Phase I Treatment of Severe Crowding, Narrow Palate, and Posterior Crossbite

Presentation

Chief complaint. “I want to stop sucking my thumb and fix my overjet.”

Diagnosis. Seven-year-old female with a skeletal and dental Class II malocclusion characterized by mandibular retrognathia, a hyperdivergent growth pattern, approximately 8 mm overjet, severely proclined maxillary incisors, upright to retroclined mandibular incisors, a high and constricted maxillary palate, right posterior crossbite, severe maxillary and mandibular crowding, lingually blocked-out upper right lateral incisor, blocked-out lower left canine, and mandibular midline deviation to the left. History of persistent thumb-sucking habit.

Measurements

Cephalometric values before and after treatment
Measure	Norm	Pre	Post
SNA	82	81	80
SNB	80	73	74
ANB	2	8	6
Wits	0	4	0
SN-MP	32	39	39
U1-SN	102	110	100
L1-MP	90	88	98
Overjet (mm)	2–3	8	1
Overbite (mm)	2–3	1	2

Treatment

Objectives. Skeletally expand the maxilla to correct the posterior crossbite and constricted palate, create space to alleviate crowding and allow eruption/alignment of the lateral incisors, reduce the excessive overjet and maxillary incisor proclination, eliminate the thumb-sucking habit, and establish a Class I dental relationship.

Plan. Begin Phase I treatment with a rapid palatal expander (RPE) to achieve skeletal maxillary expansion and correct the posterior crossbite. Follow with Invisalign First to level and align the arches, create and maintain space for erupting teeth, reduce the overjet, and use elastics as needed to improve the sagittal relationship toward Class I.

Appliances and materials

Rapid Palatal Expander — Large expander to help stop finger habit
Invisalign First — with Class II elastics

Progress records

Outcome

Successfully eliminated the thumb-sucking habit, expanded the maxillary arch, corrected the posterior crossbite, achieved a Class I relationship, reduced the overjet, and created adequate space for eruption of the permanent teeth.

Retention

Essix retainers with palatal coverage to be worn full time for 6 months then nighttime only