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Tearing at the Margin
What causes dental impressions to tear at the margins?
Visible rips or tears on the margin of the preparation can result in short crown margins and/or open margins. Learn common ways to adjust the dental impression procedure to minimize tearing.
Browse this page to read about common issues and find solutions and tips to eliminate tearing at the margin. You can also request to download a PDF of the full guide.
Insufficient retraction
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What can you do:
Retract gingival tissue to entirely capture the prepared area. Retraction cords as well as retraction pastes are suitable.
3M™ Astringent Paste supports your impression work with excellent gingiva retraction with or without cord and hemostasis.
Inhibition of setting due to use of acidic retraction materials/hemostatic agents like aluminum or ferric salts
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What can you do:
Thoroughly rinse preparation with water and dry before taking the impression.
Smear layers from custom temporary, provisional cements (acrylics) or core build-up present
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What can you do:
Smear layers from acrylates (e.g. core build-up or temporary materials) can inhibit the setting of impression materials.
When core build-up and final impression are made in one appointment:
- Be sure to remove the smear layer completely prior to impression taking with alcohol/by polishing. Check surrounding teeth and tissue for any residue.
When the temporary and final impressions are made in one appointment:
- Fabricate the provisional after taking the final impression or remove the air-inhibited layer on the exposed preparation with alcohol before taking the final impression.
- Do not use impressions already used to fabricate the provisional for subsequent precision impression taking.
- If a temporary is removed prior to impression taking: Remove all residues of cement and clean the abutment tooth. In case of a core build-up remove the air-inhibition layer on the exposed preparation with alcohol before taking the final impression.
Inadequately mixed materials
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What can you do:
Bleed cartridge before applying the mix tip to ensure even dispensing. Then use the mix tips recommended by the manufacturer and dispense a pea-sized amount onto a mix pad prior to use.
Premature removal of the impression
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What can you do:
Follow manufacturer's instructions for intra-oral setting time and make sure that the impression material has completely set before removal.
Store impression material at room temperature. Usually, times given in the manufacturer’s instructions for use are valid for a storage temperature of 23 °C/74 °F. Working times are reduced due to higher temperatures of the product, while intra-oral setting times might be longer if the temperature of the product is lower.
Inhibition of setting of VPS impression materials due to contact with sulfur from latex gloves
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What can you do:
Use gloves which do not contain traces of sulfur, e.g. nitrile gloves.
Impression material has low tear resistance
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What can you do:
Let the material completely set prior to removal of the impression and use impression material with sufficient tear resistance.
All 3M Oral Care precision impression materials offer clinically proven tear resistance.
* Images: Highly detailed impressions made with 3M™Impregum™ Polyether Impression Material (top) and 3M™Imprint™ 4 VPS Impression Material (bottom).
Expired impression material
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What can you do:
Do not use expired impression material.
Follow defined storage conditions for materials given in the instructions for use for full shelf life.
Not seeing what you need?
Download our comprehensive guide to troubleshooting most common dental impressioning issues, including a bonus section on 10 Golden Rules for Taking Perfect Dental Impressions.
