Dahl effect

The Dahl effect or Dahl concept is used in dentistry where a localized appliance or localized restoration is used to increase the available interocclusal space available for restorations.

Method and concept

The Dahl Concept refers to 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.

The effect works by a combination of intrusion (40%) of the anterior teeth in contact with the appliance and eruption (60%) of the unopposed posterior teeth.

History

In 1962, D. J. Anderson from Guy’s Hospital Medical School, described the idea of manipulating occlusion by inducing over-eruption. This was achieved by placing bite-raising caps on certain teeth in the arch and observing the changes in distances between other teeth of opposing arches.[1]

However, in 1975, Bjørn L. Dahl from the Faculty of Dentistry of University of Oslo became the first author through a series of papers to report the successful use of the technique for the management of the worn dentition. Dahl, along with Olaf Krogstad and Kjell Karlsen, described this phenomenon where a Dahl appliance or anterior bite plane is used to increase the available interocclusal space available for restorations.[2][3]

A male, 18 year old patient with heavy wear on the palatal aspect of his dentition and no interproximal contacts in the anterior teeth was the subject of the experiment. A removable cobalt chromium platform was worn, which covered the upper palatal surface of the anterior teeth, while being held in place by clasps in the canine and premolar region. The appliance was worn for 24 hours each day over a 12 month period except for cleaning after every meal. This caused the premolars and molars of the patient to be propped open with the anterior teeth occluding the appliance.[2]

Clinical Application

The Dahl concept is commonly used when an increase in the interocclusal space is required together with an increase in occlusal vertical dimension ; for example when restoring a case of severe anterior tooth surface loss.
Typically, restoring the worn anterior teeth with dental composite to the original proportions will result in an increase in OVD, with the posterior dentition held apart out of the occlusion.

Adaptation occurs over a period of some months: compensatory eruption of the posterior teeth will occur, together with some intrusion of the anterior teeth and potential growth of the alveolar bone. This will allow the posterior occlusion to reestablish at the new increased OVD, stabilizing the increased interocclusal space.

Dentoalveolar tissues tend to compensate by remodelling when incisal/occlusal tooth surface loss has occurred to allow the teeth to regain a functional occlusion. A subsequent increase in the OVD with the Dahl approach could exceed the patient's tolerance and adaptive capacity. If the patient is unhappy with the height of their teeth and a Dahl approach cannot be tolerated then crown lengthening may be appropriate.

Dahl appliance

The original material used to construct Dahl's appliance was cobalt chromium. Now, many materials can be used to construct Dahl's appliance as long as the principles of technique are adhered to. A Dahl appliance should fulfil the following aims:

  • A thickness of material should be placed on the incisal/occlusal aspect of those teeth where the creation of interocclusal space is necessary. No mucosal-bone component should be involved
  • Thickness of the material placed should directly correspond to the required amount of inter-occlusal space, which will determine the increased in OVD as measured at specific site in the mouth.
  • An occlusal bite platform should be constructed ideally to ensure the occlusal forces are directed along the long axis of teeth.
  • Stable inter-occlusal contacts should be achieved.
  • Movement of the discluded teeth should not be impeded by the appliance.[3]

Advantages

The advantages of this approach are:

  • minimal removal of tooth substance is required to create the interocclusal space
  • lost OVD can be restored
  • minimisation of facial aging by restoring facial height
  • safety
  • relative simplicity
  • relatively reversible
  • relatively cost effective approach

Success of Dahl concept

Planned occlusal changes can be tested using a removable appliance prior to permanent treatment. Dental composite based approaches to tooth surface loss allow for easy adjustment or removal if required. One study published in the British Dental Journal, 2011 found that patient satisfaction was high when composite restorations were used in the Dahl approach and that the median survival time was between 4.75 and 5.8 years.[4]

See also

References

    1. ↑ Anderson, D.J. "Tooth movement in experimental malocclusion". Archives of Oral Biology. 7 (1): 7–15. doi:10.1016/0003-9969(62)90043-2.
    2. 1 2 Dahl, BJøRN L.; Krogstad, Olaf; Karlsen, Kjell (1975-07-01). "An alternative treatment in cases with advanced localized attrition". Journal of Oral Rehabilitation. 2 (3): 209–214. doi:10.1111/j.1365-2842.1975.tb00914.x. ISSN 1365-2842.
    3. 1 2 Poyser, N. J.; Porter, R. W. J.; Briggs, P. F. A.; Chana, H. S.; Kelleher, M. G. D. (2005-06-11). "The Dahl Concept: past, present and future". British Dental Journal. 198 (11): 669–676. doi:10.1038/sj.bdj.4812371. ISSN 0007-0610.
    4. ↑ Gulamali, A. B.; Hemmings, K. W.; Tredwin, C. J.; Petrie, A. (2011-08-27). "Survival analysis of composite Dahl restorations provided to manage localised anterior tooth wear (ten year follow-up)". British Dental Journal. 211 (4): E9–E9. doi:10.1038/sj.bdj.2011.683. ISSN 0007-0610.
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