complete dentures Flashcards
What does alveolar resorption involve?
Magnitude Site and pattern Time relations Influencing factors Problems
What is the magnitude of resorption in mandible compared to the maxilla?
4x greater in the mandible than the maxilla
How does the residual ridge change as a result of mandibular resorption?
More lingually placed anteriorly More buccally placed posteriorly In at the front and out at the back Labial plate is weaker in front Lingual plate is weaker in back
Where should mandibular denture teeth be placed in relation to the residual ridge?
Lower anteriors- on or slightly ahead
Canines and premolars- on
First molar- on or just inside
Second molar- on or just outside
How does the residual ridge change as a result of maxillary resorption?
More palatial in all regions
Where should maxillary denture teeth be placed in relation to the residual ridge?
All slightly buccally/labially rather than on
How quick is mandibular resorption over time?
Rapid bone resorption initially when teeth are taken out which then slows over time Eg. 2.5mm in 4 months 3.5mm in 8 months 4mm in 12 months 4.25mm in 16 months
What influences the rate of resorption?
Systemic=quicker eg. Osteoporosis
Local=slower eg. Retained roots and implants preserve bone
Denture induced=quicker (limited evidence)
What are the benefits of retained roots and artificial implants?
They preserve the bone around them so the dentures are more stable
What is the ‘neutral zone’?
The teeth are placed in balance so that the forces of the tongue and cheek work together to keep the dentures in place
What are immediate dentures?
Relates to rapid initial resorption
What should happen if the patient has a class 3 molar occlusion?
Lower molar teeth must be placed correctly over the ridge
May have to allow cross-bite for aesthetic purposes
Why might patients get a molar crossbite?
Often due to the palatial resorption of maxilla and buccal change of mandible- resorptive pattern
How might the mucosa be affected by bone resorption?
It might get compressed between the denture base and the sharp bone ridges leading to pain
How might the mental nerve be affected by bone resorption?
May become compressed leading to shooting pain or numbness and paresthesia
What happens if there is irregular resorption?
The mucosa might become sandwiched between sharp bony spicules and the denture base- painful
How might the patients appearance be affected?
Lack of support of soft tissues may lead to angular cheilitis (fungal infection at corners of mouth) and ages patient significantly
What kind of impression would you do with a ridge with minimal/without undercuts?
Rigid impression material in close fitting special tray
What kind of impression would you do with a ridge with large undercuts?
Elastic impression material in spaced special tray
What is an undercut?
The area between the maximum bulbosity of the ridge compared to the deepest part of the sulcus beneath
The contour that would prevent the placement of a prosthesis
Why is zinc oxide-eugenol used?
Cheap, easy to modify and accurate
Mucostatic but if in non-spaced, non-perforated tray= mucocompressive
Sometimes used with one spacer
Mucostatic, two spacers and wide perforations in mild flabby areas
What does a close fitting special tray look like?
1-2mm short of final denture border
Minor to moderate undercuts
Mucocompressive impression
What does a spaced special tray look like?
Use alginate instead
2-3mm short of final denture border
Moderate to severe undercuts
Mucostatic impression
Why might you use tissue stops?
Use for anything but ZnO
Silicone- 1.5-2mm TS
Alginate- 3mm TS
Ask lab to create
For areas that are relatively noncompressive
Stops tray showing through if excessive pressure
