Efficient production of a zirconia overdenture

Case by CDT Mathias Berger, France

Every patient is unique. Their specific backgrounds, functional needs and aesthetic demands need to be respected in any prosthodontic treatment plan. However, the importance of an individual treatment approach increases with the number of teeth to be replaced: After all, the impact of the restorations on facial aesthetics and on the patient’s quality of life is never greater than when all teeth are missing. Fortunately, adequate dental materials and techniques are available for a patient-centered, individual approach, no matter what challenges need to be overcome.

A patient with bruxism

In the present case, an elderly male patient with bruxism was in need of a new maxillary denture. Since the placement of five implants in the maxilla, he had no proprioception in this jaw. This lack of sensation had an impact on the overdenture to be produced: material and design needed to be carefully selected in a way that it would withstand uncontrolled chewing forces. As technical complications are easier to repair than biological complications, the overdenture should not be unbreakable – instead, the replacement of single units should be easily manageable.

Two-part denture design

The solution was a two-part design with a milled bar consisting of the gum area and tooth abutments (fig. 1) combined with single crowns. The material of choice for the bar was KATANA™ Zirconia HTML Plus (Kuraray Noritake Dental Inc.) with a uniform flexural strength of 1,150 MPa throughout the disc, while the single crowns were milled from KATANA™ Zirconia YML that offers natural translucency and strength gradation. While a monolithic design was selected for the posterior crowns, the six crowns for the anterior region received a micro-cutback for aesthetic micro-layering with CERABIEN™ ZR Porcelain. The shade scheme for individualization of the anterior crowns is shown in fig. 2. In a nutshell, customization was performed with the Internal Stains Cervical 1, Grayish Blue, Dark Grey and A+. The finishing layer on the incisors was created mainly using LT0 materials with some CCV-3 on the cervical and LT Natural on the mesial and distal lobes. On the canines, LT1 was used instead of LT0. The posterior crowns were merely finished with liquid ceramics (CERABIEN™ ZR FC Paste Stain, Kuraray Noritake Dental Inc.).

Fig. 1. Sintered bar milled from KATANA™ Zirconia HTML Plus.

Fig. 2. Chroma map for micro-layering in the anterior region.

Fig. 3 shows the finished single crowns with their individual, age-appropriate shade effects on the sintered bar. After checking the fit of the crowns, the gum areas of the bar were individualized using CERABIEN™ ZR Tissue Porcelain (fig. 4). Subsequently, the crowns were luted to the zirconia abutments (fig. 5), leaving screw access holes in aesthetically uncritical positions (fig. 6). The final overdenture ready for try-in is shown in fig. 7. Due to an excellent fit on the implants (fig. 8), it was possible to immediately fix the overdenture with the screws, close the access holes with composite and discharge the patient. The final appearance is shown in fig. 9.

Fig. 3. Finished crowns on the sintered bar.

Fig. 4. Bar with individualized gum areas.

Fig. 5. Placement of the central incisor crowns on the bar.

Fig. 6. Occlusal screw access hole in the finished overdenture.

Fig. 7. Overdenture ready for try-in.

Fig. 8. Intraoral try-in of the aesthetic overdenture.

FINAL SITUATION

Fig. 9. Treatment outcome.

CONCLUSION

This patient case is a good example of how important it is to respect the patient’s background, age and specific demands when producing dental restorations. Thanks to the great variety of restorative materials with different mechanical and optical properties available, it is possible to create suitable prosthetics for virtually every patient. However, for this purpose, it is important to stay up to date regarding new products launched and techniques developed. This way, it is often even possible to create beautiful and durable solutions in a simplified and efficient procedure such as micro-layering on innovative zirconia with a high aesthetic potential.

Dentist: