2. Malocclusion:
Malocclusion is a condition in which there is a malrelationship between the arches
in any of the planes of the space or in which there are anomalies in tooth position
beyond the limit of the normal. (WALTHER & HOUSTON)
According to Angle: the key to occlusion was the maxillary 1st molar
ā¢ Class I (normal occlusion)
ā¢ Class I malocclusion
ā¢ Class II malocclusion
ā¢ Class III malocclusion
3. CLASSIFICATION
Depending upon which part of the oral & maxillofacial unit is at fault :
1. Individual tooth malposition's (DENTAL DYSPLASIA)
2. Malrelationās of the dental arches or dento alveolar segments. (SKELETODENTAL DYSPLASIA)
3. Skeletal malrelationship (SKELETAL DYSPLASIA)
4. I. Individual tooth malposition's (DENTAL DYSPLASIA)
o These are malocclusions of individual teeth in relation to adjacent teeth with in same dental
arch.
o This disorder is also called intra arch malocclusions.
o This malocclusion includes condition like spacing or crowding with in dental arches.
They are of following type:
5. 1. MESIAL
INCLINATION
OR TIPPING
2. DISTAL
INCLINATION OR
TIPPING
3. LINGUAL
INCLINATION
OR TIPPING
4.LABIAL/BUCCAL
INCLINATION OR TIPPING 5.INFRA OCCLUSION
6.SUPRAOCCLUSION
7.ROTATIONS :-
a.Mesiolingual or distolabial b. Distolingual or mesiolabial
8.TRANSPOSITION
6. ii. Malrelation's of Dental Arches:
o These characterized by an abnormal relationship between teeth or groups of teeth of one
dental arch to another arch.
o These occur in all the three planes of space, namely ā
> sagittal plane
> vertical plane
> transverse plane
7. SAGITTAL PLANE MALOCCLUSION
a. Pre normal occlusion:
Where the mandibular dental arch is
placed more posteriorly when the
teeth meet in centric occlusion.
b. Post normal occlusion:
Where the mandibular dental arch is
place more distally when the teeth
meet in centric occlusion.
9. TRANSVERS PLANE MALOCCLUSION
These includes various types of cross bites due to constriction of the
dental arches or some other reason the relationship is disturbed.
10. iii. SKELETAL MALOCCLUSIONS:
o These malocclusions are caused due to the defect in the underlying skeletal structure itself.
o The defect can be in size position or relationship b/w the jaw bones.
12. Specific causes of malocclusion:
A. Disturbances in embryological development
ā¢ Causes: range from genetic disturbances to
specific environmental insults
ā¢ Teratogens: chemical and other agents
capable of producing embryologic defects if
given at the critical time
ā¢ <1% of children who need orthodontics had
a disturbance in embryologic development
as a major contributing cause.
B. Skeletal growth disturbances
ā¢ Fetal molding and birth injuries
ā Intrauterine molding: pressure against
the face
ā Birth trauma to the mandible: use
forceps in delivery
ā Childhood fracture of the jaw
13. C. Muscle dysfunction:
ā¢ Damage to motor nerve āunderdevelopment
of that part of the face (Muscle atrophy).
ā¢ Excessive muscle contraction of neck on one
side can resist growth in the same way as
scaring after injury ā facial asymmetry
D. Acromegaly:
ā¢ It is caused by anterior pituitary gland tumor
that causes excessive secretion of growth
hormones.
ā¢ Excessive growth of the mandible
class III malocclusion
E. Disturbances of dental development:
ā¢ Congenitally missing teeth
ā¢ Malformed or supernumerary teeth
ā¢ Interferences with eruption
ā¢ Ectopic eruption
ā¢ Early loss of primary teeth
ā¢ Traumatic displacement of teeth
F. Hemi mandibular hypertrophy:
ā¢ unilateral Excessive growth of the mandible
15. Genetic influence:
ā¢ Inherited in 2 major ways:
ā Disproportion between the size of the teeth and the size of the jaws (Teeth vs Jaw)
ā Disproportion between size or shape of the upper and lower jaws (Upper vs Lower)
16. Environmental influences:
ā¢ If a habit like thumb sucking created pressure against the teeth for more than the
threshold duration (6 hours or more per day), it certainly could move teeth.
Thumb sucking:
ā¢ During primary dentition: no influence
ā¢ If it persists beyond the time that the permanent teeth begin to erupt:
ā Flared and spaced maxillary incisors
ā Lingually positioned lower incisors
ā Anterior open bite
ā A narrow upper arch
17. A malocclusion where the molar relationship shows
the buccal groove of the mandibular first molar
distally positioned when in occlusion with the
mesiobuccal cusp of the maxillary first molar.
The mesiobuccal cusp of the maxillary first molar is
aligned with the buccal groove of the mandibular first
molar. There is alignment of the teeth, normal overbite
and overjet and coincident maxillary and mandibular
midlines.
A normal molar relationship exists but there is
crowding, misalignment of the teeth, cross bites, etc.
A malocclusion where the molar relationship shows
the buccal groove of the mandibular first molar
mesially positioned to the mesiobuccal cusp of the
maxillary first molar when the teeth are in
occlusion.