A clinical case report by Johannes Beiter, Germany which sees amalgam fillings being replaced with glass-ceramic restorations.
Workflows and procedures in practice are changing as a result of the increasing establishment of computer-assisted dentistry in prosthetic therapy and the growing diversity of materials. The possibility of chairside fabrication is improving both patient comfort and productivity. A new interesting material for single-tooth restorations is the Straumann® n!ce® glass-ceramic. The material is presented by the author based on a patient case.
The patient wished to have the large-surface amalgam fillings in the upper and lower jaw removed (Fig. 2-3). He wished to have fully ceramic restorations that can be created with the smallest possible effort. These are single-tooth restorations (partial crowns). In the upper posterior region a bridge restoration was indicated, which was implemented with lithium disilicate ceramic. All other indirect single-tooth restorations had to be performed with Straumann n!ce. The material is biocompatible,
and relatively strong without additional crystallization firing, while featuring natural photo-optical properties.
The aim was new minimally invasive treatment within the dental workflow. No functional disorders were present. No periodontal abnormalities were identified either. A vitality test was performed on all teeth with a positive result, up to tooth 46. This tooth underwent root canal treatment.
After the anesthesia and fitting of the rubber dam, the amalgam fillings were removed and the teeth were prepared in a minimally invasive way for full ceramic restorations (Fig. 4-6). The precondition: Rounded design, no corners or sharp edges, shoulder preparation with rounded edges and/or hollow groove. The manufacturer specifies 1 mm as the minimum layer thickness for crowns and partial crowns, which was complied with in the preparation.
Construction and grinding
The situation was “molded” or scanned respectively with the intraoral camera. To prevent mirror images or undesired reflections, the teeth first had to be dried to the maximum extent. This was followed by buccal bite registration (scan) and importation of the data into the CAD software.
The scans were checked and artifacts were removed. After the virtual model calculation and assignment of the jaws with the bite register, the preparation boundary could be easily marked and the insertion axis defined with a few clicks. The automated, biogeneric initial suggestion of the software was a valuable aid in constructing the restorations. Only minor changes were made to the initial suggestion. The restorations were constructed within a short time (Fig. 7-8) and the data were transferred to the CAM machine. In the milling preview, the design was finally checked, e.g. for values below the minimum wall thickness. The precrystallized n!ce was now fixed and the restorations were ground (Fig. 9). Milling was performed in the fine mode and lasted about 25 minutes.
After removing the ground restorations from the machine, the grinding pins of the blank were removed with a fine grain diamond. The restorations ground from n!ce showed finely tapered margins and a 1:1 reproduction of the construction. On trial placement in the mouth, the fit was judged as very good. At some sites the approximal contact points were adjusted as required. Final polishing of the restoration outside the mouth produced a high gloss finish. For a natural appearance, the n!ce restorations can be polished with a standard polishing set for lithium disilicate glass-ceramic. A classical polishing protocol was used in this case – coarse burs, ceramic polisher, zirconium oxide polishing paste and brushes (Fig. 10) – and the restorations were then cleaned in an ultrasonic bath. The crowns and partial crowns were ready to be fitted. An additional crystallization firing as for comparable materials is not necessary for n!ce.
The insertion of restorations in the mouth was performed with adhesive attachment under rubber dam. The same adhesive securing cements can be used for n!ce as for lithium disilicate. Before insertion, the ceramic restorations were cleaned with phosphoric acid (30 seconds). Conditioning of the adhesive surface was performed per protocol with 20-second etch bonding (5% hydrofluoric acid gel). After cleaning and conditioning the teeth, final insertion of the restorations was performed (Fig. 11-12) and the functional criteria underwent a final check. The two small amalgam fillings in teeth 34 and 35 were exchanged for direct composite fillings.
In combination with the intraoral scanner and the chairside CAM machine, Straumann n!ce glass-ceramic offers the possibility of fabricating indirect single-tooth restorations easily, safely and comfortably within the dental workflow. The lithium alumosilicate ceramic is supplied in the fully crystallized state. No crystallization firing is necessary. Grind, polish, done – the procedure described offers high comfort for the patient and
high productivity in everyday practice.
Dr. Johannes Beiter specializes in the fields of periodontology and implantology. Since 2012 he has been a dentist specializing in oral surgery, holding a Master of Science degree in periodontology and implant therapy.
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