Aetiology of malocclusion, Extractions and Local factors Flashcards
what is malocclusion?
> an appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory
> malocclusion is not a disease but is regarded as a deviation from the normal
what are the categorical causes of malocclusion and malposition?
> skeletal pattern (genetically determined)
> Local factors
> soft tissues (pressure from lips, muscles, tongue)
> space deficiency and excess
what are the general factors causing of malocclusion?
> SKELETAL RELATIONSHIP
> TOOTH SIZE / ARCH SIZE DISPROPORTION
> soft tissues (macroglossia)
> genetic and developmental disorders
> TMJ trauma / growth abnormalities
> general factors tend to be things you can’t control for
what are the local factors causing malocclusion?
> EARLY LOSS / PROLONGED RETENTION OF
- DECIDUOUS TEETH
- ECTOPIC TEETH
> Absent teeth, supernumeraries
> Impaction, delayed eruption
> large Fraenum, local pathology
> Dental trauma
> local factors allow us to spot problems during development
how does skeletal relationship cause malocclusion?
> mostly genetic control
> jaw size has decreased since primitive populations
how does tooth and arch size cause malocclusion?
> relatively small arches may cause crowding
> larger teeth may cause crowding
- tooth size genetically controlled
- begg and aboriginal populations - found that softer diet led to smaller teeth
what are the common developmental and genetic disorders which cause malocclusion?
> Cleft Lip and Palate
- Surgical scarring: Class III, Crossbites
- local factors - supernumeraries / absent teeth
> Achondroplasia (he most common type of short limb (or disproportionately short stature)
> Acromegaly (abnormal growth of the hands, feet, and face, caused by overproduction of growth hormone by the pituitary gland.)
how does soft tissues cause malocclusion?
> Tongue posture and size
- anterior open bite
- cerebral palsy
> Tongue thrust not an aetiological factor
> Lip form and function
- bimaxillary proclination in Afro-Carribeans
what local factors involving the teeth are important in discovering the cause of maloclusion?
> Deciduous Teeth
- Early loss or prolonged retention of deciduous teeth
> Permanent: number of teeth
- Absent teeth (hypodontia)
- supernumeraries
- early loss (6s, 1s) - caries/ trauma
> Permanent: position of teeth
- ectopic canines (2% effect)
- impaction of 1st molars, or premolars
what might occur if the labial frenum is thickened?
> can lead to a midline diastema
what might happen if there is early loss of the Es due to caries?
> 6s move medially
> 4s and 5s unable to fit in the arch
> insufficient space = results in crowding + irregularities to the arch
how do you avoid problems with crowding caused by early loss of deciduous teeth?
> space maintainers
> best for of space maintenance is retaining the deciduous tooth
what are the effect of early loss of deciduous teeth?
> Tooth lost
- D, E = space loss as 1st permanent molars drift mesially (causes premolar crowding)
- C = incisor midline shift as permanent incisors drift into space
- A, B = minimal effect
> Age
- Effects more severe with earlier loss
> Degree of Crowding in the Arch
- more space loss with D or E loss if crowding present
- greater midline shift with C loss if perm incisors crowded
is prolonged retention of the deciduous teeth common?
> relatively common
what teeth tend to be affected by the prolonged retention of deciduous teeth?
> usually Es and Ds
> may delay permanent successor erupting
what may happen to retentive deciduous teeth?
> infraocclusion - (other teeth and bone continue to develop in the vertical dimension)
> May become “submerged” or “infraoccluded” due to ankylosis (root cementum attaching directly to the bone)
- tipping of adjacent teeth (first molars)
- almost all exfoliate naturally
- extract only if becoming completely submerged
what is the most common scene in the permanent dentition relating to malocclusion?
> hypodontia (congenital)
> 2-3%
what is severe hypodontia?
> 6 or more missing teeth excluding 8s
what do you call the complete absence of all permanent teeth?
> anodontia
excluding 3rd molars what are the most absent teeth seen in hypodontia cases?
> upper laterals
> 2nd premolars
> lower central
what is the treatment for hypodotia?
> space closure
> Open or maintain space then bridgework / implants / denture
> accept (e.g. lower 5s)
what is the treatment for hypodotia?
> space closure
> Open or maintain space then bridgework / implants / denture
> accept (e.g. lower 5s)
