IPS Empress CAD and IPS e.max CAD LT offer aesthetics and strength

The chairside method offers many advantages. For example, it produces fast and precise results, allowing all-ceramic restorations to be fabricated and seated in only one appointment. The patient in the following case requested this type of treatment for an all-ceramic solution to replace his more than thirty-year old restorations. In the dental examination, the onlay was shown to have suffered some damage because of heavy occlusal contacts (Fig. 1).

Case report

Incipient dentin caries was visible on the mesial aspect. Therefore, the contact point was integrated into the partial crown preparation. Sharp-edged transitions, cusp coverage, and bevels were avoided. The preparation margins in visible areas did not cause any aesthetic problems, since tooth-coloured materials were used in this case. Adequate space was provided, to place the ceramic with the adhesive cementation technique. The preparation border of crown #36 was located at the level of the bifurcation. A pronounced circular chamfer was prepared here, and the inner edges were rounded, as sharp edges can cause the formation of stress peaks and fractures. The thickness of the material corresponded to the minimum requirements for ceramics, and adequate space was available (Fig. 2).

Fig. 2: Checking of the available space from the vestibular aspect.

In the chairside technique, a scan of the tooth surface with an intra-oral camera replaces the conventional impression-taking step. The scanned-in data is then digitalised for the CAD/CAM procedure. For the scanning process, the teeth are coated with the matt, white-opaque IPS Contrast Spray Chairside (Fig. 3).

Similarly, the static occlusion is recorded intra-orally with a check-bite using silicone (Fig. 4). From this data, the CEREC software generates a virtual model upon which the restoration is fabricated.

Mad about blue

Premolars with glass-ceramic restorations placed with the adhesive technique have produced excellent long-term results. Hence, we decided to use the IPS Empress CAD Multi Block to fabricate the restoration. This polychrome ingot demonstrates a steadily increasing translucency from the cervical to the incisal region. As a result, its appearance closely resembles that of natural teeth; therefore, restorations made with this ingot do not have any visible transitions.

Crown #36, however, had to be bonded on dentin using the adhesive technique. Consequently, the high bonding values achieved in enamel could not be produced. Furthermore, the crown was located at the chewing centre. Thus, IPS e.max CAD LT, which offers adequate stability, was chosen for the chairside treatment. The low translucency version is suitable for posterior teeth and adhesive cementation procedures. In addition, its hardness value of 360 MPa is three times higher than that of feldspathic ceramics.

First, we constructed the full crown, as this took longer than the partial crown. Figure 5 shows the restoration in its ‘blue’ lithium metasilicate state after it has been milled. The marginal seal at try-in was impeccable (Fig. 6). The occlusion was carefully checked and adjusted. This could also have been done at the end state, but polishing would have been required.

Figs. 3–6: Matt preparation surface( Fig. 3). Matt surface of the check-bite, which records the static occlusion (Fig. 4). Milling results of the ‘blue crown’ (Fig. 5). Try-in of the crown in the lithium metasilicate state (Fig. 6).

In most cases, a crown can be completed in only one firing cycle. When the crown is crystallised at 850°C in a vacuum furnace, such as the Programat CS, it should be supported by IPS Object Fix firing paste, which ensures the even distribution of temperature (Fig. 7). In this partially crystallised blue state, the crown can already be characterised with IPS e.max CAD stains (Fig. 8). In the half-hour procedure, the ceramic obtains the selected tooth-colour and final hardness. This method saves a considerable amount of time in single-appointment treatment. Following the combined stains and glaze firing, the crown is ready for placement (Fig.9).

Figs. 7 & 8: Careful removal of excess (Fig. 7). Partially crystallised crown with glaze (Fig. 8).

Efficient, aesthetic & precise

Subsequently, the partial crown was constructed and polished. The try-in of the machined CEREC restoration showed the precision of the work (Fig. 10). The partial crown was polished to a high gloss with OptraFine silicone polishers. Glazing and characterisation would have been possible at this point. However, in most cases the polychrome IPS Empress CAD Multi Block achieves outstanding results in the posterior region without further work. The full crown could also have been conventionally cemented.

Nevertheless, we decided to use the adhesive bonding technique in this case, as we have found that this method produces the best long-term results with ceramics. The strong bond optimally supports the material, while creating a lasting seal against bacteria. Adhesive cementation with the Syntac system and a flowable light-curing composite is an established routine in our practice. We use this technique whenever it is possible.

Figs. 9–11: Final result prior to placement (Fig. 9). Side view at try-in (Fig. 10). Seated IPS Empress CAD Multi restoration (Fig. 11).

Figure 11 shows the clinical result after the removal of excess. The follow-up examination after one month revealed impeccable clinical conditions, without any gingival irritation or premature contacts. The patient was very satisfied with the result, particularly because treatment could be completed in one appointment, owing to a high-strength ceramic.

Editorial note: This article was originally published in Cosmetic Dentistry Vol. 2, Issue 4, 2008 and is published here with the kind permission of Ivoclar Vivadent.

Author info

Dirk Ostermann has been using CEREC since 1998. He is a national and international speaker for CEREC. Dr Ostermann is in private practice in Hanover, Germany, emphasising on ceramic restorations as well as endodontics and implantology.