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Dr. Mohammed Alruby
Orthodontics for G.P
Etiology of Malocclusion
For general practitioners
Prepared by
Dr. M Alruby

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Dr. Mohammed Alruby
Orthodontics for G.P
Etiology in orthodontics is the study of actual causes of dento – facial abnormalities.
Malocclusion is the condition where there is a deviation from the usual or accepted relationship,
dental malocclusion exists when the individual teeth within one or both jaws are abnormally
related to each other, this condition may be limited to a couple of teeth or involving the majority
of teeth present.
Development of normal dentition and occlusion depends on a number of interrelated factors that
include the dento alveolar, skeletal and the neuromuscular factors. Thus localization of the
possible etiology may be a very difficult task.
A- Extrinsic factors:
1- Evolution:
With evolution, the jaws become smaller, reduction in the number and size of teeth and
diminution of jaw projection together with increased in vertical height of the face and there is
retrognathic tendency in man as he ascends the evolutionary scale.
2- Heredity:
Transmission of dento facial characteristic through generation by genes. The child is a product
of parents who have dissimilar genetic material. Thus the child may inherit conflicting traits from
both the parents resulting in abnormalities of the dentofacial region. Another reason attributed
for genetically determined malocclusion is the racial, ethnic and regional intermixer, which
might have led to uncoordinated inheritance of teeth and jaws.
There are three types of transmission of malocclusion from the stand point of genetics:
1- Repetitive: the recurrence of single dentofacial deviation within the immediate family.
2- Discontinuous: a tendency for a malocclusion trait to reappear within the family over
several generations.
3- Variable: the occurrence of different but related types of malocclusion within several
generation of the same family.
Dental defect of genetic origin include the following:
= Crowding and spacing of teeth.
= Size and characteristic of soft tissue including muscles and frenum.
= Macrognathia and micrognathia.
= Macrodontia and microdontia.
= Oligodontia.
= Tooth shape variations.
= Median diastemas.
= upper face height, nose height, and bigonial width.
= Bimaxillary protrusion.
4- Congenital:
Those are deformities of hereditary or non-hereditary origin but exciting at birth.
The congenital abnormalities that cause malocclusion:
= Cleft lip and palate:
lack of fusion between the two palatal processes to each other. From one third to one half of all
cleft palate children have familial history of this deformity.

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Dr. Mohammed Alruby
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As with the non-cleft child, palatal, pharyngeal and perioral musculature is well developed at
birth to meet the demand of suckling, deglutition and mastication. While the complete unilateral
or complete bilateral cleft break the continuity of the upper lip and disturbs the functional
pattern and significantly reduce the restraining effect of the buccinators mechanism that produce
malocclusion.
The cleft palate may lead to:
**Under development and retruded maxilla due to continuation of the oral cavity to the nasal
cavity that affect the pressure of air cells in the nose and maxillary sinus that stimulate the
growth of maxilla.
** Excessive intra oral clearance.
**Lingually tipped incisors
The cleft lip may lead to:
** Collapse of the maxillary arch.
** Protrusion of anterior segment.
The cleft soft palate: not affect the malocclusion but effect on speech.
In case of surgically corrected cleft palate the malocclusion may be due to faulty surgery, scar
tissue and interference with function or with the growth centers of the jaws.
= Cerebral palsy:
Is a paralysis or lake of muscular coordination due to inter cranial lesion. The varying degree of
abnormal muscular function may occur in mastication, deglutition, respiration and speech.
This uncontrolled muscle activity gives rise difficulty in establishment and maintenance of
normal occlusion.
= Torticollis:
Is the foreshortening of the sterno-clido-mastoid muscle that causes profound changes in the
bony morphology of the cranium and face. Facial a symmetry with dental malocclusion may be
created if this problem not treated fairly early.
= Cleidocranial dysostosis:
Another congenital defect characterized by:
1- Unilateral or bilateral complete or partial absence of the clavicle.
2- Delayed closure of the cranial sutures.
3- Maxillary retrusion.
4- Mandibular protrusion.
5- Retarded eruption of permanent teeth.
6- Retained deciduous teeth.
7- Supernumerary teeth are common.
8- Multimpacted tooth.
= Cranio facial dysotosis:
The same as the Cleidocranial dysotosois but the clavicles are normal.
=Mandibulo facial dysostosis: characterized by
1- Hypoplasia of facial bone especially of the mandible ------- bird face appearance
2- Crowding and malposition of teeth.
= Micrognathia:
Abnormal small jaw, maxilla or the mandible may be affected.
In mandible: sever retrusion of the chin, steep mandibular plane, retrognathic profile,
In maxilla: retruded middle third of the face, deficient premaxilla, and prognathic profile.
= Macrognathia:

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Dr. Mohammed Alruby
Orthodontics for G.P
Abnormally large jaw, the macro-gnathia may be true due to actual prognathism of the jaw or
relative due to underdevelopment of one jaw to the other.
=Tongue tie:
Is a congenital condition caused by shortness or excessive anterior prolongation of the lingual
frenum on the undersurface of the tongue.
Effects: 1- constriction of maxillary arch.
2-difficulties in eating, swallowing and speech
3-periodontal disease mandibular segment.
= Microglassia and a glossia:
Rare condition characterized by small tongue or rudimentary tongue but a glossia characterized
by completely absence of tongue. This condition lead to difficulty in eating and speech with
collapsed dental arches.
Macroglossia:
Abnormal large tongue that lead to:
1- Spacing and flaring of teeth.
2- Tongue thrust out of the mouth that leads to open bite.
3- Abnormal tongue posture over the occlusal surface that leads to open bite.
4- Difficulty in eating , respiration, swallowing and speech
5-Environment:
1- Prenatal influences:
The fetus is well protected against injuries and nutritional; deficiencies during pregnancy. But
there are certain factors, the presence of which can results in abnormal growth of the orofacial
region thereby predisposing to malocclusion. Abnormal fetal posture during gestation is said to
interfere with symmetric development of the face. Most of thses deformities are temporary and
usually disappear as age advances.
The other prenatal influences include maternal fibroids, amniotic lesions. Maternal infection
such as measles and use of certain drugs during pregnancy such as Thalidomide can cause gross
congenital deformities including clefts.
2- Postnatal factors:
The following are some of the post- natal factors that can cause malocclusion:
a- Forceps delivery can result in injury to the temporomandibular joint are, which can
undergo ankylosis such patients show retarded mandibular growth and thus have a
hypoplastic mandible.
b- Cerebral palsy is a condition characterized by muscle incoordination. This may occur due
to birth injuries. The patient can exhibit malocclusion due to loss of muscle balance.
c- Traumatic injuries that can cause condylar fracture can cause growth retardation
resulting in marked facial asymmetry.
d- Presence of scar tissue such as those caused by burn or as a result of cleft lip surgery may
produce malocclusion due to their restrictive influences on growth.
6-endocrine imbalance:
No tissue in the body is escape from some sort of abnormal influences either in the course
of its development and growth or in the functional activities. The following are some of the
endocrine disturbance that can cause malocclusion.
Hypothyroidism: Characterized by presence of one or more of the following features:

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Dr. Mohammed Alruby
Orthodontics for G.P
a- Retardation in rate of calcium deposition in bones and teeth.
b- Marked delay in tooth bud formation and eruption of teeth.
c- The deciduous teeth are often over retained and the permanent teeth are slow to erupt.
d- Abnormal root resorption.
e- Irregularities in tooth arrangement and crowding of teeth can occur.
Hyperthyroidism: this condition characterized by increase in the rate of maturation and an
increase in metabolic rate. The patient exhibits premature eruption of deciduous teeth, disturbed
root resorption of deciduous teeth and early eruption of permanent teeth. The patient may have
osteoporosis which contraindicates orthodontic treatment.
Hypoparathyrodism: this endocrinal disorder is associated with changes in calcium metabolism.
It can cause delay in tooth eruption, altered tooth morphology, delayed eruption of deciduous
and permanent teeth.
Hyperparathyroidism: produces increase in blood calcium. There is demineralization of bone
and disruption of trabecular pattern. In growing children, interruption of tooth development
occurs. The teeth may become mobile due to loss of cortical bone and resorption of alveolar
process.
7-Nutritional deficiency:
Nutritional deficiencies during growth may result in abnormal development, causing
malocclusion. These diseases are more common in the developing countries than in the
developed world. Nutrition related disturbances such as Ricketts, Scurvy and Beriberi can
produce severe malocclusion and may upset the dental development timetable.
8-Accident and trauma:
Accident is more significant factor in malocclusion. As the child is learn to crawl and walk the
face and dental arches receive trauma. Traumatic displacement of deciduous incisors may affect
the normal eruption of permanent successors. Blow or trauma is responsible for ankylosis of
teeth and the resultant malocclusion, ankylosis of TMJ early in life interfere with growth and
normal tooth alignment. Dental trauma can leads to malocclusion by three ways:
1- Damage of permanent tooth buds from injury to primary teeth.
2- Drift of permanent teeth after premature loss of primary teeth.
3- Direct injury to permanent teeth.
9-Muscle action:
The facial muscles can affect jaw growth in two ways:
1- The formation of bone at the point of muscle attachement depends on the activity of
muscles.
2- The musculature is important part of the total soft tissue matrix whose growth normally
carries the jaws downward and forward.
Muscle weakness is found to be associated with underdevelopment of the mandible; strong
muscle action is associated with strong well developed jaws but not necessarily with good dental
alignment. Deep over bite may be caused by strong elevator muscles that do not permit full
eruption of the buccal teeth. Open bite may be associated in many cases with weak mandibular
musculature.
Hyper active mentalis muscle cause flattening of mandibular anterior segment and mandibular
arch collapse and protrusion of maxillary incisors due to lower lip trap during swallowing.

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Dr. Mohammed Alruby
Orthodontics for G.P
Hypo tonicity of lower lip causes protrusion of maxillary teeth, it is commonly seen in Class II
division 1, on the other hand the hyper tonic upper lip may causes retroclination of maxillary
incisors which often seen in Class II division 2.
10-Abnormal pressure habits:
(1) Thumb sucking:-
It is repeated forceful sucking of the thumb with associated strong buccal and lip contractions.
The problem is start when the habit extended after 4 years of age that lead to development of
malocclusion that characterized by:
= Protrusion of maxillary teeth.
= Spacing of upper anterior teeth.
= High palatal vault.
= Retraction and crowding of lower anterior teeth.
= Excessive over jet.
= Class II division 1 or Class III when the mandible is pulled forward.
N.B: the severity of the effects produced by thumb
Sucking will depend on its force, duration, and frequency.
Treatment: firstly the child must understand that is done
for his benefits and not as a part of punishment.
The child may be shown a cast or photographs of mouth
of children, who have had detrimental sucking habits,
Show the treatment results too, to establish what can
be done with the dentist's help. The best appliance is palatal arch wire with short spurs soldered
at strategic location remain the thumb to keep out. The oral shield can be used to aid in the
correction of thumb sucking but it requires an unusual amount of patient cooperation.

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Dr. Mohammed Alruby
Orthodontics for G.P
(2) Tongue thrust and abnormal swallowing habits:
The subject of tongue thrust and abnormal swallowing habits is extremely controversial, and the
correlation between these habits and dental malocclusion is to establish. Firstly I need to give
the reader an idea about the normal swallowing as follow:
= Normal infant swallowing:
The tongue lies between the gum pads.
The mandible stabilized by the contraction of facial muscles.

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Dr. Mohammed Alruby
Orthodontics for G.P
This type is present in the neonate and gradually disappears with the eruption of the buccal teeth
in primary dentition.
The cessation of the infant swallow and appearance of mature swallow is an on and off
phenomena but there is a transitional period or transitional swallowing.
= Normal mature swallowing:
Teeth are present in centric occlusion.
Muscles of facial expression are in rest.
Contraction of the elevator muscles to bring the teeth into occlusion.
A) - Simple tongue thrust swallowing:
Contraction of the lips, mentalis and mandibular elevator muscles.
The teeth are in occlusion (tooth together swallow) but the tongue is thrust to give an anterior
seal for the open bite.
The open bite is well circumscribed and has definite begging and ending, this open is due to
thumb sucking.
The incidence of simple tongue thrust swallow is diminishes with increasing the age.
Treatment: firstly we need to change the behavior of the tongue swallowing by instruct the
patient to the normal pattern of swallowing and the normal position of the tongue during
swallowing, should be instruct the patient practically to the correct swallowing at least 40 times
daily. A well-adapted soldered palatal arch wire having short sharp strategically placed spurs
can be inserted. Protectively, the tongue is withdrawn from the abnormal position and placed
properly during swallowing.
B) - Complex tongue thrust swallowing:
There is a contraction of the lips, mentalis and facial muscles and lack of contraction of the
mandibular elevators.
The open bite of this type is more diffused than the simple type and difficult to define.
When examined the dental casts there is poor occlusal fit and instability of intercuspation
because the intercuspal position is not repeatedly reinforced during swallowing.
Treatment: at the start of treatment the patient attention must brought to the problem and the
difficult prognosis explained carefully, the patient should know at the start of treatment, that
much responsibility for successful therapy lies with himself or herself.
Follow the steps as for simple tongue thrust swallowing.
C) – Retained infantile swallowing:
= Persistence of infant type of swallow after eruption of permanent teeth, this patient
demonstrates very strong contraction of the lips and facial muscles.
= Tongue thrust strongly between the anterior and posterior teeth.
= patient has high difficulty in mastication in mastication, the patient occlude only on one molar
in each quadrant.
= patient has inexpressive face, and the facial muscles used for stabilizing the mandible during
swallow.
= this type occurs due to defect on the transitional phase of swallowing from infant to adult
swallow.
= the prognosis for correction of this type of swallow is poor. Fortunately, the true retained
infantile swallow is rare.

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Dr. Mohammed Alruby
Orthodontics for G.P
3) Abnormal tongue posture:
The continuous effect of abnormal tongue posture may produce more open bite than obvious
tongue thrust.
During the arrival of the teeth, the tongue normally change its posture and come to rest inside
the encircling dentition, some children have an inherently abnormal tongue posture problems are
not unaesthetic and there is stability of the incisor relationship even a mild open bite is seen.
= the acquired protracted tongue posture is a simpler matter, since it usually results from
chronic pharyngitis, tonsillitis or other naso-respiratory disturbance, sometimes the
nasopharyngeal condition no larger exist but the tongue remain in a forward position.

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Dr. Mohammed Alruby
Orthodontics for G.P
Treatment: A well-adapted soldered palatal arch wire having short sharp strategically placed
spurs can be inserted. Protectively, the tongue is withdrawn from the abnormal position and
placed properly during swallowing.
4) Mouth breathing:
Mouth breathing means habitual respiration through the mouth instead of the nose. Normal
dentofacial development require normal nasal breathing, the mouth breathing may be developed
as a result of:
1- Partial nasal obstruction.
2- Inflammatory reaction of the nasal mucosa.
3- Increased free way space and absence of anterior lip seal
4- Heart disease.
The low tongue and mandibular posture in case of mouth breathing have very deleterious effect
on normal dentofacial growth.
The patient of mouth breathing characterized by:
1- Gingival hypertrophy that make bleeding during sleep.
2- Narrow and collapsed maxilla.
3- Hypotonic upper lip.( reduction of normal muscle tone)
4- Hypertrophy of lower lip.
5- Increased over bite due to increased over jet and loss of incisal stop.
6- Protrusion of maxillary incisors.
7- Posterior cross bite.
8- Gonial angle is larger than normal.
9- Increased anterior facial height.
Treatment: 1- reduction of nasal air way obstruction, prior to and dental treatment, the child
should be referred to a rhinologist for the removal of the nasal and pharyngeal obstructions if
present.
2-interception of habits. Many children continue to breathe through the mouth, especially at
night, even after removal of the adenoids. In such cases the habit must be corrected by using an
oral screen (a piece of plastic material that rests in the labial and buccal vestibule and prevent
the passage of air through the mouth after adenoidectomy)
3- Correction of malocclusion.
5) Tongue sucking:
This habit can occur habitually or due to macroglossia and its activity is similar to the sucking
and usually disappears about 2 years of life, tongue sucking may cause anterior or posterior
open bite.
Treatment: 1- changes the behavior of the tongue.
2- Use of habit breaking appliance as tongue guard.
3- Correct the malocclusion.
6) Lip sucking and lip biting:
Lip sucking may appear by itself or it may be seen with thumb sucking, the lower lip the most
frequently involved and also the upper lip may be involved.
This habit may be lead to:
= labio- version of maxillary anterior teeth.
= Linguo version of mandibular teeth.
= lip hypertrophy.

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Dr. Mohammed Alruby
Orthodontics for G.P
The deformity reaches its maximum level when the discrepancy between the maxillary and the
mandibular incisors become equal to the thickness of lower lip.
Treatment: use of oral screen (oral shield).
7) Abnormal posture:
Poor postural condition can cause malocclusion.
Chin propping habit: extrinsic pressure, unintentional may cause a deep anterior closed bite, and
may also cause the mandible to be retracted. Note that there is little of lower anterior teeth is
visible when the jaws are in closed position.
Face leaning: lateral pressure, unintentional may cause lingual movement of maxillary teeth on
that side, the mandible being less affected because it does not have a rigid attachment and slide
away from the pressure.
Head posture: faulty head posture can cause abnormal changes in the form of jaw bones.
Curvature of the neck and cervical spine causes forward and upward positioning of the head
which is commonly associated with Class II malocclusion. So the child must held in an upright
posture to prevent pressure on the face.
Mandibular posture: low mandibular posture associated with mouth breathing initiate abnormal
neuromuscular reflexes. Which may be responsible for production of Class II malocclusion and
open bite.
8) Bottle feeding:
The mass of tissue taken into the mouth by the child nursing at the breast exerts a spreading
action on the jaws and aids in their normal growth. In addition the tongue movement inside the
mouth during the breast feeding is ideal and so help in development of normal swallowing
behavior. In the bottle feeding the spreading action is absent, the milk from the bottle is follow by
the action of sucking that produce a negative pressure in the mouth which contract the cheeks
and compress the jaws.
9) Nail biting:
One of the most common habits in children and adults, it is a sign of internal tension. Absent less
than 3 years of age, there is a rapid increase at 6 year of age followed by sharp rise at puberty
and followed by rapid decline after age of 16 in boys.
After the age of 15 year, the nail biting is replaced by pencil biting, lip biting.
The clinical nail bitter shows:
= Crowding,
= Rotation,
= Attrition at incisal edge of the teeth especially the lower incisors,
= Tendency of Class III malocclusion.
Management: = in mild cases of nail biting treatment usually not indicated, since the child will
probably transfer to some other activity at later age. Treatment should be by removing the basic
emotional factors causing the act.
Use of oral shield is effective.
10) Pillowing habit:

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Dr. Mohammed Alruby
Orthodontics for G.P
= Postural defect during sleep are considered as an etiologic factor in the development of
malocclusion, the effect depend upon the frequency, duration and the amount of pressure exerted
by the abnormal postures, also depend upon the resistance of the bone to deformation.
= Flattening of the skull and facial a symmetry may occasionally developed during the 1st
year of
life with the head turned to the right or the left for longer time.
= The pillow of the child must be at the level of his shoulders and not too high or low, and the
mother must change the position of her child at frequent intervals.
B- Intrinsic or local factors:
1- Anomalies in tooth number:
= supernumerary teeth: occur most commonly in
maxilla near the midline palatal to maxillary incisors.
These teeth are usually conical in shape and occur most
often singly but can occur in pairs. May be fused to the
right or left central incisors. The supernumerary
tooth leads to crowding that lead to positional and
occlusal anomalies malocclusion and arch a symmetry.
The supernumerary teeth may be:
Mesiodens: between the maxillary centeral incisors.
Peridens: buccal to the arch.
Distomolars: distal to the 3rd
molars.
Paramolars: buccal or lingual to the molars.
= Missing teeth: Congenital missing teeth are more
frequent than supernumerary teeth. Where the
supernumerary teeth are usually found in the maxilla
the missing teeth are frequent in both arches. The order
of frequency of absence is:
1- Maxillary and mandibular third molars.
2- Maxillary lateral incisors.
3- Maxillary second premolars.
4- Mandibular second premolars.
2- Anomalies of tooth size:
The size of the teeth is largely determined by hereditary.
There is a great variation in tooth size even with the same
individual.
Macrodontia: tooth is large than normal that may cause crowding.
Microdontia: abnormally small tooth.
3- Anomalies of tooth shape: anomalies of tooth shape are very interrelated, abnormally
shaped tooth predisposing to malocclusion, the following are some of the examples of
frequently seen tooth shape anomalies:
a- The presence of peg shaped lateral maxillary incisors is often accompanied by spacing
and migration of teeth.
b- Presence of abnormally large cingulum on the maxillary incisors. The presence of
exaggerated cingulum prevents establishment of normal over bite and over jet. The
involved tooth is usually in labio-version due to the forces of occlusion.

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Dr. Mohammed Alruby
Orthodontics for G.P
c- The mandibular second premolars may rarely have an additional lingual cusp, thereby
increasing the mesio – distal dimension of the tooth.
d- Congenital syphilis is often associated with abnormal tooth form. Peg shaped lateral is
classical finding of such patients.
e- Anomalies of shape can occur as a result of developmental defects like amelogenesis
imperfect, hypoplasia of tooth, fusion and gemination.
f- Dilaceration is described as a condition characterized by abnormal angulation between
the crown and the root of a tooth or angulation within the root. It usually occur due to
a blow to a deciduous tooth which transmitted to the underlying tooth bud. Dilacerated
teeth fail to erupt to normal level and can thus cause malocclusion.
4- Abnormal labial frenum:
At birth the frenum is attached to the alveolar ridge with fibers actually running into the labial
inter dental papilla. As the teeth erupt and as the alveolar bone deposited the frenum migrate
superiorly to the alveolar ridge, the fibers may persist between the maxillary centeral incisors
and attaching to the outer layer of the periosteum. This attachment may interfere with the normal
closure that results into media distema.
5- Premature loss of deciduous teeth:
This refers to loss of a tooth before its permanent successor is sufficiently advanced in
development and eruption to occupy its place. The deciduous teeth serve as space saver for the
permanent teeth and also assist in maintaining the opposing teeth at the proper occlusal level.
Premature loss of maxillary deciduous incisors:
= lead to shifting and dental arch deviation.
= space maintainer may be required to prevent lisping as well as esthetic purpose.
Premature loss of mandibular deciduous incisors:
= crowding of permanent one.
= deep over bite and collapse of anterior segment.
= space maintainer must be constructed.
Premature loss of deciduous canines:

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Dr. Mohammed Alruby
Orthodontics for G.P
= interfere with the eruption of permanent one because late of eruption of canine in relation to
other teeth.
Premature loss of 1st
deciduous molars:
= if premature loss occur before eruption of the 1st
permanent molars strong force will be
exerted on 2nd
deciduous molar causing it to shift mesially and close some of the space.
= if premature loss occur during active eruption of the lateral incisors strong force will exerted
on the primary canine causing it to shift distally and close the space.
Premature loss of 2nd
deciduous molar:
= if extraction occur before eruption of 1st
permanent molar, the 1st
permanent molar will erupt
mesially close much space required for 2nd
premolar and impaction may be occur.
= if extraction occur after eruption of 1st
permanent molar, the 1st
permanent molar show slight
or severe mesial tilting.
Effect of loss of posterior primary teeth:
= collapse of lower anterior teeth and centeral line may be shifted to the side of extraction.
= as a result of premature loss of both upper and lower 2nd
deciduous molars,psudo mesio
occlusion may occur as the child will protrude the mandible to bring the lower anterior teeth in
contact with the upper to achieve a bite of comfort.
= mesial tilting of mandibular 1st
permanent molars with impaction or palatal eruption of 2nd
premolars.
6- Prolonged retention of deciduous teeth:
This refers to a condition where there is undue retention of deciduous teeth beyond the usual
eruption age of their permanent successors.
Causes:
a- Incomplete or unequal resorption of the roots.
b- Absence of permanent tooth.
c- Ankylosis of deciduous tooth.
d- Abnormal path of eruption of permanent teeth.
Effects:
a- Deflection of permanent teeth buccally or lingually.
b- Impaction of permanent teeth.
c- Prolonged retention of deciduous incisors or canine usually results in the deflection of the
permanent successors with disturbances of occlusion.

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Dr. Mohammed Alruby
Orthodontics for G.P
7- Delayed eruption of permanent teeth:
The retarded eruption of permanent teeth can cause disturbances in the arrangement of teeth
because of shifting of erupted teeth producing lack of space for the coming teeth.
Causes:
a- Presence of supernumerary tooth.
b- Trauma of tooth germ.
c- Infection of tooth germ.
d- Ankylosis of tooth with the jaw bones.
e- Systemic disease such as endocrine disturbance.
8- Abnormal eruptive path:
Causes:
a- Sever crowding and totally inadequate space to accommodate all of the teeth. So the
deflection of the erupting tooth is response to that.
b- Presence of supernumerary tooth, retained deciduous tooth or root fragment or bony
barrier often influences the direction of eruption.
c- Trauma of the deciduous tooth may turn the development of successor in an abnormal
direction.
d- Early Class II therapy against the maxillary arch to move the maxillary dentition
posteriorly can cause the maxillary second molars teeth to erupt into cross bite or can
impact the developing third molar more deeply.
e- Some abnormal eruptive paths are of unknown origin (idiopathic).
Effects:
a- Crowding and malposition.
b- Impaction.
9- Ankylosis:
Is a condition where a part or whole of the root surface is directly fused to the bone with the
absence of the intervening periodontal membrane.
Ankylosed deciduous tooth should be extracted as soon as diagnosed to permit erupting of
successor.
10-Dental caries:
Caries lead to:
= premature loss of deciduous or permanent teeth.
= abnormal axial inclination.
= over eruption.
= subsequent drifting of the contiguous tooth.
The carious tooth should be repaired not only to prevent infection and loss of teeth but to
maintain the integrity of dental arches.
11-Improper dental restoration:
Improper dental restoration which not contoured to the anatomical landmarks of the teeth may
lead to:
= poor inter proximal contact and shifting of teeth.
= over eruption of teeth due to under filling.

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Orthodontics for G.P
= traumatic occlusion due to premature contact.
= periodontal disease.
= food impaction and secondary caries.
12-Loss of permanent teeth:
Every individual tooth as an essential key stone not only for one arch but also for both arches.
The removal of single tooth may lead to:
= break the continuity of the arc hand shifting.
= elongation of the tooth.
1- Loss of centeral incisors:
Produce mesial shifting of lateral incisors that lead to space between lateral and canine and
mesial shifting of canine.
2- Loss of lateral incisors:
Produce distal shifting of centeral incisors and mesial shifting of canine.
3- Loss of canine:
Produce distal shifting of lateral and rotation of premolars.
4- Loss of 1st
premolar:
Produce distal shifting of canine and mesial shifting of posterior teeth and may be with rotation.
5- Loss of 2nd
premolar:
Produce distal shifting of the 1st
premolar, and mesial shifting of the molar and the 1st
molar may
show lingual inclination and loss of occlusal contact.
6- Loss of 1st
molar:
Produce distal shifting of the premolars.
= in maxilla: the premolars shift together and collapse of the arch.
= in mandible: the premolars shift single and create space between them.
7- Loss of 2nd
permanent molar:
Produce mesial inclination and shifting of third molar.
8- Loss of 3rd
molar:
Does not produce distal shifting of 2nd
molar.