MANAGEMENT OF PROSTHETIC RESTORATIONS WITH THE CEREC SYSTEM

Transcription

1 Prosthetic dentistry MANAGEMENT OF PROSTHETIC RESTORATIONS WITH THE CEREC SYSTEM Mariana CONSTANTINIUC 1, Alina ZAHARIA 2, Alexandru-Victor BURDE 3, Daniela POPA 3, Sorana BACIU 1 1 Senior Lecturer, Iuliu Haţieganu UMPh, Cluj-Napoca 2 Lecturer, Iuliu Haţieganu UMPh, Cluj-Napoca 3 PhD student, Iuliu Haţieganu UMPh, Cluj-Napoca Contact person: Burde.Alexandru@umfcluj.ro Abstract The outcome of prosthetic restorations manufacturing in the field of dentistry and the remarkable functional results recorded depend equally on the accuracy of the clinical preparation and on the technology used. Currently, CAD-CAM systems represent the most advanced technology in restorative dentistry, which many practitioners consider to be the future of dentistry. This paper presents the operating procedure, the equipment and protocol used in the chair side and laboratory version of the CEREC system, summarizing the benefits it provides to both dental team and patients. Keywords: CEREC, computer, CAD CAM, milling, ceramics INTRODUCTION The unprecedented evolution noted in all fields of knowledge has allowed the digitalization of dentistry. Accordingly, restorative dentistry permanently enriches its therapeutic arsenal with new methods, the CAD-CAM system representing the latest advancement in digital dentistry. In current terminology, the concept of CAD- CAM restorations involves a most precise digital-assisted production of prosthetic restorations, from its design to the manufacturing phase. The CAD system allows the generation of digital points, surfaces or virtual volumes, on which the practitioner will build the prosthetic restoration. These reconstructions can be replicas of the wax patterns or prosthetic reconstructions generated through CAD software. The CAM system allows the operator (clinician or technician) to manufacture the die or the prosthetic restoration in a conventional or new-generation material. This principle of operation is found in the CEREC system, an innovative technology that involves automatic recognition and extraction of the digital pattern of the future restoration, based on the geometrical model of the part, in order to generate the automated implementation process by coupling CAD to CAM systems. The acronym of the CEREC method derives from CEramic REConstruction. The CEREC system was invented in 1980 by Prof. Werner Mörmann and Dr. Marco Brandestini at the University of Zürich. The authors perfected the system themselves, together with other specialists. Clinical implementation of this new technology was done in 1985 [1, 2]. The newest and most advanced generation of the CEREC system is CEREC 3, which operates in a three-dimensional cartesian coordinate system and has the capabilitiy to perfectly superimpose the virtually-generated image over the real image of the dental arch, obtained through specific methods, from the oral cavity of the patient. This method provides an opportunity to manufacture sustainable, biocompatible, aesthetic, metal-free core restorations, with maximum precision. Restorations, consisting of inlays, onlays and all ceramic crowns, are rapidly manufactured and can be inserted in the oral cavity by adhesive techniques [3-5]. The CEREC system is designed to be used both in the dental office and in the laboratory. The office system is called CEREC 3D, and the laboratory technology to achieve full ceramic restorations is called CEREC InLab [6]. International Journal of Medical Dentistry 189

2 Mariana CONSTANTINIUC, Alina ZAHARIA, Alexandru-Victor BURDE, Daniela POPA, Sorana BACIU PRINCIPLES The computer-aided design and manufacturing systems are based on the principle of operation of several, related, but distinct elements: - a digital impression system which converts the analogous information of the volumes in a numerical data form, exploitable by the computer; - a design system that allows processing of the numerical data, an operation that can range from mere reproduction of dental morphology up to the conception of complex prosthetic elements; - a manufacturing system (milling) that converts the virtual numeric data into analogous objects [3-6]. The CEREC system starts with an optical impression of the preparation and antagonist teeth. The optical impression is captured by an intraoral camera, which transmits the image of the prepared teeth directly into the software of the system. This image is the equivalent of the actual clinical situation, which appears on-screen in a three-dimensional view and offers the possibility to visualize the appearance of the dental preparation, thus eliminating the conventional step of obtaining the impression of the dental arches with classical materials [7]. After teeth preparation and intraoral optical impression, the practitioner will interact with the future restoration exclusively through the computer, that is connected either to the CEREC 3D or inlab system. Depending on the particular operating system, working steps can be conducted with or without the intervention of the laboratory. The system is able to detect the limits of the preparation, but there is also the option to manually trace the limits. Also, the system plans the occlusion using an algorithm based on a biomechanical principle similar to natural dentition eruption [3, 4]. manufacturing the dental restoration, both components acting in parallel (figs. 1 and 2). Fig. 1 - Image acquisition and design component Fig. 2 - Milling system For the manufacturing phase, the milling device is equipped with two special diamond burrs, which have a conical and cylindrical shape (figs. 3 and 4). COMPONENTS OF THE SYSTEM CEREC is a modular system consisting of two units, connected by Hertzian waves: the first is used for image acquisition and the second for Fig. 3 - Diamond burrs contained in the milling unit 190 Volume 4 Issue 3 July / September 2014

3 MANAGEMENT OF PROSTHETIC RESTORATIONS WITH THE CEREC SYSTEM MATERIALS Fig. 4 - Milling process Initially, fine-structured feldspathic ceramics were exclusively used, due to their good mechanical properties, which prevent crack propagation. The feldspathic porcelain is fused with different industrially-manufactured crystals, processed through the CEREC system, and also with a higher biological and mechanical reliability than gold, which has long been the reference material (fig. 7). The cylindrical diamond burr performs, under a continuous jet of water, a speedy and precise modeling (figs. 5 and 6) of the ceramic block. The conical burr allows reproduction of the fine details of occlusal morphology [3, 8]. Fig. 7 - Ceramic blocks Fig. 5 - Milling under continuous water stream At present, besides feldspatic porcelains, there is a wide range of materials available for CAD/ CAM fabrication of dental restorations: zirconium oxide, aluminum, lithium disilicate, synthetic materials, precious and nonprecious alloys. The choice for a certain ceramic material used in CEREC technology is guided by certain requirements that also represent the real advantage of these materials: - properties similar to those of enamel (natural translucency and radio-opacity); - the possibility to individualize the hue of the block and to glaze the restoration; - increased strength, superior or equal to that of the pressed ceramic. WORKING PROCEDURE Fig. 6 - Milling of the ceramic block Using sustainable and biocompatibile materials, in association with a correct dental preparation, along with the use of the CEREC system provides prosthetic restorations with superior durability [9]. The working procedure for the CEREC system includes 3 main stages, which require about 45 minutes. The first stage consists in the preparation of the tooth surfaces, followed by the optical impression of the dental preparation and antagonist teeth (figs. 8 and 9). Also, at this stage, the final form of the prosthetic restoration is designed. International Journal of Medical Dentistry 191

4 Mariana CONSTANTINIUC, Alina ZAHARIA, Alexandru-Victor BURDE, Daniela POPA, Sorana BACIU Fig Inlay insertion Fig. 8 - Preparation designed for demonstration purposes All these manoeuvres may take place exclusively in the dental office, without the participation of a dental laboratory. In this context, the treatment is performed in a single session, requiring no application of provisional work [12-14]. COMPUTER OPERATION Fig. 9 - Optical impression This essential operation for the realization of prosthetic restoration involves several steps: In the first stage, the occlusal contour of the antagonist teeth is selected by the operator, suppressing all other areas on the outskirts of the strictly concerned area (fig. 12). Accurate marking of the occlusal surface of the antagonist teeth is crucial for the automatic generation of the occlusal surface of the future crown. The second stage involves milling and refinement of the obtained restoration (fig. 10). If the working session is split up into two treatment stages, the duration of the clinical phase is reduced, as the manufacturing stage can be performed in the absence of the patient. In the last stage, adhesive fixation is done by the practitioner [10, 11] (Fig. 11). Fig Marking of the anatagonist tooth occlusal surface Fig Milling of the restoration In the second stage, the program automatically detects, with extreme precision, the preparation limits. The contour of the preparation limit can be manually selected by the practitioner (fig. 13). 192 Volume 4 Issue 3 July / September 2014

5 MANAGEMENT OF PROSTHETIC RESTORATIONS WITH THE CEREC SYSTEM Fig Manual selection of the preparation limits The primary objective of the third stage is selection, from the database, of the most indicated type of restoration, taking into account the specific clinical situation (fig. 14). Fig Prefiguration of the proposed restoration In this stage, the CEREC software displays the dental morphology database, allowing the preview of each morphology kit, in order to facilitate the most suitable choice. Several data banks offer the option of choosing the degree of abrasion of the prosthetic crown, so that to correlate it with the age of the patient. After selection of the most appropriate morphology kit, the program allows positioning and possibly altering of crown height, depending on the adjacent teeth. Step four consists of placing the location of the proximal contact points (fig. 15). The CEREC 3 system automatically adjusts the outline of the restoration, taking into account the guidelines imposed by the operator which, aided by the program, places the contact points in optimum position. Fig Contact point with neighbouring tooth To control the degrees of friction between the contact points, a color scheme is displayed, in which: - red signifies a too tight contact point; - yellow symbolizes the need for a more pronounced grinding of the restoration; - green equals the optimum situation. In the fifth stage, the configuration of the occlusion is automatically done, location of the International Journal of Medical Dentistry 193

6 Mariana CONSTANTINIUC, Alina ZAHARIA, Alexandru-Victor BURDE, Daniela POPA, Sorana BACIU oclussal contacts being selected according to a principle that illustrates the natural evolution of dental arches formation (fig. 16). Imitating the natural phenomenon of the teeth eruption, the system moves and guides the occlusal surface of the crown until a perfect integration with the rest of the arch is attained and the restoration has functional occlusion with the antagonist teeth. Fig Localization of the occlusal contact points In this stage, the selected restoration can be validated as such or the design can be optimized using different tools of the program. After completion of these steps, once a prefiguration of restoration exists, the order can be placed to the mill to manufacture the restoration out of the ceramic block. The milled restoration will have the support rod removed by grinding and will be externally glazed. In the end of the process, restoration will be applied in the oral cavity [3, 15-18]. CONCLUSIONS 1. CEREC system is a major technical acquisition of digital solutions in the field of dentistry, being among the most modern methods of optimization of dental restorations. 2. CEREC 3 system proves numerous advantageous practical applications, such as ease of handling and reliability in the manufacturing process of dental prosthetics, by a precise positioning of the interproximal and occlusal contacts. 3. CEREC system provides standardization of the work stages and reduces by up to 40% the involvement of the human factor in the complex process of making prostethic restorations Acknowledgement: Dr. Alexandru-Victor Burde is a fellow of POSDRU grant no. 159/1.5/S/ grant entitled: Model colaborativ institutional pentru translatarea cercetarii stiintifice biomedicale in practica clinica- TRANS- CENT. References 1. Mormann WH. (2006), The evolution of CEREC system. J Am Dent Assoc.; 137(1): 7S-13S. 2. Davidowitz G, Kotick PG. (2011), The Use of CAD CAM in Dentistry -Review Article. Dent Clin of North Am. Jul;55(3): Cerec Dental CAD/CAM Systems. Available at: www. sirona.com 4. Zandparsa R. (2014), Digital Imaging and Fabrication. Dent Clin North Am. Jan; 58(1): Fasbinder D. (2012), Using digital technology to enhance restorative dentistry. Compend Contin Educ Dent.; 33(9): Allen K.L, Schenkel A. B, Estefan D. (2004), An over view of the CEREC 3D CAD/CAM system. Gene Dent. May-Jun; 52(3): Quaas S, Rudolph H, Luthardt R.G. (2007), Direct mechanical data acquisition of dental impressions for the manufacturing of CAD/CAM restorations. J Dent. Dec; 35(12): Arnetzl G, Pongratz D. (2005), Milling precision and fitting accuracy of Cerec Scan milled restorations. Int J Comput Dent. Oct; 8(4): Conrad HJ, Seong WJ, Pesun IJ. (2007), Current ceramic materials and systems with clinical recommendations: A systematic review. J Prosth Dent; 98(5): Baldissara P, Llukacej A, Ciocca L, Valandro FL, Scotti R. (2010), Translucency of zirconia copings made with different CAD/CAM systems. J Prosthet Dent. Jul; 104(1): Rekow ED, Silva NR, Coelho PG, et al. (2011), Performance of dental ceramics: challenges for improvements. J Dent Res.; 90(8): Wittneben JG, Wright RF, Weber HP, et al. (2009), A systematic review of the clinical performance of CAD/ CAM single-tooth restorations. Int J Prosthodont.; 22(5): Martin N, Jedynakiewicz NM. (1999), Clinical performance of Cerec ceramic inlays: a systematic review. Jan; 15(1): Schaefer O, Decker M, Wittstock F, Kuepper H, Guentsch A. (2014), Impact of digital impression techniques on the adaption of ceramic partial crowns in vitro. J Dent. Jun; 42(6): Willer J, Rossbach A, Weber HP. (1998), Computer assisted milling of dental restorations using a new CAD/ CAM data acquisition system. J Prosthet Dent. Sep; 80(3): Volume 4 Issue 3 July / September 2014

7 MANAGEMENT OF PROSTHETIC RESTORATIONS WITH THE CEREC SYSTEM 16. Beuer F. (2008), Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Braz Dent J.; 204(9): Trifkovic B, Budak I, Todorovic A, Vukelic D, Lazic V, Puskar T. (2014), Comparative analysis on measuring performances of dental intraoral and extraoral optical 3D digitization systems. Measurement. Jan; 47: Guess PC, Schultheis S, Bonfante EA, Coelho PG, Ferencz JL, Silva NR. (2011), All-Ceramic System: Laboratory and Clinical Performance. Dent Clin North Am. Apr; 55(2): D.J. Fasbinder. (2006), Clinical performance of chairside CAD/CAM restorations. J Am Dent Assoc. Sep; 137 Suppl: 22S-31S. International Journal of Medical Dentistry 195