Occlusion Flashcards
define occlusion
the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues
what is the intercuspal position?
the complete intercuspation of the opposing teeth independent of the condylar position
sometimes referred to as the best fit of the teeth regardless of the condylar position
name two factors which can change the ICP
- extraction of teeth
-restorations
what is the retruded contact position?
guided occlusal relationship occurring at the most retruded position of the condyles in the joint cavities
define index teeth
contacting facets of teeth in the intercuspal position
what is the most reproducible position?
the RCP
when is the RCP used instead of the ICP?
when there is not enough index teeth and there is an unstable occlusion
is it easier to change or conform to the existing occlusion?
conform to
when would you conform to the existing occlusion?
- works best in stable occlusion with sufficient index teeth
- usually use ICP
- ensure the prosthesis doesn’t alter the occlusion
when would you change the existing occlusion?
- often when the occlusion is unstable and there is a lack of sufficient index teeth
-usually more challenging to record occlusion
-often use RCP
how do we record occlusion?
using articulated study casts and an interocclusal record
give 3 examples of interocclusal records
-bite registration paste
- a wax wafer using modelling wax
- a modified wax wafer e.g. alminax
how do we record occlusion when there is a lack of index teeth?
record blocks
would the RCP always be used for edentulous patients?
- exam answer yes
- clinic answer no
how would you know that the OVD is not being changed at the jaw registration stage for partials?
the index teeth still bite together
why is it a good thing if you can see through the wax wafer after recording the occlusion?
thick wax would adjust the OVD
name 4 factors influencing the positions and movements of the mandible
-the muscles of mastication
-the neural feedback pathways
-the temporomandibular joints
- the shape of the occluding surfaces of the teeth
what is the envelope of motion?
a relatively small space in which the occlusion is achieved during normal functional mandibular movements such as swallowing and chewing
what are abnormal movements in the envelope of motion caused by?
derangement of the articular disc and muscle hypertrophy
give 4 examples of parafunctional activity
-bruxism
-clenching
-jaw posturing
- lip/pencil biting
give 4 consequences of parafunctional activity
-fractured cusps or restorations
-Increased tooth mobility
- muscle fatigue
-tooth wear
what is Posselt’s envelope?
represents the movement of the tip of the lower incisor when viewed in sagittal or frontal plane
what is the name given to the mandible intitally opening with a hinge movement about a horizontal axis
the retruded Aix/terminal hinge axis
what is the most superior position of the condyles in their fossae?
the retruded position
is the retruded position clinically reproducible in dentate or edentulous patients?
both
how big is the discrepancy between the RCP and ICP?
up to 1mm
how big should the freeway space be?
2-4mm
what is the occlusal vertical dimension?
measurement of face height when the teeth are in the intercuspal position
what determines the path of mandibular teeth moving from ICP to maximum protrusion?
the articulating surfaces of anterior teeth (anterior guidance)
what determines the path of mandibular teeth moving from ICP to maximum protrusion in patients with anterior open bites or edge-to-edge incisor relationships?
the occlusal surfaces of posterior teeth
what determines the angle and length and movement of teeth from ICP to maximum protrusion
the incisor relationship
describe the movement from ICP to maximum protrusion in patients who are class II division 2
the movement is almost vertical as the lower incisors are locked palatal to the upper incisors and cannot slide forward
what maintains ICP and directs occlusal forces axially?
- palatal cusps of maxillary teeth
- buccal cusps of mandibular teeth
(supporting cusps)
what do supporting cusps contact?
inclined planes of opposing dentition
or
cusp tips contact the opposing fossae
during lateral excursions, what is the working side and what is the non-working side?
WS- the side to which the mandible moves
NWS- the opposite side
what is the difference between canine guidance and group function?
CG- during lateral excursion, only the canines on the working side contact
GF- during lateral excursion, two or more pairs of teeth contact on the working side
describe how the mandible moves from RCP to maximum opening
-rotates around the THA in an arc of a circle to the point Y
- the condyles translate/slide downwards and forwards along the articulator eminencies of the glenoid fosse to the point of maximum opening
what is the Bennett movement?
condylar movements on the working side in the horizontal plane
what is the Bennett angle?
the angle between the non-working side and the sagittal plane during lateral excursion of the mandible
how big is the Bennett angle on average?
16o
ranges from 2-44
how do you locate the RCP?
- pt in supine position with chin pointed upwards
- stand behind pt and place thumbs on chin and fingers on lower border of mandible
-use gentle manipulation to move the pt into RCP
name 4 types of articulator
-simple hinge
- average value
- semi-adjustable
- fully adjustable
what movements does a simple hinge articulator allow?
rotational movements only
around horizontal axis
what movements does an average value articulator allow?
a limited range of protrusive and lateral movements based through a fixed condylar guidance mechanism
what are the two types of semi-adjustable articulator?
-arcon
-non-arcon
