27.4 Extractions in the Primary Dentition

5. Extractions in the Primary Dentition: Balancing and Compensating

When a primary tooth is unrestorable, exhibits internal/external root resorption, or presents with infection threatening the developing permanent successor, extraction is indicated. Unilateral primary tooth loss can disrupt arch symmetry and dental alignment.

Arch Symmetry Management in Primary Extractions
  │
  ├── Balancing Extraction: Contralateral tooth in the SAME arch
  │     └── Primary goal: Preserve midline symmetry
  │           ├── Primary Canines (C): MANDATORY balancing extraction
  │           ├── Primary First Molars (D): Balance only in crowded arches
  │           └── Primary Second Molars (E): NEVER balanced (space maintainer instead)
  │
  └── Compensating Extraction: Opposing tooth in the SAME quadrant
        └── Primary goal: Maintain occlusal interdigitation / prevent over-eruption
              └── Rarely indicated in the primary dentition

Balancing Extractions (Contralateral Arch Symmetry)

• Definition: The extraction of the corresponding contralateral tooth on the opposite side of the same dental arch.
• Objective: To maintain dental arch symmetry and prevent a permanent dental midline shift toward the side of unilateral tooth loss.
• Specific Tooth Recommendations:
  • Primary Canines (C): When a primary canine is lost prematurely on one side, the permanent incisors on that side drift and tilt distally into the space, causing an intractable dental midline shift. A balancing extraction of the contralateral primary canine is mandatory to allow symmetrical drift and preserve the midline.
  • Primary First Molars (D): Balancing is indicated only in crowded arches where the early loss of one first primary molar would precipitate a noticeable unilateral space loss and midline shift. In uncrowded arches, balancing primary first molars is unnecessary.
  • Primary Second Molars (E): Never balanced. Premature loss of a primary second molar results in rapid mesial drifting and tipping of the permanent first molar, not a midline shift. Space maintenance (or orthodontic intervention) is required instead of extracting the contralateral healthy molar.

Compensating Extractions (Opposing Quadrant)

• Definition: The extraction of the opposing primary tooth in the opposite arch on the same side (e.g., upper left versus lower left).
• Primary Dentition Rule: Compensating extractions are rarely, if ever, indicated in the primary dentition, because over-eruption of opposing primary teeth is minimal and self-limiting due to the rapid emergence of the permanent successor.

6. Clinical Traps, Pitfalls & Worked Scenario

[!WARNING] Clinical Trap: Misdiagnosing Radicular Furcation Pathology as Periapical Pathology: A candidate evaluates a 5-year-old patient with an asymptomatic, deeply carious primary lower second molar (tooth 75). Bitewing radiographs show no pathology at the root apices, but a distinct radiolucent shadow is visible in the inter-radicular furcation between the mesial and distal roots. A novice may conclude the apices are clear and proceed with a Hall PMC or pulpotomy. This is a critical diagnostic error: in primary molars, accessory canals in the thin pulpal floor cause inflammatory resorption and bone loss to present first in the furcation area. Furcation radiolucency signifies irreversible pulpitis or necrosis, which is an absolute contraindication to the Hall Technique and vital pulpotomy. The tooth requires a pulpectomy or extraction.

[!NOTE] Clinical Trap: Treating Hall Occlusal Elevation with Crown Grinding: Immediately after cementing a Hall PMC, the child bites in premature contact on the crown, leaving the anterior teeth and opposite quadrant open by 1.5 mm. The clinician must never grind the occlusal surface of a stainless steel crown to eliminate the premature contact. Grinding perforates the thin preformed metal, destroying the peripheral biological seal and compromising the restoration. Reassure the carer that physiological dentoalveolar compensation will eliminate the occlusal step within 2 to 4 weeks.

Worked SBA Clinical Scenario

Scenario: A 6-year-old boy is brought to the dental surgery by his mother complaining of discomfort around his lower right jaw. Clinical examination reveals a large Class II occlusal-distal carious cavity in tooth 84 (mandibular right first primary molar). His mother reports that the boy occasionally cries when chewing tough food on that side, but the pain resolves immediately after eating, and he has never woken up at night with toothache. Clinical examination shows no gingival swelling, no sinus tract, and physiological mobility. Bitewing radiographs demonstrate coronal dentine radiolucency extending into the inner third of dentine, with an intact dentine band separating the lesion from the pulp chamber. The inter-radicular furcation and periapical tissues are healthy. During selective caries excavation, a pinpoint (0.5 mm) mechanical exposure of the coronal pulp occurs, bleeding bright red.

Question: What is the most appropriate next clinical step?

Clinical Reasoning Formulation:

1. Diagnostic Status: The history of transient pain provoked only by mastication that subsides immediately, coupled with normal surrounding soft tissues and clear furcation bone on the bitewing radiograph, confirms reversible pulpitis.
2. Therapeutic Selection: Coronal pulp exposure during excavation in a tooth with reversible pulpitis indicates a pulpotomy.
3. Immediate Step: Place a sterile cotton pellet moistened with saline over the exposure/amputated pulp and apply gentle pressure for 3 to 5 minutes to assess haemostasis.
4. Outcome Evaluation: If bleeding arrests within 3–5 minutes, apply Mineral Trioxide Aggregate (MTA) or 15.5% ferric sulphate over the canal orifices and restore definitively with a Preformed Metal Crown (PMC). If bleeding persists past 5 minutes, convert immediately to a pulpectomy or extraction.