Preventative and Intermediary Materials Flashcards
What do sealants do?
Fill in irregularites in teeth, particularly in posteriors, to create a smooth surface that is easier to clean and less likely to retain food and harbor bacteria.
What are the most common sealants?
Bis-GMA - light cured
What are the characteristics of sealants?
Reasonably low viscosity
Flowable
Filler particles of silica or inorganic glasses for stiffness
What are the benefits of light cured sealants?
Working time is completely controlled by operator
What is air inhibition?
The surface layer of a sealant is prevented from polymerization. This needs to be removed after curing and is removed with an abrasive slurry of pumice.
What is filler used for in sealants?
Improve mechanical properties of sealant, especially elastic modulus. Prevents deflection under occlusal stress.
When does optimal adhesion of sealant to enamel occur?
When sealant has high surface tension, good wetting, low viscosity.
Do sealants release fluoride?
Fluoridated sealants release fluoride for the first 24 hours after placement, but then release decreases to ineffective levels
What colors of sealants are availavble
Tooth colored or clear
Color-reversible resins change color under dental curing lights to visualize coverage
How effective are sealants?
Almost all studies show a direct correlation between sealant retention and caries protection.
What must sealants accomplish?
Retention of enamel, resistance to occlusal wear, easy application, low surface contamination
How must enamel be prepared?
Wettability improved by etching
Pretreatment with silicanes in solution may help.
Saliva must be prevented from contaminating etched surface
How are sealants applied?
Thin brush, ball applicator or syringe
Excess build up should be avoided
Sealant should not be overworked to avoid air voids
Air-inhibited surface layer should be wiped away immediately.
What are pros and cons of glass ionomer sealants?
+They release fluoride
- Are generally viscous which makes filling difficult
- Brittle and less resistant to wear
- Low retention rates
What are pros and cons of composite sealants?
\+Low viscosity, "flowable" \+packaged in syringes or compules \+Filler provides better wear resistance -Long-term clinical efficacy not established -Air bubbles must be carefully avoided
What are significant properties of glass ionomers?
- Elastic modulus similar to dentin
- Bond strength to dentin 2-3 MPa (lower than resin, but retention better)
- Expansion coefficient comparable to tooth structure
- Low solubility
- Fairly high opacity
- Fluoride releases slowly
- Mild pulp reactivity
- Working time is short
When are resin-modified/hybrid ionomers used?
Low stress-bearing areas
What are properties of hybrid ionomers?
Double flexural strength of glass ionomers
Fluoride release rechargable
Packaged as powder-liquids
Optimum powder/liquid ratio is critical
Light cured
Color and texture improved by finishing in wet environement
Can be used to line dentin walls in deep cavities.
Lines deep cavities, then resin composite fills
What are calcium hydroxide cements used for?
Lining deep cavities
Pulp-capping
What are properties of calcium hydroxide cements?
Set to hard mass
Can be light cured
Create secondary dentin bridges when applied to direct pulp exposures
Low tensile strength, compressive strenght, elastic modulus
Somewhat soluble
Calcium Fluoride
Deposited on tooth surface
Converted to fluorapatite through remineralization reaction
Advantages of fluoride varnish
Extended time of exposure for active fluoride ingredient on tooth surface.
Good preventative action against caries
Pathological factors of caries
- Acid-producing bacteria
- Frequent consumption of fermentable carbohydrates
- Below normal salivary flow and function
Protective factors against caries
- Normal salivary flow and components - Ca and P
- Fluoride
- Antibacterials
