Casey CastaldiCRD 118Fall 2013The Evolution of Dental
BracesHuman beings have historically been characterized as being a
particularly inventive species. Throughout history, we have
invented technologies to meet out basic human needs in creative
ways. However, the inventive capacity of human beings is not
limited to necessity. In his book about the evolution of
technology, George Basalla states, If technology exists to meet
basic human needs any complexity that goes beyond the basic
fulfillment of needs could be judged superfluous and would need to
be explained on ground other than necessity.(Basalla, 1988). The
desire for straight teeth did not originate from a direct human
need. In fact, human beings survived and thrived for thousands of
years without any form of intervention. However, at a certain point
in human history, standards of beauty forever changed in a way that
produced a desire for straight symmetrical teeth. Over the years,
other standards of beauty have changed significantly; with
different clothes, sizes, and looks drifting in and out of fashion.
However, despite these changes, straight teeth have remained an
intrinsic part of our idea of beauty, specifically in U.S society.
So much so in fact, that an entire field of medicine was created in
its name. Dental braces and have become a pivotal technology in the
United States due to their ability to create the beautiful straight
smiles that we revere so dearly in this culture. What this paper
will attempt to do is explore the evolution of dental braces as a
technology by first examining the progression of materials and
mechanisms used in the practice and then by looking at the social
forces behind the acceptance and adoption of the technology. By
examining the evolution of this technology through both physical
material and socio-cultural lenses, I hope to illuminate the
connections and relationships that exist between braces technology
and the larger cultural trends of our society. Evolution of
Materials:
Figure 1: Pierre Fauchards bandeauWhile a lot of modern
orthodontic development occurred in the United States during the
20th century, the idea and practice of straightening crooked teeth
has been around for centuries. Ancient historical figures such as
Hippocrates, Aristotle, Celcus, and Pliny the Elder have all been
cited discussing the appearance and structure of teeth dating back
all the way to 460 B.C. (Wahl, 2005: Chpt 1). These figures
hypothesized the different reasons and causes behind crooked teeth,
and proposed manual ways to correct them; including the application
of pressure, extraction, and filing teeth down to improve their
alignment (Wahl, 2005: Chpt 1). It wasnt until the 18th century
that the first physical mechanism was invented with the sole
purpose of correcting malocclusion, otherwise known as crooked
teeth. Pierre Fauchard, referred to by many as the father of
orthodontia, invented an instrument know as the bandeau (see fig.
1). The device was made of a band of precious metal, either gold or
silver, and a series of silk ligatures which were tied to
individual teeth (Asbell, 1994). Fauchard used the precious metals
due to their malleability and the ligatures to try and pull
individual teeth towards the preformed metal band. The concept
behind this device was to pull teeth into the desired symmetrical U
shape, while avoiding the extraction of permanent teeth, as was a
common practice for many dentists at the time. (Wahl, 2005: Chpt
1). For years, the bandeau was the norm in the practice what would
later be known as orthodontics. Other orthodontists, including
Etienne Bourdet who was the personal dentist to the King of France,
would expand and adjust his device in order to expand the arch more
efficiently to make room for more teeth (Wahl, 2005: Chpt 1). The
majority of initial development to orthodontic devices and methods
occurred in Europe, however in the beginning of the 19th century,
the United States became a major player in dentistry and
subsequently orthodontics. The devices being used by American
orthodontists were similar to their European counterparts and were
made primarily out of gold and silver, although some did experiment
with different types of wood (Asbell, 1994). Due to their malleable
consistencies, the gold and silver brackets and devices needed
constant adjustments that were often times very uncomfortable for
patients. In 1839 however, Charles Goodyear invented a remarkable
new material called vulcanite that drastically changed the design
and nature of orthodontic devices. The softer material allowed
orthodontists to create new bite plates that were substantially
cheaper and lighter than their metal counterparts (Wahl, 2005: Chpt
1). Professionals also used the new material to make rubber bands,
which are still used today in orthodontia to reduce discomfort and
correct malocclusion. The introduction of vulcanite into braces
technologies allowed for more experimentation and combinatory
technologies that would help advance the technology in many
ways.While the invention of vulcanite was extremely important to
the development of orthodontic technology, dentists still relied
primarily on metal wires and brackets. As mentioned before, the
precious metals were not only highly malleable, but were also
extremely expensive. This issue was addressed in the early 1900s
with the introduction of a new material, stainless steel. While
this metal had been around for years, it was first introduced into
mainstream U.S production in the first two decades of the 1900s and
orthodontists quickly adopted the material. Stainless steel was
cheaper and stronger than gold or silver, while still being
malleable enough to be molded and adjusted to custom fit patients
needs (Stainless Steel, 2013). After its adoption into braces
technology, many dentists started to change the construction of
their devices, because they could now use more metal with every
patient without paying higher costs. As a result, around the same
time that stainless steel made its first appearance in orthodontics
the individual bracket also debuted. Brackets were circular metal
devices that encircled each individual tooth and then connected
those teeth to larger wires (Indian Dental Academy, Feb 2013; fig
2).
Figure 2: Angle's Ribbon Arch: individual bracket useThe bracket
changed the way that orthodontists attempted to correct crooked
teeth, and it was only possible with the introduction of a cheaper
lighter weight metal. However, despite the major advances that
stainless steel created for orthodontic mechanisms, there were some
drawbacks. After orthodontists realized that some of their patients
had allergies to the Nickel found in steel, they needed to find a
new alternative solution and were not willing to revert to silver
or gold. Instead, they were able to offer titanium as an
alternative once it was commercially produced in the mid 1930s
(Titanium, 2013). Titanium was a lighter and equally strong metal
and thus provided consumers with a valid alternative to steel.
However, due to the nature of its production, it came at a higher
cost.Along with the production of new cheaper and lightweight
metals like titanium and steel, the 20th century also marked the
evolution of various other technologies that greatly advanced the
field of orthodontics in different ways. Firstly, the evolution and
widespread use of x-ray technology throughout the entire medical
and dental field provided orthodontists with a new view into the
mouths of their patients. X-rays enabled dentists and orthodontists
to better treat and predict the natural movements of teeth like
they had never been able to before (Wahl, 2005: Chpt 6). As
dentists and orthodontists began to study the root structure of
their patients, they were able to understand the physical causes of
malocclusion and could treat patients accordingly. Secondly, the
20th century also marked big changes in the evolution of adhesive
technologies or cements used in orthodontics. Since the end of the
19th century, dental cements had been used in order to bond the
different brackets to teeth. With the changes to bracket shape and
use in the 1930s and 1940s, existing cements were not providing
orthodontists with strong enough bonds to hold brackets to
individual teeth. However in the 1960s adhesive technologies
evolved dramatically, with the creation of a dental cement that
incorporated the natural make up of tooth enamel into the boding
process (Ewoldsen & et.al. 2001). Orthodontists would have to
prime the teeth with a phosphoric acid and then would later apply a
zinc polyacrylate cement to bond the metal brackets directly to
teeth. Over the years the bonding technology has evolved even
further to incorporate resins and glass ionomers in order to
improve both the strength of the bonds as well as the negative
effects of some original cements. These new adhesive cements were
stronger, clearer, and healthier for patients than previous
versions. They allowed orthodontists to use smaller amounts of
adhesives to receive the same strength of bonds, thus enabling them
to use smaller brackets with no loss in corrective power
(Al-Munajed, 2000) These changes reduced not only the overall
discomfort level of many consumers, but also drastically improved
the overall aesthetic appearance of braces.
Figure 3: Ceramic BracketsDespite the aesthetic improvements
that adhesive technology provided for braces technology, consumers
were still off put by the overall appearance of braces. In
response, there has been a drastic increase within the past twenty
years in new braces technologies. New materials are now being used
primarily to lessen the harsh physical appearance of braces, and in
some cases make them completely invisible. The first move away from
the traditional use of metals in orthodontia came in the 1980s with
the use of ceramic brackets and wires. These tooth colored devices
camouflaged the braces and gave consumers the benefits of an
improved smile without having to live with large amount of metal in
their mouths for years at a time (Archwired, 2005; fig. 3). Even
more recently the development of Invisalign technology has made
correcting crooked teeth even less intrusive. The removable
retainers are made out of a thermoplastic material and are created
using 3-D imaging of an individuals teeth (Invisalign, 2013).
Patients go through a series of different retainers that gradually
shift the alignment of their teeth. Lingual braces, or braces that
go around the inside of teeth as opposed to the outside, have also
been around the orthodontic field for years and have advanced
dramatically in recent years. However, due to the advanced training
that orthodontists need to properly apply the devices, many dont
offer the service to their patients (Wahl, 2005: Chpt 6). While
both these new materials have allowed consumers to have braces
without dealing with the aesthetic consequences, it should be noted
that they are also more expensive options.
The Social Construction of Braces:As mentioned in the
introduction of this paper, braces did not become a part of our
society and culture our of an inherent human need. Although some
young adults might argue that having crooked teeth is the
equivalent of committing social suicide, that way of thinking is a
derivative of the social construction of beauty rather than an
innate biological need. According to Basalla, We cultivate
technology to meet our perceived needs, not a set of universal ones
legislated by nature(Basalla, 1988). Like many technologies, braces
were created and developed due to a socially constructed belief
that a straight smile and nice teeth were defining characteristics
of beauty. Throughout its evolution the physical technology of
braces was directly influenced by the feedback of the consumers
themselves. In the article The social construction of facts and
artifacts: Or how the sociology of technology and sociology of
science might benefit each other written by Trevor Pinch and Wiebe
Bijker, the relationship between society and technology is explored
in detail. Some of the key methods they identify as useful when
examining technology through this lens are the identification of
relevant social groups involved, as well as using a
multidirectional model to track the chronological evolution of a
technology (Pinch & Bijker, 1987).
The Evolution of Mechanisms and SCOT:When the idea of correcting
crooked teeth first started to manifest itself through physical
technologies, there was very little background information or study
that had been put into the biological and physical causes of
malocclusion. As a result, the methods used to straighten teeth
were highly variable. Braces technology remained subjective to each
respective orthodontics up until the mid 20th century when the
technology began to steady with the introduction of new metals and
bonding cement (Ewoldsen & et.al. 2001). It is difficult to
determine exactly which technologies taken from different
mechanisms in orthodontic history have gone into the contemporary
version of dental braces that we are familiar with today. However
by using the SCOT method of multidirectional modeling, we see how
many different technologies that might not appear in a linear model
of the evolution played a part in developing contemporary
braces.What braces technology shows us is that after the
introduction of the bandeau in the 1700s there were very few new
technologies until nearly 100 years later. Orthodontists around
Europe made small adjustments to the existing technology, however
it wasnt until the invention of vulcanite in the mid 1800s that
braces technology did more than target the movement of individual
teeth with the use of ligatures (Wahl, 2005: Chpt 1). After its
invention, different dentists and orthodontists explored different
types of arch expanders and bite plates made out of vulcanite that
both improved the understanding of arch expansion and created the
foundation for many orthodontic technologies still in use today
(Whal, 2005: Chpt 2). Many of these vulcanite-based technologies
worked to improve the knowledge base surrounding orthodontics, but
are not directly linked to the technology used in contemporary
braces. In fact, they most closely resemble retainers that are used
as post-braces treatments by many orthodontists (Whal, 2005: Chpt
2). While the vulcanite devices were not directly involved in
bracket technology that dominates the field today, the ideas they
presented were instrumental in the development of current braces
technology. When orthodontists started experimenting with
vulcanite, they realized the importance of expanding the arch in
order to more easily move teeth. Dr. Edward Angle took this
knowledge and made a series of metal mechanisms known collectively
as the E-arch. This technology was based off of the mechanisms
found in previous V-arch designs, as well as the arch expansion
concepts of the vulcanite plates (Civen, 2004). The E-arch, created
in 1907, was improved upon in 1910 with the Pin an Tube arch. Both
of these were meant to perform the same function as the vulcanite
mechanisms by expanding the palate, however they were not
removable. Many orthodontists in the field had decided that
removable devices were not optimal for producing long-term
straightening effects (Indian Dental Academy, Feb 2013).
Eventually, the Pin and Tube arch would lead to Figure 4: Edgewise
BracketsEdgewise brackets that were the dominant braces technology
until 1956. At that point in time, the Begg bracket was introduced
and would prove to be the basis for most proceeding braces models;
fitting into the more linear model of technological evolution we
are accustomed to exploring. (Indian Dental Academy, Feb 2013; fig.
4). What the SCOT model encourages us to do is examine the
evolution of technology through a more critical lens. It
acknowledges that there is a much richer history behind the
evolution of a technology than we usually see by only looking
retrospectively at the successful versions. While the vulcanite
bite plates resemble modern day retainers much more so than they
resemble metal braces, they still contributed to the evolution of
the technology. By including them in the evolution of braces, we
gain a new insight into not only the development of the technology,
but also the development of the entire orthodontic practice.
Relevant Social Groups:In their article, Pinch and Bijker also
stress the importance of identifying the relevant social groups
within the evolution of any technology. They argue that in order to
understand how and why a technology developed in the way it did, it
is important to look at who exactly had a vested interest in its
advancement (Pinch & Bijker, 1987). As discussed earlier, one
of the strongest driving forces behind the evolution of dental
braces were the standards of beauty that have existed historically,
and have continued to develop within our society. Therefore, when
examining the technological evolution of braces, it is important to
look at who exactly was most active in the perpetuation and
creation of the standards that emphasized having straight,
symmetrical teeth. Through my research, I have determined that the
two main actors involved in the evolution of braces in the broadest
sense, were patients and orthodontists. However, within the patient
group, there are various different subcategories that have effected
and supported the evolution of braces in different ways.
Specifically, the relevant groups within patients are women,
individuals with high socio-economic standing, and most recently
adults. Beginning by examining the group of women, it is clear by
examining historical trends braces use that women have always been
more interested in using braces to straighten their teeth. Even
before the technology began to stabilize in the 1970s and became
more aesthetically pleasing, women were willing to undergo many
different kinds of orthodontic treatments to straighten their
teeth. Due to the increased pressure by society to conform to
standards of beauty, women have gone to great lengths throughout
history to change their natural appearance even if that meant
undergoing painful procedures or wearing heavy metal appliances in
their mouths (Jensen, 2013). Even in ancient Etruscan cultures,
only female remains were found with the remnants of some sort of
corrective dental device (Wahl, 2005: Chpt 1). A more recent study
done in 2009 amongst a group of children showed that girls were
generally more critical of their own smiles and thought they needed
to get braces, even if they did not have a definite treatment need
(Christopherson & et.al, 2009). What this case demonstrates is
the constructed need to have straight teeth and consequential
social pressure to conform to those social constructions being felt
by young women today. While men have also expressed an interest in
braces, women have historically and currently do experience a
larger pressure to have straight teeth and have therefore always
been important actors in the evolution of braces technology.In more
recent history, the incorporation of new materials into braces
technology has turned adults into a new relevant social group.
Before the introduction of ceramic brackets and Invisalign
technology, braces did not attract many adults due to the
association of braces with adolescence (Rosvall & et.al, 2009).
Forty-year old executives with metal braces were not likely to be
taken very seriously. Therefore, when ceramic brackets and
Invisalign type technologies began to develop, adults were quick to
involve themselves in the process. Merely by typing Invisalgn or
ceramic braces into a search engine, one can see that the many of
the companies and organizations that are found advertise to adult
consumer groups. As the materials have changed and the technology
has evolved, adults now have a way to get straight teeth without
having to go through the humiliating process of metal braces. While
the social groups vary based on gender and age, there is one
characteristic that has remained relatively constant throughout the
entire evolution of braces and that is socioeconomic status. Since
their inception when they were made out of pure gold and silver,
braces have always been an expensive technology. It does not come
as a surprise then, that the majority of patients come from
relatively affluent backgrounds. Original patients who were the
test subjects of the worlds first orthodontists, included kings and
princes in France who could afford to pay their dentists to create
devices out of precious metals (Wahl, 2005: Chpt 1). Today, the
class divide still exists in orthodontics, although now you dont
have to be a King or Queen to receive treatment. This being said,
braces still remain a technology only available to those with
comprehensive dental plans and large savings accounts. Traditional
metal braces run between $3,500 and $6,000 dollars, which, for
families and individuals belonging to lower socio-economic
groupings are far too expensive (Proctor and Gamble, 2013). While
some dental plans do cover braces at least partially and some
orthodontists offer payment plans for patients, the price of braces
generally limits the patient base to relatively wealthy sectors of
society. In fact, one of the reasons that the new aesthetically
pleasing braces technologies (which cost between $5,000 and $8,000
dollars) have been allowed to develop and succeed is because the
social group most directly involved in their production typically
have the financial means to afford them. In effect, braces have
always been a technology paid for and influenced by the most elite
groups of society.Lastly, as I will expand upon in the near future,
orthodontists themselves are another relevant social group in the
evolution of braces. When the first orthodontists began to
distinguish themselves in the dental community, they were more like
specialized dentists than anything else. Due to the fact that no
official discipline of orthodontics had yet been established, the
original orthodontists had no foundation to base their work upon
therefore they had a vested interest in creating completely new
technology that could serve as an example for generations to come.
Once the specialty and technology had been established,
orthodontists had much more economically fueled interest in the
evolution of the technology. When orthodontists decided that they
were not interested in going through extra training to use lingual
braces, the technology faded to the background of new braces
technologies. Orthodontists created an entirely new field of
medicine for themselves and were driven by both professional and
financial goals.The Professionalization of Orthodontics:Another
very important factor in the evolution of dental braces was the
professionalization of orthodontics and the emergence of accredited
university and professional programs. In 1910, Dr. Edward Angle
created the first university program for orthodontics in the United
States known as the Angle School. The program was the first of its
kind to focus specifically on the practice of orthodontics, rather
than dentistry. Dr. Angle himself was one of the most influential
orthodontists in the United States, and the creation of his
university program enabled many of the discoveries and mechanisms
of the 20th century. After the Angle school opened, other
post-graduate programs began to emerge around the country. Student
and graduates of these programs went on to develop their own
methods and devices and even went on to publish some of the first
national journals devoted to orthodontics (Wahl, 2005: Chapt 3).
Before this point, orthodontics had merely been a subset of
dentistry that a few dedicated individuals had devoted their lives
to. The progression of orthodontic technology was slow and messy
because there was no uniform curriculum or knowledge base for
individuals to base their methods off of. With the introduction of
schools of orthodontics, industrial knowledge and methods were able
to flow freely and as a result the industry experienced a growth in
industry specific knowledge and an increase in new mechanisms.
(Wahl, 2005: Chpt 3; Lapsley, 2012).
Figure 5: One current Ortho AssociationAlong with the
introduction of new university programs, the early 1900s also
marked the first instances of nation wide orthodontic associations
(Wahl, 2005: Chpt 3). These associations allowed recent graduates
of orthodontic programs, as well as already established figures in
the orthodontic field to organize and form networks amongst each
other. One result of these new networks was a newfound sense of
competition between individual orthodontists and schools of though.
The majority of conflicts and debates existed between Dr. Angle and
his students, and those who attended other institutions that didnt
belong to the same school of thought. Like most competition within
industries, the competition between Angle and others in the field
did spark some controversy, but it also inspired new technologies
and methods, which would go on to advance the fields as a whole
(Wahl, 2005: Chpt 6; Kenney, 2013). Without the creation of
university programs and orthodontic associates, the discussions and
innovations formed in the wake of newly created relationships and
competition would have gone unexplored. As a profession, many
individuals saw a lot of potential in orthodontics for a variety of
reasons. Firstly, as discussed above, the demand for straight teeth
has always been, and promises to remain, relatively high especially
in U.S society. Orthodontists rarely have to worry that their
client base will suddenly stop desiring straight teeth; therefore
their jobs are almost inherently secure. Another appeal of the
profession is that orthodontists tend to make decent livings due to
the relative cost of their product. It should come as no surprise
that with a product literally made of gold; orthodontists were not
operating within a small budget when it came to developing their
technology. Even today, orthodontists are one of the top earning
careers in the entire United States. In 2012, the BLS published
findings that placed orthodontists at number six on the list of top
earning positions, with those in the field earning an average of
$186,000 a year (Locsin, 2012). With high job security and high
salaries, it is not surprising that orthodontia is a competitive
and highly sought after profession. Conclusion:To the dismay of
millions of young adults who have lived through the experience,
braces have become an important technology in U.S society. The
century old desire for straight teeth has resulted in countless
mechanisms and technologies made out of various different
materials. As those materials and mechanisms evolved, so too did
the general understanding of the underlying structure of teeth.
Even in the past century, we have seen the effectiveness of braces
increase exponentially. For a price, individuals are able to enter
an orthodontists office one day with crooked teeth, and leave a few
months or a couple years later with perfectly straight teeth.
Previously, this same transformation was only possible with
multiple years of therapy and gave no guarantee of success. Braces
technology has found new ways to incorporate fresh materials and to
address the needs of patients in successful and important ways. As
a result, braces have become an important part of U.S culture and
have expanded their influence into new social groups and
institutions. Unless standards of beauty in this country change
drastically in the near future, braces will remain to be an
important technology and will continue to evolve and expand as new
technologies become available. Currently, work is being done with
3-D modeling and genetic testing in order to find new ways to map
and more effectively treat malocclusions. The incorporation of
these new technologies, as well as the further development of
existing methods will undoubtedly lead to more discrete and
effective treatments for crooked teeth. Not to mention a
significant decrease in the number of embarrassing school photos
that entire generations of young children will have to hide from
their friends.
Works CitedAl-Munajed, K. (2000). The use of a cyanoacrylate
adhesive for bonding orthodontic brackets: an ex-vivo study.Journal
of Orthodontics,27(3), 255-260.
Archwired. (2005).Should I get ceramic or metal?. Retrieved from
http://www.archwired.com/ceramic_vs_metal_braces.htm
Asbell, M. (1994). A brief history of orthodontics. American
Journal of Orthodontics and Dentofacial Orthopedics,98(3),
Basalla, George. 1988. The Evolution of Technology (New York:
Cambridge University Press) pp 1-63.
Christopherson, M. & et.al. (2009). Objective, subjective,
and self-assessment of preadolescent orthodontic treatment need--a
function of age, gender, and ethnic/racial background?.Journal of
Public Dental Health,69(1), 9-17.
Civen, O. (1940).An historical review of the progress of
orthodontics from 1840 to 1940.
Ewoldsen, N., & Demke, R. (2001). A review of orthodontic
cements and adhesives.American Journal of Orthodontics and
Dentofacial Orthopedics,120(1), 45-48.
Indian Dental Academy. (13 Feb, 2013). Evolution of Orthodontic
Brackets. Indian Dental Academy. PowerPoint.
http://www.slideshare.net/indiandentalacademy/orthodontic-brackets-part-1-orthodontic-courses-in-india-indian-dental-academy
Indian Dental Academy. (4 Oct, 2013). Advances in
Orthodontics/Orthodontic Course Trainings. Indian Dental Academy.
PowerPoint.
http://www.slideshare.net/indiandentalacademy/advances-in-orthodontics-orthodontic-courses-training-by-indian-dental-academy
Invisalign Inc. (n/d.).Invisalign-frequently asked questions.
Retrieved from http://www.hvortho.com/docs/invisalign-faqs.pdf
Jensen, K. (2013).The weirdest beauty rituals throughout time.
Retrieved from
http://mom.me/home/7471-weirdest-beauty-rituals-throughout-history/
Lapsley, J., & Summer, D. (2012). "We are both hosts: napa
valley, u.c. davis and the search for quality.
Locsin, A. (2012).How much money do orthodontists make?.
Retrieved from
http://work.chron.com/much-money-orthodontists-make-21906.html
Pinch, Trevor and Weibe Bijker. 1987. The Social Construction of
Facts and Artifacts, In Bijker, T. Huges, and T. Pinch (eds) The
Social Construction of Technological Systems. (Cambridge, MA: MIT
Press) pp. 17-47.
Proctor & Gamble. (2013).How much to braces cost. Retrieved
from http://www.oralb.com/embraceit/how-much-do-braces-cost
Rosvall, M., & et.al. (2009). Attractiveness, acceptability,
and value of orthodontic appliances.American Journal of
Orthodontics and Dentofacial Orthopedics,135(3),
Stainless steel. In (2013).Encyclopedia Britannica. Retrieved
from
http://www.britannica.com/EBchecked/topic/562558/stainless-steel
Titanium. In (2013). Encyclopedia Britannica. Retrieved from
http://www.britannica.com/EBchecked/topic/597174/titanium-processing
Wahl, N. (2005). Orthodontics in 3 millennia. Chapter 1:
Antiquity to the mid-19th century.American Journal of Orthodontics
and Dentofacial Orthopedics,127(2),
Wahl, N. (2005). Orthodontics in 3 millennia. Chapter 2:
Entering the Modern Era.American Journal of Orthodontics and
Dentofacial Orthopedics,127(4),
Wahl, N. (2005). Orthodontics in 3 millennia. Chapter 3: The
Professionalization of Orthodontics.American Journal of
Orthodontics and Dentofacial Orthopedics,127(4),
Wahl, N. (2005). Orthodontics in 3 millennia. Chapter 6: More
early 20th-century appliances and the extraction
controversy.American Journal of Orthodontics and Dentofacial
Orthopedics, 127(6),