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The apical papilla is a stem cell rich tissue located at the base of the developing dental root and is responsible for the progressive elongation and maturation of the root. The multipotent stem cells of the apical papilla (SCAP) are extensively studied in cell culture since they demonstrate a high capacity for osteogenic, adipogenic, and chondrogenic differentiation and are thus an attractive stem cell source for stem cell-based therapies. Currently, only few studies are dedicated to determining the role of the apical papilla in dental root development. In this review, we will focus on the architecture of the apical papilla and describe the specific SCAP signaling pathways involved in root maturation. Furthermore, we will explore the heterogeneity of the SCAP phenotype within the tissue and determine their micro-environmental interaction. Understanding the mechanism of postnatal dental root growth could further aid in developing novel strategies in dental root regeneration.

AIM: Apart from other biomarkers isolated in the synovial fluid, alpha-defensin appears to be a promising diagnostic tool to confirm a periprosthetic joint infection (PJI) in the hip or knee. The purpose of this study was to evaluate the sensitivity and specificity of an alpha defensin lateral flow (ADLF) test compared to usual standard classifications in the diagnostic management of PJI. METHOD: This investigation was set up as a multicenter prospective cohort study. Synovial fluid was obtained by means of joint aspiration or intra-operative tissue biopsies. A presumptive PJI diagnosis was made according to criteria outlined by the Musculoskeletal Infection Society (MSIS), the Infec¬tious Diseases Society of America (IDSA) and the European Bone and Joint Infection Society (EBJIS). The intention to treat by the surgeon was logged. Sensibility and specificity for the ADLF test was plotted for each aforementioned diagnostic algorithm. Spearman correlations between all scores were analyzed. Multiple logistic regression was used to determine the contribution of independent variables to the probability of PJI. RESULTS: Hundred thirty six patients with a painful arthroplasty were assessed for infection and rated by the treating surgeon as potentially infected or not on the basis of clinical and laboratory in¬formation. According to the EBJIS criteria sixty-eight patients were deemed infected, fifty according to the IDSA criteria, forty one according to the MSIS criteria and forty according to the ADLF test. However, the sensitivity of ADLF test was 87.8% for MSIS, 70% for IDSA and 55.8% for EBJIS. The specificity of ADLF test was between 94% - 97%. Good correlation was observed between synovial fluid culture and ADLF test (r = 0.73). Low to excellent correlations between the ADLF test and the EBJIS (r = 0.58), IDSA (r = 0.68), and MSIS score (r = 0.84) were observed. The surgeon’s intention to treat correlated well with the MSIS score (r = 0.86), and moderately with the EBJIS (r = 0.59). CONCLUSIONS: ADLF test sensibility was variable, but its specificity was excellent. Most of the cas¬es, not retained by MSIS but classified by EBJIS as infected, got a negative microbiological result. Considering an accepted 20% negative microbiological result rate in PJI diagnostic, EBJIS is clearly overestimating the number of infected cases. MSIS score correlates with the surgeon intention to treat and ADLF test.

INTRODUCTION. Le test « lateral flow » pour l’alpha défensine (ADLF) semble disposer d’une grande sensibilité (97.1%) et spécificité (98.6%)1. Cette affirmation est contestée par d’autres avec des valeurs de sensibilité bien moindre (54%)2. Comment des taux aussi divergents peuvent-ils être observés et est-ce lié à la manière de définir l’infection ? MÉTHODE: une étude de cohorte prospective multicentrique pour établir la sensibilité et la spécificité de l’ADLF dans le bilan de prothèses douloureuses comportait 136 patients, dont 49 ont été traités comme infectés. Chaque patient a été classifié selon le score MSIS, IDSA et les critères proposés par l’EBJIS. La sensibilité et la spécificité de l’ ADLF a été évaluée pour chaque algorithme de diagnostic. Les corrélations de Spearman entre tous les scores ont été analysées. Une régression logistique multiple a été utilisée pour déterminer la contribution de variables indépendantes à la probabilité d’une infection de prothèse. RÉSULTATS. Selon les critères EBJIS, 68 patients ont été jugés infectés, 50 selon l’IDSA, 41 selon les critères MSIS et 40 selon le test ADLF. La sensibilité du test ADLF était de 87,8% pour MSIS, 70% pour IDSA et 55,8% pour EBJIS. La spécificité du test ADLF était comprise entre 94% - 97% pour tous les scores. Une bonne corrélation a été observée entre la culture de liquide synovial et le test ADLF (r = 0,73). Des corrélations faibles à excellentes ont été observées entre le test ADLF et l’EBJIS (r = 0,58), IDSA (r = 0,68) et le MSIS (r = 0,84). L’intention du chirurgien de traiter corrélait bien avec le score MSIS (r = 0,86), et modérément avec l’EBJIS (r = 0,59). Le comptage des globules blancs (GB) sur le liquide synovial s’est avéré le mieux corrélé à l’obtention d’une culture positive, avec des valeurs seuils de 1000 à 3000 GB. CONCLUSIONS. La sensibilité du test ADLF est variable, selon le référentiel choisi, mais sa spécificité est excellente. La plupart des cas non retenus par le MSIS mais classés par l’EBJIS comme infectés ont eu un résultat microbiologique négatif. Soit le score EBJIS surestime le nombre de cas infectés, soit il attire l’attention sur des situations où la microbiologie nous fait encore défaut. Le test ADLF ne permet pas de confirmer le diagnostic si l’EBJIS et IDSA sont pris comme référence

Within the field of tissue engineering, natural tissues are reconstructed by combining growth factors, stem cells, and different biomaterials to serve as a scaffold for novel tissue growth. As adequate vascularization and innervation are essential components for the viability of regenerated tissues, there is a high need for easily accessible stem cells that are capable of supporting these functions. Within the human tooth and its surrounding tissues, different stem cell populations can be distinguished, such as dental pulp stem cells, stem cells from human deciduous teeth, stem cells from the apical papilla, dental follicle stem cells, and periodontal ligament stem cells. Given their straightforward and relatively easy isolation from extracted third molars, dental stem cells (DSCs) have become an attractive source of mesenchymal-like stem cells. Over the past decade, there have been numerous studies supporting the angiogenic, neuroprotective, and neurotrophic effects of the DSC secretome. Together with their ability to differentiate into endothelial cells and neural cell types, this makes DSCs suitable candidates for dental tissue engineering and nerve injury repair.