Removing All-Ceramic Restorations With Lasers

INTRODUCTION
I am now in my 14th year of using dental laser technology in my practice. Lasers have changed my professional life as a general dentist and they are my instruments of choice for caries removal, biopsies, soft-tissue cosmetics, frenectomies, lesion destruction and healing, troughing for crown and bridgework, hemostasis for extractions, and to treat periodontitis (with laser-assisted new attachment procedure [LANAP]), to name a few of the myriad of laser uses. Now, in addition to the above-mentioned procedures, I utilize a hard-tissue laser to remove bonded veneers and other all-ceramics, including CAD/CAM zirconia restorations.

BRIEF HISTORICAL BACKGROUND
Dental lasers work utilizing a beam of light. The beam is amplified light energy. The energy is produced in the laser’s resonator, then directed into a fiber-optic system, next moving to the tip of the laser handpiece and, finally, precisely onto the biologic tissue. All this is done at the speed of light. This contact creates a thermal interaction. Different lasers operate at specific wavelengths of light, and have different affects on the soft tissue, tooth enamel, dentin, and caries.
I first purchased a soft-tissue variable-pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) dental laser in 1999. Hard-tissue lasers had come to dentistry in 1997. This invention gave clinicians an alternate tool to high-speed handpieces, with the ability to reduce or eliminate vibrations, the sound of the handpiece, microfractures, and some of the discomfort. Procedures are done with reduced amounts (or none) of local anesthetic for many procedures. I bought my first Erbium:YAG (Er:YAG) laser treatment center in 2003.
I currently use a variety of free-running, true-pulsed (non-diode) lasers in my general dental practice. To remove caries from teeth, hard-tissue lasers (such as the Fotona PowerLase AT Er:YAG) use light energy, air, and water to replace the bur. Simply stated, the Erbium laser vaporizes the tooth decay away. My soft-tissue lasers (such as PerioLase MVP-7 [Millennium Dental) Nd:YAG) use a no-cut, nonbleeding, no stitches, laser technique to remove diseased tissues, stop infection, and allow the body to heal itself. I use an Nd:YAG laser to treat periodontitis and/or gingivitis. Both Er:YAG and Nd:YAG lasers have other soft- and hard-tissue applications.
Three cosmetic developments since 1991 have dramatically changed how I practice dentistry daily: porcelain veneers, CAD/CAM zirconia copings overlaid with porcelain (bilayered), and full-contour (solid or monolithic) zirconia restorations. The ability to bond (glass ceramics such as leucite-reinforced porcelain or lithium disilicate) or cement (zirconia) cosmetic restorations in place of using light- or dual-cured resin cements has created long-lasting restorations that will not easily become uncemented/debond. However, the resin cement-restoration interface is too strong for easy crown or bridge removal, when/if needed. (Veneers were never thought to be removable.)
Now with millions of these restorations in patients’ mouths, how are we going to treat postoperative clinical failures (endodontic, functional, and aesthetic failures, etc) that require the removal of the restoration? I have endured the time and expense of using a handpiece and diamond burs to remove stronger and stronger all-ceramic materials, and I definitely needed to find an alternative to remove bilayered and especially monolithic zirconia crowns.

Veneer and All-Ceramic Crown Removal
For the past 2 years, I have used an erbium laser to remove porcelain veneers bonded with light-cured resin cements. No anesthetic is required. The Fotona PowerLase AT Er:YAG (2,940 nm) utilizes a cylindrical quartz tip (8 mm length/one mm end diameter) in contact in the R14 handpiece or using the noncontact R02 handpiece which has a 7-mm focal distance (Figure 1). The narrowest pulse width was used (50 µsec). Settings varied from 200 to 275 mJ at 8 or 15 Hertz. A 2-to-one water to air-mix was utilized. The complete external aspect of the veneer was traced at the focal distance while firing the laser; within a minute the veneer or remaining fragments of a previously fractured veneer “pop off.” The resin cement remains bonded to the tooth. The technique is very predictable (Figures 2a and 2b).

Figure 1. Fotona PowerLase AT.

Does the technique work on zirconia bilayered restorations (porcelain layered over zirconia copings, such as Lava [3M ESPE])? In the past, I cut off an anterior bilayered zirconia bridge after the porcelain separated from the underlying zirconia coping. This involved a lot of time, diamonds, water, and suction, tapping, and prying pieces off. Now, when I need to remove a newly resin-cemented (bilayered) zirconia bridge (in this case, a Lava bridge), I use the same laser technique that was used to remove porcelain veneers. A bridge can be removed en mass and used as a cemented temporary while a new one is designed and fabricated by the dental laboratory team.
How did I handle the removal of monolithic zirconia (such as BruxZir [Glidewell Laboratories]) crowns? As an example, a patient presented with a completed molar solid zirconia crown, requiring postcementation endodontic treatment. Access was made using a handpiece and a No. 4 round diamond bur with water spray. A lot of sparking and heat resulted while creating the access opening. The root canal therapy was finished and the access restored with composite resin. This tooth was necrotic, but what would be the effect on removing a resin-cemented crown from a vital tooth with burs? Patients will certainly have future needs that may involve the removal of resin-cemented monolithic zirconia crowns, and necessitate that this is done without damaging the underlying tooth structure or causing damage to the nerve system.

CASE REPORTS
Case 1
Diagnosis and Treatment Planning—A 59-year-old female presented with dull pain to biting in the lower right. A monolithic zirconia crown (BruxZir) had been placed 6 months previously on tooth No. 30 and the pulp was now diagnosed as necrotic. Root canal therapy (RCT) on tooth No. 30 was the indicated treatment.
Options were: cut an access opening through the crown and perform the RCT, then restore the access opening with composite resin; or temporize the access opening and replace the crown at a future date; or remove the crown, do RCT, then recement the crown today.
When informed of the treatment options, the patient did not like the idea of cutting through her “new” crown. I let her know that I had the equipment and technique to remove the crown and that it would take less time to remove the crown than cut through it. For her, it was an easy decision to have the crown removed, do a one-appointment RCT procedure, seal the access, and then recement the existing crown (Figure 3).

Figure 3. Preoperative radiograph of tooth No. 30.	Figure 4. Tooth No. 30 with crown off. Note the cement remaining on prepared tooth.

Clinical Protocol—Local anesthetic (1 carpule 2% carbocaine [1/20,000 Levonordefrin]) was given for the RCT (not for the crown removal). With all the required laser safety and regulatory compliances observed, the BruxZir crown was removed using the PowerLase AT laser system with a 90° Optical Handpiece Model R14-C, utilizing an 8/1.0 Cylindrical Quartz tip.

Laser Parameters:

• Wavelength = 2,940 nm free running pulsed Er:YAG laser
• Beam delivery type = 7-mirror articulated arm
• Power = 2.0 Watts 135 mJ per pulse
• Repetition rate = 15 Hertz
• Pulse width = SSP 50 µsec
• Water 4/air 2, spray with a vacuum tip to remove water from patient’s mouth.

Only the erbium laser was used with the tip in near contact with outer surfaces of the monolithic zirconia crown. Focal distance from the fiber tip was at 0.7 mm; using the shortest pulse width (50 µsec) to increase the photo acoustic response; slow movement of tip to increase the power density; pulse repetition rate was set at a frequency of 15 pulses per second; starting on the occlusal surface, slowly painting back and forth over all surfaces; then to the buccal surface, moving back and forth, top to bottom; then to the lingual, starting at occlusal. The crown popped off and was caught in the suction tip before completing the laser treatment on all of the lingual aspect of the restoration. In less than a minute, the crown had been removed (Figures 4 to 5b).

Figure 6. Radiograph of tooth No. 30 after cement was cleaned off the tooth, root canal therapy completed.	Figure 7. The crown was recemented.

Figure 8. (Case 2) Preoperative photo.

There was no cement left in the crown; however, cement remained bonded to the prepared tooth and to the composite resin core material. Next, RCT was then done, resin cement was cleaned off the tooth surfaces and the access was sealed with composite resin (bonded). Then, the internal surfaces of the zirconia crown were sandblasted, and the crown was tried-in, adjusted, and polished. (Note: It is easier to polish solid zirconia in the lab than in the mouth.) Finally, the crown was resin cemented (Rely X Unicem 2 (A2) [3M ESPE]) (Figures 6 and 7).

Case 2
Diagnosis and Treatment Planning—A patient presented with a bilayered zirconia crown (Prismatik CZ [Glidewell Laboratories]) that had experienced fracturing of the layering porcelain just 6 weeks after it had been cemented over an implant (in tooth No. 12 position) (Figure 8). The crown had been cemented using a (self-etching, self-adhesive) resin cement.
Treatment would consist of removing the crown using an erbium laser, and returning the original impression/models to the laboratory team to remake the crown in monolithic zirconia (BruxZir). Tooth No. 12 was replaced with a 3I Osseotite Certain implant (4.0 x 11.5 mm) and a UCLA screw-retained cast gold implant abutment.
Clinical Protocol—The Prismatik CZ crown was removed using the PowerLase AT laser system with an Optical Handpiece Model R14, 8/1.0 Cylindrical Quartz tip. (Note: No local anesthetic was administered in this case.)

Laser Parameters:

• Wavelength = 2,940 nm
• Power = 1.6 Watts 200 mJ
• Repetition rate: 8 Hertz
• Pulse width: SSP 50 usec
• Water 4/air 2 spray.

The PowerLase erbium laser was used with quartz tip in contact with the ceramic, with slow movement of the tip to increase power density; pulse repetition rate was set at a frequency of 8 pulses per second; reduced pulse rate to minimize possible heat buildup in gold; starting on the occlusal surface, slowly painting back and forth over all surfaces; then to buccal surface, back and forth top to bottom; then to lingual, starting at the occlusal aspect, brushing across the lingual surfaces side to side, moving toward gingival. The crown popped off with a scaler (Figures 9 to 12).

Note the cement left on the abutment and inside the zirconia coping crown. The abutment was temporized with a compositecrown, and the patient returned at a later date for cementation of the replacement crown.

Case 3
Diagnosis and Treatment Planning—The patient presented with 10-year-old resin-bonded pressed all-ceramic crowns on teeth Nos. 8 and 9 (Figure 13). The porcelain had fractured on the facial aspect of the restoration on tooth No. 8.
Treatment would consist of removing the crown using an erbium laser, impressions, and then re-cementing the existing crowns as temporaries during the laboratory fabrication interval.
Clinical Protocol—The crowns were removed using the PowerLase Erbium R14 handpiece, 8/1.0 Cylindrical Quartz tip.

Laser Parameters:

• Wavelength = 2,940 nm
• Power = 2.0 Watts 135 mJ
• Repetition rate: 15 Hertz
• Pulse width: SSP 50 µsec
• Water 4/air 2 spray.

Only the erbium laser was used with the tip in contact with outer surfaces of the crowns; pulse repetition rate is a frequency of 15 pulses per second, starting on the facial at the gingival margin surface, slowly painting back and forth over all surfaces; then to lingual surface, back and forth, bottom to top. Porcelain fractured at the point of the existing fracture line on the facial aspect of tooth No. 8. The crowns were popped off using a scaler inserted at the gingival facial margin (Figures 14 and 15).

Figure 13. (Case 3) Preoperative photo.	Figure 14. Immediately after lasering crowns off.

Figure 15. The pressed leucite-reinforced porcelain crowns, immediately after removal with the laser.

The teeth were reprepared for leucite-reinforced porcelain crowns (IPS Empress Esthetic [Ivoclar Vivadent]). After impressions were taken, the old crowns were used as temporaries; the fragment of porcelain that had been lost in the procedure was repaired with a light-cured composite resin (after cementation). Final restorations were placed 2 weeks later.

CLOSING COMMENTS
An erbium laser can be used to remove porcelain and other all-ceramic restorations, including bilayered and monolithic zirconia restorations. This can be accomplished without damaging the restorations, underlying bonded composite buildups, abutments, or the tooth structure. This technique is specific for the erbium wavelengths, not diode, Nd:YAG or carbon dioxide lasers; and, of course, no laser can be used to remove metal or PFM restorations.
I have placed hundreds of all-ceramic restorations for my patients; many more than I have ever had, or will ever have, to remove. The good news is that we now have a tool to use in those infrequent and otherwise very challenging circumstances.

Dr. Cranska practices full-time laser and family dentistry in Severna Park, Md. He has advanced proficiency laser certification from the Academy of Laser Dentistry and standard proficiency and training certification from the Institute for Advanced Laser Dentistry. He can be reached at (410) 975-9331 or via e-mail at laserdentistry@hotmail.com.

Disclosure: Dr. Cranska has no financial interest in any laser company, but is compensated as a clinical consultant for presenting, lecturing, and training from the Institute for Advanced Laser Dentistry and Millennium Dental Technologies.