Removable prosthodontics (complete dentures) Flashcards
Name some key anatomical landmarks of the maxillary denture bearing area
-Labial frenum; over extension of denture can cause loosness -Incisive papilla; behind upper incisors but moves to alveolar ridge due to resorption -Tuberosity; utilised to aid retention -Hamular notch; f/- extends beyond for seal and suction -over extension leads to ulceration -Under extension leads to dropping
Name some key anatomical landmarks of the mandibular denture bearing area
-Lingual frenum; attaches tongue to alveolar ridge -Stability gained from mylohyoid ridge -Hamular notch; ideal site for distal border of denture. Helps with posterior seal -Retromolar pad; if denture extends to cover anterior two thirds, it provides support -Retromylohyoid space; retention and stability greatly increased if denture extends into this space
Describe the resorption patterns in the maxilla and mandible
-Upper; recedes up and back, width decreases -Lower; recedes down in a more vertical manner. Width increases -This is why f/f are often constructed in crossbite
What are the Cawood and Howell classifications of edentulous ridges?
i) Dentate
ii) Post extraction
iii) Broad alveolar process
vi) Knife edge
v) Flat ridge (no alveolar process)
iv) Submerged ridge (loss of basal bone)
Why does the alveolar bone reduce in edentulous patients and at what rate?
If there are no remaining teeth or roots, there is no remaining periodontium and therefore no means of retaining alveolar bone around teeth.
Maximum rate of bone loss is in the first three months, but bone loss continues over the lifetime of the patient
Define support
Resistance to vertical movement of the denture.
How well the underlying oral tissues, including mucosa, keeps the denture from moving vertically towards the arch and thus being excessively depressed and moving deeper into the arch.
What areas off the mandible and maxilla offer support for a full denture?
Mandible; buccal shelf, sesidual ridge, and retromolar pad
-Maxilla; hard palate, residual ridge
Define retention
Resistance to displacement in a vertical direction
Describe how retention is achieved
- Accurate fit of the denture base to the mucosa so that the space between the two is as small as possible.
- Border seal achieved by extending the denture flanges to the depth of the functional sulcusl.
- The borders of the denture should not interfere with the muscle or frenal attachments.
Define stability
Resistance to horizontal movement.
Place fingers on the occlusal surface and try to rock the denture side to side
Give some positives and negatives of using alginate in complete denture impressions
- Cheap
- Easy to use
- Can be messy
- Elastic
- Poor dimensional stability if stored dry, or wet for prolonged periods. Good if stored correctly
- Accurate (enough for dentures)
Give some positives and negatives for the use of impression compound in complete denture impressions
- Non-elastic
- Poor surface detail
- Not cheap
- Can be messy for operator
- Needs to be heated, could burn patient
- Can only be used for primary impressions
Name some similarities and differences between silicones and polyeither
SILICONE; dimensionally stable, hydrophobic, variety of consistencies, messy, very accurate
POLYETHER; dimensionally stable, hydrophilic (better), only medium body, messy, very accurate
Define what and impression is
A reverse or negative form of the tissues which is converted into a positive model/cast using plaster or stone
Describe the steps in how impression compound is used
- immerse in water bath at 55 ti 60 degrees for 4/5 minutes to ensure complete softening
- use gauze/paper towel at the bottom of the bath to prevent it sticking
- If you kneed it, water will be incorporated and act as a plasticiser
- If it is left too long it becomes difficult to handle and some of its constisuents may leach out, altering the material properties
- Use vaseline on gloves to prevent sticking
