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)
how common is missing upper laterals?
> 2-3%
what are missing upper lateral incisors associated with?
Associated with ectopic canines and small contralateral lateral incisors
what is the treatment for missing upper laterals?
> space closure (crowding, Class II cases, 3s acceptable)
> bridgework (no crowding, 3s poor colour)
> usually need fixed appliances
how common is absent second premolars?
> common - 2%
> can appear on radiographs as late as age 8
what is the treatment for an absent second premolar?
> space closure (extract deciduous early)
> bridgework
> use space to treat crowding
> accept and retain Es
> Prognosis of Es uncertain, unusual to last beyond age 30
are absent lower centrals common?
> very rare
> A’s usually retained
what is the treatment for absent lower centrals?
> close space
> bridgework
what is the incidence of supernumerary teeth?
> 1-2%
> 80% are in the anterior maxilla (OPG/ Anterior occlusal to find)
what is the classification of supernumerary teeth
> Morphology = Coniform and Tuberculate
> Position = Mesiodens, Supplemental (looks like another tooth), Paramolar
what are the clinical effect of supernumerary teeth?
> causes delayed eruption of teeth (e.g. Upper centrals)
> may erupt (mesiodens), causing crowding
> midline diastema (mesiodens)
what is the treatment of supernumerary?
> No treatment
> Extract
> Exposure and alignment of teeth with delayed eruption (Upper incisors)
> However, more than 70% of unerupted upper central incisors will erupt following removal of a supernumerary tooth
what are the common impacted teeth?
> first permanent molars
> premolars
> third molars
what is the incidence of impacted permanent first molars?
> 3-4%
where is the impacted 6s most commonly found?
> maxilla
what is the treatment options for impacted 6s?
> two thirds will correct spontaneously, although unlikely to improve after age 8 years.
> extraction of E
> Simple URA to disimpact
what causes the impaction of premolars?
> early loss of Es
what is the more common impacted premolar?
> second premolar
what is the treatment for impacted premolars?
> Extract 4 to allow eruption of 5
> Extract 7 and distalise 6 to create space
> Extract 5 (surgical)
> No treatment and review regularly
what is the incidence of ectopic canines?
> 2%
what can happen to a upper labial frenum?
> it can become abnormally thick
what are abnormally thick upper labial frenums associated with?
> midline diastema
what is the treatment for an abnormally thick labial frenum?
> wait until upper canines erupted before treating
> fraenectomy during or after space closure
what is the common causes for early loss of permanent teeth?
> 6s = caries
> 1s = trauma
why is the early loss of permanent 1st molars a problem?
> Residual space
> overeruption of opposing first molar
> space is difficult to use with appliances for treating anterior crowding or overjet
what is the ideal age for spontaneous closure of early loss of permanent 1st molars?
> 8-9 years
does the upper or lower spaces caused by early loss of 6s close better?
> upper spaces close better
what happens to unopposed upper 6s?
> they over erupt
what happens to the midline in unilateral loss of 6s?
> midline shift is minimal so not to worry
what is the management of carious 1st molars?
> Extraction best age 8-9, if 6s are of poor prognosis at this age then consider extraction
> Later extraction –> tipping
> Consider extraction of upper with lower
would you extract 3rd molars due to crowding ?
> no - very weak association with lower incisor trauma
> lower incisor crowding in 70% of patients
what are the tx options if upper perm incisors are lost or unsaveable?
> Maintain space with prosthesis
> Close space orthodontically and crown lateral poor gingival margin & canine colour
> however try to save eg RCT, reimplant
what are the biggest risk of early loss of perm upper incisors?
> 8-10
> trauma
> > boys
> class 2 div 1 = poor lower lip coverage (incompetent) no protection
what are common examples of abnormal tooth forms?
> dilaceration of perm upper incisors
> peg shaped upper lateral incisors
what is the dilaceration of permanent upper incisors?
> root bent away from the crown
> trauma to deciduous predecessor, age 4-5
> causes delayed or non-eruption
> tx - orthodontic alignment sometimes possible
> a lot less common than supernumerary - use radiograph to differentiate
what is peg shaped upper lateral incisors often associated with?
> strong association with ectopic canines
> other lateral may be absent
