THE EFFECT OF THE TOOTHBRUSH COVERS AND THE PRESENCE OF TOILET IN THE ENVIRONMENT ON BACTERIAL GROWTH ON TOOTHBRUSHES

摘要

This extended essay focuses on the effects of using toothbrush covers and the presence of toilets in the preserving environment on the bacterial growth on toothbrushes. Hence, the research question is: “How do the presence of toilet in the environment and the usage of toothbrush covers affect the bacterial growth on toothbrushes?”udTo test the hypothesis, which is “both the presence of toilet in the environment and the usage of toothbrush covers increase the bacterial growth on toothbrushes.”, total of 20 toothbrushes were used for a month by 5 different people, 4 toothbrushes for each person. Two of the toothbrushes were covered and the two of them were not. A pair consisting of one toothbrush from each group is put in a room without toilet and the other pair is put in a room with toilet. At the end of a month, the toothbrushes are taken to the laboratory and the bacterial growth on each of them is compared by the analysis of the data obtained at the end of the serial dilution and plate counting method. udIt is concluded that the usage of toothbrush covers increase the bacterial growth on the toothbrushes by providing a moist environment to the bacteria, when the presence of toilet in the environment does not affect it. However, because of an unexpected data result caused by the toothpaste remnants on the bristles of some toothbrushes, a different question is raised at the end of this experiment: “Does leaving some toothpaste remnants on the bristles of the toothbrush inhibit the bacterial growth?”