anatomical considerations - primary impressions Flashcards
How are complete dentures made?
Denture construction
Denture provision
How are dentures constructed?
Primary and secondary impressions during visits 1 and 2
Registration and wax try-in during visits 3 and 4
What happens during denture construction?
Shape of edentulous ridges recorded
Correct placement of teeth established - inter-ridge relationships
Wax template made
Template converted to acrylic denture
How is the correct placement of teeth established?
Occlusal registration blocks are placed in situ
They are mounted in centric relation on articulator
How are dentures provided?
Fit stage and review during visits 5 and 6
6-12 months post fit review
Where should the dentures extend to?
1-2mm in front of the fovae palatini
What are the fovae palatini?
Two small indentations at the junction at the hard and soft palate
What is denture candidiasis?
Red and speckled palate often due to wearing dentures at night
What are the hamular notches?
Formed at junction of maxilla and hamular process of the sphenoid bone
Where should the back of the maxillary dentures go on the lateral sides?
Hamular notches
What happens if you don’t mold the hamular notches properly?
May lead to soreness and loss of retention
What structures need to be molded properly?
Hamular notches
Prominent frenae
Full depth of labial and buccal sulci
What is the relevance of the middle frenum?
Key reference point for impression taking
What impact would a shallower sulcus have on a denture?
More lateral movement
What is the relevance of the large frenae in the canine region?
Insertion into crest of ridge may reduce retention of maxillary denture
What is the relevance of the incisive papilla?
Key reference point for maxillary incisors
Mean distance between IP and incisor is ~12mm
What is the relevance of the retromolar pads?
Key reference point for posterior border of mandibular border
Denture should cover just over half of this
What is the relevance of the mylohyoid ridge?
Key reference point for lingual border of mandibular denture
What is the relevance of the external oblique ridge?
Key reference point for buccal border of mandibular denture
What is the relevance of the lingual gingival remnant?
Usually on newly edentulous patients
Indicates where to place teeth
What is the relevance of the lingual frenum?
Key reference point
Move tongue side to side and forward during impressions
What is the relevance of the genial tubercles?
Bony extentions
If denture rocks on this as jaw resorbs and ridge gets smaller may be traumatic
What is the relevance of the insertion of mentalis?
May be uncomfortable for dentures to rock on as jaw resorbs and ridge gets smaller
What is the relevance of the mental foramen?
Mental nerve may get trapped as the jaw resorbs and ridge gets smaller
Shooting pains
How is informed consent gained?
Explain who you are Carry out initial assessment for notes Diagnosis and prognosis Explain no of visits and treatment Propose changes, benefits and risks Ask if they understand and if any Qs Clearly document
What is the initial assessment?
Reason for attending
Med/social/dental history
Observations from oral examination
What should be said on subsequent visits?
Explain today’s treatment
Ask if understood and any Qs
Reestablish objectives of treatment
Write up notes
What are the ideal properties of impression materials?
Accuracy
Resolution
Dimensional stability
Rigid or elastic
Why do we use alginate?
Simple, cheap, bonded to tray with adhesive, viscous during placement, elastic when set
HOWEVER, unstable if not cast up quickly
What is the problem with stock trays?
Impression material may debond if large undercuts present
How do you select your stock tray?
If the medium tray doesn’t fit, use a small or large
Use callipers to take inter hamular notch width of patients old dentures
Why might a greenstick be used?
If the stock tray doesn’t fit properly, they can be adapted with this
How do you use greenstick?
Very hot water softens this and it’s good to add to retromolar pads and palate
Why and how do you apply adhesive to the tray?
To hold the material in the tray when removing
Apply copiously and leave for 5 mins before impression
Where do you stand when taking an upper impression?
Behind right shoulder
Maxilla at your elbow
Where do you stand when taking a lower impression?
In front
Mandible at your elbow
What should be happening as the impression material is setting?
Apply traction to the cheeks
Get the patient to do functional movements with lips and cheeks
How do you get finer detail on the impression?
Trim peripheral excess so 1-2mm short of functional sulcus depth
Relieve frenae
What should you do if the alginate debonds?
Retake
How do you mark your impression as an indication for the special trays?
Use an indelible pencil to mark 1-2mm inside the depth of the periphery
Why might old good dentures be useful?
Provide an alginate for lab to cast up
Gives indication of how denture looks
Helps to select mold of teeth
Shows diastimer or crossover of teeth
What instructions should you give to the lab?
What material for second impression What tray is needed Eg. Non perforated close fitting special tray for zinc oxide Patient sticker Date and signature
How do you reduce the risk of cross infection?
Immerse the impressions in perform for 10 mins
Must be clearly documented
How are the impressions made?
Stock tray for an alginate primary
Special tray for zinc oxide-eugenol secondary
