Definition: Simple crowding is defined as
disharmony between the size of the teeth and the
space available for them.
It is crowding uncomplicated by skeletal,
muscular, or occlusal functional features.
Simple crowding is most frequently associated
with a class I molar relationship, although it may
be found with class II horizontal type (maxillary
dental protraction and normal facial skeleton).
Definition: Complex crowding is crowding caused
and complicated by skeletal imbalance, abnormal
lip and tongue functioning, and/or occlusal
dysfunction as well as disharmony between the
sized of the teeth and the available space.
Signs of Arch Length
Children exhibit arch length deficiencies for two
(1) the arch length of some children is too small
to accommodate the size of the teeth; and
(2) a child may start with an adequate arch
length but may develop a deficient arch length
from a variety of environmental factors that affect
the dentition (e.g., caries or loss of teeth)
MEASUREMENT OF THE AVAILABLE
ARCH LENGTH IN THE MIXED DENTITION
Measure arch length segments from the buccal
and labial sides of the arch at the contact points
between the teeth
The main purpose of the mixed
dentition space analysis is to
differentiate patients with severely
crowded arches from those who have
up to as much as 4 mm of incisor
crowding but who still have enough
room in the entire arch, as a result of
leeway space, for successful eruption
of the permanent premolars and
canines and proper alignment of the
These patients are excellent candidates for a
lower lingual arch or palatal holding arch.
Treatment of these patients with a lingual or
palatal arch provides them with an important
and beneficial service.
Intervention with these two preventive appliances
can eliminate the need for future orthodontic
treatment or simplify future orthodontic treatment.
Patients predicted to have crowding of 5 or more
mm in an arch should be referred to the
This is also an important service to patients and
Arch length deficiencies occur in the mixed
dentition for two reasons: (1) the arch length is
too small to accommodate the size of the teeth
and (2) arch length is lost because of local
When the deficiency results from an
imbalance between the size of the teeth
and the arch, primary canines are
prematurely exfoliated by the erupting
incisors and the distances between the
distal surfaces of the permanent lateral
incisors and mesial surfaces of the
primary first molars are small or
In the early mixed dentition, the permanent
incisors and first molars are erupted.
The permanent canines and premolars
have not erupted.
Their mesial-distal widths can be
measured on periapical radiographs, but
the images are enlarged in comparison to
the true widths of the teeth.
Orthodontists have devised several methods of
predicting the size of the nonerupted canines and
The prediction methods use three basic predictor
variables: (1) only erupted teeth, (2) only
measurements from radiographs, and (3) a
combination of variables 1 and 2.
All methods of prediction involve error. The error
of a prediction method is called its standard
error of estimate.
The late mixed dentition starts with the eruption
of one of the permanent canines or premolars.
If most of the canines and premolars are erupted
and if the nonerupted tooth or teeth are easily
measured on a periapical radiograph, an
alternative prediction method can be used.
The method corrects the radiographic
enlargement of a nonerupted tooth.
The mesial-distal widths of the nonerupted
tooth and an erupted tooth are measured on
the same periapical radiograph.
The mesial-distal width of the erupted tooth is
measured on a plaster cast.
These three measurements provide the elements
of a proportion that can be solved to obtain the
width of the non-erupted tooth on the cast.
A simple proportional relationship can be setup:
True width of primary molar
Apparent width of primary molar
True width of unerupted premolar
Apparent width of unerupted premolar
True width of primary molar
Apparent width of primary molar
True width of unerupted premolar
App width of
Tanaka and Johnston (1974) and Moyers
(1988) created non-radiographic
prediction methods by correlating the sum
of the widths of the lower permanent
incisors with the sum of the widths of the
lower premolars and canine on one side
of the arch.
There is a reasonably good correlation between
the size of the erupted permanent incisors and
the unerupted canines and premolars.
These data have been tabulated for white
American children by Moyers.
To utilize the Moyers prediction tables, the
mesiodistal width of the lower incisors is
measured and this number is used to predict the
size of both the lower and upper unerupted
canines and premolars.
The size of the lower incisors correlates better
with the size of the upper canines and premolars
than does the size of the upper incisors, because
upper lateral incisors are extremely variable
Despite a tendency to overestimate the size of
unerupted teeth, accuracy with this method is
fairly good for the northern European white
children on whose data it is based.
No radiographs are required, and it can be used
for the upper or lower arch.
Tanaka and Johnston
Tanaka and Johnston developed another way to
use the width of the lower incisors to predict the
size of unerupted canines and premolars.
For children from a European population group,
the method has a good accuracy despite a small
bias toward overestimating the unerupted tooth
TANAKA AND JOHNSTON PREDICTION VALUES
One half of the
mesiodistal width of
the four lower
+10.5 mm =
Estimated width of mandibular
canine and premolars in one
Estimated width of maxillary
canine and premolars in one
If the analysis predicts borderline crowding of
+2mm to −4mm in both arches of a Class I
patient, consider holding arch length with a
palatal (Nance) arch and a lower lingual
This intervention may prevent the need for future
orthodontic treatment, or at least reduce the
severity of the malocclusion.
If the analysis predicts severe crowding in excess of
−6 mm in one or both arches of a Class I patient,
holding arches are not needed.
In patients with crowding, primary canines may be
extracted in both upper and lower arches to allow the
permanent lateral incisors to erupt and to prevent the
erupting incisors from shifting to the right or left of the
The crowded malocclusion will require
comprehensive orthodontic treatment. These patients
may benefit from serial extraction treatment.
If the analysis predicts borderline crowding
between +2mm and −5mm in the lower arch of a
Class II patient, it is important to place a lower
lingual holding arch to preserve arch length.
If the lower holding arch allows the permanent teeth
mesial to the first molars to erupt, the eventual
treatment of a nonsurgical Class II malocclusion will
It should be clear that holding lower arch length per
se with an appliance will not correct the Class II
If the analysis predicts severe crowding in
excess of −5mm in the lower arch of a Class II
patient, a lingual holding arch may still be
appropriate for the nonsurgical malocclusion.
These patients have a malocclusion that is very
difficult to treat, and they should be referred for
comprehensive orthodontic treatment.
If the analysis predicts borderline crowding of
+2mm to −5mm in the upper arch of a Class III
patient, it is important to place a palatal holding
arch to preserve arch length.
In these patients, extraction of premolars to
relieve upper arch crowding complicates
orthodontic treatment. Holding upper arch length
will not correct the Class III malocclusion but can
assist in the eventual treatment of a nonsurgical
If the analysis predicts severe crowding in
excess of −6mm in the lower arch of a Class III
patient, a holding arch may be appropriate.
The arch length preserved by the holding arch
could enable an orthodontist to retract lower
anterior teeth in a nonsurgical Class III
These patients should be referred for
comprehensive orthodontic treatment.
Crowding can be classified
Mild crowding – upto 1.5mm
Moderate crowding – 1.5 to 5mm
Severe crowding – 6 to 8 mm
Mild crowding can be treated by several
methods. Cases that require only a simple
tipping movement may often be treated with a
removable appliance such as a spring retainer
Moderate crowding may be treated with either
extraction or nonextraction of permanent teeth.
Severe crowding teeth would need to be
extracted to create adequate space.
Serial Extraction in Severely Crowded
Cases in the Mixed Dentition
When a patient is diagnosed with a Class I
malocclusion and a severe TSALD of 8 to 10 mm
or greater during the early mixed dentition, a
decision may be made by the orthodontist that
the patient would ultimately require extraction of
four premolars to allow space for the proper
alignment of the remaining teeth.
The stepwise management of crowding involves the
following steps :
2.Disking of primary teeth
3.Extractions of overretained teeth/ rootpieces
etc.Serial extractions if crowding is severe.
4.Corrective orthodontic referral.
Clinical observation reveals that if the physiologic spaces
are between 2 -6mm there is a fifty percent chance that
the crowding will self resolve.
If the physiologic spaces are more than 6 mm then there will
be no crowding.
CAUSES OF CROWDING IN MODERN DENTITIONS :
1.Inherited discrepancy between tooth size and jaw size
2.Increase in cross racial marriages
3.Change in dietary habits
4.Early loss of primary teeth
5.Over retained deciduous teeth.
Classification of Crowding
1.Premature tooth loss but no space loss
2.Localised crowding : less than 3 mm
3.Localised crowding : more than 3 mm
4.Moderate generalized crowding : less than 4 mm
5.Severe generalised crowding : 4 to 9 mm
6.Very severe generalised crowding : more than 10mm
Premature Tooth Loss With Adequate
Space: Space Maintenance
Early loss of a primary tooth presents a potential
alignment problem because drift of permanent or
other primary teeth is likely unless it is prevented.
Space maintenance is appropriate only when
adequate space is available and all unerupted
teeth are present and at the proper stage of
If there is not enough space or if succedaneous
teeth are missing, space maintenance alone is
PREMATURE TOOTH LOSS BUT
1. Band & loop space maintainer
2. Partial denture space maintainer
3. Distal shoe space maintainer
4. Lingual arch space maintainer
5. Mild to moderate crowding of incisors with
Band and Loop Space
The band and loop is a unilateral fixed appliance
indicated for space maintenance in the posterior
The simple cantilever design makes it ideal for
isolated unilateral space maintenance.
Because the loop has limited strength, this appliance
must be restricted to holding the space of one tooth
and is not expected to accept functional forces of
Although bonding a rigid or flexible wire across the
edentulous space has been advocated as an
alternative, this has not proved satisfactory clinically.
It also is no longer considered advisable to solder the
loop portion to a stainless steel crown because this
precludes simple appliance removal and
Teeth with stainless steel crowns should be banded
like natural teeth
If a primary second molar has been lost, the band
can be placed on either the primary first molar or the
erupted permanent first molar.
Some clinicians prefer to band the primary tooth in
this situation because of the risk of decalcification
around any band, but primary first molars are
challenging to band because of their morphology,
which converges occlusally and makes band
A more important consideration is the eruption
sequence of the succedaneous teeth.
The primary first molar should not be banded if
the first premolar is developing more rapidly than
the second premolar, because loss of the banded
abutment tooth would require replacement of the
Before eruption of the permanent incisors, if a
single primary molar has been lost bilaterally, a
pair of band and loop maintainers are
recommended instead of the lingual arch that
would be used if the patient were older.
This is advisable because the permanent incisor
tooth buds are lingual to the primary incisors and
often erupt lingually.
The bilateral band and loops enable the
permanent incisors to erupt without interference
from a lingual archwire
At a later time the two band-and-loop appliances
can be replaced with a single lingual arch if
The partial denture is most useful for bilateral
posterior space maintenance when more than
one tooth has been lost per segment and the
permanent incisors have not yet erupted.
In these cases because of the length of the
edentulous pace band and loop space
maintainers are contraindicated and the lingual
position of the unerupted permanent incisors and
their likely lingual position at initial eruption make
the lingual arch a poor choice.
The partial denture also has the advantage of
replacing occlusal function.
Another indication for this appliance is
posterior space maintenance in
conjunction with replacement of missing
primary or delayed permanent incisors,
Anterior space maintenance is
unnecessary because arch circumference
generally is not lost even if the teeth drift
and redistribute the space, so
replacement of missing anterior teeth is
done solely to improve appearance.
This has social advantages even for
Distal Shoe Space
The distal shoe is the appliance of choice
when a primary second molar is lost
before eruption of the permanent first
This appliance consists of a metal or
plastic guide plane along which the
permanent molar erupts.
The guide plane is attached to a fixed or
removable retaining device.
When fixed, the distal shoe is usually retained
with a band instead of a stainless steel crown so
that it can be replaced by another type of space
maintainer after the permanent first molar erupts.
Unfortunately, this design limits the strength of
the appliance and provides no functional
replacement for the missing tooth.
If primary first and second molars are missing,
the appliance must be removable and the guide
plane is incorporated into a partial denture
because of the length of the edentulous span.
This type of appliance can provide some occlusal
To be effective, the guide plane must
extend into the alveolar process so that it
contacts the permanent first molar
approximately l mm below the mesial
marginal ridge, at or before its emergence
from the bone.
An appliance of this type is tolerated well
by most children, but is contraindicated in
patients who are at risk for subacute
bacterial endocarditis or are immuno-
compromised, because complete
epithelialization around the intra-alveolar
portion has not been demonstrated.
Careful measurement and positioning are
necessary to ensure that the blade will
ultimately guide the permanent molar.
Faulty positioning is the most common
problem with this appliance
Measurement on the radiograph: The outline
of the distal shoe is designed on radiograph. The
mesio-distal length of the horizontal position of
the distal shoe should be as long as the
maximum width of the second primary molar and
vertical height should be about 1 mm under the
mesial contour of the unerupted first permanent
Distal Shoe Space Maintainer
Intra alveolar appliance
Loss of ‘E; before
eruption of ‘6’
Lingual Arch Space
A lingual arch is indicated for space maintenance
when multiple primary posterior teeth are missing
and the permanent incisors have erupted.
A conventional lingual arch, attached to bands on
the primary second or permanent first molars and
contacting the maxillary or mandibular incisors,
prevents anterior movement of the posterior
teeth and posterior movement of the anterior
A lingual arch space maintainer is usually
soldered to the molar bands but can be
removable, depending on the number of
adjustments anticipated and the care of the
appliance expected from the patient.
Removable lingual arches (e.g.,those that fit into
attachments welded onto the bands) are more
prone to breakage and loss.
Regardless of whether it is removable, the
lingual arch should be positioned to rest
on the cingula of the incisors,
approximately 1 to l.5 mm off the soft
tissue, and should be stepped to the
lingual in the canine region to remain
away from the primary molars and
The most common problems with lingual
arches are distortion, breakage and loss.
Careful instructions to parents and
patients can reduce these problems.
Maxillary lingual arches as space
maintainers are not familiar to many
clinicians but are contraindicated only in
patients whose bite depth causes the lower
incisors to contact the archwire on the
lingual of the maxillary incisors.
When bite depth does not allow use of a
conventional design, either the Nance
lingual arch or a transpalatal arch can be
The Nance arch is an effective space maintainer,
but soft tissue irritation can be a problem.
The best indication for a transpalatal arch is
when one side of the arch is intact and several
primary teeth are missing on the other side.
In this situation, the rigid attachment to the intact
side usually provides adequate stability for space
When primary molars have been lost bilaterally
however, both permanent molars may tip
mesially despite the transpalatal arch, and a
conventional lingual arch or Nance arch is
Localized Space Loss (3mm or less):
After premature loss of a primary tooth, space
may be lost from drift of other teeth before a
dentist is consulted.
Repositioning the teeth to regain space rather
than just space maintenance is required.
Up to 3 mm of space can be reestablished in a
localized area with relatively simple appliances
and a good prognosis
Maxillary Space Regaining
Generally, space is easier to regain in the
maxillary than in the mandibular arch, because of
the increased anchorage for removable
appliances afforded by the palatal vault and the
possibility for use of extraoral force (headgear).
Permanent maxillary first molars can be tipped
distally to regain space with either a fixed or
removable appliance, but bodily movement
requires a fixed appliance.
Because the molars tend to tip forward and
rotate mesiolingually, distal tipping to regain 2-
3mm often is satisfactory.
A removable appliance retained with Adams'
clasps and incorporating a helical fingerspring
adjacent to the tooth to be moved is very
effective. This appliance is the ideal design for
tipping one molar.
One posterior tooth can be moved
up to 3 mm distally during 3 to 4
months of full-time appliance wear.
The spring is activated
approximately 2 mm to produce 1
mm of movement per month.
The molar generally will derotate
spontaneously as it is tipped distally.
For unilateral bodily space regaining, a
fixed intra-arch appliance is preferred.
The excellent anchorage provided by the
remaining teeth and palate can support
the forces generated by a coil spring on a
segmental archwire to produce distal
movement of the molar on only one side,
with good success.
If bodily movement of both permanent maxillary
first molars is necessary in regaining space, this
can be accomplished by using a banded and
bonded fixed appliance or headgear.
Sometimes both molars need to be moved
distally but one requires substantially more
movement than the other.
To accomplish this, an asymmetric facebow with
a neckstrap attachment can be used.
’This will result in more movement on the side
with the longer outer bow but will also move that
tooth toward lingual crossbite.
Asymmetric cervical headgear is neither as easyt
o adjust nor as comfortable to wear as symmetric
headgear, and it requires excellent patient
For space regaining, it should be used only to
deal with bilateral but asymmetric space loss-not
true unilateral space loss, which is treated best
with a removable or fixed appliances
Regardless o f the method used to regain these
limited amounts of space a, space maintainer is
required when adequate space has been
A fixed space maintainer is recommended rather
than trying to maintain the space with the
removable appliance that was used for space
Moderate and Severe
For children with amoderate space deficiency,
usually there is generalized but not severe
crowding of the incisors.
Other times the primary canines are lost to
ectopic eruption of thelateral incisors and more
severe crowding goes largely unrecognized.
Usually when the permanent canines are
erupting the real extent of the problem is noted.
Children with moderate crowding and inadequate space in
the early mixed dentition face one of two choices.
Either the arch will need to be expanded to accommodate
the permanent teeth or some permanent teeth will need to
Generally, if the lower incisor position is normal or
somewhat retrusive, lips are normal or retrusive, the
overjet is adequate, the overbite is not excessive, and
there is good keratinized tissue facial to the lower incisors,
some facial movement of the incisors and expansion can
If facial movement is anticipated and the amount and
quality of tissue is questionable, a periodontal consultation
about a gingival graft is appropriate.
Surgical or nonsurgical management of the tissue
may be required prior to beginning the tooth
A conservative approach to this dilemma is to place a
Iingual arch after the extraction of the primary canines
and allow the incisors to align themselves.
Ultimately the lingual arch or another appliance can
be used to increase the arch length.
A word of caution is necessary here.
Clinical experi-ence indicates that a considerable
degree of faciolingual irregularity will resolve if space
is available, but rotational irregularity will not.
If the incisors are rotated, severely irregular or spaced
and early correction is felt to be important, a multiply
bonded and banded appliance is indicated
Lower incisor teeth usually can be tipped 1 to
2mm facially without much difficulty, which create
sup to 4mm of additional arch length.
If the overbite is excessive and the upper and
lower incisors are in contact, however, facial
movement of the lower incisors will not be
possible unless the upper incisors also are
When expansion by tipping the incisors facially is
indicated, two methods should be considered.
The other method is to band the permanent
molars, bond brackets on the incisors, and use a
compressed coil spring on a labial archwire to
gain the additional space.
Early Treatment of Severe
A key question, which remains unanswered, is
whether early expansion of the arches (before all
permanent teeth erupt) gives more stable results
than later expansion (in the early permanent
Partly in response to the realization that recurrent
crowding occurs in many patients who were
treated with premolar extractions a number of
approaches to early arch expansion recently
have regained some popularity in spite of a lack
of data to document their effectiveness.
Expansion can involve any combination of
several possibilities: maxillary dental or skeletal
expansion, moving the teeth facially or opening
the midpalatal suture; mandibular buccal
segment expansion by facial movement of the
teeth; or advancement of the incisors and distal
movement of the molars in either arch.
A less aggressive approach is to expand the
upper arch in the early mixed dentition, using a
lingual arch (or perhaps a jack screw expander
but this must be done carefully and slowly in the
early mixed dentition) to produce dental and
Late Mixed Dentition Treatment for
One alternative is a functional appliance that
incorporates lip and buccal shields or a lip
bumper to reduce the resting pressure of the lips
and cheeks and produce dental expansion
Lip pads and buccal shields will lead to anterior
movement of the incisors and buccal movement
of the primary molars or premolars, which allows
the teeth to align themselves along a larger arch
Last, several approaches can be used for either
severe crowding or severe localized space loss
that focus on increasing arch circumference by
repositioning molars distally and often moving
incisor forward sometimes with the same
appliance and its side effects
There are three major limitations to this
the long duration of treatment from the primary or
early mixed dentition through the eruption of the
the possibility of creating unesthetic dentoalveolar
and the uncertain stability of the long-term result.
Distal Molar Movement
If bodily distal movement of one or both
permanent maxillary first molars is necessary to
adjust molar relationships and gain space, if
there are adequate anterior teeth for anchorage,
and if some anterior incisor movement can be
tolerated, several appliances can be considered.
All are built around the use of a heavy lingual
arch, usually with an acrylic pad against the
anterior palate to provide anchorage.
To tip or bodily move molars distally, extraoral force via a
facebow to the molars is the most effective and straightfor-
The force is directed specifically to the teeth that need to
be moved, and reciprocal forces are not distributed on the
other teeth that are in the correct positions.
The force should be as nearly constant as possible to
provide effective tooth movement and should be light
because it is concentrated against only two teeth.
The more the child wears the headgear,the better; 14 to 16
hours per day is minimal.
Approximately100gm of force per side is appropriate.
Lip bumpers are capable of the following:-
Correct lip biting habit
Upright lingually tipped lower incisors
Correct mild crowding of anterior teeth
Distalize the molar teeth
Act as space regainer
Help to re-inforce anchorage
They are screen like devices, which shield the dentition
from perioral musculature.
They are also referred to as Lip plumpers.
They may be made for the maxillary or mandibular
The type of anchorage used is Intra-