Repair or Partial Replacement of LS2-Bonded Onlays

Drs. Jose-Luis Ruiz and Raymond L. Bertolotti
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Partial-coverage, supragingival bonded onlays are restorations that are more minimally invasive and healthier for the tooth and patient than traditional full crowns. Research and experience have demonstrated the excellent durability of bonded pressable feldspathic porcelain onlays,1 but when using stronger bonded lithium disilicate (LS2) (IPS e.max [Ivoclar Vivadent]), their durability is increased.2 The authors of both of these referenced papers report years of use and virtually no failures.1,2

Despite this, bonded onlays can fail for several reasons, such as improper bonding cementation procedures (leading to secondary caries) and, of course, fractures. A common reason for failure is secondary caries associated with bleeding during cementation, often on restorations with subgingival margins, which drastically complicates bonded cementation. Supragingival restorative techniques can improve the success of bonded dentistry. Supragingival protocol and techniques have been previously discussed3 and can obviously prevent this cementation problem.

After more than 20 years of practicing supragingival minimally invasive dentistry and performing tens of thousands of these restorations, Dr. Ruiz has limited the use of full crowns with partial coverage onlays and veneers. He reports having had to repair or replace a very small number of bonded onlays, including lithium disilicate. While removing a cemented feldspathic onlay is not very difficult, removing a bonded lithium disilicate onlay can prove to be a very difficult, invasive, tooth-traumatizing, and frustrating procedure.

Figure 1. Broken porcelain veneer. Figure 2. Small disto-facial-incisal porcelain partial replacement.
Figure 3. Photo, 17.5 years post repair. (Courtesy of Dr. Bertolloti.)

In addition, bonded onlays are often partially intracoronal restorations, which negates the ability to create a notch and split open the restoration as can be done with extracoronal crowns.

These failures can lead to the need for full replacement, but they can be repaired in some cases. Dr. Bertolotti, a pioneer of adhesive dentistry, has been teaching techniques to repair and predictably bond new porcelain to broken intraoral porcelain for decades, demonstrating long-term durability.

The repair of a broken porcelain veneer incisal edge is illustrated here, using only alumina blasting, no hydrofluoric (HF) acid etching, and the combination of Clearfil Porcelain Bond Activator and Photo Bond (Kuraray) (Figures 1 to 3). The implementation of this technique can be of great value when managing failing onlays. Success with intraoral repairs depends greatly on the proper conditioning of the different substrates, enamel, dentin, and porcelain.4 The best conditioning for lithium disilicate has been extensively researched.5 While many have shown that etching with 5% to 9% HF acid for 20 seconds, followed by silane, provides very predictable and successful results, Llobell et al6 showed that Clearfil Porcelain Bond Activator, even without HF acid etching, outperformed etching and silane.7 Complexity occurs because intraoral repair requires the proper adhesion of surfaces with different conditioning requirements, enamel, dentin, and porcelain, which can negatively interact with each other. Using Clearfil SE Protect (Kuraray) combined with Clearfil Porcelain Bond Activator instead of silane facilitates this process, as this mixed adhesive will work for both teeth and porcelain. Kameyama et al8 also showed remarkable results with this protocol.

REPAIRING A LITHIUM DISILICATE ONLAY
When the secondary caries is on a facial or lingual margin, where access is easy, repairing the restoration with composite may be the most reasonable option. It will be the most minimally invasive, most simple, and least costly option. When performed correctly, it is very predictable and will provide a few years of service. Because of the difference in expansion and contraction of composite and porcelain, grooving or staining at the porcelain-composite interface may show with time, and the patient should be aware of this fact. While it is not the most durable solution, the simplicity, cost-effectiveness, and ability to be repaired multiple times during the long life of the entire bonded onlay restoration make it a very reasonable option.

The following technique will provide a simple and reliable repair to a failing restoration margin:

1. Remove the leaky margin and secondary caries, followed by alumina blasting the porcelain margin to be repaired with a Microetcher (Zest Dental Solutions). Alternatively, roughen porcelain with a course diamond (Figure 4).

2. Carefully apply Porcelain Etch (Ultradent Products), a viscous, buffered 9% HF acid, on the porcelain surface to be repaired. For IPS e.max, the time will be 20 seconds. The viscosity of this material makes it possible to selectively etch only the porcelain and helps to avoid the tooth surface. The operator, assistant, and patient should always wear eye protection.

3. Selectively etch enamel, if present, for 10 seconds (with 37% phosphoric acid gel), always etching at least 2 mm beyond the cavo-margin and avoiding etching dentin. This can be done while waiting for the porcelain-etching time to pass (Figure 5).

Figure 4. After removing the facial leaky margin of the existing porcelain onlay. Figure 5. Twenty seconds of hydrofluoric (HF) acid etching porcelain and 10 seconds of phosphoric acid etching enamel.
Figure 6. Buffering of the HF acid etch with EtchArrest (Ultradent Products) for safe rinsing and disposal. Figure 7. The repair after finishing and polishing.

4. After 20 seconds, apply EtchArrest (Ultradent Products), sodium bicarbonate, and calcium to neutralize the HF acids and make it safe for rinsing, following the manufacturer’s instructions (Figure 6).

5. Wash and fully dry, and since dentin has not been etched, there is no risk of the dentin collapsing by overdrying.

6. Apply Clearfil SE Protect primer (bottle 1) mixed with Clearfil Porcelain Bond Activator in a 1:1 ratio to enamel, dentin, and porcelain for 25 seconds, followed by fully evaporating the primer with air.

7. Apply Clearfil SE Bond (bottle 2) over dentin, enamel, and porcelain and light cure.

8. Use Majesty ES 2 Flow (Kur­aray) on the surface and for light curing, allowing enough space for a final layer of composite.

9. Apply the desired shade of Majesty ES 2 restorative composite to restore the entire missing part and cure.

10. Finish and polish (Figure 7).

Figure 8. Illustration of large secondary caries forming on the cervical margin. Figure 9. After removing the entire distal marginal ridge, allowing for proper access to remove caries and repair damage using supragingival restorative techniques.
Figure 10. After damage repair and beveling.

PARTIAL REPLACEMENT OR VENEERING OF A BONDED ONLAY
Dr. Ruiz has veneered porcelain to repair or aesthetically enhance old PFM bridges and crowns hundreds of times with durability matching those of new restorations. This technique has also been used occasionally for the partial replacement of veneers and bonded onlays. When a bonded onlay fails due to color, shape, or secondary caries on the proximal-cervical margins, the restoration usually needs replacement. As previously discussed, the full removal of a bonded onlay can be very traumatizing, so a partial replacement or veneering can be the most minimally invasive and a healthier way to manage these cases. This all assumes that the remaining restoration has been deemed healthy.

When secondary caries on the proximal-cervical margins create an access and visibility problem (Figure 8), it is desirable to remove the entire proximal ridge of the existing restoration, allowing for proper visibility and the ability to repair the damage (Figure 9). Cervical caries can be repaired using “enamel preservation” or “margin elevation techniques” to achieve a supragingival margin, which will drastically increase predictability at cementation. Supragingival restorative techniques have been discussed in previous articles.9 Create a deep bevel reduction of approximately 2 to 3 mm at the occlusal cavo-margin, which extends to the facial and lingual of the existing restoration (Figure 10). When the reason to replace the restoration is color or shape, placing a bonded veneer over the facial surface of the existing porcelain restoration and tooth will be the minimally invasive alternative to a full replacement. A half-millimeter-deep veneer preparation will suffice in these cases. After preparation, take a final impression and temporize.
The following technique will provide a reliable and straightforward final bonding cementation procedure for the section being replaced:

1. On the day of the bonded cementation, and after removing the provisional, alumina blast intraorally. The composite buildup and the porcelain are to be repaired using a Microetcher. Alternatively, roughen the porcelain and build-up composite with a course diamond.

2. Follow steps 2 to 6 from the repair protocol.

3. Apply Clearfil SE Bond (bottle 2) over dentin, enamel, and porcelain. Do not light cure.

4. After preparing the intaglio surface of the IPS e.max restoration, apply Panavia V5 cement (Kuraray) on the restoration and seat.

5. Cure, finish, and polish.

CONCLUSION
While there is limited research on the durability of intraoral repairs or the partial replacement of bonded porcelain and IPS e.max restorations, there is a considerable amount of research, as well as clinical experience, on surface treatment. The increased simplicity, cost efficiency, and minimally invasive nature of these procedures greatly benefit patients as well as dentists. Ultimately, if a repair fails, there is always the option of full replacement.


References

  1. Ruiz JL, Christensen GJ, Sameni A, et al. Clinical performance of bonded ceramic and resin-based composite inlays and onlays using a self-etch bonding system: a 51-month report. Inside Dentistry. 2007;3:62-65.
  2. Malament KA, Natto ZS, Thompson V, et al. Ten-year survival of pressed, acid-etched e.max lithium disilicate monolithic and bilayered complete-coverage restorations: performance and outcomes as a function of tooth position and age. J Prosthet Dent. 2019;121:782-790.
  3. Ruiz JL. Supragingival dentistry: easier and healthier restorative care. Interview by Damon Adams. Dent Today. 2010;29:90-97.
  4. Kimmich M, Stappert CF. Intraoral treatment of veneering porcelain chipping of fixed dental restorations: a review and clinical application. J Am Dent Assoc. 2013;144:31-44.
  5. Peumans M, Hikita K, De Munck J, et al. Effects of ceramic surface treatments on the bond strength of an adhesive luting agent to CAD-CAM ceramic. J Dent. 2007;35:282-288.
  6. Llobell A, Nicholls JI, Kois JC, et al. Fatigue life of porcelain repair systems. Int J Prosthodont. 1992;5:205-213.
  7. Colares RC, Neri JR, Souza AM, et al. Effect of surface pretreatments on the microtensile bond strength of lithium-disilicate ceramic repaired with composite resin. Braz Dent J. 2013;24:349-352.
  8. Kameyama A, Haruyama A, Tanaka A, et al. Repair bond strength of a resin composite to plasma-treated or UV-irradiated CAD/CAM ceramic surface. Coatings. 2018;8:230.
  9. Ruiz JL. Avoiding subgingival margins for healthier dentistry: using a supragingival preparation protocol. Dent Today. 2015;34:82-86.

Dr. Ruiz is founder of the Los Angeles Institute of Clinical Dentistry, former course director of the University of Southern California’s Esthetic Dentistry Continuum, associate instructor at Gordon J. Christensen – Pratical Clinical Courses in Utah, and an independent evaluator for Clinicians Report. Dr. Ruiz is the author of Supra-Gingival Minimally Invasive Dentistry with Dr. Ray Bertolotti and is the author of many research and clinical articles. He has been named as one of Dentistry Today’s Leaders in CE since 2006. He is also in private practice in the Studio District of Los Angeles. He can be reached at
drruiz@drruiz.com.

Dr. Bertolotti received his DDS degree from the University of California, San Francisco, after working as a PhD metallurgical and ceramic engineer at Sandia National Laboratories. Dr. Bertolotti is perhaps best known for introducing “total etch” to North America in 1984. He also introduced Panavia in 1985, tin plating in 1989, self-etching primers in 1992, and HealOzone in 2004. He is founder of Danville Materials (now part of Zest Dental Solutions) and was director of research. The sectional Contact Matrix system, MicroPrime B, MicroEtcher sandblasting, and intraoral tin plating are also his developments. He is a well-known international lecturer, having presented at invited lectures in more than 30 countries. He can be reached via email at rbertolott@aol.com.

Disclosure: The authors report no disclosures.

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