13 June 2023

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Pulp capping: a technique to preserve the vitality of the tooth

By Arianna Bianchi

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The dental pulp is extremely important for the vitality of the tooth, as it represents a source of nourishment for it, also performing a bioindicator function with regard to pathogenic elements.

Very often, pulp infections are irreversible processes and therefore it is difficult for the body to eliminate the infection, which persists and worsens over time. For this reason, endodontic therapy is one of the most used techniques in dentistry, allowing the removal of contaminated or damaged pulp tissue and replacing it with a biocompatible synthetic material to prevent future contamination.

It should be underscored that, thanks to the advances in dental biomaterials and endodontic technology, the success rate of root canal therapies has increased considerably in the last ten years.

Materials and methods

The purpose of the study, published in August 2019 in the Journal of Clinical and Molecular Pathology, is to provide a synthesis of the literature on pulp capping therapies, the aim of which is to prevent the passage of bacteria and promote healing of the pulp. dental pulp.

A search was conducted on PubMed, Cochrane and Journal of Endodontics, using the following keywords: Dental pulp capping, MTA, Biodentin. Then a "manual" search was performed from the list of pre-selected items.

Dentin is a hard, radiopaque, permeable tissue. It is mainly composed (for 70%) of a mineral, hydroxyapatite. In addition to it, there is also an organic type matrix, mainly collagen types I, V and III, matrix proteins (osteocalcin, octeonectin, octeopontin), proteoglycans, albumin, growth factors (TGFB-1, IGFI and PDGF) and metalloproteases. Finally, an aqueous component (12%) is also present inside the dentin.

The dentin has a particular structure, as it is perforated by millions of tubules (called dentinal tubules), which all converge centripetally towards the pulp. Within each dentinal canal there is an extension of an odontoblast surrounded by its fluid. The composition of this dentin fluid is similar to that of blood plasma, but with a higher concentration of calcium ions. In the presence of exposure to the dentin, the overpressure causes the leakage of the dentin fluid into the oral cavity. This leakage of liquid towards the outer limits, among other things, is the spread of bacteria on the pulp.

The dental pulp is substantially confined in a closed space, being almost surrounded by dentin. At the root apex, however, there is an orifice, the apical foramen, through which the elements necessary for its vascularization and innervation reach the pulp. The pulp is divided into two distinct areas: a large area located in the dental crown, called the pulp chamber and containing the so-called chamber pulp, and a smaller area located in the roots, i.e., the root canals containing the root pulp.

The oral cavity is colonized by many microorganisms, of which streptococci are the main components.

Dental caries is the main process causing inflammation and necrosis of the pulp. These processes are caused both by direct contact of bacteria with the pulp tissue and indirectly through bacterial antigens traveling through the dentinal ducts.

However, even traumatic causes such as "accidental" fractures with or without exposure of pulpal tissue - but also malocclusions, abrasions, dental wear, poorly adapted orthodontic or prosthetic appliances - can lead to an alteration of the dento-pulpal complex.

It is also possible that the inflammation of the pulp may be iatrogenic and be linked to the use of rotary instruments, dental materials such as composite resins or orthophosphoric acid used in adhesion processes or hydrogen peroxide or carbamide peroxide.

The responses of the dento-pulp complex to possible pathogenic noxae are quite complex and involve a series of mediators, which trigger an inflammatory response. If it is too severe, the tissue changes that the pulp has undergone become irreversible, thus giving rise to a process defined precisely as "irreversible pulpitis".

However, it is important to underline how the age of the patient plays a fundamental role in the possible healing process: a young pulp, in fact, will be easier to heal unlike an older pulp which will have already undergone many episodes of inflammation.

Results

There are essentially two pulp capping techniques: direct and indirect.

Direct capping consists in the application of a biomaterial in direct contact with the exposed pulp tissue, to promote its healing and obliteration by means of a newly formed dentin bridge. This technique, however, can only be applied to a pulp that has suffered reversible damage. It is therefore necessary to ensure that the treated tooth responds positively to the vitality tests (and in this respect the thermal tests, cold or hot, are the most used).

It must be emphasized that the cause that led to the exposure of the pulp tissue influences the success rate. If the exposure occurs accidentally, for example during the preparation of a cavity or a post of a crown, the success rate of direct capping is extremely high, since bacterial contamination is minimal. If, on the other hand, the pulp exposure is the result of a carious process, the probability of success is reduced, as there is a greater presence of bacteria within the pulp tissue.

It is also essential that all hooding maneuvers are conducted under a dam, after having administered to the patient a quantity of anesthetic sufficient to guarantee his comfort. Bleeding control is also of fundamental importance: it has in fact been demonstrated that if the material is placed in contact with a bleeding pulp, there is no formation of tertiary dentin (the previously mentioned dentinal bridge) and therefore the vitality of the pulp is not maintained. dental element.

Indirect pulp capping, on the other hand, is a therapy that consists of covering the dentin with a protective (and/or dentinogenic) material to promote healing of the pulpo-dentinal complex. Indirect pulp capping consists of removing the pathogen, creating secondary dentin at sites of pulp inflammation, eliminating pulp inflammation, demineralizing the affected dentin, and sealing the cavity to reduce the risk of new bacterial overgrowth. Also in this case, the treatment must be performed under a dam after a suitable anesthesia.

After that, the infected dentin is removed and the cavity is sealed with a bioactive material, which must have bactericidal properties and stimulate dentinogenesis.

There are varied materials for capping. The most used is generally glass ionomer cement (CVI), which is defined as the gold standard, or zinc oxide eugenol (ZOE). A second material is then applied to the first layer which must meet certain requirements: total absence of microfiltration by perfect sealing of the tooth/material interface, sufficient support of occlusal loads and insolubility.

However, the most used material in most cappings is calcium hydroxide, whose first application in dentistry dates to 1920. Since then, the field of action of calcium hydroxide has continued to develop and remains, even today, a flagship product in the dentist's therapeutic arsenal.

Since these materials have some limitations, such as lack of adhesion and porosity (which can therefore be secondary entry routes for bacteria and their metabolites), new materials have been studied and introduced on the market. The first of these is Mineral Trioxide Aggregate (MTA), a derivative of Portland cement, commonly used in construction. MTA has several biological properties: it is known for its anti-inflammatory action, as well as having an antibacterial action in aqueous media thanks to its alkaline ph. It has no effect on strictly anaerobic bacteria but appears to be effective on some optional anaerobic bacteria (such as Streptococcus mutans) and possesses antifungal properties. Beneath the MTA layer, the damaged pulpal tissue heals by angiogenesis and neovascularization, as well as by proliferation of functional cubic cells in the vicinity of the damaged area.

Another new material is biodentine, a calcium silicate-based dentin replacement material. Biodentine differs from other traditional Portland cement-based materials due to the absence of aluminum components and the presence of water-soluble polymers to guarantee the balance between a low concentration of water, necessary for the curing of the product, and a risk of porosity, followed by microfiltration and degradation of the material in the presence of an excessive amount of water. Biodentin is a promoter of reaction dentin creation, mineralization and angiogenesis. Its use is indicated for direct and indirect pulp capping, pulpotomies and perforation repairs.

Conclusions

The evolution of dental practices towards tissue conservation is leading towards the conservation of pulp vitality. However, many dentists fear failure and therefore prefer not to try to preserve it rather than perform a systematic pulpectomy.

According to the authors of the article, certainly the development of materials of the bioceramic family is largely responsible for this renewed interest in the preservation of pulp vitality through capping, as if dentists thought that it is thanks to these intelligent materials that the pulp capping succeeds, which isn't entirely false, but it's a long way from being true.

For more information: "Dental pulp capping: a literature review."