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What is the purpose of record bases?
- support wax rims
- make CR record
- make trial denture
What makes record base ideal?
- strength & rigidity
- accuracy-no rocking
- smooth, polished borders (no trauma)
- thickness = finished dentures (no gagging, tongue restriction)
What is palatal thickness of record base?
What defines the thickness and contour of borders?
land of master cast (should not overextend)
What materials are used for record bases?
- Tray resin: brittle but accurate
- Autopolymerizing acrylic resin: strong but less accurate
- Light cure resin: accurate, brittle, expensive
What happens if palate of record base is too thick?
- restrict tongue space/articulation
What shape should lingual mandibular base be?
concave so doesn't limit tongue or interfere w/speech
Which areas should be thinnest for proper tooth positioning?
anteriorly and over 2nd molar region
Which sound is best to determine VDO?
What is positioned used to determine?
Vertical dimension of occlusion (VDO)
What does wax occlusion rims do?
- transfer face bow record
- orient incisors and occlusal plane
- develop lip contour
- develop VDO
- tentative CR recrod
- general aid in selecting teeth
What features contribute to support?
- •Retromolar pad
- •Alveolar ridge contours (the broader the more support)
- •Amount of attached keratinized mucosa
- •Buccal /Palatal(max) shelf area
- (the more access and the greater the surface area the better the support
What features contribute to stability?
- Alveolar ridge height
- flabby, moveable tissue
- Mand: floor of mouth contour, tongue position(anterior v retruded)
- Max: well formed tuberosities
What features contribute to retention?
- Mandible primary: tongue position, floor of mouth posture, neuromuscular control
- Mandible secondary: peripheral seal, adhesion, cohesion
- Maxilla: shape(palatal vault), drape(soft palate), saliva (quant/qual), compressibility, well shaped tuberosities, height of alveolar ridge
What does the height of the alveolar ridge contribute to?
maxillary retention resistance to lateral displacement
What are the final impression objectives?
- 1.Preservation-against alveolar ridge atrophy or resorption, the process can be hastened or retarded by local factors.
- Pressure in the impression technique is reflected as pressure in the denture base and results in soft tissue damage and bone resorption.
- 2.Support-maximum coverage= “snow shoe” effect.
- 3.Stability- close adaptation to the underlying mucosa is most important to reduce the horizontal movement of the denture.
- 4.Retention-atmospheric pressure, adhesion, cohesion (depends on peripheral seal), mechanical locks, and muscle control.
- 5.Esthetics-border thickness should be varied to restore facial contour and proper lip support.
What happens at the 2nd clinical appointment?
- Final impressions after est. health of denture bearing
- Try in custom tray, adjust 2-3mm short vestibule
- Establish 3D contours of denture w/ thermoplastic compunt
- Final impression w/light body for mucostatic final impression
What are the types of impression techniques?
- functional position: dentures unseated when soft tissues that are displaced and
- recorded in this position attempt to return to the undisplaced position
- when the forces are released. Pressure
- limits the normal blood flow-> resorption
- Selective Pressure Technique:
- combination of extension for maximum coverage within tissue tolerance with light pressure or intimate contact with the movable, loosely attached tissues in the vestibules. The impression is refined with minimum pressure utilizing a wash of light body impression material.
What is the selective pressure technique?
- combination of extension for maximum
- coverage within tissue tolerance with light
- pressure or intimate contact with the movable, loosely attached tissues in the vestibules. The impression is refined
- with minimum pressure utilizing a wash of light body impression material.
Where is the only tissue not at rest when making final impression?
Posterior palatal seal area
What are the types of impression compound?
- Type I: impression
- Type II: tray preparation (border molding)
- Composition: filler (50%),resin (40%), wax(7%), stearic acid (3%)
- Characteristics: thermoplastic, low thermal conductivity, stiff/brittle at room temp
- 110 Degrees for ISO compound
What is the sequence of maxillary border molding?
- •Area “A” is molded by instructing the patient to move the mandible laterally and anteriorly, pucker, and smile.
- anterior areas are molded by the following:
- •Massage the upper lip with a lateral motion
- •Instruct the patient to pucker and smile
- •Check the flange thickness for proper lip support
- Area D:
- Place 2-3 mm of compound on top of the tray in a butterfly configuration to
- displace the tissues in the posterior palatal seal area.
- Seat the tray firmly. After the tray has been in position for 10
- seconds ask the patient to swallow.
- Remove the tray and chill.
What structure limits the thickness and length of the denture border in this region?
What is the purpose of vent hole on maxillary tray?
- 1)To permit proper seating of the loaded master impression tray while making the
- final impression.
- 2)To relieve the pressure over the incisive papilla and the rugae.
- 3) To prevent entrapment of air bubbles in the impression
DO AFTER BORDER/PALATAL SEAL MOLDING
What are the desirable characteristics of impression materials?
- •We recommend an elastic, free flowing, light body polysulfide impression material
- for most maxillary impressions.
- •Vinyl Polysiloxane impression materials such as Virtual may also be used. The material should have hydrophilic properties and adequate viscocity to reduce the probability of gagging.
What factors make for a good impression?
- •Smooth well defined peripheries
- •Maximum extension
- •Even pressure distribution (there should be no areas where the underlying tray or
- compound shows through)
- •There should be intimate tissue contact without voids
What is the window tray impression technique?
- used to record highly mobile or hypertrophic tissue with minimum displacement
- tissues are most often seen anteriorly and may be particularly prominent in
- patients with combination syndrome. It
- is inadvisable to remove these mobile tissues because the underlying bony ridge
- is usually knife edged. These tissues
- act as a cushion and rarely impinge upon the interocclusal
What is sequence of mandibular border molding?
- A: buccal flange: pucker smile
- Proper extension into area “D” will create seal for the mandibular denture in selected
- patients with favorable tongue position and floor of mouth posture.
- insert and mold area “E” by instructing the patient to push their tongue
- against your thumb placed in the lower incisor area and to swallow. It may take several applications to properly
- define the length and contour of the denture border in this area.
- Do not let go of the tray.
- Hold the tray in position until the material has polymerized.
What should be considered for patients with unfavorable floor of mouth posture?
Dentures retained with osseointegrated implants
- retention. Note denture snaps onto retention bar.
- •Improved stability (from the implants and the retention bar).
- •Improved support (anteriorly).
- •Improved control of the bolus (tongue no longer must position denture and control bolus simultaneously).
- •Improved mastication efficiency
What are features of tray acrylic?
•Higher % filler material- more accurate, less shrinkage