8 - Class I Malocclusion Flashcards
Class I Malocclusion
State 3 features of Class I malocclusion:
A Class 1 malocclusion is when the lower incisors occlude on or directly beneath the cingulum, plateau of the upper incisors (British Standards Institute)
- The upper inclination is average, and the overjet is within the normal range of 2-4mm.
- The AP relationship is usually class I, and there is a discrepancy within the arches and/or in transverse/vertical relationships between the jaws or teeth
Class I malocclusion - refers to incisor relationship only ???
Aetiology of class I malocclusion :
- Skeletal
- Soft tissue
- Dental
Skeletal class I
Class I- SNA is ahead on SNB slightly which is a normal relationship of the maxilla to the mandible
Dentoalvaolar compensation - incisors tip to attempt a class I incisor relationship despite altered skeletal pattern
- Skeletal II – Proclination of lower incisors
- Skeletal II – Retroclincation of lower incisors
Crossbites are common in class I malocclusion because of crowding is common
In the vertical dimension, the overbite is either normal or slightly increased
– Not possible to be severe overbite in class I
Soft tissues class I
Bimaxillary proclination:
Teeth lie in the zone of balance, which is an imaginary zone of the lower incisor region where the forces on teeth both inside and outside the mouth are equal
In bimaxillary proclinication there’s an alteration of that balance of forces
- If force from tongue is too large, then incisors procline.
- If force from lips is too much, then the incisors retrocline
Afro-Caribbean patients have increased incidence of bimaxillary Proclination
Dental
Class I malocclusion
Name the dental causes of class I malocclusion (6)
Dental factors are the main aetiological influences in Class I malocclusion.
Tooth size/arch length discrepancy, leading to crowding or spacing within the arches.
• Displaced teeth
• Impacted teeth
• Anomalies in tooth size, number and form
• Supernumerary Teeth - Conical, Tuberculate , Supplemental, Odontome
• Early loss of primary teeth eg loss of Es lead to crowding of 5s, loss of leeway space - difference of mesiodistal width of C, D, E compared to their successors -3,4,5s. Maxilla - leeway space = 1.5mm, Mandible - leeway space= 2.5mm
Displaced tooth
Displaced teeth -commonly upper canines and second premolars
Management :
Mild displacement -extract primary tooth
Severe displacement - surgical exposure and bonding of gold chain
Very displaced - surgical removal of tooth
To attempt to prevent impacted teeth what is done
Annual palpation for maxillary canine
Should palpate buccal sulcus from age of 9
If not present buccal check palatal
Investigate if:
- absence of buccal bulge
- asymmetry of bulge
- palatal bulge
Management
- interceptive treatment - eg extraction of upper C -> can correct canine palatally impacted
- surgical exposure and bonding of gold chain
- very displaced - surgical removal
Extra on supernumerary tooth
Conical
– Small peg shaped tooth.
- Usually upper anterior
- Conical supernumerary found in the midline is called a Mesiodens
- Most common type – 70%
- Rarely prevent eruption of incisors
Usually detected when taking radiographs before orthodontic treatment
- Management:
- Decide whether the supernumerary needs to be extracted prior to ortho treatment.
- Space closure, Midline? Causing a diastema?
Tuberculate – Barrel shaped tooth
- Late forming
- Doesn’t tend to have roots.
- Very rarely erupts.
- Palatal aspect of upper 1s.
- Leads to impaction of upper 1s.
- If preventing eruption of adult tooth, then surgical removal of the tuberculate.
- This allows eruption of central.
- Sometimes you need to place a gold chain on the unerupted central and use ortho to
bring it down.
Supplemental – Duplicate tooth within the normal serios.
- Found at the end of the series.
- Distal to the lateral incisors
- Distal the 5s
- Distal to the terminal molar.
- Results in crowding.
- Managements
- Extract the tooth with the least favourable crown or root position.
Odontome
- Complex – Mass of poorly organised dental tissues.
- Usually in the premolar/molar region
- or compound – Mass of tooth like structure (denticles) usually in the anterior portion of the maxilla
- Rarer, not seen frequently
Impacted teeth
How do we describe impacted teeth?
When describing an impacted tooth:
- Describe the direction
- Disto-angular
- Mesio-angular
- Horizontal
- Vertical
How do we know if canines are ectopic?
Describe impaction:
How would we manage?
With impacted canines, if you can see that the tips of the canines are over the lateral roots, then you know that the canines are ectopic and out of position. It is important to check for resorption of roots. It is very common that ectopic canines cause resorption of the laterals and sometimes the central (if very ectopic)
Impaction:
- disto angularly impacted tooth
- impacted 5 with an enlarged follicular space
Management - pt been bonded with fixed appliance and tooth surgically exposed and gold chain has been bonded
Orthodontic wires used to extrude the tooth and bring into the line of the arch
What can you see in this radiograph?
Impacted upper canines - (bilateral impaction)
Mesioangular impaction
Slightly larger follicular spaces
Both Cs retained - tip of canine is overlying lateral roots -> very clear sign the teeth are ectopic (out of position)
Must check for resorption
Describe this clinical photograph
Surgical exposure of an imapcted canine in the palate and bonding of gold chain - to bring tooth into the line of the arch
What can you notice in this clinical photograph ?
Supernumerary teeth - supplemental lateral
MUST COUNT TEETH
Crowding
Define crowding
State causes
Crowding
Define 3 categories of crowding
When we look at IOTN and crowding, we use the letter D, which stands for contact point displacement
We look at the worst contact point displacement in the patients mouth, and we measure in mm to give a score for their crowding
What type of crowding is this?
Severe
Almost exclusion of the upper canines
LL canine is excluded from lower arch
Mild rotations of anterior teeth
RULE:
Rotations anteriorly -> due to crowding
Rotations posteriorly -> due to spacing
What is done for moderate-severe crowding ?
Planing extractions depends on
Prognosis -> extract poor prognosis over sound
Extraction of 4s OR 5s?
- 4s -> need more space at front of the mouth - more space anteriorly to relieve anterior crowding or if you wanted to reduce an increased overjet in class II div I pt
Anchorage balance when you extract 4s favours more movement at the front of the mouth so allows more space at front of the mouth
Whereas extract 5 Anchorage balance favours forward movement of the 6 - eats up space and less space anteriorly
May consider taking out 6- if pt has MIH and hypoplastic enamel severely on their 6s
What is done to relieve mild crowding?
Head gear used for molar distalisation - can only carry out if molar relationship is less than or equal to half a unit class II - not done much anymore
Interproximal stripping - can be done by handheld strip, bur, disc
Arch expansion - most common. Fixed appliance made from Ni Ti
For understanding what is anchorage
Anchorage = source of resistance to forces generated by an orthodontic appliance
Balance between applied force and available space
If its described as Anchorage demanding - means you need more space to treat that case
More anchorage demanding:
- if you need more teeth moved
- Multi rooted posterior teeth compared to single rooted teeth
- bodily movement compared to tipping movement
Spacing
Aetiology of spacing
Hypodontia
1 what is it
2 Aetiology
3 Most commonly affected teeth?
4 Dental anomalies associated with hypodontia include:
5 Main treatment options are:
6 Factors to consider in treatment planning:
1- The developmental absence of one or more teeth, excluding third molars
2- Aetiology is multifactorial, with both genetic and environmental factors implicated
3- Most commonly absent in Caucasians (approx 2%):
- Lower second premolar
- Upper lateral incisor
- Upper second premolar
4-
- Impacted upper canines
- Delayed dental development
- Microdontia (localized or generalized)
5 -
- Either maintain/redistribute existing spacing for restorative replacement
- Or carry out orthodontic space closure
6-
• Severity of the hypodontia- number and site of missing teeth
• Underlying malocclusion and degree of crowding
• Colour and form of adjacent teeth
• Pt’s wishes
Median Diastema
1 what is it?
2 What is the relevance in a mixed dentition
3 what may it be associated with?
4 Treatment
1- A space between the upper central incisors
2- Presence of a diastema is a normal finding in the mixed dentition and usually closes on eruption of the upper canines - normal in mixed dentition
3- May be associated with a persistent low fraenal attachment
4
1. Prior to any treatment, take a radiograph to check there is no underlying supernumerary tooth
2. Fixed appliances can be used to close the spacing, however permanent retention is required to avoid relapse.
3. In certain cases, a frenectomy may be indicated
Bimaxillary proclination
1 What is it?
2 Which demographic is it seeen more commonly in?
3 is Correction easy - why/why not:
1- Both upper and lower incisors are proclined
2- Seen more commonly in certain racial groups eg Afro-Caribbeans
3- Correction is difficult, as both upper and lower incisors need to be retracted and this is prone to relaps
Case 1
Class I incisors
Class I molar relationship - angles classification
