What piece of equipment is required for making a close fitting dental
tray such as that that might be used for whitening purposes. After
making a quick drying impression with the pink powder and water, how
is this transferred into the permanent flexible plastic mould and
where might I view the equipment needed?

Hi drydoc,

Thank you for your question! Having undergone the fun and games
associated with professional tooth whitening, your question piqued my
interest.

As you mentioned, the dentist's first step is creating an impression
of the patient's teeth. From this impression, the dentist or dental
technician makes a plaster replica of the teeth. From there, a
technician creates a flexible bleaching tray to fit the plaster mold,
which in turn will fit the patient's actual teeth.

With many over-the-counter bleaching kits, customers can actually
create their own impressions with a powder mix included in their kit.
Customers mail the impressions to a laboratory, whose technicians in
turn create the plaster molds and bleaching trays.

This brings me to your question - how are the bleaching trays actually
created? Here's a mouthful for you, from a study titled "Evaluation of
Tray Fabrication Design and Effects on Vital Tooth Bleaching":

"Plastic sheets 0.040 thick and 5x5 inches square were used with a
Sta-Vac vacuum form machine (Buffalo Mfg. Co). Each tray was trimmed
approximately 1 millimeter short of the gingival margin to prevent
oral soft tissue irritation. The margin was flamed to increase
adaptation to the casts. Trays were tried in the subject’s mouth and
trimmed if indicated."
(http://www.discusdental.com/clinical/trays.html)

The USAF Dental Investigation Service, referring to the Zaris
Professional Tooth Whitening System by 3M, describes the process more
succinctly:

"One-millimeter-thick clear tray blanks are provided and are used with
a vacuum machine to make the bleaching trays."
(http://www.brooks.af.mil/dis/Dis61/sec12.htm)

Essentially, dental technicians use a small heated vacuum to shape a
pre-cut square of vinyl bleaching tray material to the patient's
plaster mold. Resin spacers are sometimes used in creating the trays
to create reservoirs for the bleaching solution. Once shaped, the
bleaching trays are trimmed and smoothed for a better fit and to
prevent gum irritation.

Ultradent Products Online has a number of bleaching tray materials and
equipment available for viewing and purchase, including:

Regular and micro-torches, for smoothing dental tray edges to prevent
discomfort and abrasion
<http://www.ultradent.com/toothwhitening/Blazer%20Micro%20Torch/blazermicrotorch.htm>

Sof-Tray Sheets
<http://www.ultradent.com/toothwhitening/Softraysheets/softraysheets.htm>

Ultradent LC Blockout Resin, for creating reservoirs in bleach trays
<http://www.ultradent.com/toothwhitening/lcblockout/lcblockout.htm>

Ultradent Utility Vinyl Cutters, for trimming tray material
<http://www.ultradent.com/toothwhitening/vinylcutters/vinylcutters.htm>

UltraVac - heated vacuum for shaping tray blanks
<http://www.ultradent.com/equipmentanddevices/ultravac/ultravac.htm>

Many schools, like the University of North Carolina, offer crash
courses in dental tray fabrication. Here's the scoop on UNC's
Professional & Predictable Take Home Whitening seminar:
<http://www.dent.unc.edu/ce/cde/courses/listcourse.cfm?MeetingCode=04-DE-006>

The Global Online Dental Education Network offers a webcast course
titled Immediate Fabrication of Direct Thermoplastic Whitening Trays.
This is a shorter process in which a dentist essentially creates
bleaching trays directly in a patient's mouth, without creating
plaster molds. See the following URL:
<http://www.dentrek.com/webcasts/cewebcasts_descrip.asp?x_ID=122> 
 
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All the best!

Emjay-ga