Crown & Bridge Cement

8/2/2019 Crown & Bridge Cement

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CROWN AND

BRIDGE CEMENT

BY:-SURBHI BHARDWAJBDS II


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Alternate name Zinc Phosphate cement

Zinc Oxyphosphate Cement

Zinc Cement


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HISTORYThe earliest formulation as reported byRollins(1879),Gaylord(1889),Ames(1893 &Fleck(1902) were variously based on syrup oforthophosphoric acid or unstable mix of

metaphosphoric acid & sodiummetaphospate in solution.

Later cements with 50% sol. of o-phosphoric

acid was used but problem revolved aroundthe control of setting reaction but by the timeFlecks (1902) paper these problems hadbeen solved.


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The importance of densifying &deactivating the ZnO powder to moderatethe reaction was recognized & it was also

found that satisfactory cements could beproduced only if aluminum wasincorporated into the o-phosphoric acid

solutionThe basic science underlying this empiricalfinding was elucidated only in 1970


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Definition According to Boucher zinc phosphate

cement is defined as material used forcementation of inlays, crowns, bridges, and

orthodontic appliances and occasionally asa temporary restoration. It is prepared bymixing zinc oxide and magnesium oxidepowders with a liquid consisting principally

of phosphoric acid, water, and buffers.


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TYPES Type I(fine grain) - Used for the

permanent cementation of castrestorations such as crowns, inlays,

onlays, and bridges. This materialcreates the very thin film layer that isnecessary for accurate seating ofcastings.

Type II(medium grain) -Recommendedfor use as an insulating base for deepcavity preparations


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dispensing

As powderliquid system

As singlecomponent

NOTE-A capsulated system which is mechanically mixedhas been marketed


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Composition of powderZINC OXIDE-

90.2%(Reactiveingredient)

MgO-8.2%(To reduce temp.

of calcination)

SILICA-1.4%(inactive filler)

BITHMUS OXIDE-.1%

(imparts strength tofreshly mixedcement)

BaO/CaO- .1%(modifiers)

Colour pigmentsin trace amount


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Composition of liquid 38.2%

Reactive ingredientPhosphoric

acid

16.2% buffer

Aluminumphosphate &zinc phos.

Zinc 7.1%

Moderator

Water


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manipulation


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cement formingreaction

ZnO Alumino-phosphoric

acid complex

Zinc aluminophosphate ge

Heat


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properties


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1.BIOLOGICAL PROPERTY It is recognized as pulpal irritant

Probable cause is free phosphoric acidpresent at the time of placement ofcement

Pulp should be covered with pulpcapping agents


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RHEOLOGICAL

PROPERTIES


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1.WORKING AND SETTING TIME

MATERIAL ADA no. 96 Commercial product

TYPE I 2.5-8 mins 5.5 mins

TYPE II --- 3-4mins

FACTORS AFFECTING

# Powder liquid ratio

# Rate of powder incorporation# Temperature of mixing slab# Spatulation time# Water content


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2.CONSISTENCY

luting

standard

base


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3.RETENTION Non-adhesive to tooth structure or

surface of casting

MECHANICAL adhesion (factors

affecting)

#Rough surface on tooth & restoration

#Film thicknes & consistency of material

#Strength of luting cement


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3.SOULBILITY &DISINTEGRATION Measured by wt. loss when a disc of

cement is suspended in distilled waterfor 24hr.

ADA req. for type I is max. 0.2%

FACTORS AFFECTING

#P/L ratio

#Initial wetting of cement mix

#Solvent & its pH


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Mechanical propertiesPROPERTIES TYPE I TYPE II

Compressive strength 80-100 MPa(ADA>75MPa)

100-170MPa(ADA>103.5)

Tensile strength 5.5MPa 5-14MPa(brittle)

MOE 14,000MPa 22,000MPaFilm thickness 25-30 mc mt. 30-35 mc mt.

STRENGTH OF CEMENT IS INFLUENCED BY

#Initial powder & liquid composition

#P/L ratio#Time#Handeling of the cement during placement


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Thermal property Have adequate thermal insulating

property.

Used as base under metallic restoration

Optical propertySet cement is opaque

Hence,cant be used for ant. restoration


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uses Primarily used as permanent

cementation material to fix performedrestorations

To fix orthodontic bands Thermal insulating base

Temporary or intermediate restorative

material


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Advantages disadvantages Good compressive

strength

Easy manipulation

process Sets sharply to

relative hard mass

Low cost production

Long history ofclinical success

Pulpal irritation

Lack ofanticariogenic & anti

bacterial action Lack of chemical

adhesion to toothstructure

Soluble in oral fluids Non-aesthetic


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modifications


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HYDROPHOSPHATE CEMENT The phosphoric acid is freeze dried &

converted to solid form, these solid acidphosphates are blended with phosphate ofZn,Ca & other metals as well as the oxides ofthese metals with water

Liquid used id distilled water Acidity is same as of conventional Zn-P

cement Other properties inferior then that of

conventional one Used as luting cement & thermal insulating

bases


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FLUORIDE CEMENYS Some zinc phosphate cement contain 1-

3% of stannous fluorides & they areparticularly used for orthodontic

cementation Have low strength & high solubility

because of dissolution of fluoridecontaining material

But ant cariogenic property is not sogood as leaching of fluoride ionsdecrease in 1-2days


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Copper cement/Silvercement/germicidal cement Ag salts or Cu oxides are sometimes added to powder of

zinc phosphate cement to impart antibacterial /antisepticproperty

Silver cement generally contain few % of salt such as silverphosphate. Silver salts darkens on exposure in the mouth

Cement is black when cupric oxide is added,red if cuprousoxide is added white if cuprous iodide is added & green ifcupric silicate is added

Cement is used in rare cases such as rampant caries ofdeciduous teeth

They are seldom used currently because there clinicalbehavior doesnt seem superior to any other temporary

restorative material & their toxic reaction to the pulp isgenerally recognized


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CONCLUSION

Zinc phosphate is oldest and mostwidely used dental material and isconsidered as gold standard cement

because of its long clinical success.


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Crown & Bridge Cement