SARPE Activation Protocol: Revise & Review

Surgically Assisted Rapid Palatal Expansion (SARPE) is the preferred approach for managing transverse maxillary deficiency in skeletally mature patients, where traditional Rapid Maxillary Expansion (RME) fails due to the fusion of midpalatal and circummaxillary sutures. Unlike RME in adolescents, SARPE relies on surgical mobilisation of the maxillary halves, followed by controlled mechanical expansion. To ensure safe and stable outcomes, Orthodontist must follow a precise, evidence-based activation protocol.

1. Latency Period (Healing Before Activation)

Following SARPE surgery—typically involving a Le Fort I osteotomy and midpalatal split—a latency period of 5 to 7 days is advised before beginning expansion. This allows soft tissue revascularisation and initial osteogenic activity at the osteotomy sites.

• Verstraaten et al. (2010) and Mommaerts (1999) support a 5-day delay, citing improved predictability and reduced risk of early consolidation.

• Immediate activation (<48 hours), although reported in some protocols, carries a higher risk of scar formation and relapse.

2. Activation Rate

The most widely accepted rate is 0.5 mm/day, performed as 0.25 mm turns twice daily. This rate strikes a balance between efficient skeletal expansion and reduced trauma to the surrounding bone and periodontal structures.

• Studies such as Northway & Meade (1997) and Betts et al. (1995) highlight that faster rates may result in poor bone fill and excessive strain on the anchorage teeth.

• Bone-borne appliances may tolerate a slower rate of 0.25 mm/day, yielding more controlled, parallel skeletal separation.

3. Total Expansion Time

Typically, the activation phase lasts 7 to 14 days, depending on the severity of the maxillary deficiency. The goal is often 7–10 mm of expansion, confirmed clinically and radiographically. The appearance of a midline diastema confirms skeletal separation of the maxilla.

4. Retention/Consolidation Phase

A minimum 3-6 month consolidation period is essential post-expansion to allow osteogenesis within the widened suture.

• Bailey et al. (1997) suggest leaving the expander passively in place for up to 6 months to prevent collapse.

• Premature removal may lead to relapse due to inadequate bone formation across the expansion site.

5. Orthodontic Treatment Initiation

Light orthodontic forces can be applied 4–6 weeks after expansion, once initial bone healing has occurred. This timing also capitalises on the Regional Acceleratory Phenomenon (RAP), which facilitates faster and more efficient tooth movement post-surgery (Lines, 1975).

6. Appliance Type & Protocol Adjustment

Tooth-borne expanders (e.g. Hyrax) may lead to dental tipping and alveolar bending. While bone-borne or hybrid expanders reduce dental side effects and are more suitable for adult patients. According to Koudstaal et al. (2006), bone-borne devices produce more parallel, skeletal expansion with fewer periodontal consequences.

In Summary:

• Latency: 5–7 days post-surgery

• Activation: 0.25 mm twice daily (total 0.5 mm/day)

• Duration: 2-3 weeks depending on the required expansion

• Retention: At least 3-6 months

• Ortho movement: Begin 4–6 weeks after expansion

• Appliance: Bone-borne preferred in adults