Intraoral Repairs: Fixing PFMs Effectively and Efficiently

Intraoral Repairs: Fixing PFMs Effectively and Efficiently. Photo Courtesy of Nestor / stock.adobe.com/

Intraoral repairs can be a cost-effective and fast alternative to replacement when a patient comes in with a chip. Knowing how to do one properly and efficiently can help the patient with their tooth esthetics and function and financially.

In a Dental Talk Viva Learning podcast, Rolando Nunez, DDS, MSc, and Manager of Clinical Affairs for BISCO, says that most of the intraoral repairs he encountered in his practice were porcelain-fused-to-metal (PFM) restorations.¹A literature review confirms that these are frequent occurrences, with a calculated average incidence of 27 percent in fixed dental prostheses between 5 and 14 years old. Moreover, the most frequent problem is a chip in the porcelain, at a 34 percent rate by some estimates. When assessing the fracture, here are the 3 types you will likely see:²

1. Static Fracture: the porcelain is broken but still in place
2. Cohesive Fracture: a chipping fracture in the body of the porcelain
3. Adhesive Fracture: bonding failure either between the veneer and the core porcelain or the porcelain and metal substrate

It is incumbent upon the dentist to determine how to move forward. Some fractures can be polished, while others need repair. The most severe need replacement occurs when the fracture extends into a function area, recontouring will change the anatomic form too much, there is a high risk of thermal damage to the pulp during recontouring, or it will not look good.³

Jeff Lineberry, DDS, FAGD, AAACD, says he sees fewer PFMs in his practice, and when he does, many are failing, often because of their age. As a result, Dr Lineberry tends to default replacing a PFM restoration with a different, more modern material, usually lithium disilicate or zirconia, depending on the case and the location of the restoration.

“Usually, when they are failing, I am replacing them,” Dr Lineberry says. “Lithium disilicates is one of the happy mediums where we have an excellent restoration that’s durable and esthetic. Zirconiais an option as well and it is durable, and they are more esthetic than PFMs. However, with more esthetic zirconia nowadays, the overall strength of it is reduced.”

Another significant consideration when choosing between repairing and replacing a failing PFM restoration is how the fracture happened. Dr Nunez explains that it is essential to determine what caused the fracture before you move forward with a repair. If it was a hockey puck to the mouth, then you can move forward with the repair. However, if the fracture occurred because of chronic habits, flaws with the restorative materials, or occlusion problems, dentists should address that problem first so the repair will last.⁴

“Many times, when restorations are chipped or broken, that’s a functional issue, like too much pressure and so forth, which leads to premature failure of the restoration,” Dr Lineberry agrees.

Once you are ready to proceed with the intraoral repair and have isolated the area, fixing it depends on the fracture. Static Fractures often only need polishing. The polishing repair technique works best in the posterior when the chip is small and doesn’t affect esthetics or function. When the chip is more extensive, clinicians should protect the tooth pulp and remaining porcelain from heat.⁵

However, Cohesive Fractures require a bit more technique. These can either demand the recementing of the chipped-off material or by building up composite resin. In either case, the restoration substrate requires surface modification and roughening.⁶

Intraoral repairs require you to create either mechanical or chemical retention depending on the substrate. Per the Balkan Journal of Stomatology, treating the ceramic surface starts by removing the glazed layer with a diamond bur or sandblast and acid-etch (or both) to expose the ceramic layer underneath, which reacts better and has a larger contact surface area. The authors recommend either a 37 percent phosphoric acid, a 5-10 percent hydrofluoric acid, or a 1.23 percent acidulate phosphate fluoride for the acid etch. However, it is essential to isolate to protect the soft tissues from damage when using hydrofluoric acid. For metal substrate, they recommend sandblasting and metal primer. Tin plating could enhance the bond strength for high-noble or noble metal surfaces.⁷

Dr Nunez says that a silane coupling agent is essential after roughening the ceramic surface to achieve a good chemical bond to the porcelain. Moreover, he says that it should be pure silane, not a product that contains silane. Also, Dr Nunez cautions clinicians to be careful of sandblasting in intraoral repairs where both porcelain and metal are exposed because the sandblasting can create microcracks in the porcelain surface. Instead, he recommends roughening the surface of the metal with a diamond bur followed by primer containing MDP (Methacryloyloxydecyl dihydrogen phosphate), a popular monomer in many universal adhesive primers. However, if you have both surfaces that need treatment, it is indicated that you should apply the silane first to the ceramic surface and then the MDP to the metal surface.⁸

If the clinician is going to reattach the porcelain chip, then it can be rebonded at this point. However, suppose the clinician uses composite to repair the restoration, and the restorative surface requires metal masking. In that case, it is essential to use an opaquer first before layering translucent resins on top of it. The authors in the Balkan Journal of Stomatology recommend a flowable resin in an opaque shade.⁹

BISCO has an Intraoral Repair Kit indicated to repair PFM or Zirconia/Alumina restorations, porcelain & lithium disilicate restorations, and direct and indirect composite restorations. It comes with Z-Prime Plus, Porcelain Primer, Porcelain bonding Resin, Dual-Cured Opaquer, Porcelain Etchant (9.5% HF), and Barrier Gel. Then, you use the composite system you like to complete the restoration from there.¹⁰ Dr Nunez explains that the Dual-Cure opaquer is essential because it allows you to cure it with the light to keep in place, but the self-cure properties will continue to polymerize the material and assure a depth of cure. This curing continuation is essential for the material closest to the metal surface.¹¹

3M ESPE also has an intraoral repair system; the CoJet™ System is indicated for use with resin nano-ceramic, metal, ceramic and composite surfaces of indirect restoration. It includes CoJet™ Sand, 3M™ ESPE™ Sil, Visio™ Bond, Sinfony™ Opaquer Powder, Sinfony™ Opaquer Liquid, Brush Handles, and Disposable Brush Tips.¹²

A 2015 study by The Journal of Advanced Prosthodontics compared the 2 systems for bond strength using a diamond bur to roughen the surface and airborne particle abrasion. The authors suggested that the BISCO system performed well in Cohesive Fractures contained to porcelain substrate and that the 3M system did better when the fractures extended to metal surfaces.¹³

In his North Carolina practice, Dr Lineberry doesn’t remember the last time he repaired a PFM. However, he does repair restorations with a zirconia substructure with porcelain on top of it. While there are specific bonding protocols for zirconia, Dr Lineberry says most of it is micromechanical.

“Things stick to rough surfaces better than smooth surfaces,” Dr Lineberry says, adding that he uses air abrasion on Zirconia substrates.

When he has done PFM restoration in the past, Dr Lineberry uses an air abrasion on the exposed metal substrate also. After thorough cleaning of the exposed metal, he uses bonding agent on the metal, followed by an opaquer or very white composite to keep the metal from showing through the restorations. Forgoing the use of an intraoral repair kit, Dr Lineberry uses an assortment of materials for his repairs, but notes that he tends to reach for Scotchbond™ Universal Plus Adhesive (3M) or G-Premio Bond™ (GC America) for his bonding agent.

“It depends on the situation,” Dr Lineberry says about the materials he uses for repairs.

Dr Lineberry says that many clinicians are steering clear of using hydrofluoric acid intraorally, even though it was commonly used in the past. While it creates a strong bond, it is toxic and can damage the oral cavity. He says there are a lot of great conditioning agents for porcelain that work well.

“I’m kind of old school, so a lot of times when I condition porcelain, I use silanizing agent.Will they hold up? That’s a great question,” Dr Lineberry says of the porcelain conditioning agents. “Overall, you have to address any functional issues that caused the failure, and, in my opinion, you still have to rely upon micro-mechanical retention rather than bonding.”

References

1. Klein, DDS P. The First Aid Kit for Intraoral Repairs. Dental Talk Viva Learning. Published 2021. Accessed September 9, 2021. https://vivalearning.com/member/podcast.asp?x_podcastId=169.
2. Aslam A, Hassan S, Nayyer M, Ahmed B. Intraoral repair protocols for fractured metal-ceramic restorations - Literature review. Scielo.org.za. Published 2018. Accessed September 9, 2021.http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0011-85162018000100008.
3. Aslam A, Hassan S, Nayyer M, Ahmed B. Intraoral repair protocols for fractured metal-ceramic restorations - Literature review. Scielo.org.za. Published 2018. Accessed September 9, 2021http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0011-85162018000100008..
4. Klein, DDS P. The First Aid Kit for Intraoral Repairs. Dental Talk Viva Learning. Published 2021. Accessed September 9, 2021. https://vivalearning.com/member/podcast.asp?x_podcastId=169.
5. Aslam A, Hassan S, Nayyer M, Ahmed B. Intraoral repair protocols for fractured metal-ceramic restorations - Literature review. Scielo.org.za. Published 2018. Accessed September 9, 2021. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0011-85162018000100008.
6. Aslam A, Hassan S, Nayyer M, Ahmed B. Intraoral repair protocols for fractured metal-ceramic restorations - Literature review. Scielo.org.za. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0011-85162018000100008. Published 2018. Accessed September 9, 2021.
7. Solid is, K., Gerasimou, P. and Boutsiouki, C., 2012. Intraoral Ceramic Restoration Repair Techniques: Report of 3 Cases. [online] Researchgate.net. [Accessed 9 September 2021]. Available at: <https://www.researchgate.net/publication/268279790_Intraoral_Ceramic_Restoration_Repair_Techniques_Report_of_3_Cases>
8. Klein, DDS P. The First Aid Kit for Intraoral Repairs. Dental Talk Viva Learning. Published 2021. Accessed September 9, 2021. https://vivalearning.com/member/podcast.asp?x_podcastId=169.
9. Solid is, K., Gerasimou, P. and Boutsiouki, C., 2012. Intraoral Ceramic Restoration Repair Techniques: Report of 3 Cases. [online] Researchgate.net. [Accessed 9 September 2021]. Available at: <https://www.researchgate.net/publication/268279790_Intraoral_Ceramic_Restoration_Repair_Techniques_Report_of_3_Cases>
10. Intraoral Repair Kit | BISCO Dental. Bisco.com. Accessed September 9, 2021. https://www.bisco.com/intraoral-repair-kit/.
11. Klein, DDS P. The First Aid Kit for Intraoral Repairs. Dental Talk Viva Learning. Published 2021. Accessed September 9, 2021. https://vivalearning.com/member/podcast.asp?x_podcastId=169.
12. CoJet™ System: Intraoral Repair and Surface Pre-treatment. multimedia.3m.com. Accessed September 9, 2021. https://multimedia.3m.com/mws/media/814608O/3m-cojet-system-intraoral-repair-and-surface-pre-treatment-strong-bonds.pdf.
13. Yoo JY, Yoon HI, Park JM, Park EJ. Porcelain repair - Influence of different systems and surface treatments on resin bond strength. J Adv Prosthodont. 2015;7(5):343-348. doi:10.4047/jap.2015.7.5.343