1. Objectives
   1. Retention
      1. ability of denture to withstand displacement against its path of insertion (POI)
      2. Factors :
         1. Anatomical
            1. ▪︎Size of denture bearing area Maxilla - 25cm² Mandible - 14cm²
            2. ▪︎Tissue displaceability
         2. Physiological
            1. ▪︎Amount & consistency of saliva ▪︎Thin & watery saliva - best retention ▪︎Excess thick ropy saliva - loss of retention
         3. Physical
            1. ▪︎Adhesion ▪︎Cohesion ▪︎Interfacial surface tension (STEPHAN'S FORMULA)- F = 4.7 X kr⁴ ___________________ X V h³ F - surface tension, k is viscosity of liquid, r is radius of contacting surfaces, V is viscosity, h is space between surfaces ▪︎Capillarity ▪︎Atmospheric pressure ▪︎Gravity
         4. Mechanical
            1. ▪︎Undercuts - moderate undercuts enhance retention severe undercuts compromise retention ▪︎Denture adhesives - enhance retention ▪︎Suction chambers or disc - create a negative pressure in palate hence enhancing retention
         5. Muscular
         6. Atmospheric pressure- Emergency retentive force/ temporary restraining force 14.7lb/inch2
            1. Only effective when peripheral seal is present
            2. Maxillary CD obtain it from : base of tongue
   2. Stability
      1. ability of denture to withstand horizontal or lateral forces
      2. Factors :
         1. Vertical height of the ridge
         2. Quality of soft tissue covering the ridge
         3. Quality of impression
         4. Occlusal rims
         5. Teeth arrangement
         6. Contour of polished surfaces
   3. Support
      1. resistance to vertical forces of mastication, occlusal forces & other forces applied in a direction towards basal seat tissues.
      2. For adequate support : cover maximum denture bearing area "SNOWSHOE EFFECT"
   4. Preservation of residual structures
      1. preservation of remaining oral structures is imp. for long term success of denture
   5. Aesthetics
      1. starts with impression making
2. Classification of Impression techniques
   1. Acc.to pressure used
      1. Pressure technique
      2. Minimal pressure technique
      3. Selective pressure technique
   2. Position of mouth while making impression
      1. Open mouth
      2. Close mouth
   3. Method of manipulation for border moulding
      1. Hand manipulation
      2. Functional movements
   4. Types of tray
      1. Stock tray
      2. Custom tray
3. Types
   1. PRIMARY IMPRESSION
      1. First step in fabrication of a CD
      2. Made with a stock tray. There should be atleast 5mm clearance btw stock tray & ridge
      3. Materials - impression compound, alginate or impression plaster
   2. SECONDARY/WASH IMPRESSION
      1. For preparing a master cast
      2. Borders of special tray prepared from primary cast should end 2mm short of peripheral structures
      3. Peripheral structures are recorded by Border Moulding/ Peripheral tracing
      4. Materials - ZOE paste & medium body elastomers
      5. Wax spacer is used in special tray
         1. Thickness should be 1mm
         2. Purpose - 1) Allow space in the tray for final Impression material 2) Allow the tray to be properly positioned in the mouth during border moulding
4. Theories of impression making
   1. Mucostatic/ passive impression/ pressure-less
      1. Given by : Richardson & Henry Page
      2. Material used - Impression plaster
      3. Indications : Fibrous flabby tissues/ hyperplastic tissues/ Knife-edge ridge/sharp bony spicules
      4. Final denture is closely adapted to mucosa but has poor seal
   2. Mucocompressive/ Functional technique
      1. Given by : Carol Jones
      2. Materials used : Impression compound, waxes, soft liners
      3. Indications : Healthy & uniformly firm ridge
   3. Selective pressure technique
      1. Given by : Boucher
      2. Indications : Firm healthy mucosa attached over ridge
5. Border Moulding
   1. Techniques
      1. Incremental/sectional
         1. Material of choice - Green stick compound
            1. PROCEDURE
            2. 1. Greenstick compound is softened over the flame. ▪︎At first flange of custom tray should be reduced until its 2mm short of reflection
            3. 2. Add softened material along the portion of tray when border is intended to be refined
            4. 3. The material should be tempered with warm water before placing intraorally
            5. 4. Labial vestibule is refined first followed by buccal vestibule & PPS & functional movement carried out in this area
            6. 5. After border moulding the moulded section is immersed in cold water. Evaluate retention & stability of border moulded tray
            7. Functional Movements MAXILLA
            8. A. Labial flange ▪︎Extend cheeks outward, downward, & inward ▪︎Patient asked to do puckers, open wide, grimaces, smile
            9. B. Buccal flange ▪︎Extend cheek outward, downward, & inward ▪︎Open wide & move side to side ▪︎Pucker & smile
            10. C. Buccal frenum ▪︎Elevate cheek & pull outward, downward, & inward ▪︎Move backward & forward ▪︎Pucker & smile
            11. D. Posterior lateral Hamular notch ▪︎Move mandible right & left & opening the mouth wide & closes against chin
            12. E. Posterior vibrating line ▪︎Observe line when patient saying "ah" & record this line or area & we can see a butterfly shaped junction of hard & soft palate
            13. Functional Movements MANDIBLE
            14. A. Labial flange ▪︎Extend cheeks outward, upward, & inward ▪︎Patient asked to do puckers, open wide, sneers, grimaces, smile
            15. B. Buccal flange Buccal frenum :- ▪︎Extend cheek outward, upward, & inward move back & forward ▪︎Pucker & smile Distobuccal area :- ▪︎Cheek is pulled buccally & moved upward & inwards
            16. C. Massetric notch ▪︎Patient closes against hand on chin
            17. D. Retromolar pad ▪︎Patient is asked to open mouth wide & closes against hand on chin
            18. E. Anterior lingual flange ▪︎Protrude tongue ▪︎Push tongue against front part of palate ▪︎Push tongue against thumb in lower incisor area
            19. F. Molar lingual flange ▪︎Protrude tongue or make "K" sound ▪︎Push tongue against thumb in lower incisor area ▪︎Swallow
      2. Single-step
         1. Material of choice - Putty/heavy body elastomers eg. :- polyether
6. POSTERIOR PALATAL SEAL (PPS) or POST DAM
   1. 2 regions
      1. Pterygomaxillary seal
      2. Post palatal seal
   2. 2 Vibrating lines
      1. Anterior
         1. Located on soft palate
      2. Posterior
         1. At the junction of soft palate that shows limited movt. & the soft palate that shows marked movt.
   3. Functions
      1. Slightly displaces the soft tissues to ensure complete seal
      2. Prevents ingress of food & saliva beneath denture base
      3. Prevents excess impression material from running down patient's throat
   4. Distal end of denture must cover tuberosities & extend into hamular notches. It should end 1-2mm posterior to vibrating line.
   5. Placing PPS too deeply results in displacement of denture anteriorly
   6. PPS is recorded when head is positioned such that Frankfort's horizontal (FH) plane is 30°below the horizontal plane
      1. Done to activate muscle of soft palate only
   7. Methods to record PPS
      1. 1. Scraping of cast
         1. ▪︎Functional
            1. Patient sit in upright position
            2. Wipe PPS area. Locate hamular notch with T burnished & mark with indelible pencil
            3. Posterior vibrating line established is marked. Trial denture is inserted in mouth & marked line is transferred
            4. Trial base is trimmed till posterior border marking & seated on master cast to transfer the marking
            5. Anterior vibrating line is marked in patient by "Valsalva Maneuvere"
            6. Transferred to the cast
            7. Scraping of cast ▪︎Deepest area - either side of midline 1/3rd distance anterior to posterior vibrating line ▪︎Scraping - 1-1.5mm ▪︎Mid-palatine raphe - 0.5-1mm
            8. Scraped area of cast filled by readapting shellac base/by adding autopolymerizing acrylic
            9. Modified record base is checked in patient's mouth if there is any space
         2. ▪︎Arbitrary
      2. 2. Impression techniques
         1. ▪︎Using fluid wax
         2. ▪︎Using low fusing compound
   8. Errors in PPS
      1. ▪︎Overextention
         1. Can lead to ulceration & painful deglutition
         2. Covering the hamular process can also lead to sharp pain in the region. These areas should be identified, trimmed & polished
      2. ▪︎Under postdamming
         1. Occurs if patient's mouth is wide open while making impressions. Seal area becomes taut in this position & a space is created in other position
      3. ▪︎Over postdamming
         1. Occurs due to excessive scraping of master cast, especially in hamular notch region