Approximation and contact of the maxillary central incisor roots with the incisive canal after maximum retraction with temporary anchorage devices_ Report of 2 patients

494 Chung, Choi, and Kim
Fig 1. CBCT images of the incisive canal. The incisive canal (arrows) is surrounded by cortical bone.
The axial section represents the apical third of the incisor roots. Notice that the width of the incisive canal
is larger than the interroot distance between the central incisors in the axial view.
mandibular canal and the inferior alveolar neurovascular
bundle during orthodontic tooth movement have also
been reported 9-11 and in rare incidences were associated
with temporary paresthesia of the lower lip. 9,10
The following 2 case reports illustrate the contact
and approximation of the maxillary central incisor roots
to the incisive canal after maximum retraction with temporary
anchorage devices.
CASE REPORTS
Patient 1
Patient 1 was a 19-year-old woman with chief complaints
of lip prominence and protrusion. The intraoral
photographs and cephalograms indicated a skeletal
Class II malocclusion with a protrusive profile. A panoramic
radiograph showed no gross abnormalities. She
had no notable medical history (Fig 2).
The overall goals of treatment were to improve the
protrusive profile and to obtain a Class I occlusion with
ideal overjet and overbite. Four first premolars were extracted,
and orthodontic treatment was initiated using
0.022-in slot Roth prescription self-ligating brackets
(Clippy-C; Tomy International, Tokyo, Japan). In addition,
4 miniscrews (Ortholution, Gyeonggi-do, Korea),
one per quadrant, were inserted between the second
premolars and the first molars to reinforce anchorage
during space closure. We used 150-g nickel-titanium
coil springs (Tomy International) and elastomeric modules
for anterior retraction via en-masse sliding mechanics.
Since the patient lived abroad, she was able
to visit the clinic only once every 4 months on average
during her vacations.
The duration of the treatment was 24 months. After
treatment, her profile was improved with a Class I occlusion
and ideal overjet and overbite, and the dental
midline was in accordance to the facial midline. Fixed retainers
were bonded, and removable retainers were provided
for use at night. The patient was fully satisfied with
the overall outcome. The cephalometric superimposition
indicated absolute retraction of the maxillary incisors
through bodily movement and controlled tipping of
the mandibular incisors along with intrusion (Table I).
However, the posttreatment radiographs indicated moderate
to severe apical root resorption, especially in the
maxillary right central incisor, compared with the neighboring
teeth. Interestingly, according to the periapical
radiograph, the incisive canal, which was identified as
a radiolucent tube-like structure surrounded by a thin
radiopaque margin between the central incisor roots,
was curved to the right and not to the left, making contact
with the right central incisor root and not the left
central incisor (Figs 3-5).
Considering the large amounts of anterior retraction
and root movement, and the severity of root resorption
at the right central incisor, we performed a cone-beam
computed tomography (CBCT) scan (Pax-Zenith3D;
Vatech, Seoul, Korea) to further evaluate the
3-dimensional (3D) structural changes, including the
amount of alveolar bone surrounding the maxillary incisors.
In general, the palatal surface of the maxillary teeth
was covered with a thin layer of cortical bone. However,
to our surprise, the mesiopalatal surface of the maxillary
right central incisor root apex was in contact with the
incisive canal (Fig 4, A and B), which was associated
with severe root resorption (Fig 4, C and D), whereas
September 2015 Vol 148 Issue 3
American Journal of Orthodontics and Dentofacial Orthopedics