Nowadays, the preservation of dental pulp vitality is an integral part of our daily therapies. The success of these treatments depends on the clinical situation as well as the biomaterials used. Mineral Trioxide aggregate and Biodentine^TM are commonly used as pulp capping materials. One objective of vital pulp therapy is the repair/regeneration of the pulp. In addition to the initial inflammatory status of the pulp, the nature and quality of the new mineralized tissue obtained after pulp capping directly influence the success of the treatment. In order to characterize the reparative dentin, in the current study, the chemical composition and microstructure of the dentin bridge after direct pulp capping using Biodentine™ and mineral trioxide aggregate (MTA) was studied by using Raman microspectroscopy and scanning electron microscopy, respectively. The results showed that the reparative dentin bridge observed in both groups presented dentin tubules and chemical composition similar to primary dentin. With the limitations of this study, the calcium-silicate-based cements used as pulp capping materials provide an optimal environment for pulp healing, resulting in a reparative dentin resembling on certain points of the primary dentin and the regeneration of the pulp.

Dental pulp is a dynamic tissue able to heal after injury under moderate inflammatory conditions. Our study aimed to evaluate pulp repair under inflammatory conditions in rats. For this purpose, we developed a rat model of controlled pulpitis followed by pulpotomy with a tricalcium silicate-based cement. Fifty-four cavities were prepared on the occlusal face of the maxillary upper first molar of 27 eight-week-old male rats. E. coli lipopolysaccharides at 10 mg/mL or phosphate-buffered saline PBS was injected after pulp injury. Non-inflamed molars were used as controls. Levels of inflammation-related molecules were measured 6 and 24 h after induction by enzyme-linked immunosorbent assay of coronal pulp samples. Pulp capping and coronal obturation after pulpotomy were performed with tricalcium silicate-based cement. Four and fifteen days after pulpotomy, histological and immunohistochemical analysis was performed to assess pulp inflammation and repair processes. Our results showed significantly higher levels of innate inflammatory proteins (IL-1β, IL-6, TNF-α and CXCL-1) compared with those in controls. Moderate residual inflammation near the capping material was demonstrated by histology and immunohistochemistry, with the presence of few CD68-positive cells. We showed that, in this model of controlled pulpitis, pulpotomy with Biodentine^TM allowed the synthesis at the injury site of a mineralized bridge formed from mineralized tissue secreted by cells displaying odontoblastic characteristics. Analysis of these data suggests overall that, with the limitations inherent to findings in animal models, pulpotomy with a silicate-based cement is a good treatment for controlling inflammation and enhancing repair in cases of controlled pulpitis.

The regenerative endodontic procedure (REP) represents a treatment option for immature necrotic teeth with a periapical lesion. Currently, this therapy has a wide field of pre-clinical and clinical applications, but no standardization exists regarding successful criteria. Thus, by analysis of animal and human studies, the aim of this systematic review was to highlight the main characteristics of the tissue generated by REP. A customized search of PubMed, EMBASE, Scopus, and Web of Science databases from January 2000 to January 2022 was conducted. Seventy-five human and forty-nine animal studies were selected. In humans, the evaluation criteria were clinical 2D and 3D radiographic examinations. Most of the studies identified a successful REP with an asymptomatic tooth, apical lesion healing, and increased root thickness and length. In animals, histological and radiological criteria were considered. Newly formed tissues in the canals were fibrous, cementum, or bone-like tissues along the dentine walls depending on the area of the root. REP assured tooth development and viability. However, further studies are needed to identify procedures to successfully reproduce the physiological structure and function of the dentin–pulp complex.

The main goal of vital pulp therapy (VPT) is to preserve the vitality of the pulp tissue, even when it is exposed due to bacterial invasion, iatrogenic mechanical preparation, or trauma. The type of new dentin formed as a result of VPT can differ in its cellular origin, its microstructure, and its barrier function. It is generally agreed that the new dentin produced by odontoblasts (reactionary dentin) has a tubular structure, while the dentin produced by pulp cells (reparative dentin) does not or has less. Thus, even VPT aims to maintain the vitality of the pulp. It does not regenerate the dentin pulp complex integrity. Therefore, many studies have sought to identify new therapeutic strategies to successfully regenerate the dentin pulp complex. Among them is a Wnt protein-based strategy based on the fact that Wnt proteins seem to be powerful stem cell factors that allow control of the self-renewal and proliferation of multiple adult stem cell populations, suitable for homeostasis maintenance, tissue healing, and regeneration promotion. Thus, this review outlines the different agents targeting the Wnt signaling that could be applied in a tooth environment, and could be a potential therapy for dentin pulp complex and bone regeneration.

Objectives: Repeated lipopolysaccharide (LPS) stimulation is a well-established model of chronic inflammation in conditions such as sepsis, lung disease, and arthritis, where it activates the nuclear factor-κB (NF-κB) pathway. Because deep caries similarly expose dental pulp to bacterial toxins, applying this approach to rat molars could clarify how recurrent LPS challenges drive pulp inflammation. This study evaluated whether one to three inductions of LPS or phosphate-buffered saline (PBS, positive control) induce progressive molecular and histological changes in rat pulp. Methods: Exposed upper first molars received 1-3 inductions of LPS or PBS. Pulp tissue was collected 6, 24, and 48 hours after the final induction for histology and quantitative polymerase chain reaction (qPCR). Results: Gene expression analysis showed significant modulation of inflammatory and remodelling markers (IL6, MMP3, MMP9, CCR7, CXCL1, HO1, and DSPP) with repeated stimulations. Histological alterations were more pronounced after multiple exposures, although no significant differences emerged between LPS- and PBS-treated teeth. The progressive rise in the MMP9/DSPP ratio suggests its potential as an indicator of pulpal tissue degradation. Conclusion: This model offers preliminary knowledge about the sequential molecular and histological responses of rat pulp to repeated bacterial challenges. Although further work is needed to isolate LPS-specific effects and confirm chronic features, these findings help delineate the early dynamics of pulp inflammation.

Évaluation de la réponse inflammatoire et de réparation dans un modèle innovant de pulpite molaire de rat: La maladie carieuse est l'une des maladies infectieuses les plus répandues dans le monde avec un coût biologique et économique extrêmement lourd. Les infections bactériennes cariogènes sont responsables de l'initiation et de la progression de la lésion carieuse à l'origine de la déminéralisation de l'émail, dentine et l'initiation d'une réponse inflammatoire pulpaire entrainant des lésions subséquentes. Cliniquement, l'inflammation pulpaire est caractérisée par une pulpite réversible ou irréversible, et la différence réside essentiellement dans l'intensité de la douleur. D'après plusieurs études et notamment celle de Riccuci, il n'y a pas toujours de corrélation entre les diagnostics clinique et histologique. Il n'existe pas d'outil de diagnostic fiable à 100%. Aujourd'hui, une dent en pulpite irréversible est traitée endodontiquement par l'éviction totale de la pulpe dentaire et son remplacement par un matériau inerte. Un traitement très complexe à réaliser. La littérature décrit un grand nombre d'échecs ~ 50% se manifestant par la présence de lésion périradiculaires ou de fracture dentaire. Des traitements alternatifs permettent de préserver la vitalité pulpaire en réalisant un coiffage avec un matériau bioactif. Ces techniques sont déjà largement utilisées lors d'une pulpite réversible. Actuellement, la dentisterie moderne consiste à préserver au maximum la pulpe. Des cliniciens ont tenté ces traitements dans les cas de pulpites irréversibles. Le succès est variable à cause de la difficulté à poser les bonnes indications. Le statut inflammatoire pulpaire demeure le maillon faible de cette stratégie de conservation de la vitalité pulpaire. Il est nécessaire de mener plus d'études analysant les données biologiques de la pulpite, afin de développer de nouveaux outils diagnostics plus fiables reposant sur le niveau d'inflammation pulpaire. Et d'étendre les thérapeutiques de vitalité pulpaire à certaines pulpites dites irréversibles. L'inflammation pulpaire est caractérisée par la surexpression de plusieurs marqueurs de l'inflammation notamment pro-inflammatoire, qui jouent un rôle dans la pathogénèse de la pulpite. Il a été montré que le niveau de ces marqueurs était variable en fonction de la nature faible ou sévère de la pathologie. L'objectif de mon travail de thèse est double. Le premier objectif est de créer un nouveau modèle de pulpite graduelle. L'inflammation est induite par l'injection de LPS d'E. Coli versus PBS après la réalisation d'une d'effraction pulpaire sur la molaire de rat. Cette induction est réalisée graduellement et conduit à la nécrose. Ce modèle va permettre d'analyser et comprendre l'évolution histologique, immunohistochimique, l'expression génique et moléculaire des différentes étapes de cette inflammation. L'analyse qPCR par micropuces de 89 analytes de l'inflammation, fait ressortir des variations d'expression de l'ordre de la tendance pour 22 molécules selon le temps ou le type d'induction. Mais des études complémentaires sont encore nécessaires afin d'affiner ces résultats. Le deuxième objectif est d'étudier la réparation du complexe pulpo-dentinaire sur le modèle d'inflammation en réalisant une pulpotomie camérale et son obturation à l'aide d'un matériau bioactif : la BiodentineTM. Les temps d'inflammation de 6h et 24h d'induction ont montré que la pulpe était encore capable de se réparer en établissant un pont dentinaire au contact de la BiodentineTM. Le temps d'induction de 24h a montré que ce pont dentinaire était moins dense mais plus étendu. En d'autres termes, ce travail de thèse investigue la corrélation entre le niveau de l'inflammation pulpaire et la qualité de la réparation/régénération pulpaire. Les résultats obtenus permettront de créer un modèle de pulpite irréversible. Et un modèle d'inflammation graduelle afin de comprendre l'inflammation pulpaire et trouver un outil de diagnostic ou de nouvelles thérapeutiques pour repousser les limites de la conservation de la vitalité pulpaire.