Invisalign Palatal Expander for Severe Crowding in a 6-Year-Old | Phase I Orthodontic Treatment

This 6-year-old patient presented with severe crowding in the lower arch and moderate crowding in the upper arch, with insufficient space for the developing permanent teeth and blocked-out upper lateral incisors.

Patient

Child (10 and under), male

Classification

Class I

Active treatment

13 months

Published

September 8, 2026

Presentation

Chief complaint. "I have a tooth growing in on the inside."

Diagnosis. This 6-year-old patient presented with a skeletal Class I relationship and a convex facial profile. Clinical examination demonstrated significant space deficiency in both arches, with a particularly narrow and constricted maxillary arch and high palatal vault. Key diagnostic findings included: Skeletal Class I jaw relationship Convex facial profile Constricted maxillary arch with a high, narrow palatal vault Moderate to severe maxillary crowding Insufficient space for eruption of the maxillary permanent canines, which were blocked out of the arch Proclined maxillary incisors Significant mandibular crowding Lower dental midline shifted significantly to the right Blocked-out lower right lateral incisor Thick mandibular lingual frenum Severe deep overbite Approximately 2 mm of overjet Overall, the patient demonstrated a significant arch-length and space deficiency during the early mixed dentition, with inadequate room for the developing permanent teeth. The constricted maxillary arch and high palatal vault were important considerations in planning early expansion and arch development.

Why I chose this approach

My goal was to create space for the developing permanent teeth and address the narrow upper arch early. Although he was only 6, he already had significant crowding, with teeth erupting outside the intended arch form. I chose Phase I treatment because the space deficiency was already affecting eruption. I selected the Invisalign Palatal Expander to widen his constricted upper arch and create additional room for the upper lateral incisors and developing canines. He was nervous about having an expander, and this option did not require a parent to turn a key inside his mouth. Instead, expansion progressed through a series of removable expanders. This made the approach less intimidating for him and eliminated the need for his parents to perform screw activations at home. The severe lower crowding also required attention. I used Invisalign First to develop the lower dental arch, create room for the blocked out lower right lateral incisor, and improve coordination with the expanded upper arch. The lower treatment focused on dental arch development and tooth positioning. After expansion, holding trays and retainers helped preserve the space while the permanent teeth continued to erupt. This phased approach improved arch form and available space while accommodating his concerns about treatment. The purpose of early treatment was to provide a better foundation for eruption and future alignment. We will continue monitoring his growth and permanent teeth to determine whether Phase II treatment is needed.

Cephalometric values before and after treatment
Measure	Norm	Pre	Post
SNA	82	77	79
SNB	80	75	73
ANB	2	2	3
Wits	0	0	1
SN-MP	32	30	31
U1-SN	102	114	112
L1-MP	90	104	101
Overjet (mm)	2–3	4	2
Overbite (mm)	2–3	2	2

Measure

Norm

Pre

Post

SNA

SNB

ANB

Wits

SN-MP

U1-SN

102

114

112

L1-MP

104

101

Overjet (mm)

2–3

Overbite (mm)

2–3

Treatment

Objectives. The primary goal of Phase I treatment was to create adequate space for the developing permanent teeth and improve arch development during growth. Our objectives were to: Expand the maxillary arch and palate to address the transverse constriction and high palatal vault. Create adequate space for the upper lateral incisors and developing permanent canines to erupt into the arch. Develop and broaden the lower arch form to address the severe mandibular crowding. Create space for the blocked-out lower right lateral incisor to erupt into a more favorable position. Improve coordination between the upper and lower arches. Allow the remaining permanent teeth to erupt while preserving the space created during Phase I treatment. Monitor growth and dental development and re-evaluate the patient for Phase II treatment once the permanent dentition has erupted.

Plan. Treatment began with the Invisalign Palatal Expander, with a new expander changed approximately every two days to gradually widen the maxillary arch. After active expansion, the patient will wear holding trays for approximately 3–4 months to maintain the expansion. During this period, the lower arch will be scanned and treated with Invisalign First to develop the mandibular arch form, create additional space, and improve coordination between the upper and lower arches. The patient will then be monitored as the permanent teeth erupt, with continued Invisalign First treatment as needed to guide eruption and alignment. Once the permanent dentition is established, growth, bite, alignment, and remaining space needs will be reassessed to determine the timing and need for Phase II comprehensive orthodontic treatment.

Appliances and materials

Invisalign Palatal Expander

Invisalign First

Progress records

Invisalign Palatal Expander in the mouth

Outcome

We successfully expanded and developed both the upper and lower arches, creating additional space for the remaining permanent teeth to erupt into more favorable positions. Phase I treatment significantly improved the available space and arch form, providing a better foundation for the developing permanent dentition and future Phase II treatment, if needed.

Retention

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