Temporary Materials Flashcards
What are the four types of temporary dental materials and their typical clinical applications?
PMMA (PolyMethylMethAcrylate): Indirect, long-term use for short and long crowns/bridges.
PEMA (PolyEthylMethAcrylate): Direct/chairside, short-term use for single crowns.
Bis-acryl Composite: Direct/chairside, long-term use for short-span bridges.
UDMA (Urethane Dimethacrylate): Direct or indirect, long-term use.
What is free radical addition polymerization in temporary materials?
A process where methacrylate monomers form polymer chains via a reaction initiated by free radicals, leading to material hardening.
List the advantages and disadvantages of PMMA as a temporary material.
Advantages:
Good marginal fit
High transverse strength
Polishable
Disadvantages:
Poor abrasion resistance
High shrinkage
Significant thermal release
Free monomer toxicity
How are temporary materials delivered for clinical use?
PMMA/PEMA: Powder/liquid formulation.
Bis-acryl Composite/UDMA: Two-paste cartridge systems
What are the limitations of product literature in evaluating dental materials?
Often superficial and sales-oriented.
May lack detailed or scientifically validated data.
Why is temperature rise a concern during temporary material fabrication?
Excessive heat generated during polymerization can cause pulpal damage due to:
Protein denaturation.
Irreparable thermal trauma to smaller teeth.
What were Zach and Cohen’s key findings on pulpal damage and temperature rise?
2°C increase: No effect.
5.5°C increase: Temporary tissue changes; recovery in most cases.
11°C increase: Significant necrosis in two-thirds of samples.
How did BALDISSARA’s findings contradict Zach and Cohen’s study?
BALDISSARA found no pulpal damage even with a temperature rise of 14°C held for 170 seconds, suggesting higher tolerance to thermal stimuli than Zach and Cohen reported.
Compare the temperature rises during polymerization for different materials.
TCB DUAL CURE, PROVIPONT, ISOTEMP, INTEGRITY, PROTEMP GARANT
TCB dual cure: 3.5°C
Provipont DC: 4.5°C
Isotemp: 5°C
Integrity: 9°C
Protemp Garant: 10.5°C
How do mean temperature and duration impact material selection?
Materials with lower temperature rise and shorter polymerization times (e.g., TCB dual cure) minimize the risk of pulpal damage.
Why is polymerization shrinkage significant in temporary materials?
Low shrinkage ensures better marginal fit and reduces microleakage, preserving the restoration’s functionality.
Which material demonstrated the best color stability after immersion in coffee?
Protemp 4 showed virtually no colour change after three days of immersion at 36°C.
What factors should be evaluated when selecting temporary materials?
Ease of use.
Working and setting times.
Abrasion resistance.
Colour stability (e.g., resistance to staining in coffee tests).
Which material is generally considered the best for temporary restorations and why?
Bis-acryl composite (e.g., Protemp 4) is often preferred because:
It has low polymerization shrinkage, ensuring excellent marginal fit.
Superior color stability, particularly in aesthetic zones (e.g., minimal staining in coffee tests).
Higher compressive strength compared to PMMA or PEMA.
Suitable for long-term use and short-span bridges when fabricated chairside.
No single material is ideal for all applications
