Internal Characterization of a Transitional Restoration Using a Milled Hybrid- Ceramic Material

The ability to provide a long-term temporization for an individualized, full-mouth restoration is an important phase of a successful treatment plan. This step gives both the dentist and patient the confidence that a final restoration will meet the requirements of functionality and esthetics. Furthermore, when fabricating a multiple-unit case specifically for the anterior region, patients concerned with the quality and esthetics of a temporary restoration may not accept a monochromatic solution. Therefore, choosing an appropriate transitional material and a shade adjustment system is an important part of a successful treatment plan.

A new-generation CAD/CAM material, HC Block/Disk (Shofu Dental Corporation, shofu.com), in shade A2-LT/M (low translucency/block size medium) meets all the criteria of an effective long-term provisionalization (Figure 1). Composed of 61% zirconium silicate embedded in a high-temperature, high-pressure polymer matrix, a densely-packed nanofiller of HC Block/Disk forms a skeleton that uniformly absorbs masticatory forces and promotes resistance to breakdown phenomena. The high flexural strength of 191 MPa and Vickers hardness of 66 Hv0.2 make HC Block/Disk a good candidate for a vast spectrum of indications, including long-term transitional restorations and permanent anterior/posterior restorations for inlays/onlays, full-contour crowns, and implant-supported cases.

With a total milling time of 11 minutes and 30 seconds using Cerec inLab MC XL (Dentsply Sirona, dentsplysirona.com) under wet conditions, HC Block/Disk showed excellent machinability in terms of damage tolerance, wear on CAD/CAM instruments, and the ability to be milled to a very low thickness. The evidence also supports that restorations fabricated with HC Block/Disk achieve ideal marginal integrity and fit (Figure 2).

As a composite-based ceramic restorative, HC Block/Disk is highly compatible with other resin-based materials, allowing dental laboratory technicians to create highly individualized customizations with a stain system such as Lite Art (Shofu Dental) and to repair or modify with a direct or indirect restorative material such as Ceramage (Shofu Dental).

After milling, the sprue was removed and contacts and occlusion were minimally adjusted with a Dura-Green Stone (Shofu Dental). To create adequate canvas for internal characterization with Lite Art and final layering with Ceramage F-59, the unit was cut labially.

In order to provide reliable mechanical retention, first the surface of the milled restoration was roughened by sandblasting with aluminium oxide particles (about 50 to 100 μm), at 2-3 bar pressure for 10 seconds, then neatened with a clean brush without the presence of water. The cleaning process can also be conducted with oil-free compressed air.

Strong and durable chemical retention for the successive staining was obtained with CeraResin Bond Adhesive System (Shofu Dental). Initially, CeraResin Bond 1 was applied to prime the surface. After 10 seconds, CeraResin Bond 2 was added and left undisturbed for 10 seconds, then subsequently light-cured for 20 seconds (Figure 3).

The restoration was naturalized with Lite Art Stain System, which incorporates novel multifunctional monomers and photo-initiators, responsible for emulating the natural dentition's optical properties of light diffusion and anisotropy. The proprietary chemical composition of Lite Art also supports a failsafe adhesion to a variety of substrates, including direct and indirect composites, PMMA, and other resin-based materials. The high-viscosity nature of Lite Art Stains allows for a precise application and prevents waste.

The color spectrum utilized for internal staining of the restoration included (Figure 4):

• White (W) – to create decalcification spots, crack lines, and white bands; to bring out the marginal ridges; and to enhance the tips of the cusps

• Khaki (K) – to emphasize cervical and palatal areas and the developmental grooves

• Cyan (C) – to highlight and intensify translucent areas

• Orange (O) – to mirror the characteristic of interproximal contacts

To achieve the nuances and characterization effects of natural dentition, the stains were diluted with Lite Art Clear Liquid (Figure 5). A Solidilite V light-curing unit (Shofu Dental) was used to polymerize the restoration for 1 minute.

An overlay of an indirect flowable composite, Ceramage F-59, was applied with a small, flat brush to enhance the translucency, to create depth and space, and to shield the restoration from damages (Figure 6).

The final curing was carried out for 3 minutes with the Solidilite V appliance.

Minor surface contouring accentuating the morphology and texture was created with a Dura-Green Stone and a diamond bur (Figure 7).

CompoMaster (Shofu Dental), a two-step, diamond-filled abrasive system, was used to finish and pre-polish the restoration without impeding its complex anatomical details (Figure 8).

The final restoration was polished with a bristle brush and Dura-Polish Polishing Paste (Shofu Dental) (Figure 9).

To obtain the wet, glossy sheen, the unit was super-polished with a felt wheel and Dura-Polish Dia Polishing Paste (Shofu Dental) (Figure 10).

The achieved transitional restoration was fully functional and visually appealing (Figure 11).

Transitional restorations offer an excellent means of treatment. Whether prescribed as a short-term or a long-term modality, this restorative option offers an efficient and inexpensive interim solution to a variety of patients, including those undergoing periodontal therapy, the geriatric population, and dental implant users, and can be used as a phase antecedent to an indirect esthetic restoration.

In a very short time, HC Block/Disk, Ceramage, and Lite Art Stains can create a successful transitional restoration that is both functional and highly esthetic.

Abel Fernandez, CDT, MDT, is the owner of Master's Touch Dental
Laboratory in San Marcos, California.

Disclaimer: The statements and opinions contained in the preceding material are not of the editors, publisher, or the Editorial Board of Inside Dental Technology.

Shofu Dental Corporation
shofu.com
800-827-4638

1. Schriwer C, Skjold A, Gjerdet NR, Øilo M. Monolithic zirconia dental crowns. Internal fit, margin quality, fracture mode and load at fracture. Dent Mater. 2017 Sep;33(9):1012-20.

2. Miyazaki T, Nakamura T, Matsumura H, Ban S, Kobayashi T. Current status of zirconia restoration. J Prosthodont Res. 2013 Oct;57(4):236-61.

3. Ramos CM, Cesar PF, Bonafante EA, et al. Fractographic principles applied to Y-TZP mechanical behavior analysis. J Mech Behav Biomed Mater. 2016 Apr;57:215-23.

4. Munoz EM, Longhini D, Antonio SG, Adabo GL. The effects of mechanical and hydrothermal aging on microstructure and biaxial flexural strength of an anterior and a posterior monolithic zirconia. J Dent. 2017 Aug;63:94-102.

5. Zhang F, Inokoshi M, Batuk M, et al. Strength, toughness and aging stability of highly-translucent Y-TZP ceramics for dental restorations. Dent Mater. 2016 Dec; 32(12):e327-e337.

6. Pinto PA, Colas G, Filleter T, DeSouza GM. Surface and mechanical characterization of dental yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) after different aging processes. Microsc Microanal. 2016 Dec;22(6):1179-88.