Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2018-03-23, 14:18:55 | version 1.38.0
lab tribuneDental Tribune Middle East & Africa Edition | March-April 2015 3C < Page 2C Microcracks are prevented by reducing the grinding work to a minimum. Figs 9a and b: The unsintered structure is carefully ground and smoothed. Figs 10a and b: Brush infiltration before sintering: The colouring liquid is applied in the cervical areas. Fig.8: The milled crowns before they were trimmed from the zirconium oxide disc Fig.7: Same digital data set: preparation for the fabrication of the zirconium oxide crowns (Zenostar Zr Translucent) with CAD/CAM equipment Figs 11a and b: Brush infiltration: The colouring liquid is applied on the cusp tips and in the fissures. Fig. 12: The occlusal surfaces are pol- ished before the stains are applied. Figs 13 and 14: The stains were applied and sprayed with another coating of glaze. wax-up was created (Figs 1 and 2). In this type of situation we prefer to use the manual wax- up technique, because we have found this method to be faster. Alternatively, the restorations could have been virtually de- signed. Irrespective of the meth- od used, a lasting result can only be achieved if the technician has an in-depth knowledge of the principles of functional occlu- sion. The waxed up crowns were transformed into long-term tem- poraries with CAD/CAM equip- ment. First, the physical mod- els and wax-ups were digitally scanned (Zenotec D500, Wie- land Dental) and the STL file was imported into a correspond- ing design software (Dental DesignerTM, 3Shape) (Fig. 3). Then, all the parameters were suitably adjusted and the con- struction data was transferred to the milling machine (Zenotec select, Wieland Dental), where the restoration was cut from a PMMA-based disc (Telio CAD for Zenotec) (Figs 4 and 5). The milled crowns were re-worked only minimally and then placed on the model. In order to impart the PMMA restorations with a natural-looking appearance, their surface texture was fin- ished in such a way that a natu- ral play of light was achieved. The crowns were subsequently polished with a special polishing medium and goat’s hair brushes (Fig.6a). Next, the clinician re- moved the chairside provisional restorations and cemented the long-term temporaries with a suitable luting composite (Tel- io® CS Link) (Fig. 6b). Fabrication of the permanent restorations Three months later, it was time to focus on the permanent res- torations. In an effort to keep the treatment with monolithic restorations as straightforward as possible, the existing data set, which had been validated by means of the longterm tempo- raries, was used (Fig.7). We se- lected the translucent zirconium oxide Zenostar Zr Translucent for the restorations. This mate- rial comes in disc form and in six different shades. We decided to use the ”sun” variant, which would give the restorations a warm, reddish foundation. Vari- ous possibilities of finishing the restoration were available af- ter the milling process (Zeno- tec select) (Fig. 8). In this case, the unsintered structures were characterized with the colour infiltration method. Finishing: brush infiltration In the brush technique, the milled structures (crowns) are infiltrated with a colouring liq- uid (Zenostar Color Zr, Wieland Dental). In this process, the res- torations acquire a lifelike ap- pearance, showing a tooth-like progression of shade, already before the sintering procedure. All the A-D shades can be re- produced with these colouring solutions. Five additional char- acterization stains are avail- able. In the case at hand, the bar joints were removed from the milled crowns 26, 25 and 35 by grinding, and the surfaces were smoothed (Figs 9a and b). Sub- sequently, the colouring liquid was selectively brushed on the cusp tips, around the margins and in deep fissures (Figs 10a to 11b). The charm of this colourless liq- uid lies in the fact that it can be made visible. For this purpose a drop of colour concentrate (Zenostar VisualiZr, Wieland Dental) is added to the solution. As a result, the individual liq- uids can be easily distinguished from each other when they are brushed on the restoration. The colouring material is composed of organic pigments which fire without leaving any significant residue. Next, the restorations were sintered at 1450°C (Ze- notec Fire P1, Wieland Dental). After the sintering process, the crowns appeared lifelike and showed a warm and natural glow due to the reddish zirco- nium oxide used. Only a few mi- nor adjustments had to be made on the basis of the inspection on the model. As a result, this ap- proach not only ensures savings in terms of time and money, but it also heightens quality assur- ance. Fig. 15: The zirconium oxide crown on tooth 25 immediately after it was placed. Tooth 26 was provisionally restored with a PMMA crown. Fig. 16: A suitable alternative to a veneered crown and a cast crown – the full-contour zirconium oxide crown on tooth 35. It smoothly blends into the surrounding dentition. At this stage – before the stain- ing materials were applied – the zirconium oxide crowns were polished and the surfaces were smoothed (Fig. 12). This effec- tively counteracted the common concern of abrasion. Before the crowns were fired, a glaze (Zenostar Magic Glaze, Wieland Dental) was sprayed on their surfaces in order to estab- lish an even base for the appli- cation of the staining materials. Stains in paste form (Zenostar Art Module Pastes, Wieland Dental) were used to character- ize the restorations. The pastes had to be mixed to a soft, smooth consistency before they could be applied. The cervical and incisal areas of the restorations were individualized with the stains (Fig. 13). A film of glaze was sprayed on the restorations (Fig. 14) before they were fired. The combination of the stains and the lightly fluorescent spray glaze produced a three-dimen- sional effect. After the final firing, the crowns did not appear any different from layered restorations. On the contrary, they looked very lifelike and showed a natural internal play of colour. In the next step, the occlusal contacts were checked in the articula- tor and the proximal contacts on the model. Then the crowns were sent to the dental practice for placement. Seating of the restorations Teeth 25, 35 and 26 were suit- ably prepared for the permanent restorations. Unfortunately, the attempt to save tooth 26 failed. The buccal crown wall fractured when the long-term temporary was removed. Right from the beginning, we were aware of the fact that the remaining part of this tooth might not be strong enough to withstand the treat- ment. At this stage, therefore, it became quite clear that the tooth could not be preserved. Conse- quently, the long-term tempo- raries were re-seated and a new treatment plan was presented to the patient for tooth 26 on the basis of a detailed analysis. A few weeks later, the permanent all- ceramic crowns were cemented (SpeedCEM®) on tooth 25 and tooth 35. The plan was to replace tooth 26 with an implant-sup- ported restoration at a later date. Conclusion The monolithic zirconium oxide crowns on tooth 25 and tooth 35 were indiscernible from the oth- er teeth (Figs 15 and 16). The pa- tient reported that she was able to chew comfortably and natu- rally. The CAD/CAM fabrication protocol allowed the crowns to be cost-effectively produced. The translucent material (Ze- nostar Zr Translucent) that was used in this case showed a high level of light transmission. Therefore, it offered the ideal basis for reproducing the optical properties of the natural teeth. The described approach will help to satisfy the rising number of cost-conscious and estheti- cally discerning patients, since it offers an attractive alternative to individually layered ceramic crowns and cast crowns made of precious or non-precious metal. Dieter Knappe, CDT Knappe Zahntechnik GmbH Weinstrasse 14 67889 Schweigen-Rechtenbach Germany dieter.knappe@orange.fr Contact Information