Ch 27 Taking Alginate Impressions

What is the most common method for obtaining diagnostic casts?

use of alginate impression

Advantages of alginate impressions

pleasant taste
inexpensive
easy to manipulate
adequately reports details

What is the most common method for obtaining diagnostic casts?

use of alginate impression

Advantages of alginate impressions

pleasant taste
inexpensive
easy to manipulate
adequately reports details

Positive reproductions of the patient's dental arches and surrounding tissues

study models and study casts

What is the purpose of taking an alginate impressions?

to make an accurate reproduction of the maxillary and mandibular arches and adjacent tissues

What is the purpose of the perforations in tray?

alginate will flow into the holes when in dental arch - act as retentive mechanism to keep set alginate from separating from the tray upon removal

What developmental anomalies may affect proper selection of tray size?

mandibular tori and maxillary exostosis -- wider or larger tray may be necessary for patient comfort

5 Properties to consider when choosing tray

1. extend facially to include all teeth and musculature of vestibule
2. extend distally 2 to 3 mm beyond last tooth
3. provide a 2 to 3 mm depth beyond occlusal surface and incisal edge
4. comfortable for patient
5. some metal trays may be bent

When should trays be steralized?

after each use or tried use for proper fit

What is the purpose of rope (beading) wax?

protects tissues from injury, extends the tray, and may aid in retention of alginate material within tray

Where may wax be placed?

periphery of tray and palatal area

Why is wax placed on palatal area of tray?

support alginate in high vault and to avoid trapping air

What is average setting time for alginate material?

3 to 4 minutes

What should you instruct patient to do if they are uncomfortable during impression procedure?

instruct patient to raise hand - do not talk

What should be provided to protect patient clothing?

napkin and paper towel

How do you minimize patient's gag reflex while taking impressions?

have patient breath in and out through nose - seated in upright position - avoid touching tongue (especially the base)

What should be removed before impression procedure?

all removal prostheses

Why should fixed appliances be covered in wax?

to prevent alginate from locking under crowns and pontics - which may cause tearing

How does preprocedural mouth rinse result in more accurate impression?

reduces bacterial load, debris, and saliva

What impression should be taken first?

mandibular arch

What is regular setting time?

approximately 3 to 4 minutes (fast setting 1 to 2 minutes)

What is average working time? (time taken to mix)

approximately 1 minute

If using bulk materials, after shaking can how long should clinician wait before opening the lid?

30 seconds

Cooler water will have ____ working time.

longer

Warmer water will have ___ working time.

shorter

Armamentarium for Taking Alginate Impressions

Impression Trays
Rope (beading) Wax
Rubber Mixing Bowl
Alginate Spatula
Alginate Powder
Measuring Scoop for Alginate
Water Measurer
Tap Water
Disinfecting Solution
Mouthwash
Infection Control Attire
Air/Water Syringe
Gauze

What is a homogenous mixture?

one that has smooth consistency

How do you eliminate trapped air from loaded impression tray?

using the tip or the end of the spatula

Why is it important to moisten and smooth the alginate?

create a smooth surface and decrease formation of air bubbles

What is appropriate clock position for seating mandibular impression?

7 o'clock

What is proper location of occlusal plane when seating mandibular impression?

parallel to floor

Where should the tray handle be aligned?

with patients midface

What is proper clock position for seating maxillary impression?

11 o'clock

Why is it important to rub a small amount of alginate on occlusal plane and interproximal surfaces during impressions?

to eliminate air bubbles in the impression

Should impression be set first in the anterior or posterior?

posterior

How can patient decrease gag refex?

breathing through nose and slightly tipping head down

What is function of both hands during removal of impressions?

dominant hand removes impression - free hand used to stabilize the arch

How can a suction seal be broken?

place index finger under periphery of posterior portion

What are important post removal procedures?

have patient rinse mouth to remove excess alginate and remove any excess alginate from interproximal areas - use moistened towel to remove alginate from face and lips

What is proper disinfecting technique for trays?

1. rinse with water to remove any debris
2. gently shake off excess water
3. spray with disinfectant
4. place in plastic bag
5. disinfect for 10 minutes
6. rinse again with water and dry