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Dental Tribune Middle East & Africa Edition | 6/2016 18 restorative Advanced Restorative Techniques and the Full Mouth Reconstruction. The Dahl Appliance. Part Six ByProf.PaulA.Tipton,UK Bjorn Dahl first described the Dahl appliance in the early 1970's. Since thentheyhavegraduallybeenincor- porated into the field of restorative dentistry, although many ortho- dontists still dispute their efficacy and relevance. This article will cover its usage in today’s modern restora- tive dentistry techniques, focusing on the use of the traditional chrome cobalt ‘Maryland wings’ style of ap- pliance to the use of splinted tempo- raryorprototyperestorationsandto definitive restorations used to gain spaceduringrestorativeprocedures. Dahl proposed creating space in the treatment of localised anterior tooth wear by separating the posterior teeth through an anterior bite plane for about four to six months. A com- bination of passive eruption (pos- terior teeth) and intrusion (anterior teeth) allowed the re-establishment of posterior occlusion while main- tainingtheanteriorspace.Dahlorigi- nally used a cast metal appliance to separate posterior teeth. The same goal can be achieved today using provisional restorations or adhesive dentistry (direct resin composites) and can be used to create similar spaceposteriorly. Toothsurfaceloss Tooth surface loss (TSL) is a normal, physiological process that occurs throughout life. Depending on the rate of wear, this physiological pro- cess can be described as a pathologi- cal one if it occurs rapidly and/or if it is accompanied by acid erosion – as in acid regurgitation at night, bulimia, fizzy drinks consumed ex- cessively,etc. In the majority of patients, TSL is ac- companied by dento-alveolar com- pensation, including alveolar bone growth and cementum deposition. These physiological compensatory processes ensure that, for the major- ity of patients, occlusal contacts are maintained in order to retain the ef- ficacy of the masticatory apparatus. This lack of interocclusal space pre- sents a problem for the restorative dentist. One approach is to conform to the existing intercuspal position (ICP) and create the necessary interocclus- alspacebyfurtherocclusalreduction ofthewornteeth.Occlusalreduction of already worn teeth may lead to a lack of axial height and thus insuf- ficient retention and resistance for conventional restorations. Perioden- tal crown lengthening procedures will aid retention but, unfortunately, introduceotherdisadvantages. Tooth preparation and the associ- ated loss of coronal tissue can risk further insult to the pulp and limit the options for future restoration replacement and many patients do notenjoythissurgicaloption. An alternative approach is to create the necessary space by reorganis- ing the occlusion by means of an increase of the vertical dimension of occlusionbutmanywillrequireafull mouth reconstruction. A different variation involves reconstruction of the occlusion to a retruded contact position (RCP) in a case where there is a large horizontal slide from RCP toICP. Orthodontic appliances can be used to create sufficient interocclusal space by a combination of relative vertical and horizontal bodily move- ments and a change in the axial in- clination of the teeth. These compre- hensive and specialised techniques may be more appropriate when oth- er features of the occlusion require treatment such as anterior crowding ormidlinechanges. A typical example of this is shown in Figures 1 to 6. This 55-year-old lady was referred by the GDP because of the wear on her lower anterior teeth and for the replacement of the miss- ing upper left canine tooth and cor- rection of the associated centre line discrepancy. In this instance, traditional ortho- donticsnotonlycorrectedthecentre line but also moved the upper ante- rior teeth upwards, creating space for the restoration of the worn lower anteriorteeth. AnteriorDahlappliance A typical example of a Dahl appli- ance is shown in Figures 7 to 11. The patient was a 35-year-old man who was referred by his GDP with exten- sive erosion of the palatal surfaces in the upper anterior teeth to a degree that he was concerned about the sensitivity of the teeth. Although all teeth had a degree of tooth wear, only the upper anterior teeth were worn sufficiently to justify interven- tion. A nickel chromium fixed Dahl appli- ance covering the palatal surfaces of alltheupperanteriorteethwasmade on a working model articulated with a lower model in the terminal hinge axis position. The interocclusal dis- tancewasincreasedbyraisingthein- cisal pin point on the articulator and the appliance waxed up to produce an occlusal platform at right angles to the long axis of the lower incisor teeth. The cast appliance was then sandblasted and cemented to the teeth with glass ionomer cement. The appliance was adjusted to estab- lishevencontactofallloweranterior teeth in occlusion with the Dahl ap- pliance and it was confirmed that none of the posterior teeth made contactinanyexcursionoftheman- dible. There was no problem with retention of the appliance through- out the active phase of treatment, even though the amount of enamel around the exposed dentine on the palatalsurfacesoftheteethwasmin- imal. An alternative approach could have been to do a similar treatment using direct composite, splinting the anteriorteeth. After 12 weeks, the posterior teeth had fully erupted until occlusion, allowing for removal of the Dahl ap- plianceandrestorationoftheeroded In part six of the series, Paul Tipton provides an insight into the Dahl concept by discussing the use of the appliance in today’s modern restorative dentistry techniques Figure 1: Over erupted upper anterior teeth and cen- trelineshift Figure9:NickelchromiumDahlappliance Figure13:Pooraestheticsmile Figure5:Finalsmile Figure6:Finalfullfaceview Figure2:Traditionalorthodonticstoalignandintrude Figure10:Dahlappliancecementedonto the teeth Figure14:Wornspacedupperanterior teeth Figure3:Lowerworn teeth Figure11:Spaceacquiredusing theDahlappliance Figure15:Palatalweardue tobulimia Figure7:Wornpalatalsurfaces Figure4:Finalcaptekrestorations Figure12:Final‘empress’palatalveneers Figure16:Prototypesplintedcompositecrowns Figure8:Diagnosticwaxing ÿPage 19