A coupling device for use with a dental appliance for mandibular repositioning, including: a first mount adapted for lateral attachment to a first splint with a generally forward facing axis with respect to the user of the dental appliance when in use; a second mount adapted for lateral attachment to a second splint of the dental appliance; and a link arm coupled to the first and second mount, the link arm extending transverse to said forward facing axis along a transverse axis in a transverse dimension to engage with said second mount in a slideable coupling that allows in use a range of relative movement in said transverse dimension, wherein the coupling allows for sliding movement along the transverse axis accompanied by free pivotal movement about the forward facing axis, protrusive positioning of a mandible being provided in use by relative positioning of the link arm along said forward facing axis; characterised in that the first mount is a pivot mount and the second mount is a fixed mount, the pivot mount allows for free pivotal movement about said forward facing axis, the pivot mount comprises a first connecting member with a forward facing axis and supports a position adjustment member; the fixed mount comprises a second connecting member and includes a spigot; the first and second connecting members are coupled to one another through the position adjustment member and the link arm; the link arm projects perpendicularly to an axis of the position adjustment member and comprises a slot opening for coupling with the spigot, the slot opening having a lateral extent to said position adjustment member axis, the width of the slot opening marginally larger than the diameter of the spigot so that movement of the second connecting member is relatively restricted in a direction parallel to the axis of the position adjustment member; the slidable coupling provided by the spigot located in the slot opening enabling the second connecting member to move relative to the first connecting member within the lateral extent of the spigot in the slot opening. a first mount adapted for lateral attachment to a first splint with a generally forward facing axis with respect to the user of the dental appliance when in use; a second mount adapted for lateral attachment to a second splint of the dental appliance; and a link arm coupled to the first and second mount, the link arm extending transverse to said forward facing axis along a transverse axis in a transverse dimension to engage with said second mount in a slideable coupling that allows in use a range of relative movement in said transverse dimension, wherein the coupling allows for sliding movement along the transverse axis accompanied by free pivotal movement about the forward facing axis, protrusive positioning of a mandible being provided in use by relative positioning of the link arm along said forward facing axis; characterised in that the first mount is a pivot mount and the second mount is a fixed mount, the pivot mount allows for free pivotal movement about said forward facing axis, the pivot mount comprises a first connecting member with a forward facing axis and supports a position adjustment member; the fixed mount comprises a second connecting member and includes a spigot; the first and second connecting members are coupled to one another through the position adjustment member and the link arm; the link arm projects perpendicularly to an axis of the position adjustment member and comprises a slot opening for coupling with the spigot, the slot opening having a lateral extent to said position adjustment member axis, the width of the slot opening marginally larger than the diameter of the spigot so that movement of the second connecting member is relatively restricted in a direction parallel to the axis of the position adjustment member; the slidable coupling provided by the spigot located in the slot opening enabling the second connecting member to move relative to the first connecting member within the lateral extent of the spigot in the slot opening.