Rotating instruments used in the fields of dentistry and oral surgery operate at high speeds. Therefore, if small particles are projected and strike the orbit, injuries of varying severity can occur. We report here a case in which a broken dental bur pierced into the orbit. The bur fortunately did not damage the eyeball and stopped after penetration of the medial orbital wall. The subject was a 27-year-old dental assistant and not wearing protective eyewear. A foreign body had penetrated the medial wall of the right orbit and the tip had reached the ethmoid sinus. The medial orbital wall was exposed subperiosteally after dissection of the medial canthal ligament, and the foreign body was removed. Although the importance of protective eyewear had been advocated, eye protection compliance differed by region and dental personnel. Eye protection use needs to increase in not only dentists but also other dental personnel. Keywords: broken dental bur, eye protection, foreign body, occupational hazard, ocular injuries, orbital wall