An occlusal splint or sometimes called night guard is mostly recommended to patients that are heavy grinders, or bruxes*.
Since most of the damage caused by teeth grinding is when we sleep, a splint ussually stops or prevent further damage.
The guard is custom made the upper or lower arch of the mouth. When the night guard is in place, the patient can not grind their teeth together and cause more damage.
The guard is worn during night maybe 4-5 nights a week and has been proved that they reduce the chance of fracture and tooth surface loss in the long run.
*Bruxism is the nocturnal unconscious grinding or gnashing of the teeth. It has been linked to stressful life events and occlusal or bite irregularities. Research shows that the maximun clench force capability during bruxism is up to 4 times the maximun conscious force in some subjects.