This is the Bite that is most effective when treated at 7-8 years of age- Class III Underbites

Presentation

Chief complaint. " I want to fix my underbite"

Diagnosis. Patient presents with a concave facial profile and a skeletal Class III pattern characterized by maxillary retrognathia with mild mandibular prognathism. Intraorally, she presents with: Bilateral Class III molar and canine relationships Generalized maxillary crossbite, including bilateral posterior crossbite and anterior crossbite -2 mm negative overjet (underbite) 1 mm (10%) overbite Constricted, narrow maxillary arch with a high palatal vault Extruded mandibular incisors Severely retroclined mandibular incisors, consistent with significant dentoalveolar compensation for the underlying skeletal Class III discrepancy Mildly retroclined maxillary incisors Overall, the patient demonstrates a skeletal Class III malocclusion with significant transverse maxillary deficiency and dentoalveolar compensation, including severe retroclination of the lower incisors.

Why I chose this approach

In my practice, early correction of an underbite associated with a deficient upper jaw is one of the most valuable uses of Phase I treatment. My goal was to address both the narrow palate and the upper jaw’s backward position while she was still young. I chose a palatal expander to correct the bilateral posterior crossbite and reverse pull facemask therapy to encourage forward movement of the upper jaw. At age 7, I wanted to take advantage of her early growth to improve the relationship between the jaws. Her lower incisors were already severely tipped inward to compensate for the underbite. This made addressing the jaw relationship particularly important rather than relying on further tipping of the lower teeth. I then used limited braces to improve anterior alignment and incisor position while maintaining space for the developing permanent teeth. We corrected the anterior and posterior crossbites and established positive overjet and overbite. I intentionally finished with some additional overjet to provide allowance for potential future mandibular growth. Continued growth monitoring remains an essential part of her care. Early treatment improved her bite and jaw relationship, but future lower jaw growth will determine how well the correction holds and whether additional treatment is needed.

Measurements

Cephalometric values before and after treatment
Measure	Norm	Pre	Post
SNA	82	81	83
SNB	80	84	83
ANB	2	-3	0
Wits	0	-8	-2
SN-MP	32	38	40
U1-SN	102	95	116
L1-MP	90	76	80
Overjet (mm)	2–3	-2	3
Overbite (mm)	2–3	1	2

Treatment

Objectives. Expand the maxilla to correct the transverse deficiency and bilateral posterior crossbite. Protract the maxilla to improve the skeletal Class III relationship and anterior crossbite. Level and align the anterior teeth and improve incisor position. Create and maintain adequate space for eruption of the permanent canines and posterior teeth. Improve the anterior overjet and overbite toward a positive, stable relationship. Monitor mandibular growth closely as the patient continues to grow and reassess the Class III skeletal pattern over time.

Plan. Begin with rapid palatal expansion to address the transverse maxillary deficiency. The expander will be activated twice daily for approximately two weeks, with progress monitored clinically. Following expansion, initiate reverse-pull headgear therapy to protract the maxilla. The patient should wear the reverse-pull headgear for a minimum of 12 hours each day, preferably throughout the evening and overnight, until adequate maxillary advancement is achieved and a positive overjet and overbite are established. Once the skeletal and transverse correction is underway, bond the upper and lower anterior teeth from canine to canine to level and align the anterior segments. Prior to debonding, obtain progress radiographs to evaluate root position, eruption, and available space. Reposition brackets as needed to optimize alignment and root angulation. If additional space is required, continue space development to facilitate eruption of the permanent canines and posterior teeth. Mandibular growth and the developing Class III relationship will continue to be monitored throughout treatment and during subsequent growth.

Outcome

Treatment successfully achieved the planned skeletal and dental correction. The bilateral posterior crossbite and anterior crossbite were corrected. The maxilla was advanced anteriorly, improving the skeletal Class III relationship. ANB improved by approximately 1 degree. The mandible and occlusal plane rotated counterclockwise, contributing to improvement of the Class III relationship and an increase in the mandibular plane angle. A positive overjet was intentionally overcorrected to provide some allowance for potential future mandibular growth. The anterior teeth were aligned and the overall occlusion significantly improved. Overall, we achieved the intended transverse, sagittal, and dental treatment goals, with continued growth monitoring recommended as the patient matures.

Retention

Upper and lower Hawley Retainer We will switch to Essix with Class III elastics slits to be worn at night in the future her lower jaw starts growing ahead of the upper jaw