lecture 20 preventive dental materials (slides)

8/3/2019 Lecture 20 Preventive Dental Materials (Slides)

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Preventive dental

materials

Preventive dentalPreventive dental

materialsmaterials


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Why are they used? To prevent injury or disease.

Three classes of materials areinvolved

Fluoride gels Pit and fissure sealants

Mouth protectors


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Fluoride Gels: acidulated sodium fluoride gels

contain 2% sodium fluoride (or more) +hydrogen fluoride + phosphoric acid.Fluoride ion concentration 1.22-1.32%.Stannous fluoride maybe used too.

Rinses: sodium fluoride or stannousfluoride

Varnishes

* Some products have pH of 6-8 to preventacid etching of restorations


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Rinse

Varnish

Gel


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Properties

Help to reduce smooth surface cries

Effectiveness depends on method ofapplication and frequency andduration.

A gel should be viscous enough forease of handling but fluid enough to

flow all around teeth


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Manipulation

Fluoride gel in trays: teeth clean and dry,patient should bite for 4 minutes and notrinse for 30 minutes


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Pit and fissure sealants To prevent pit and

fissure caries Pits and fissures are

enamel faults,inaccessible tocleaning using toothbrushes

Another method toseal fissures is usingair abrasion thenflowable composite.


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Composition and reaction Similar composition to resin composite but

more fluid. MOSTLY ACTIVATED BY VISIBLE LIGHT 2 component systems are activated by

peroxide initiator and amine activator Components:

Bis-GMA UDMA


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Examples


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Properties Physical and mechanical properties

depend on the product. Bonding is mechanical by acid etching

done to: Clean the surface Improve wettability

Create a rough surface


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Properties Sealant penetration maybe difficult due

to: Air entrapment Food debris accumulation

Penetration of sealant into fissure

depends on: Penetration coefficient of sealant: Surface tension Viscosity of sealant

Contact angle of sealant with enamel

Configuration of fissure (length, diameter)


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For sealants to be effective they

have to be retained. Reviews are important to replace

deficient sealants If caries exists under sealants,

studies showed that the number ofbacteria is low.


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When a sealant is not

used Uncooperative patients

If molars are caries free for a longtime

If there are no pits an d fissures


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Application


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Mouth protectors


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General points Made from polymers

Formed by heat to fit over teeth

Used to protect from injury or asvehicle to apply fluoride or bleachingmaterial


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Types and composition

Stock Mouth formed

Custom made: preferred, due to: Better comfort

Lack of bad odor or taste Minimal impaired speech Durability

But more expensive than other types


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Composition Custom made: in sheets 1.6-3 mm

thick Thermoplastic polymer (poly-vinyl

acetate-polyethylene polymer) or calledethylene vinyl acetate (EVA)

Other products: rubber latex

Polyurethane Vinyl plastisol.


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TypesCustom made

Mouth formed

Stock


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Properties

ADA specifications consider physical,mechanical properties

EVA properties before and afterinsertion into oral cavity are

different. Inside the mouth, theybecome more flexible, better impactstrength, but less tensile strength


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Compared to other

products Polyurethanes: higher strength,

hardness, higher water sorption,need higher processing temperatures

Plastisol and rubber latex haveslightly lower strength and hardness

compared to EVA but are difficult toprocess


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Complaints Gagging

Discomfort

Irritation

Bad taste

* Not common if mouth guard is made

properly.


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Continue,

Thicker mouth guard is stronger butmore uncomfortable

A final thickness of 4 mm isdesirable over incisal edge and cusps.Usually 2 thin sheets are used to

compensate for shrinkage


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Failures

Bite through, chewing through,tearing


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Parafunctional habits affect the

longevity of mouth protectors Deformation may occur due to

improper storage (in heat, tightspace

Should be stored on stone model orin a rigid container


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Fabrication Taking an impression

Pouring a model

Forming the thermoplastic material

on the model (by hand, pressurelamination, vacuum)

Finishing


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How is it made?

Palatal area is

not needed

V d


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Vacuum and pressure

lamination techniques

Both are moreaccurate than by hand


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Technique continue, Model is centered

Sheet is heated Lowered onto the model

Vacuum to fit the sheet on model Cooling

If primary teeth are erupting aspacer is placed


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Continue, Trimming: 3 mm above labial fold, clearance for

frenum Edges should be smooth by flame torching themthen smoothed with fingers

For occlusal adjustment: occlusal surface isheated than placed inside patients mouth inocclusion.

If vertical dimension is to be increased extra

layers of polymer are placed when soft then asecond layer under vacuum.


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Hand forming technique Sheet is softened in boiling water for

20 seconds Adapted by fingers on model and held

by wet towel Trimmed and finished


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Maintaining mouth guard Clean teeth

Clean mouth guard occasionally

Do not use abrasive

Do not use alcohol

Store in container provided


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References Dental materials, properties and

manipulation chapter 3.

lecture 20 preventive dental materials (slides)

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