Impacted teeth, it’s in the timing

orthodontics In summary

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.

Timing

Role of timing to the impacted tooth, the adjacent teeth and alveolar and skeletal growth.

Implications of timing on impacted teeth:

1. Eruptive potential

2. Root development

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.

• Principle:

• 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)

• Interceptive treatment

• Removal of obstruction, spontaneous eruption 36-75%

• Removal of obstruction + space creation spontaneous eruption 82-89%

(Sun et al AJODO 2006)

Root development

• 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

• Shorter root

• 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)