Non-elastic impression Non-elastic impression

materialmaterial

Delivered by:Delivered by:

DR. KANWAL GULZARDR. KANWAL GULZAR

IMPRESSION PLASTERIMPRESSION PLASTER

Impression plaster is similar in composition to Impression plaster is similar in composition to dental plaster used to construct models and dental plaster used to construct models and

dies.dies.

COMPOSITIONCOMPOSITION It consists of calcined, beta calcium sullphate hemihydrate It consists of calcined, beta calcium sullphate hemihydrate

which when mixed with water to produce calcium sulphate which when mixed with water to produce calcium sulphate dihydrate.dihydrate.

The material is used at higher water/ powder ratio as The material is used at higher water/ powder ratio as compared to modelling plaster.compared to modelling plaster.

Antiexpansion agents are added to reduce setting Antiexpansion agents are added to reduce setting expansion.expansion.

Potassium sulphate is most commonly used antiexpansion Potassium sulphate is most commonly used antiexpansion agent but it also accelerates setting reaction.agent but it also accelerates setting reaction.

Retarder such as Borax is added to control setting Retarder such as Borax is added to control setting characterstics.characterstics.

A pigment such as alazarin red is added in order to make A pigment such as alazarin red is added in order to make clear distinction between the impression and model after clear distinction between the impression and model after casting of thecasting of the model.model.

IMPRSSION TRAYS USED FOR IMPRSSION TRAYS USED FOR IMPRSSION PLASTERIMPRSSION PLASTER

Impression plaster is too fluid to be used in stock Impression plaster is too fluid to be used in stock tray.tray.

Special trays are normally constructed using 1-Special trays are normally constructed using 1-1.5mm spacer.1.5mm spacer.

Before casting modelling plaster in the plaster Before casting modelling plaster in the plaster impression, the impression must be coated with impression, the impression must be coated with separating agent, otherwise separation is separating agent, otherwise separation is impossible.impossible.

IMPRESSION TECHNIQUEIMPRESSION TECHNIQUE

The technique for insertion of impression into the mouth The technique for insertion of impression into the mouth involves “puddling” the impression into place involves “puddling” the impression into place

The tray containing impression plaster is seated in The tray containing impression plaster is seated in patient’s mouth and then gently move from side to side patient’s mouth and then gently move from side to side and antero-posteriorly, this allow the material to flow in and antero-posteriorly, this allow the material to flow in every area of the mouth every area of the mouth

PROPERTIES OF IMPRESSION PROPERTIES OF IMPRESSION PLASTERPLASTER

Regarding properties the difference between impression Regarding properties the difference between impression

plaster and model plaster is:plaster and model plaster is:

1.1. Impression plaster have more rapid setting in order to Impression plaster have more rapid setting in order to avoid inconvenience to both the patient and the dentist.avoid inconvenience to both the patient and the dentist.

2.2. Have smaller setting expansion for greater accuracy.Have smaller setting expansion for greater accuracy.

3.3. Much lower strength so that fracture can occur easily if the Much lower strength so that fracture can occur easily if the material engages an undercut.material engages an undercut.

USESUSES

Impression plaster remains a useful material particularly Impression plaster remains a useful material particularly when recording impression of patient with excessively when recording impression of patient with excessively mobile soft tissues overlying the residual alveolar bone.mobile soft tissues overlying the residual alveolar bone.

IMPRESSION COMPOUNDIMPRESSION COMPOUND

Impression compound is a thermoplastic material Impression compound is a thermoplastic material having the properties similar to dental waxes.having the properties similar to dental waxes.

TYPES OF IMPRESSION TYPES OF IMPRESSION COMPOUNDCOMPOUND

TYPE I (LOWER FUSING):TYPE I (LOWER FUSING): Used for taking Used for taking impression.impression.

TYPE II: TYPE II: Used for construction of impression trays.Used for construction of impression trays.

MODES OF DISPENSIONMODES OF DISPENSION Type I materials are supplied either in sheet or stick Type I materials are supplied either in sheet or stick

form.form.

Sheet form is used for recording impression of Sheet form is used for recording impression of edentulous ridges.edentulous ridges.

Stick form is used for border extension on impression Stick form is used for border extension on impression tray or for recording impression of single crown using tray or for recording impression of single crown using copper ring technique.copper ring technique.

COMPOSITIONCOMPOSITIONCOMPONENTCOMPONENT EXAMPLEEXAMPLE FUNCTIONFUNCTION

THERMOPLASTIC THERMOPLASTIC MATERIALMATERIAL

Natural or synthetic Natural or synthetic resin and waxesresin and waxes

Characterizes the Characterizes the softening temperaturesoftening temperature

FILTERFILTER Talc Talc Gives “body” by Gives “body” by increasing viscosity of increasing viscosity of the softened material; the softened material; reduces thermal reduces thermal contractioncontraction

LUBRICANTLUBRICANT Stearic acidStearic acid Improves flow Improves flow propertyproperty

MANIPULATIONMANIPULATION

The sheet material is normally softened using a water The sheet material is normally softened using a water bath.bath.

Both the temperature and time of conditioning in water Both the temperature and time of conditioning in water bath effects the material.bath effects the material.

If the conditioning temperature is too low the material does If the conditioning temperature is too low the material does not soften properly and if too high, it becomes sticking and not soften properly and if too high, it becomes sticking and manageable.manageable.

Softening temperature range 55-60C is found to be Softening temperature range 55-60C is found to be normal.normal.

The conditioning time must also be carefully monitored.The conditioning time must also be carefully monitored. It should not be so long that important constituent such as It should not be so long that important constituent such as

stearic acid leached out and it should not be too short that stearic acid leached out and it should not be too short that the material is not thoroughly softened.the material is not thoroughly softened.

The stick material is generally softened using a flame.The stick material is generally softened using a flame. The material is then tempered in water bath before The material is then tempered in water bath before

placing in patient’s mouth.placing in patient’s mouth.

PROPERTIESPROPERTIES

Impression compound is fairly rigid after setting and is Impression compound is fairly rigid after setting and is non-elastic in nature that’s why undergoes distortion on non-elastic in nature that’s why undergoes distortion on removal from undercuts.removal from undercuts.

Because of its high viscocity it is unable to record fine Because of its high viscocity it is unable to record fine details.details.

It is a mucocompressive impression materialIt is a mucocompressive impression material Have poor thermal conductivity that is why require Have poor thermal conductivity that is why require

several minutes for the centre of material to be softened.several minutes for the centre of material to be softened. The material have large values of coefficient of thermal The material have large values of coefficient of thermal

expansion and undergo considerable shrinkage on expansion and undergo considerable shrinkage on removal from the mouth.removal from the mouth.

USESUSES

Impression compound is used to take preliminary Impression compound is used to take preliminary impression of edentulous arches. This gives a model on impression of edentulous arches. This gives a model on which a special tray can be constructed and then which a special tray can be constructed and then secondary impression can be taken.secondary impression can be taken.

Impression waxesImpression waxes Impression waxes are rarely used to record complete Impression waxes are rarely used to record complete

impression.impression. They are normally used to correct small imperfection in They are normally used to correct small imperfection in

other impressions particularly those of the zinc oxide other impressions particularly those of the zinc oxide Eugenol type.Eugenol type.

They are thermoplastic material which flows readily at They are thermoplastic material which flows readily at mouth temperature and relatively soft even at room mouth temperature and relatively soft even at room temperature.temperature.

They are applied with a brush in small quantities to fill in They are applied with a brush in small quantities to fill in areas of impression in which sufficient material has been areas of impression in which sufficient material has been used or in which an air blow or crease has caused a defect.used or in which an air blow or crease has caused a defect.

Zinc oxide /eugenol impression Zinc oxide /eugenol impression pastespastes

Zinc oxide Eugenol is a non-elastic impression material.Zinc oxide Eugenol is a non-elastic impression material.

CHEMICAL COMPOSITIONCHEMICAL COMPOSITION Material is normally supplied as two paste which are mixed Material is normally supplied as two paste which are mixed

together on a paper pad or glass.together on a paper pad or glass.

COMPONENTCOMPONENT FUNCTIONFUNCTIONZinc oxideZinc oxide Reactive ingredient which Reactive ingredient which

take part in setting reactiontake part in setting reaction

PASTE IPASTE I Olive oil, linseed oil or equivalentOlive oil, linseed oil or equivalent Inert component used to form Inert component used to form paste with zinc oxidepaste with zinc oxide

Zinc acetate or equivalentZinc acetate or equivalent To accelerate settingTo accelerate setting

Water (trace) in some products Water (trace) in some products To accelerate settingTo accelerate setting

PASTE PASTE IIII

Eugenol (oil of cloves)Eugenol (oil of cloves) Reactive ingredient take part Reactive ingredient take part in setting reactionin setting reaction

Xaolin, talc or equivalentXaolin, talc or equivalent Inert filler used to form a paste Inert filler used to form a paste with eugenolwith eugenol

SETTING REACTIONSETTING REACTION

On mixing two pastes, a reaction between zinc oxide and On mixing two pastes, a reaction between zinc oxide and eugenol begins which cause the formation of chelate eugenol begins which cause the formation of chelate compound.compound.

The setting reaction is ionic in nature and requires an ionic The setting reaction is ionic in nature and requires an ionic medium to proceed.medium to proceed.

The ionic nature is increased by the presence of water and The ionic nature is increased by the presence of water and certain ionizable salts which act as accelerators.certain ionizable salts which act as accelerators.

Some manufacturers do not incorporate water into the Some manufacturers do not incorporate water into the pastes and for these material setting is retarded until mixed pastes and for these material setting is retarded until mixed paste contacts moisture in the patients mouth.paste contacts moisture in the patients mouth.

Some manufacturers incorporates water as the component Some manufacturers incorporates water as the component of at least one of the paste.of at least one of the paste.

MODE OF DISPENSIONMODE OF DISPENSION The pastes are normally dispensed from tooth paste like The pastes are normally dispensed from tooth paste like

tubes and mixed in equal volume.tubes and mixed in equal volume.

The proportioning is achieved simply by expression of The proportioning is achieved simply by expression of equal length of each paste onto the mixing pad or slab.equal length of each paste onto the mixing pad or slab.

One tube is labeled as catalyst and one is labeled as One tube is labeled as catalyst and one is labeled as base paste.base paste.

There is a good colour contrast between the pastes There is a good colour contrast between the pastes which aid in homogenous, streak free mixing.which aid in homogenous, streak free mixing.

PROPERTIESPROPERTIES Zinc oxide eugenol is low viscosity, non-elastic Zinc oxide eugenol is low viscosity, non-elastic

impression material.impression material.

Because of the lack of elasticity the set material may Because of the lack of elasticity the set material may fracture when removed over undercut.fracture when removed over undercut.

Some patients are allergic to eugenol so in that case Some patients are allergic to eugenol so in that case eugenol free pastes are available. The eugenolis eugenol free pastes are available. The eugenolis replaced by alternative organic acid.replaced by alternative organic acid.

The material can be added to the impression once the The material can be added to the impression once the material is set so that any correction in impression can material is set so that any correction in impression can be made with this material.be made with this material.

USESUSES

The material is normally used to record the major The material is normally used to record the major impression of edentulous arches. The impression is impression of edentulous arches. The impression is normally recorded in close fitting special tray constructed normally recorded in close fitting special tray constructed on model obtained from primary impression.on model obtained from primary impression.

THE ENDTHE END