impression

Written by Andrew Sedler

Written by Andrew Sedler

Written by Andrew Sedler

Impression Troubleshooting Guide
The Foundation of Successful Restorative Cases
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impression troubleshooting - best dental lab usa

The foundation of any successful restorative case begins with an accurate, detailed impression. At Burbank Dental Lab, we see hundreds of impressions every day, most of which are of very good quality. However, we also see impressions that have issues. There are also impressions that look fantastic but have hidden problems that cause challenges for both parties. We have found that even the most experienced dental practitioner can encounter difficulties when making an impression. Even the slightest inaccuracy is amplified as the restoration progresses from model to wax/digital mockup, to milling, to final seating.

What You Will Learn In This Article

  • Highlight several of the most common problems that we see in the lab.
  • Present how to identify the problem before sending it into the lab.
  • Show how to avoid the root causes of common problems.

Problem 1: Inadequate Margins

Impression problem: Inadequate margins

Causes & Solutions

Insufficient tissue management

Solutions:

  • Ensure good tissue management - no gingivitis or bleeding sulcus. 
  • Double cord technique may alleviate.
  • Use gingival retraction clay/paste such as Espasyl-Kerr, Access-Centrix Inc., Astringent Retraction Paste-3M.

Insufficient wash material

Solution:

  • Keep the mix-tip permanently immersed in the paste to avoid the formation of air bubbles. Apply a liberal amount of wash material into the sulcus. Start from the bottom up and cover the whole abutment tooth with the syringing material. Always keep the tip in close proximity to the surface.

Void caused by syringe technique

Solution:
  • Keep tip continually submerged within impression material and sulcus.

Tearing of the margin

Solution:

  • May require a wash material with a higher tear strength.
  • Additional tooth preparation in a margin area to create a more adequate sulcus impression material width.

Problem 2: Air Bubble On Margin

Air bubble on margin

Voids on the margin or occlusal of an impression can compromise the restoration’s fit and function. When voids occur on occlusal surfaces, it is not possible to properly articulate models.

Causes & Solutions

Improper syringe technique

Solution:
  • Keep tip continually submerged within impression material and sulcus
  • Use a stirring motion while syringing, making sure to keep the syringe tip immersed to avoid trapping air.

Blood/saliva contamination around preparation (Figure 3)

Blood/saliva contamination around preparation

Figure 3

Solution:
  • Ensure good tissue management, with no gingivitis or bleeding sulcus. 
  • Double cord technique may alleviate.
  • Use gingival retraction clay/paste such Espasyl-Kerr, Access-CentrixInc., Astringent Retraction Paste-3M. (Figure 4)

Using gingival retraction clay

Figure 4

Exceeding the working time of material reduces the hydraulic action of the wash to be expressed into the sulcus

Solution:

  • Follow the manufacturer’s working time specification.

Problem 3: Tight Crowns

Causes & Solutions

This problem can be caused by several of the following factors.

  • Early removal of the impression tray from the mouth.
  • A poor bond of the material to the tray, or seating an impression tray with material that is partially set. 
  • Inserting the impression tray after it has begun to set. 
Solution: 
  • Closely follow the recommended working and setting times and always use a VPS tray adhesive according to instructions.

Problem 4: Short Crowns

Causes & Solutions

Trays with weak or low walls can provide insufficient support during impressioning, causing short crowns.

Solutions:

  • To address this issue, use custom or rigid trays — preferably metal.  (Figure 5)
  • Short crowns can also be due to teeth coming into contact with the tray during impressioning; confirm that teeth do not touch the tray.

 

Rigid trays

Figure 5

Problem 5: Drags / Pulls In Impression

Causes & Solutions

The tray seating step presents the possibility for a number of errors. If drags and pulls are an issue, try not to seat the tray too rapidly. (Figure 6)

Drags and pulls

Figure 6

 
Solutions:
  • Position the tray before seating, and use a slow, steady, vertical seating motion. Drags or pulls can result when the tray is placed and seated in one motion. To avoid drags, carefully position it in the mouth before seating it slowly and carefully. Avoid contact of teeth with the tray.
  • Be sure to adhere to the manufacturer's directions, as seating after the material has begun to set can cause this problem as well.

Problem 6: Surface Inhibition - (Figure 7)

Surface inhibition

Causes & Solutions

Surface inhibition can occur when impression material is exposed to residues from custom temporary materials or powder from latex gloves. This results in the surface of the impression material not setting properly, feeling tacky to the touch, and visually resembling the surface of an orange peel.

 
Solutions:
  • Avoid this problem by waiting to fabricate the temporary crown until after the final impression has been made.  
  • Use an alcohol wipe to remove the air-inhibited layer on any composites, adhesives, or core buildups in the impressioning area.  
  • Use non-latex or powder-free gloves. 
  • Rinse retraction cord thoroughly before removal to eliminate sulfur-based contaminates from hemostatic agent or glove.
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GUIDELINES FOR A GOOD IMPRESSION

  • 1

    Uniform, homogeneous mix of material

  • 2

    The tray is sufficiently filled with impression material

  • 3

    Thoroughly-applied tray adhesive

  • 4

    Rigid, sturdy impression tray

  • 5

    No voids or pulls on margin detail

  • 6

    Detailed margins with no tears or rough surfaces

  • 7

    No tray show-through of the impression material

  • 8

    Good blend between heavy body and light body materials

  • 9

    A strong bond between impression material and tray

  • 10

    No tooth contact with the tray

  • 11

    Complete information about the impression material used provided to the dental laboratory

Burbank Dental Lab is dedicated to facilitating your practice success, and we make every effort to communicate with our clients regarding what we observe regarding impressions and other patient records. Our goal is to be an integral part of your dental team, to create Smiles By Design® together with you.

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Fabrication
of the future
is here!

Burbank Dental Lab has three new state-of-the-art Carbon M2 printers. We are very excited about the options that these cutting-edge printers will allow us to offer our dental clients. Here are some of the advantages that these printers will begin to deliver to you and your dental practice.

Our New
State-Of-The-Art
3d Printers

Carbon offers a highly dependable 3D manufacturing solution for many dental applications with its breakthrough Digital Light Synthesis™ technology, enabled by a wide range of dental materials.

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