How far is the root apex of a unilateral impacted canine from the root apices' arch form?
BACKGROUND
The purpose of this study was to determine the arch form of the root apices of normally erupting teeth and then determine the differences in the location of the apex of impacted canines relative to normally erupting canines. In addition, we sought to determine whether the labiopalatal position of the impacted canines influences the position of the apices.


METHODS
The study included 21 patients with unerupted canines that subsequently had a normal eruption, 21 patients with palatally impacted canines, 27 patients with labially impacted canines, and 17 patients with midalveolus impacted canines. Images were obtained using cone beam computed tomography, and the x, y, and z coordinates of the root apices were determined using Ondemand3D software (Cybermed Co., Seoul, Korea). Two-dimensional coordinates were converted from acquired 3-dimensional coordinates via projection on a palatal plane, and the Procrustes method was used to process the converted 2-dimensional coordinates and to draw the arch forms of the root apices. Finally, we measured the extent of root apex deviation from the arch forms of the root apices.


RESULTS
Normally erupting canines showed that even though calcifications may be immature, their positions were aligned with a normal arch form. The root apices of the impacted canines were an average of 6.572 mm away from the root apices' arch form, whereas those of the contralateral nonimpacted canines were an average distance of 2.221 mm away, a statistically significant difference. The palatally impacted canines' root apices distribution tended toward the first premolar root apices.


CONCLUSIONS
Incompletely calcified, unerupted teeth with a subsequent normal eruption showed a normal arch form of the root apices. The root apices of impacted canines were farther from the arch forms than were the nonimpacted canines. Also, the root apices of impacted canines in the palatal area showed distributions different from those of the other impacted canine groups.
Department of Orthodontics, Institute of Translational Dental Sciences, Pusan National University Dental Hospital, Yangsan, South Korea.
Sung-Hun
SH
Kim
Department of Orthodontics, Institute of Translational Dental Sciences, Pusan National University Dental Hospital, Yangsan, South Korea.
You-Min
YM
Kim
Department of Dentistry, School of Dentistry, Pusan National University, Busan, South Korea.
Sewoong
S
Oh
Department of Orthodontics, Institute of Translational Dental Sciences, Pusan National University Dental Hospital, Yangsan, South Korea.
Seong-Sik
SS
Kim
Department of Orthodontics, Institute of Translational Dental Sciences, Pusan National University Dental Hospital, Yangsan, South Korea.
Soo-Byung
SB
Park
Department of Orthodontics, Institute of Translational Dental Sciences, Pusan National University Dental Hospital, Yangsan, South Korea.
Woo-Sung
WS
Son
Department of Orthodontics, Institute of Translational Dental Sciences, Pusan National University Dental Hospital, Yangsan, South Korea; Department of Orthodontics, Dental Research Institute, Pusan National University Dental Hospital, Yangsan, and Biomedical Research Institute, Pusan National University Hospital, Busan, South Korea. Electronic address: kimyongil@pusan.ac.kr.
Yong-Il
YI
Kim
D000293:Adolescent; D002648:Child; D003481:Cuspid / Q000033:anatomy & histology / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D009811:Odontometry; D012189:Retrospective Studies; D019227:Tooth Apex / Q000033:anatomy & histology / Q000473:pathology*; D014095:Tooth, Impacted / Q000473:pathology*; D055815:Young Adult