This Patient Dental Health Education pamphlet from 1977 discusses oral injuries and mouth protectors in teenagers on page 8. The topic is the first one covered in the teen section—before malocclusion—and is even included in the section introduction.

From page 8: “The teen-age years are a critical time for oral health. Your child's permanent teeth, except the third molars or "wisdom teeth" are probably in position by 13 years of age. Unfortunately, it is during the teen-age years that decay occurs most often. And it is the permanent teeth that are damaged. Your teen-age child may also face problems of periodontal disease, malocclusion, and accidents. If your teenager is in sports, especially contact sports, it is essential to protect his or her permanent teeth.”