Bonded Ceramic Onlays

Case Presentation

A patient presented to the office with a large, cariously involved amalgam on tooth No. 3. While it was initially suspected that a full-coverage crown might have been necessary, upon removal of the failing restoration and recurrent decay it was determined that there was sufficient remaining tooth structure to permit a more conservative porcelain onlay. The mesial-buccal cusp was completely undermined with decay; therefore, it was reduced for porcelain coverage. A final impression and a bite registration were taken and a temporary restoration was placed. The patient returned in 2 weeks for cementation of an all-ceramic, laboratory-processed porcelain onlay.

The patient was anesthetized and the provisional restoration was removed (Figure 1. The restoration was inspected for proper hydrofluoric acid-etching and for fit on the master model (Figure 2. It was tried in with a small amount of water and assessed for fit, marginal seal, and interproximal contact. Once verified for accuracy in the mouth, the inner surface was cleaned with acetone and silanated (Figure 3.

RelyX Unicem 2 Automix cement in a translucent shade was chosen to cement this case for its no-mix, easy to dispense delivery system, high bond strengths, excellent handling properties, color stability, adequate working time, and ease of clean-up of the residual cement.

A rubber dam was placed and tooth No. 3 was ligated around the cervical neck with floss for ideal isolation and to ensure that the dam material would not interfere with the seating of the restoration. The cavity preparation was cleaned with Gluma® Desensitizer (Heraeus, http://www.heraeus-dental-us.com) and air-dried. Because of the open cavity form, the intraoral tip of the cement was attached to the wide mixing tip to ensure full distribution along all aspects of the preparation. The intraoral tip was placed directly into the cavity form and an even layer of RelyX Unicem 2 Automix cement was expressed with gentle finger pressure (Figure 4. The all-ceramic onlay was pulled from the working die using a wax applicator and placed into the preparation. An amalgam condenser was used to firmly seat the restoration (Figure 5.

Using the “wave technique,” an LED curing light was waved over the restoration from the buccal and lingual surfaces for approximately 5 seconds. This technique begins the polymerization of the residual cement, but only to the gel/semi-solid state. Excess residual cement was then easily removed with a sickle scaler (Figure 6 and the interproximal material was cleared with floss (Figure 7. More than adequate working time with full operatory lighting enabled complete removal of the residual cement in less than 2 minutes. Once all excess resin cement was removed, a glycerin gel (DeOx®, Ultradent Products, Inc, http://www.ultradent.com) was placed over all of the cavosurface margins to inhibit the formation of an air-inhibited layer at the cement interface, which can lead to marginal ditching and staining by chromagenic foods and beverages. The final light-cure of 1 minute per surface was initiated (Figure 8. A composite-impregnated cup (Enhance®, DENTSPLY Caulk, http://www.caulk.com) was used to remove and smooth any bonded excess along the margins. The rubber dam was removed and the occlusion was refined with a fine diamond.

Figure 9 shows the completed restoration. Note that the cement’s translucent shade permitted a seamless, vital, monoblock restoration while conserving tooth structure.

Conclusion

Conservative, well-bonded, all-ceramic inlays and onlays are often the ideal restorations for moderate to large cavity forms. The success of these restorations often relies on the efficiency and durability of the bond interface between the tooth and the ceramic. RelyX Unicem 2 Automix cement exhibits ideal handling, physical properties, and ease of clean up, coupled with exceptional bond strength, color stability, and hydrophobic seal of dentinal tubules. The new Automix dual-barreled syringe and choice of two sizes of dispensing tips make this product an excellent choice for not only all-ceramic inlays and onlays, but all-ceramic crowns and laboratory-processed composite as well.