Читать книгу Caries Excavation: Evolution of Treating Cavitated Carious Lesions - Группа авторов - Страница 18

When the odontoblastic barrier is destroyed by the carious lesion and either bacteria or their toxins reach the underlying pulp, a tertiary dentine secretion can still be observed. This dentine, which is secreted after the odontoblast destruction, is synthesised by another cell type originating for the differentiation of adult pulp stem cells. This reparative dentine usually contains fewer tubules than the physiological one. This might decrease the bacterial infiltration or their toxins to the underlying pulp. While little was known about the cells secreting this dentine, the discovery of adult stem cells within the dental pulp provided a significant step forward. Indeed, all dental pulps in permanent and primary teeth and at all ages comprise, at least, a population of adult stem cells [28]. This was first demonstrated in a culture system of cells isolated from the pulps of third molars, where pulp cells were able to produce a mineral matrix with molecular and mineral characteristics of dentine [29]. Additionally, when isolated with specific mesenchymal stem cell markers such as STRO-1 and transplanted after mixing with hydroxyapatite/tricalcium phosphate ceramic powder subcutaneously in mice, they generated a dentine/pulp-like tissue [30]. There is converging evidence that one of the niches of these stem cells is located in the perivascular area. After pulp injury, these cells are activated and migrate to the injury site to synthesise the tertiary dentine [31]. It has been reported that TGF-β₁, which can be released after the dissolution of dentine, is involved in the recruitment of these cells and their differentiation into odontoblast-like cells secreting the tertiary dentine [32].

Fig. 3. a Histology of a moderate carious lesion in a molar. It is characterised by a disorganised dentine with a loss of the typical tubular structure at the carious site. b Tertiary dentine is secreted locally by the underlying odontoblasts (od). At this stage, bacterial infiltration is arrested at a distance from the pulp, which has a normal aspect.

Additionally, recent investigations on dental pulp, which has a terminal circulation, revealed that, in addition to the systemic regulation, it has a local regulation of its vascularisation, inflammation, and regeneration. This allows the dental pulp to resist bacterial invasion by different mechanisms, as explained below.