Stem cells, tissue engineering and periodontal regeneration.

The aim of this review is to discuss the clinical utility of stem cells in periodontal regeneration by reviewing relevant literature that assesses the periodontal-regenerative potential of stem cells. We consider and describe the main stem cell populations that have been utilized with regard to periodontal regeneration, including bone marrow-derived mesenchymal stem cells and the main dental-derived mesenchymal stem cell populations: periodontal ligament stem cells, dental pulp stem cells, stem cells from human exfoliated deciduous teeth, stem cells from apical papilla and dental follicle precursor cells. Research into the use of stem cells for tissue regeneration has the potential to significantly influence periodontal treatment strategies in the future.

Interactions of the tooth and bone during development.

The tooth works as a functional unit with its surrounding bony socket, the alveolar bone. The growth of the tooth and alveolar bone is co-ordinated so that a studied distance always separates the 2, known as the tooth-bone interface (TBI). Lack of mineralization, a crucial feature of the TBI, creates the space for the developing tooth to grow and the soft tissues of the periodontium to develop. We have investigated the interactions between the tooth and its surrounding bone during development, focusing on the impact of the developing alveolar bone on the development of the mouse first molar (M1). During development, TRAP-positive osteoclasts are found to line the TBI as bone starts to be deposited around the tooth, removing the bone as the tooth expands. An enhancement of osteoclastogenesis through RANK-RANKL signaling results in an expansion of the TBI, showing that osteoclasts are essential for defining the size of this region. Isolation of the M1 from the surrounding mesenchyme and alveolar bone leads to an expansion of the tooth germ, driven by increased proliferation, indicating that, during normal development, the growth of the tooth germ is constrained by the surrounding tissues.

Dental follicle progenitor cell heterogeneity in the developing mouse periodontium.

As a developmental precursor for diverse periodontal tissues, the dental follicle (DF) harbors great promise for periodontal tissue regeneration. However, development of optimal therapy awaits the answer to a key question that impinges on many issues in development-Do adult progenitor tissues form a homogeneous cell population that differentiates into target tissues when they arrive at the site, or they contain heterogeneous cell populations that are committed to specific fates? To address the homogeneity/heterogeneity question, we analyzed differentiation pathways and markers in several cloned DF cell lines. Our studies revealed that each of our cloned DF lines featured remarkably unique characteristics, indicative of a separate and distinct lineage. One line, DF1, was high in proliferative activity but did not display any mineralization behavior, suggesting that it might be related to a periodontal ligament-type lineage. DF2 was similar to DF1, but featured remarkably high alkaline phosphatase activity indicative of a highly undifferentiated state. DF3 matched the mineralization characteristics of a same stage alveolar bone line AB1 in terms of gene expression and von Kossa staining, indicating that DF3 might be of cementoblastic or alveolar bone osteoblastic lineage. To verify the multilineage potential of the DF for purposes of tissue engineering, a series of differentiation induction experiments was conducted. For identification purposes, characteristics of these heterogeneous follicular progenitor cells were compared with follicle components in tissue sections of the postnatal developing periodontium. The presence of heterogeneous cell populations in the DF mirrors individual developmental pathways in the formation of the dental integument. The profound cellular heterogeneity of the DF as an adult progenitor for tissue regeneration also suggests that heterogeneous cellular constituents might play as much of a role in tissue regeneration as the inducible characteristics of individual lineages might do.

Algunas consideraciones con relación a la dimensión biológica del periodonto. Sinonimia: espesor biológico - espacio biológico / Some considerations related to the periodontium's biological dimension. Synonymy: biological thickness - biological space

En este artículo se realiza una recopilación sobre algunos aspectos del denominado espacio, espesor o dimensión biológica del periodonto, también denominado unión dentogingival, desde la formación y desarrollo, la participación de los tejidos embrionarios, ectodermo, mesodermo y endodermo y la subsecuente evolución de la cuarta capa embrionaria denominada ectomesénquima. El resultante gingival final, luego de la erupción del diente permanente desde el punto de vista clínico, radiográfico, histológico y quirúrgico, con el fin de reconocer los límites calcificados de esta dimensión y los componentes de tejido blando epitelial y conectivo, así como sus dimensiones clínicas e histológicas. Una recopilación de los factores que lo alteran tanto genéticos como adquiridos los cuales modifican sus dimensiones superficiales, creviculares y subcreviculares. Los métodos de reconocimiento clínico del espesor crevicular, profundidad sondeable, el daño que haya causado la patología nivel de unión, parámetros utilizados también en la evaluación del resultado de los diferentes procedimientos terapéuticos y también necesarios para establecer la evolución favorable o desfavorables de un caso en un período de tiempo. Se revisan someramente los aspectos patológicos asociados con la enfermedad periodontal inflamatoria de origen bacteriano (periodontitis), con relación a los daños causados en la superficie blanda, dura y la profundidad de la dimensión crevicular (bolsa periodontal). Por último se describen las diferentes opciones de resolución de la bolsa peridontal por: a) Regeneración (neoformación tejidos perdidos). b) Reparación (cicactrización) de la dimensión biológica, según los hallazgos de la investigación en animales y humanos al utilizar las diferentes técnicas descritas para el tratamiento de la bolsa periodontal