Orthotown October 2021 - 30

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Fig. 1
selectively melts each layer of the intended
device, fusing it to the previous layer, all in
an inert atmosphere.
Once the parts have been grown, sigTraditional
bands require separation,
and thus some form of associated chair
time and scheduling for the patient. This
component of the banding workflow can
be eliminated with laser sintering if a band
does not require access to interproximal
areas. A further challenge is introduced
when a traditionally banded appliance is
to be made in a laboratory, rather than in
the office. Traditional bands interact with
interproximal areas, but also regularly
proceed subgingivally. Both requirements
force a laboratory technician to modify
areas of a stone model that are obscured to
them. This creates potential error and leads
to seating and fit issues.
One strategy employed to mitigate this
issue is fixating already-fit bands into an
impression. This method requires chair
time to fit the band, and a high degree of
accuracy and durability when fixating the
bands in the impression. Even slight errors
in fixation or disturbances during shipping
will create difficulty with seating and fit.
Another imperfect solution is to use scans
to size bands. While this improves success
when choosing a band size, it does not
solve the primary issue facing technicians:
concealed anatomy.
To directly address these concerns, a
hypothetical appliance must require no
separators, interact with only the anatomy
that is visible in an impression or scan, and
achieve a fit equal to a custom-fit band.
Laser sintering can yield such an appliance.
Technological
advances
Selective laser sintering (SLS) is not
a new technology, but its application in
orthodontic appliance manufacturing has
become relevant very recently. SLS has
seen applications in the crown, bridge and
removable partial denture spaces for years,
where it has been used to manufacture
frameworks. The process uses a thin bed
of cobalt-chrome (CoCr) powder spread
over a metal build plate. Then, a laser
Discover more online
Great Lakes Dental Technologies is an employee-owned company, with more than
200 employee-owners who design, develop, manufacture and market appliances and
products for use in the orthodontic, dental, and sleep and airway markets. Great Lakes,
one of North America's largest orthodontic laboratories, offers more than 4,000 products
and services, and provides training and education on the latest technology, equipment
and appliance fabrication techniques. Information: greatlakesdentaltech.com
30 OCTOBER 2021 // orthotown.com
nificant processing is required before they
are ready for delivery. The parts remain
attached to the build plate (Fig. 1) and are
placed into a heat-treatment oven to relieve
thermal stresses from the sintering process.
After stress relief, the parts are separated from
the build plate and support structures are
removed. The bands and frameworks can
then be smoothed and polished in preparation
for assembly of the final appliance. Several
smoothing steps are required, which can be
performed either by hand or using isometric
finishing.
Laser sintering requires a large capital
investment compared with traditional skilled
fabrication, but despite this, laser sintering
will become more common and accessible
as the technology matures in dentistry.
The overall quality
of an appliance with
sintered components
is superior to traditionally
banded devices.
To harness additive manufacturing,
parts must be designed digitally. Design
software allows experienced lab technicians
to translate years of traditional bench experience
into digital fabrication. Using a scan
imparts a greater level of accuracy, but more
importantly, it also allows the design of a
custom band without the laborious process
of a wax-up and casting. Technicians can
adapt the shape of a band to visible tooth
surfaces only (Fig. 2), which eliminates the
most common sources of fit issues.
Sintering can be wielded to fabricate
entire space maintainers, bonded lingual
retainers, expander frameworks and any
other component requiring rigidity and
strength (Fig. 3). Any components requiring
precise placement in relation to tissue can be
designed to stay low-profile while avoiding
impingement. Additionally, any traditional
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Orthotown October 2021

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