Oral splints have been frequently used in the treatment of bruxism to protect teeth and periodontium from damage, but the mechanism of action and efficacy of oral splints remain controversial. It has been suggested that they can be used to treat bruxism, based on the assumption that the device can eliminate or remove occlusal interference. Currently there are no reliable data to support the assumption of occlusion as an etiologic factor for bruxism, because several other factors have a role in bruxism, such as psychiatric, neurological and systemic disorders. In this paper, the mechanism of action and efficacy of oral splints in bruxism are discussed. Conclusions: although oral splint may be beneficial in protecting the dentition, the efficacy of this device in reducing bruxism is still not confirmed. There are several aspects that would support the broad usage of oral splints in the treatment of bruxism, but there are also limitations associated with each of these aspects. In conclusion, oral splints can be considered as useful adjuncts in the management of sleep bruxism but not as a definitive treatment.