Reinforcing Occlusal Rim Stage and Selecting Teeth for Complete Dentures Flashcards
What are acrylic base plates made from?
Heat cure acrylic resin with wax rim on top
What are acrylic base plates more rigid than?
Wax on a wax base
When is it more comfortable and less likely for occlusal rims to be displaced?
When base plates are carved to final shape of denture base
What enables jaw relation registration to be measured more easily?
When base plates are carved to final shape of denture base
What creates a raised area on denture base which creates a posterior seal/post dam?
Either a groove is cut into palate of master cast/area is compressed during impression taking?
What does depth of occlusal rim depend on?
Compressibility and is therefore a clinical decision
What is mucosa in midline?
Less compressible
When is retention for complete dentures with acrylic bases checked and corrected?
At jaw relation stage
What is it worth bearing in mind that problems with retention may be due to?
Denture bases
What does under-extension require?
New impression
What does inadequate width of flange require?
New impression
What does ineffective seal at posterior border require?
Adjust/new impression
What does poor fir of denture base require?
Adjust/new impression
What does over extension require?
Often seen if denture does not seat; adjustment
What is vertical dimension checked by?
A Willis bite gauge/calipers, with dots on nose and chin/by assessing closest speaking space of 1mm
What are the steps in checking vertical dimension?
Measure RVD first without blocks in place, ensure patient fully relaxed, repeat measures
What will give a better guide of vertical dimension?
Use of more than one method
What is checked with upper occlusal wax rim?
Lip and cheek support and neutral zone
How is labial contour of upper wax rim first restored?
By modifying maxillary wax block to a 90 degree angle between philtrum and columella/102-116 degrees
What are buccal corridors shaped to support?
Cheeks
What is rim slightly buccal to?
Ridge normally, as a result of resorption
Where is anterior occlusal plane registered for upper occlusal rim?
Usually 2-3mm below relaxed level of upper lip parallel to intra-pupillary line
What is checked with upper occlusal wax rim?
Lip and cheek support and neutral zone
How is upper block trimmed posteriorly?
By continuing anterior occlusal plane level posteriorly in a line paralell to ala-tragus line
What is a Foxes occlusal plane indicator/disposable wooden spatula used for?
To establish orientation and level of occlusal plane and produce correct shape for labial, buccal and palatal surfaces
What guides position of upper incisors using biometric guidelines?
Shape labial surface of upper rim
What is checked for lower rim?
Buccal labial and lingual surfaces and neutral zone
Why check space for lips, cheeks and tongue?
To ensure rim in neutral zone
What is orientation of occlusion governed by?
Upper rim
What is lower block trimmed until?
Rims contact evenly and at correct OVD
When may upper rim need further adjustment?
If lower rim will be too high (instability)/too low (no space for teeth)
What other checks to carry out once rims adjusted?
Check RVD again with rims in place, check facial proportions, get patient to talk..do rims hit, previous dentures can be helpful to establish OVD too
What is jaw relation registration?
Even occlusal contact between rims at chosen OVD whilst mandible is in CR
How is jaw relation registration checked?
Patient is relaxed and lower jaw is gently manipulated into CR
What is final registration taken using?
A bite registration paste/alternative
What other methods of registration of wax rims in occlusion?
Contact and softened wax/contact and fluid material
How are wax rims in occlusion registered with contact and fluid material?
Ensure wax blocks are at correct VDO and then record JRR with fluid material without heating up wax again
What may contact and softened wax loose?
Vertical height
Where is midline marked on block?
Usually in centre of philtrum but varies in caries of facial asymmetry
How are wax rims in occlusion registered with contact and fluid material?
Ensure wax blocks are at correct VDO and then record JRR with fluid material without heating up wax again
How is use of a facebow to record relationship of upper cast to skull useful in complex cases?
So that a cast may be set up on a semi-adjustable articulator and an accurate balanced articulation achieved
What may be useful as an alternative to wax occlusal rim?
A gothic arch tracing to measure position of CR and mandibular movement
What are the next steps?
Casts (registered with/without blocks) should be stable, they are disinfected and sent to technician with information about shades and moulds for setting up a trial of teeth, and teeth are selected for dentures
What is equation to calculate central incisor width?
Photographic width of incisor x actual PD/photographic PD
What is PD?
Interpupillary distance
What is height of tooth dependent on?
Height of smile
What should extension of denture base correspond to?
Depth and width of extension of sulci (in upper to post dam and in lower to pear shape pads)
What will extension of denture base do?
Distribute force and allow adjacent musculature to aid stability and retention
What is extension if we have acrylic baseplates?
These were adjusted at previous stage to ensure a comfortable fit and good jaw relation
What is extension if we have wax-based rims?
Wax may have been added in lab and we therefore may need to adjust this again to ensure bases are fitting comfortably first
How check tooth positioning of lower teeth?
Posteriorly should generally be positioned around crest of mandibular ridge
When is lower teeth position and whether they are in neutral zone more easily judged?
At clinical try in stage by dentist
How check tooth positioning of upper teeth?
Should follow biometric principles using wax occlusal rim at jaw relation registration stage, consider skeletal base
What are teeth generally set in?
Neutral zone, balanced between tongue and cheek to aid denture stability
What is neutral zone very important for?
Lower denture where less surface area of denture bases
When was neutral zone defined?
At occlusal rim tage
What is there is space between buccal surfaces of posterior teeth and cheek mucosa?
There may be inadequate tongue space
What can be challenging anteriorly?
Mentalis muscle
What should occlusion be with complete dentures/partials with no natural teeth in occlusion?
Should be balancing contacts in dynamic occlusion to help keep dentures stable
What should occlusion be in partial dentures where we are conforming?
Check to ensure that occlusion of natural teeth with and without dentures in place is same
What if error not obvious with occlusion?
Stabilises both bases left finger and thumb hold upper up and lower dentures in place, while right thumb and finger gently guide on chin
What should first contact not be on?
One/a few teeth but there should be widespread contacts around arch
What if teeth close from ‘first touch’ to ‘all way’?
If it is more than a couple of mm movement, then redo jaw relationship
How look at occlusion when patient grinds teeth?
This can be assessed more easily on articulator, but ask patient to gently grind their dentures
What bear in mind when look at occlusion when patient grinds teeth?
Some of teeth may pop out of wax
How is occlusal height re-checked?
Reassess RVD, OVD and FWS
How are RVD, OVD and FWS reassessed?
Observe facial appearance, observe movement of lips, cheeks and tongue and movement of dentures, and phonetics
What if OVD is too small?
Can add wax to teeth and may be able to retake JRR at this appointment
What if OVD is too large?
Need to remove teeth
What does correcting OVD depend on?
Aesthetics, amount of FWS needed, and ffect of increased OVD on tongue position (for lower teeth)
What if OVD is too small due to an asymmetrical vertical error?
More wax can be added to one side of arch and jaw relation re-recorded in CR to ensure balanced occlusion, then jaw relation registration is retaken in CR
What is useful to assess yourself in clinician and patient assessment?
Shape, mould, size of teeth, level of occlusal plane, orientation of occlusal plane, centre line, and lip support
What use floss to confirm?
Dental midline in alignment with facial contours
What is proportion between upper/lower and anterior/posterior teeth?
Upper front teeth are ‘subject’, and gingiva, inter-arch space, and lower teeth are ‘background’
What is an occlusal plane issue?
Negative smile line not in harmony with soft tissues
How is negative smile line not in harmony with soft tissues corrected?
Identify facial landmarks and lines to which smile will blend
What will make dentition appear more natural?
Having some irregularity and crowding
What should irregularity be balanced across?
Arch
What can create a realistic appearance relative to age?
Selective grinding to create incisal wear and darker teeth
What should be considered for denture characterisation?
Small spaces, a gold inlay, a clasp, silver amalgam restorations, gold inlay, irregular teeth arrangement, and chipped teeth
What are errors at try in stage?
Appearance incorrect and occlusal error e.g., premature contacts and/or teeth are not occluding same on model as in mouth
What may small changes be corrected by?
Adjusting/moving teeth at chairside/on articulated casts
What should larger changes be?
Remounted in laboratory; new tooth position and repeat try in, in wax/repeat occlusal rim, jaw relation stage with/without anterior teeth in situ
