27.3 Pulp Therapy in Primary Teeth

4. Pulp Therapy in Primary Teeth

The primary objective of paediatric pulp therapy is to maintain the primary tooth in a functional, symptom-free state until normal physiological exfoliation, preventing arch space loss and avoiding infection of the underlying permanent tooth germ.

Diagnostic Decision Matrix for Primary Tooth Pulp Therapy
  │
  ├── Transient, provoked pain (cold/sweet); resolves immediately; normal furcation radiograph
  │     └── DIAGNOSIS: Reversible Pulpitis
  │           │
  │           └── Coronal pulp exposed during caries removal?
  │                 ├── NO  ──> Indirect Pulp Capping (IPC) or Hall Technique
  │                 └── YES ──> PULPOTOMY (Coronal pulp amputation)
  │                               │
  │                               └── Haemostasis achieved with damp cotton pellet in ≤ 5 min?
  │                                     ├── YES ──> Medicament (MTA / Biodentine / Ferric Sulphate) + PMC
  │                                     └── NO  ──> Radicular pulpitis: convert to PULPECTOMY or EXTRACTION
  │
  └── Spontaneous nocturnal throbbing; sinus/abscess; inter-radicular bone loss; non-vital
        └── DIAGNOSIS: Irreversible Pulpitis / Necrosis
              │
              └── Is the tooth restorable with ≥ 1/3 root length remaining?
                    ├── YES ──> PULPECTOMY (Resorbable paste obturation: ZOE or Vitapex) + PMC
                    └── NO  ──> EXTRACTION (+/- Space Maintainer)

Diagnostic Differentiation: Reversible vs Irreversible Pulpitis

Vital Pulp Therapy

Indirect Pulp Capping (IPC)

Indicated in primary molars with deep carious lesions exhibiting reversible pulpitis, where caries excavation risks mechanical exposure:

• Caries is excavated selectively from the peripheral cavity margins to sound dentine.
• Demineralised affected dentine is left over the pulp chamber to avoid exposure.
• A biocompatible liner (calcium silicate cement, MTA, or resin-modified glass ionomer) is placed over the deep dentine, followed by an immediate hermetic seal with a PMC or composite.

Pulpotomy (Coronal Pulp Amputation)

Indicated when a vital primary tooth with reversible pulpitis undergoes mechanical or carious exposure of the coronal pulp during caries excavation.

• Protocol:
  1. Administer local anaesthetic and achieve rubber dam isolation.
  2. Deradiate and unroof the entire coronal pulp chamber with a high-speed sterile diamond bur, ensuring no dentine overhangs remain.
  3. Amputate all coronal pulp tissue down to the orifices of the root canals using a sharp sterile spoon excavator or a large sterile round bur at slow speed under light water cooling.
  4. Irrigate the chamber gently with sterile saline or water to flush debris.
  5. Haemostasis Verification (Critical Diagnostic Step): Place a sterile cotton pellet moistened with saline over the canal orifices and apply gentle pressure for 3 to 5 minutes.
     • Successful Haemostasis: Bleeding arrests completely within 3–5 minutes. The radicular pulp is vital and non-inflamed. Proceed with pulpotomy medicament placement.
     • Haemostasis Failure (> 5 minutes of persistent bleeding): The inflammatory process has propagated into the radicular pulp tissue (radicular pulpitis). Pulpotomy will fail. The clinician must convert the procedure to a pulpectomy or extract the tooth.

Pulpotomy Medicaments

Non-Vital Pulp Therapy: Pulpectomy

Indicated in restorable primary molars presenting with irreversible pulpitis or pulpal necrosis, where maintaining the tooth is essential for space maintenance (particularly the second primary molar before the eruption of the first permanent molar).

Operative Protocol

1. Complete access opening, canal orifice location, and pulp extirpation.
2. Determine working length radiographically, establishing a limit 1.0 to 2.0 mm short of the radiographic apex to prevent over-instrumentation into the underlying permanent germ.
3. Mechanically debride the canals using hand K-files up to size #30–#35 with gentle filing. Primary root dentine is thin; aggressive filing risks lateral perforation.
4. Irrigate copiously with 0.5%–1.0% sodium hypochlorite (NaOCl), chlorhexidine (0.2%), or sterile saline.
5. Dry canals thoroughly with sterile paper points.
6. Obturation with Resorbable Paste: The root canals must be filled with a material that resorbs at a rate equivalent to physiological root resorption. Suitable pastes include:
   • Pure Zinc Oxide Eugenol (ZOE) without setting catalyst/accelerators.
   • Calcium Hydroxide and Iodoform Paste (Vitapex / Metapex): Superior resorption kinetics; resorbs rapidly if extruded beyond the apex without foreign body reaction.
7. Definitive Restoration: The tooth must be sealed coronally with a Preformed Metal Crown (PMC) to prevent microleakage.

[!CAUTION] Strict Contraindication of Non-Resorbable Materials: Gutta-percha points, resin sealers, and non-resorbable pastes are strictly contraindicated for obturating primary teeth. As the primary roots resorb, non-resorbable materials do not degrade, remaining in the alveolar bone as a rigid physical obstruction that deflects or prevents the normal eruption of the succedaneous permanent tooth.

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Materials and Medicaments

The materials used in primary pulp therapy are examinable in their own right. Ferric sulphate is used as a haemostatic and pulpotomy agent; mineral trioxide aggregate and other calcium silicate cements give high success rates but may discolour the crown; formocresol has largely been abandoned in UK practice on toxicity and carcinogenicity grounds. Root filling in a primary pulpectomy must use a resorbable material — conventionally a non-reinforced zinc oxide eugenol or an iodoform-based paste — so that it resorbs with the root and does not deflect the permanent successor. Using gutta-percha in a primary tooth is a reliable wrong answer.

The examinable decision rule is that pulp therapy is justified only when the tooth is restorable, the child can cooperate for the procedure, and the tooth has a useful lifespan ahead of it; otherwise extraction with appropriate space management is the correct plan.