Interim Restorations Flashcards
Use of Interim Restorations (6)
ØEsthetics
ØFunction
Ø Prevent Sensitivity
Ø Drifting
ØTissue Health
ØDiagnostics
Interim Restorations
•Definition:
• A prosthesis designed to enhance esthetics, stabilization
and/or function for a limited period of time after which it
is to be replaced by a definitive prosthesis.
Interim Restorations
• Used to
• Used to assist in determination of the therapeutic
effectiveness of a specific treatment plan or the form and
function of the planned definitive prosthesis.
Interim Restorations
• Essential to Fixed Prosthodontic treatment since
restorations are fabricated indirectly in the laboratory.
• “Interim” or “provisional restoration”
• NOT “—-”
temporary
Interim Restorations
• Requirements:
(1)
• The same as for definitive
restorations, except for
longevity and sophistication of
color
Biomechanical Requirements:
(7)
• Pulpal protection
• Positional stability
• Occlusal function
• Cleansability
• Marginal integrity
• Strength and retention
• Esthetics / Phonetics
Protect the Prepared Teeth
(5)
• Bacterial plaque and saliva
• Exposure to irritating and painful
stimuli
• Temperature changes; chemicals /
fluids
• Marginal leakage
• Abrasion or breakage of prepared tooth
surfaces
Positional Stability (Intra-arch /
Inter-arch)
(3)
• Proximal contacts
• Occlusal contacts
• Inter-abutment stability (FPD)
Positional Stability – Proximal Contact
• A provisional will prevent
lateral drifting of the prepared and/or adjacent teeth)
Tooth
migration
Inability to
seat final
crown
Excessive
contact
Excessive
adjustment
Open
proximal
contacts
(2)
Impaction of
food and
debris
Periodontal
inflammation/
bone loss
Inadequate
Occlusal contact
(Infra-occlusion)
(2)
Extrusion
Premature
occlusion on
crown
Proper
Occlusion
Mastication
Comfort
Positional
stability
Supraocclusion
(3)
Pain
Dislodgement
of the
provisional
Crack/
Breakage of
the provisional
Restore Masticatory Function and Occlusion (3)
• Centric occlusal contacts (anterior and posterior)
• Lateral and protrusive guidance where appropriate on anterior teeth.
• No contact in lateral and protrusive on posterior teeth.
Maintain Periodontal Health (4)
• Non-impinging margins
• Physiologic contours, emergence profiles, embrasures, and proximal
contact
• Smooth surface texture and finish
• Leads to optimum and predictable tissue health
• Fit:
as close to finish line of tooth as possible
• Contour:
smooth, undetectable with explorer; smooth surface finish
• Sealed to prevent
leakage and resultant pain / caries or dislodgement
Marginal Integrityr: undetectable with explorer
(3)
• Emergence Profile: flat or slightly concave – NOT convex bulge
• Rough, thick margin → plaque accumulation; gingival inflammation
• Hemorrhage complicates impressions, cementation
Strength and Retention
• Adequate thickness for strength
(2)
• Withstand forces without breaking or dislodgement
• Adequate tooth reduction is necessary
Strength and Retention
• Physical properties of dental materials
(2)
• Metal or resin
• PMMA vs Bisacryl Resin
Strength and Retention
• Adequate thickness for strength
(3)
• Withstand forces without breaking or dislodgement
• Adequate tooth reduction is necessary
• Connectors / pontic contours ↑ w/o gingival impingement
Strength and Retention
• Physical properties of dental materials
(2)
• Brittleness (fracture) – especially bis-acryl resins
• ↑ Wear
Esthetics and Phonetics
• Maintain phonetics through:
(5)
• Proper tooth length, position, contours
• Facial (lip) support
• Proper tooth (pontic) form for appearance
• Tooth shade compatible with remaining teeth
• Preview of final restoration for patient acceptance
While in a fluid state, the mixed
resin
fills the cavity formed by a
mold, and then solidifies producing a
rigid restoration.
Custom Interim – Direct Technique
(4)
Molar is prepared for FGC.
Resin injected into mold of unprepared tooth.
Impression with resin re-seated onto
prepared tooth; allowed to set.
When removed, internal surface of provisional
crown is seen
Custom Interim – Direct Technique
ØCustom direct interim crown is removed from the matrix, and then
shaped and polished.
Interim Fabrication
• Two-part mold:
one part forms external contour of crown or FPD;
the other forms the internal or tooth / tissue-contacting surface.
external form (matrix)-
internal form (tooth)-
custom.preformed
direct/indirect technique
External Surface Form
(2)
• Pre-fabricated (preformed) crowns
-Single crowns only
• Custom-fabricated molds
-Single or multiple unit restorations
Technique of fabrication
• “Direct on tooth” versus “Indirect on cast”
Prefabricated crown forms
(5)
• Aluminum or tin-silver
• Nickel-chrome or stainless steel
• Polycarbonate shells
• Cellulose acetate shells
• VLC moldable composite crowns
Custom molded crown or FPD forms:
(3)
• Vacuum-formed matrix
• Silicone putty matrix
• Alginate or VPS impression
ØPre-fabricated Crown Forms
(5)
1) Limited to single units
2) Must be lined with auto polymerizing resin
3) Considerable modification (internal relief, axial recontouring, occlusal
adjustment) may be required
4) Can manipulate resin to prevent “locking in”
5) First-visit emergency when crown is missing
ØCustom molded crown or FPD forms:
(4)
1) Less time consuming
2) Must be used for multiple units (FPD)
3) Improved contours and esthetics
4) Simulates planned restoration (when used in combination with
diagnostic waxing).
ØDirect Technique
• Made
intra-orally directly on patient
ØIndirect Technique
• Made
in laboratory on a cast of the prepared teeth
Direct Technique:
indication (2)
1) Convenience
2) Time required for fabrication – routine restorations
ØIndirect Technique:
indication (4)
1) Patient comfort / allergies
2) Presence of multiple undercuts
3) Long span FPD or multiple units
4) Indirect Provisionals can be fabricated in advance of the tooth
preparation appointment; use of auxiliaries
Direct vs. Indirect Techniques
• Combination Indirect-Direct technique
• Custom interim shell made in laboratory and relined intra-orally
Polymerization and Polishing Acrylic Resin
(2)
• Warm water in pressure pot 20-25 psi (PMMA)
• Increases polymerization; decreases porosity
• PMMA polish:
wet pumice / muslin wheel; dry tin oxide (Acrilustre) on muslin wheel
• Bis-acryl resin polish:
rubber abrasives, polishing paste, or unfilled resin glaze
The finish and polish must contribute to patient comfort
and physiologic tissue health:
(3)
• Tissue stabilization for esthetics
• Final impression
• Cementation of final restoration
Desirable Properties and Characteristics
Polymer Resins for Interim Restorations
(8)
1) Convenient handling
2) Biocompatibility
3) Dimensional stability during polymerization
4) Ease of contouring and polishing
5) Flexural strength and abrasion resistance
6) Appearance (translucence; color; color stability)
7) Patient acceptance
8) Chemical compatibility with luting agents
Currently Available Materials
ØAcrylic Resins:
(3)
1) Poly(methyl methacrylate) (PMMA)
2) Poly(R’ methacrylates) (R’ = ethyl, vinyl, isobutyl)
3) Powder / Liquid (chemically activated; “cold cure”)
Currently Available Materials
ØBis-Acryl Composite Resins:
(4)
1) Multifunctional dimethacrylate composite resins
i. Bis-GMA / Bis-EMA / Urethane dimethacrylate
2) Chemically-Activated
3) Dual-Activated (chemical / VL)
4) Visible Light-Activated
Free Radical Polymerization
ØThe chemical conversion of monomer to a biologically inert polymer
by chain reaction.
ØUnreacted free monomer is
toxic (esp. MMA)
ØInadequate polymerization results in poor — properties.
mechanical
Polymerization reaction is —, and there is — upon
polymerization and cooling.
exothermic
shrinkage
ØInitiation
(2)
• Activation:
• Free radical combines with monomer
• Activation: (3)
formation of a free radical by decomposition of an
initiator (due to “activator”)
• Benzoyl peroxide + 3o amine / heat (MMA)
• Camphoroquinone + blue light-490nm (VLC composite)
Propagation (growth)
• Process of adding molecules in growing chain
Termination
(2)
• Growing chains randomly combine; stop growing
• Polymerization is completed
ØPropagation: process of adding
molecules in the growing chain
• Physical properties of (2) develop
rigidity and
strength
• Setting material — density and
exothermia, causing
↑
polymerization
contraction.
↑ Temperature during propagation
promotes:
(2)
• greater polymerization and
• removal of unconverted monomer
Composites: additional (2)
VLC ↑
polymerization, strength
Termination
• Growing chains randomly combine
• Material becomes rigid – able to finish / polish
(≈— minutes)
5
Desirable to convert all free monomer to
polymer before termination
(2)
• (Does not COMPLETELY happen)
• Composites: additional VLC ↑
polymerization, strength
• Inhibition: (3)
Reaction with eugenol, oxygen,
hydroquinone will cause termination.
• Where would contact with eugenol occur?
• “Oxygen inhibited layer”?
Properties associated with MONOMER:
(2)
• Chemical / allergic irritation
• Physical properties of set material
Properties associated with MONOMER:
• Chemical / allergic irritation
• Physical properties of set material
(4)
• Exothermic heat of reaction & volumetric shrinkage
• Strength of mass
- As MW (size) of monomer ↑ (ethyl, isobutyl, etc.), exothermia, shrinkage, and strength ↓
• Composites: UDMA can affect resilience, toughness to counteract brittleness
ØProperties associated with POLYMER (Powder):
(3)
• Increase in filler content →
• Too much filler →
• Composites: size / shape of particles affects density, strength, surface finish
• Increase in filler content →
(2)
- Greater strength
- Less exothermia and less shrinkage
• Too much filler →
poor handling
Poly(methyl methacrylate) – PMMA
ØADVANTAGES
(4)
• Good marginal fit
• Good transverse strength
• Polishes well
• Durability / color stability
Poly(methyl methacrylate) – PMMA
Ø DISADVANTAGES
(4)
• Toxic monomer
• High exothermia
• High volumetric shrinkage (8%)
• Low abrasion resistance
Problems with PMMA
(6)
• PMMA can generate temperatures
of 70oC or higher in the pulp
chamber as material goes through
polymerization.
• Free monomer contact with tissues
→ chemical burns, allergic
reactions.
• Monomer vapor is harmful.
• A volumetric shrinkage of ~8% occurs
on polymerization.
• A 2% reduction in crown diameter
results in a high marginal
discrepancy.
• Results when polymerization occurs
off the tooth.
Poly(R’ methacrylate) – not used at UMKC
(R’=ethyl, vinylethyl, isobutyl, etc. – Trim, Snap)
ØADVANTAGES
(2)
• Less exothermia
• Less shrinkage
Poly(R’ methacrylate) – not used at UMKC
(R’=ethyl, vinylethyl, isobutyl, etc. – Trim, Snap)
Ø DISADVANTAGES
(6)
• Toxic monomer
• Poor:
• Surface hardness
• Transverse strength
• Durability
• Fracture toughness
• Color stability
Bis-Acryl Resins (Composite)
ØADVANTAGES
(5)
• Good marginal fit
• Low exothermia
• Low shrinkage
• Good surface hardness and
abrasion resistance
• Good biocompatibility, color
stability, and patient acceptance
Bis-Acryl Resins (Composite)
Ø DISADVANTAGES
(4)
• Limited polishability
- Improved surface finish w/ resin glaze
• No doughy/rubbery stage
• ↑ Cost
• Brittleness
Problems associated with Interim
Restorations
(3)
• Time required for fabrication
• Time the interim is required to function in the
mouth
• Materials available for fabrication
Problems associated with Interim
Restorations
• Management of deficiencies
(2)
• Reline / modification / repair
• Treatment of the fractured or defective surfaces
• Treatment of the fractured or defective surfaces (3)
• Grinding to expose fresh surfaces; removing enough to
provide adequate thickness and ability to complete reseating of restoration
• Roughening / sandblasting / bonding agent
• Composite – flowable composite resin
cements:
• Zinc Oxide – Eugenol cements (Temp Bond)
(3)
• Low strength
• Sedative (obtundant) and bactericidal
• Inhibition of resin polymerization
• Non-eugenol cements: (3)
• Polycarboxylate cement w/ plasticizers
(Ultratemp)
• Glass ionomer-based cement – modified
(Smart Temp)
• Resin Cement (modified low strength) (Telio
CS Link)
Polycarboxylate cement w/ plasticizers
(Ultratemp)
• Low strength final cement
Glass ionomer-based cement – modified
(Smart Temp)
• Longer-term use
Resin Cement (modified low strength) (Telio
CS Link)
(2)
• Especially helpful for planned bonded-ceramic
restorations
• Translucent
Provisional Cementation
(2)
• Equal amounts of base and catalyst are mixed together on a mixing pad.
• The material is mixed with a small spatula until homogenous.
• Mixing Syringe is also available
