Impacted teeth, it’s in the timing.
Join me for a summary looking at impacted teeth and key components of timing which affect not only the success of alignment, but also root formation. This podcast also explores the occurrence of asymmetries of both dental and facial due to impacted teeth, and what can be done about it. This podcast is a summary of the AAO lecture by Stella Chaushu and Adrian Becker.
Role of timing to the impacted tooth, the adjacent teeth and alveolar and skeletal growth.
Implications of timing on impacted teeth:
1/ Eruptive potential and timing
Interceptive treatment Ideal time for spontaneous eruption is ½ to 2/3 of final root length.
Orthodontic traction: Ideal time for active (orthodontic traction) eruption is 2/3 to ¾ final root length.
Peak of eruptive potential is at 2/3 to ¾ of final root length
Root completed within 2.5 to 3 yrs post eruption
Timing of impacted maxillary canine interceptive treatment
Dental age of 9-10 years
Interceptive treatment includes: extraction C, D, distalisation molars, RME
Prognosis of treatment of impacted canines is uncertain and reduces with age.
Ideal early adolescence
Timing of impacted maxillary incisor interceptive treatment
Before age of eruption 7-8 years
Likely spontaneous eruption, but risk of damage to permanent incisor in surgery
After age of eruption > 8 years
Spontaneous eruption not predictable, likely require active (orthodontic traction)
Removal of obstruction, spontaneous eruption 36-75%
Removal of obstruction + space creation spontaneous eruption 82-89%
(Sun et al AJODO 2006)
Impacted incisor due to obstruction – ideal time =7-8 yrs
Dilacerated upper incisors – ideal time – at ½ root or less = 6-7 yrs, as removal of root proximity to the anatomical barrier can reduce the dilaceration of the forming root
Timing of impacted premolar interceptive treatment
What to do when premolar root formation has not occurred in adolescent patient
If apex is open = root formation occurring
Timing of obstruction management
Removal: As early as possible
Orthodontic traction: Delay until bony infil, otherwise loss of gingivla and alveolar supoort
2/ Root development
Canine root development
Hooked apex 3-4 times more likely with impacted canines
impacted incisor 2.3mm shorter root Sun 2016, Impacted canine 2.3mm shorter roo Cao 2021
Total volume unaffected (length + hook)
Prevalence and severity of dilaceration increase with age until apex closed
Dilacerated root respond to traction/
Yes but increased treatment difficulty and duration , example of 2 years
Arrested root development
Can arrested root development be reversed?
If root abuts with an anatomical barrier. Such as nasal floor, it is the cause of the arrested development
Orthodontic traction and movement away from the barrier = continued root development
Early exposure and orthodontic traction
Implication of impacted tooth and asymmetry
Impacted tooth can affect alveolar and skeletal growth
Cases with asymmetry significantly higher in impacted group.
Asymmetry index 27% Vs 3.4%
Chin asymmetry 52% Vs 14%
Occlusal cant 38% Vs 10%
Timing of treatment, if delayed = occlusal cant increased with age.
After treatment, asymmetry can persist = treat as early as possible to limit asymmetry (managing impaction will not correct asymmetry)