LASER DOPPLER FLOWMETRY OF ORAL STRUCTURES: CAPABILITIES AND LIMITATIONS

Abstract

Preserving oral health is a crucially important area of medicine. One of the numerous functions of the oral cavity is that it serves as a first line of defence, forming a barrier between the internal and the external environment. Thus, an appropriate function of oral tissues is a pre-requisite for the healthy function of the entire organism. For the appropriate function of organs and tissues, a good supply of nutrients and oxygen is necessary. This is provided by the blood supply, and therefore knowledge of the microcirculation of particular organs is necessary for a proper understanding of their function. The first indicator of an injury is the change in microcirculation. Blood flow is regulated by local and systemic mechanisms. Vasoregulatory substances - three different small molecules (nitric oxide (NO), carbide monoxide (CO) and hydrogen sulfide (H2S)) are known to be endogenous gaseous mediators in the circulation - have a key role in local regulatory mechanisms.

Aims: To investigate the effects of gaseous mediators CO and H2S on the submandibular gland (SMG) and gingival (GIN) microcirculation in rats.

Methods: Gingival circulation and microvessel function can be studied using different methods. A non- invasive technique to study tissue blood flow is laser Doppler flowmetry (LDF), a sensitive, reproducible and harmless method that is widely used today. LDF can be used both in human studies and on experimental animals. Blood flow (BF) was measured by laser Doppler flowmetry on the exposed surface of right SMG and on the upper central papilla. BF changes were calculated as percentage of the baseline. In the first series of experiments a HO inhibitor (zinc deuteroporphyrin 2,4-bis glycol, ip. 45mM/kg) was given. In the second local dripping of 50mM H2S donor sodium hydrosulfide (NaHS) was applied directly on the SMG and GIN. The study was approved by the Animal Ethics Committee of Semmelweis University.

Results: The HO inhibitor did not change the SMG BF (89±3% of baseline, NS), but significantly decreased the GIN BF (56±10% of baseline, p<0.05). NaHS application significantly increased SMG BF (214±26% of baseline, p<0.001), but did not change GIN BF (110±7% of baseline, NS).

Conclusion: These data clearly indicate that endogenous H2S is involved in the adequate maintenance of basal submandibular perfusion, but not in gingival blood flow. On the contrary endogenous CO is a vasodilator in the gingiva, but not in the submandibular gland.