ALGINATE

Irreversible Hydrocolloid

Alginate is what type of HYROCOLLOID?

once the paste sets to a gel, the process cannot be reversed.

The term irreversible indicates that ?

1. Ease in manipulation

2. Minimum equipment necessary

3. Flexibility of the set impression

4. Accuracy if properly handled

5. Low cost

Give the reasons for the Wide Use of Alginates

Potassium alginate/sodium alginate (15-20%)

Composition:

To dissolve in water

Calcium Sulfate dihydrate (16%)

Composition:

> React with dissolved alginate to form insoluble calcium alginate

> Reactor

Sodium phosphate/Trisodium phosphate (1- 2%)

Composition:

> React with calcium sulfate (ions) to slow working time

> Provide proper gelation time

Diatomaceous earth/ Silicate powder (50-60%)

Composition:

> Control consistency of the mix and flexibility of the impression > Filler

> Controls strength, stiffness and texture

> Gives mixed material its body

Potassium titanium fluoride/Potassium sulfate/ Potassium zinc fluoride (3%)

Composition:

> Accelerator – for the setting of the gypsum product

Zinc Oxide (7%)

Composition:

> Filler

1. Potassium alginate/sodium alginate (15-20%)

2. Calcium Sulfate dihydrate (16%)

3. Sodium phosphate/Trisodium phosphate (1- 2%)

4. Diatomaceous earth/ Silicate powder (50-60%)

5. Potassium titanium fluoride/Potassium sulfate/ Potassium zinc fluoride (3%)

6. Zinc Oxide (7%)

7. Colorant

8. Flavoring

Give all the composition of alginate

Type I/ Fast Setting

Types of Alginates:

Sets at 60 sec to 120 sec

Type II/Normal Setting/Regular Setting

Types of Alginates:

Sets at 2 min to 4.5 min

Sets at 2 min to 4.5 min

Types of Alginates:

Type II/Normal Setting/Regular Setting - sets ?

Sets at 60 sec to 120 sec

Types of Alginates:

Type I/ Fast Setting - sets at ?

1. Reprogel

2. Identic

3. Replica

Examples of a Regular Setting Alginate Material

2NaPO4 + 3CaSo4 → Ca2(PO4)2 + 3Na2SO4

Gelation Process:

paste to gel

Gelation Process:

potassium alginate → calcium alginate

Permanent Deformation

Properties:

- The amount of deformation during removal is increased

- Time that it is held under compression is increased

- Thinner mixes are used

Flexibility

Properties:

- Relative amount of water and powder used influence the ? of set alginate.

- decreased W/P = decreased flexibility

- increased W/P = increased flexibility

Strength

Properties:

-? is increased if thick rather than thin mixes

- Tear and compressive ? at the time of removal of the impression increases if the time of removal is delayed.

F - increase

Properties: T/F

Decrease in amount of water will weaken the material

T

Properties: T/F

Insufficient spatulation will result to insufficient mixing of material components

Dimensional Change

Properties:

- Loss of accuracy with increase in time of storage.

Syneresis

Properties:

evaporation of water if impression is stored exposed to air

Imbibition

Properties:

absorbs water and expands

F -one hour only

Properties: T/F

Impression can be stored in 100% relative humidity for more than one hour

Normal-set alginate

Manipulation - terminologies:

- Working time of 2 minutes and a setting time of up to 4½ minutes after mixing

Fast-set alginate

Manipulation - terminologies:

- Working time of 1¼ minutes and a setting time of 1 to 2 minutes

Working time

Manipulation - terminologies:

- The time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient's mouth

Setting time

Manipulation - terminologies:

- The time required for the chemical action to be completed.

• Must feel comfortable to the patient

• Should extend slightly beyond the facial surfaces of the teeth

• Should extend approximately 2 to 3 mm beyond the third molar, retromolar, or tuberosity area of the arch

• Depth to allow 2 to 3 mm of material between the tray and incisal or occlusal edges of the teeth

Give two Tray-Selection Criteria

• mandibular

• maxillary

Manipulation:

> Adult ? impression

- Two scoops of powder and two measures of water

> Adult ? impression

- Three scoops of powder and three measures of water

Alginator

Manipulation:

? – mechanical mixer for alginate

1. Iodophor 2. Sodium Hypochlorite 3. Glutaraldehyde

Give the disinfectants

• Tearing

• Distortion

• Rough stone model

• Irregularly Shaped Voids

• Grainy Material

• External Bubbles

Effects of Mishandling Alginate Impression Materia

Hybrids of alginate and silicone elastomers

Modified Alginates

• Alginot (Kerr)

• Position Penta Quick (3M)

• Silgimix (Sultan Health Care)

• Status Blue (Zenith Dental Products)

Alginate Substitute