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J Am Dent Assoc, Vol 132, No 7, 1041-1043.
© 2001 American Dental Association |
OBSERVATIONS |
Recently, I reviewed the research abstracts of both the American Association for Dental Research, or AADR, and the International Association for Dental Research, or IADR (available in the January and March 2001 issues of Journal of Dental Research). I was amazed to see how many of these abstracts dealt with research on self-etching primers, including the differences between self-etching primers and conventional "total-etch" bonding agents. I am pleased to see the increased interest in techniques that provide predictable desensitization of teeth receiving both direct and indirect restorations.
Dentists have been bonding resin-based composite and amalgam for many years. However, it is unfortunate that reports of the success of commercially available dentin-bonding agents have focused mainly on the criterion of the strength of the bond to dentin and enamel, not on the level of dentin desensitization.
If the dental literature is observed carefully, the reviewer will find that any brand of dentin-bonding material can be found to have the highest degree of bonding to dentin when compared with all other materials. The research results often relate to the evaluating organization, or to the person or company paying for the research. This confounding and confusing array of contradictory reports has been a significant problem in the area of dentin bonding. As a result, most conscientious practitioners have rejected the formal published peer-reviewed literature and company reports and have depended on empirical evidence reported by practicing peers.
In this article, I review the four categories of dentin-bonding agents available, and I make conclusions about the most effective methods not only to bond restorations to dentin, but also to desensitize that dentin in the process.
Three-component material.
The first concept to be popularized uses three constituents. The first liquid, usually phosphoric acid, removes the smear layer from dentin and etches the enamel. The second component—containing hydroxyethylmethacrylate, or HEMA, wetting agent and other ingredients—penetrates the open dentinal canals. The third component usually is unfilled bonding resin, which flows into the open dentinal canals. Correct use of this category of bonding agents forms a hybrid layer of resin-impregnated dentin, forming a seal between the resin-based composite and the open dentinal canals and providing a bond to the dentin.
The main problem with this category of bonding materials has been unpredictable postoperative tooth sensitivity, as reported by both dentists and patients. This sensitivity probably is related to lack of sealing of the dentinal canals, because of the very volatile alcohol- or acetone-containing bonding liquids.
If the three-component bonding agents are used meticulously, and if they are placed in adequate thickness, they provide adequate dentin desensitization. If they are not used correctly, the result is uncomfortable tooth sensitivity. The postoperative sensitivity horror stories I hear are upsetting, since the condition is avoidable. A patient recently seen in my practice typifies such problems. A young woman entered the practice complaining of tooth sensitivity. We analyzed her Class II resin-based composite restorations, which had been placed recently. They looked very good, both clinically and radiographically. Her problem was an inability to chew on either side of her mouth because of the extreme postoperative sensitivity in the restored teeth. On inquiring of the previous dentist about his bonding technique, we learned that the practitioner had used a three-component bonding agent exactly according to the manufacturer’s specifications. This case is an example of the unpredictability of the so-called "prime-etch" concept.
So what can be done when postoperative tooth sensitivity persists past several weeks? Removal of all of the restorations and replacement with more adequate bonding/sealing agents and new restorative resin are necessary.
Could these types of bonding agents be used with a more predictable technique? If a three-component bonding agent is used with a desensitizer (such as GLUMA Desensitizer [Heraeus Kulzer] or MicroPrime [Danville Engineering]) placed between the acid-etching step and the primer step, desensitization usually is effected. Alternatively, if a flowable resin is placed after the bonding step, desensitization is effected. Either of these solutions to the problem requires more steps. The increased number of steps makes this bonding category objectionable because of the technical complexity, and because of the additional expense and time required. Additionally, dentists cannot be certain that postoperative sensitivity will not arise.
Two-component material.
These so-called "one-bottle" bonding agents, which actually are one bottle of acid and one bottle of bonding material, have similar problems to those of the three-component category in prevention of postoperative tooth sensitivity. Their only apparent advantages over the other category are a simplified procedure and a reduction in the number of required steps.
Two-component agent.
The "self-etching" primer concept leaves the so-called "smear layer" in place, does not require washing off the tooth surface and seals the dentinal surfaces well. Numerous reports in the 2001 AADR and IADR abstracts support this concept as both providing very adequate bonding to dentin and enamel and ensuring postoperative comfort. This concept has been used in Asia for more than 10 years with very good results.
When the concept was introduced, some researchers and clinicians were suggesting that enamel surfaces should be selectively etched before the acid/primer was placed. This enamel-etching step was followed by placement of the self-etching primer in the entire tooth preparation. Current research reported in the AADR and IADR abstracts supports use of the self-etching primers alone without conventional acid etching of the enamel first.
According to thousands of dentists I have encountered on the international lecture circuit, the level of tooth desensitization effected by this category of dentin-bonding agents is highly impressive, with an almost 100 percent lack of postoperative tooth sensitivity. The most popular bonding agent in this category is Clearfil SE Bond (Kuraray). Clinical success with this category is so great that most dental companies that manufacture dentin-bonding agents are either introducing self-etching primers or developing them.
One-component agent.
In the second category of self-etching primers, all three constituents are placed on the tooth surface at one time and not washed off the tooth surface. The popular Prompt L-Pop (3M ESPE) has been received very well by practitioners, and it has captured an impressive portion of the market since its recent commercial introduction. Similar to the two-component agent, the one-component agent has been reported to have an excellent lack of postoperative sensitivity. However, before using these bonding products with other brands of restorative resins, practitioners should try the respective materials and bonding agents on extracted teeth to ensure that the materials bond to one another and to tooth structure.
THE TOTAL-ETCH CONCEPT
TOP
THE TOTAL-ETCH CONCEPT
THE SELF-ETCHING PRIMER CONCEPT
CONCLUSIONS
Two categories of bonding materials represent the total-etch concept. One involves three components: acid-etching liquid, primer and bonding agent. The other involves two components: acid-etching liquid and a combined solution of primer and bonding agent. Numerous reports support the two-component self-etching primer concept as both providing very adequate bonding to dentin and enamel and ensuring postoperative comfort.
THE SELF-ETCHING PRIMER CONCEPT
TOP
THE TOTAL-ETCH CONCEPT
THE SELF-ETCHING PRIMER CONCEPT
CONCLUSIONS
Two categories of bonding agents represent the self-etching primer concept. One category involves two components, a combined acid-etching/priming solution and a bonding agent. The other involves a single component, a combined acid-etching, priming and bonding material.
CONCLUSIONS
TOP
THE TOTAL-ETCH CONCEPT
THE SELF-ETCHING PRIMER CONCEPT
CONCLUSIONS
The "self-etching" primer concept has proved itself both scientifically and clinically. The concept reduces clinical steps, can be placed inexpensively, provides adequate bonding to dentin and enamel and, most importantly, ensures the patient’s postoperative comfort.
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FOOTNOTES |
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This article has been cited by other articles:
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  G. J. CHRISTENSEN Bonding to dentin and enamel: Where does it stand in 2005? J Am Dent Assoc, September 1, 2005; 136(9): 1299 - 1302. [Full Text] [PDF]
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 Z. C. Cuehrel[UNKNOWN], F. Tasman, M. A.[U. Onur, and A. Gumrukcuoglu Influence of a Self-Etching Primer on Compound Nerve Action Potentials J Biomater Appl, January 1, 2004; 18(3): 153 - 161. [Abstract] [PDF]
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G. J. CHRISTENSEN Ensuring retention for crowns and fixed prostheses J Am Dent Assoc, July 1, 2003; 134(7): 993 - 995. [Full Text] [PDF]
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S. DELIPERI and D. N. BARDWELL An alternative method to reduce polymerization shrinkage in direct posterior composite restorations J Am Dent Assoc, October 1, 2002; 133(10): 1387 - 1398. [Abstract] [Full Text] [PDF]
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