Efficient production of a zirconia overdenture

Every patient is unique. Patients’ 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 the teeth are missing. Fortunately, adequate dental materials and techniques are available for a patient-centred, 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 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 masticatory forces. As technical complications are easier to address than biological complications, the overdenture should not be unbreakable; instead, the replacement of single units should be easily manageable.

Fig. 1: Sintered bar milled from KATANA Zirconia HTML PLUS.

Fig. 3: Finished crowns with individual, age-appropriate shade effects on the sintered bar

Two-part denture design

The solution was a two-part design consisting of a milled bar with a gingival area and tooth abutments (Fig. 1) and of single crowns. The material of choice for the bar was KATANA Zirconia HTML PLUS (Kuraray Noritake Dental), which has a uniform flexural strength of 1,150 MPa throughout the disc, and the single crowns were milled from KATANA Zirconia YML, which offers natural translucency and strength gradation. Whereas 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 (Kuraray Noritake Dental). Customisation of the anterior crowns (Fig. 2) was performed with the internal stains Cervical 1, Grayish Blue, Dark Grey and A+. The finishing layer on the incisors was created using LT0 materials mainly, as well as some CCV-3 on the cervical area 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, Fig. 3). After checking of the fit of the crowns, the gingival areas of the bar were individualised 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 (Figs. 6 & 7).Owing to an excellent fit on the implants (Fig. 8), it was possible to fix the overdenture with the screws immediately, to close the access holes with composite and then to discharge the patient (Fig. 9).

Fig. 4: Bar with individualised gingival areas. Fig. 5: Placement of the central incisor crowns on the bar. Fig. 6: Occlusal screw access hole in the nished overdenture. Fig. 7: Overdenture ready for try-in. Fig. 8: Intra-oral try-in of the aesthetic overdenture. Fig. 9: Final situation.

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 prostheses 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.