> measurment decrease
-old age –> measuurment decrease slightly
low vertical dimensions will result in :
- cheek and tongue biting (lower arch will end before the 2/3rd mark on retromolar buccal pad
-loss of biting force
- inharmonious facial proportions
-angular cheilitis (caused by pooling of saliva)
-TMJ disorder
high vertical dimentions will result in :
-difficulty in swallowing and speaking
-loss of biting power
-clicking of teeth
-inharmonious facial proportions
-seperated lips when face is at rest
-pain under basal seat, ulceration and inflamation under denture base
TMJ is also affected
what is meant by centric relation ?
- position at which mandible is most retracted while NOT being under strain, resting in its socket
centric relation is maintained by :
ligaments
what is centric occlusion ?
relation between upper and lower teeth when jaw is in centric relation ( doesn’t have to be maximum intercuspation as that is mostly not happening when centric occlusion is taking place )
