Irreversible Irreversible Hydrocolloid Hydrocolloid Irreversible Irreversible Hydrocolloid Hydrocolloid

IrreversibleIrreversible HydrocolloidHydrocolloid IrreversibleIrreversible HydrocolloidHydrocolloid

Student ____________________

Preliminary Alginate Impressions

Date / / Initials_______ Instructor #_____

Unacceptable Correctable Acceptable Student

Unacceptable Correctable Acceptable Instructor __________

Accurate recording of all critical anatomy

Material properly mixed as indicated by impressions

Minimum of voids

Trays properly selected and centered over the ridges

Minimal areas where trays have contacted tissues

Diagnostic Cast Evaluation




No significant bubbles or flaws in stone

Base approximately parallel to ridge and approximately l/2 inches thick (minimum)

Evidence of a dense stone surface

Clean and well trimmed

Includes all anatomical surfaces

Student ____________________

Preliminary Alginate Impressions




Accurate recording of all critical anatomy

Material properly mixed as indicated by impressions

Minimum of voids

Trays properly selected and centered over the ridges

Minimal areas where trays have contacted tissues

Diagnostic Cast Evaluation




No significant bubbles or flaws in stone

Base approximately parallel to ridge and approximately l/2 inches thick (minimum)

Evidence of a dense stone surface

Clean and well trimmed

Includes all anatomical surfaces

Preliminary ImpressionsPreliminary ImpressionsPreliminary ImpressionsPreliminary Impressions

Selection of a Stock TraySelection of a Stock TraySelection of a Stock TraySelection of a Stock Tray• 5 -7 mm between tray & tissues – Bulk for strength & accuracy of material– Just short of vestibule – Slightly beyond vibrating line

• 5 -7 mm between tray & tissues – Bulk for strength & accuracy of material– Just short of vestibule – Slightly beyond vibrating line

Stock Tray Selection Stock Tray Selection Stock Tray Selection Stock Tray Selection • Compound on peripheries if needed • Extension only to provide coverage of critical

anatomy • Not for displacing vestibular tissues

• Compound on peripheries if needed • Extension only to provide coverage of critical

anatomy • Not for displacing vestibular tissues

Pre-Measure MaterialPre-Measure Material Pre-Measure MaterialPre-Measure Material

• Infection control – Do not take

containers to your operatory

– Do not handle containers with contaminated gloves/hands

• Infection control – Do not take

containers to your operatory

– Do not handle containers with contaminated gloves/hands

Handling the MaterialHandling the MaterialHandling the MaterialHandling the Material

• Do not leave containers open in a humid environment –Humidity & high temperatures cause

deterioration

• Do not leave containers open in a humid environment –Humidity & high temperatures cause

deterioration

Use Separate BowlsUse Separate BowlsUse Separate BowlsUse Separate Bowls

• Gypsum can cause acceleration of setting of alginate

• Alginate contamination can decrease strength of casts

• Gypsum can cause acceleration of setting of alginate

• Alginate contamination can decrease strength of casts

AlginateAlginate

StoneStone

Measuring AlginateMeasuring AlginateMeasuring AlginateMeasuring Alginate

• Fluff the powder before measuring

• Ensure no large voids

• Fluff the powder before measuring

• Ensure no large voids

Measuring AlginateMeasuring AlginateMeasuring AlginateMeasuring Alginate

• Do not tap the scoop more than once or twice–Compacts the powder

– Thicker mix

• Do not tap the scoop more than once or twice–Compacts the powder

– Thicker mix

PreparationsPreparationsPreparationsPreparations

• Measuring by weight is more accurate than by volume

• Ratio of 1 scoop powder : 1 measure water

• 3 scoops of powder is sufficient for most arches

• Measuring by weight is more accurate than by volume

• Ratio of 1 scoop powder : 1 measure water

• 3 scoops of powder is sufficient for most arches

Regulating Set TimeRegulating Set TimeRegulating Set TimeRegulating Set Time

• Regulate with water temperature

• Water/powder ratio can affect tear strength & viscosity

• Regulate with water temperature

• Water/powder ratio can affect tear strength & viscosity

Mixing AlginateMixing AlginateMixing AlginateMixing Alginate

• Mix for up to 45 seconds

• Smooth creamy consistency

• No lumps or powder should remain

• Mix for up to 45 seconds

• Smooth creamy consistency

• No lumps or powder should remain

MixingMixingMixingMixing

Fill TrayFill TrayFill TrayFill Tray

Making the ImpressionMaking the ImpressionMaking the ImpressionMaking the Impression

• Wipe alginate onto the occlusal surfaces of any teeth

• Wipe alginate onto the occlusal surfaces of any teeth

Making the ImpressionMaking the ImpressionMaking the ImpressionMaking the Impression

• Don't bottom out on the teeth or the residual ridge–Distort the tissue or move teeth

– Stone leaks between alginate & tray & produces distorted cusp

• Don't bottom out on the teeth or the residual ridge–Distort the tissue or move teeth

– Stone leaks between alginate & tray & produces distorted cusp

Making the impressionMaking the impressionMaking the impressionMaking the impression

• Wait to remove impression until the material is firm

• Approximately one minute after initial set

• Wait to remove impression until the material is firm

• Approximately one minute after initial set

RemovalRemovalRemovalRemoval

• Lift lip up to break the seal against tissues

• Several drops of water

• Remove rapidly, to prevent significant permanent deformation

• Lift lip up to break the seal against tissues

• Several drops of water

• Remove rapidly, to prevent significant permanent deformation

Impression StorageImpression StorageImpression StorageImpression Storage

• Wrap in a damp towel –Wring to eliminate excess water

• Pour within 12 minutes – Minimizes distortion

• Support impression by handle or tray until cast poured

• Wrap in a damp towel –Wring to eliminate excess water

• Pour within 12 minutes – Minimizes distortion

• Support impression by handle or tray until cast poured

Evaluating Irreversible Evaluating Irreversible Hydrocolloid ImpressionsHydrocolloid Impressions


• Properly mixed

• Smooth surface

• Properly mixed

• Smooth surface



• Tray centered over ridge• Tray centered over ridge



• No significant tissue/tooth contact• No significant tissue/tooth contact



• No-large voids in the impression• No-large voids in the impression



• All critical anatomy recorded –Hamular notches–Retromolar pads–Vestibules, etc.

• All critical anatomy recorded –Hamular notches–Retromolar pads–Vestibules, etc.

DisinfectionDisinfectionDisinfectionDisinfection

• Rinse the impression• Place in zip lock bag, pour in

disinfectant to cover all surfaces• Seal for 10 minutes• Remove and rinse prior to

pouring stone

• Rinse the impression• Place in zip lock bag, pour in

disinfectant to cover all surfaces• Seal for 10 minutes• Remove and rinse prior to

pouring stone

Mixing StoneMixing StoneMixing StoneMixing Stone

• Weigh powder

• Measure water

• Vacuum mix– Less time to complete than

hand mixing – Stronger cast

• Weigh powder

• Measure water

• Vacuum mix– Less time to complete than

hand mixing – Stronger cast

Two pour techniqueTwo pour techniqueTwo pour techniqueTwo pour technique

• Pour stone into impression

• Wait for stone to set (~ 30 minutes)

• Invert impression with set first pour onto base stone

• Superior surface strength

• Pour stone into impression

• Wait for stone to set (~ 30 minutes)

• Invert impression with set first pour onto base stone

• Superior surface strength

Two Pour TechniqueTwo Pour TechniqueTwo Pour TechniqueTwo Pour Technique

• Use vibrator & flow the stone into the impression slowly

• Modulate speed of pouring by tilting the tray back and forth

• Use vibrator & flow the stone into the impression slowly

• Modulate speed of pouring by tilting the tray back and forth


• If impression fills too quickly-voids

• To delay filling:– Tilt impression in opposite direction of

the flow of the stone– Reduce speed of vibrator

– Press impression less firmly against

vibrator

• If impression fills too quickly-voids

• To delay filling:– Tilt impression in opposite direction of

the flow of the stone– Reduce speed of vibrator

– Press impression less firmly against

vibrator


• Leave rough areas on the exposed surface of the stone–Helps attach base

• Leave rough areas on the exposed surface of the stone–Helps attach base


• Make a patty of stone

• Invert impression with the first pour onto the base

• Adapt new stone to the existing stone

• Make a patty of stone

• Invert impression with the first pour onto the base

• Adapt new stone to the existing stone


• Trim excess stone from the base with the spatula while the stone is still soft

• Trim excess stone from the base with the spatula while the stone is still soft


• Separate impression from cast after 30 minutes

• Separate impression from cast after 30 minutes

Trimming CastsTrimming CastsTrimming CastsTrimming Casts

• Model moist for trimming–Debris from trimmer will not

attach

• Model moist for trimming–Debris from trimmer will not

attach

Trimming CastsTrimming Casts Trimming CastsTrimming Casts

• Soak the model by immersing– in slurry water

– just base of cast contacting tap water

• Soak the model by immersing– in slurry water

– just base of cast contacting tap water

Trimming CastsTrimming CastsTrimming CastsTrimming Casts

• Prolonged immersion in tap water can lead to erosion of the cast

• Prolonged immersion in tap water can lead to erosion of the cast

Trimming Trimming DiagnosticDiagnostic Casts CastsTrimming Trimming DiagnosticDiagnostic Casts Casts

• Cast should be minimum of 10-12mm (.5 inch) in thinnest part

• Trim the base on the model trimmer parallel to ridges

• Leave the mucous membrane reflection intact for making a custom tray

• Cast should be minimum of 10-12mm (.5 inch) in thinnest part

• Trim the base on the model trimmer parallel to ridges

• Leave the mucous membrane reflection intact for making a custom tray

a

10-12mm

a

10-12mm

Trimming Trimming MasterMaster Casts CastsTrimming Trimming MasterMaster Casts Casts

a

3mm

3mm

LandArea

10-12mm

a

3mm

3mm

LandArea

10-12mm

• Boxed and trimmed with a 3mm wide by 3mm deep land area

• Aids in processing of acrylic

• Diagnostic casts (no land area) – Used for making custom trays

– Land area omitted so material is easier to trim & remove from the

cast

• Boxed and trimmed with a 3mm wide by 3mm deep land area

• Aids in processing of acrylic

• Diagnostic casts (no land area) – Used for making custom trays

– Land area omitted so material is easier to trim & remove from the

cast

Outline of Bases for Trimmed Outline of Bases for Trimmed CastsCasts

Outline of Bases for Trimmed Outline of Bases for Trimmed CastsCasts

• Follow the contour of the ridges, with rounded angles

• Follow the contour of the ridges, with rounded angles

a

Mandibular Maxillary

a

Mandibular Maxillary

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