Etiology of Malocclusion (Oral Recit)

Etiology

in orthodontics, is the study of actual causes of dento-facial abnormalities

Malocclusion

deviation from the usual or accepted occlusion or occlusal relationship

Malocclusion

exists when the individual teeth within one or both jaws abnormally related to each other, this condition may be limited to a couple of teeth or involving the majority of teeth presents.

Orthodontic equation

is an expression of the development of any dento-facial deformity

Orthodontic equation

Cause --------- acts at a certain time --------- on tissue – produce --- results

Primary etiologic sites

1. Neuromuscular system

2. Bone

3. Teeth

muscle group that serve most frequently as primary etiologic sites

1. muscles of mastication

2. muscles of facial expression

3. tongue

neuromuscular system

plays its primary role in the etiology of dentofacial deformity by the effect of abnormal contraction of bony skeleton and the dentition. Both bones and teeth are affected by the many functional activities of orofacial region

Bone

changes in dental arches growth may alter the occlusal and functional relationship.

Teeth

may be primary sites in the etiology of dentofacial deformity in many ways Gross variation in size and shape are encountered frequently and always are of concern Decrease or increase in the regular number of teeth will give rise malocclusion

A-1 Evolution

With evolution, the jaws become smaller, reduction in number and size of teeth and diminution of jaw projections together with increased in vertical height of the face and there is a retrognathic tendency in mans as he ascends the evolutionary scale

A-2 Heredity

Transmission of dentofacial characteristics through generations by genes. Most authors between 1900-- 1920 did not completely determine the role of inheritance in determination of the form, size and proportion of dentofacial skeleton, but they stress their work upon the effect of the environmental factors, and at this time they were hardly belief that the effect of local lack of function is more important.

Bennet statement

the size, form and density of bones such as maxilla and mandible varies according to the extent to which these structure are used during period of growth – (function stimulate growth)

Walk Joff statement

the form and degree of development of maxilla and mandible depends upon the magnitude of functional stimuli of muscles acting upon these structures.

Baker

his study was performed on animals by unilateral amputation of muscles of mastication, he found lack of growth on the affected side.

Brash

studied the facial form and the dental development in twins on genetic bases, he also emphasized the genetic facial pattern of some royal families in Europe where they had been inter marriage, his studies gave the best evidence to support the role of inheritance

Axel Lundstorm

1925 showed that, the form and size of dental bases and the teeth are genetically determined, when the size of the teeth and their basal arches are not correlated, problems of crowding or spacing will be arising.

Broadbent and Hofrath 1931

developed standardized cephalometric x-ray technique which permit serial longitudinal studies of facial growth, by these studies the concept of inheritance growth pattern arises

three types of transmission of malocclusion from the standpoint of genetics

1. Repetitive

2. Discontinuous

3. Variable

Repetitive

the recurrence of single dentofacial deviation within the immediate family

Discontinuous

a tendency for mal-occlusal trait to reappear within the family over several generation

Variable

the occurrence of different but related types of malocclusion within several generation of the same family

Dental defect of genetic origin includes the following:

1- Crowding and spacing of teeth

2- Size and characteristic of the soft tissue including muscles and Frenum

3- Facial a symmetry

4- Macrognathia and Micrognathia

5- Macrodontia and Microdontia

6- Oligodontia

7- Tooth shape variations (peg shaped lateral incisor)

8- Mandibular retrusion

9- Mandibular prognathism

10- Median diastema

11- Upper face height, nose height, bi-gonial breadth

12- Bimaxillary protrusion

hereditary ectodermal dysplasia

it is a sex linked anomaly transmitted by the unaffected female to their male offspring

hereditary ectodermal dysplasia manifestations

1. soft and thin dry skin with absence of sweat gland

2. frontal bossing and depressed nose

3. thick hypotonic lip

4. Oligodontia and complete anodontia

5. delayed eruption of teeth

6. maxilla and mandible are normal size but the present teeth are widely separated

7. the incisor may be peg shape or conical

A-3 Congenital

Deformities either heredity or non-heredity origin but exciting at birth

Cleft Palate

Lack of fusion of two palatal process to each other, various studies have shown that from one third to one half of all cleft palate children have familial history of this deformity.

Classification of clefts

Class I: soft palate cleft with possible notching of hard palate Class II: soft and hard palate but not alveolar ridge

Class III: complete unilateral lip jaw palate right or left

Class IV: complete bilateral lip jaw palate

Developed at birtg

As with non- cleft child, palatal, pharyngeal and perioral musculature is well developed to meet the demand of suckling, deglutition and mastication.

Cleft palate may lead to

Underdevelopment and retruded maxilla due to continuation of the oral cavity to nasal cavity that affect the pressure of air cells in the nose and maxillary sinus that stimulate growth of maxilla

Excessive intraoral clearance

Lingual tipped incisors

Cleft lip

The common cleft is the upper lip as a result of failure of globular process with maxillary process, this cleft lead to discontinuity of buccinator mechanism that lead to protrusion of anterior teeth

Cerebral palsy

a paralysis or lack of muscular coordination due to inter-cranial lesion

Torticollis: Wryneck

Foreshortening of the sternocleidomastoid muscle can cause profound changes in the bony morphology of cranium and face Facial a symmetry with dental malocclusion may be created if this problem not treated fairly early

Cleidocranial dysostosis charactierized by:

 Unilateral or bilateral complete or partial absence of the clavicle

 Delayed closure of cranial suture

 Maxillary retrusion of due to underdevelopment of maxilla

 Mandibular protrusion

 Retarded eruption of permanent teeth

 Retained deciduous teeth

 Supernumerary teeth are common

 Underdevelopment of paranasal sinuses

 Multi-impacted tooth

Mandibulo-facial dysostosis characterized by:

 Hypoplasia of facial bones especially zygomatic

 Marked hypoplasia of mandible

 bird face appearance

 Crowding and malposition of teeth

 Agenesis of malar and palatine bone

 Cleft palate

 Anomalies of external ear

Micrognathia may be affected:

 Mandible:

- severe retrusion of chin

- Steep mandibular plane

- Retrognathic profile

- Deficient chin button

 Maxilla:

- retruded middle third of face

- Deficient premaxilla

- Prognathic profile

Macrognathia

Abnormally large jaw, may be true due to the actual prognathism of jaw or relative due to underdevelopment of one jaw(maxilla) to the other

Micrognathia

Abnormal small jaws maxilla or mandible

Pierre Robin’s syndrome

characterized by Micrognathia, glossoptosis, cleft palate

 May be associated with other abnormalities such as atresia of ear and absence of TMJ

Cleft mandible

midline defect result from failure of union between left and right mandibular process

Tongue tie

is congenital condition caused by shortness or excessive anterior prolongation of Frenum linguae of the under surface of tongue.

Tongue tie effect

restriction of normal tongue function

Tongue tie cause

Constriction of maxillary arch

Difficulties in eating and possible

Periodontal disease in mandibular segment

Ankylglosum superior syndrome characterized by:

1. Tongue congenitally attached to the hard palate or maxillary alveolar ridge

2. Hypodontia

3. Microglossia

4. Anomalies of extremities

Microcephaly

 the brain development is retarded, and it is smaller than normal

 cranial dimensions are affected as well as the volume

 skull is small because of a lack of brain growth

 none of cranial sutures is closed, but since the brain does not grow

 the demand of sutures is absent

 in a number of chromosomal anomalies, microcephaly is present with varying degree of mental retardation

Hydrocephaly

Spinal fluid fills the cranium and causes the enlargement of cranial vaults.

Hydrocephaly

 The sutures of the cranial bones are separated and new bone formation tends to close the gap and the cranium may be double its volume

 Mental retardation may occur and it is not a necessary component because the pressure influences the vault rather than the brain

 cranial base not affected severely, and face may grow normally

 the jaws and occlusion of teeth are not directly involved

 Although the face looks larger in microcephaly and smaller in hydrocephaly is only relative to the size of the cranium

Craniostenosis

Sutures of the cranial vault may be fuse prior to the complete growth of brain depending on the sutures involved

Craniostenosis

 cranium is deformed in bizarre shapes turricephaly, scapho-cephly without necessarily causing brain damage, if however, many are fused the brain growth is confined as an inadequate space and pressure may build to such a point as to cause the brain to flow through the foramen magnum and brain growth in not enough to cause expansion.

 the weakest area in the anterior cranial base during five years of life is the ethmoid, so the increased intra-cranial pressure may deflect the ethmoid complex downward. This lowering the perpendicular lamina of the ethmoid, which influence the vertical position of the palate which in turn influence the vertical rotation of the mandible.

 the primary disturbance in the cranial base may secondarily influence the position of maxilla and mandible and thereby the facial proportion and dental occlusion.

Platybasia

 Occur as in case of mongolism, the angle between the anterior cranial base and posterior cranial base is obtuse angle in such degree to appear as straight line.

 This occur due to lack of development of occipital bone to grow downward and thus keeping the glenoid fossa high so the mandible is not rotated

 there is apparent open mouth that may be due to relatively large tongue in reduced oral cavity

Platybasia

may occur in case of hypothyroidism as there is a lack of development of sphenoid complex and this influence the midface When the sphenoid fails to grow upward, the posterior end of palate remains low relative to the condyle and tends to induce mandibular rotation downward and backward resulting in open bite.

Microglossia and aglossia

Rare condition characterized by small or rudimentary tongue, aglossia is very rare condition in which the tongue is completely absent

Microglossia and aglossia effect

difficulty in speech and eating, collapse of dental arch due to high action of buccinator

Macroglossia

Abnormal large tongue

Macroglossia effects

 spacing and flaring of the teeth

 tongue thrust

 abnormal tongue posture over the occlusal surface

 difficulty in eating, respiration, swallowing and speech

Macrochelia

Enlarged lower lip, flaccid and everted. It is often hypotonic, so that there is lack of pressure against mandibular teeth that result in protrusion

Hypertelorism

lateral position of eye due to widening of the bridge of the nose; incomplete development of maxillary process; incomplete development of mandibular rami

Nutritional deficiencies

o the mother suffering from lack of calcium, phosphorus, vitamin B C and D are able to have malformed children

o half of pregnant women who have congenitally malformed offspring exhibit the signs of anemia

o large varieties of congenital malformation have been found in newborn infant of mother with sever vitamin A deficiency

o Riboflavin deficiency may cause malformation, administration of Riboflavin to pregnant rat was fond to prevent some malformation

o acute folic acid deficiency may cause cleft palate, retarded growth and deformities of bones

Rubella

Acute viral infection usually occurs in epidemic form, maternal rubella of pregnant mother is considered as a possible cause of wide spread congenital malformation such as, blindness, deafness, and cardiovascular abnormalities. The most common dental effect is: enamel hypoplasia high caries index delayed eruption of teeth

Radiation

When pregnant mother exposed to radiation especially during the 1st six weeks of first trimester, the fetus may be damaged even with small dose,

Malformations of radiation are

Cleft palate, mongolism, microcephalus, hydrocephalus, deformed limb

Abnormal intrauterine position

interferes with symmetric development of face and jaws; asymmetry of the head may be caused by the pressure of the shoulder or extremities against the head

Chapple and Dawidson

determined the position of comfort of the fetus, they found that many infants with signs of pressure on mouth and jaws. This pressure is caused by one or both legs had been extended across the body bringing the foot against the side of the head forcing it against the opposite shoulder, thus causing facial a symmetry and deviation of the mandible

Pituitary gland

Small body in the base of brain and rest in hypophyseal fossa of sphenoid bone and considered as a master gland in the body

Hypo-pituitarism

pituitary dwarfism

Pituitary dwarfism leads to

=delayed eruption and shedding time of teeth as the growth of the body as general

= root of the teeth is shorter than normal

= dental arch is smaller than normal and cannot accommodate all teeth so that malocclusion is developed

= retarded osseous development of mandible than maxilla

= delayed apical closure

= hypothyroidism and diabetes insipidus

Hypo-pituitarism in adult

Simmond’s disease

Simmond’s disease

Occur after puberty due to infarction of pituitary gland

Simmond’s disease characteristics

= decrease sexual function

= loss of weight

= atrophic change in skin

= no specific dental features

Hyper-pituitarism before puberty

Gigantism

Gigantism characteristics

= root of teeth longer than normal

= upper part of body is shorter than normal

= spacing of teeth

= ossification of cartilaginous center is delayed and the fontanelle may persist to the time of adolescence

Hyper-pituitarism after puberty

Acromegaly

Acromegaly characteristics

= lips are thick and negroid

= tongue enlarged and show indentation

= teeth in mandible are tipped buccal or labial due to enlarged tongue (effect: spacing of teeth) = mandible is large size due to accelerated condylar growth, there is appositional and remodeling changes in all area of mandible

Thyroid Gland

Highly vascular bilateral lobed u shaped gland located on the trachea, it stimulates basal metabolic rate and control general metabolism by increase oxygen uptake by the tissues

Hypothyroidism: congenital type:

Cretinism

Cretinism

Failure of thyroid gland to produce sufficient hormone to meet the requirement of the body

Cretinism characteristics

= shortening of the base of skull

= mandible is under-developed; maxilla is over-developed (relative)

= retardation in normal rate of deposition of calcium in bones and in the development of tooth buds in the fetus

= defect facial height

= tongue enlarged and protruded which may result in malocclusion = delayed shedding of primary teeth = delayed eruption of permanent teeth

Hypothyroidism: childhood type (after 6 years and before puberty)

Juvenile Myxedema

Juvenile Myxedema characteristics

= enlarged tongue by edema fluid that protruded continuously and this lead to malocclusion

= delayed carpal and epiphyseal calcification

= delayed eruption rate of teeth and deciduous teeth are retained beyond the normal shedding time = irregularities of teeth arrangement and open bite may be present as a result of tongue enlargement

= osteoporosis and periodontal disease

=abnormal dental calcification and root resorption

= in adequate development of maxilla and depressed nasal bridge

Hypothyroidism: adult type

Myxedema

Myxedema characteristics

= edema of soft tissue of mouth, face, lips, and nose

= tongue enlarged and edematous and interfering with speech and occlusion = osteoporosis of bone

Note: Myxedematous swelling: is a probably an extra-vascular cellular accumulation of water and protein in the tissue

Hyperthyroidism

hyper-function of thyroid gland

Hyperthyroidism characteristics

= alveolar atrophy in advanced cases

= shedding of deciduous teeth is earlier than normal

= accelerated eruption of permanent teeth

= patient has facial expression of surprising or excitement; the patient is usually nervous and very uncooperative

Parathyroid gland

Four small glandular bodies embedded in the back of thyroid gland, regulate calcium and phosphorus metabolism

Hyper-parathyroidism

Von Recklinghausen’s disease of bone

Von Recklinghausen’s disease of bone characteristics

= High osteoclastic activity and withdrawal of calcium from the bony skeleton due to bone resorption, there is a sudden drifting of teeth that lead to spacing

= pathologic fracture may occur, lamina dura is absent

= Giant cell tumor or cystic lesion of the jaw are the first oral signs

= malocclusion occurs due to shifting and spacing of teeth

= in growing children, there may be marked interruption of teeth development

Hypo-parathyroidism

low calcium level below 10mg/100ml

Hypo-parathyroidism characteristics

= increase neuromuscular excitability ----- Tetany due to low Ca level

= aplasia or hypoplasia of teeth when the effect occur before the teeth were entirely formed = large pulp chamber and irregularities of occlusion

= delayed resorption of primary teeth roots

= delayed eruption of permanent teeth

The Adrenals

Paired organs situated near the upper surface of each kidney, consists of outer layer(cortex) and inner layer (Medulla)

Adrenocortical hyper-function

Decrease in protein body mass including the bony matrix to Ca deposited when the bone is formed that interfering with bone and tooth formation

Adrenocortical hyper-function manifestation

hermaphrodite; Early appear of sexual hair; Acceleration of tooth eruption and bone age

Cushing’s syndrome

= characterized by adrenocortical hyper-function

= obesity in upper part of body (neck-face) ---- moon face

= muscle weakness = there is premature epiphysis closure in children = high rate of physical growth

= accelerated eruption of the teeth

= osteoporosis of bone in adult

Hypothalamus

Make up the third ventricle of the brain, the hypothalamus provides neurogenic of pituitary gland which control the target glands as; thyroid, adrenal, and gonads or it may affect the target gland directly

The Thymus

Generally, it atrophied at the age of 14 to 16 years but with over growth of the thymus

= the general body growth is accelerated

= hypertrophy of the thymus gland may result in delayed eruption of deciduous teeth and poor tooth calcification

The Gonads

= imbalance of osteogenic hormones (excreted by the ovaries and testes) may result in gingivitis, gingival hyperplasia and periodontal disease

= burning sensation of tongue and decrease salivary secretion

= exert marked influence in somatic growth

= in hypo-function, the closure of the epiphysis is retarded

= in hyper-function, advanced puberty occurs with early closure of the epiphyseal growth center and retardation of body height

Precocious puberty

Occurs as a result of disturbance in hypothalamus, pituitary, adrenal, and Gonads

fibrous dysplasia

characterized by fibro-osseous formation and arise as:

= expansion and deformity of the jaws

= disturbance of eruption pattern of teeth because loss of normal support for teeth = mal-alignment, tipping or displacement of the teeth

cherubism

= symmetrical fibro-osseous lesions causing enlargement of the jaws

= alveolar ridges are wide lead to narrow palate to V shaped and tongue is forced backward, and this interfere with swallowing and breathing

= there is mal-alignment and malformation and irregularities of the teeth

Achondroplasia

The most common primary skeletal dysplasia. Disturbance in the endochondral bone formation which result the characteristic form of Dwarfism

four types of arthritis

1. infectious

2. rheumatoid

3. degenerative

4. traumatic