Microsoft Word - Cetnar 2016.doc


	
  

Vol	
  4,	
  No	
  1	
  (2016)	
  
ISSN	
  2167-­‐8677	
  (online)	
  

DOI	
  10.5195/d3000.2016.52	
  	
  

	
  

	
  

	
  

http://dentistry3000.pitt.edu	
  

	
   New	
  articles	
  in	
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  journal	
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  licensed	
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  Creative	
  Commons	
  Attribution	
  4.0	
  United	
  States	
  License.	
  

	
  
This	
  journal	
  is	
  published	
  by	
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  University	
  Library	
  System,	
  University	
  of	
  Pittsburgh	
  as	
  part	
  of	
  its	
  D-­‐Scribe	
  Digital	
  Publishing	
  Program	
  and	
  is	
  cosponored	
  
by	
  the	
  University	
  of	
  Pittsburgh	
  Press.	
  

	
  

Observing	
  Anterior	
  Crowding	
  In	
  a	
  Population	
  Living	
  a	
  Century	
  Ago	
  
Christopher	
  Cetnar1	
  
	
  
1	
  University	
  of	
  Pittsburgh	
  School	
  of	
  Dental	
  Medicine,	
  Pittsburgh	
  PA,	
  USA

Abstract	
  

Purpose:	
  To	
  observe	
  the	
  frequency	
  of	
  mandibular	
  anterior	
  crowding	
  in	
  a	
  population	
  who	
  
lived	
  during	
   the	
  nineteenth	
  century	
  and	
  compare	
   the	
   rate	
  of	
  occurrence	
   in	
   the	
  current	
  
population,	
  which	
   is	
   claimed	
   to	
  be	
   two-­‐thirds	
   of	
   adults	
   experiencing	
   crowding	
  by	
   early	
  
adulthood.	
  Materials	
  and	
  Methods:	
  The	
  School	
  of	
  Dental	
  Medicine	
  at	
   the	
  University	
  of	
  
Pittsburgh	
   possesses	
   a	
   collection	
   of	
   skulls	
   of	
   individual’s	
   likely	
   living	
   in	
   the	
   northeast	
  
United	
  States	
  during	
  the	
  late	
  19th	
  century	
  and	
  early	
  20th	
  century.	
  Of	
  this	
  skull	
  collection,	
  
29	
  skulls	
  were	
  evaluated	
  for	
  the	
  presence	
  of	
  mandibular	
  anterior	
  crowding.	
  Results:	
  55%	
  
of	
   the	
   evaluated	
   mandibular	
   anterior	
   arches	
   were	
   positive	
   for	
   mandibular	
   anterior	
  
crowding.	
  57%	
  of	
  the	
  male	
  specimens	
  were	
  positive	
  for	
  anterior	
  crowding,	
  while	
  50%	
  of	
  
the	
  females	
  were	
  recorded	
  to	
  have	
  anterior	
  crowding.	
  These	
  frequencies	
  are	
  lower	
  than	
  
the	
  one	
  suggested	
  for	
  the	
  current	
  live	
  population	
  in	
  the	
  United	
  States.	
  Conclusion:	
  From	
  
this	
  sample	
  of	
  the	
  population	
  living	
  a	
  century	
  ago,	
  there	
  was	
  a	
  lower	
  prevalence	
  of	
  ante-­‐
rior	
  crowding	
  (55%)	
  than	
  the	
  research	
  suggested	
  two-­‐thirds	
  of	
  adults.	
  

	
  

Citation:	
  Cetnar,	
  C.	
  (2016)	
  Observing	
  Anterior	
  
Crowding	
  In	
  a	
  Population	
  Living	
  a	
  Century	
  Ago.	
  
Dentistry	
  3000.	
  1:a001	
  
doi:10.5195/d3000.2016.52	
  
Received:	
  May	
  31,	
  2016	
  
Accepted:	
  	
  June	
  13,	
  2016	
  
Published:	
  	
  September	
  28,	
  2016	
  
Copyright:	
  ©2016	
  Cetnar,	
  C.	
  This	
   is	
  an	
  open	
  ac-­‐
cess	
  article	
   licensed	
  under	
  a	
  Creative	
  Commons	
  
Attribution	
  Work	
  4.0	
  United	
  States	
  License.	
  
Email:	
  cwc23@pitt.edu

	
  

Introduction	
  

Orthodontic	
  treatment	
  has	
  
become	
  very	
  common	
  in	
  the	
  
modern	
  model	
  of	
  dental	
  treat-­‐
ment.	
  It	
  has	
  been	
  recorded	
  that	
  
80%	
  of	
  U.S.	
  teenagers	
  have	
  com-­‐
pleted	
  or	
  are	
  currently	
  undergoing	
  
orthodontic	
  treatment	
  according	
  
to	
  the	
  American	
  Association	
  of	
  
Orthodontists	
  (AAO;	
  
https://www.aaoinfo.org/).	
  It	
  can	
  
be	
  contemplated	
  that	
  in	
  the	
  near	
  
future	
  orthodontic	
  treatment	
  may	
  
eventually	
  become	
  the	
  standard	
  of	
  
care,	
  if	
  it	
  has	
  not	
  already.	
  

One	
  key	
  to	
  understanding	
  
orthodontic	
  treatment	
  is	
  the	
  idea	
  
that	
  the	
  oral	
  cavity	
  is	
  dynamic,	
  
consisting	
  of	
  many	
  interacting	
  
components	
  including	
  pressures	
  
from	
  soft	
  tissue,	
  musculature,	
  

function,	
  and	
  normal	
  growth.	
  This	
  
dynamic	
  environment	
  is	
  under-­‐
stood	
  by	
  orthodontics	
  and	
  is	
  com-­‐
bated	
  with	
  the	
  use	
  of	
  removable	
  
or	
  permanent	
  retainers	
  after	
  
treatment	
  to	
  prevent	
  the	
  altera-­‐
tion	
  of	
  the	
  established	
  occlusion	
  
(orthodontic	
  regression).	
  	
  

Mandibular	
  incisor	
  crowd-­‐
ing	
  is	
  a	
  phenomenon	
  that	
  is	
  ob-­‐
served	
  in	
  both	
  patients	
  that	
  have	
  
received	
  orthodontic	
  treatment	
  
and	
  those	
  who	
  have	
  not.	
  As	
  the	
  
aging	
  process	
  occurs,	
  the	
  smile	
  
line	
  tends	
  to	
  shift	
  exposing	
  more	
  
mandibular	
  teeth	
  when	
  a	
  patient	
  
smiles	
  or	
  opens	
  their	
  mouth	
  in	
  
normal	
  conversation.	
  Patients	
  who	
  
had	
  previous	
  orthodontic	
  treat-­‐
ment	
  notice	
  that	
  their	
  once	
  
straight	
  teeth	
  become	
  “crooked”	
  
or	
  “crowded”	
  and	
  point	
  towards	
  

their	
  mandibular	
  incisors.	
  Re-­‐
search	
  suggests	
  that,	
  without	
  or-­‐
thodontic	
  treatment,	
  approxi-­‐
mately	
  2/3	
  of	
  adolescents	
  with	
  
good	
  alignment	
  and	
  “normal”	
  oc-­‐
clusions	
  will	
  develop	
  incisor	
  ir-­‐
regularity	
  by	
  early	
  adulthood	
  [1].	
  

	
   The	
  School	
  of	
  Dental	
  Medi-­‐
cine	
  at	
  the	
  University	
  of	
  Pittsburgh	
  
possesses	
  a	
  collection	
  of	
  skulls	
  
that	
  is	
  made	
  up	
  of	
  individuals	
  liv-­‐
ing	
  in	
  the	
  Northeastern	
  United	
  
States	
  during	
  the	
  late	
  19th	
  and	
  
early	
  20th	
  century	
  [2].	
  This	
  popu-­‐
lation	
  living	
  a	
  century	
  ago	
  would	
  
not	
  have	
  undergone	
  modern	
  day	
  
orthodontic	
  treatment	
  and	
  from	
  
this,	
  anterior	
  crowding	
  can	
  be	
  ob-­‐
served	
  whether	
  or	
  not	
  two-­‐thirds	
  
of	
  adolescents	
  have	
  crowding	
  in	
  
their	
  mandibular	
  anterior	
  teeth.	
  
This	
  information	
  would	
  yield	
  use-­‐



	
  	
  Observing	
  Anterior	
  Crowding	
  In	
  a	
  Population	
  Living	
  a	
  Century	
  Ago	
  

Vol	
  4,	
  No	
  1	
  (2016)	
  	
  	
  	
  DOI	
  10.5195/d3000.2016.52	
  

	
  http://dentistry3000.pitt.edu	
  
2	
  

ful	
  data	
  in	
  understanding	
  the	
  
complex	
  process	
  of	
  anterior	
  
crowding	
  and	
  the	
  prevalence	
  in	
  a	
  
population	
  that	
  was	
  not	
  exposed	
  
to	
  modern	
  dentistry	
  and	
  ortho-­‐
dontic	
  practices.	
  

Methods	
  

At	
  the	
  University	
  of	
  Pitts-­‐
burgh	
  School	
  of	
  Dental	
  Medicine	
  
there	
  is	
  a	
  collection	
  of	
  skulls.	
  Most	
  
of	
  them	
  were	
  acquired	
  from	
  a	
  
seller	
  in	
  New	
  York	
  City	
  around	
  the	
  
1930’s	
  indicating	
  that	
  these	
  indi-­‐
viduals	
  lived	
  in	
  the	
  east	
  coast	
  of	
  
the	
  United	
  States	
  [2].	
  The	
  skulls	
  
have	
  previous	
  tagged	
  displaying	
  
gender,	
  estimated	
  age	
  (>40	
  years,	
  
<40	
  years;	
  unless	
  a	
  known	
  age	
  was	
  
indicated),	
  as	
  well	
  as	
  ethnicity.	
  	
  

In	
  evaluation	
  of	
  anterior	
  
crowding,	
  a	
  set	
  of	
  criteria	
  was	
  es-­‐
tablished	
  to	
  determine	
  if	
  the	
  skull	
  
was	
  eligible.	
  The	
  first	
  condition	
  
was	
  that	
  the	
  skull	
  had	
  to	
  have	
  full	
  
adult	
  dentition,	
  which	
  excluded	
  
the	
  six	
  pediatric	
  skulls	
  found	
  in	
  the	
  
museum.	
  The	
  second	
  condition	
  
was	
  that	
  the	
  specimen	
  had	
  to	
  
have	
  present	
  all	
  six	
  of	
  the	
  man-­‐
dibular	
  anterior	
  teeth.	
  The	
  last	
  cri-­‐
teria	
  was	
  evaluating	
  the	
  condition	
  

of	
  the	
  crowns	
  on	
  the	
  anterior	
  
teeth	
  which	
  eliminated	
  specimens	
  
that	
  had	
  more	
  than	
  one	
  full	
  crown	
  
missing	
  or	
  that	
  had	
  crowns	
  that	
  
were	
  unable	
  to	
  be	
  evaluated	
  for	
  
crowding	
  (missing	
  contacts,	
  frac-­‐
tured	
  crowns	
  etc).	
  	
  After	
  the	
  selec-­‐
tion	
  process	
  was	
  completed	
  there	
  
were	
  29	
  qualified	
  mandibular	
  
arches	
  evaluated,	
  23	
  males	
  and	
  six	
  

females.	
  

Since	
  the	
  intent	
  is	
  not	
  to	
  
measure	
  the	
  severity	
  of	
  crowding,	
  
a	
  different	
  method	
  of	
  evaluating	
  
crowding	
  was	
  applied	
  in	
  determin-­‐
ing	
  whether	
  or	
  not	
  the	
  subject	
  has	
  
crowding	
  present.	
  Crowding	
  was	
  
evaluated	
  by	
  proximal	
  tooth	
  con-­‐
tact-­‐point	
  displacement,	
  which	
  

was	
  observed	
  by	
  visualizing	
  irregu-­‐
larity,	
  flaring,	
  or	
  protrusion	
  of	
  the	
  
mandibular	
  incisors	
  [4].	
  	
  For	
  an	
  
arch	
  to	
  qualified	
  as	
  a	
  	
  “yes	
  or	
  posi-­‐
tive”	
  response	
  to	
  crowding,	
  two	
  or	
  
more	
  teeth	
  in	
  the	
  anterior	
  arch	
  
must	
  have	
  improper	
  bilateral	
  
proximal	
  contact	
  or	
  must	
  display	
  
excessive	
  flaring,	
  retrusion	
  or	
  pro-­‐
trusion	
  due	
  to	
  insufficient	
  interca-­‐
nine	
  distance.	
  For	
  example,	
  Figure	
  
2a	
  would	
  have	
  recorded	
  as	
  posi-­‐
tive	
  for	
  anterior	
  crowding,	
  while	
  
Figure	
  2b	
  would	
  have	
  been	
  nega-­‐
tive	
  for	
  anterior	
  crowding	
  since	
  
there	
  is	
  ideal	
  proximal	
  tooth	
  con-­‐
tact	
  and	
  no	
  excessive	
  malposition	
  
of	
  the	
  anterior	
  teeth	
  due	
  to	
  lack	
  of	
  
arch	
  space.	
  

There	
  are	
  multiple	
  meth-­‐
ods	
  to	
  determining	
  whether	
  ante-­‐
rior	
  crowding	
  exists	
  besides	
  the	
  
mere	
  clinical	
  presentation	
  of	
  misa-­‐

ligned	
  teeth.	
  One	
  method	
  to	
  de-­‐
termine	
  the	
  severity	
  of	
  anterior	
  
crowding	
  to	
  determine	
  appropri-­‐
ate	
  treatment	
  is	
  the	
  widths	
  of	
  all	
  
the	
  teeth	
  anterior	
  to	
  the	
  molars	
  
are	
  measured	
  and	
  subtracted	
  from	
  
the	
  sum	
  of	
  two	
  measurements	
  
(mesial	
  of	
  the	
  lower	
  incisor	
  to	
  the	
  
distal	
  of	
  the	
  lower	
  canine,	
  plus	
  dis-­‐
tal	
  of	
  lower	
  canine	
  to	
  the	
  mesial	
  of	
  



	
  	
  Observing	
  Anterior	
  Crowding	
  In	
  a	
  Population	
  Living	
  a	
  Century	
  Ago	
  

Vol	
  4,	
  No	
  1	
  (2016)	
  	
  	
  	
  DOI	
  10.5195/d3000.2016.52	
  

	
  http://dentistry3000.pitt.edu	
  
3	
  

the	
  first	
  molar)	
  to	
  give	
  the	
  degree	
  
of	
  crowding	
  [3].	
  This	
  method	
  is	
  
described	
  in	
  Figure	
  1.	
  

Results	
  

From	
  Table	
  1,	
  it	
  can	
  be	
  ob-­‐
served	
  that	
  out	
  of	
  the	
  29	
  subjects	
  
that	
  were	
  eligible	
  for	
  evaluation,	
  
16	
  (55%)	
  presented	
  with	
  anterior	
  
crowding,	
  while	
  13	
  of	
  the	
  speci-­‐
mens	
  had	
  normal	
  spacing	
  and	
  
proximal	
  contacts	
  between	
  all	
  six	
  
of	
  the	
  mandibular	
  anterior	
  teeth.	
  	
  

	
  

Table	
  2	
  shows	
  a	
  compari-­‐
son	
  between	
  male	
  and	
  female	
  
museum	
  specimens.	
  These	
  data	
  
show	
  that	
  males	
  were	
  at	
  a	
  slightly	
  
higher	
  rate	
  of	
  56.5%	
  occurrence	
  of	
  
anterior	
  crowding	
  in	
  comparison	
  
with	
  50%	
  of	
  the	
  female	
  subjects	
  
being	
  positive	
  for	
  anterior	
  crowd-­‐
ing.	
  

Table	
  3	
  shows	
  a	
  compari-­‐
son	
  between	
  age	
  groups	
  and	
  sexes	
  

that	
  were	
  recorded	
  in	
  the	
  muse-­‐
um	
  records.	
  These	
  data	
  show	
  that	
  
males	
  had	
  nearly	
  the	
  same	
  preva-­‐
lence	
  for	
  anterior	
  crowding	
  in	
  
both	
  age	
  groups,	
  57%	
  for	
  males	
  
below	
  the	
  age	
  of	
  40	
  and	
  56%	
  for	
  
males	
  above	
  the	
  age	
  of	
  40.	
  While	
  
the	
  females	
  below	
  the	
  age	
  of	
  40	
  
only	
  showed	
  25%	
  positive	
  for	
  an-­‐
terior	
  crowding	
  and	
  both	
  of	
  the	
  
two	
  specimens	
  above	
  the	
  age	
  of	
  
40	
  being	
  positive	
  for	
  anterior	
  
crowding.	
  

Discussion	
  

The	
  
physiology	
  be-­‐
hind	
  anterior	
  
crowding	
  is	
  
understood	
  as	
  
combination	
  
between	
  me-­‐
sial	
  movement	
  

of	
  posterior	
  teeth	
  and	
  lingual	
  
movement	
  of	
  anterior	
  teeth.	
  Es-­‐
sentially,	
  both	
  of	
  these	
  processes	
  
shorten	
  the	
  arch	
  length,	
  which	
  
leads	
  to	
  the	
  crowding	
  process.	
  The	
  
mesial	
  movement	
  of	
  posterior	
  
teeth	
  theory	
  has	
  been	
  more	
  or	
  
less	
  discounted	
  as	
  the	
  source	
  of	
  
crowding	
  and	
  has	
  been	
  used	
  as	
  
justification	
  for	
  surgical	
  removal	
  of	
  

third	
  mo-­‐
lars.	
  Studies	
  
have	
  shown	
  
that	
  there	
  is	
  
no	
  clinically	
  
reduced	
  
level	
  of	
  
crowding	
  
due	
  to	
  third	
  
molar	
  ex-­‐
traction	
  as	
  

well	
  as	
  crowding	
  affecting	
  people	
  
with	
  congenitally	
  missing	
  third	
  

molars	
  the	
  same	
  as	
  those	
  who	
  
have	
  retained	
  molars	
  [5]..	
  Anterior	
  
lingual	
  movement	
  is	
  discussed	
  
through	
  the	
  equilibrium	
  theory	
  of	
  
tooth	
  position,	
  with	
  evidence	
  from	
  
the	
  differential	
  mandibular	
  growth	
  
theory.	
  	
  Anterior	
  crowding	
  is	
  most	
  
definitely	
  a	
  multifactorial	
  process	
  
and	
  evidence	
  seems	
  to	
  lean	
  to-­‐
wards	
  a	
  combination	
  of	
  the	
  equi-­‐
librium	
  theory	
  and	
  relapse	
  from	
  
orthodontic	
  treatment.	
  	
  

There	
  are	
  a	
  number	
  of	
  
theories	
  attempting	
  to	
  explain	
  
mesial	
  acting	
  force;	
  pressure	
  from	
  
erupting	
  third	
  molars,	
  inherent	
  
mesial	
  migration	
  or	
  drifting,	
  matu-­‐
ration	
  and	
  contraction	
  of	
  perio-­‐
dontal	
  soft	
  tissue	
  and	
  fibers,	
  oc-­‐
clusal	
  forces	
  on	
  anterior	
  teeth,	
  
and	
  loss	
  of	
  arch	
  length	
  due	
  to	
  inci-­‐
sor	
  overbite.	
  It	
  is	
  illogical	
  to	
  as-­‐
sume	
  that	
  there	
  is	
  a	
  single	
  cause	
  
of	
  late	
  mandibular	
  anterior	
  crowd-­‐
ing	
  and	
  more	
  realistically	
  under-­‐
stood	
  as	
  a	
  complex	
  and	
  multifac-­‐
torial	
  process.	
  Like	
  other	
  multifac-­‐
torial	
  processes,	
  there	
  is	
  always	
  an	
  
interaction	
  between	
  genetics	
  and	
  
the	
  environment.	
  Most	
  of	
  the	
  re-­‐
searched	
  processes	
  tend	
  to	
  be	
  
considered	
  environmental	
  instead	
  
of	
  making	
  links	
  to	
  genetic	
  suscep-­‐
tibility.	
  From	
  a	
  genetic	
  approach,	
  
there	
  may	
  be	
  certain	
  susceptibili-­‐
ties	
  that	
  can	
  be	
  observed	
  to	
  help	
  
predict	
  the	
  severity	
  of	
  future	
  ante-­‐
rior	
  crowding	
  besides	
  observing	
  
familial	
  trends.	
  This	
  could	
  lead	
  to	
  
creating	
  personalized	
  treatment	
  
plants	
  to	
  prevent	
  relapse	
  in	
  pa-­‐
tients	
  who	
  have	
  undergone	
  ortho-­‐
dontic	
  treatment	
  and	
  are	
  interest-­‐
ed	
  in	
  persevering	
  their	
  inter-­‐arch	
  
length.	
  	
  

Table 1. Prevalence of anterior crowding found in the 
observed population 

Specimens positive for anterior crowding 16 

Specimens negative for anterior crowding 13 

Percent of specimens positive for anterior crowding 55% 

Table 2. Comparison of crowding by sex. 

 

Specimens 
positive for an-
terior crowding 

Specimens 
negative for 

anterior crowd-
ing 

Percent of spec-
imens positive 

for anterior 
crowding 

Males 13 10 56.5% 

Female 3 3 50% 



	
  	
  Observing	
  Anterior	
  Crowding	
  In	
  a	
  Population	
  Living	
  a	
  Century	
  Ago	
  

Vol	
  4,	
  No	
  1	
  (2016)	
  	
  	
  	
  DOI	
  10.5195/d3000.2016.52	
  

	
  http://dentistry3000.pitt.edu	
  
4	
  

The	
  common	
  understand-­‐
ing	
  with	
  mandibular	
  incisor	
  crowd-­‐
ing	
  is	
  that	
  without	
  orthodontic	
  
treatment,	
  approximately	
  two-­‐
thirds	
  of	
  adolescents	
  will	
  develop	
  
incisor	
  irregularity	
  by	
  early	
  adult-­‐
hood.	
  This	
  hypothesis	
  might	
  be	
  
observable	
  in	
  modern	
  day	
  adults	
  
in	
  which	
  have	
  had	
  a	
  mosaic	
  of	
  
modern	
  orthodontic,	
  surgical,	
  and	
  
restorative	
  treatment,	
  all	
  of	
  which	
  
may	
  affect	
  late	
  mandibular	
  incisor	
  
movement	
  ultimately	
  resulting	
  in	
  
crowding.	
  Observing	
  a	
  population	
  
almost	
  a	
  century	
  apart	
  in	
  which	
  
these	
  more	
  modern	
  approaches	
  to	
  
occlusion	
  and	
  comprehensive	
  or-­‐
thodontic	
  treatment	
  were	
  not	
  
available	
  could	
  contest	
  this	
  dog-­‐
ma.	
  With	
  the	
  understanding	
  that	
  
orthodontics	
  is	
  in	
  place	
  to	
  correct	
  
original	
  malocclusion	
  and	
  does	
  not	
  
play	
  a	
  role	
  in	
  later	
  life	
  develop-­‐
mental	
  processes	
  that	
  lead	
  to	
  
crowding,	
  it	
  is	
  very	
  interesting	
  to	
  
observe	
  see	
  if	
  we	
  are	
  better	
  off	
  
now	
  that	
  we	
  were	
  a	
  century	
  ago	
  in	
  

relation	
  to	
  ante-­‐
rior	
  crowding	
  in	
  
adults.	
  

From	
  the	
  
data	
  present	
  in	
  
Table	
  1,	
  it	
  was	
  
observed	
  that	
  in	
  
the	
  population	
  
living	
  on	
  the	
  
eastern	
  coast	
  of	
  
the	
  United	
  
States	
  nearly	
  a	
  
century	
  ago	
  
(1930s)	
  repre-­‐
sented	
  in	
  the	
  
museum,	
  there	
  
was	
  observable	
  
anterior	
  crowd-­‐

ing	
  in	
  55%	
  of	
  the	
  subjects.	
  This	
  is	
  
an	
  interesting	
  number	
  because	
  it	
  
is	
  actually	
  lower	
  than	
  the	
  expected	
  
two-­‐thirds	
  (66%)	
  that	
  research	
  
suggests.	
  	
  	
  	
  

	
   The	
  data	
  presented	
  
in	
  Table	
  3	
  compares	
  age	
  and	
  gen-­‐
der	
  and	
  shows	
  that	
  the	
  male	
  spec-­‐
imens	
  that	
  were	
  eligible	
  for	
  analy-­‐
sis	
  showed	
  a	
  relatively	
  consistent	
  
percentage	
  of	
  anterior	
  crowding,	
  
but	
  the	
  data	
  collected	
  from	
  the	
  
few	
  female	
  specimens	
  told	
  a	
  dif-­‐
ferent	
  story.	
  Only	
  25%	
  of	
  the	
  fe-­‐
males	
  under	
  the	
  age	
  of	
  40	
  showed	
  
anterior	
  crowding	
  while	
  both	
  of	
  
the	
  specimens	
  aged	
  above	
  40	
  
were	
  positive	
  for	
  anterior	
  crowd-­‐
ing.	
  Though	
  the	
  sample	
  size	
  was	
  
very	
  small	
  for	
  the	
  females,	
  it	
  is	
  
consistent	
  with	
  the	
  modern	
  ob-­‐
servation	
  in	
  which	
  correlates	
  inci-­‐
sor	
  crowding	
  and	
  thickness	
  of	
  the	
  
mandibular	
  symphysis,	
  cancellous	
  
bone	
  thickness	
  [6].	
  

One	
  drawback	
  of	
  this	
  ob-­‐
servation	
  is	
  the	
  lack	
  of	
  sample	
  
size;	
  of	
  the	
  100	
  specimens	
  found	
  
in	
  the	
  museum	
  only	
  29	
  were	
  
found	
  to	
  be	
  qualified	
  for	
  the	
  data	
  
collection,	
  which	
  means	
  that	
  this	
  
small	
  sample	
  size	
  might	
  not	
  be	
  
representative	
  of	
  the	
  whole	
  popu-­‐
lation.	
  Thus,	
  it	
  must	
  be	
  taken	
  into	
  
consideration	
  that	
  if	
  a	
  larger	
  sam-­‐
ple	
  size	
  were	
  analyzed,	
  then	
  the	
  
percentage	
  of	
  anterior	
  crowding	
  
might	
  be	
  closer	
  to	
  the	
  suggested	
  
two-­‐thirds.	
  It	
  must	
  also	
  be	
  taken	
  
into	
  consideration	
  that	
  a	
  skull	
  col-­‐
lection	
  sold	
  as	
  a	
  museum	
  might	
  
have	
  been	
  selective	
  and	
  not	
  an	
  
accurate	
  representation	
  of	
  the	
  
population.	
  

In	
  conclusion,	
  from	
  the	
  
small	
  sample	
  size	
  of	
  a	
  population	
  
living	
  a	
  century	
  ago	
  it	
  was	
  deter-­‐
mined	
  that	
  anterior	
  crowding	
  was	
  
present	
  in	
  55%	
  of	
  the	
  population	
  
(56%	
  in	
  males	
  and	
  50%	
  in	
  fe-­‐
males),	
  which	
  is	
  comparable	
  to	
  the	
  
research	
  suggested	
  two-­‐thirds	
  
(66%).	
  

References	
  

1.	
  Late	
  mandibular	
  incisor	
  
crowding.	
  American	
  Association	
  of	
  
Orthodontics:	
  Orthodontic	
  Dia-­‐
logue.	
  1999;11(1).	
  

2.	
  Caries	
  and	
  periodontal	
  
disease:	
  insight	
  from	
  two	
  US	
  popu-­‐
lations	
  living	
  a	
  century	
  apart.	
  Rose	
  
E,	
  Vieira	
  AR.	
  Oral	
  Health	
  Prev	
  
Dent.	
  2008;6(1):23–8.	
  
PMID:18399304	
  

3.	
  Orthodontics.	
  Part	
  3:	
  Pa-­‐
tient	
  assessment	
  and	
  examination	
  
II.	
  Roberts-­‐Harry	
  D,	
  Sandy	
  J.	
  Br	
  

Table 3. Comparison of crowding by age and sex. 

 

Specimens 
positive for 

anterior 
crowding 

Specimens 
negative for 

anterior 
crowding 

Percent of 
specimens 
positive for 

anterior 
crowding 

Males 
<40 4 3 57.1 

Males 
>40 9 7 56.3 

Females 
<40 1 3 25 

Females 
>40 2 0 - 



	
  	
  Observing	
  Anterior	
  Crowding	
  In	
  a	
  Population	
  Living	
  a	
  Century	
  Ago	
  

Vol	
  4,	
  No	
  1	
  (2016)	
  	
  	
  	
  DOI	
  10.5195/d3000.2016.52	
  

	
  http://dentistry3000.pitt.edu	
  
5	
  

Dent	
  J.	
  2003	
  Nov	
  22;195(10):563–
5.	
  PMID:14631426	
  

4.	
  Goldberg	
  AI.	
  An	
  evalua-­‐
tion	
  of	
  mandibular	
  anterior	
  crowd-­‐
ing	
  as	
  it	
  relates	
  to	
  facial	
  diver-­‐
gence	
  in	
  treated	
  and	
  untreated	
  
subjects.	
  2012;	
  A	
  thesis	
  presented	
  
to	
  the	
  Graduate	
  Faculty	
  of	
  Saint	
  
Louis	
  University	
  in	
  partial	
  fulfill-­‐
ment	
  of	
  the	
  requirements	
  for	
  the	
  
degree	
  of	
  Master	
  of	
  Science	
  in	
  
Dentistry.	
  

5.	
  The	
  effect	
  of	
  extraction	
  
of	
  third	
  molars	
  on	
  late	
  lower	
  inci-­‐
sor	
  crowding:	
  a	
  randomized	
  con-­‐
trolled	
  trial.	
  Harradine	
  NW,	
  Pear-­‐
son	
  MH,	
  Toth	
  B.	
  Br	
  J	
  Orthod.	
  1998	
  
May;25(2):117-­‐22.	
  PMID:9668994	
  

6.	
  Mandibular	
  anterior	
  
bony	
  support	
  and	
  incisor	
  crowd-­‐
ing:	
  Is	
  there	
  a	
  relationship?	
  Uysal	
  
T,	
  Yagci	
  A,	
  Ozer	
  T,	
  Veli	
  I,	
  Ozturk	
  A.	
  
Am	
  J	
  Orthod	
  Dentofacial	
  Orthop.	
  
2012	
  Nov;142(5):645–53.	
  
PMID:23116505