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9Dental Tribune Middle East & Africa Edition | September-October 2014 clinical Prof. Dr Masashi Miyazaki Nihon University School of Dentistry Department of Operative Dentistry 1-8-13, Kanda-Surugadai, Chiyoda-ku Tokyo 101-8310 Japan miyazaki-m@dent.nihon-u.ac-jp Contact Information CAD CAM Technology: a Review Dr. Kassis Cynthia., DDS, MSc Dr.KhouryPierre.,DDS,DESS Dr Tatiana Zogheib, DDS Dr. Hardan Louis., DDS CES PhD head of Esthetic and Re- storative Dentistry depart- ment ,USJ Prof. Mehanna Carina. , DDS CES PhD FICD Director of Es- thetic and Restorative Dentist- ry Postgraduate Program USJ, President of the continuimg Education committee, Leba- nese Dental Association C AD/CAM technology and materials are currently used in a number of clin- ical applications, including the fabrication of indirect restora- tions. CAD-CAM gives both the dentist and the laboratory an opportunity to automate fixed restoration fabrication. Both chairside and chairside – labo- ratory integrated procedures are available. The properties of these restorative materi¬als and their indications and ap- propriate use must be under- stood in order to enable the achievement of predictable and esthetic results for patients. KEYWORDS: CAD-CAM systems Intraoral scanner Digital impression Introduction In the past decade, the demand for all ceramic restorations has increased in both anterior and posterior teethand the search for materials with improved properties has expanded.1 The need for a uniform material quality, reduction in produc- tion cost, and standardization of manufacturing process has encouraged researches to seek to automate the manual pro- cess via the use of CAD- CAM technology since 1980.2 Computer-aided design (CAD) and computer-aided manufac- turing (CAM) technology sys- tems use computers to collect information and design, and to manufacture a wide range of products.3 The introduction of the first digital intraoral scan- ner for restorative dentistry was in the 1980s by a Swiss dentist, Dr. Werner Mörmann, and an Italian electrical engi- neer, Marco Brandestini, that developed the concept for what was to be introduced in 1987 as CEREC® by Sirona Dental Systems LLC (Charlotte, NC), the first commercially CAD/ CAM system for dental resto- rations.4,5 Ever since research and development sectors at a lot of companies have improved the technologies and created in-office intraoral scanners. All the existing intraoral scan- ners try to face with problems and disadvantages of tradition- al impression fabrication pro- cess and are driven by several non-contact optical technolo- gies and principles. The purpose of this present publication is to provide an extensive review on the CAD- CAM technology and to em- phasise on the application of this technology in restorative dentistry. CAD –CAM techniques The major goals of the impres- sion – taking process in restor- ative dentistry are obtaining a copy of one or several prepared teeth, healthy adjacent and an- tagonist teeth, establishing a proper interocclusal relation- ship and then converting this information into accurate rep- licas of the dentition on which indirect restorations can be performed.6 Traditional restorative tech- niques for fixed restorations require the use of impression materials to record the con- tours and dimensions of the preparation. This is followed by the pouring of stone models and dies prior to laboratory fab- rication of the definitive fixed restoration. Taking an accurate impression is one of the most difficult procedures in dentist- ry, requiring careful retraction or removal of soft tissue around preparation margins, hemosta- sis, and selection of an appro- priate impression material and tray for the technique used. By using a CAD/CAM restor- ative technique, a number of steps can be simplified or elim- inated.7 Digital systems now offer the opportunity to avoid tradi- tional, analog impressions, in- cluding the usual impression materials, time, and handling limitations associated with them. Intraoral scanners have the potential to offer excellent accuracy with a more comfort- able experience for the patient and more efficient workflow for the office. But care must be taken to ensure that the whole preparation is scanned, to avoid introducing errors. Two techniques can be used for CAD/CAM restorations: The chairside technique or the in- tegrated chairside-laboratory procedure. > Page 10 Fig. 10. Carbide burs are recommended for the removal of marginal overhangs. Fig. 11. Final polishing is performed with Astrobrush. Figs 12 and 13. The result is an esthetic posterior restoration without postoperative sensitivity. achieved by means of the pho- toinitiator Ivocerin® for exam- ple, which is employed by Ivo- clar Vivadent. Good mechanical properties such as high flexural strength and wear resistance are also important in order to make a composite resin suitable for use in occlusion bearing areas [8]. Tetric® N-Ceram Bulk Fill from Ivoclar Vivadent combines all of these qualities. This light-curing posterior composite has been specifically developed for the bulk-filling technique. Increments of up to 4 mm thick- ness can be cured in only 10 seconds at a light intensity of > 1,000mW/cm2. Tetric N-Ceram Bulk Fill con- tains four different types of fill- ers: a barium aluminium sili- cate filler, ytterbium trifluoride and mixed oxide. Additionally, a prepolymer filler (a shrinkage stress reliever) has been incor- porated which keeps polymeri- zation shrinkage and shrinkage stress to a minimum (Figs 1 and 2). It acts like a spring, dampen- ing the forces generated during polymerization. As a result, gap formation and marginal leakage are minimized, thereby helping to eliminate the risk of second- ary caries and postoperative sensitivity. The photoinitiator system in Tet- ric N-Ceram Bulk Fill includes conventional initiators as well as the polymerization booster Ivocerin. This polymerization booster ensures a reliable depth of cure in the deeper portions of the cavity after a relatively short irradiation time. A special light sensitivityinhibitorhasalsobeen incorporated which makes the composite resin less sensitive to ambient light and thus gives the clinician more time to apply and contour the restoration. Another useful quality of this material is its good polishability, which supports the achievement of a glossy surface, excellent resist- ance to wear in the contact ar- eas and a high flexural strength of 120 MPa. Moreover, Tetric N- Ceram Bulk Fill is highly radio- paque; therefore, the restorative result is easy to examine on den- tal radiographs. A clinical case The shade of the composite to be used should always be selected at the start of the appointment, i.e. before the rubber dam is placed. This prevents incorrect colour matching due to dehy- dration. After the carious tissue has been removed (Figs 3 and 4) and the adhesive has been ap- plied (Fig. 5), the entire restora- tiveprocedurecanbeperformed with Tetric N-Ceram Bulk Fill. As a consequence, a uniform restoration featuring homoge- neous strength is achieved. Because of the material’s nat- ural-looking translucency, the shade of the restored site will blend in with the remaining tooth structure. If stained sub- strate is visible within the cavity, < Page 8 the clinician may opt to place a layer of Tetric® N-Flow Dentin first. This material has a higher opacity and is thus capable of masking the darker colour of the underlying dentin. Although the incremental tech- niquehasbeenadvocatedforthe reduction of shrinkage stress, the composite resin described above is an ideal option for the restoration of deeper cavities us- ing the bulk-filling technique. The successive build-up tech- nique makes it possible to en- sure correct occlusal morphol- ogy through the incremental placement of composite. Thin- bladed placement instruments and special brushes are used to sculpt and contour the restored site. The composite is applied in bulk increments to rebuild each ana- tomic entity of the affected area. Each cuspal portion is recon- structed with one increment of composite resin, imparting to each of the cusps its adequate anatomical form. The size and location of the cav- ity determines the number of increments needed. Relatively small Class I cavities can be filled with a single bulk incre- ment. Medium-sized and large cavities are restored with several increments. Each cusp is rebuilt with an increment of maximum 4 mm thickness. Anatomical features of the oc- clusal surface should be taken into consideration during the ap- plication of the composite resin to mimic the natural tooth struc- ture. Insensitivity to light is a considerable advantage of Tetric N-Ceram Bulk Fill, as it ensures that sufficient time is available to shape and contour the resto- ration (Figs 6 to 9). If the composite resin is careful- ly placed using suitable instru- ments, only little time is required for the contouring and finishing of the restoration. Hand instru- ments such as LM Arte-Eccessa (LM Dental) are recommended for the removal of composite ex- cess. Marginal overhangs can be removed with carbide burs (Fig. 10). Composite finishers are then used to refine the anatomi- cal features. Polishing can be ac- complished with ease and in one step using Astrobrush® (Fig. 11). The result is an esthetic posteri- or restoration without postoper- ative sensitivity (Figs 12 and 13). Conclusion Direct composite resin resto- rations can be performed in a predictable and efficient way if an appropriate technique and advanced materials are used. As the understanding of the charac- teristics of new filling materials improves among clinicians, the quality of the direct restorations they fabricate will also increase. Tetric N-Ceram Bulk Fill with its many innovative features enables clinicians to restore posterior teeth in a much more efficient way. Proper attention to technological advances in the field of restorative therapy allows esthetic treatment to be provided that will satisfy not only the patient but also the dentist performing the restorative pro- cedure. Full list of references is avail- able from the publisher.