Trephine Burs do not have blade at center, thus it will be rather
difficult to get smooth cutting for a start. Enough exercise is
recommended before use. After Trephine Burs penetrate into
bone, then smooth cutting is available. To avoid choking on
bone inside Trephine Bur, pull of Trephine Burs up and down, so
that bone will always remain at patient. Remained bone can be
collected by surgical curettes. Enough cooling and possibly low
speed is recommended to avoid heat damage against bone.