A periodontist is a dental specialist who focuses on the prevention, diagnosis, and treatment of diseases that affect the GUMS and other structures that support the teeth. The concern of a periodontist is the health of the GUMS, which can be affected by GUM disease. The two solutions to the crossword for the term 'periodontist's concern' are GUMS (4 letters) and GUM (3 letters). GUMS are the soft tissue around the teeth that provide support and protection, while GUM disease is an infection of the GUMS caused by bacteria.