partial dentures 4 new Flashcards
What are the aims of primary impressions?
🟣 To capture the entire potential denture-bearing area, including:
All standing teeth 🦷
The buccal and lingual sulci
Any area where a denture might contact
🎯 The resulting cast is used to:
🧠 Plan treatment
🧭 Survey for undercuts and path of insertion
🧰 Construct a special tray for secondary impressions
What areas must be recorded in a primary impression for a denture?
✅ All of the following should be captured:
Edentulous ridges
Buccal sulcus
Palate
Hamular notch
Lingual sulcus
Retromolar pad (posterior mandibular area)
What are the differences between elastic and inelastic impression materials?
What are the advantages of alginate?
✨ Cheap and easy
✨ Pleasant taste 🍓
✨ Elastic (captures undercuts)
✨ Good surface detail
✨ Mucostatic (doesn’t distort soft tissue)
What is alginate and how does it work?
🧪 Alginate is an irreversible hydrocolloid. It sets via a chemical reaction:
Sodium alginate + Calcium sulphate + Water → Calcium alginate + Sodium sulphate
💡 Once set, it can’t be reversed or reused.
What are the disadvantages of alginate?
❌ Poor dimensional stability (must be poured within 1 hour) ⏳
❌ Can shrink (syneresis) or swell (imbibition)
❌ Cannot be added to
❌ Low tear resistance
❌ Needs adhesive and tray support (floppy once set!)
What are the steps when taking a primary impression?
1️⃣ Tray selection:
Small/MED/LARGE
Must not touch teeth
Should cover all teeth
Extend 2mm short of sulcus
2️⃣ Tray modification:
Use wax/silicone/impression compound to support alginate
Prevents slumping of material
- extend to full depth of sulcus
3️⃣ Use of green stick if needed for border moulding
4️⃣ Take impression → pour within 1 hour ⏳
When and why would you modify a stock tray?
🛠 Modify when:
Tray doesn’t fully cover sulcus or teeth
Large edentulous spaces = unsupported alginate risk
🧰 Modify using:
Wax (4 layers for labial support)
Silicone putty
Impression compound
👉 To prevent alginate distortion and improve detail!
What is green stick compound and what is it used for?
🟢 Green stick is a thermoplastic, inelastic impression material
Softens with heat 🔥
Used for border moulding trays before taking alginate or silicone impressions
👄 Captures functional sulcus depth during muscle movement!
How do you use green stick compound for border moulding?
🔥 Soften in flame (move in/out to avoid burning)
💦 Dip in warm water (~50°C) before placing in mouth
📏 Mould it along outer tray borders
🗣️ Ask patient to:
Smile 😁
Move lips/cheeks/tongue 👅
Stretch facial muscles
✂️ Trim excess with hot wax knife
🖊️ Draw a line 2mm from sulcus depth to guide lab!
What are secondary impressions and why do we take them?
📌 Purpose:
Capture accurate, functional detail
Record denture-bearing tissues under movement
Ensure proper extension and fit of denture
Record bautemtn teeth and tooth prep in detail for construction of framework
🎯 Needed for:
Final denture design
Accurate framework fabrication (e.g., cobalt chrome RPDs)
What materials are used for secondary impressions?
Medium/light-bodied silicone 🩵
Alginate (occasionally)
Green stick (for border moulding)
What are special trays and how are they designed?
🧰 Made from light-cured acrylic
Made on primary cast
Have 3mm spacing around teeth
Close-fitting over edentulous ridges
Stops to prevent over-seating
Perforated (for alginate) or non-perforated (for silicone)
If needed, drill holes >1mm for retention
Why is border moulding important?
🏃 Captures functional movement of the sulcus
Ensures denture flanges won’t impinge during chewing/talking/smiling
Prevents denture dislodgement
Done with green stick or pink silicone
What do you check during a metal framework try-in?
🦷 On Cast:
All components present
Design matches prescription
Rest seats seated correctly
Adequate relief from gingiva
🦷 In Mouth:
Try each arch separately
Check for:
Rocking
Impingement
Occlusion (with articulating paper/wax)
Patient comfort
What is the purpose of recording the occlusion?
🎯 To provide the technician with:
Correct relationship between upper & lower casts 🧩
Midline and arch shape
Occlusal plane
Tooth shape, size, and shade 🎨
Class of incisor relationship (I, II, III)
Space available for teeth
📦 Case 1: Stable ICP & small gaps
Technician can hand articulate models
Shade only needed
Case 2: Occlusal stops but larger gaps
Use record rim
Record occlusion in ICP
Case 3: No stable occlusion
Use upper & lower wax rims
Record in RCP
Provide all guidance for setting up teeth
What are wax rims and what are they used for?
🕯️ Wax rims help:
Establish occlusal plane
Indicate midline and tooth positions
Set correct incisor display
Determine vertical dimension
Used especially in full dentures or unstable occlusions
What is blue mousse used for?
🧊 Blue mousse is a PVS bite registration material
Used to record opposing occlusion accurately
Ensures casts are mounted correctly in articulator
What info must be included in the lab prescription after recording occlusion?
📬 Must include:
Tooth shade 🎨
Incisor class (I/II/III)
Baseplate material
Occlusal scheme
Articulator type
Tooth mould and setup instructions 🦷
What are primary impressions usually taken with
How do we select tray
what are common problem s selecting a tray
How do we take lower impressions from a patient
How do we take Upper impressions from a patient
How do we take impressions using border moulding?
How do we asses completed impression
What are the stages of a Secondary impression
What is the clinical tecnqie of border moulding
- set up warm water bath 50 degrees
- use greenstick to pink stick
- after heated and placed onto special tray, insert into warm water for couple of seconds before putting it into patients mouth
then removed excess impression compound with to wax knife -leaving depth and buccal surfaces remaining
❗️Why is it important to beware of leaving greenstick compound behind in the sulcus? 🟢
❌ Soft tissue trauma – causes pain, ulcers, or inflammation
😵 Distorted impression – affects fit, seal, and accuracy of denture
⚖️ Unintended pressure – alters sulcus shape, reduces denture stability
✅ What to do:
🔥 Trim excess with hot wax knife
✂️ Ensure greenstick stops 2mm short of sulcus
🤲 Check borders for sharpness or bulk
Motto: “Check it, heat it, trim it, test it.” ✔️
