Temperature dependence of toothbrush bristle morphology An ultrastructural study

Abstract. In this study, it was demonstrated that the original forms of toothbrush bristle ends undergo morphological changes during the preparatory procedures required prior to their examination by scanning electron microscopy (SEM). In particular, the distance of the specimens from the cathode of a traditional sputter-coater and the time of gold-palladium coating influence the temperature inside the vacuum compartment. Morover, the temperature influences the original morphology of toothbrush bristles, 2 segments of each toothbrush head with nylon or ultralon bristles were cut off the brush: one was mounted vertically and one horizontally on stubs for SEM analysis. Different temperatures were measured inside the sputter-coater at the level of the bristle ends, during coating with gold-palladium alloy. The temperature at the level of the bristles that were placed horizontally was about 38°C, and 59°C when they were placed vertically. SEM analysis of the specimens showed that the same toothbrush has end-rounded bristles at about 59°C and non-acceptable irregular bristles at about 38°C. Retraction of bristles (which appeared shortened and with increased diameters) and superficial cracks were particularly present in the vertically placed ultralon bristles.