Multiple clinical reviews and trials support the efficacy of myofunctional therapy and nasal dilators in improving airway function, reducing snoring, and managing mouth breathing during sleep.
Papers 1, 7, 9, and 10 provide positive evidence supporting the use of myofunctional therapy and/or nasal dilators (as part of combined airway therapies) in reducing sleep-disordered breathing, snoring, and mouth breathing. No retrieved papers contradict this claim.