Hematomas may involve the brain, organs, or any other part of the body but we are dealing strictly with the oral cavity. A dental hematoma is blood outside the blood stream and is usually caused by surgical trauma or a prick of the needle on a blood vessel. The condition usually subsides with no treatment. It may cause some swelling (ice may be used the first 24 hours) and bruising, but is usually nothing to be too concerned about.