Aetiology of malocclusion - local causes Flashcards
What are the dental causes of malocclusion?
Tooth/tissue ratio
Number of teeth
Form and position of teeth
What are the local causes of malocclusion
Habits
Labial frenum
Pathology
What is meant by the tooth/tissue ratio?
Imbalance in the ratio of tooth a jaw size will produce crowding or spacing of the dentition
What are the possible aetiological factors in crowding?
Independent genetic control of teeth and jaws
Evolution
Out breeding
Diet
What is the % of crowding in the UK?
60-70%
What are the possible effects of crowding on the dentition?
Overlapping and displacement
Impaction
Mesial movement of teeth
What is generalised spacing due to?
Hypodontia
Small teeth/well developed arches
What are is the congenital causes of absence of teeth?
Anodontia = all teeth missing Oligodontia = several teeth missing Hypodontia = Few teeth missing
What could the missing teeth aetiology be linked to?
Sex-linked recessive condition of ectodermal dysplasia
What is ectodermal dysplasia
Lack of sweat glands
Sebaceous glands
and hair follicles
Some degree of anodontia or malformed teeth
How can cleft lip and palate patients have missing teeth?
absence of teeth to the surgery carrie dout in the region of developiing tooth germs
What are the most common missing teeth
Lower 3rd molars 13.6% Upper 3rd molars 11% Lower second premolars 3% Upper lateral incisors 1.8% Upper second premolars 1.1% Lower incisor 0.3%
What are the effects of developmental hypodontia?
Form of teeth: smaller or malformed
Position of teeth: affected by the absence of teeth
Growth
How can developmental hypodintia affect growth?
May affect the alveolar bone and increase the freewau space but not the rest of the mandible
What can cause aquired loss of teeth?
Premature loss of deciduous teeth
Loss of permanent teeth
Retention of deciduous teeth
Delayed eruption of permanent teeth
What are supplemental teeth? What can they result in?
These have a normal form and usually occur at the end of the series
Increase crowding potential of the dentition and are treated by removal of a suitable tooth
What are the 2 types of midline supernumerary?
Conical
Tuberculate
What is a conical (mesiodens)
Develops early - root formation coincides with the upper central incisor may erupt usually displaces otherteeth Does not delay eruption May be inverted
when would you not remove the supernumerary tooth?
If it is very high
inverted
removal would damage other teeth
What is a tuberculate?
Develops later than the upper central incisor
Does not usually erupt
Delays the eruption of the upper central incisor
Other teeth may move into the space
Where does a tuberculate develop?
on the palatal ascpect of the upper central incisor
What happens once have removed the tuberculate?
the other teeth often remain high when erupted and require orthodontic treatment
What is it important to do before dealing with patients with supernumerary teeth?
Carry out a full orthodontic assessment
Space must be created for the permanent teeth to erupt into and any associated malocclusion must be dealt with
What are the different shape and size of teeth?
Gemination
Fusion
Macrodontia
Microdontia
What does the equilibrium theory tell us about thimb/digit/dummy sucking?
The force duration is more important than magnitude
What force needs to be applied to affect the teeth significantly>
6 hours/day
How many infants suck digits? What ages does this happen?
> 50% between 6 months and 2 years
Stopped by 4 years
What are the long-term effects of digit sucking on the permanent dentition?
Flared, spaced upper incisors
Lingually inclined lower incisors (could be proclined)
Reduced overbite (or anterior open bite)
Narrowed upper arch
Habit does not affect the molar relationship
How do you treat the problems associated with digit sucking ?
If the habit stops early, the overjet may reduce within 1 year, but the tongue may have adapted to the reduced overbite and prevent this closing
What is the labial fraenum?
Remnant of the tecto-labial bands
Precedes (before) tooth development and transeptal fibres
What is the labial faenum attached to at birth?
Papilla, migrates with eruption of the deciduous and permanent molars
Where does the labial faenum attach?
To the mucosa over the labial plate but in some cases attaches to the crest of the alveolar bone before tooth eruption
The type of attachment is determined at 7 weeks IUL, when there is separation of the lip and alveolous by an invaginating lip furrow band
What does the histology of the labial fraebum show?
Not muscle
Consists of vascularised collagen fibres
interrupts the transeptal fibres
What is the effect of the labial fraenum?
Midline spacing, associated with large fresh fraenum
Space closure will relapse
How do you prevent relapse of space closure due to labial fraenum?
Fraenectomy - not until upper laterals and canines are present (90% of diastemas close spontaneously)
How do you diagnose the labial fraenum attachement?
Blanching on palatal mucosa when faenum put under tension
V-shaped notch on radiograph
What pathology is associated with malocclusion?
Rare and usally self-evident Fracture Cyst Neoplasm Inflammatory condition
