Temporary Crown

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Lect. 4 Crown and Bridge Dr. Ameer Hamdi ALAmeedee
Temporary Crown:
A fixed prosthesis, designed to protect, enhance esthetics, stabilization and function for a limited period of time, after which it is to be replaced by a definitive crown
HISTORY
1937 ---- Heat cured acrylic resin.
1947 ---- Auto polymerizing acrylic resin.
1952 ---- Brotman introduced prefabricated aluminum or celluloid crown form.
1959 ---- Amsterdam et al suggested use of copper band splint or thin flexible metal wire for internal reinforcement.
1960s ---- Vinyl poly-ethyl methacrylate (Snap and Trim).
1969 ---- Ethyl imine derivatives.
1972 ---- Gerald J. described a technique for a modified “shell” type temporary acrylic resin fixed partial denture.
1973 ---- Charles et al described the use of polycarbonate resin.
1980 ---- Composite.
1983 ---- Weiner described technique that use silicone putty impression material in provisional restoration fabrication.
1984 ---- Morton et al ---- visible light-cured microfilled composite resin.
1986 ---- Kinsel described use of an acrylic resin denture tooth for construction of interim restoration.
1987 onwards ---- Concept of provisionalization applied and implemented in implant dentistry.
CLASSIFICATION:
1-DEPENDING ON THE METHOD OF FABRICATION:
a- Custom made provisional restoration.
b- Prefabricated provisional restoration.
2- DEPENDING ON THE MATERIALS:
a- Polycarbonate.
b- Cellulose acetate.
c- Aluminium and tin-silver.
d- Nickel-chromium.
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3- DEPENDING ON THE TIME USED:
a- SHORT TERM ---- for few days (upto 2 weeks) ( e.g. ---- Polycarbonate or aluminum crowns ).
b- MEDIUM TERM ---- for few weeks ( > 2 weeks) ( e.g. ---- resin based provisionals).
c- LONG TERM ---- for months ( e.g. ---- mostly cast metal crowns).
TYPES:
1. Pre-formed crowns (made of plastic or metal):
a. Self cured resins.
b. Light cured resins.
c. Composites resins.
d. Heat cured acrylic resin.
e. Cast metal.
f. Fiber reinforced composite resins.
2. Pre-formed crowns proprietary shells:
a. Come in a series of sizes.
b. Usually need considerable adjustment marginally proximally and occlusally.
c. Plastic shells as polycarbonate or acrylic.
d. Metal shell as aluminium, stainless steel or nickel chromium.
3. Polycarbonate resin crowns:
a. Polymethyl methacrylate materials.
b. Crowns combine micro glass fibers with a polycarbonate plastic material.
c. High impact strength.
d. High abrasion resistance.
e. High hardness.
f. A good bond with methyl- methacrylate resin.
4. Preformed metal crowns Aluminum shells:
a- Provide quick tooth adaptation due to the softness and ductility.
b- Rapid wear that results in perforation in function and/or extrusion of teeth.
c- An unpleasant taste Iso-Form Crowns (3M Dental Products).
d- Manufactured with high-purity tin-silver and tin-bismuth alloys.
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e- Suitable ductility and can be contoured quickly.
f- Occlusal table is reinforced so they are more resistant to wear related failure.
REQUIREMENTS:
1-Biological requirement:
a. Pulpal protection.
b. Periodontal health.
c. Occlusal compatibility and tooth position.
d. Prevention of enamel
2-Mechanical requirement:
a. Resist functional loads.
b. Resist removal forces.
c. Maintain interabutment alignment Restore.
3-Esthetic requirement:
a. Tooth contour.
b. Color.
c. translucency.
d. Texture.
FUNCTIONS:
1. Comfort/Tooth vitality: Essential to cover freshly cut dentine and prevent sensitivity, plaque buildup, and subsequent caries and pulp pathology. It also sedate prepared abutments.
2. Occlusion and Positional Stability: To prevent unwanted tooth movement.
3. Function.
4. Gingival Health and Contour: To facilitate oral hygiene and prevent gingival overgrowth.
5. Aesthetics.
To assess the effect of aesthetic and occlusal changes:
1) Calipers may be used to test the thickness of a provisional restoration to ensure sufficient tooth preparation to accommodate the proposed restorative material.
2) A provisional restoration may be used to provide a coronal build up for isolation purposes during endodontic treatment.
3) Long-term provisional restoration may also be advisable to assess teeth of dubious prognosis.
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4) A provisional restoration may find a use as a matrix for core build ups in grossly broken down teeth, by removing the coronal surface to allow placement of restorative material.
5) Proposed changes to the shape of anterior teeth are best tried out with provisional restorations to ensure patient acceptance, and, approval from friends and family.
6) A patient’s tolerance to changes in anterior guidance or increased occlusal vertical dimension is best tried out with provisional restorations.
7) Long-term wear of properly fitting and contoured provisional restorations allows the health of the gingival margin to improve and its position to stabilize before impressions are recorded for definitive restorations.
8) Altered function can be assessed (fine mouth movements and lip/tooth contact required for speech production or sound generation in the case of a musical instrument).
IMPRESSION:
History:
? Philip P. 1756, First described taking impression with softened wax.
? Christopher F. 1820, Introduced the metal impression tray.
? Chapin H. 1853, First used Plaster of Paris for making impressions.
? Charles S. 1857, Introduced the first impression compound.
? Sears A. 1937, First used agar hydrocolloids for recording crown impressions.
? United States-1945, Introduced alginate during World War II.
? Pearson S. 1955, Developed synthetic rubber base impression materials Polysulfide.
? Late 1950’S, First developed as an industrial sealant.
? Condensation Silicone- Early 1960’s.
? Addition Silicone-1970’s.
? Polyether- Late 1970’s.
? Polyether Urethane Dimethacrylate – Late1980 s.
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TERMINOLOGIES:
IMPRESSION: A negative likeliness or copy in reverse of the surface of an object; an imprint of the teeth and adjacent structures for use in dentistry
IMPRESSION TRAY : A receptacle into which suitable impression material is placed to make a negative likeliness (or) a device that is used to carry, confine, and control impression material while making impression.
IMPRESSION MATERIAL: Any substance or combination of substances used for making an impression or negative reproduction.
IMPRESSION TECHNIQUE: A method and manner used in making a negative likeness.
Properties of an ideal impression:
1) Complete plasticity before cure.
2) Sufficient fluidity to record fine detail.
3) The ability to wet the oral tissues.
4) Dimensional accuracy.
5) Dimensional stability.
6) Complete elasticity after cure.
7) Optimal stiffness.
8) Nontoxic.
Impression materials used in Fixed partial denture:
1)-Hydrocolloid impression material:
a) Reversible hydrocolloid.
b) Irreversible hydrocolloid.
2)-Elastomeric impression materials:
a) Polysulfide.
b) Addition silicone.
c) Condensation silicone.
d) Polyether Dimethacrylate.
Impression Techniques:
1. Stock tray technique:
a - Double mix.
b - Single mix.
2. Custom tray technique:
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a - Single mix.
3. Closed bite double arch technique.
4. Copper band technique.
5. Reversible hydrocolloid technique:
a - Laminate Technique.
b - Wet Field Technique.
6. The matrix system.
Impression step techniques:
1. One step technique:
Impression material with one type of viscosity (mostly: medium viscosity material) e.g. polyether.
2. Two steps technique:
Impression material with two viscosities (light and heavy consistency) we mix separately the two types at the same time. The light body type is loaded in the impression syringe; on the other hand the heavy body is loaded to the special tray.
3. Putty wash technique:
Impression material with two viscosities (light and heavy consistency) we mix the heavy body type, we remove the impression after it set inside the patient s mouth after completion of the preparation we start to mix the light body.
EVALUATING FINAL IMPRESSION:
1-Elastomeric material should be present 0.5 mm beyond visible finish line.
2-Note presence of bur marks, the junction of smooth root surface, and continuous finish line.
3-There should be no shiny smooth areas; if present, they suggest moisture contamination.
4-There should be no tray shows though in any areas of the impression except at tissue stops.
5-There must be no voids or no air bobbles present, they suggest mixing problems or contamination.
6-There should be no thin areas leaving the finish line unsupported. These areas distort under the weight of the stone.