What causes unclear margins in dental impressions?
Dental labs report that it is common to receive impressions with obscured margins. This causes the dental lab to guess where the margin ends which can result in a poor-fitting restoration. Learn common ways to adjust the dental impression procedure to ensure margins are sharp.
Browse this page to read about common issues and find solutions and tips to eliminate unclear margins. You can also request to download a PDF of the full guide.
Thick blood/saliva pooled around the preparation
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What can you do:
Rinse and dry the prepared area and stop any bleeding by using appropriate retraction technique and a hemostatic agent. Liquids or pastes based on aluminum chloride, aluminum sulfate, or iron sulfate are suitable hemostatic agents.
3M™ Astringent Paste supports your impression work with excellent gingiva retraction with or without cord and hemostasis.
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.
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.
Working time exceeded, flowability already impaired
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What can you do:
Select material with sufficient working time (i.e. regular set instead of fast set). Make a choice depending on the individual situation and preference of material. Do not exceed working times given in the instructions for use. In case of 3M Oral Care materials follow given intra-oral syringing times for wash materials.
Pay attention to storage temperature. 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.
3M™ Impregum™ Soft Polyether Impression Material offers a very long working time with constant flow. And, polyether impression material is less temperature sensitive in its setting reaction than VPS materials.
3M™ Imprint™ 4 VPS Impression Material offers both a fast and a regular setting material. Select Quick Set for 1 to 2 unit cases and Regular Set for cases that involve 3 or more units.
Impression material stored at too low temperature
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What can you do:
Temperature influences the viscosity. Store impression material at room temperature. Lower temperatures might lead to higher viscosities.
Incorrect storage conditions of the final impression
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What can you do:
After disinfection rinse impressions with water and dry before sending it to the lab.
Store impressions at room temperature and away from direct sunlight.
Inadequate disinfection
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What can you do:
Use recommended disinfectants. Follow the manufacturers’ instructions for use. Do not exceed the immersion time.
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.
