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Fabrication of Upper & Lower Essix ‘C’ Retainers

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The following walk through shows one method of fabricating Essix retainers using a Bio Star machine.

The design and finishing periphery are the standard design used at the Royal Lancaster Infirmary (unless otherwise stated by the clinician). All photographs, text and fabrication by Mr. Andrew Tinkler at the Orthodontic / Maxillofacial Laboratory—Royal Lancaster Infirmary.


Both upper & lower Essix models are trimmed up as shown in the picture above and any anomalies removed with an Ash 5 / 9.



Laboratory work sheet, impressions and centric wax bite were received from the clinic, upper & lower impressions cast for Essix models and also cast a second time for one set of Study Models. The Study Models are trimmed up in the usual way and then Par Scored.

A Bio Star machine is being used here. The picture shows the upper model in position on the platform and the Essix retainer blank in position prior to heating.

The heating element is then moved over the Essix retainer blank.

The Bio Star machine will alert you when to close the chamber over the upper model and the locking arm should be moved in to position. The chamber will be held under air pressure during the cooling phase.

The Bio Star machine will again alert you when to evacuate the chamber.

The formed blank and upper model are then removed from the machine. The same method is carried out for the lower model.

At this stage the excess blank material needs to be removed. It is often easier to use scissors to make the initial cut up to the palatal / lingual area.

At this stage the excess blank material needs to be removed. It is often easier to use scissors to make the initial cut up to the palatal / lingual area.

A bur is then used to cut through the Essix material. This should be done to approximately 7mm in the palatal / lingual area and 3mm away from the gingival margins in the buccal and labial areas.

Please view the following series of photographs for guidance on removing the excess blank material

This picture shows the excess blank material removed from the upper model.

This picture shows the upper and lower Essix blanks removed from their models and ready for trimming to the design specified by the clinician. For this stage of the trimming, a metal acrylic bur is used.

This particular design required the Essix retainers to extend around the distal area of the upper molar teeth. See final pictures for further guidance.

Extends along the gingival margins and into the palate a distance of 5-6mm. See final pictures for further guidance.

A similar design is used for the lower retainer.

This picture shows a second bur been used to remove any small particles from the periphery of the retainer caused by the roughness of the previous metal acrylic bur. N.B. This stage may or may not be necessary prior to polishing on the lathe using pumice.

The periphery of both upper and lower retainers are then lightly pumiced on a lathe. N.B. Remember it is only the periphery of the retainers that should be pumiced and not the whole surface of the appliance.

The retainers are then rinsed free of pumice using cold water. N.B. Hot water is not used to rinse the retainers because this would heat the material of the retainers and risk distortion of the appliance. This picture and the following pictures show the finished upper & lower retainers in position on their models.

This picture shows the palatal view of the upper retainer in position on its model. Again note the position of the finished periphery—approximately 5-6mm away from the gingival margins.

Questions and answers regarding this walkthrough

Question

Authors answer

Hi, sorry for this but noticed something on the walk throughs and have to make comment. The fabrication of 'Essix C' retainers, showed the material only cover upto the first molars on upper and lower, thus leaving the second molars to over-erupt. Just thought i'd bring it to your attention.

Thanks for the enquiry regarding coverage of the second molars when fabricating an Essix C retainer.

At the Royal Lancaster Infirmary, the Laboratory staff and the clinicians have decided to 'end' the Essix retainers distal to the 6's for a number of reasons: - In a large number of cases at Lancaster, the second molars are still erupting, therefore covering them is obviously not an option.  Also, it has been noted (by clinicians) that it is difficult to guarantee that the 7's have fully erupted and the clinician in this case (not covering the 7's), will take responsibility for the control of the eruption of the 7's and make adjustments to the treatment if necessary. 

Also, and as a minor concern, the accuracy of the impression cannot always be relied upon in the second molar region.

Hope this clears things.  Even though these 'walk throughs' are peer assessed, its amazing the number of 'points of interest' are brought to peoples attention.

Every contributor to the techniques site are describing their own particular technique for fabricating an appliance / component and there will obviously be many variations on these techniques.  The original Essix retainer only covered the 3 - 3's for example.

Thanks again for your observations and its good to know that some people are taking an interest in our techniques section of the site!

Do you wish to discuss this case? Email the author HERE

For further information contact : -

  • Mr. Andrew Tinkler. LOTA.
  • Maxillofacial Laboratory,
  • Royal Lancaster Infirmary,
  • Lancaster.
  • LA1 4RP

Peer assessed by: -

  • Mr. C. Bridle. FOTA.
  • Orthodontic Laboratory,
  • Royal Hampshire County Hospital,
  • Winchester,
  • Hampshire.
  • SO22 5DG