Comparison of Indirect Restorative Dental Materials-Dental Materials Lecture note


Indirect restorations are generally done in two or more dental visits.  The first visit involves cutting the tooth down to a size and shape in which it will be able to support and retain a custom manufactured restoration.  An impression, which records the shape of the preparation, down to the most minute detail is taken and sent to the laboratory where the restoration is fabricated.  The patient leaves the office with a temporary restoration generally made of plastic and is given an appointment for an insert date several weeks later after the lab has finished making the restoration.  The final restoration is inserted using a cement to adhere it to the tooth preparation on the second visit.  (Note: In some practices, these restorations are fabricated in-office using a computer assisted design technique, in which case the patient may receive the finished restoration at the same visit.)

Comparison of Indirect Restorative Dental Materials
Factors
All-Porcelain (ceramic)
Porcelain Fused To Metal
Gold Alloys (high nobel)
Base Metal Alloys (non-nobel)
General Description
Porcelain, ceramic or glasslike fillings and crowns
Porcelain is fused to an underlying metal structure to provide strength to a filling, crown or bridge.
Alloy of gold, copper and other metals resulting in a strong, effective filling, crown or bridge.
Alloys of non-noble metals with silver appearance resulting in high strength crowns and bridges.
Principal Uses
Inlays, onlays, crowns and aesthetic veneers
Crowns and fixed bridges.
Inlays, onlays, crowns and fixed bridges
Crowns, fixed bridges and partial dentures.
Leakage and Recurrent Decay
Sealing ability depends on materials, underlying tooth structure and procedure used for placement.
The commonly used methods used for placement provide a good seal against leakage.  The incidence of recurrent decayy is similar to other restorative procedures.
Durability
Brittle material, may fracture under heavy biting loads. Strength depends greatly on quality of bond to underlying tooth structure.
Very strong and durable.
High corrosion resistance prevents tarnishing; high strength and toughness resist fracture and wear.
Cavity Preparation Considerations

Because strength depends on adequate porcelain thickness, it requires more aggressive tooth reduction during preparation.
Including both porcelain and metal creates a stronger restoration than porcelain alone; moderately aggressive tooth reduction is required.
The relative high strength of metals in thin sections requires the least amount of healthy tooth structure removal.
Clinical Considerations

These are multiple step procedures requiring highly accurate clinical and laboratory processing. Most restorations require multiple appointments and laboratory fabrication.
Resistance to Wear
Highly resistant to wear, but porcelain can rapidly wear opposing teeth if its surface becomes rough.
Highly resistant to wear, but porcelain can rapidly wear opposing teeth if its surface becomes rough.
Resistant to wear and gentle to opposing teeth.
Resistance to Fracture
Prone to fracture when placed under tension or on impact.
Porcelain is prone to impact Highly resistant to fracture. fracture; the metal has high strength.
Highly resistant to fracture.
Biocompatibility
Well tolerated.
Well tolerated, but some patients may show allergenic sensitivity to base metals.
Well tolerated.
Well tolerated, but some patients may show allergenic sensitivity to base metals.
Post-Placement Sensitivity
Sensitivity, if present, is usually not material specific.
Low thermal conductivity reduces the likelihood of discomfort from hot and cold.
High thermal conductivity may result in early post-placement discomfort from hot and cold.
Esthetics
Color and translucency mimic natural tooth appearance.
Porcelain can mimic natural tooth appearance, but metal limits translucency.
Metal colors do not mimic natural teeth.
Relative Cost to patient
Higher; requires at least two Patient office visits and laboratory services. 
Average Number of Visits to Complete
Minimum of two; matching esthetics of teeth may require more visits.
Minimum of two; matching esthetics of teeth may require more visits.
Minimum of two.

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