Is Pulp Inflammation a Prerequisite for Pulp Healing and Regeneration?

Abstract

The importance of inflammation has been underestimated in pulpal healing, and in the past, it has been considered only as an undesirable effect. Associated with moderate inflammation, necrosis includes pyroptosis, apoptosis, and nemosis. There are now evidences that inflammation is a prerequisite for pulp healing, with series of events ahead of regeneration. Immunocompetent cells are recruited in the apical part. They slide along the root and migrate toward the crown. Due to the high alkalinity of the capping agent, pulp cells display mild inflammation, proliferate, and increase in number and size and initiate mineralization. Pulp fibroblasts become odontoblast-like cells producing type I collagen, alkaline phosphatase, and SPARC/osteonectin. Molecules of the SIBLING family, matrix metalloproteinases, and vascular and nerve mediators are also implicated in the formation of a reparative dentinal bridge, osteo/orthodentin closing the pulp exposure. Beneath a calciotraumatic line, a thin layer identified as reactionary dentin underlines the periphery of the pulp chamber. Inflammatory and/or noninflammatory processes contribute to produce a reparative dentinal bridge closing the pulp exposure, with minute canaliculi and large tunnel defects. Depending on the form and severity of the inflammatory and noninflammatory processes, and according to the capping agent, pulp reactions are induced specifically.

Reactionary and reparative dentin formation after pulp capping: Hydrogel vs. Dycal

“…The nemosis-induced inflammatory reaction stimulates the dental pulp, leading to massive proinflammatory, proteolytic, and growth factor responses. The programmed cell death included the release of cycloxygenase-2, prostaglandin E2, interleukin-8, and several MMPs (Goldberg et al 2015). The globular structures seen only after Hydrogel capping seem to be connected with the initial steps of mineralization.…”

“…The comparison between the two capping agents shed lights on the actual differences between Dycal capping, inducing an inflammatory process, closely associated with the presence of necrotic areas, and Hydrogel treatment where inflammatory pulp cells were undetectable. The role of inflammation in the repair process seems to be a crucial point (Goldberg et al 2015).…”

“…In addition to the available Ca(OH) 2 liners, recent studies shed lights on the possibility that self-assembling peptide hydrogels may contribute to support the differentiation of dental pulp stem cells (Li et al 2014). As new tools for tissue engineering, hydrogels constitute injectable scaffolds, and cell and bioactive molecule carriers (Cavalcanti et al 2013;Goldberg et al 2015).…”

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“…To be able to repair itself and generate a hard-tissue barrier, the pulp must eventually stop the inflammation of the pulp and continue to regenerate itself by stimulating its cells at the injured site and organize a dentinal bridge. 24 To repair the damaged odontoblast and heal the injury of the pulp, an ideal capping material should be able to stimulate the dentinogenic potential of the human dental pulp cells or dental pulp stem cells (DPSCs). Currently, calcium hydroxide is generally used for pulp capping, which has been evaluated by many long-term studies whose results were acceptable.…”

Reactions of human dental pulp cells to capping agents in the presence or absence of bacterial exposure

“…Pulp cells affected by trauma or carious lesions undergo an inflammatory process, ultimately stimulating osteo/ orthodentin bridge formation that partially or completely occludes pulpal exposure (1,2). The cellular response driving such repair may be the proliferation and differentiation of odontoblast-like cells that are derived from dental pulp progenitors (3).…”