Dahl Concept

Definition

The Dahl concept is a method for creating prosthetic space in a limited region of the dental arch, without tooth preparation and without reconstructing the entire occlusion. In Bjørn Dahl's original description (1975), a removable metal bite plane was placed on the worn anterior teeth of the maxilla, so that in the closed position only the anterior teeth were in contact and the posterior teeth were taken out of occlusion. Over several months, posterior contact is re-established, and this return is the result of relative axial tooth movement: partly intrusion of the loaded anterior teeth, and partly (the larger share) supra-eruption of the unopposed posterior teeth. The result is fresh interarch space in the anterior region, into which the restoration is placed. In today's application, the restoration itself (usually direct composite on the palatal and incisal surfaces) typically plays the role of the fixed bite plane.

Concept Boundary & Misconceptions

The most common mistake is equating the Dahl concept with "raising the vertical dimension." What actually happens is a repositioning of the teeth within a living system, not simply adding height to the OVD. The space comes from tooth movement, not from cutting tissue, and not necessarily from a permanently higher OVD.

The second misconception concerns the biological requirement for this movement. Supra-eruption and intrusion depend on bone and periodontal ligament remodeling. Implants do not erupt, neither do ankylosed teeth, and a fixed posterior bridge behaves as a rigid unit. So in a patient whose posterior occlusion rests on an implant or a splinted fixed prosthesis, the Dahl logic does not work. This concept makes sense on an arch that is largely natural, with a healthy periodontium.

The third misconception is concern over patient tolerance. Discomfort, sensitivity, and transient changes in chewing and speech subside in most patients within the first few weeks, but this doesn't mean it's absolutely risk-free — the patient must be followed and checked regularly throughout treatment.

Role in Clinical Decision-Making

In localized anterior wear, compensatory eruption keeps pace with the advancing wear, and effectively no space is left for a restoration. The options on the table are limited: aggressive preparation (sometimes combined with elective root canal treatment), crown lengthening, orthodontic extrusion, full-mouth rehabilitation at a new OVD, or the Dahl concept. Choosing Dahl makes sense when the wear is localized and anterior, the periodontium is healthy, the posterior teeth are natural and mobile, and the patient has adaptive potential.

A point that's often overlooked is that Dahl is a solution for "space," not for "cause." If the source of erosion or parafunctional force isn't controlled, the anterior composite will fracture or wear again in the very space this method created. The Dahl concept doesn't borrow space from tooth structure — it borrows it from the biological adaptive capacity of the dental-jaw system, and wherever that capacity doesn't exist, the idea doesn't work either.