A Solution for Patients with Allergies and Bruxism

A full-arch mandibular impression, a full-arch maxillary opposing impression, a bite registration, and intraoral images were provided by the clinician to the dental laboratory technician. Custom shade was acquired by the technician before the preparation of the tooth to avoid dehydration.

Digital design was attained by scanning the model with emphasis on tooth No. 18 and adjacent tooth No. 19 (Figure 1 and Figure 2). A bite registration of the opposing was prepared and scanned, providing a view of the antagonist, which was acquired and trimmed digitally. The software proposed the designed restoration with a correct Curve of Spee and Curve of Wilson. The proposed restoration displayed a red area indicating that the opposing tooth would need to be lightly adjusted intraorally by the clinician during cementation of the crown (Figure 3).

The restoration was accepted and milled under wet conditions on a Sirona inLab MC XL using the Shofu Block HC for Cerec, shade A2-2L. Shofu Block/Disk HC offers better machinability in terms of time, damage tolerance, wear of milling diamond burs, and the ability to be fabricated at a low thickness, which in this case was necessary for the occlusal area (Figure 4).

With a compressive strength of 472 MPa, a high flexural strength of 191 MPa, and Vickers hardness of 66 HV0.2, Shofu Block HC is an excellent candidate to restore tooth No. 18. The hardness of the material demonstrates values closer to dentin, preventing excessive antagonist wear, which is one of the patient's concerns due to severe bruxism. Additionally, Shofu Block HC lacks the presence of metal, allowing it to be the best choice of material for this patient. With superior flexural strength and low flexural modulus, it has excellent capability to diffuse stress, making it an ideal alternative.

Grinding off the sprue, making minor adjustments, and contouring the milled unit are achieved with Dura-Green Stone abrasives (Figure 5 and Figure 6). Starting with the removal of the sprue, Dura-Green Stone IC9 HP is preferred. No adjusting on the intaglio is required as the milled HC crown came out clean of debris; therefore, the sitting of the crown to the die stone model presented an outstanding adaptation. The mesial contact was slightly adjusted and minor contouring of the overall surface was obtained with Dura-Green Stone WH6 HP. To minimally adjust the occlusion, a Dura-Green Stone FL2 HP was used. Fine small diamonds worked perfectly to accentuate the occlusal morphology.

To provide mechanical retention the unit is lightly sandblasted with 50-µm aluminum oxide at 2 bar pressure, rinsed with alcohol, and air-hose cleaned without the presence of oil or water. CeraResin Bond 1 and 2 were applied over the entire surface according to the manufacturer's instructions with the purpose of achieving a chemical bond between the internal stains and the HC restoration.

The internal naturalization is proceeded to enhance the different nuances of the crown according to the custom shade. In this case Lite Art Stains were introduced to the milled restoration (Figure 7). These modifiers are compatible with indirect composites, PMMA, resin-based materials for CAD/CAM, and hybrid ceramics. The high viscosity allows precise application over the different areas of the crown, thus making it manageable to apply. Solidilite V light-curing chamber is used for 1 minute to cure the stains.

To overlay and protect the internal stains, Ceramage UP T-Glass was used to cover the buccal, lingual, and interproximal areas (Figure 8). On the occlusal area, Ceramage UP OC was used on triangular ridges and cusp tips. Next, 56 enamel was utilized on the buccal incisal one-third to enhance the translucency of the two-layer crown and to protect the naturalization on the secondary anatomy and fossa. Once again, the Solidilite V light-curing unit was used for 3 minutes to polymerize the crown.

CompoMaster polishers, a simple two-step system, produced a smooth finish. Proceeding with the final step, Dura-Polish is used with a soft bristle brush to polish the crown. Dura-Polish DIA is used with a felt wheel to super-polish the unit to a high luster. The intaglio of the Shofu HC crown was treated by sandblasting it with 50-µm aluminum oxide, followed by steam cleaning, ultrasonic water bath, ethanol cleaning, and Shofu HC Primer.

This hybrid ceramic is an alternative restorative to rehabilitate permanent single crowns on patients of all ages. It is ideal for those who have severe erosion of teeth with minimal tooth structure, allergies to alloys, or advanced bruxism. Shofu's novel Block HC provided a canvas for artistry and beauty in restoring tooth No. 18 (Figure 9 and Figure 10).

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

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

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