Vital pulp therapy

Y-L Ng and K Gulabivala

The aim of this chapter is to outline the technical and clinical elements of prevention and management of pulp disease. The rationale was established in Chapter 2. The general principles of disease management covered previously apply equally well to the primary and secondary dentitions as will be evident from Chapter 1. However, primary teeth bring special challenges of management and are covered here first before describing the management of secondary permanent teeth.

Management of the primary dentition

Retention of the primary dentition until the time of natural exfoliation is important for several reasons. Primary teeth have important roles in mastication, appearance, speech development and space maintenance for the permanent successors. Therefore, there are clear psychological advantages of conserving rather than extracting such teeth.

Endodontic treatment of primary teeth differs from that of permanent teeth for three main reasons – tooth morphology, physiology and pathology. Techniques and medicaments used in primary teeth differ due to these factors and because of the processes of physiological root resorption and exfoliation.

Morphology of primary teeth

The enamel and dentine of primary teeth are thinner and the pulp chamber, with its extended horns, larger in proportion than in permanent teeth (Fig. 7.1). Caries progresses relatively more rapidly to the pulp in the primary dentition.

Fig. 7.1 Comparison of adult and primary molars

Primary molars have irregularly shaped ribbon-like root canals with lateral branches. The floor of the pulp chamber is thin and there are numerous accessory canals in the interradicular area. The permeability of the dentine in this region often leads to interradicular rather than periapical bone loss associated with infected primary molars (Fig. 7.2).

Fig. 7.2 Caries and intraradicular bone loss in (arrowed) primary molars

The roots of the primary teeth are in close relationship to the developing permanent successor and will undergo physiological resorption during the process of exfoliation (Fig. 7.3). Materials used within the root canal system must, therefore, also be resorbable. Their close proximity means that trauma to, or infection of, primary teeth may affect the developing successor. Possible sequelae include enamel defects, arrested development or cyst formation.

Fig. 7.3 Resorption of primary molar roots

Pulp disease in primary teeth

Inflammatory pulpal changes in response to caries occur more rapidly in primary teeth compared to permanent teeth, soon becoming irreversible. Symptoms from such pathological changes in primary teeth may not become severe until the later stages of necrosis and abscess formation (Fig. 7.4).

Fig. 7.4 Abscess associated with primary molar

Diagnosis of pulp disease in young children is complicated by their inability to articulate the problem, which is difficult enough for an adult (see Chapter 4); furthermore, they may respond unpredictably to subjective clinical tests. Techniques used in the management of pulp disease in permanent teeth cannot, therefore, be reliably used in the primary dentition. Methods of objectively measuring inflammatory changes in the pulps of primary teeth by molecular (e.g., prostaglandin) assays are under assessment but not yet ready for implementation.

Techniques of pulp therapy

Indirect pulp capping

Carious lesions should usually be fully excavated before teeth are restored. A clinical dilemma may be presented by the finding of deep caries in an asymptomatic tooth exhibiting no clinical or radiographic evidence of pulp disease in a child whose cooperation or attention span would preclude progress to pulpotomy. Indirect pulp capping may be used in such instances. Its success relies on the observation that the advancing carious front is almost free of cariogenic bacteria. Provided that the overlying infected dentine is removed, a small amount of softened dentine may be left in the deepest part of the cavity and covered with a thin layer of setting calcium hydroxide and then zinc oxide eugenol or reinforced glass ionomer cement. The tooth should then be definitively restored to achieve an optimal coronal seal with an adhesive or preformed metal restoration. The tooth may then be reviewed clinically and radiographically to ensure that progression of pulp disease does not lead to periapical involvement. This avoids a second operative visit, which is an obvious advantage for children.

Direct pulp capping

This technique is generally contraindicated for the primary dentition. Pathological changes progress rapidly within the pulps of primary teeth and their healing ability is limited. Pulpal inflammation usually persists and progresses to internal root resorption and then necrosis, particularly when calcium hydroxide is used to dress the exposed pulp (Fig. 7.5). Use of the technique may be justified in exceptional circumstances, such as to manage a small traumatic exposure in otherwise sound dentine during cavity preparation. Haemorrhage from the exposure should be minimal and easily controlled by gentle application of a cotton pledget soaked in sterile water/saline. Further haemorrhage would indicate more severe pulpal inflammation and pulpotomy would be the treatment of choice. If the bleeding is easily arrested, calcium hydroxide or mineral trioxide aggregate (MTA) (Table 7.1) may be used to dress the wound, followed by tooth restoration.

Table 7.1

The constituents of MTA™ and Biodentine™

Fig. 7.5 Internal root resorption

Biodentine™, which is a new biocompatible and bioactive calcium silicate based material (see Table 7.1), has been advocated for use as a dentine “replacement”, as well as a direct pulp capping agent. It has been shown to have the potential to induce transforming growth factor β1 (TGF-β1) release from human pulp cells and early dental pulp mineralization but further laboratory and long-term clinical outcome studies are required.