1. A flow cell comprising: i) an inlet channel having an inner hole that extends from the inner hole and extends outwardly of the flow cell； ii) an outlet channel hydraulically connected to the inlet channel； and iii) at least one dentin sample reversible fixation mechanism for fixing the dentin sample between the inlet and outlet channels, wherein the dentin sample fixation mechanism comprises a fixation mechanism and at least one washer located adjacent to the fixation mechanism for receiving the dentin sample, this washer has at least one flat side for contact with the dentin sample. 2. The flow cell according to claim 1, wherein the washer has at least one pair of flat sides, wherein one of the sides is opposite or substantially opposite the other flat side, wherein one of the flat sides is in contact with the dentin sample and the other flat side of pairs of flat sides are in contact with at least one locking mechanism. 3. The flow cell according to claim 2, wherein the washer is a square O-ring. 4. A flow cell according to claim 1, wherein the washer contains a material selected from the group consisting of silicone, rubber, plastic, or a mixture thereof. A flow cell according to claim 4, wherein the washer contains rubber. 6. A flow cell according to claim 1, further comprising a discharge duct that is adapted to receive air in the form of at least one air bubble that can accumulate under the dentin sample fixed in the locking mechanism after the fluid has been introduced into the flow cell in the inlet duct. A flow cell according to claim 1, further comprising an additional1. Проточная кювета, содержащая:i) впускной канал, имеющий внутреннее отверстие, который отходит от внутреннего отверстия и продолжается наружу проточной кюветы；ii) выпускной канал, гидравлически соединенный с впускным каналом； иiii) по меньшей мере один механизм обратимой фиксации образца дентина, предназначенный для закрепления образца дентина между впускным и выпускным каналами, при это
