Download Sheet #9 / Dr.Abd Alrahman / Suzan Hussein

27/11/2014
orthodontics lecture #9
Suzan Hussein
 Local causes of malocclusion:
1. Variation in tooth number
2. Variation in tooth size or form
3. Abnormalities in teeth position
 Variation in teeth size and form:
Teeth could be too large, too small or have an odd form.
1. Macrodontia:
Slide #60: If we compared the size of the right central incisor with the left, we
notice that there is a big difference in the size.
Teeth that are lager in size than normal>>macrodontia
Why are we concerned regarding macrodontia??
 Crowding
 Esthetics
-Management includes several options:
We can accept the tooth as it is if the patient has no esthetic concerns.
Trimming is not easy because we have a large tooth and a large pulp chamber
and trimming can endanger the pulp, so what we do is gradual interproximal
reduction and this will cause the deposition of secondary or tertiary dentine
and recession of the pulp, however most patients aren’t patient and the more
common treatment includes RCT and a full coverage crown. Extraction is rarely
an option and we always go for the most conservative approach.
2.Microdontia:
Teeth that are smaller in size than normal.
It can be accompanied by hypodontia.
27/11/2014
orthodontics lecture #9
Suzan Hussein
Hypodontia can also be associated with impacted canines and peg shaped
laterals, so hypodontia ,microdontia and impacted canines are connected to each
other.
-Treatment includes veneers for the small sized teeth. Patients with microdontia
associated with hypodontia are often referred to orthodontists for space
redistribution to allow for an adequate space for placement of implants. In some
cases space closure is required.
Slide #62: closing the median diastema allows for a larger space for placement of
implant.
So treatment options include:
1. Accept
2. Orthodontic treatment only (space closure)
3. Orthodontic treatment (space redistribution) followed by restorative
treatment
3. Abnormal Form:
 peg shaped laterals
Problems associated :1. Esthetics 2.spacing
 Germination (one tooth bud divides into two teeth) or fusion (when two
tooth buds fuse together to make one large wide crown)
Problems: mainly esthetics
 Talon cusps
An anomalous structure projecting lingually from the cingulum area of a maxillary
or mandibular permanent incisor.
Affect occlusion mainly and can sometimes cause premature contact.
Management is by gradual grinding of the cusps.
27/11/2014
orthodontics lecture #9
Suzan Hussein
 Abnormalities of tooth position
1-Ectopic teeth
Third molars (most common)
Upper canines mostly but sometimes lower canines as well.
First permanent molars
Upper centrals
2. Transpositions
 Ectopic canines :
 Prevalence:
Impaction 2%
Palatal most common 61%
In line of the arch 34%
Buccal 4.5%
Why do we have impacted canine?
1) Long path of eruption
The canine travels from the base of the nose downward then jumps from the
palatal side to the buccal side to erupt.
2) Guidance theory
The roots of the lateral incisor guide the canine to erupt. If the lateral was
congenitally missing or if we had a peg-shaped lateral incisor the canine fails to
erupt.
27/11/2014
orthodontics lecture #9
Suzan Hussein
3) Crowding
Crowding could be a result of a variety of factors (early loss of primary
teeth...) and it usually results in buccal impaction of the canine, where the
canine has no space to erupt.
4) Genetic factors
a-prevalence varies with different populations
b-affects females more commonly than males
c-familial occurrence
d-occurs bilaterally with a greater than expected frequency
e-occurs in association with other dental anomalies
 Ectopic first molar:
-Slide #69:
Here we have an ectopic 1st molar where the 6 is erupted under the E. This mainly
occurs in the upper arch and is rarely found in the lower arch.
 Causes:
-small arch
-mesial eruption angle of the 6 instead of vertical eruption
 Possible effects:
- Impaction of the 2nd premolar (6 migrated forward and took the space of the 5)
or the 5 erupts but takes the place of the canine causing canine impaction.
-class 2 malocclusion
-irreversible pulpitis of the E caused by food impaction and caries or internal
resorption of the pulp.
27/11/2014
orthodontics lecture #9
Suzan Hussein
-it can also be asymptomatic, but the main concern regarding ectopic 1st molars is
loss of space.
 Treatment:
66% of the cases are reversible impaction where there is spontaneous correction,
we don’t do anything. We wait 3-6 months, if there is no improvement then we
intervene.
 Ectopic upper central incisors :
Slide # 73: we have a retained primary incisor, the permanent incisor is absent. It
could be ectopic.
When should we be concerned?
-asymmetry of eruption
-sequence of eruption is changed
We take X-rays to aid in the diagnosis
Differential diagnosis:
1. Supernumerary
2. Dilacerations
3. missing (rare)
 Transposition:
the positional interchange of 2 adjacent teeth.
Slide #76: interchange in the position between the 1st premolar and canine.
It can either true or false:
True>>transposition of the roots along with the crown
27/11/2014
orthodontics lecture #9
Suzan Hussein
False>>transposition of the crown only. If we took an x-ray, we see the roots cross
each other but don’t hit each other or cause resorption.
Problems:
1) Occlusion.
2) Esthetics
It is very difficult to treat these cases. If we take the case in slide #76 as an
example, what we need to do is bring the premolar backward and the canine
forward. At one point both of them will be in front of each other in order for
them to cross to the opposite side and because the width of the bone is less
than the width of both teeth, the teeth will be positioned outside the bone.
 Classification: three part code:
1. Jaw of occurrence :
Mx>>maxilla
Mn>>mandible
2. Transposed tooth:
L1 >central incisor
L2 >lateral incisor
C >canine
P1 >1st premolar
P2 >2nd premolar
M1 >1st molar
M2 >2nd molar
3. Site of transposition
Ex: Mx.P1.C>>transposition of premolar to the canine position.
Why not the opposite? Because the premolar erupts before the canine.
-Treatment: we accept them as they are
Slide #79:
Here we have the central then lateral then C and we can see a small bulge which
is the canine, so here we have transposition.
27/11/2014
orthodontics lecture #9
Suzan Hussein
Treatment option in such a case include:
1) Extraction of the C, then we bring the lateral backwards and move the
canine downward. After that we do trimming for the lateral to make it look
like a canine and trimming of the canine to look like a lateral tooth but still
we have problems, the canine is more yellowish in color and so even after
trimming it appears more yellow and its root is more prominent than what
a lateral incisor should be.
2) Extract the canine and leave the C, but it’s still a primary tooth and it can be
lost.
 Failure of eruption :
It could be either primary or secondary.
-Primary: the tooth fails to erupt at all and stays within the bone.
-Secondary: the tooth penetrates the gingiva and enters the oral cavity
then fails to continue eruption for no known reason.
It could be either localized or generalized.
-Treatment: these teeth can’t be treated by orthodontics because it will
cause ankyloses (cause is unkown). The only option is onlay if it was
localized and small or surgery (sub-apical osteotomy).
Failure of eruption can occur in both dentitions.
 Median diastema:
Causes:
1) Microdontia
2) Hypodontia
3) Ugly duckling stage (physiological diastema) >>canine causes
pressure on the roots of the lateral, once the canine erupts, the
diastema will disappear, no orthodontic treatment required. If we do
27/11/2014
orthodontics lecture #9
Suzan Hussein
ortho treatment and alignment at this age, the crown of the canine
will cause resorption of the root of the lateral incisor.
4) High frenal attachment
The frenum goes all the way to the incisive papilla. This is diagnosed
by blanching.
5) Improper fusion of maxilla and this can sometimes be accompanied
with high frenal attachment. It can be seen in x-ray.
-Treatment: we usually only do tipping movement or slow movement
of the central incisors mesially, and this will cause deposition of bone
and closure of the diastema.
GOOD LUCK