Lymph drainage in the human dental pulp

Abstract

We investigated which structural components are responsible for maintaining interstitial fluid equilibrium in the pulpal tissue, for which the existence of an effective lymph drainage is postulated. There have been only a small number of investigations on pulpal lymph tissue. Therefore, we decided to perform a detailed structural analysis. Twenty vital, healthy teeth that had to be extracted for orthodontic reasons were immersed in Patent Blue for 10 to 15 minutes after opening the pulpal cavity. They were then extracted and the dental pulps were opened by cleavage of the surrounding hard tooth structure. Subsequently, the specimens were prepared for light and electron microscopic investigation. A clear blue ring of stain was detected by light microscopy in Weil's zone in the coronal region of the pulp, the cell-rarefied layer surrounded by the odontoblasts. No dye deposition was observed in the apical part. However, using transmission electron microscopy, capillary structures with typical morphological characteristics of lymphatic vessels were found apically. The coronal part of the pulp did not reveal any such vascular structures. It may be concluded from these findings that the lymph in the coronal region is collected in interstitial tissue clefts and drained towards the apex, whence it is further transported via lymph capillaries.

The lymphatic vascular system of the mouse head

“…Some groups claim that a lymphatic drainage system exists in the dental pulp of diverse species. Various immunohistochemical methods, immersion of teeth in Patent Blue and ultrastructural analyses by electron microscopic techniques have been used to verify this hypothesis (Bernick 1977; Bishop and Malhotra 1990; Marchetti et al 1991; Matsumoto et al 2002; Oehmke et al 2003). Nevertheless, more recent studies in this field utilizing immunohistochemical staining with the common LEC markers Lyve-1, Prox1, VEGFR-3, or D2-40 have been unable to detect lymphatic structures in the human or dog dental pulp (Gerli et al 2010; Martin et al 2010).…”

Absence of lymphatic vessels in human dental pulp: a morphological study

“…(48), we propose that true lymphatic vessels are not normally present in human dental pulp, but that they may appear following inflammation. Under normal conditions the interstitial fluid that was not re‐absorbed on the venular side, would flow via ‘non‐endothelialized interstitial channels’, as reported in an analysis of the crown region (49), through the extracellular matrix to the root canal and leave the tooth through the apical foramina. The interstitial fluid would reach the periodontal ligament region, where lymphatics have been found in animals by S taszyk et al.…”

Absence of lymphatic vessels in the dog dental pulp: an immunohistochemical study

“…However, it agrees with the results of other investigations that denied or questioned the existence of lymphatic vessels in the dental pulp of dogs (see Table 1). It is noteworthy that none of the previous studies in the dog used specific methods, e. g. electron microscopy, enzyme‐histochemical procedures or application of immunohistochemical markers, which are accepted as proving the existence of lymphatic vessels (Oehmke et al. 2003).…”

“…However, pulpal tissue drainage via blood vessels or lymph capillaries, which are temporarily formed in response to inflammatory stimuli, has been regarded as a possible but physiologically unfavorable option of normal tissue clearance (Oehmke et al. 2003).…”

“…Instead, a lymph drainage model for human teeth has been supposed, consisting of two different constituents of the lymphatic pathway, i.e. tissue clefts that collect interstitial fluid and macromolecules in the coronal part of the pulp and lymphatic vessels that receive the lymph fluid in the apical area of the pulp (Oehmke et al. 2003).…”