Downloaded from jada.ada.org on June 29, 2014
Use of luting or bonding with lithium disilicate and zirconia crowns Gordon J. Christensen JADA 2014;145(4):383-386 10.14219/jada.2013.44 The following resources related to this article are available online at jada.ada.org (this information is current as of June 29, 2014): Updated information and services including high-resolution figures, can be found in the online version of this article at: http://jada.ada.org/content/145/4/383
This article cites 33 articles, 3 of which can be accessed free: http://jada.ada.org/content/145/4/383/#BIBL Information about obtaining reprints of this article or about permission to reproduce this article in whole or in part can be found at: http://www.ada.org/990.aspx
Copyright © 2014 American Dental Association. All rights reserved. Reproduction or republication strictly prohibited without prior written permission of the American Dental Association.
Downloaded from jada.ada.org on June 29, 2014
Use of luting or bonding with lithium disilicate and zirconia crowns Gordon J. Christensen, DDS, MSD, PhD
uring the past few years, new types of toothcolored crowns have been introduced and rapidly accepted by both practitioners and their patients. Lithium disilicate (IPS e.max, Ivoclar Vivadent, Amherst, N.Y.), zirconia-based, full zirconia and a few other types of restorations just becoming available have had a significant influence on the fixed prosthodontic marketplace. Laboratories report that some of these newer crowns and fixed prostheses are now used more than are porcelain-fused-to-metal (PFM) restorations.1 As with any new concept, device or material, a significant period is needed for practitioners to adapt to the new concept, observe the clinical challenges it presents and eventually have mature and reliable opinions about its clinical use. Among the challenges observed with lithium disilicate, zirconia-based and full zirconia restorations have been continuing questions about how to affix the restorations to tooth preparations and how to remove them after cementation when necessary. In this column, I discuss those specific challenges and provide state-
of-the-art suggestions concerning cementation and restoration removal. This is a controversial topic, and some readers will rebut the opinions I express here. lithium disilicate restorations
Cements, cementation and removal. Practitioners commonly ask me whether they should bond or lute lithium disilicate restorations. It has been my observation that bonding has been the most popular technique, probably because of ease of use, high strength, the ability to bond to tooth structure and the tooth-colored appearance of resins, which allows blending of the restoration’s color with the tooth’s color.2-5 Sandblasting of the internal aspect of lithium disilicate restorations is controversial because of the creation of microcracks shown in some studies, and some say the practice is contraindicated.6-8 When bonding lithium disilicate restorations, the clinician etches the internal surfaces of the restorations with 5 percent hydrofluoric acid for 20 seconds, silanates them once or twice and then bonds them to tooth surfaces with resin cement.9 This technique provides a strong connection between the restoration and the
tooth surface and yields an optimum esthetic result, because the bonded resin cement blends with the tooth’s color and the restoration’s color.2,3 If the preparation lacks retention—such as is the case with onlays, short full-crown preparations or severely tapered restorations—the decision to use bonding cements appears to be appropriate. However, if the tooth preparation has optimum retention, such as with adequately prepared full-crown or inlay preparations, is bonding the optimal technique, or should luting cement be used? In my opinion, bonding is not the best technique to ensure that tooth preparations have optimum mechanical retention, for the following reasons. Lithium disilicate has nearoptimum esthetic characteristics and can be made to match the color of teeth nearly perfectly.10 Similarly, resin cements can match tooth color very well. When one is removing a bonded lithium disilicate restoration that has been cemented with resin cement matching the tooth color, it can be nearly impossible to differentiate among the restorative material, the cement and the tooth structure.11,12 Research has shown that practitioners often inadvertently remove more tooth structure than desirable when removing bonded,
JADA 145(4) http://jada.ada.org April 2014 383 Copyright © 2014 American Dental Association. All Rights Reserved.
Downloaded from jada.ada.org on June 29, 2014
resin-cemented lithium disilicate restorations.13 Luting cements such as resinmodified glass ionomer cement, currently popular in the United States, or conventional glass ionomer cement allow easier removal of lithium disilicate restorations because of the following reasons. The luting cement is more opaque in color and is weaker than resin cement. During the removal of a restoration, the different color observed when cutting through the restoration makes a demarcation between the crown and the tooth and potentially allows for less traumatic crown removal than when a bonded restoration is removed. Resin-modified glass ionomer cement offers the benefit of fluoride release. Furthermore, this cement is well known to prevent postoperative tooth sensitivity, whereas bonding with resin cement occasionally causes unpredictable postoperative tooth sensitivity.14-16 When to bond and when to lute. Although long-term research on this topic is lacking, I suggest the following on the basis of current knowledge and my own use and observations of the products over the past few years. If the tooth preparation has adequate retention provided by acceptable length of axial walls and an optimum near-parallelism of axial walls, luting cements probably are indicated. If the tooth preparation has questionable retention, such as an onlay or a crown preparation with minimal retentive qualities, or if the restoration requires some color modification that can be provided by tooth-colored resin cement, bonding cements probably are indicated. Removal of a lithium disilicate restoration is extremely difficult and is one of the distinct disadvantages of this type of restoration.13 Both diamond and carbide burs and wheels have been promoted for this
procedure, but removal still is much more difficult than it is with PFM or full metal restorations. Later in this column, I will discuss a removal technique. zirconia-based and full zirconia restorations
Cements, cementation and removal. As with lithium disilicate restorations, the subject of cementation and removal of zirconia restorations has aroused controversy. Zirconia is about three times stronger than lithium disilicate.17,18 Zirconia-based restorations have an inner core of zirconia about 0.3 to 0.5 millimeters thick that is veneered with layered or pressed ceramic, whereas full zirconia restorations are composed entirely of zirconia. Research has shown that cementing zirconia restorations with resin-modified glass ionomer provides adequate retention.19 Either bonding with resin cement or luting with various conventional cements may be considered,20-22 and both techniques are being used by practitioners.23,24 Clinicians are aware that regardless of the cement type used, these restorations are extremely difficult to remove. Some alternative cementation procedures for full zirconia or zirconia-based restorations are as follows. The internal surfaces of the restoration are either sandblasted or cleaned with a commercially available product (Ivoclean, Ivoclar Vivadent).25-28 Either procedure appears to provide adequate cleaning of the restorations before cementation. Use of phosphoric acid to clean zirconia restorations before cementation has been criticized by some researchers; sandblasting appears to be less controversial.29,30 When to bond and when to lute. The decision regarding whether to bond or lute zirconia restorations is based on the same considerations
presented in the previous discussion concerning lithium disilicate. If the tooth preparation has adequate retention, luting may be preferable for reasons discussed previously. In my opinion, only when retention is questionable should bonding be the clinical choice for zirconia restorations because of the extreme difficulty encountered in removing the restorations when they have been bonded. Finishing and polishing lithium disilicate and zirconia
Another challenge with these materials is adjusting them during a clinical appointment. The finishing and polishing of both ceramics are extremely time consuming and difficult. The best way to overcome this problem is to avoid the necessity of disturbing the surface, thereby averting the need to finish and polish. Many dental laboratories are making these crowns slightly low (out of occlusion) to avoid the necessity for dentists to remove surface ceramic. This technique avoids cutting the restoration surface—but it can have somewhat serious complications, because it results in directing occlusal forces to adjacent teeth that may fracture owing to the additional loading. However, without justifying this technique, I will say that it is well known that usually the occlusion stabilizes gradually as the crowned tooth and the teeth in the opposing arch extrude. Ideally, new crowns should be placed with the same occlusal forces on them as adjacent and opposing teeth, but in reality this does not always happen. The following instruments have been shown in research to be among those that are best for finishing and polishing lithium disilicate and zirconia:31 dDialite for IPS e.max and Dialite
384 JADA 145(4) http://jada.ada.org April 2014 Copyright © 2014 American Dental Association. All Rights Reserved.
Downloaded from jada.ada.org on June 29, 2014
for zirconia (Brasseler USA, Savannah, Ga.); dLuster for IPS e.max and Luster for zirconia (Meisinger USA, Centennial, Colo.); dOptraFine (Ivoclar Vivadent). Use of finishing instruments should be followed by application of polishing pastes. Well-proven ones31 are dDiamante (Olivier Tric, Elmhurst, Ill.); dDiashine (VH Technologies, Lynnwood, Wash.); dOptraFine HP Polishing Paste (Ivoclar Vivadent); dZircon-Brite (Dental Ventures of America, Corona, Calif.). Wear of opposing teeth
In scanning electron research, the standard glazes and stains placed on both types of material wear against opposing teeth until the glaze is worn off.32 However, contrary to negative predictions made by some clinicians before the products’ introduction, neither material is wearing opposing teeth as much as did the previous generation of PFM or full ceramic crowns.32,33 It would be well if glaze did not have to be placed, but new methods of finishing and polishing lithium disilicate and zirconia are needed to eliminate this challenge. Conclusions
Cementation of lithium disilicate, zirconia-based and full zirconia restorations has been a controversial subject. Both bonding and luting cements have been suggested, and both are being used with clinical success. Because of the difficulty of removal of both types of crowns, luting the restorations with conventional cements appears to be a legitimate choice when the tooth preparation’s retention is adequate. However, bonding and use of resin cement are necessary when the tooth prepara-
tion’s retention is questionable or when color change effected by the resin cement is desired. n
Dr. Christensen is the director, Practical Clinical Courses, and a cofounder and the chief executive officer, CR Foundation, Provo, Utah. He also is an adjunct professor, University of Utah, Salt Lake City. He is a diplomate of the American Board of Prosthodontics. Address correspondence to Dr. Christensen at CR Foundation, 3707 N. Canyon Road, Suite 3D, Provo, Utah 84604. The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the American Dental Association. 1. Christensen GJ. Is the rush to all-ceramic crowns justified? JADA 2014;145(2):192-194. 2. Al Ben Ali A, Kang K, Finkelman MD, Zandparsa R, Hirayama H. The effect of variations in translucency and background on color differences in CAD/CAM lithium disilicate glass ceramics (published online ahead of print July 26, 2013). J Prosthodont. doi:10.1111/ jopr.12080. 3. Yuan K, Wang F, Gao J, et al. Effect of zircon-based tricolor pigments on the color, microstructure, flexural strength and translucency of a novel dental lithium disilicate glassceramic (published online ahead of print July 13, 2013). J Biomed Mater Res B Appl Biomater. doi:10.1002/jbm.b.32986. 4. Johansson C, Kmet G, Rivera J, Larsson C, Vult Von Steyern P. Fracture strength of monolithic all-ceramic crowns made of high translucent yttrium oxide-stabilized zirconium dioxide compared to porcelain-veneered crowns and lithium disilicate crowns (published online ahead of print July 18, 2013). Acta Odontol Scand 2014;72(2):145-153. 5. Hopp CD, Land MF. Considerations for ceramic inlays in posterior teeth: a review. Clin Cosmet Investig Dent 2013;5:21-32. 6. Colares RC, Neri JR, Souza AM, Pontes KM, Mendonça JS, Santiago SL. Effect of surface pretreatments on the microtensile bond strength of lithium-disilicate ceramic repaired with composite resin. Braz Dent J 2013;24(4): 349-352. 7. Yavuz T, Dilber E, Kara HB, Tuncdemir AR, Ozturk AN. Effects of different surface treatments on shear bond strength in two different ceramic systems. Lasers Med Sci 2013; 28(5):1233-1239. 8. Dilber E, Yavuz T, Kara HB, Ozturk AN. Comparison of the effects of surface treatments on roughness of two ceramic systems. Photomed Laser Surg 2012;30(6):308-314. 9. Guarda GB, Correr AB, Gonçalves LS, et al. Effects of surface treatments, thermocycling, and cyclic loading on the bond strength of a resin cement bonded to a lithium disilicate glass ceramic. Oper Dent 2013;38(2):208-217. 10. Niu E, Agustin M, Douglas RD. Color match of machinable lithium disilicate ceramics: effects of foundation restoration. J Prosthet Dent 2013;110(6):501-509.
11. Chaiyabutr Y, Kois JC, Lebeau D, Nunokawa G. Effect of abutment tooth color, cement color, and ceramic thickness on the resulting optical color of a CAD/CAM glass-ceramic lithium disilicate-reinforced crown. J Prosthet Dent 2011;105(2):83-90. 12. Niu E, Agustin M, Douglas RD. Color match of machinable lithium disilicate ceramics: effects of cement color and thickness (published online ahead of print Nov. 8, 2013). J Prosthet Dent 2014;111(1):42-50. doi:10.1016/ j.prosdent.2013.09.005. 13. CR Foundation. Endo access through ceramics: are cracks a problem? Gordon J. Christensen Clinicians Rep 2012;5(10):1, 3. 14. Blatz MB, Mante FK, Saleh N, Atlas AM, Mannan S, Ozer F. Postoperative tooth sensitivity with a new self-adhesive resin cement: a randomized clinical trial. Clin Oral Investig 2013; 17(3):793-798. 15. Chandrasekhar V. Post cementation sensitivity evaluation of glass ionomer, zinc phosphate and resin modified glass ionomer luting cements under Class II inlays: an in vivo comparative study. J Conserv Dent 2010;13(1): 23-27. 16. Sidhu SK. Clinical evaluations of resinmodified glass-ionomer restorations. Dent Mater 2010;26(1):7-12. 17. Guazzato M, Albakry M, Ringer SP, Swain MV. Strength, fracture toughness and microstructure of a selection of all-ceramic materials, part I: pressable and alumina glass-infiltrated ceramics. Dent Mater 2004;20(4):441-448. 18. Guazzato M, Albakry M, Ringer SP, Swain MV. Strength, fracture toughness and microstructure of a selection of all-ceramic materials, part II: zirconia-based dental ceramics. Dent Mater 2004;20(4):449-456. 19. Christensen RP, Ploeger BJ. A clinical comparison of zirconia, metal and alumina fixed-prosthesis frameworks veneered with layered or pressed ceramic: a three-year report. JADA 2010;141(11):1317-1329. 20. Abdelaziz KM, Al-Qahtani NM, AlShehri AS, Abdelmoneam AM. Bonding quality of contemporary dental cements to sandblasted esthetic crown copings. J Investig Clin Dent 2012;3(2):142-147. 21. Meng XF, Xie ZG, Chen YH, Gu N. Effects of sandblasting on surface character and resin bond of zirconia ceramic [in Chinese]. Zhonghua Kou Qiang Yi Xue Za Zhi 2011;46(6): 370-374. 22. Peutzfeldt A, Sahafi A, Flury S. Bonding of restorative materials to dentin with various luting agents. Oper Dent 2011;36(3):266-273. 23. Seto KB, McLaren EA, Caputo AA, White SN. Fatigue behavior of the resinous cement to zirconia bond. J Prosthodont 2013;22(7):523-528. 24. Azimian F, Klosa K, Kern M. Evaluation of a new universal primer for ceramics and alloys. J Adhes Dent 2012;14(3):275-282. 25. Gargari M, Gloria F, Napoli E, Pujia AM. Zirconia: cementation of prosthetic restorations (literature review). Oral Implantol (Rome) 2010;3(4):25-29. 26. Chintapalli RK, Mestra Rodriguez A, Garcia Marro F, Anglada M. Effect of sandblasting and residual stress on strength of zirconia for restorative dentistry applications. J Mech Behav Biomed Mater 2014;29:126-137. 27. Saker S, Ibrahim F, Ozcan M. Effect of
JADA 145(4) http://jada.ada.org April 2014 385 Copyright © 2014 American Dental Association. All Rights Reserved.
Downloaded from jada.ada.org on June 29, 2014
different surface treatments on adhesion of In-Ceram Zirconia to enamel and dentin substrates. J Adhes Dent 2013;15(4):369-376. 28. Bhargava S, Doi H, Kondo R, Aoki H, Hanawa T, Kasugai S. Effect of sandblasting on the mechanical properties of Y-TZP zirconia. Biomed Mater Eng 2012;22(6):383-398. 29. Quaas AC, Yang B, Kern M. Panavia F 2.0 bonding to contaminated zirconia ceramic
after different cleaning procedures. Dent Mater 2007;23(4):506-512. 30. Yang B, Wolfart S, Scharnberg M, Ludwig K, Adelung R, Kern M. Influence of contamination on zirconia ceramic bonding. J Dent Res 2007;86(8):749-753. 31. CR Foundation. Polishing instruments for new monolithic materials. Gordon J. Christensen Clinicians Rep 2013;6(2):1, 6.
32. CR Foundation. BruxZir and milled IPS e.maxCAD: very promising 1-year results. Gordon J. Christensen Clinicians Rep 2012;5(6): 1, 3-4. 33. Odatsu T, Jimbo R, Wennerberg A, Watanabe I, Sawase T. Effect of polishing and finishing procedures on the surface integrity of restorative ceramics. Am J Dent 2013;26(1):51-55.
386 JADA 145(4) http://jada.ada.org April 2014 Copyright © 2014 American Dental Association. All Rights Reserved.