2 - Development of the Dentition Flashcards
Eg pt has unerupted, delayed eruption of upper canine - could cause resorption of u central or lateral incisor
Or
Growth modification for pt who has severe underlying skeletal problem - if referred at correct time, at start of pubertal growth spurt - then can do this.
Concept of ideal vs normal occlusion
What is ideal occlusion?
Ideal occlusion = Andrew’s six keys:
- Correct molar relationship - (anteriorposteriorly class 1 and molars interdigitate well in buccal segments)
- Correct crown angulation - mesial/distal tilt
- Correct crown inclination - labiolingual inclination
- No rotations
- Tight contacts
- Flat occlusal plane - so not deep overbite or anterior open bite
What is normal occlusion?
What is malocclusion
Development of deciduous dentition
1- when do deciduous teeth develop from and until
2- calcification begins when?
3- when is root formation complete after eruption?
4- when do maxillary and mandibular A-E erupt?
Ideal positions for Deciduous dentition :
(4)
What 3 things should we have at the completion of deciduous dentition?
Deciduous incisor relationship
Explain feature of lower gum pad at birth
Is overbite normal at first and what happens over the next few years?
At 5 years what occurs?
What variations often occur on ‘ideal’ deciduous incisor relationship
Overbite and overjet often depend on degree of thumb sucking
anterior open bite on left image
increased overjet on right image
Spacing between incisors - deciduous dentition
1- what is the increase in intercanine width during time deciduous incisors present?
2- If deciduous incisors are not spaced what happens to permanent dentition:
3- If crowded deciduous incisors what happens to permanent dentition:
4- How much spacing is needed in the lower arch to ensure permanent incisors are aligned?
1- 1-2mm increase in intercanine width during time deciduous incisors present
2- if deciduous incisors not spaced -> crowded permanent incisors
3- if crowded deciduous incisors -> severely crowded permanent incisors
4- in lower arch only if > 6mm spacing of deciduous incisors will permanent incisors be aligned
End to end E relationship
1- Ideal E relationship
2- Variations of E relationship
1- Es should be vertically on top of each other
2-
Class I Es -> class I 6s or class III 6s
Class II Es -> class II 6s
Class III Es -> very rare as mandible lags behind maxilla at this stage
Problems arising during development of deciduous dentition
Abnormalities in tooth tissue ratio leads to
Abnormalities in number of teeth could lead to: (3)
Abnormalities in tooth form or position leads to:
What can occur due to thumb sucking?
Also leads to increase in overjet and anterior open bite
Incisor retrusion leads to:
Posterior crossbite could be caused by?
What 2 problem could we detect in deciduous dentition
Development of the permanent dentition
1- starts at what age?
2- calcification dates
3- root formation:
4- what age do mandibular and maxillary 1-7 erupt?
If disruption eg illness at the time of the calcification may reflect in teeth being affected eg hypoplasia -if at birth could affect 6s as they calcify at this time
Development of permanent dentition can be divided into
3 stages
Stage 1 of permanent dentition eruption
Left DPT - lower 2 not erupted so around 6-6.5
Right DPT - all 4 lower incisors so around 7
How is there space for permanent incisors that replace deciduous incisors?
(Space relationships in replacement of incisors )
(3)
- Deciduous incisors are spaced
- Permanent incisors are proclined (1-2mm space)
- Increase in intercanine width:
- slightly more in maxilla (3mm) than in mandible (2·5mm)
- slightly more in male than female
• in maxilla -> just enough space
• in mandible -> 1·5mms short of space
- transitory lower incisor crowding age 8 to 9
Problems at stage I
- Impact of 6 under E
- mesial drift of 6 if E lost prematurely
- failure of eruption of incisors - supernumeraries or retained deciduous molar
- diastema and distal tilt to upper lateral incisor (NORMAL to have midline diastema at this stage)
- incisor crowding
- missing lower incisor or upper lateral incisor or abnormal form of upper incisor
- loss of permanent teeth - upper 1 or 6s
- premature loss of deciduous teeth
- incisor relationship altered by thumb sucking (posterior crossbite can also be caused by thumb sucking)
- anterior crossbite
Can also assess for anteroposterior correction
What can you see
What can you see?
Supernumerary between incisors in clinical photo
Supernumerary in midline between incisors in x ray - mesiodens
Bottom clinical photo - incisor rotated
Supernumerary can cause failure of eruption of permanent incisors or displacement
What can you see?
If more than 6 month delay need to investigate and x ray
Also history of trauma - if trauma to the A then could damage the upper incisor permanent and cause dilaceration
What can you see
What can you see?
Incisor crowding
What can you see
Abnormal shape
What can you see?
What can you see?
What can you see?
Stage 2 of permanent dentition eruption
Space requirements in eruption of premolars
(Space relationship in eruption of premolars)
Deciduous teeth are larger than permanent teeth - leading to leeway space - greater in mandible than maxilla
Allows Change over from E to E vertical relationship where they are on top of each other to class I buccal segment relationship- where mesiobucal of U6 is in buccal groove of L6
E relationship
How many mm of movement of lower 6 needed to give class I?
Class I relationship occurs due to (2)
Some mandibular growth forwards along with leeway space -> permanent molar relationship of class I
Problems at stage 2
change of sequence of eruption and signs of disturbance in normal development:
• Delay in eruption of upper 3
- asymmetries of eruption of right and left sides
- if variation is over 6 months take Xray to check cause
• 5 excluded lingually, palatally, or impacted
• Retained deciduous teeth, missing 5’s, submerging E’s
Extra - Should palpate upper buccal sulcus for maxillary canine - should be able to palpate buccal and distal to lateral incisor
What can you see?
Radiograph - can detect position of upper canines using upper standard occlusal and DPT - can use parallax method to determine position of the canines - to see if normal, ectopic or palatally displaced, or at risk of resorbing lateral or central incisor
What can you see?
Radiograph - can detect position of upper canines using upper standard occlusal and DPT - can use parallax method to determine position of the canines - to see if normal, ectopic or palatally displaced, or at risk of resorbing lateral or central incisor
If pt is 13 definitely delay in eruption and need to take radiograph to check and refer for ortho assessment if there’s a problem
Left pic - palatally displaced canine, undergone Interceptive treatment with surgical exposure, gold chain on attachment
Unerupted canine uses upper lateral incisor root as guidance to erupt into correct position - so if pt missing upper laterals then even more important to monitor eruption as canines likely to displace palatally - as shown in bottom right pic
What’s this?
LRE - lower level of occlusal plane, become ankylosed - may become submerged - need to refer for treatment
Infraoccluded
What occurs in stage 2
Treatment planning for most malocclusions - space analysis space regain, space maintain or extractions
(Once 7-7 erupted)
Stage 3
Problems at stage 3
NICE guidelines for third molar extraction (not usually an ortho problem, but oral surgery)
