A Reliable Bonding Protocol for Single Tooth or Complex Restorations

One of the most common frustrations voiced by clinicians regarding bonding procedures is the lack of reliability. However, this is often a result of operator error.¹ Good bonding protocols begin and end with rubber dam isolation. Because restorative dental materials are hydrophobic, ensuring an isolated field should be the first step in every bonding procedure.²

Case Report

A patient presented to the practice for the final restoration of tooth No. 5, which had previously been prepared, including an immediate dentin sealing procedure, and then fitted with a provisional restoration^.3 After the provisional restoration was removed, rubber dam isolation was achieved, clamps were placed (B4 Clamps, Coltene), and the bonding surface was cleaned with 27 μm aluminum oxide particles at 40 psi (PrepStart^™, Zest Dental Solutions) (Figure 1).^4,5

When cementing indirect restorations under rubber dam isolation, it is essential to ensure adequate visualization of and access to the margins. The use of accessory clamps helps to accomplish this task. Although most rubber dam clamps in circulation are designed for endodontic procedures, the ones used in this case were selected because they are designed for restorative procedures, allowing for tight approximation and inversion of the rubber dam around the tooth being isolated. Prior to starting a bonding protocol, clinicians should remove all remnants of provisional cement and debris and confirm the passive fit of the final restoration. If a restoration is not able to seat fully, the clamps should be adjusted, and the restoration should be tried in again until the fit is confirmed (Figure 2). Once passive fit is confirmed and adequate inversion and isolation are maintained, the bonding protocol may commence.

To provide the necessary microretention for successful bonding in this case, the tooth was etched with a high viscosity phosphoric acid etchant (Select HV^® Etch w/ BAC, BISCO) and thoroughly rinsed (Figure 3). The high viscosity of this material facilitates precise placement and reduces the risk of it running onto the dentin and adjacent teeth, which makes it ideal for the selective etch technique. After rinsing, it is critical to not overdry the etched tooth. The excess water needs to be removed to achieve the highest possible bond strength, but care should be taken to prevent desiccation.

Following etching, the bonding protocol continued with the placement of a universal adhesive (All-Bond Universal^®, BISCO). Two separate coats were applied, and for each, the adhesive was scrubbed onto the preparation for 10 to 15 seconds using a microbrush to ensure adequate impregnation of the material into the tooth surface (Figure 4). Once the second coat was completed, the adhesive was air thinned for 10 seconds to evaporate the solvent.⁶ Excess solvent should be evaporated by thoroughly air-drying with an air syringe for at least 10 seconds; there should be no visible movement of the adhesive (Figure 5). After the solvent was completely evaporated, the surface exhibited a uniform, glossy appearance, and the adhesive layer was then light cured for 10 seconds.

Because the final restoration in this case was being delivered using rubber dam isolation, the adhesive surface was at minimal risk for contamination during the time that the intaglio surface of the final restoration was treated for delivery. Understanding the requirements of the restorative material being used is essential for proper preparation of the intaglio surface. In this case, a lithium disilicate (IPS e.max^® CAD, Ivoclar) restoration was fabricated in house using an intraoral scanner (Planmeca Emerald^® S, Planmeca) and a milling machine (Planmeca PlanMill^® 40 S, Planmeca). The intaglio surface of the restoration was etched for 90 seconds with a 9.5% buffered hydrofluoric acid gel (Porcelain Etchant [9.5% HF], BISCO) and then copiously irrigated. Next, the intaglio surface was cleaned with the high viscosity phosphoric acid etchant for 30 seconds and copiously irrigated again to remove any potential contaminants. A silane primer (Bis-Silane^™, BISCO) was then applied, and the restoration was placed in a dark box for 30 seconds. Silane is a coupling agent that is used to improve both the mechanical and chemical bonds between porcelain restorations and resin cement. Furthermore, it helps to protect restorations from contamination.

For final delivery, a dual-cure universal adhesive resin cement (Duo-Link Universal^™, BISCO) was applied to the intaglio surface of the restoration, and it was seated using light finger pressure (Figure 6). A clean microbrush was then used to remove the excess cement from around the margins on the buccal and palatal aspects to ensure that the restoration was fully seated. Once complete seating was confirmed, a curing light was used to tack cure the buccal and palatal aspects for approximately 3 seconds each while maintaining finger pressure. All of the visible excess cement was removed, and the interproximal contacts were verified (Figure 7). The restoration was then fully light cured for 20 seconds on both the buccal and palatal aspects. Because the universal adhesive resin cement used is a dual-cure material, the restoration was allowed to fully chemically cure for 5 minutes before the clamp and rubber dam were removed and all of the remaining excess cement was removed with a scaler and the margins were finished (DET3F FG Fine Needle Diamond, Brasseler) (Figure 8).

Conclusion

Good restorative dentistry stems from good systems, and good bonding stems from good isolation. Without one, clinicians cannot have the other. Maintaining control during all procedures allows clinicians to provide patients with consistent and reliable restorative outcomes. Whether a case involves delivering a single porcelain restoration or an entire arch, establishing and staying true to good systems is how clinicians optimize patient care.