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CAD/CAM - international magazine of digital dentistry

I industry report _ diode lasers Fig. 10_Depiction of the form of the preparation, especially the level ranges on the monitor, after cutting less relevant aspects of the model situation image digitally. Fig. 11_Checking of the minimum layer depth for the future ceramic restoration is more practical than via the analogous model. Fig. 12_Articulation can be checked from various perspectives. Fig. 13_Production and checking of the optimum occlusal configuration. Fig. 14_Okklusal view of the digitally planned partial crowns. Fig. 15_In the end of the digital planning phase, the restoration can be checked from all special dimensions even before the milling process. 34 I CAD/CAM 4_2013 cal impression taking via scanner systems does not allowforthisoption. While optical impression taking systems make a contribution to standardization, direct control of the preparation outcome and thus to the quality of the impression, conventional as much as digital optical impression taking can only capture structures which arevisibletothehumaneye.Opticalimpressiontaking cannot replace conventional impression taking tech- niques completely. This holds true especially for re- movable and complete dentures as well as circular implant suprastructures. In addition, the transfer of virtual data into real-life working models, which is oftenmandatory,hasnotyetbeenperfected. However,thecurrenttrendisdigitalimpressiontak- ing,althoughmanyobstacleshaveyettobeovercome. A review of the literature and published reports shows that in most cases supragingival preparation marginsaretreated,whichsomecolleaguesmightbe able to take an impression from without any retrac- tioncords.Extensivehaemostasismeasurementsand tissue suppression can cause more trouble, since a camerawillonlybeabletoscanareasoptimallywhich are easily accessible. No optical system has been able to see through a pooling of saliva or offer usable data for an exact renderingofthepreparationmargin.Imprecisioncan accumulate between impression taking and final prosthesis.Thus,boththeadvantagesandtheprecise results produced by digital workflow would be taken ad absurdum. But the clinical, deeply subgingival preparation margin with bleeding of the adjacent gingiva (Fig. 2) can be a severe challenge for experienced clinicians using the traditional analogous impression tech- nique. Without cord techniques or astringent auxil- iaries,agoodresultishardtoachievefromimpression taking. Or is it? Twenty years ago, I have introduced high-fre- quency technology and shortly afterwards dental lasers to our praxis because of the high quality stan- dards in solving prosthetic problems by our team of cliniciansanddentaltechnicians.Especiallythecom- pact diode lasers can be applied effectively in this field. _Laser radiation Not only is laser radiation absorbed by the tissue and then transformed into heat, but it is also partly transmittedthroughthetissue.Thistakesplaceinde- pendently from the respective dental laser and de- terminestheindication.Thecuttingspeedofthelaser radiation is limited by the tissue, which can only be ablatedinlayers.Laserradiationproducedbytheden- tal laser is led to the application site in the oral cavity by fibre optic systems consisting of mirror joint arms and flexible glass fibres. Here, laser radiation from the anterior fibre heats the surface layer of the tissue in a closely-defined area, thus ablating the tissue. In order to reach deeper layers, the tissue must be ablated layer by layer. Although some authors see this as a disadvantage1 , this minimally invasive and tissue-conserving procedure is especially helpful in the sensitive cervical areas and in sulcus extension previous to impression taking.2 _Clinical Procedure The handpiece of the diode laser device (Fig. 1) is placedinthehandlikeafountainpen(Fig.1a).Withthe thinfibretip,thepreparationmarginistracedcircularly around the anchor tooth, either over its total circum- ference or only the gingival level range of the partial crown (Figs. 3–5), by using it like a fine fibre pen of adiameterofonly0.3mm. Fig. 14 Fig. 15 Fig. 11 Fig. 12 Fig. 13 Fig. 10