Print/Press Workflow With a Novel Silicate Ceramic Material: A Case Report

Jose Maria Ayub, DDS; Telmo Santos, CDT; Mauricio Figueredo, DDS; Julian Conejo, DDS, MSc; and Markus B. Blatz, DMD, PhD

Abstract: Digital technology that utilizes 3D printing has become a viable alternative to the traditional fabrication of wax patterns and definitive restorations for pressable ceramics. Digital workflows afford clinicians fewer variables, improved repeatability, and faster design and fabrication times. The print/press technique for producing zirconia-reinforced lithium-disilicate restorations offers benefits in terms of convenience, precision, and improved mechanical properties. This article describes an efficient workflow for monolithic ceramic restorations using the print/press technique and a novel zirconia-reinforced silicate ceramic.

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Lithium-disilicate ceramic restorations have gained popularity due to their excellent esthetic and mechanical properties.¹ These restorations can be fabricated using either computer-aided design/computer-aided manufacture (CAD/CAM) procedures or lost-wax techniques.² Pressed restorations have been found to have significantly better marginal fit accuracy compared to those milled from lithium-disilicate blocks.^3-5 However, the conventional fabrication of wax patterns for pressed restorations has several drawbacks, including time consumption, technique sensitivity, and potential inaccuracies in the wax pattern, which can affect the final restoration quality.^2,5

The use of digital systems, such as 3D printing, has been developed as an alternative method for the traditional fabrication of wax patterns and definitive restorations. CAD/CAM-generated restorations provide technicians more facilities during the fabrication process, with fewer variables, ensuring greater repeatability and reliability in the restorations. CAD/CAM also minimizes the time required for design and production, making it a more efficient alternative to traditional methods.⁶

The print/press technique involves creating a 3D-printed wax pattern, which is then used to form a mold for pressing ceramic materials. This dual approach combines the accuracy of digital design with the material properties of ceramics. This article describes a workflow for monolithic ceramic restorations using the print/press technique and a novel zirconia-reinforced silicate ceramic.

A 33-year-old female patient presented with severe wear on her maxillary teeth due to bruxism and acid erosion. After clinical and radiographic analysis, ceramic restorations were chosen to close diastemas and restore function and esthetics (Figure 1 through Figure 3).

Intraoral scans were taken and sent to a smile design planning center in Madrid, Spain (DSD Planning Center, digitalsmiledesign.com), where facial parameters were analyzed and a final 3D smile design was created (Figure 4). The virtual design was approved by the practitioner.

A 3D-printed (Form 3+ printer, Formlabs, formlabs.com) model (Model Resin V2, Formlabs) from the digital wax-up made by the planning center was used to create two silicone indexes (Panasil^®, Kettenbach Dental, kettenbach-dental.us), one to serve as a tooth reduction guide and the other for fabrication of provisional restorations. Another 3D-printed model was used to create a silicone index to transfer the digital wax-up into a mockup on the patient (Figure 5).

Because of severe wear of the incisal edges, acid erosion on the palatal surfaces, and the presence of diastemas between the anterior teeth, the maxillary central and lateral incisors and canines were prepared for 360-degree laminate veneers using a conservative full-coverage design. The maxillary premolars and first molars were prepared for facial-occlusal laminate veneers using cutting burs of 0.3-mm depth facially and 1-mm depth occlusally/incisally. This preparation approach facilitated enamel conservation for partial- and full-coverage restorations (Figure 6 to Figure 8).

Subsequently, a digital intraoral final impression was made using a powder-free scanner (TRIOS 3, 3Shape, 3shape.com) and exported to a dental laboratory through the scanner software's specific connection portal where the final restorations were designed with a CAD software (Inlab 19, Dentsply Sirona, dentsplysirona.com) (Figure 9). Specific 3D printing resins with high wax content (Castable Wax 40 Resin, Formlabs) were used for the fabrication of residue-free burnout molds to print the patterns. Once printed, the wax patterns were checked for marginal fit and adaptation into the prepared printed model before investing (Figure 10). This alternative technique may be used when a milling machine is unavailable, although 3D printer parameters and post-cleaning and curing protocols should be followed as indicated by the manufacturer to achieve optimal marginal adaptation.⁷

A zirconia-reinforced lithium-disilicate press ceramic system (Vita Ambria^®, VITA Zahnfabrik, vita-zahnfabrik.com) was selected as the restorative material because of its high flexural strength and its availability in translucent and high translucent levels.^8,9The restorations based on the printed patterns were pressed and finished in preparation for intraoral placement (Figure 11). Once the restorations were received, dry and wet try-ins were conducted under relative isolation to check the marginal fit, preparation adaptation, and shape. Restorations were tried in with a light paste (Variolink^® Esthetic LC Try-in +, Ivoclar, ivoclar.com) for a detailed esthetic and phonetic evaluation.

After the patient's esthetic approval, the restorations were removed and rinsed with air-water, followed by 5% hydrofluoric acid-etching for 20 seconds (Figure 12).⁸ A specific cleaner (Ivoclean^®, Ivoclar) was applied to the intaglio surfaces of the restorations to ensure the surfaces were free of residues (Figure 13). A silane coupling agent (Monobond Plus^®, Ivoclar) was then applied to the intaglio surfaces of the restorations for 60 seconds (Figure 14). Adhesive cementation was performed under absolute isolation (Figure 15). The tooth surfaces were etched with 37% phosphoric acid for 20 seconds and rinsed with air-water. After air-drying the tooth surfaces, a bonding agent was applied (Tetric^® N-Bond Universal, Ivoclar).

The restorations were inserted with a resin cement (Variolink^® Esthetic LC, Ivoclar). The cement was light-cured from the labial and palatal surfaces for 20 seconds. After cementation, a water-soluble gel (Liquid Strip, Ivoclar) was used on the margins of the restorations to eliminate the oxygen-inhibited layer and light-cured for 20 seconds (Figure 16). Centric and eccentric occlusal contacts were verified with articulating paper.

Final intraoral and extraoral images showed the integration of the restorations to the soft tissue with natural morphology and texture while also demonstrating dentofacial harmony (Figure 17 through Figure 21).

The present technique describes a workflow using a new pressable zirconia-reinforced silicate ceramic. The use of CAD/CAM additive systems for fabricating wax patterns has been found to improve the marginal fit of pressed restorations compared to conventional wax pattern fabrication.^2,5 This improvement in marginal fit is crucial for ensuring the longevity and success of the restorations, as a precise fit helps to prevent microleakage and secondary caries.⁶ Additionally, the use of CAD/CAM systems eliminates several limitations of the conventional waxing technique, such as human error and inconsistencies in wax pattern production.^6,10

Furthermore, 3D printing of wax patterns has been demonstrated to be more accurate than conventional hand-formed and milling production of wax patterns in terms of marginal and internal fit.¹¹ This increased accuracy is attributed to the precise control and repeatability of the 3D printing process, resulting in wax patterns that closely match the digital design.¹² The improved fit of the wax patterns translates to better-fitting restorations, reducing the need for adjustments and improving overall clinical outcomes.

In addition to the advancements in wax pattern fabrication, zirconia-reinforced silicate ceramic, such as the one used in this case, offers improved strength and durability for restorations.⁹ The incorporation of zirconia reinforcement enhances the flexural strength of the ceramic, reducing the risk of fracture or chipping.¹³ This increased strength is particularly beneficial for restorations in high-stress areas, such as posterior teeth, where durability is crucial for long-term success.

Moreover, the zirconia-reinforced silicate ceramic exhibits excellent esthetic properties, including natural translucency and color stability.¹⁴ These optical characteristics allow for restorations that closely mimic the appearance of natural teeth, enhancing patient satisfaction and esthetics.

The print/press technique for fabrication of zirconia-reinforced lithium-disilicate dental restorations offers advantages in terms of convenience, precision, and improved mechanical properties. The use of digital systems, including 3D printing, allows for highly accurate fabrication of wax patterns and definitive restorations. Further research and clinical studies are needed to evaluate the long-term success and clinical outcomes of this technique.

Jose Maria Ayub, DDS
Visiting Scholar, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Telmo Santos, CDT
Laboratory Technician, XD Digital Dental Lab, Miami, Florida / Belo Horizonte, Brazil

Mauricio Figueredo, DDS
Private Practice, Montevideo, Uruguay

Julian Conejo, DDS, MSc
Assistant Professor, Clinical Restorative Dentistry, and Director, Chairside CAD/ CAM Dentistry, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Markus B. Blatz, DMD, PhD
Professor of Restorative Dentistry, Chair, Department of Preventive and Restorative Sciences, and Assistant Dean, Digital Innovation and Professional Development, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Figures and Images

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Figure 1

Fig 1. Initial frontal view of the patient smiling, showing diastemas and wear of the maxillary anterior teeth.

Figure 2

Fig 2. Initial intraoral frontal view of the maxilla showing attrition on the incisal edges of the maxillary incisors.

Figure 3

Fig 3. Initial extraoral view showing attrition on the incisal edges of the maxillary incisors.

Figure 4

Fig 4. Facially driven 3D diagnostic wax-up done by the smile design planning center: left, ideal pretreatment (original model untouched); right, ideal post-treatment (original model digitally reduced on subtractive areas).

Figure 5

Fig 5. Printed wax-up model (left) and silicone matrix (right) used to transfer the design to the patient.

Figure 6

Fig 6. Lateral view of depth cutting diamond bur used to control thickness of the facial tooth preparation.

Figure 7

Fig 7. Occlusal view of minimally invasive 0.3-mm preparation at the cervical margin of tooth No. 8.

Figure 8

Fig 8. Frontal view of the 360-degree veneer preparations on the maxillary canines, lateral incisors, and central incisors.

Figure 9

Fig 9. Facial view of the final restoration design.

Figure 10

Fig 10. Recreated example of printed burnout molds ready for the investing/pressing process.

Figure 11

Fig 11. Final restorations fabricated in zirconia-reinforced lithium disilicate on the printed model.

Figure 12

Fig 12. Application of 5% hydrofluoric acid for 20 seconds on the intaglio surface.

Figure 13

Fig 13. Application of the cleaner on the intaglio surface, followed by rinsing and drying.

Figure 14

Fig 14. Application of the silane coupling agent on the clean intaglio surface.

Figure 15

Fig 15. Fit check of restorations under rubber dam isolation.

Figure 16

Fig 16. Extraoral view after cementation under rubber dam isolation.

Figure 17

Fig 17 through Fig 19. Extraoral postoperative views after cementation: (Fig 17) frontal view, (Fig 18) left lateral view, (Fig 19) right lateral view.

Figure 18

Fig 17 through Fig 19. Extraoral postoperative views after cementation: (Fig 17) frontal view, (Fig 18) left lateral view, (Fig 19) right lateral view.

Figure 19

Fig 17 through Fig 19. Extraoral postoperative views after cementation: (Fig 17) frontal view, (Fig 18) left lateral view, (Fig 19) right lateral view.

Figure 20

Fig 20. Intraoral frontal view of maxilla at follow-up appointment 2 weeks post-insertion, showing a natural appearance and integration.

Figure 21

Fig 21. Final portrait of the patient with a natural-appearing smile.