mouth prepartion and master cast Flashcards
phase 1 pt tx
relief of?
collection of?
what is cast is made? used for?
develop what plan?
what to do with pt?
occlusion?
– Relief of pain & infection= priority
– Collection of diagnostic data= Diagnostic cast, Diagnostic mounting
– Develop treatment plan= Design RPD
– Patient education & motivation
– Occlusal equilibration
phase 2 pt tx
removal of?
extraction of?
surgery?
perio? plaque?
interim prothesis? why?
occlusion?
– Removal of deep caries, temporary restorations
– Extraction of non-retainable teeth
– Preprosthetic surgery: tuberosity reduction, etc.
– Periodontal treatment, Plaque control
– Interim prosthesis: function, esthetics
– Occlusal equilibration, may need changes after extractions
phase 3 pt care
endo?
restorative?
occlusion?
– Definitive endodontic treatment
– Definitive restorative treatment: Surveyed crowns, if needed and Fixed partial dentures, if appropriate
– Occlusal plane correction
phase 4 of pt tx
– Construction RPD
phase 5 tx
– Post-insertion care
– Periodic recall
– Continued plaque control
goals of mouth preparation
pain/infection?
caries?
extractions? surgery?
perio/plaque?
occlusion?
endo?
definitive restorations?
enameloplasty?
• Relief of pain & infection
• Caries removal
• Extractions, Preposthetic surgery
• Periodontal treatment, plaque control
• Occlusal equilibration
• Endodontics
• Definitive Restorative Treatment:– Amalgams, composites– FPDs, crowns, surveyed crowns
• Occlusal plane correction
• Enameloplasty for RPD GP
Diagnostic Casts roles
• Preliminary design of RPD
• Identify tooth modification areas
performing tooth mods?
– according to RPD diagnostic cast design
– QA Worksheet
possible enameloplasty in order
- develop guide planes
- enlarge embrasure for minor connectors
- lower HOC
- create undercuts if needed
- rest seats
developing guide planes
proximal
ML
L
– Proximal: adjacent to edentulous areas
– ML: stress-release clasps ML minor connector
– Lingual: reciprocal clasp
considerations of lowering the HOC
– Proximal 2/3 Circumferential retentive clasp
– Reciprocal clasp
– Lingual Guide Plate
confirming mouth preparations
• Alginate Impression(s)/Snapstone Cast(s)
• Survey interim casts
• Confirm that preparations are parallel to path of insertion in the following sequence:
1. Prepare guiding planes
2. Enlarge embrasures for minor connectors
3. Reposition the survey line to reduce interferences to framework placement and enable most ideal clasp placement
• Confirm that survey line lowered enough
Undercut Preparation
• Used when slightly insufficient retentive undercut
• Sloped buccal &/or lingual surface, procedure contraindicated: reconsider other areas for undercut or surveyed crown
when is placing an undercut prep indicated
slightly insufficient retentive undercut with vertical buccal & lingual surfaces
how is the retentive undercut prepped
Preparation with round-ended tapered diamond
when are rest seats made
After adequate preparation for GP, Survey line alterations
Checking the adequacy of occlusal/embrasure rest seats:
– Patient close into beading wax
– Measure thickness of wax (Caliper)
• At least 1mm
what if yu cannot obtains adequate depth in enamel of the tooth for the rest seat
• Remove small amount of opposing tooth structure
– Be sure to remake impression of opposing arch
Master Cast: Class III RPD impression techniques
does the ridge provide support in these cases?
• Residual ridge not provide RPD support
• Alginate/stock tray
• Alginate/custom tray
• Custom tray/elastomeric material
– Preferred technique UMKC
– Not border molded
– Medium-bodied PVS
Master Cast: Distal Extension RPD Impression
ridge support?
captures? why?
how should force be distributed?
allows increased?
less frequent?
• Residual ridge important source of RPD support
• Important to accurately record maximum tissue support area– Broad-stress distribution concept
• Distribute occlusal forces over as many teeth & as much soft tissue as possible
• Not overload teeth or tissue
• Increased stability & retention
• Less frequent reline
The Problem with Tooth-Tissue Supported RPDs:
•The periodontal membrane allows for 0.25 +/- 0.1 mm and the muco-periosteum allows for 2.0 + mm movement
•Due to the lever effect of the distal extension base, occlusal pressure is concentrated on the distal end of the base
The Solution for Tooth/Tissue Supported RPDs
equalize support from?
distributing load?
base movement?
• Equalize support derived from tissue and teeth
• To distribute load to both the natural and artificial dentition & minimize base movement
Master Cast: Extension RPD Impression techniques
• Custom tray/elastomeric material
• Corrected (Altered) Cast technique
Custom tray/elastomeric material technique for master casts
border molded tray, one step
• Corrected (Altered) Cast technique for distal extended cases basic steps
– Two-step (Dual) impression
• Step one: Impression of teeth & residual ridge
• Step two: Impression of residual ridge areas using framework
Master Cast: Altered Cast Impression step 1
• Step one: Impression of teeth & residual ridge
– Alginate/stock tray or Alginate/custom tray
– Framework fabricated on 1st cast
• Framework less precise than with elastomeric impression
Master Cast: Altered Cast Impression step 2
• Step two: Impression of residual ridge areas only
– Sectional trays added to framework
– Border-molded
– Elastomeric material
creation of the altered cast
errors of the altered cast approach
•Lift of distal framework during residual ridge impression
•Framework on final cast not oriented the same as in the mouth
one step and two step cast techniques compared
• Leupold, Flinton, & Pfeifer, JPD, 1992
–Compared one-step border-molded custom tray/elastomer impression & altered cast impression technique
– Concluded clinically insignificant difference in the vertical displacement of final RPD between the 2 techniques
– One-step technique less prone to operator error than altered cast procedure
one step custom tray impression, making the tray
which cast is used?
method?
• Fabricate tray on working / diagnostic cast
• Apply separating medium to cast– Liquid foil (not vaseline)
• Tray extensions:– 2-3 mm coronal to vestibule depth in both dentate &
edentulous areas
• Wax spacer placed over tray outline
– ~3 mm over teeth (red rope wax)
– ~1.5 mm over residual ridge (baseplate wax
tray stops in custom tray making (one-step technique)
– 3 widely spaced openings in wax spacer
• 3 mm openings
– Tripod support for tray
– Use teeth NOT contacted with rests
– Residual ridge stops similar to complete denture tray
custom trays and aluminum foil
Aluminum foil over wax spacer (not vaseline)
• Triad tray material adapted over foil/spacer
• Polymerize
finger rests of the custom tray, why?
Add finger rests to tray surface over edentulous areas
– Stability during impression
– Strengthen tray
• Distal tray areas prone to fracture
• Narrow, flat residual ridges
• Add handle
when to determine final tray extension, how is this done?
• Determine final tray extension at impression appointment
– PIP tray flanges: extension & outer surface
– Do border molding movements
– Areas where PIP removed, shorten or thin tray
border molding the custom tray
where?
materials?
• Border mold distal extension residual ridge areas
• Elastomeric impression material
– Polysulfide: High tear strength, pour within 1 hour
– PVS: Hydrophobic, adequate tissue detail
making the master cast with second impressions
• Box impression
• Pour with improved dental stone
surveying the master cast
determining Poi?
marking Hoc?
marking the undercut?
what to do once all this is done?
– Determine path of insertion
• Guide planes parallel, Equalize undercut
– Mark abutment height of contour
• Facial & Lingual
– Measure & mark retentive undercut
• RED line
• NOT red DOT
• Approximate inferior edge of clasp
• Tripod lateral sides of cast
Lab Prescription
requires?
• Surveyed cast
• Work authorization– Lab RX
• Send to QA for approval
• Send to Lab
• Framework fabricated
