TOPIC: LABORATORY PROCEDURE, OCCLUSAL RELATIONSHIP AND POSTINSERTION OF REMOVABLE PARTIAL DENTURE
🎯 KEY POINTS:
🔹Aerosol spray is useful in fitting the framework on the master cast.
🔹Functionally generated pathway technique eliminates the need for face bow transfer.
🔹Gypsum-bonded investment is used for casting type IV gold alloys and ticonium.
🔹Boley gauze is used for the accurate transfer of the design to the refractory cast.
📌 STEPS INVOLVED IN THE FABRICATION OF CAST PARTIAL DENTURE
💡The steps involved in the fabrication of cast partial framework are as follows:
🔺Fabrication of the master cast
🔺Surveying of the master cast
🔺Block out and relief of master cast
🔺Master cast duplication
🔺Refractory cast fabrication
🔺Beeswax dip
🔺Waxing of the partial denture framework
🔺Spruing of the waxed framework
🔺Investing of the waxed framework
🔺Burnout
🔺Casting
🔺Finishing and polishing
✳️ BLOCK OUT: Applying wax or another similar temporary substance to undercut portions of a cast to leave only those undercuts essential to the planned construction of the prosthesis.
⭐Types of Block Out
(i) Parallel block out
(ii) Shaped block out
(iii) Arbitrary block out
🔷 RELIEF IN RELATION TO FABRICATION OF CAST PARTIAL FRAMEWORK
💡The common areas that require relief are:
- Below the lingual bar connectors or bar portion of the linguo-plates
- Maxillary or the mandibular tori
- Below the framework, over the edentulous ridge for attachment of the acrylic resin
✳️ REFRACTORY CAST: A cast made of a material that will withstand high temperatures without disintegrating also called investment cast’. (GPT 8th Ed)
💡Low Heat Investment
- Such as the gypsum-bonded investment material
- Used for casting type IV gold alloy and ticonium
- Burnout temperature of this material is 704°C
💡High Heat Investment
- Such as the phosphate-bonded investment material
- Used for casting cobalt–chrome alloy
- Burnout temperature of this material is 1037°C
✳️ SPRUING OF THE FRAMEWORK
Sprue: The channel or hole through which plastic or metal is poured or cast into a gate or reservoir and then into a mold. (GPT 8th Ed)
⭐ Types of Spruing
💠Based On the Number Of Sprues
🔸Single
🔸Multiple
💠Based On The Location Of The Main Sprue
🔸Direct or top spruing
🔸Indirect or bottom spruing
🔸Rear spruing
✳️ PROCEDURE OF BURNOUT CYCLE:
🔸1st hour: Temperature is maintained at 100°C; water is driven out during this phase.
🔸2nd hour: Temperature is increased to 238°C.
🔸3rd hour: Temperature is raised to 675–710°C for 1.5–2 h.
✳️PROCEDURE OF CASTING METHODS:
🔸Gas oxygen blowtorch
🔸Oxyacetylene mixture
🔸 Induction casting
📌 METHODS OF ESTABLISHING OCCLUSAL RELATIONSHIP FOR PARTIAL DENTURE
There are two methods of establishing an occlusal relationship:
(i) Functionally Generated Path Technique
(ii) Articulator Or Static Technique
🔶 FUNCTIONALLY GENERATED PATH TECHNIQUE:
👉 Definition: Registration of the paths of movement of the occlusal surfaces of teeth or occlusion rims of one dental arch in plastic or other media attached to the teeth or occlusal rims of the opposing arch. (GPT 8th Ed)
🔶 ARTICULATOR OR STATIC TECHNIQUE
👉 This technique includes the following:
📍Direct Apposition Of The Casts or Hand Articulation
📍Using Interocclusal Record
📍Jaw Relation Record Entirely Made On Occlusion
📍Occlusal Relation Using Bite Rims On The Denture Bases