by Gordon J. Christensen, DDS, MSD, PhD
In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics readers. If you would like to submit a question to Dr. Christensen, please send an email to firstname.lastname@example.org.
I have been using ceramic inlays and onlays for a few years - as promoted by several well-known dental lecturers - but I do not achieve the success that they claim. Some of my patients have complained of postoperative tooth sensitivity and numerous restorations have fractured, requiring replacement. What am I doing wrong?
Answer from Dr. Christensen
I have heard many similar comments. The "aesthetic revolution" has produced many excellent procedures, but some of these are very technique-sensitive. Listed below are some of the aspects of the tooth-colored inlay/onlay procedure that can cause problems:
•Tooth preparations should remove about 1 to 2 mm of tooth structure to allow optimum thickness of fired ceramic or cast ceramic. In my experience, tooth preparations that remove too much or too little tooth structure can cause the restorations to fracture during service.
•Avoid bevels on tooth preparations, except on facial surfaces of onlays. These bevels should be out of occlusion. Bevels placed by ceramic are especially prone to fracture during service.
•Lack of liner on the dentin. Although some bonding agents may be used alone - before the resin cement - without causing significant postoperative tooth sensitivity, it is often difficult to predict. I suggest placing a layer of resin-reinforced glass ionomer (3Mtrademark ESPEtrademark Vitrebondtrademark) on the deepest internal dentin areas of the tooth preparation, before the final impression. If placed correctly, these products can eliminate postoperative tooth sensitivity completely.
•Self-etching primers will reduce or eliminate postoperative tooth sensitivity when using resin cement. I suggest Panavia F resin cement and ED self-etching primer (Kuraray America). Many other self-etching primers are now available. The self-etching primer used underneath an indirect restoration must be self-curing or dual-curing. I have found that it is foolish to cure the primer and bonding material before seating a well-fitted ceramic restoration, because the film thickness of the pooled, cured bonding agent precludes adequate seating of the restoration.
•Case selection. Avoid using all-ceramic restorations on patients who have heavy occlusion, bruxing, or clenching. If you do elect to use all-ceramic restorations in such breakage-prone people, make a hard resin occlusal splint for them to wear at night and during other times of stress.
Practical Clinical Courses has a step-by-step video featuring tooth-colored inlays and onlays - C-101B, "Predictable Ceramic Inlays & Onlays" - which shows the preferred technique in close-up, easy-to-understand views. For information, call (800) 223-6569, fax (801) 226-8637, or visit our Web site at www.pccdental.com.
I have been told that I must use resin cement to seat all-ceramic restorations. I resist, because some of my patients have had severe postoperative tooth sensitivity, even though I use the bonding agents and resin cements exactly as the manufacturers and lecturers suggest. Which cements and bonding agents do you recommend for all-ceramic crowns, inlays, and onlays?
Answer from Dr. Christensen
In the past, resin cement has been the recommended luting material for all-ceramic restorations because of its strength and color availability. Resin cement was acceptable when a veneer was cemented over a nonsensitive, all-enamel surface. However, now there are several strong all-ceramic restorations that can be cemented over dentin surfaces using other cements that are less pulpally threatening than resin.
Here are my suggestions:
•When cementing all-ceramic full crowns, such as Procera and Inceram (aluminous), resin-reinforced glass-ionomer cement can be used with success - RelyXtrademark Luting Cement (3Mtrademark ESPEtrademark), Fuji Plus (GC America), or others. Although the strength of resin-reinforced glass ionomer is less than resin cement, these ceramic restorations have adequate strength for use with the weaker cement. Also, Procera and Inceram (aluminous) have relatively opaque internal cores; the possibility of color change due to cement is minimal.
•Other types of fired or cast-ceramic restorations - such as inlays, onlays, or veneers - have very little inherent strength. They usually require the extra strength and bonding capability of resin cement. In spite of the clinical challenges, I suggest resin cement for almost all other all-ceramic crowns, inlays, onlays, and veneers.
•Inlays, onlays, and veneers provide different challenges. Often, the color of these restorations must be altered slightly by the color of the cement. Resin cements can be translucent or are made in a variety of colors. Therefore, they meet the needs of color-changing better than other types of cements.
•I suggest using self-etching primers (see the answer to the first question in this article) on dentin and enamel surfaces before using resin cement with inlays, onlays, and crowns.
•After many years of using several brands of "total-etch system" bonding agents and resin cement under these types of restorations, and talking to thousands of dentists who have done likewise, I find the "total-etch" concept too unpredictable for routine use under indirect tooth-colored inlays, onlays, and crowns by typical dentists in busy practices. I do not deny that "total-etch" products can be used with success, but keeping postoperative tooth sensitivity at bay predictably is a major challenge.
A recently made Practical Clinical Courses video - C-102A, "Cement - A Critical Choice (With Tips for Procera & Other All-Ceramic Crowns)" - has been very popular and useful. For more information, call (800) 223-6569, fax (801) 226-8637, or visit www.pccdental.com.
Dr. Christensen is a practicing prosthodontist in Provo, Utah. He is the founder and director of Practical Clinical Courses, an international continuing-education organization for dental professionals initiated in 1981. Dr. Christensen is a co-founder (with his wife, Rella) and senior consultant of Clinical Research Associates, which, since 1976, has conducted research in all areas of dentistry and publishes its findings to the dental profession in the well-known CRA Newsletter. He is an adjunct professor at Brigham Young University and the University of Utah. Dr. Christensen has educational videos and hands-on courses on the above topics available through Practical Clinical Courses. Call (800) 223-6569 or (801) 226-6569.
Dr. Christensen's views do not necessarily reflect the opinions of the editorial staff at Dental Economics.