Pacific Coast Society of Orthodontists Bulletin Spring 2018 - 50

Presentation Summary

Doctors

The Need for Speed: Separating
Biology from Biomechanics
Dr. Bruce Hawley
PCSO Bulletin Columnist

Presented by Dr. Chung Kau at the PCSO Annual
Session, Oct. 14, 2017
Each year, around 3.5 million individuals seek
orthodontic treatment, a potential $20 billion
industry. There has been a significant increase
in the number of adults seeking orthodontic
treatment in the past decade, reflecting a changing marketplace in an evolving specialty. In
orthodontics, both planning and execution are
important.

Dr. Chung Kau
Chairman and Professor,
Department of Orthodontics,
University of Alabama
at Birmingham

Biology of Tooth Movement
There are four main classic theories on tooth
movement, all of which are applicable: biomechanical, piezoelectric, pressure/tension, and
hydrodynamic. In reality, tooth movement is an
inflammatory response: fluids in the periodontal
ligament (PDL) move, resulting in bone remodeling; the tooth moves into a new position through
osteoclastic activity on the pressure side and
osteoblastic activity on the non-pressure side.
There is an initial phase involving PDL compression, followed by a lag phase and a post-lag
phase. Light forces are probably better than
heavy ones; they tend to keep the PDL intact and
minimize tissue necrosis and undermining
resorption. Heavy forces tend to cut off blood
flow by occluding blood vessels.
Device-Assisted Therapy
Is there an alternative to conventional biomechanical systems, which may help to accelerate
orthodontic treatment? Electric current, magnetics, and lights have been tried. Is this science or
myth? Are we in control here or merely rendering
"cartoon-a-dontics"? Surgical interventions such
as osteotomies, interseptal surgery, and corticotomies have all been used. In humans, there tends
to be a 2.5-fold increase in the rate of tooth
movement in the first two months after surgical
intervention, with rates returning to those of
controls in the fourth month. In 2010, Propel Orthodontics began marketing micro-perforations/

microtrauma as a somewhat less barbaric
approach than corticotomy. While this intervention seems to work in a majority of cases, largescale studies are needed. We need to look at
the morbidity issues and realize that microperforation is not a continuous or long-lasting
effect, and probably not a great practice builder.
Acceledent markets a commercially available
cyclical forces therapy device on the theory that
vibration of teeth will increase the rate of tooth
movement. This device uses gentle pulsing with a
low vibratory effect. Histologically, bone-forming
cells form around the teeth to be moved. Dr. Kau
believes that compliance is crucial: Acceledent
advocates that the protocol be used for 20 minutes per day, but the patient compliance rate
is only around 67%. As yet, we have minimal
science available to verify the effectiveness of
this approach.
Photobiomodulation, or the application of a lowlevel laser, utilizes mitochondrial absorption of
photons, increasing ATP production and the formation of red blood cells. There is some evidence
that it seems to help, approximately doubling
alignment speed but with no increase in space
closure in human premolar extraction cases.
There is considerable human variability, with different cellular responses in different individuals.
Finishing in Orthodontics
Successful orthodontic treatment involves:
1. Developing a road map
2. Determining the foundation by keeping teeth
within the bone
3. Planning the limits
4. Executing the plan
The more you practice, the less you know! Begin
with the end in mind and know your system. Be
smart about your mechanics, realizing that tipping happens immediately and root movement
takes much longer to occur. Take time to finish,

PCSO Bulletin  Spring 2018

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Spring 2018