Pacific Coast Society of Orthodontists Bulletin Summer 2020 - 46

Let's Talk About That

given to some patients to act as a shield to promote healing, and occasionally, it is necessary to
remove the springs for a week and then reinsert
them to allow a cheek ulcer to heal, after which
repeated ulcers seldom occur.
Lacing of both arches with stainless-steel ligature
under the wire is critical; otherwise, unwanted
spaces can develop distal to mandibular canines
and mesial to the maxillary first molars.
Some patients dislike the lower lip fulness that
can be obvious when the pushrod is connected to
the lower archwire distal to the canine brackets.
As an alternative, a 25 or 29 mm pushrod can be
selected and placed on the mandibular archwire
distal to the first premolar brackets.
Occasionally, a lower bracket engaged by the
pushrod will fail. The use of a Unitek bumper or
tie with the bumper facing distal of the lower 3
or 4 cushions the blow of the pushrod and helps
to prevent this, especially in cases of mandibular
arch/skeletal asymmetry (i.e., subdivision cases).
Bending the eyelet of the pushrod to form a 90°
angle to the rod rather than the default 45° angle
prevents buccal flaring of the pushrod during
mastication.
Dr. Christine Mills discusses the Twin Block appliance

Dr. Christine Mills received
her doctorate of dental
surgery degree from the
University of Toronto and
her master's of science
degree as well as her
certification as a specialist
in orthodontics from the
University of Chicago.
Prior to retiring, she
maintained a full-time orthodontic practice in
Vancouver, British Columbia, for more than 30
years, and she was also a clinical assistant
professor at the University of British Columbia,

where she lectured and mentored part-time for 25
years in the Faculty of Dentistry's orthodontic
department.
1. When would the ideal time be to start treatment using your appliance? For the patient
described, I would start treatment immediately
with full-time wear of a Twin Block appliance
(TBA), in the hope that there is still adequate
growth potential remaining to achieve a good
skeletal correction. Ideally, I prefer to start skeletal
Class II correction much earlier, doing a Phase I
treatment with the TBA in the mixed dentition
stage, at approximately nine years of age. Early
intervention is preferable because it allows ample
time to get the maximal skeletal correction of
the mandibular deficiency while steady growth
is guaranteed. Why wait until the last minute, as
in the described patient, when her growth spurt
may be ending soon?
2. Would you use a one-phase or two-phase
treatment? The described patient's treatment
will involve two phases. The first phase, with
the TBA, will be directed at correcting the A-P
discrepancy (excessive overjet) by encouraging
forward growth of the mandible. The TBA will
also correct the vertical discrepancy (deep overbite) by encouraging eruption of the lower first
molars. Finally, the TBA will correct any transverse discrepancy by allowing for some maxillary
expansion (1/4-mm per week). This is almost
always required when the mandible is advanced
forward.
The second phase of treatment will involve a
short period of fixed edgewise appliances to correct any dental alignment issues such as crowding, spacing, rotations, and generally detailing the
occlusion.
3. Which appliance would you use? Please be
specific, including any teeth to be bracketed. The
TBA used during active treatment would require
arrow clasps or Adam's clasps for retention on the
maxillary first molars as well as on the maxillary

PCSO Bulletin Summer 2020

Pacific Coast Society of Orthodontists Bulletin Summer 2020

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Summer 2020