Orthotown October 2016 - 47

Designing
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With digital indirect bonding, both the designing and
production of transfer trays are automated. Isolating the
designing from production allows the opportunity to verify bracket positions before making the tray. Adjustments
of the design can be made without wasting materials, and
can be completed in less time than remaking a poorly
fitting tray.
Instead of a lab technician shaping the tray on a dental
model while making the layers of the tray, covering the
brackets and trimming excess material, digital methods
enable custom shaping of the coverage of each bracket so
it doesn't have too much or too little material holding it in
the tray. The doctor can digitally specify the contours of
the tray to prevent brackets from being trapped in it.
Since trays are designed in the software, no physical models
are required for placing brackets. Bracket positions on the
virtual setup are precisely matched on the virtual tray. This
gives the doctor final say about the bracket positions, before
the tray is made.

Production
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With increased availability and affordability of 3-D printers,
orthodontists can do 3-D printing in their own offices with
no lab fees or lengthy delays for shipping. Outsourcing to a
lab for production is unnecessary.
The 3-D printer must be capable of printing the fine details
of the brackets; otherwise, the brackets won't fit correctly in
the tray-even if it was designed perfectly.
Three-dimensional printing the transfer tray eliminates the
former need for a dental model when making the tray. Only
a single material is needed for the tray, and no thermoforming is involved.
Using a printing material that makes the tray rigid gives the
tray a positive "stop" when placed on the teeth.
Before starting bonding, it's important to practice putting
the rigid tray on and off the patient's teeth, to find and

*
*
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relieve undercuts so that the tray has a passive fit. It shouldn't
snap into place-the tray should be passively seated in the
correct position without any secondary movement because of
being too loose.
While designing the tray, or after printing it, the tray can be
split into segments that make insertion and removal simpler.
When the tray is designed and produced to fit passively, no
finger pressure is needed to hold each segment on the teeth.
After attaching and curing the brackets on the teeth, the tray
can be gently lifted off, presuming the tray design doesn't
trap brackets in their spaces and the undercuts have been
properly relieved.

Outcomes
An indirect bonding system with the previously mentioned
features for planning, design and production can yield multiple
favorable results.
Accuracy: With digital treatment planning, digital tray
designing and onsite 3-D printing, direct-to-ideal tooth positions
and bracket positions are possible. That precision greatly reduces
rebond appointments and round-tripping of teeth. True straight-wire
treatment can be used and minimal (if any) robotic wire-bending
is needed, because the brackets are where the doctor wants them.
Timing: Working entirely in the doctor's own office contributes
to shorter overall treatment time. No need for technique-sensitive
manual production of transfer trays. No need for back-and-forth
with labs to verify that technicians have correctly placed brackets,
and no worrying that appliances will arrive in time for the bonding
appointment. Transfer trays can be designed, printed and used promptly.
Expenses: Costs such as these can be greatly reduced, and
even eliminated, by using digital indirect bonding and in-house
3-D printing:
* Lab services and materials for transfer tray designing
and production
* Wire-bending services
* Shipping
* Dental models for setups
* Rebond appointments
* Remaking of trays that may not fit because of changes with
the patient's dentition (such as eruptions) during the delay
for arrival of the trays.
orthotown.com \\ OCTOBER 2016

http://www.orthotown.com

Table of Contents for the Digital Edition of Orthotown October 2016