MTM® Clear•Aligner: Taking Quality Monophase PVS Impressions

Why the Need for a Good PVS Impression?

The key to case acceptance and proper fitting aligners begins with the impression. There are many techniques that can be used to obtain a PVS impression that will be accepted by the lab. This step by step, Monophase PVS Impression  Guide, details one technique and will help you and yours staff take this type of impression.

  • Impressions and bite registrations must be taken using PVS (Polyvinyl Siloxane) impression material
  • Separate upper & lower impressions are required for all cases
  • Full-arch orthodontic impression trays are provided to allow full capture of tissue to the
    mucogingival junction.
  • Triple trays, partial arch, or trays without sides will not be accepted.
  • Impressions must capture Full distal of the terminal molar
  • No tooth should perforate the PVS impression material or come in contact with the tray

Impressions rejected by the Service Center will cause:

  • Treatment delays/re-impressions
  • More chair time
  • Extra staff time
  • Lost/wasted money (materials and time)
  • Upset patients

PVS Impression Techniques

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Why Not Alginate?

  • Alginate is typically used for study models, temporary removable prosthesis and duplication material
  • Alginate is not dimensionally stable enough to withstand both the transit time and the two pours the Service Center will require in the fabrication your appliance
Factors Affecting PVS Impression Quality

Tray Selection
Use plastic impression trays with retention holes and slits that were
provided with your Patient Case Shipper

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Quality of PVS Material and PVS Tray Adhesive
Figure 1: Use High quality PVS impression material

Figure 2: PVS Tray Adhesice

  • Use only PVS adhesive for PVS impression materials
  • Apply a generous amount inside and the outer edges of the tray
  • Wait at least 5 minutes before loading the impression material into the tray (see manufacturer’s recommendations)


  • Always use nitrile gloves
  • Sulphur in latex / vinyl gloves inhibits the setting of addition silicones
  • Latex may also cause an allergic reaction
  • Avoid scented gloves as it may cause patient to excessively salivate

Material Setting Times

  • PVS Impression materials come in a wide variety of viscosities and set times to accommodate your individual technique and preferences
  • Always follow the manufacturers setting times.
Types of PVS Impression Defects
  • Pulls and Drags
  • Voids
  • Inadequate or Poorly Defined Margins
  • Poor Bond of the PVS Material to the Tray
  • Tooth Contact with the Impression Tray
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PVS Impression Guidelines

  • Rigid, sturdy tray
  • No voids or pulls in margin detail
  • Detailed margins w/o tears
  • No tooth contact with the tray
  • Strong bond between impression material and the tray
  • No dental work should be done after impressions have been taken

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Monophase Impression Technique — Single Viscosity, Single Step
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Step One: Preparation
1. Inspect oral cavity prior to impressions
2. Select the appropriate tray size

Step Two: Load Tray
1. Keep the mix tip submerged in the tray material to prevent voids/bubbles
2. Do not under fill the tray

Step Three: Positioning & Tray Seating
1. Lower Arch: Position yourself behind the patient
2. Upper Arch: Position yourself in front of  the patient
3. insert the loaded tray straight and evenly into mouth, avoid rotation
4. Do not allow the patient to bite down on the tray
5. Hold tray with passive pressure

Step Four: Tray Removal
1. Once impression material has set,remove tray from the mouth
2. Dislodge tray from the posterior on both side and pull straight down
3. Do not use the handle of the tray to dislodge the impression

Step Five: Inspection
Quality impressions should contain the follwoing:

  • No voids
  • No presence of dentition past tray (correct tray size is used)
  • Must capture full distal to the molars
  • No bubbles
  • No slumps or folds
  • Clear gingival margins

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© 2017 Dentsply Sirona.  All Rights Reserved.
#MTML-ITG  RTE-076-17  US version
Issued 4/17

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