Same-day dentistry: Replacement of two PFM crowns with zirconia restorations

Clinical case by Dr. Frank Heldenbergh

The advancements in zirconia in contemporary dentistry nowadays allow for a wider range of applications, including in the anterior sector, and for chairside production using dedicated CAD/CAM systems. Even without a cutback, KATANA™ Zirconia Block (STML), combined with CERABIEN™ ZR FC Paste Stain (both Kuraray Noritake Dental Inc.), offer an extremely satisfactory aesthetic solution.

In the present patient case, the materials were chosen to replace old PFM crowns on the maxillary central incisors. The planned treatment was in accordance with the patient's wishes, and carried out in a single appointment.

CASE DESCRIPTION

The patient asked for a replacement of the existing crowns on the two maxillary central incisors (teeth 11 and 21, FDI notation). The porcelain-fused-to-metal (PFM) restorations had been in place for about thirty years (Figure 1). She desired aesthetic improvements and slight repositioning of these two teeth.

TREATMENT PLAN

In agreement with the patient, it was decided to perform the entire procedure in one appointment: removal of the existing crowns, digital impressions, production, and bonding of new restorations. The periodontium was healthy with no bleeding. The only uncertainty was whether the existing crowns were cemented onto inlay-cores or if they were Richmond crowns. A preliminary silicone impression was taken as a precautious measure: in case something unexpected prevented the new crowns from being bonded during the session, it would be easily possible to produce temporary crowns.

Fig. 1. Initial clinical situation.

TREATMENT

Using a diamond bur followed by a tungsten carbide bur, the existing crowns were removed, revealing that they indeed were Richmond crowns. Because the anatomy of the intra-radicular posts clearly contraindicates an attempt to remove these posts, it was decided to trim the crowns to transform them into inlay cores rather than risk further damage. The corono-peripheral preparations were reworked at the same time. One of the major challenges was related to the necessity of masking the metal of the transformed coronal-radicular reconstructions. Luckily, the space available was sufficient for the production of full zirconia crowns with a significant thickness (Figure 2). The target shade of the crowns was chosen in consultation with the patient (Figure 3).

Fig. 2. Situation after removal of the existing restorations.

Fig. 3. Shade determination using a shade tab: A2 was the appropriate shade.

Subsequently, impressions were taken using and intraoral scanner, the virtual models were checked and the crowns designed, considering the patient's request to have her two incisors slightly retracted (Figures 4 and 5).

Fig. 4. Virtual models of the patient’s teeth with the newly designed crowns, revealing the space available for a slight retraction.

Fig. 5. Designing of the two crowns.

The two crowns were milled from KATANA™ Zirconia Block 14Z A2 (Figure 6). A quick reminder: unlike lithium disilicate, zirconia prosthetic parts cannot be tried in immediately after milling, as they are around 20 percent larger than their final size after sintering. Final sintering was performed within about 18 minutes using the furnace SINTRA CS (ShenPaz Dental Ltd). After this process, the crowns may be tried on to check their fit, shape, shade and optical integration.

Fig. 6. Milled crowns in the CAD/CAM blocks.

For finishing of the restorations, different options are available. In this case, we decided not to limit ourselves to mechanical polishing of the prosthetic parts, as zirconia does not fluoresce like natural teeth. To add fluorescence as an optical feature, the surface was lightly stained and glazed with CERABIEN™ ZR FC Paste Stain (Figure 7).

Fig. 7. Crowns in the furnace after staining and glazing with liquid ceramics.

After firing, the two incisor crowns were tried in again using a try-in paste corresponding to the chosen resin cement system (PANAVIA™ V5, Kuraray Noritake Dental). In this way, the final appearance was simulated to validate the shade of the cement. The intaglio surfaces of the crowns were then sandblasted before applying CLEARFIL™ CERAMIC PRIMER PLUS as the restoration primer. The prepared teeth were treated with KATANA™ Cleaner (Kuraray Noritake Dental Inc.) to decontaminate the surface from proteins in saliva and possibly blood. Those clean surfaces are ideal for bonding. After thorough rinsing and drying, PANAVIA™ V5 Tooth Primer (containing MDP monomer for bonding with the hydroxyapatite and metal of the preparation) was applied according to the manufacturer’s instructions (Figure 8).

Fig. 8. Selected cementation system and try-in.

Subsequently, PANAVIA™ V5 Paste was applied into the first crown, which was then seated, followed by tack curing (brief photopolymerization for three to five seconds), excess removal and final light curing from all sides.

The procedure was then repeated for the second maxillary central incisor. The result instantly satisfied the patient, both in terms of aesthetics (adaptation, position of the new crowns, mimicry) and the comfort provided (Figures 9 and 10).

Fig. 9. Crowns immediately after placement.

Fig. 10. Aesthetically pleasing and comfortable result.

At a recall after four months, soft tissue conditions were ideal and the patient was happy with the outcome (Figures 11 to 13). The selected zirconia had nice optical properties, masking of the metal posts was successful and the natural surface texture contributed its share to a nice overall picture. The retracted position of the teeth was also perceived positively by the patient, while comfort and function were excellent.

DISCUSSION

Although lithium disilicate has so far been considered the material of choice for prosthetic work in the anterior region, zirconia is nowadays proving to be an extremely satisfactory alternative from every point of view: milling, strength, aesthetics, assembly (among other things, no hydrofluoric acid is required for bonding). KATANA™ Zirconia Blocks (STML) with a multi-layered colour structure in a single 4Y-TZP zirconia block, combined with CERABIEN™ ZR FC Paste Stain, offer a remarkable solution. This applies to treatments around the replacement of existing crowns as well as first-line treatments with less invasive preparations (verti-prep) than those required by other types of ceramics.

Fig. 11. The patient’s smile at a recall after four months.

Fig. 12. Great optical integration.

Fig. 13. Natural surface texture contributing to success Control pictures after four months taken by Emmanuel Charleux.

Dentist:

FRANK HELDENBERGH

Dr. Frank Heldenbergh graduated with a Doctor of Dental Surgery degree from the University of Reims in 1988.Driven by a passion for prosthetics, he pursued further specialization as a Prosthetic Resident at the UFR Odontology of Reims from 1990 to 1992. Dr. Heldenbergh’s dedication to advancing dental practices led him to join the Board of the Academy of Adhesive Dentistry in 1999. His commitment to this field has been unwavering, and he currently serves as the Vice President of A.D.D.A.-R.C.A.

Recognized for his expertise in ceramic veneers, inlays and onlays, Dr. Heldenbergh supervised practical work for the Paris Odontological Society from 2000 to 2018, shaping the skills of many aspiring dentists. His influence extended to the A.D.F. Congress, where he supervised practical work on ceramic veneers from 2000 to 2016. In 2017, he was the Head of Practical Work at A.D.F., a role that allowed him to further contribute to the advancement of dental education and practices. In 2018, he was the Head of Practical Work for ceramic veneers at the Paris Odontological Society.

Recognizing the importance of technology in modern dentistry, Dr. Heldenbergh pursued a University Degree in CAD/CAM from Toulouse in 2022. This addition to his qualifications highlights his dedication to staying at the forefront of dental innovation.