Restricted mouth opening and trismus in oral oncology

Restricted mouth opening (RMO) and trismus are terms commonly used in oral oncology in instances where there is difficulty in mouth opening. The term trismus in oral oncology is mainly used to indicate the radiation-induced fibrosis of the muscles of mastication. The treatment given for RMO as reported in the literature is given for muscular dysfunction trismus, whereas RMO in oral oncology can occur owing to various reasons other than muscular dysfunction. RMO occurs in various conditions of the oral cavity; in posterior pharyngeal infection, where it is termed reflectory trismus; in oral submucous fibrosis; in oral mucosal disorders; in the use of certain drugs; and in minor dental procedures of the posterior oral cavity. The usage of the term trismus in all RMO cases would complicate the treatment; thus, the word should not be used in all RMO cases.