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Dental Tribune Middle East & Africa Edition No. 5, 2015

Dental Tribune Middle East & Africa Edition | September-October 2015 21CAD/CAM < Page 20 Carlo Monaco, DDS, MSc, PhD Researcher, Assistant Professor University of Bologna Via S. Vitale 59 40125 Bologna, Italy carlo.monaco2@unibo.it Prof. Dr Giovanni Zucchelli, DDS, PhD Associate Professor Department of Oral Sciences University of Bologna Via S. Vitale 59 40125 Bologna, Italy giovanni.zucchelli@unibo.it Luigi De Stefano, DT Via Martiri D’Ungheria 132 84018 Scafati (SA) Italy info@luigidestefano.com Contact Information the canines were found to be too long in relation to the new ap- pearance of the central and lat- eral incisors (Fig. 2). To redress this situation, the patient was given the option to have her ca- nines reduced by approx. 1 mm following the insertion of the temporary restoration. Further- more, the patient was informed of the need for surgical inter- vention to adapt the course of her gum line. Treatments neces- sitating a reduction of healthy tooth structure and/or a change of the gingival profile require the use of visualization software, such as the Digital Smile Design program, because such changes cannot be made visible with models or mock-ups. After the existing restorations were removed with a tungsten carbide bur (Fig. 3), the resulting abutments were in a suboptimal condition and tooth 22 was dam- aged by a carious lesion. It was therefore necessary to build up the abutments using composite material and an adhesive before the temporary PMMA restora- tions (polymethyl methacrylate) could be placed. The primary objective was to avoid a further reduction of tooth structure. Af- ter completion of the conserva- tive treatment, the built-up teeth were again slightly reduced to create space in the interproxi- mal area with the aim to encour- age the papillae to grow into the interdental spaces between the temporary restorations (Fig. 4). Surgical intervention Surgical crown lengthening was performed to attain a harmoni- ous gum line. After the peri- odontal surgical soft tissue pro- cedure, the bucco-lingual bone was reduced using a diamond- coated drill and hand chisel with the aim to expose 5 mm of tooth structure above the alveo- lar bone crest. After the surgical intervention, the exposed root surfaces were smoothed up to the bone crest with the help of curettes, followed by the prepa- ration of the abutment teeth. Here, the aim was to modify the natural emergence profile of the teeth as they emerge from the alveolar ridge and, as a result, to limit the coronal growth of the soft tissue portions in the buc- cal and palatal areas. Finally, the soft tissue flaps were secured over the buccal and palatal sides of the alveolar bone using sim- ple vertical mattress sutures (PGA 6/0) and anchored to the periosteum on the buccal side. After the surgery, the temporary restorations were inserted us- ing calcium hydroxide cement. This intervention meant that the patient was not able to clean her teeth in the areas affected. Instead, she was instructed to rinse with 0.12% chlorhexidine solution for one minute three times a day. Temporization At the following appointment, the sutures were removed and a precision impression - with- out placing a retraction cord - was taken. This impression was used to create a second “se- ries” of temporary restorations amenable to relining. Three weeks after the surgery, the final preparation of the abut- ments was performed. The gum line was used as a reference to provide orientation in the cervi- cal region. Early temporization was advantageous to soft-tissue conditioning. With this measure, a potential soft-tissue rebound was easier to monitor and the desired esthetic outcome could be achieved in a targeted fash- ion. Over the following five to six months, the temporaries were additionally modified to allow the interdental papillae to grow into an appropriate shape. Intraoral data capturing Six months after the surgery, the soft tissue had developed into an ideal shape (Fig. 5). Time had now come to begin with the fi- nal prosthetic stage. Only one appointment was planned for this stage. As the patient was satisfied with the morphologi- cal shape and function of the temporary restorations, the PMMA restorations were uti- lized as prototypes for the final crowns. Two digital impressions were required. At the first step, a digital record of the temporary restoration was created and sub- sequently used as a “biogeneric” model. At the second step, the abutment teeth were digitally recorded after a retraction cord had been placed. Both the tem- porary restorations and abut- ment teeth were coated with a dusting of scanning powder to facilitate optical data capturing (Figs 6 to 8). After intraoral scan- ning (CEREC® Bluecam, Sirona Dental Systems GmbH, Germa- ny), the data were imported into the CAD software (CEREC Soft- ware V. 4.2) and integrated into the design of the restorations. The parameters concerning the space for the luting composite and adhesive were set to 30 and 20 μm respectively and the mini- mum incisal ceramic was set to 1,5 mm. Additionally, digital re- cords of the opposing jaw and bite registration were also taken. Material All-ceramic restorations should demonstrate natural optical properties and offer a lifelike surface texture. Simultaneously with the ad- vancement of CAD/CAM tech- nology, the manufacture of CAD/CAM blanks has been con- sistently improved. Esthetic re- sults that look intriguingly simi- lar to the natural dentition can now be easily achieved due to the combination of the “enamel- like” optical properties of the IPS e.max® CAD HT blocks (high translucency) and the staining technique - no individual lay- ering is required. Lithium dis- ilicate glass-ceramic blocks (IPS e.max CAD HT C14/A2) were the chosen material for the case described here. The blanks were processed in the CEREC milling unit (Sirona) using a Step Bur 12 and a Cylinder Pointed Bur 12S (Fig. 9). Crown seating After crystallization firing, the restorations were fitted on the abutment teeth and their accu- racy of fit was evaluated. Minor shape adjustments were per- formed and the occlusal and proximal contacts adjusted (Fig. 10). Finally, customized effects were applied to the crowns us- ing the staining technique (IPS e.max Ceram Shades) (Fig. 11). The dual-curing luting com- posite Variolink® Esthetic DC was selected for placing the crowns. This material is avail- able in several shades to allow an ideal esthetic integration. Water-soluble, glycerine-based try-in pastes provide valuable assistance in selecting the cor- rect colour composite (Fig. 12). With these pastes, the shade ef- fect of the all-ceramic restora- tion can be simulated before it is permanently cemented. The try- in pastes feature the same shade and translucency as the lut- ing composite after it has been cured. The consistency of the try-in paste is similar to that of the luting composite. In the pre- sent case, each time the restora- tion was tried in with one of the coloured try-in pastes, the shade effect was measured using a col- ourmeasurement device (Spec- troShade, MHT). With the five different shades Light+, Light, Neutral, Warm and Warm+, the translucency can be modified in varying degrees of percentage, ranging from brighter/whiter to darker/yellower and the darker shades can be used to change between the levels of opacity and translucency. With a trans- lucency of approx. 10% and a relatively bright shade effect, the “Light” version was selected for the final cementation. The crowns were seated on the same day (Figs. 13 and 14). Conclusion In the case presented here, the combination of CAD/CAM tech- nology, a lithium disilicate glass- ceramic and a colour-balanced luting composite enabled us to use a straightforward and effi- cient method to restore our pa- tient’s smile to its full attractive- ness. Many manufactures have developed materials that can hardly be distinguished from their natural counterpart, i.e. the tooth. Fig. 6: Intraoral digital registration of the tempo- rary restorations Fig. 9: Crowns were designed and then milled from lithium disilicate blocks (IPS e.max CAD HT C14/ A2). Fig. 7: The temporary restoration was used as a ”biogeneric“ model. Fig. 10: Try-in of the milled crowns and adjustment of proximal contacts Fig. 8: Preparing the digital scan of the abutment teeth Fig. 11: Customization using the staining technique Fig. 12: Selecting a suitable shade of the luting composite (Variolink Esthetic DC) using glycerine-based water-solu- ble try-in pastes Fig. 13: Final seating of the individual crowns. Air blocker (Liquid Strip) was applied to prevent the formation of an inhibition layer during lightcuring. Fig. 14: Permanently seated restoration. In only one treatment session, the final prosthetic restoration was completed and seated.

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