PRS03 - Lecture 2 - Primary Impressions Flashcards
What are the 3 functions of a primary impressions?
To obtain a cast so that:
Correctly extended special trays can be constructed
A partial denture can be designed for the patient
What 7 things are needed for primary impressions?
Examination kit
Range of dentate stock trays
Silicone and alginate adhesives
Equal quantities of silicone putty base and catalyst
Alginate (+ mixing bowl, spatula, water measure)
Disposable scalpel
Gauze, bag for impressions + labratory prescription
What are the properties of an ideal stock tray? (3)
Fit in the mouth (small, medium or large)
Record all necessary land marks
May need to be modified (green stick composition or knife)
What anatomical structures needs to be recorded in the maxilla? (10)
Incisive papilla - small mass of fibrous tissue (behind upper incisors)
Palatine fovae - pair of mucous gland duct orificies near the midline of soft and hard palate
Palatine raphe - midline of palate
Palatal rugae - transverse ridges of the hard palate
Vibrating line - junction between the hard and soft palate
Hamular notch - junction of maxillary tuberosity and hamular process
Alveolar ridge
Frenum - fibrous tissue fold between lip and alveolus, found labially + buccally
Sulcus (labial and buccal)
Tuberosity
Why is the sublingual folds important when taking impressions?
Avoid trapping the folds because it can reduce the depth and width of the lingual sulcus
What anatomical structures needs to be recorded in the mandible? (9)
(memorise diagram)
Retromolar pad - mass of non-keratinised glandular tissue (posterior to third molars
Pear-shaped pad - anterior to retromolar pad
Retromylohyoid fossa/papilla (lingual pouch) - fossa on lateral wall of the lingual sulcus (posterior to mylohyoid muscle)
Buccal shelf - surface between residual and external oblique ridges
Mylohyoid ridge - bony ridge where mylohyoid muscle is attached
Sublingual folds - folds of floor of mouth (site of sublingual gland)
Sulcus
Frenum
Extermal oblique ridge (Alveolar ridge?)
Why is the vibrating line important for upper dentures?
Full palatal coverage should be just anterior to it
What should be done prior to mixing the impression material? (3)
1) Explain the procedure to the patient
2) Put chair in correct position
3) Apply silicone adhesives to relevant areas of the tray (vault of palate, distal extension saddles, long bounded saddles)
Describe the clinical steps of primary impression taking (6 - detailed)
1) Ensure you and patient are in the correct positions
Lowers - stand infront of patient
Uppers - stand behind patient (chair should be lower)
2) Use silicone putty and adhesive
Mix putty using non-latex gloves
Place in areas of the stock tray where there are no teeth (saddles)
For uppers - place putty in the palatal vault (especially if high)
Once set - remove the tray
Trim 1-2mm off rolled border, removing undercuts and trim away from teeth (giving ~4mm clearance)
3) Use alginate + alginate adhesive
Mix alginate with water (3:1)
Apply alginate adhesive -> tray + over putty
Place alginate over tray + thin layer on the putty
4) Place the tray with alginate into patients mouth
Ensure frenal notch of tray aligns with the labial frenum
For lowers - ask patient to raise (so it doesnt get trapped in lingual flange) and protrude tongue
Mould the borders + massage excess material into the sulci
5) Disinfection
Disinfect in preform for 10mins + rinse
Wrap in wet agauze + place in bag
6) Write prescription -
Make cast impression, special trays and wire-reinforced wax base + occlusal rims (for premilary jaw reg)
How will you manage patients that gag? (3)
Put seat upright
Tell them to wiggle their toes
Ensure them that they are doing well
What does a good impression need to have? (4)
Correct extension
Record anatomical landmarks
Rolled borders
Surface details
What are the important muscles in the face? (5)
Masseter
Buccinator
Mentalis
Pterygoid
Mylohyoid
Why is the mylohyoid muscle important for impressions? (1)
Under- or over extended recordings can lead to discomfort, pain, poor retention and stability of the denture
What anatomical features will influence your choice of major connector for lower dentures? (5)
Alveolar ridge (level and extent of resorption, shape (knife redge).
Mental foramen (resorption of alveolar ridge)
Muscle attachments
Frenum (deph of the sulcus)
Mandibular Torus
What problems can the palatal torus cause for upper dentures? (2)
1) Rocking, flexing, pain/discomfort or fracture of major connector
2) This can be overcome by either:
Covering or uncovering torus (horse-shoe shape)
Surgery
