occlusion and malocclusion Flashcards
what is the ideal occlusion?
anatomically perfect arrangement of teeth- RARE
what is normal occlusion?
acceptable variation of ideal occlusion
-aligned teeth
-no crowding
-class I incisor relationship- normal overjet/overbite
-class I molar relationship
what is a normal overjet?
upper incisors are 2-4mm ahead of lowers
what is a normal overbite?
upper incisors cover lowers by about 30%
what is a class I molar relationship?
-mesiobuccal cusp of the upper 1st permanent molar occludes with the buccal groove of the lower 1st permanent molar
define malocclusion?
-an irregularity in the occlusion beyond the accepted range of normal
do all malocclusions require tx?
no
define class I malocclusion?
the overjet and overbite are normal- molars are in the class I position.
define class II malocclusion
the overjet is increased- upper incisors are even further forward that the normal accepted range.
define class III malocclusion
the overjet is decreased meaning the lower incisors are ahead of the upper incisors
what is a cause of malocclusion?
genetics
how do genetics affect malocclusion?
genetics can affect:
-skeletal pattern
-size of jaw and teeth
-can result in syndromes such as cleft lip and palate
describe the class I skeletal pattern?
normal skeletal pattern where the maxilla is 2-4 mm ahead of the mandible
describe the class II skeletal pattern?
when the maxilla is >4mm ahead of the mandible- may be an associated class II malocclusion
describe class III skeletal patterns?
mandible lies <2mm behind the maxilla and may be infront of maxillanum. - may be associated with class III occlusion
how is the skeletal pattern affected in the transverse plane?
look directly at patient in front:
-may be asymmetry between two halves of faces
-may be discrepancy in face height- the lower third of the face may be increased or decreased in comparison to the rest of the face.
if a patient inherits large teeth and small jaws what are they likely to have?
crowding
if a patient inherits small teeth and large jaws what are they likely to have?
spacing
what are other causes of malocclusion?
environment
how can the environment cause malocclusion, give examples.
-soft tissues
-habits e.g thumb sucking
-pathology e.g tumour
-trauma
-local factors
what is an example of soft tissues causing malocclusion?
-lip incompetence- where the upper and lower lip do not meet at rest
what is an example of habits causing malocclusion?
e.g digit sucking- where thumb puts pressure on teeth cause them to move apart- causing an anterior open bite
how can pathology affect malocclusion?
-tumours are slow growing and can exert a force on the teeth causing misalignment
how can trauma affect malocclusion?
-trauma can exert an immediate force on the tooth-moving it out of alignment- e.g intrusive luxation
how do local factors affect malocclusion and give examples of local factors?
-they tend to cause malocclusion in one area
-supernumerary
-hypodontia
-fraenum
-retained deciduous teeth
-early loss of deciduous teeth
how do supernumeraries affect malocclusion?
-may prevent eruption of other teeth
-may cause crowding
how does hypodontia affect malocclusion?
-spacing
-fixed with brace, dentures, implants
how does the frenum affect malocclusion?
-labial frenum may cause a space between upper central incisors
how do retained deciduous teeth affect malocclusion?
-prevents permanent tooth fro erupting in correct position
how does early loss of deciduous teeth affect malocclusion?
-may cause permanent teeth to drift and erupt in incorrect position= loss of space and crowding when other teeth erupt
what does IOTN stand for?
index of orthodontic treatment needs
how does the IOTN assess malocclusion?
-measures the severity of malocclusion based on affects of malocclusion on dental health and aesthetics of the pt.
how is dhc of iotn graded?
given score- 1-5
4/5-require treatment- greatest effect on dental health.
based on looking at overjet, missing teeth, crowding, overbite, cross bite etc
how is the aesthetic component graded ?
effects of malocclusion on aesthetics
-based on graded photos to score the teeth
-1=most attractive
-10-least attractive
