Class III underbite with 2 impacted canines

Presentation

Chief complaint. " I want to fix my teeth."

Diagnosis. Mixed Dentition, Class I molars with anterior crossbite, severe upper and lower crowding, lingually inclined upper and lower incisors, and bilateral impacted, buccally displaced canines. Tooth #6 is positioned over the root of #7, with a hyperdivergent skeletal pattern.

Why I chose this approach

My goal was to correct the underbite, create space for both impacted canines, and guide them into the arch while protecting the adjacent incisor roots. The position of the canines made the sequence and direction of tooth movement especially important. I began with a palatal expander and reverse pull facemask to address the narrow upper arch and encourage forward movement of the maxilla while she was still growing. Correcting the inward inclination of the upper front teeth was also an important part of resolving her anterior crossbite. The upper right canine was positioned over the lateral incisor root, so I first moved the lateral incisors lingually to provide clearance. I then used the hooks on the expander to apply distal traction, directing the impacted canines away from the incisor roots before bringing them down into the arch. I chose braces to provide control over space opening, root positioning, and alignment as the canines were brought into place. Class III elastics helped support the bite correction and establish a positive overjet. Both canines were successfully brought into the arch, the crowding was resolved, and the anterior crossbite was corrected. Because she was still growing and showed a developing Class III pattern, continued monitoring remained an essential part of the plan.

Measurements

Cephalometric values before and after treatment
Measure	Norm	Pre	Post
SNA	82	79	79
SNB	80	78	77
ANB	2	1	2
Wits	0	-4	0
SN-MP	32	36	37
U1-SN	102	91	106
L1-MP	90	78	83
Overjet (mm)	2–3	-2	1
Overbite (mm)	2–3	2	1

Treatment

Objectives. Expand the maxilla and encourage maxillary advancement. Create adequate space for the impacted canines while protecting the lateral incisor roots. Retract the maxillary lateral incisors lingually to move them away from the canine eruption path, then apply distal and posterior traction to guide the canines into position. Procline the maxillary anterior teeth to correct the anterior crossbite. Level and align both arches, establish a Class I occlusion, and closely monitor future Class III growth.

Plan. Begin with a maxillary palatal expander and facemask therapy to correct the transverse deficiency and anterior crossbite. Use facemask hooks to assist with traction of the impacted canines. Initially, tie the maxillary lateral incisors to move them lingually and away from the canine roots, creating a safer eruption path. Once adequate clearance is achieved, begin distal traction of the impacted canines using the facemask hooks. Then band and bond from 7–7, open adequate space for the canines, and guide them into the arch. Continue Class III elastics as needed to maintain sagittal correction and establish a positive overjet.

Appliances and materials

Rapid Palatal Expander with face mask hooks
Reverse Pull Headgear
Metal Braces — 022 MBT
Class III elastics

Progress records

Cone Beam — Both canines are buccal and tooth #6s is mesial and buccal to #7 and #11 is also buccal

Outcome

Both canines were brought into the arch, a positive overjet was achieved, and Class III growth is being monitored.

Retention

Fixed U2-2 permanent retainer
Fixed L3-3 permanent retainer
Invisalign Vivera retainers to be worn at night

Both impacted canines were successfully brought into the arch, and a positive overjet was achieved. Both arches were leveled and aligned, crowding was resolved, anterior tooth inclinations were improved, and the midlines were coordinated. Third-molar extraction will be recommended. Because continued mandibular growth is evident, we will closely monitor the developing Class III pattern and support the correction with Class III elastics worn with the retainers as needed.