(a) The parent or guardian of a child younger than 18 years of age may be present in the treatment room during the child's dental treatment or procedure, unless the dentist determines in the dentist's professional judgment that the presence of the parent or guardian in the treatment room is likely to have an adverse effect on the treatment of the child. The decision to exclude the parent or guardian must be documented in the patient's record.(b) In this section, "parent or guardian" includes a person authorized by law to consent for the medical or dental treatment of a child younger than 18 years of age.