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ePaper created 2017-01-24, 10:47:27 | version 1.38.0
08 I I clinical_ single-visit solution Marginsplaceddeeplysubgingivalarenotonlyan inflammatory irritant to the attachment apparatus3 but are difficult to scan due to both fluid and tis- sue deflection issues (Fig.6). When the practitioner presents the option of expedience made possible by CAD/CAM technology, it is difficult to predict or acknowledge possible complications in tooth preparationduetofactorssuchastoothpositionand variation in normal dental anatomy. From experience, STL files can be a challenge to accurately acquire and may lose accuracy4 with in- creasingfilesizeinsomecases.Therefore,toincrease acquisition of accurate scan data, prevent possible scan complications and shorten the treatment time, the five restorations would be divided and produced from two smaller files (Figs. 7a, 7b). Specifically, teeth #7-10 will be scanned, and #7 will be designed and milled followed by teeth #8-10 (Figs.8a,8b).Thenormallyidlemillingtimewasused to prepare tooth #6 and then scan this preparation with the milled #7 in place for an accurate contact and design landmark. The possibility of achieving a good quality clinical outcome with a single scan and designofallfiveteethsimultaneouslycouldcertainly have produced clinically acceptable result, but it would be less productive in terms of time manage- ment and without the improved accuracy. Tooth preparation design will influence whether the block is milled more quickly on a “standard” set- ting vs. on a “detailed” setting (Figs. 9a, 9b). Accord- ingly,teethshouldbepreparedwithscanninginmind anddesignshouldbecompletedwithmillinginmind: We scan to provide data for an accurate design, and wedesigntheproposalstomaximizetheparameters of the mill’s abilities. Anterior tooth preparations with incisal area dimensions smaller than the mill’s CAD/CAM 3_2016 Fig. 6 Fig. 7b Fig. 7a Fig. 8b Fig. 8a Fig. 6_Tooth preparations for teeth #6 –10 full contour, single unit e.max FDPs using a single-visit CAD/CAM procedure. Care was exercised to avoid damaging the gingival tissues as bleeding may prevent an accurate digital impression scan. Figs. 7a, 7b_Dividing the digital impression of the five teeth into two scan files results in a more efficient use of treatment time. Fig 7a: An occlusal view of #7–10 tooth preparations. Fig. 7b: The scan of #6 tooth preparation using #7–10 seated in lithium monosilicate phase as landmarks. Figs. 8a, 8b_Digital restoration design of tooth #7–10. Fig. 8a: To achieve a balanced esthetic appearance, the restorations should have a similar facial thickness of ceramic material on each central and lateral tooth where possible. Fig. 8b: Tooth preparation should be completed with restoration thickness in mind. JamesM.Stein,DMD,left,main- tains a private practice in Boston, Mass. He has been featured in TV, radio and print media for his work withsingle-visitCAD/CAMceramic crowns and veneers. He has pub- lished and lectured internationally on prosthodontics, implantology, cosmetics and CAD/CAM technol- ogy and has completed extensive clinical, surgical and technical training. He has been serving the Boston community through his pri- vate dental practice for 30 years. Brett E. Stein, DMD. completed his undergraduate education at Bowdoin College where he gradu- ated with a BA in biology in 2012. In 2016, he received his DMD fromtheUniversityofPennsylvania School of Dental Medicine, gradu- ating with honors in clinical den- tistry. He is currently completing his post-doctoral specialty training in the prosthodontics residency program at the Harvard School of Dental Medicine. CAD/CAM _about the author