Aetiology of Malocclusion 2 Flashcards
what is the aetiology of malocclusion
• Skeletal
○ Class III
○ High FMPA
• Dental
○ Missing teeth
• Soft tissue
○ Lip trap
• Other
○ Habits
define what a local cause of malocclusion is
a localised problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion
what are the causes of local malocclusion
- Variation in tooth number
- Variation in tooth size or form
- Abnormalities of tooth position
- Local abnormalities of soft tissues
- Local pathology
what causes variation in tooth number
- Supernumerary teeth (extra)
- Hypodontia (developmentally absent teeth)
• Variation of timings ie at this particular time the tooth number is not correct:
○ Retained primary teeth
○ Early loss of primary teeth
○ Unscheduled loss of permanent teeth
what is a supernumerary tooth
A tooth or tooth-like entity which is additional to the normal series
where is the most common place to find supernumerary teeth
Most common in anterior maxilla
are supernumerary teeth found more in males or females
Males > females
what is the prevalence of supernumerary teeth
1% primary dentition
2% permanent dentition
what are the types of supernumerary teeth
- Conical
- Tuberculate
- Supplemental
- Odontome
what are conical supernumerary teeth
○ Small, peg shaped ○ Close to midline = mesiodens ○ May erupt (extract) ○ Usually 1 or 2 in number ○ Tend not to prevent eruption but may displace adjacent teeth [Ie usually do not cause a problem in the eruption of permanent teeth]
what are tuberculate supernumerary teeth
○ Tend not to erupt ○ Paired ○ Barrel-shaped ○ Usually extracted ○ One of the main causes of failure of eruption of permanent upper incisors
what are supplemental supernumerary teeth
○ Extra teeth of normal morphology
§ Ie same form / shape as the tooth they are copying
§ can cause crowding and upset the centreline and can impede the eruption of other teeth
○ Most often upper laterals or lower incisors
○ Can be 3rd premolars or 4th molars
○ Often extract
§ Decision based on form and position
§ Look at the form of the tooth and the copy and decide which one is in the better position and keep that tooth whilst extracting the other one
what are odontome supernumerary teeth
○ Compound
§ Discreet denticles
○ Complex
§ Disorganised mass of dentine, pulp and enamel
what is hypodontia
Developmental absence of one or more teeth
Can have mild, moderate and severe hypodontia depending on how many teeth are missing
does hypodontia affect males or females more
Females > males 3:2
where is it common to have hypodontia
Commonly upper laterals (2s) > second premolars (5s)
what are retained primary teeth
A disruption in the sequence of eruption
A difference of more than 6 months between the shedding of contra-lateral teeth
why do primary teeth not exfoliate / why are they retained
○ Absent successor
§ Ie nothing to resorb it’s roots and push it out
§ = hypodontia
○ Ectopic successor or dilacerated
§ So the permanent teeth is in the mouth but not in the normal place
§ Not following normal path of eruption / has been impacted
○ Infra-occluded (ankylosed) primary molars
§ Ankylosis is when the roots can be fused to the bone
○ Dentally delayed in terms of development
§ Just natural for them to lose their primary teeth later than the normal age
○ Pathology / supernumerary
what are the options I f there is an absent successor
• Either maintain primary tooth as long as possible
○ If good prognosis
○ This maintains the space in the mouth
• Or extract, deciduous tooth early to encourage spontaneous space closure in crowded cases
Early orthodontic referral for advice
what are infra-occluded primary molars
“submerged”
Process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
Temporary ankylosis
how can infra-occluded primary molars be graded
Can be graded between slight, moderate and severe
○ slight: between occlusal and inter proximal contact, less than 2mm in the occlusion as the marginal ridge is not level on either side but it is above the contact point
○ Moderate: within occluso-gingival marrgins of inter proximal contact
○ Severe: below inter proximal contact point
[severe infra-occlusion with the deciduous molar falling well below the contact points]
once at moderate-severe you would consider referral to a specialist to consider extraction of the deciduous infra-occluded tooth / teeth
why do infra-occluded primary molars look like they are sinking
The reason why they look like they are sinking is because the infra-occluded teeth actually stay where they are whereas the rest of the teeth and bone around them continue to develop and grow
So as everything else moves this tooth just stays where it is
how are infra-occluded primary molars managed
• Permanent successor present
○ Usually self correct so keep under review
○ Consider extraction if:
§ Contact points are going subgingival
§ Root formation of the successor is near completion
• Permanent successor absent
○ Depends on potential of crowding:
§ Retain if in good condition (onlay) ~ Want to build it up if it has good long term prognosis and healthy roots
§ Or extract and plan space management ~ Either replace with prosthetic tooth or orthodontically close the space
what causes the early loss of primary teeth
○ Trauma
○ Periapical pathology
○ Caries [Most common reason]
○ Resorption by successor
what does early loss of primary teeth cause
Localisation of crowding
what does localisation of crowding because of early loss of primary teeth depend on
○ Which tooth is extracted / lost
○ When the tooth is extracted
○ Patient’s inherent crowding
what does balancing extraction mean
○ By extraction of a tooth from the opposite side of the same arch
§ Creates a balance eg extract a tooth from the right and the left of the lower arch
○ Designed to minimise midline shift
what is meant by compensating extraction
○ By extraction of a tooth from the opposing arch of the same side
○ Designed to minimise maintain occlusal relationship
§ Ie minimise future problems like centreline shifts or molar relationship discrepancies
what happens if there is early loss of primary incisors
Very little impact
No compensating or balancing extractions
what happens if there is early loss of primary canines
○ Unilateral loss in crowded arch, can give centreline shift
○ Will get some mesial drift of buccal segments
○ Consider balancing extraction
Eg if upper left deciduous canine is lost you would consider extracting the upper right deciduous canine to keep the centreline
what happens if there is early loss of primary molars
○ More space loss with Es > Ds ○ More space loss in upper > lower ○ 6s drift mesially and steal 5 space ○ Tend not to balance or compensate ○ Would look to space maintain ○ But if unsure better to get a second opinion
what factors influence the impact of the loss of 6s
§ Age at loss
§ Crowding
§ Malocclusion
when is ideal for the 6s to be lost if they need to be
• Upper arch
○ Less important
• Lower arch
○ Ideally at the time of bi-furcation development in 7s
§ If L7s erupted (late) ~ Often poor space closure
§ If too early ~ Distal drift of 5s
when will extraction of 6s give the best results in the lower arch
○ If you extract in a spaced arch → may have spaces left
○ If you extract in an aligned arch →may have spaces left
○ If you extract in a crowded arch → best results likely
what are fundamentals of the unscheduled loss of 6s
• Compensation
○ If U6 has to go ~ no compensation
○ If L6 has to go ~ often compensation
§ Refer for advice before making decision
• Balancing
○ Not if spaced or well aligned
Consider if premolar crowding
what happens if there is unscheduled loss of a central incisor
○ In first instance maintain space = re implant the avulsed tooth
§ Or providing a partial denture
○ Plan how to deal with space
§ Prosthesis?
○ If the space is not maintained then centreline shift can occur and space loss which then makes it much more difficult for the orthodontist to create the space and to create good symmetry
what are the variations in tooth size or form
- Too large = macrodontia
- Too small = microdontia
- Abnormal form
what is macrodontia
Tooth / teeth larger than average
can be localised or generalised
what are the problems with macrodontia
○ Crowding
○ Asymmetry
○ Aesthetics
what is microdontia
Tooth / teeth smaller than average
can be localised or generalised
what does microdontia lead to
Leads to spacing
Linked to hypodontia
what are abnormal forms of teeth
- Peg shaped laterals
- Dens in dente
- Geminated / fused teeth
- Talon cusps
- Dilaceration
- Accessory cusps and ridges
what teeth are commonly ectopic
3rd molars (8s) Upper canines (3s) FPM (6s) Upper centrals (1s)
what is the prevalence of ectopic canines
1-3% of population
what are ectopic canines associated with
Associated with small or absent upper laterals
with regards to ectopic canines what needs to be checked for
Check for palpable buccal canine bulge from 9 years onwards
Further investigation or refer if in doubt
what should you look for in the clinical assessment of ectopic canines
○ Visualisation / palpation of any obvious bumps of 3
§ Look for the canine bulge
○ Inclination of 2
§ can be distally inclined and this would mean that the canine is pushing against the roots of this tooth
○ Mobility of c or 2
§ May mean there is root resorption occurring
○ Colour of c or 2
Due to loss of vitality due to resorption
what should you look for in the radiographic assessment of ectopic canines
○ 2 radiographs needed to localised position
§ Usually OPT and anterior occlusal
○ Parallax technique (vertical)
§ Can take 2 periapicals or other radiographs to give you horizontal parallax
§ Horizontal parallax is supposed to be more accurate however if you have an OPT and upper occlusal then you have a larger view in which you can see any pathology and the rest of the teeth
§ 3 P’s
□ Presence
□ Position
□ Pathology
what are the management options for ectopic canines
○ Prevention
○ Extraction C to encourage improvement in position of 3
§ Interceptive extractions
○ Retain 3 and observe
§ Accept its position
§ Monitor
§ Consider this if you have a 2-4 contact (ie lateral incisor and premolar contact) and the ectopic canine is very ectopic and you are not planning on doing any orthodontic treatment or the patient declines any treatment
○ Surgical exposure and orthodontic alignment
○ Surgical extraction
§ Of the impacted tooth ie the canine itself
○ Autotransplantion
§ Rarely done
§ Surgical procedure where you remove the tooth from where it is and then place it into its new position
how can we prevent ectopic canines
- Appropriate monitoring from age 9 onwards
* Clinical assessment ~ Symmetry
where are ectopic FPM most commonly found
More commonly upper arch
when are ectopic FPM reversible
Reversible before age 8
why can ectopic FPM be a caries risk
If left and not monitored can become a caries risk due to plaque and food trapping
what are ectopic FPM signs on
○ Crowding
§ If the upper arch is hypoplastic then it doesn’t give the tooth enough room to erupt normally
○ Mesial path of eruption
how can ectopic FPM be managed
○ Separator
§ In between distal of e and mesial of 6 to try and push apart the teeth to create more space
§ Works well
○ Attempt distalise 6
§ Orthodontically have an appliance on and have a spring to push the 6 distally ~ allows it to erupt
○ Extract e
§ But if radiograph shows severe impaction or the e is resorbed / poor prognosis then extract
what do you need to check for with ectopic upper centrals
○ Sequence
○ Symmetry
why can upper centrals be ectopic
○ Supernumerary
○ Dilacerated (trauma)
what is the possible treatment for ectopic upper centrals
○ Surgical exposure
§ Removal of supernumerary if present and bond gold chain
§ Give it time to erupt but you need to maintain space
○ Make space
○ Above 9 years: § Orthodontic traction □ Align it § Bonded retainer □ Keep it in place
what is transposition
interchange in the position of 2 teeth
how can transposition be classified
○ True
§ Both the crowns and the roots have switched
○ Pseudo / false
§ Just the crowns have switched but the root apices are in the correct position
where does transposition most commonly occur
○ Upper canines and first premolar
○ Lower canines and incisors
what are the treatment options for transposition
○ Accept
○ Extract
§ One of the teeth then close the teeth
○ (correct)
§ Do this when it is a mild pseudo transposition
§ Not really done when it is a true transposition
what causes local abnormalities of soft tissues
- Digit sucking
- Frenum
- Tongue thrust
what is another name for digit sucking
Non Nutritional Sucking Habit
what happens with Non Nutritional (Digit) Sucking Habit
- Proclined upper incisors
- Retroclined lower incisors
- Anterior Open Bite
- Unilateral Posterior Crossbite
what happens when the thumb is sucked
the thumb being sucked creates negative pressure within the mouth and pushes the upper incisors forwards causing them to become proclined
○ Pushes the lower incisors into the mouth towards the tongue
○ Creates a gap between the incisors
The negative pressure causes a constriction / prevents further transverse growth of the maxilla which then causes unilateral posterior crossbites
what may the labial frenum cause
Labial Frenum may cause median diastema
when would you do a frenectomy
If the diastema persists and its greater than 3mm and it is a concern to the patient then you can do a frenectomy and close the space orthodontically but would require a permanent life-long bonded retainer
But we wouldn’t do anything until the permanent canines have erupted into their positions which can then cause spontaneous closure of the diastema and the frenum regresses
what is a tongue thrust
When patient puts their tongue between their upper and lower teeth
what can the tongue thrust cause
Can cause AOB and splay the teeth and cause spacing
what are endogenous reasons for tongue thrust
Medical issues such as Down’s Syndrome or macroglossia
what are habit / exogenous reasons for tongue thrust
Need to stop the habit before treatment is complete otherwise it will cause relapse
what local pathology can cause malocclusion
- Caries
- Cysts
- Tumours
