Black & white drawing
Left - position of the brush, in labial brushing, on the cervical part of the crown and the gum, and the approximate right angle of the bristles before the beginning of the apical-ward part of the small circular stroke [...]. At this angle, it is possible for the bristle ends to effectively reach all the food debris within the gingivo-coronal embrasure. Right - the bristles at the end of the downward arc of a circular stroke, when they form an angle of approximately 45 degrees to the teeth and gums. With the brush at about this angle, the gingival surface is not apt to be abraded by the semi-rigid, attached halves of the bristles, as in Fig. 311 (left).
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