Indirect pulp capping is a treatment modality that has gained increased popularity recently that can be undertaken in a single-visit appointment (indirect pulp capping) or a two-stage procedure (stepwise excavation) [3, 16, 17]. The premise of either treatment is to prevent exposure of the pulp during deep carious excavation by leaving the deepest carious dentine overlying the pulp in place to preserve vitality. Residual dentine thickness is an important prognostic factor for reactionary dentinogenesis and the ability of surviving odontoblasts to secrete tertiary dentine allowing continued pulp survival.

A suitable lining material is placed to allow for reparative dentine stimulation [18]. There is no general agreement as to what type of lining material is ideal although calcium hydroxide, mineral trioxide aggregate (MTA), composite resins and glass ionomer cements have all appeared to be satisfactory in their ability to induce a calcific barrier formation [19]. The placement of a high-quality temporary and final restoration is essential for success.

In the stepwise approach for caries excavation, various amounts of carious dentine are sealed off by a temporary restoration for a period of time. Re-entry is carried out in anticipation of the possibility of remineralisation of softened noninfected dentine over the pulp and hard tissue repair. The intent is to carry out further excavation of remaining caries without ensuing pulpal exposure [20, 21].

A potential disadvantage of carrying out these types of procedures is delaying the inevitable pulpectomy and possible difficulties thereof due to ensuing pulpal reactions and calcifications that can lead to negotiation difficulties. Unfortunately, treatments are guided to either invasive pulp therapy or procedures aimed at maintaining pulpal integrity based on the probable pulpal status, which can only be verified following careful follow-up. The advantage in an immature tooth with continued root development is obvious, but in a mature tooth, the obvious benefits must be weighed up against the possibility of developing a peri-radicular apical lesion, which reduces the success rate of root canal treatment [22].

Direct pulp-capping procedures are required when an inadvertent pulp exposure has occurred. The decision to avoid a pulpectomy is based on the assumption that the radicular pulp remains vital and only superficial inflammation is present confined to a few millimetres at the site of exposure. Controversy has plagued this treatment modality, and its success depends on various issues including the size of pulpal exposure, presence of infected dentinal chips, control of haemorrhage, type of pulp-capping material used and the quality of the ‘dentinal bridge’ formed [23]. The technique is not normally advocated for carious primary molars [24].

A pulpotomy procedure should be performed on a tooth that is judged vital. The coronal pulp is amputated, and then the radicular pulp is either fixed using formocresol, preserved using a haemostatic agent such as ferric sulphate or sodium hypochlorite solution to form a clot barrier or bridged by using calcium hydroxide or mineral trioxide aggregate [30–32]. The success of the technique is highly dependent on achieving a good coronal seal, which will effectively cut off the nutritional supply for any remaining dentinal bacteria and will prevent further bacterial micro-leakage. It has been strongly recommended that adhesive restorations or preformed crowns be employed following any primary molar pulp therapy procedure [25–28].

There has been a suggestion that the use of formocresol in paediatric dentistry is unwarranted due to safety concerns. Studies have linked formocresol with nasopharyngeal cancer in both human and animal studies based on exposure to formaldehyde at very high doses. The evidence in the literature suggests that formocresol is probably not a potent human carcinogen under low-exposure conditions. Nevertheless, the fixation of radicular pulp stumps using formocresol is no longer recommended, and alternatives using either ferric sulphate or mineral trioxide aggregate have been advocated using clinical studies to demonstrate equal if not better results [27–30].

Ferric sulphate (5–15 %) promotes pulpal haemostasis by forming a protective metal-protein clot at the surface of the vital radicular pulp stumps. A zinc oxide eugenol base is then usually applied over the radicular pulpal tissue.

MTA has been used successfully in adult endodontic procedures since 1993 and has been recommended for pulp capping, pulpotomy, apical barrier formation in teeth with open apexes, repair of root perforations and root canal filling. The constituents include tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, calcium sulphate and bismuth oxide. The material has excellent bioactive properties and essentially stimulates cytokine release from pulpal fibroblasts, which in turn stimulates hard tissue formation. In pulp-capping or pulpotomy procedures, it is mixed with sterile water to a sandy consistency, which is gently packed against the radicular pulp stumps. The material is hydrophilic and takes up to 4 h to set completely [32].

Desensitising pulp therapies have been recommended primarily for deciduous teeth and also used by some clinicians for the permanent dentition [33]. This two-stage technique uses paraformaldehyde paste to fix and devitalise hypersensitive coronal pulp tissue. In view of increasing concerns about the use of formaldehyde (as previously mentioned), an alternative approach, using Ledermix paste, has been recommended [34]. Ledermix is a readily available paste containing triamcinolone acetonide (steroid) and demeclocycline (antimicrobial). It is used widely in adult endodontic procedures and has been shown to reduce pulpal inflammation and pain.

Pulpectomy is indicated where the radicular pulp is nonvital or irreversibly inflamed. It is contraindicated when there is evidence of extensive internal or external root resorption or if more than one-third of the root length has been lost. The most commonly used medicaments for primary molar root canal therapy are zinc oxide eugenol (ZnOE) paste, iodoform paste and calcium hydroxide [35, 36]. Slow-setting pure zinc oxide eugenol paste has traditionally been the material of choice as a primary molar root filling material. However, concerns have been expressed regarding the slow removal of zinc oxide eugenol by the body (if extruded through the root apex) and the differential rate of resorption between this material and the tooth itself. The use of Vitapex (a mixture of calcium hydroxide and iodoform paste) has a superior success rate to that of zinc oxide eugenol and is removed more readily if extruded through an apex [37].

A recent systematic review of the literature summarised that because of the lack of good studies, it is not possible to determine whether an injured pulp as a result of deep caries can be maintained or whether it should be removed and replaced with a root canal filling. Both randomised studies and prospective observational studies are needed to investigate whether a pulp exposed to deep caries is best treated by measures intended to preserve it or by pulpectomy and root filling [38]. Current practice is dictated by best clinical judgement as to the pulpal diagnosis and appropriate treatment thereafter. Indirect pulp-capping, pulpotomy and pulpectomy procedures are indicated in deciduous teeth in order to remain as space maintainers avoiding crowding if the tooth was lost early. Immature teeth with incomplete root formation would be teeth that gain most benefit from pulp preservation procedures rather than less conservative pulpectomy treatments. Root canal procedures are reserved for those cases where apical periodontitis has been confirmed and extraction is to be avoided.