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How is the “Dahl appliance” used in the treatment of severely worn maxillary anterior teeth prior to reconstruction?

This question was submitted by a general dental practitioner: Does anyone have experience with the “Dahl appliance” used in the treatment of a severely worn maxillary anterior teeth prior to reconstruction?

Dr. Effrat Habsha, Prosthodontist at Prosthodontic Associates offered this quick initial response: 

The Dahl Concept and the Dahl Appliance

The Dahl Concept refers to the relative axial tooth movement that is observed when a localized appliance or localized restorations are placed in supra-occlusion and the occlusion re-establishes full arch contacts over a period of time.

This concept can be achieved with a Dahl appliance, which refers to any interim restoration or prosthesis which deliberately introduces supra-occlusion of selected teeth with disclusion of the remainder.  It can either be a removable appliance or a fixed appliance, typically in the form of a composite resin restoration.

Dal Appliance

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The appliance may be used in clinical situations where there is significant anterior tooth wear, such as in the case of severe dental erosion, where there is insufficient interocclusal space for adequate restoration. With the use of a Dahl appliance, the necessary space is obtained by a combination of intrusion of the anterior teeth in contact with the appliance and eruption of the separated posterior teeth. Using a direct resin-based composite build-up, the Dahl appliance offers the benefits of creating appropriate interocclusal space, while at the same time offering immediate esthetic enhancement of the worn teeth.

Specific diagnostic records must be compiled and an appropriate and accurate diagnostic wax-up depicting the desired esthetic and functional outcome must be carried out. The tooth set-up established in the diagnostic wax-up is replicated and transferred to the mouth using a silicone matrix with direct intra-oral composite build-up. 

According to Poyser et al (2005), an ideal Dahl appliance should feature the following:

  • A thickness of material placed on the incisal/occlusal aspect of those teeth where the creation of interocclusal space is necessary
  • The thickness of this material should directly relate to the amount of inter-occlusal space that is required. This will determine the increase in the vertical dimension of occlusion as measured at that particular site in the mouth.
  • Stable inter-occlusal contacts should be provided and the appliance should not impede the movement of the discluded teeth.
  • Finally, an occlusal bite platform ensuring that the occlusal forces are axially directed is essential.

After a period of 6-9 months, posterior occlusal contacts are re-established. The literature reports that the objectives of the Dahl concept are achieved in the majority of cases (94%-100%) and that this space creation occurs irrespective of age and gender. Development of adverse events, such as initial difficulty with mastication, tends to be minor in nature and transient. Prior to initiating treatment, it is prudent to advise the patient that an alteration of the vertical dimension of occlusion will ensue as a result of treatment. Appropriate case selection and adherence to the requirements of a Dahl appliance are crucial in achieving predictable outcomes.  

Resources

Briggs PF, Bishop K, Djemal S. The clinical evolution of the ‘Dahl Principle’. Br Dent J. 1997;183(5):171-6.

Hemmings KW, Darbar UR, Vaughan S. Tooth wear treated with direct composite restorations at an increased vertical dimension: results at 30 months. J Prosthet Dent. 2000; 83:287-93.

Poyser NJ, Porter RW, Briggs PF, Chana HS, Kelleher MG. The Dahl Concept: past, present and future. Br Dent J. 2005;198(11):669-76.

Follow-up: What further information would you like on this topic? Email us at jcdaoasis@cda-adc.ca

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One comment

  1. The use of a composite Dahl appliance in prosthodontics is a routine procedure.
    Casts are mounted at increased vertical and diagnostic wax-up required. We routinely place Minikin pins on the distal and mesial of the upper anteriors, retraction thread and then a bonded composite overlay inside a thermoplastic shell of the wax-up. This is the only way to accommodate the loss of the palatal tooth structure for full crown restorations in the anterior where the bite has collapsed.

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