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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 .
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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
gingival displacement gingival retraction Definition: the deflection of the marginal gingivae away from a tooth • Purpose: • expose the finish line • provide a space for impression material
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
Techniques: • Double Cord Technique: using two cords • I like use #00 and #0 • Single Cord Technique: using only one thick cord • I like use #1
Double Cord Technique First cord--------thin cord at bottom of the gingival crevice(龈沟) vertically and horizontally displace gingival margins It is not removed during impressing Second cord--------thicker cord on top of the first cord achieve horizontal tissue displacement removed immediately before impressing (sulcus closes in less than 30 sec). Very important
Double Cord Technique Very important Procedure: • Clean the preparative tooth • Place the #00 cord • Complete preparation • Place the #0 cord • Take the impression after 5-10minutes removing the #0 cord Contraindication(禁忌症): Patient with thick periodontal tissue
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
References: Wassell RW, Barker D, Walls AWG. Crowns and other extra-coronal restorations: Impression materials and technique. British Dental Journal 2002,192;679 - 690
Thanks for your attention Jing Lan E-mail: jinglan@sdu.edu.cn Tel: 88382058