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Written by Glenn van As, BSc, DMD Friday, 14 September 2012 16:34
In a clinical article published in the February 2011 issue of Dentistry Today, entitled “New Technology: Mandatory, Elective, or Hype?”1 Drs. Gordon Christensen and Paul Child discussed many of the newer technologies that have come into the dental profession and their relative merits. When discussing dental lasers, it was stated1: “This technology resembles religion in its acceptance and lack of acceptance. Some practitioners have made lasers their main interest in the profession and support the concept strongly, while others call the entire concept ‘a technology looking for a use.’” While many procedures in dentistry can be accomplished with traditional methodologies, there are several instances where the use of a laser allows for the procedure to be quicker, easier, safer, or even just simply possible. The author has written several articles on the benefits of laser dentistry for the profession and how lasers as a technology have found their purpose in daily dental practice.2-4
Diode lasers have become popular in dentistry as soft-tissue handpieces.5-6 Their prevalence is a testament to their cost, portability, reliability, and ease of use.7 Diode wavelengths fall between 810 nm and 1,064 nm. These laser wavelengths are well absorbed in melanin, pigment, and hemoglobin. The capability to coagulate with laser light allows for venous lakes (hemangiomas) to be photocoagulated.8-9 The diode laser light penetrates into the venous lake and dehydrates the lesion with a success rate of 98.5% in a single session, which is safe, predictable, simple, and can be done with only topical anesthetic (Figures 1 to 4).10
The typical soft-tissue “handpiece” in dentistry has been the electrosurgery unit, due to its low cost.11 Although electrosurge units are able to remove large amounts of tissue quickly and there is no need for eye protection with them, there are several drawbacks with this technology.2 The diode laser, unlike electrosurgery units, can be used with pacemakers and used at times for small surgical soft-tissue alterations with only topical anesthetic. In addition, diode wavelengths, similar to all dental lasers, are antibacterial, and are safe to use around metallic restorations (amalgam, crowns, partial dentures), as well as orthodontic appliances and perhaps most importantly, dental implants. The use of monopolar electrosurgery units with dental implants can create catastrophic iatrogenic damage as can happen should they come into contact for mere seconds with any metals in the oral cavity.12-15 On the other hand, it has been shown that diode lasers can be used to safely remove tissue around dental implants16-17 without damage to the implant fixtures and abutments18-22 and when utilized judiciously with the right settings can be used without fear of heat buildup to the implants.23-24 Simple soft-tissue management to expose implant cover screws and during the final seating of implant-retained crowns are much easier when judicious use of a dental laser is utilized (Figures 5 to 9). These 2 procedures show how a soft-tissue diode can be used in instances that are not easy to treat with traditional methodologies used in dentistry.
Erbium Lasers (Er:YAG and Er:CrYSGG)
The erbium family of lasers resides between 2,780 nm (erbium, chromium:yttrium scandiumgallium-garnet [Er:CrYSGG]) and 2,940 nm (erbium:yttrium-aluminum-garnet [Er:YAG]), and their wavelengths are well absorbed in water and hydroxyapatite (Figure 10). Their absorption in these tissue compounds makes it possible to ablate hard-tissue compounds as well as soft tissue; basically anything with water in it. Enamel has 6% water, bone has 22% water, and soft tissue is composed of about 80% water. The mechanism of action is that the erbium laser wavelengths are absorbed in the water molecule and cause rapid expansion of these molecules. The rapid expansion causes microexplosions to occur, and this in turn provides for an ablation crater of 30 µm to 50 µm in hard tissue (Figure 11). The ability to ablate anything with H20 in the oral cavity has given rise to the moniker “all-tissue lasers” for the erbium family of lasers. The erbium lasers can ablate soft tissue readily, but with generally less hemostasis than the dedicated soft-tissue lasers like the diode wavelengths can provide.
One benefit of hard-tissue erbium lasers is their ability to be used to assist in “gummy smile” or smile-lift cases where an excessive or asymmetrical amount of soft tissue appears in a smile. Many times, clinicians focus on the “white” parts of the smile and fail to observe minor gingival asymmetries (pink part of the smile), which, if corrected, could significantly improve the overall aesthetic outcome of the case. Conventional open-flap osseous crown lengthening surgery consists of full- or partial-thickness flaps, and osseous surgery to remove bone, followed by sutures and a minimum of 12 to 16 weeks of healing. There is nothing wrong with viewing the overall architecture of the underlying biology of bone, roots, and soft tissue; however, there are times when more minimally invasive techniques may be used with equally impressive results and with perhaps a much quicker healing time. A soft-tissue diode laser can be used to remove small amounts of soft tissue in anterior recontouring cases.25-28 If the clinician will infringe upon the biologic width of the sulcus with the laser, then bone must also be removed. Osseous surgery, either in a full-flap scenario or at times with closed-flap laser techniques using both diode and erbium lasers, can provide tremendous results for the patient with shortened healing times.29-32
| Table. Clinical Reasons for Glass Ceramic Veneer or Crown Removal|
Dental veneers, very thin porcelain or all-ceramic facings, used to improve anterior aesthetics, have been available for almost 3 decades.33-34 These facings are placed on top of the tooth after it has undergone minimally invasive preparations, typically limited to enamel. Occasionally, there is a requirement for removal or replacement of these porcelain laminates for a variety of reasons (Table). At present, the most common method to remove the veneers is to use a high-speed handpiece with a diamond. Due to the nature of the tremendous color matching abilities of both resin bonding cements and the veneers themselves with underlying tooth structure, the removal of veneers without damage to the underlying natural tooth can be both difficult and time consuming. Erbium lasers can be used to safely and predictably debond porcelain (feldspathic or other glass-ceramic) veneers. Recently, research has begun to look at the erbium lasers as an alternative to traditional veneer removal techniques.35-38 Morford et al39 produced an excellent study in 2011 that was “designed to systematically investigate the efficacy of an Er:YAG laser on veneer debonding, possibly without damage to the underlying tooth, and preservation of the veneer integrity.” Morford et al39 used an Er:YAG wavelength at a low repetition rate of 10 Hz and a low-energy setting of 133 millijoules (mj) (1.33 W) with a short pulse duration of 100 µsec on 24 porcelain (lithium disilicate and leucite-reinforced glass ceramic) veneers (13 IPS e.max and 11 IPS Empress Esthetic [both Ivoclar Vivadent]) which were bonded to preparations on freshly extracted incisors. They measured the energy and time necessary for debonding the veneers as well as the percentage of transmission of the erbium laser through the 2 different types of porcelain.
|Figure 1. Preoperative appearance of venous lake (hemangioma) on lower lip of patient.||Figure 2. Immediate postoperative appearance of venous lake after photocoagulation and laser “puncture.”|
|Figure 3. Postoperative photo taken at one week, showing healing of lesion.||Figure 4. Two weeks postoperatively, showing complete healing of lesion.|
|Figure 5. Preoperative photo of |
zirconia implant abutment, after
maxillary left incisor crown
debonded 2 days earlier.
|Figure 6. Image shows the crown that was unable to be fully seated due to soft-tissue impedance.|
The results of their study39 found that the veneers transmitted between 11.5% and 43.7% of the incident Er:YAG energy with IPS e.max transmitting twice the energy as IPS Empress Esthetic at comparable thicknesses. All 24 veneers were were completely removed with these low settings with air-spray and the tip 3 to 6 mm away from the veneer. The time for complete porcelain veneer removal with the laser was on average just under 2 minutes (113 +/- 76 seconds). Underlying tooth structure was not damaged during the removal process because the energies used for debonding were up to 20 times less that needed to ablate enamel and dentin. The debonding mainly occurred at the cement/veneer interface possibly by interacting with the hydroxide molecule in the silane bond or by expansion of the water molecules in the porcelain. The authors did find that dry veneers took more time to debond than veneers stored in saline for 3 days. It is known that porcelain absorbs moisture with time. None of the IPS e.max lithium disilicate veneers fractured during debonding, while 36% of the IPS Empress Esthetic veneers did fracture. The authors postulated that this was possibly due to the known higher flexural strength of IPS e.max restorations, which might resist more easily the pressure buildup between the tooth and the veneer during the explosive ablation of the cement. The higher flexural strength of IPS e.max (lithium disilicate) veneers might explain why these veneers do not fracture during the removal process. Morford et al39 concluded that other porcelain systems and other veneer cements, other than RelyX (3M ESPE) veneer cement, should also be tested in the future.
|Figure 7. Diode laser, ready to remove soft tissue around a zirconia abutment.||Figure 8. Immediate soft tissue appearance after diode troughing was completed.|
|Figure 9. The crown was now able to be fully seated after diode troughing.||Figure 10. Absorption spectrum of the erbium (Er) and diode lasers shows the former is well absorbed in water and hydroxyapatite, and the latter is absorbed more in melanin and |
The author has removed many veneers during the last 5 years using an Er:YAG laser. The settings with removal of the veneers typically have been higher in energy than that used with the study (5 to 6 W versus 1.33 W), but water has been used to keep the pulpal temperatures lower than the air-only spray used in the Morford et al39 study. In addition, the typical time used for porcelain veneer removal or porcelain crown removal was around 45 to 60 seconds, after which mechanical removal (curette or crown remover) was used to complete the veneer removal. If the veneers are thin, then they will occasionally crack during removal but almost always, resin cement is left on the underlying tooth structure. In addition, when IPS e.max porcelain is used, the porcelain restorations almost always debond without fracture, and anterior crowns have been successfully removed. PFM crowns, zirconia crowns (such as Lava [3M ESPE]), or aluminum oxide crowns (such as Procera [Nobel Biocare]) have not been successfully removed with this technique. The author presents 3 cases below showing the technique and encourages readers to search for the links on these cases which will take readers online to video samples of the removal of these restorations. There are many reasons why veneers or all porcelain jacket crowns may need removal, and this technique can be a “life saver” for many situations, as can be seen in the Table.
A 35-year-old female patient came in with a chief complaint of stained and chipped veneers that were 15 years old. The patient wanted “longer” maxillary incisors and only wished for the three fouths crowns on the 4 maxillary incisors to be replaced.
Gingival closed flap osseous crown lengthening was undertaken on the facial aspects of the maxillary incisors, focusing on the areas between the line angles of the incisors. This procedure was carried out with the Er:YAG laser with settings of 30 Hz and 40 mj (1.2 W) with water and light air-spray for both the soft-tissue and osseous lengthening. Subsequently, the old all-ceramic restorations were removed with 30 to 45 seconds of Er:YAG laser energy (30 Hz and 175 mj, or 5.25 W, with water/air-spray with a VersaWave Er:YAG laser [HOYA Photonics] pulse duration of 300 µsec) directed at the entire facial and interproximal surfaces. (Note: Hoya is no longer providing laser equipment for use in dentistry. Alternative companies currently providing the technology as used here include: BIOLASE Technology iPlus, and the Technology4Medicine Lightwalker series.) These older ceramic restorations were removed mechanically with a sharp curette, and although fracture occurred with these veneers, they were removed completely, leaving the resin cement on the tooth. Full-coverage porcelain restorations (IPS Empress Esthetic) were then fabricated for the patient (Figures 12 to 15). The video of this procedure (and the following 2 cases) can be viewed at the address: http://tinyurl.com/cgrnf58.
A 45-year-old female patient came into the office with a fractured porcelain veneer on the lower left lateral incisor, and a recently debonded veneer that was reattached by the patient with a cyanoacrylate cement (Krazy Glue) on the lower left central. The patient wanted these veneers removed without iatrogenic damage to the underlying tooth structure.
|Figure 11. A 30 µm to 50 µm ablation crater made by a single pulse from an Er laser.||Figure 12. Preoperative smile, showing old veneers with poor width-to-length ratios (too small and square).|
|Figure 13. After Er:YAG crown lengthening and old veneer removal, showing cement on tooth structure.||Figure 14. Final postoperative healing of new veneers.|
|Figure 15. Postoperative healing photo at 4 weeks.||Figure 16. Preoperative photo of fractured lateral lower incisor veneer and central veneer that had been cemented with cyanoacrylate by the patient.|
These veneers were removed without fracture (settings 30 Hz and 175 mj = 5.25 W with air/water-spray with a VersaWave Er:YAG laser pulse duration of 300 µsec). Mechanical removal using a curette at the gingival margin in a “prying” fashion removed the veneers. The preparations were cleaned up and fine-tuned for all-ceramic crowns (IPS Empress Esthetic) (Figures 16 to 19).
A 40-year-old female patient came into the office wishing for a “smile makeover.” Her extensively restored anterior maxillary dentition from first premolar to first premolar had numerous failing discolored restorations. The patient had 8 lithium disilicate (IPS e.max) crowns placed on teeth Nos. 5 to 8 (Nos. 14 to 11 International) and teeth Nos. 9 to 12 (Nos. 21 to 24 International). Subsequent to the final restorations being placed, the patient developed irreversible pulpitis on the maxillary right lateral incisor.
The lithium disilicate crown was removed with the Er:YAG laser used for 2 minutes total time (60 seconds on the facial and lingual with settings of 30 Hz and 200 mj = 6 W with air/water-spray). The endodontic therapy was completed on the tooth. Subsequently, the remaining 3 incisor crowns were also removed using the Er:YAG laser with similar settings. The patient had noticed “brown spots” on the facials of these teeth, which turned out to be resin cement showing through. The patient’s restorations were replaced and the new lithium disilicate (IPS e.max) crowns were bonded into place (Figures 20 to 24).
|Figure 17. Immediately after Er:YAG removal of veneers.||Figure 18. Photo showing lateral incisor veneer in one piece after removal with laser.|
|Figure 19. Immediate postoperative appearance of new porcelain crowns.||Figure 20. Preoperative view of smile, prior to makeover.|
|Figure 21. Patient had irreversible pulpitis on right maxillary lateral incisor, and was unhappy with “spots” under final incisor crowns.||Figure 22. Endodontics completed on right lateral; laser removal of the lithium disilicate crowns completed, showing “brown spots” of uncured resin cement on tooth.|
|Figure 23. Four crowns were each removed in one piece and sent back to the dental laboratory.||Figure 24. Final smile.|
|Figure 25. Chart showing settings for the removal of glass ceramic (feldspathic, leucite-reinforced, and lithium disilicate) veneers.|
|Figure 26. Chart showing settings for the removal of glass ceramic (feldspathic, leucite-reinforced and lithium disilicate) crowns.|
The use of all-ceramic veneers and crowns has become routine for aesthetic cases in many practices. Unfortunately, these restorations sometimes require replacement due to caries or fracture, poor initial placement, or problems that the patients notice with respect to position, shape, or shade. The ability to use erbium lasers to quickly remove all-porcelain restorations (glass ceramics, such as leucite-reinforced porcelain or lithium disilicate) in an expeditious fashion, and without fear of creating iatrogenic damage to underlying tooth structure, holds great promise for the dentist, patient, and dental laboratory alike.
Further research is required to see if the lower settings without water promoted by Morford et al39, or the higher energies used by the author with water, provide for better results. However, there is no doubt that the promise of the erbium lasers for veneer removal is an exciting alternative to traditional methods presently employed. Laser veneer removal provides further credence of laser technology claiming a firm foothold in our profession, while providing another reason to support the notion that laser technology is an application that has found its purpose in the dental profession (Figures 25 and 26).
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Disclosure: Dr. van As is clinical director for AMD Diode Lasers but maintains no interest in any products mentioned in this article.
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