Which theory does the diagram depicts?

The dental pulp receives its blood supply through the so-called end arteries. These arterioles, entering the apical pulp, have a relatively low blood pressure, and the pressure drop from the arterioles entering the pulp to the venules leaving is only about one-fourth of the total arteriovenous pressure difference. Accordingly, a considerable part of the vascular resistance that regulates the pulpal blood circulation is located in the venules and also outside the pulp. This implies that changes in circulation in the neighboring adjacent tissues, such as the gingiva, alveolar bone, and PDL, will change the blood flow to the pulp because it will affect the feeding pulpal arterial blood pressure. Any vasodilation in tissues that receive their blood supply through side branches of the end arterioles feeding the pulp will, according to the Poisseuille law, steal blood pressure from the pulp. It should therefore be borne in mind that clinical treatment causing vasodilatation in adjacent tissues may decrease the circulation to the dental pulp.Thus, the mere application of a matrix may affect the pulpal circulation and cause a fall in pulpal blood flow. The pulp may become ischemic.