The Dahl concept is the relative axial tooth movement that is observed when a localised appliance or localised restorations are placed in supra-occlusion and the occlusion re-establishes full arch contacts over a period of time.[2] It involves the vertical tooth movement that occurs when anterior localised appliances/restorations are placed in supra occlusion causing the posterior teeth to disclude. Rather than restoring occlusion by means of restoration, it is allowed to re-establish over time through a combination of intrusion and over-eruption. This, in turn, will increase the OVD.