Introduction to Orthodontics Fifth Year

1. Malocclusion

Malocclusion is defined as condition where there is a deviation from the normal relation of the teeth to
other teeth in the same arch and to teeth in the opposing arch .

It might be simple or complex .

Normal occlusion :- The mesiobuccal cusp of the max. first molar is aligned with the buccal groove of the man. first
molar.
- there is alignment of the teeth , normal overbite and overjet and coincident maxillary and mandibular
midlines.
A- Teeth :
1- Mesial inclination ;
Describes a tooth which is abnormally tilted so that its crown leans along the line of dental arch
toward the midline of the arch.
2- Mesial displacement ;
Describes a tooth which is bodily displaced towards the midline of the dental arch.
3- Distal inclination ;
The opposite of the mesial inclination , where the tooth tilted along line of dental arch so that its
crown too far away from the midline of the arch.
4- Distal displacement ;
Describes a tooth which is bodily displaced in adirection away from tha midline of the arch .
5- Lingual inclination ;
Refers to a tooth so tilted so that its crown leans toward the tongue.
Retro-clinatin is a term frequently used also to refer to the lingual tilting of the anterior teeth.
6- Lingual displacement ;
A tooth bodily displaced toward the tongue .

2. 7- Labial inclination ;
.A term used to describe the outward tilting of incisor and canine teeth towards the lips (proclination
may used to describe this condition ).
.In the case of the molars and premolars , the term “buccal” inclination is used .
.The composite term “vestibular” may be used to embrace both „labial‟ and buccal when indicating
the outer side of the dental arch.
8- Labial and buccal displacement ;
Is used similarly to describe bodily displacement of teeth in an outward direction.
9- Infraclusion;
A term used to describe a tooth of which the occlusal surface or incisal edge has not reached the
same leve as the rest of the teeth in the arch, i.e., it does not appear to have erupted sufficiently.
10- Supraclusion ;
The opposite of the infraclusion , i.e., the tooth appears to have “over-erupted” .
11- Mesiolingual rotation ;
Describes a tooth which is rotated around its long axis so that its mesial aspect is turned towards the
tongue .
12- Distolingual rotation ;
Describes a rotation in the opposite direction.
13- Imbrications
describes teeth ( especially lower incisors ) which are irregularly arranged within the arch due to lack
of space for them.
14- Transposition
is a term used to describe a condition where two teeth appear to have exchange places during the
development of occlusion. Perhaps this is most often seen where upper canine and an upper first
premolar or lateral incisor on the same side of the arch are transposed .

3. B- Dental arches :

could be in any direction :. Anteroposterior
. Vertival
. Transverse
1- post normal occlusion :

This is used to describe a condition where the lower dental arch appears to be too far-back in relation to
the upper arch when the teeth are closed in centric occlusion and the mandibular condyles are in their
normal position within the glenoid fossa.
2- Pre-normal occlusion ;

.This is used to describe a condition where the lower dental arch is in advance of the upper when teeth
are closed in centric occlusion and the condyles are in their normal position within the glenoid fossa.
. Psuedo…. .
3- Crossbite ;

It is a discrepancy in the baccolingual or in the transverse direction, on one or both sides.

The occlusion may be such that buccal cusps of one or more of the posterior teeth may occlude within
the fossa of the lowers . Lowers is wider than upper.

Where the discrepancy is mild it is likely that a cusp to cusp relationship of the teeth will cause
premature contact of the affected cusps as the jaws close .

In order to avoid this mandible may assume a position other than centric occlusion by deviation to one
side . This will give false impression that one side alone is affected.

Buccal crossbite ; in such a way that the buccal cusps pf the lower teeth occlude buccal to buccal cusps
of the upper teeth.

Lingual crossbite is a condition where the upper arch is completely contained within the lower or where
the lower arch is contained within the upper on closure . The buccal cusps of the lower teeth occlude
lingual to the lingual cusps of the upper teeth . This known as SCISSORS bite.
4- Open-bite ;

In these cases only the most distal teeth in the dental arch may occlude. When the jaws are closed , a
space exists between the rest of the teeth in the upper jaw and those of lower. Such space progressively
increases anteriorly.

4. 5- Bimaxillary protrusion ;

This is a forward or mesial position in the skull of both dental arches. Frequently the arches are of good
form, the teeth even , and the occlusion normal. The face seems full of teeth , especially with a smile.
.Extraction…
6- Deep overbite ;

Where the crown of the upper incisors cover more than one third of the lower when the teeth are in
centric occlusion.

.Deep impenging overbite , where the incisal edge of the loer teeth touch the palate ( complete overbite )
7- Incomplete overbite ;

It is a term used to indicate that vertical space exists between the lower incisors and the palatal aspects
of the upper incisors where the teeth are in centric occlusion .

This space may be penetrated by the tip of the tongue at rest , and during swallowing.
89- Increased interocclusal clearance ;( or increased free way space):

When a child closes jaws into centric occlusion there may be an increased incisor overbite which is
brought about by an excessive distance between the occlusal surfaces of the upper and lower posterior
teeth when the mandible is in the rest position.
C- Dental bases :
Dental base relations can be classified into the terms skeletal 1,2 or 3 in the anteroposterior direction
when the jaws are closed and the teeth are in full occlusion .

CLASS 1 ;
The bones of the face and jaws are in harmony with one another and with the rest of the head. The profile is
orthognathic.

CLASS 2 ;
.Subnormal , distal mandibular development in relation to the maxilla or postnormal relation of the dental
bases. The profile is retrognathic .

CLASS 3 ; .Overgrowth of the mandible and obtuse mandibular angle , the profile is prognathic at the
mandible or a prenormal relation of the dental bases .

5. Classification of malocclusion
The classification by Edward angle in 1899 produced a useful aid in diagnosis and treatment planning.
Angle used the roman numerals 1, 2, and 3 to designate the 3 main classes of mesiodistal arch relation. He
employed the Arabic numerals 1 and 2 to denote division of the classification.
Class 1:
The lower dental arch is at normal relation to the upper arch as evidenced by the occlusion of the mesiobuccal cusp of the upper 1st permanent molar in the buccal groove of the lower 1st permanent molar.
Providing no drifting of these teeth has occurred, and if the deciduous molars are still present, due
allowance has been made for the wider mesiodistal width of the lower deciduod molars.
A-Local abnormalities:
1.
2.
3.
4.
crowding of upper and lower incisors
labial inclination of uper anterior teeth with lower incisors in lingual inclination of varying degrees.
labial inclination of both upper and lower anterior teeth( bimaxillary, protrusion)
one or more of the upper anterior teeth are in lingual occlusion with the lower anterior teeth(anterior
cross-bite)
5. rotation of the incisors
6. posterior crossbite, uni or bilateral.
7. local abnormalities due to premature loss of deciduous molars which is often followed by forward tilt of
the permanent molars and loss of space for the premolars.
Extraction of permanent teeth, the presence of supernumerary teeth, absence of teeth and prolonged retention of
primary teeth are other local conditions, which give rise to abnormality in individual tooth position.
B-vertical malrelationship
1. excessive overbite: the majority of deep overbite problems can be divided into 2 categories. Skeletal and
dental.
Skeletal type or deep overbite may be due to either malrelation of alveloa bone and or underlying
mandibular or maxillary bones or to an overgrowth or undergrowth of alveolar segments
2. deficient or anterio open-bite: these cases the anterior teth are not in contact in all excursions of
mandible it may be the result of:
class 2:
typically the lower arch is in distal relation to the upper arch, the distobuccal cusp of upper 1st permanent
molar occludes in the buccal groove of the lower 1st molar, by an abnormal intercuspation of the premolars
to the extent of the lower 1st premolar occluding where the lower 2nd premolar normally occlude and by the
occlusion of the lower canine distal to the upper.
There are 2 divsions of class 2. Each capable of occurring on one side only, a condition described by the
suffix “unilateral” which has termed subdivision by angle.

6. Class 2 division 1






the upper incisors are proclined, such that the overjet may be as much as 14 mm.
the lower incisors frequently meet the palatal mucosa when the jaws are occluded.
short lip with failure in the anterior lip seal due to its unfavorable appearances which usually are often
accompanied by deep overbite.
an upper arch which is narrow in the canine and premolar region broadening between the molars and
giving rise to the typical V-shaped arch.
mandible may be deficient and chin underdeveloped.
mouth breathing may be present.
Class 2 division 1 subdivision:
It has same general characteristics except that its unilateral.
Class 2 division 2






the upper centrals show lingual inclination but may be overlapped by the upper laterals with the result of
their imbrication
upper arch is usually broad while incisors overbite is deep, both upper and lower incisors being in
apparent supra-occlusion.
both arches have a rather square appearance, this is due to lingual inclination of the incisors.
upper lip is of normal length and contacts he lower lip through there may be a deep mental groove below
the latter. These cases are often accompanied by prominent malar processes.
mandible is of good size
no mouth breathing involved
Class 3


The lower arch is at mesial relation to the upper arch in such a way that the lower 1st permanent molar
may be as much as a full premolar width mesial to upper 1st permanent molar, though there are often
lesser degree of mesial reation.
Incisors may occlude edge to edge, the lower incisors may be in advance of upper incisors or rarely the
lower incisors may still present their ncisal tips lingual to those of the upper incisors.
Class 3 devided into:
1- trueprenormality:
 this always involves an anterioposterior relation of the dental bases. The mandible is either excessively
large or there is a lack of forward growth of the maxilla. In many cases there is a combination of both.
Therefor when the teeth are in centric occlusion, the mandibular condyles are within the glenoid fossae
and mandible cannot be retruded further than a mm or 2.
 there are found to be hereditary other members of the family being affected.
 pressure from lower lip causes lower incisors to inclined lingually, whereas pressure from the tongue
may cause the upper incisors to be inclined labially.
 incisor overbite is small

7. 2-pseudo prenormality



this condition the mandible is protruded a little during the final stages of closure to avoid premature
contact of incisor or canine.
Its most likely to arise in cases where the relation of the incisors is edge to edge and may be caused by
mildly prenormal relation of dental base. Or by premature loss of upper molars.
Incisor overbite is large and the jaws have the appearance of being over closed when teeth are
approximated such psedo or postural class 3 cases may tend if untreated, where the condition is present
only on one side as it is referred to as unilateral.
Validity of angles classification
classification is without foundation for the following reasons:




1st permanent molars are not fixed points in skull anatomy
as it now realized it is possible to have the dental arches on one relation while basal bones at another, eg.
A dental arch class 2 might be superimposed upon skeletal class 1.
1-In class 2 cases the classification does not differentiate between true mandibular retrusion and
maxillary protrusion and also in class 3 cases doesn‟t differentiate between true mandibular protrusion
and maxillary retrusion.
2-angles classification is incomplete as a basis for diagnosis. It only attempts to embrace anomalies in
the anteroposterior direction. It cant be applied to differentiate anomalies in vertical nor transverse
directions.