First, Happy New Year to you and your family.
Definition of impacted canine
A canine is considered impacted if it is unerupted after three quarters root development (Litsas and Acar, 2011), or the contralateral tooth has erupted for at least 6 months with complete root formation or if the canine position is intraosseous at or beyond CS5 or 2 years after adolescent growth spurt or 6 month after its root completion (Lindauer et al., 1992).
Prevalence and Incidence
· 1.7 to 2% among Caucasian (Ericson and Kurol, 1986 and 1988).
· 61% of impacted canines are palatally impacted canines (PIC) (Stivaros and Mandall, 2000),
· 34% of impacted canines are impacted within the line of the arch (Stivaros and Mandall, 2000)
· 4.5% of impacted canines are buccally impacted canines (BIC) (Stivaros and Mandall, 2000).
· Unilateral impactions of canines are 4 times more frequent than bilateral impactions while female to male ratio is 7:3 (Mossey et al., 1994).
Diagnostic procedures and investigations:
a) Clinical signs:
· Absence of a normal labial canine bulge or presence of a bulge in the palatal region of the canine tooth (Kettle, 1957)
· Delayed eruption (Bishara, 1992)
· Retention of the deciduous canine (Mittal et al., 2017),
· Loss of vitality and increased mobility of the permanent maxillary lateral, central incisor or deciduous canine (Mittal et al., 2017, Husain et al., 2012).
· Abnormal position of the lateral incisor (this subject was not very well investigated)
b) Radiographic assessment using one or combination of the following imaging: OPG, periapical radiograph, lateral cephalometric radiograph, upper standard occlusal radiograph, CBCT or medical CT scans
Complication
· No complication
·It may erupt in a labial / lingual mal-position
· If the C lost, then, mesial migration of neighbouring teeth and loss of arch length might occur
· Internal or external root resorption of adjacent teeth
· Dentigerous cyst formation and infection with referred pain
· Ankylosis
· Deformation in the shape of the root of the canine (this subject was not very well investigated)
Update:
American Journal of Orthodontic and Dentofacial Orthopaedic published a CBCT-based study in their December 2020 issue to answer subjects which were not very well investigated (highlighted previously in red) .
The paper's title is: Impaction of maxillary canines and its effect on the position of adjacent teeth and canine development: A cone-beam computed tomography study.
A team from Italy, Canada and Israel undertook this study which was led by Dr Dekel.
CBCT scans from 34 adolescents who initial presented with unilateral maxillary impacted (21 with PIC and 13 with BIC) were retrospectively collected and analysed.
The study showed that:
PIC forced the roots of the adjacent lateral incisors to move labially by 5° and their crown to rotate mesiobuccally by 17.1°
BIC forced the roots of the adjacent lateral incisors to move palatally by 5° and their crown to rotate mesiobuccally by 18°
The authors also concluded that untreated impacted teeth are shorter than average and their roots were hooked.
In summary:
The axial rotation of the lateral incisor is not a sensitive diagnostic clinical sign to discriminate between BIC and PIC, however, the labio-palatal changes in the position of the root of the adjacent lateral incisors is useful diagnostic sign. Finally, early intervention is crucial to prevent developmental defect of the impacted tooth