ohif-viewer/Packages/viewerbase/components/viewer/simpleToolbarButton/simpleToolbarButton.html

<template name="simpleToolbarButton">
    <button id="{{id}}" type="button" class="{{classes}} btn btn-sm btn-default" data-container="body" data-toggle="tooltip" data-placement="bottom" title="{{title}}">
        <span class="{{iconClasses}}"></span>
    </button>
</template>