CDEN0210

I 41 feature _ interview I cosmeticdentistry 2_2010 of shades and implant systems is easier and more eco- nomical as well. Overall, production costs are very low andtheoreticallyoffersuperiorqualityatthesametime, which is something that needs to be considered when we speak of the time disadvantage. I anticipate that decentralised production will play a vital role in den- tistryforlargerrestorationssuchasfixedpartialcrowns andimplants. _The first IT systems that were available to dentists attheendofthe1970s/beginning1980swereexpensive mini-computers (VAX) that were never actually amor- tised. Will it be the same with CAD/CAM? What do you foreseepricedevelopmenttobe? An amortisation of CAD/CAM systems depends not onlyonthepossibilitiesandrangeofindications,butalso on clinical concepts and the patient base (for example, the number of ceramic restorations produced and the extent of the potential for this kind of treatment). This needs to be analysed case by case. Generally speaking, wehavealreadyundergonetheintroductionphaseand many CAD/CAM practices now demonstrate impres- sively that the system can actually be amortised quite well. Many companies have found CAD/CAM technol- ogytobeoneofthekeytechnologiesindentistrytoday, and large sums are invested in research and develop- ment,whichwillboostdevelopmentprocesses.Manyof these improvements can be incorporated into the sys- temslater,asalargepartoftheexpertiseisincorporated intosoftware.Therearelikelytobechangesinthehard- ware as well, but those will take much longer. Dentists thinking about investing in a CAD/CAM system should make their decision regardless of such considerations. After all factors—range of indication, user friendliness, testimonies of fellow colleagues, economic efficiency, and scientific approval—have been analysed, entry into theCAD/CAMworldclearlydoesmakesense.Intheshort and intermediate term, we do not expect a significant decreaseinprice.Butasascientist,Ialwayslookfarinto the future and am convinced that after the high devel- opment costs have been amortised, prices will have the potentialtodecreaseinthelongterm.Thevisionisthat someday every dental practice will own such a system. ITtechnologyisagoodexampleandCAD/CAMtechnol- ogy,whichisbasedonthisITtechnology,willfollowsuit. _iTero, 3M ESPE Lava COS, CEREC, E4D—How many pointsoflaserlightaretechnicallyrequired? For dental restorations, an accuracy of 50 µm is de- manded.Surprisingly,littleisknownabouthowcritical this level really is, but we apply this standard, and surfacesshouldbescannedwithagridofatleastcom- parable size. Double resolution (25 µm) would be even better. An average molar surface of 2 cm2 , for example, would yield 320,000 measuring points. The ideal num- berthendependsonthedataprocessing.Bycombining several scans, these numbers can be increased signifi- cantly. The software can then calculate the optimum distribution of measuring points, thereby improving theresultsevenmore. _LED (CEREC) versus laser (3M ESPE, iTero, E4D), parallel confocal imaging (iTero) versus triangulation (CEREC, 3M ESPE, E4D)—what are the advantages and disadvantages?Howmuchinterpolationisacceptable? These technical details principally influence accu- racyandclinicaladaptability.However,wecannotfully evaluate the quality of intra-oral scanners based on these details because they only constitute a small per- centage of the overall complex measurement systems. In addition, there is the decisive factor of software interplay. Clinical and scientific experiences of each measuringsystemarefarmoreimportant. _What are the advantages and disadvantages of digitalbiteregistrationversustraditionalbiteregistra- tionwithsubsequentmanualadjustment? Thesoftwareallowsamoreprecisepositioningofthe jawandasuperioranalysisoftheocclusioncomparedto theconventional,manualprocedureontheplastermodel, on condition that the digital impression ensures a high degreeofmeasurementaccuracyforthejawimpression. In addition to the controlling of the restoration material thickness, contact patterns can be analysed, 2-D slices can be adjusted for visualisation in different areas, and articulation movements can be measured. Using soft- ware, the resilience of teeth can be simulated, enabling newpossibilitiesfordiagnosisofthecontactsituation. _iTeroandE4Ddonotrequirepowdercoating.Why isn’tthispossiblewithCERECand3MESPE? Powder-free impressions are the preferred option. However, they still are a significant challenge in intra- oral scanning technology. Based on my experience, I am not able to evaluate whether this is possible with sufficientaccuracyatthepresentstage.Therearemany different approaches to analysing the light reflected from tooth surfaces without using powder; however, the accuracy of the measurement is dramatically re- duced. At the end of the day, it is the results that count anditisuptoustoanalysetheseclosely. _Do you believe that prostheses manufactured via rapid prototyping can be done in practice with better aestheticqualityandwithouttheassistanceofadental technician? Thereisdebateaboutwhetherthisispossible.While this procedure has become common in some milling centreswithregardtometalandacrylicresins,restora- tions with aesthetic materials such as dental ceramics and composites have shown some principal and un- resolved issues. Basic research is needed in this field. As a second step, production devices should be made compactsotheybecomemorecost-efficientfordental practices. In conclusion, this technology is unlikely to experienceamajorbreakthroughinthemediumterm._ Photo:Mehl