Understanding Crowding in the Early Mixed Dentition

Marlon A. Moldez
Jul 26
3 min read

Part 3: When Is Phase 1 Treatment Recommended for Crowding?

Parts 1 and 2 explained why crowding develops and how it is evaluated. Part 3 examines when treatment during the early mixed dentition may be appropriate. The recommendation depends on the diagnosis, available space, eruption pattern, dental and facial development, and expected benefit of early treatment.

When Phase 1 Orthodontic Treatment Is Recommended

Phase 1 treatment may be recommended when a developmental problem contributing to crowding can be addressed during growth. Rather than attempting to straighten every tooth, treatment focuses on factors affecting the space and eruption pathways for the permanent teeth.

Jaw Development

Growth may provide an opportunity to manage a selected skeletal problem contributing to crowding.

Treatment depends on the jaw relationship, growth pattern, facial relationships, and expected response. It is not indicated for every child with crowded teeth.

Arch Development

A narrow upper arch may be associated with crowding, a crossbite, or a functional jaw shift. Expansion may be considered when the diagnosis confirms a transverse discrepancy. It is not recommended solely to avoid extracting permanent teeth.

Space Management

Early loss of a primary tooth may allow neighbouring teeth to move into the space needed for its permanent successor. When indicated, treatment may preserve or regain space, remove an obstruction, or open an eruption pathway for a permanent canine or premolar. The approach depends on the amount and location of space loss and the positions of the developing teeth.

How Does the Severity of Crowding Affect the Recommendation?

Mild-to-Moderate Crowding

Mild-to-moderate incisor crowding may change as primary teeth are lost, leeway space becomes available, and the dental arches develop. Observation is often appropriate while eruption continues. Treatment may be considered when space has been lost, an eruption pathway is obstructed, or limited alignment would address a functional, periodontal, or psychosocial concern. Extraction of permanent teeth solely for mild-to-moderate incisor crowding is generally not considered during the early mixed dentition.

Severe Crowding

Severe incisor crowding may indicate that there is insufficient space for the permanent canines to erupt.

If a maxillary transverse discrepancy is also present, maxillary expansion may be considered. In selected cases, interproximal reduction or extraction of primary canines may be considered to relieve incisor crowding. A holding appliance may be used when indicated to preserve arch length and leeway space for permanent canines and premolars.

These approaches require a complete diagnosis, defined objectives, and informed consent addressing the expected benefits, limitations, risks, alternatives, costs, expected outcomes, and consequences of observation. Ongoing monitoring includes eruption, oral hygiene, and appliance effects.

What Happens After Phase 1?

Phase 1 treatment for crowding primarily relieves incisor crowding and preserves eruption space for permanent canines and premolars.

After Phase 1, the orthodontist monitors:

Eruption of the permanent teeth
Space for permanent canines and premolars
Dental arch development
Changes in the bite
Stability of the Phase 1 result

A holding appliance may be used when indicated while the permanent teeth emerge.

When the permanent dentition is sufficiently erupted, the orthodontist reassesses the teeth, dental arches, and bite. If maxillary canine space remains deficient and a transverse discrepancy is present, further maxillary expansion may be considered. The appropriate expansion method depends on the diagnosis and skeletal maturity.

The reassessment also determines whether Phase 2 comprehensive orthodontic treatment is needed to align all permanent teeth and refine the bite. Not every child who receives Phase 1 treatment requires Phase 2.

Key Takeaway

Phase 1 treatment for crowding is recommended only when the diagnosis identifies a clear benefit during the early mixed dentition. Its main objectives are to relieve incisor crowding and preserve eruption space for permanent canines and premolars.

After Phase 1, the orthodontist monitors dental development and reassesses the need for Phase 2 once the permanent dentition is sufficiently erupted. Phase 1 does not guarantee that later expansion, comprehensive treatment, or other procedures will be unnecessary.

Before treatment begins, the parent or guardian—and the child, as appropriate—should understand the objectives, reasonable options, expected benefits and limitations, relevant risks, costs, expected outcomes, the consequences of delaying or declining treatment, and the possible need for later care.