1-5-1d ... (5) A tooth and mouth protector (intraoral) which shall include an occlusal (protecting and separating the biting surfaces) and a labial (protecting the teeth and supporting structures) portion
and covers the posterior teeth with adequate thickness. It is recommended the protector be properly fitted and:
I am not a Dentist and I did not stay in a Holliday Inn Express last but, the following comes from
posterior teeth - definition of posterior teeth in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia.
posterior teeth - the teeth in the posterior parts of the dental arches; the premolars and molars.
Illegal if they "cut it down" and all teeth are not covered.