The protective role of curcumin in human dental pulp stem cells stimulated by lipopolysaccharide via inhibiting NF-κB p65 phosphorylation to suppress NLRP3 inflammasome activation.

OBJECTIVES: This study aims to investigate the anti-inflammatory effect of curcumin and underlying mechanisms regarding the modulation of the nod-like receptor pyrin domain containing 3 (NLRP3) inflammasome in human dental pulp stem cells (hDPSCs). MATERIALS AND METHODS: The impact of curcumin on the viability of hDPSCs was evaluated. The effect of curcumin on the expression of IL-1ß and NLRP3 in hDPSCs stimulated by lipopolysaccharide (LPS) was assessed. Then, LPS-primed hDPSCs were pre-treated with curcumin before ATP triggering NLRP3 inflammasome activation, and NLRP3 inflammasome-related mediators were assessed. The mechanism of curcumin inactivation of LPS plus ATP-induced inflammasome associated with NF-κB pathway was explored. The NF-κB pathway related pro-inflammatory mediators at mRNA and protein levels were evaluated. The expression of NF-κB p65 and phosphorylation p65 was visualized after curcumin or NF-κB inhibitor administrating respectively in hDPSCs with an activated NLRP3 inflammasome. Statistical analysis was performed. RESULTS: While curcumin at the concentration of 0.5-5 µM showed no obvious impact on the viability of hDPSCs, it significantly decreased IL-1ß and NLRP3 mRNA expression in LPS-induced hDPSCs in a dose-dependent manner. Curcumin significantly inhibited the LPS plus ATP-primed NLRP3 inflammasome activation in hDPSCs (NLRP3, ASC, caspase-1, and IL-1ß). Curcumin evidently attenuated the LPS plus ATP-induced expression of NF-κB pathway-related pro-inflammatory mediators (IL-6, IL-8, TNF-α, and COX-2). Furthermore, curcumin effectively reduced p65 phosphorylation, which acts as an NF-κB inhibitor in hDPSCs with an activated NLRP3 inflammasome. CONCLUSIONS: Curcumin pre-treatment may exert an anti-inflammatory role via inactivation of the NLRP3 inflammasome by inhibiting NF-κB p65 phosphorylation in cultured hDPSCs. CLINICAL RELEVANCE: Curcumin may have therapeutic potential in pulp inflammation.

The efficacy of platelet-rich fibrin as a scaffold in regenerative endodontic treatment: a retrospective controlled cohort study.

BACKGROUND: Blood Clot (BC) or platelet concentrates have been used as scaffold in regenerative endodontic treatment (RET). The aim of this retrospective study was to compare the performance of platelet-rich fibrin (PRF) with BC in inducing root development and periapical lesion healing after tooth revascularization. METHODS: Five patients receiving RET using PRF as a scaffold were matched 1:1 to a previous cohort of 5 patients who underwent tooth revascularization by provoking periapical bleeding. Clinical signs and symptoms were examined at follow-ups. Periapical lesion healing and root development were monitored radiographically. The resolution of clinical signs and symptoms as well as periapical radiolucency was observed in all patients (100%). RESULTS: Root elongation, dentinal wall thickening and apex closure were found in most cases (80% in both groups). There was no significant difference between the groups in terms of clinical sign resolution, root development and periapical healing. CONCLUSIONS: Within the limits of this study, PRF achieved comparable outcomes to BC in terms of clinical sign and symptom resolution, periapical lesion healing and continued root development in RET.

Radiographic, Histologic, and Biomechanical Evaluation of Combined Application of Platelet-rich Fibrin with Blood Clot in Regenerative Endodontics.

INTRODUCTION: No in vivo study has been reported on the mechanical reinforcement of a tooth after regenerative endodontic treatment (RET). The present work aimed to evaluate the concurrent use of platelet-rich fibrin (PRF) with a blood clot (BC) in RET concerning periapical healing, root development, and tooth structural reinforcement. METHODS: In our study, 24 premolars from 3 beagle dogs were assigned into control, BC, and PRF + BC groups. Periapical healing was monitored with quantitative measurements of root elongation and thickening radiographically. Tooth biomechanical integrity was assessed with the fracture resistance test. Histologic evaluation was conducted. RESULTS: There was a significant difference among the periapical radiolucency decreasing rate of the control (43.75%) and the BC (100%) and PRF + BC (100%) groups (P < .05). The increase of root length and thickness in both the BC and PRF + BC groups was significantly greater than that in the control group (P < .05). No significant difference was detected between the 2 experimental groups regarding periapical healing or root development (P > .05). Teeth in the BC (249.3 ± 64.1 N) and PRF + BC (281.7 ± 37.8 N) groups had significantly higher fracture resistance than those in the control group (108.5 ± 23.3 N) (P < .05). No significant difference was revealed between the BC and PRF + BC groups (P > .05). Histologic evidence of cementumlike tissue deposition along the canal wall with scattered bonelike tissue in the canal was observed. CONCLUSIONS: Either a combination of PRF with BC or BC alone could improve periapical healing, induce root development, and reinforce tooth structure. No additional benefit of PRF to BC in RET was found.

Histologic and Immunohistochemical Findings of a Human Immature Permanent Tooth with Apical Periodontitis after Regenerative Endodontic Treatment.

Specimens of human immature permanent teeth after regenerative endodontic treatment (RET) are sparse. This case report describes the histologic and immunohistochemical findings of tissue formed in the canal space of a human immature permanent tooth with apical periodontitis after RET. A patient presenting with immature human permanent tooth #29 with apical periodontitis underwent RET. At the 10-month follow-up visit, radiographic examination revealed complete resolution of the periapical lesion, marked narrowing of the apical foramen, increased thickness of the canal walls, and minimal lengthening of the root. Notably, the tooth regained pulp sensibility. Tooth #29 was extracted for orthodontic reasons and processed for histologic and immunohistochemical examination. The canal space was filled with newly formed cementumlike tissue, bonelike tissue, and fibrous connective tissue. The apical closure, thickness, and length increment of the root were caused by the deposition of cementumlike tissue without dentin. Furthermore, neurons and nerve fibers were observed in the canal space; this observation was confirmed by immunohistochemistry. Based on the findings in the present case, after RET, the newly formed tissues in the canal space of the human immature permanent tooth with apical periodontitis were primarily fibrous connective tissue, cementumlike tissue, and bonelike tissue. Nerve regeneration was identified.