27.8 Serial Extraction and Non-Nutritive Sucking Habits

5. Serial Extraction: Dewel's Protocol

Serial extraction is an interceptive orthodontic procedure involving the planned, sequential extraction of specific primary and permanent teeth in a child with severe tooth-size to arch-length discrepancy (crowding > 8 to 10 mm per arch), normal skeletal facial proportions (Class I skeletal), and no crossbites.

Dewel's Sequential Protocol

Dewel's Three-Step Serial Extraction Sequence
  ┌─────────────────────────────────────────────────────────────────────────┐
  │ Step 1 (Age 8–9 Years): Extract Primary Canines (Cs)                    │
  │   - Relieves incisor crowding immediately.                             │
  │   - Allows permanent lateral incisors to align spontaneously.           │
  ├─────────────────────────────────────────────────────────────────────────┤
  │ Step 2 (Age 9–10 Years): Extract Primary First Molars (Ds)              │
  │   - Accelerates eruption of first premolars (4s).                       │
  │   - Ensures first premolars emerge into the arch BEFORE canines (3s).   │
  ├─────────────────────────────────────────────────────────────────────────┤
  │ Step 3 (Age 10–11 Years): Extract Erupting First Premolars (4s)         │
  │   - Premolars extracted as soon as they penetrate the gingival margin.  │
  │   - Provides space for permanent canines (3s) to erupt into arch.       │
  └─────────────────────────────────────────────────────────────────────────┘

• Step 1 (Age 8 to 9 years): Extract the primary canines (Cs). This relieves severe crowding in the anterior incisor segment, allowing the permanent central and lateral incisors to erupt and align spontaneously.
• Step 2 (Age 9 to 10 years): Extract the primary first molars (Ds). This accelerates the root development and eruption of the underlying first premolars (4s), encouraging them to erupt into the dental arch before the permanent canines emerge.
• Step 3 (Age 10 to 11 years): Extract the erupting first premolars (4s) as soon as their crowns pierce the gingiva. This creates surplus space in the arch into which the newly emerging permanent canines (3s) can erupt cleanly.

6. Non-Nutritive Sucking Habits

Non-nutritive digit (thumb or finger) and dummy (pacifier) sucking habits alter dental arch architecture depending on the duration, frequency, and intensity of the habit (Moyers' triad), with duration being the critical determinant (habits operating $\ge 6$ hours/day produce dental changes).

Clinical Manifestations

1. Anterior Open Bite (AOB): Asymmetrical open bite reflecting the specific positioning of the thumb or digit between the incisal edges, preventing complete vertical eruption of anterior teeth.
2. Maxillary Incisor Proclination: Labial tipping and flaring of maxillary incisors due to outward hydraulic pressure from the thumb, causing an increased overjet.
3. Mandibular Incisor Retroclination: Lingual tipping of mandibular incisors due to the downward and backward force exerted by the digit shaft.
4. Maxillary Constriction & Unilateral Posterior Crossbite: Digit sucking creates negative intraoral air pressure while depressing the tongue to the floor of the mouth. The normal outward balancing force of the tongue against the palate is lost, while the inward contracting force of the buccinator muscles is unopposed. The maxillary arch constricts transversely, producing a unilateral posterior crossbite with a functional mandibular displacement on closure.

Natural History and Interception

• Spontaneous Self-Correction: If the non-nutritive sucking habit is discontinued before age 6 to 7 years (prior to the full emergence of the permanent incisors), the anterior open bite and transverse discrepancy typically resolve spontaneously through normal perioral soft tissue pressures.
• Active Interception: If the habit persists past age 7 years, intervention is warranted: motivational charts, physical reminders, or fixed habit-breaking appliances (e.g., a palatal crib or palatal arch with spikes) to disrupt the comfort and sensory feedback of sucking.

Balancing and Compensating Extractions

The vocabulary is examined precisely. A balancing extraction is the removal of the contralateral tooth in the same arch, performed to prevent a centreline shift. A compensating extraction is the removal of the opposing tooth in the other arch, performed to prevent over-eruption. The general rules for the primary dentition are that loss of a primary incisor rarely requires balancing; loss of a primary canine, particularly unilaterally, frequently causes a centreline shift and so balancing is usually considered; and loss of a primary first molar may be balanced if crowding is significant, while loss of a primary second molar causes the greatest space loss through mesial drift of the first permanent molar and is usually managed with a space maintainer rather than by balancing.

Managing Poor-Prognosis First Permanent Molars

A closely related and frequently examined decision is the timing of extraction of first permanent molars of poor prognosis, typically from molar–incisor hypomineralisation or gross caries. The ideal time for the lower first permanent molar is when the bifurcation of the second permanent molar is calcifying, generally between eight and a half and ten and a half years of age, because spontaneous mesial drift of the second molar into the space then gives the best result. Planning requires a panoramic radiograph and, usually, an orthodontic opinion; compensating extraction of the upper first molar is often advised to prevent over-eruption, whereas balancing is decided on the crowding present.

Serial extraction is now used selectively rather than routinely, because it commits a child to multiple extractions and usually to subsequent fixed appliance treatment; a specialist orthodontic opinion before starting is the expected UK answer.