STUDY OBJECTIVES: Objective sleepiness is an important outcome requiring rigorous evaluation regarding OSA treatment efficacy, but no systematic review has explored the efficacy of advancement treatments of the stomatognathic system (ATSS), i.e. mandibular advancement device (MAD), hypoglossal nerve stimulation (HNS), and maxillomandibular advancement surgery (MMA), on objective sleepiness in OSA. METHODS: We conducted a systematic review of the literature using PubMed, Scopus and Web of Science databases. All clinical studies assessing the efficacy of ATSS on objective sleepiness in adults with OSA, by the maintenance of wakefulness test (MWT), the multiple sleep latency test (MSLT), the Oxford sleep resistance test (OSLER), the psychomotor vigilance task (PVT) or the sustained attention to response task (SART), were included. RESULTS: Among 42 screened studies, 11 were included - 6 randomized controlled trials (RCTs) and 5 prospective studies. Regarding the RCTs, all assessed MAD efficacy and only one RCT found a significant improvement of objective sleepiness for MAD compared with placebo, on the MSLT. In the remaining RCTs, the included participants did not present objective sleepiness at baseline and were mostly with mild/moderate OSA. Regarding the prospective studies, all found a significant improvement of objective sleepiness for each treatment assessed, i.e. MAD, HNS, MMA and submental stimulation. Interestingly, the included participants presented objective sleepiness at baseline and moderate/severe OSA. CONCLUSIONS: This systematic review highlighted the lack of RCTs assessing the efficacy of MAD or other ATSS on objective sleepiness in OSA. Further RCTs are needed to address this important outcome taking into account baseline objective sleepiness and OSA severity.< Réduire