Developmental Disturbance Of Jaw Flashcards
What is agnathia?
Agnathia is a lethal anomaly characterised by hypoplasia or absence of the mandible with abnormally positioned ears having an autosomal recessive mode of inheritance. -Shafer
Common type of agnathia of maxilla?
Only a portion of jaw is missing.
In the case of maxilla,
- one maxillary process
- premaxilla
Common type of agnathia of mandible?
Partial absence of mandible
- only the condyle
- entire ramus
- bilateral agenesis of the condyle and of the rami also has been reported.
How is the deformation of the ear related to agnathia ?
In case of unilateral absence of the mandibular ramus, it is not unusual for the ear to be deformed or absence as well.
It is probably due to failure of migration of neural crest mesenchyme into the maxillary prominence at the fourth to fifth week of gestation.
Occurrence of agnathia?
The prevalence is unknown and less than 10 cased are described.
Prognosis of agnathia?
The prognosis is very poor and considered to be lethal.
What is micrognathia?
Micrognathia literally means a small jaw, and either the maxilla or the mandible may be affected.
Types of micrognathia?
- True micrognathia
2. Pseudo micrognathia
What is pseudo micrognathia?
Many cases of apparent/pseudo micrognathia are not due to an abnormally small jaw in terms of absolute size, but rather to an abnormal positioning or an abnorma relation of one jaw to the other or to the skull, which produce the illusion of micrognathia.
Classification of true micrognathia?
True micrognathia may be classified as
- congenital
- acquired
Etiology of congenital micrognathia?
The etiology is unknown, although in many instances it is associated with other congenital abnormalities, including congenital heart disease and the Pierre Robin syndrome.
Described the gross of micrognathia of maxilla?
Micrognathia of the maxilla frequently occurs due to deficiency in the premaxillary area, and patient with this deformity appear to have the middle third of the face retracted.
Cause and affect of maxilary micrognathia?
Although it has been suggested that mouth-breathing is a cause of maxillary micrognathia, it is more likely that the micrognathia may be one of the predisposing factors in mouth breathing, owing to the associated maldevelopment of the nasal and nasopharyngeal structures.
Reasons of pseudo mandibular micrognathia?
- posterior positioning of the mandible with regard to the skull
- to a steep mandibular angle
Cause of true mandibular micrognathia?
Agenesis of the condyles
Reasons of acquired type of micrognathia?
-results from disturbance in the area of the temporomandibular joint
Eg-ankylosis of the joint due to trauma, or infection of the mastoid, of the middle ear, or of the joint itself, ondylar ankylosis
Clinical appearance of mandibular micrognathia?
- severe retrusion of the chin
- a steep mandibular angle
- a deficient chin button
Causes of congenital condition of micrognathia?
- pierre Robin syndrome
- Cate- Manzke syndrome
- Cerebrocostomandibular syndrome
- Cornelia de Lange syndrome
- miller-dieter syndrome
- nagar acrobatically dysostosis
- Schwartz-Jamel-Abergele syndrome
- van boaters-hozay syndrome