Pacific Coast Society of Orthodontists Bulletin Winter 2023 - 58

Doctors
What If I Am Placing a U/L Fixed Retainer?
You can anticipate where the fixed retainer will be and
digitally block out the area.
What If I Don't Have a Printer?
You can outsource your printing until you decide
whether your workflow would benefit from an in-office
printer.
What If I Want To Debond, Scan, and Deliver the
Retainers All in One Day?
Scan your patient following debonding, print the
models, make the VFR, and ask the patient to return
later in the day to pick up their retainers and models.
Application of In-House Aligners
In-house aligners are useful for treating minor posttreatment
changes. Although the previous treatment
of choice for minor relapse was the finger spring
retainer, Dr. Larson has largely migrated toward inhouse
aligners to treat these patients. To fabricate his
in-house aligners, Dr. Larson uses software from uLab,
a company that has pioneered an automated system
that helps clinicians resolve minor dental changes
following treatment. Dr. Larson recommends that
clinicians interested in making in-house aligners take
a mastery course. He also urges clinicians interested
in adding 3D printing to their practice to consider the
necessary counter space for the printer, the curing
oven, and the wash station. The 3D printer also should
not be near any model trimmers because the dust
from these trimmers can negatively affect the printer.
Clear Aligner Properties
Although orthodontists often focus on the characteristics
of arch wires, the properties of clear aligners are
equally important. These properties include impact
strength, stiffness (elastic modulus), creep (dimensional
stability), resistance to fracture, shrinkage due
to polymerization, discoloration, and environmental
impact. Discoloration and fracture resistance may
be more important issues in retainers because these
appliances are intended for long-term use. Although
some data are available on the differences between
clear aligner materials, not much is known about the
clinical application of this information.
Incorporating Science to the Fabrication of Inhouse
Aligners
In 2021, John Morton of Align Technology1
spoke
about the significance of incorporating biomechanics
into clear aligner force systems. He discouraged
adopting the common conception that clear aligners
are a displacement-driven system, that the tooth
should follow the position of the aligner. This misconception
excludes the biomechanical principles
of moments and forces. Morton stressed that the
principles of arch wires, such as overcorrection and
force systems, should be incorporated into the design
of clear aligners.
What Is the Effect of Trim Margin and Material on
Clear Aligners?
A scalloped margin follows the tooth margin,
whereas a straight trim margin is cut straight 0.75 to
1.5 mm apical to the marginal gingiva. Brown2
found
that the trim line affects the forces created three
times more than the material used to fabricate the
aligner. Zendura FLX aligner material generated lower
forces and moments than did Essix ACE material,
although Essix ACE expressed greater facial strain.
No difference between the materials was noted on
lingual forces. Regarding margin trim, straight margins
expressed greater facial strain than did scalloped
margins. Biomechanically, a straight gingival margin
may be helpful when designing more complex tooth
movements, especially when force is demanded near
or at the gingival margin. Passive clear aligners and
retainers may unintentionally express forces to the
teeth.
What Is the Effect of Attachment Size?
Slama3
measured extrusive forces on a central incisor
delivered by no attachment, a small attachment, a
medium attachment, and a large attachment. He
found that attachments are effective at increasing ex58
PCSO
Bulletin Winter 2023
Pacific Coast Society of Orthodontists Bulletin Winter 2023

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Winter 2023
