Tissues Treatment before Impression Department of Prosthodontics Dr. Lan Jing.

Tissues Treatment before Impression

Department of Prosthodontics Dr. Lan Jing

Biologic Width

review

Preparation Margin

Extra sulcular

Intra sulcular

Esthetic Good Retention Prevent Radicular Caries Control Ferula Effect

The weak link between the tooth and the restoration is the correct impression

Definition: the deflection of the marginal gingivae away from a tooth

Purpose:• expose the finish line • provide a space for

impression material

gingival displacementgingival retraction

the techniques used for gingival displacement

• surgical method• mechanical method• chemico-mechanical method

Chemico-Mechanical Method

Retraction Cord

Chemical drug

• Epinephrine• Aluminum Chloride • Alum(aluminum potassium sulfate) • Ferric Sulfate • Aluminum Sulfate

Double Cord Technique: using two cords I like use #00 and #0

Single Cord Technique: using only one thick cord I like use #1

Techniques:

Double Cord Technique First cord--------thin cordat bottom of the gingival crevice （龈沟） vertically and horizontally displace gingival margins It is not removed during impressing

Second cord--------thicker cordon top of the first cordachieve horizontal tissue displacementremoved immediately before impressing (sulcus closes in less than 30 sec).

Very importan

t

1. Clean the preparative tooth2. Place the #00 cord3. Complete preparation4. Place the #0 cord5. Take the impression after 5-

10minutes removing the #0 cord

Double Cord Technique

Procedure:

Contraindication （禁忌症） :Patient with thick periodontal tissue

Very import

ant

Attentions:• Select an appropriate size of cord• The strength is softly, and the angle between cord

packer and tooth axis is an acute angle• Firstly place the cord in the proximal area, then to

lingual or buccal area• Moisten the cord before remove it to prevent gingival

injury

• surgical method• mechanical method• chemico-mechanical method

Questions:What is the purpose of gingival

displacement?

How many methods could retract gingivae?

Grasping Content:Double cord technique

Wassell RW, Barker D, Walls AWG. Crowns and other extra-coronal restorations: Impression materials and technique. British Dental Journal 2002,192;679 - 690

References:

Thanks for your attention

Jing LanE-mail: [email protected]: 88382058