Occlusion for partial dentures Flashcards
ILO 2.6a: be familiar with the design and choice of materials used in the production of partial dentures, along with knowledge of laboratory procedures
what is occlusion?
the static relationship between the incising or masticating surfaces of the maxillary and mandibular teeth or tooth analogues
how should partial dentures affect the occlusion?
- partial dentures should work in harmony with the patient’s existing occlusion
- the existing occlusion should not be changed unless you have already planned to change it
- conform to the occlusion, don’t change it
why do you need to record the occlusion?
- need to know the patient’s existing occlusion so you can conform to it
- facilitates denture design
- helps technician mount casts and set up teeth
- ensure the denture is stable and is not dislodged in function
- important if planning to change the occlusion
- need to know the position of the teeth in relation to each other
- ensure loading forces are applied correctly to teeth and underlying mucosa/bone
when do you record the occlusion?
- primary registration
- secondary registration
- framework registration
when do you need to record occlusion in the primary registration stage?
- when casts cannot be hand articulated and you need to determine occlusion to design the denture and position rest seats without occlusal interference
- after primary impression, before master impression and cast
when do you need to record occlusion in the secondary registration stage?
- when casts cannot be hand articulated
- if you plan to change the occlusion
- if replacing anterior teeth adn providing metal backings, a tooth trial is needed before the framework is constructed
- after master impression and master cast made
when do you need to record occlusion in the framework trial stage?
if conforming to occlusion, to ensure the framework does not interfere with occlusion
what are we aiming to establish when recording the occlusion?
- intercuspal relationship (ICR) to allow casts to be articulated and set up the teeth
- occlusal vertical dimension (OVD) - index teeth, re-organising occlusion
- buccal/labial contours of wax record blocks - lip support, incisal plane, occlusal plane
- tooth shade and mould
what are index teeth?
teeth that contact the intercuspal position (ICP) and allow easy recording of the OVD
* these teeth contacts should remain the same when the partial denture is in situ - conform to occlusion
what is the procedure when conforming to the occlusion?
- disinfect the record blocks in perform
- adjust the upper then lower record block
- record the occlusion
- check registration fits the casts
- disinfect record blocks
- select shade and mould
- send instructions to lab
what is the equipment for trimming the wax blocks?
- hot plate
- no flame
- wax knife
- bunsen burner and palate knife
how do you record the occlusion?
- wax block should have already been adjusted to conform to occlusion
- ensure the heels are not touching - if they touch it changes the occlusion
- join the blocks together using pink wax or registration paste
what is the procedure when not conforming to the occlusion?
- disinfect the record blocks in perform
- adjust the upper then lower record block
- record the occlusion
- check registration fits the casts
- disinfect record blocks
- select shade and mould
- send instructions to lab
same as if conforming to occlusion
what should you do if the patient does not have enough index teeth to find the occlusion?
- you need to decide the occlusion and OVD
- there may be stable tooth contacts when the mandible is in a retruded position
- if there is no stable tooth contacts when the mandible is protruded, you will have to determine the OVD and occlusion using record blocks
how do you change the OVD? when is this done?
- use record blocks to establish the OVD you want
- frequently done with patients with tooth wear using the Dahl principle - provides space for restorations and overeruption
- used if patients are over closed and have TMJ problems or persistent angular cheilitis - reduced creasing and pooling of saliva at commisures
should always be planned and not by accident
what is posselt’s envelope?
the position of teeth at different opening positions - the extremes of mandibular movement (border movements in the saggital plane)
* intercuspal position (ICP)
* retruded contact position (RCP)
* rotation of condyle (R)
* translation of condyle (T)
* protrusion (Pr)
* edge to edge incisal contact (E)
what position can be used when intercuspal position (ICP) us not possible due to no idex teeth?
centric relation / occlusion
* the comfortable bite
* the habitual bite
* the bite of convenience
* need to compare it to the retruded contact position
what is the retruded contact position?
- the first tooth contact when the condyle of the mandible is in a** retruded axis position**
- just behind the intercuspal position (ICP)
- mostly reproducible
what are the ways of recording the resting vertical dimension (RVD) and the occlusal vertical dimension (OVD)?
- two dot method
- Willis bit gauge
how do you record the resting vertical dimension (RVD) with the two dot method?
- choose point on nose and chin with minimal movement
- jaw relaxed, lips just touching, space between posterior teeth
- use dividers to measure distance between dots
- distance between divider arms = RVD
how do you record the resting vertical dimension (RVD) with the Willis bite gauge?
- jaw relaxed, lips just touching, space between posterior teeth
- fixed arm in the nasio labial position
- sliding arm under the chin
- distance between sliding and fixed arms = RVD
how do you record the occlusal vertical dimension (OVD) with the two dot method?
- choose point on nose and chin with minimal movement
- teeth in intercuspal position (ICP)
- use dividers to measure distance between dots
- distance between divider arms = RVD
how do you record the occlusal vertical dimension (OVD) with the Willis bite gauge?
- teeth in intercuspal position
- fixed arm in the nasio labial position
- sliding arm under the chin
- distance between sliding and fixed arms = RVD
what is free way space?
the space between the occluding surfaces of the maxillary and mandibular teeth when the mandible is in psychological resting position
* free way space = RVD - OVD = 2-4mm
how do you adjust the wax block when intercuspal position is not possible?
- adjust the upper occlusal rim
- the occlusal and incisal plane is appropriately oreintated in relation to the remaining upper natural teeth or the facial reference points
- if there is an anterior saddle, ensure the rim indicates the appropriate incisal level and degree of lip support
- adjust the lower occlusal rim
- no teeth will be touching as you are determining the OVD
- then record the occlusion
when writing the lab prescription, what do you want the lab to do with the work and what do you want back after the primary occlusion?
- want the lab to articulate the casts to occlusion recorded
- want to get back special trays with correct spacing for type of material used
when writing the lab prescription, what do you want the lab to do with the work and what do you want back after the secondary occlusion?
- want the lab to articulate the casts to occlusion recorded
- want to get back the try-in tray with wax
when wanting to change the OVD, what can you use instead?
- centric relation
- retruded contact position (RCP)
what is the difference between intercuspal position (ICP) and retruded contact position (RCP)?
intercuspal position (ICP)
* sufficient number of index teeth
* stable occlusion
* variable through life
* usually more anterior than RPC
* simpler to record the occlusion
retruded contact position (RCP)
* insufficient number of index teeth
* unstable occlusion
* reproducible position
* usually more posterior than ICP
* more challenging to record the occlusion
