WHAT BONDING AGENTS ARE RECOMMENDED IN THIS HANDBOOK?
On t his website I am recommending two generation V products, both total-etch, (also called etch and rinse adhesives), Photobond, a Kuraray product, and All Bond III, a Bisco Product.
The problems with Generation IV were inadequate primers and therefore post-op sensitivity was still occasionally possible.
In an unfortunate turn for the profession, rather than develop better primers, the manufacturers targeted dentinal etch as the problem, and subsequent generations – Gen VI and Gen VII all retained the smear layer and bonded through it, with lower acidity etchants, resulting in the practical deficiencies and reduced durability as detailed in the page Standard Bonding Protocol
DOUBLE PRIMING AS A METHOD TO ENSURE POST-OPERATIVE COMFORT
A universal primer can be added to any Generation IV or V bonding system to ensure that dentin is always well-primed. This assures post- op comfort, inactivates MMPs, and closes tubules to resin components and leachates.
The product chosen for this function is Microprime B, by Zest Dental Products. It is similar to products based on either chlorhexidine, glutaraldehyde, benzalkonium chloride, or, in this case, benzethonium chloride. These are all mild disinfectants, and protein fixatives. Universal primers were reviewed by Clinician’s Report in August 2002 They noted a lessened likelihood of tissue burns relative to glutaraldehyde formulations.
Gluteraldehyde formulations are the most widely used, but sloppy technique, for example, primer pooling under cotton rolls, will cause a soft tissue burn that is painful for 24 hours. Not a practice builder, my friends. Safety of materials is not absolute, we have tools which can hurt people when misapplied.
Microprime B is formulated as follows: 59% water, NaF 1%, HEMA 35%, and 5% Benzethonium chloride. It is available in the USA, but in Canada, due to low volume of sales, no supplier has taken out a device licence with Health Canada to import it. It is perfectly legal to use, however. Now it must be ordered direct from Shasta Dental Supply California, 1-800-554-6394.
Why is it a good choice? It is much less cytotoxic than glutaraldehyde products. There are other clinical uses,
- desensitization of exposed roots
- desensitization of crown preps after preparation.
The latter is a worthwhile benefit, because often no anesthesia is needed at a crown insertion appointment when the prep has so treated. This is much appreciated by dentist and patient alike, and proprioception of occlusion is better, leading to more exact occlusal harmony.
HOW TO APPLY MICROPRIME B:
Once etch and rinse are complete, dry the prep to the point that no visible standing water remains in the prep. Apply Microprime B with a Voco #1 foam pledglet and immediately air-blow off the tooth until a consistent low gloss finish is seen on the tooth surface and there are no visible droplets or standing moisture.
HOW TO APPLY ADHESIVE: STANDARD METHOD
The two-part adhesive is mixed with a standard Bendabrush (Centrix) and immediately applied to the tooth. If it does not reach the tooth within 15 seconds, the bonding agent is discarded, and a new mix started. Air thinning of the adhesive follows, volatilizing the alcohol and entrapped water, and then the adhesive is cured.
SPECIAL APPLICATION DEVICES FOR ALL COMPONENTS:
Application devices for this bonding system vary according to the size of the prep.
- #60 paper points are used in root canals being prepared for posting
- Bendabrushes (regular) in small restorations for etch, prime and bond rather than just the bond. When using brushes, differing colors of brushes are routinely used to prevent inadvertent re-use of an incorrect brush for a step.
- Larger restorations need a Voco #1 foam pellet to absorb copious amounts of etch or primer. These pellets are carried to the tooth in cotton pliers. This method fosters rapid deployment in large preps and introduces no “fluff” into the bonding scheme.
THE PRIMER:
Microprime B is applied with the Voco#1 pledglet and immediately blown free with triple syringe and HVE until a consistent low gloss finish is seen on the tooth surface and there are no visible droplets or standing moisture. The manufacturer recommends up to 20 seconds application time, but the author has 25 years of experience without primer duration.
COMPARING CLEARFIL PHOTOBOND TO BISCO ALL-BOND III
Both bonding agents are 5 to 7 microns in film thickness. Both are both alcohol-based. Both having primers in their formula. Both are a two-bottle mix just prior to insertion. Both have defensible proof of longevity. Both are mixed in a well and applied with a regular Bendabrush within 15 seconds of mixing, to preserve the ethanol fraction, so necessary for drying the bonding surface, and allowing the hydrophobic film to settle onto the tubules, initiated by the HEMA fraction of Microprime B and whatever proprietary primers are in their formula.
Both bonding agents follow the same preliminary etching/rinsing/drying/priming/ drying sequence, and both require the addition and mixing with a Bendabrush of Part A to Part B before application to the tooth.
The total time to apply a cured bonding film is approximately 35 seconds, one of the most rapid there is.
INDICATIONS FOR ALL-BOND III: MIXED SUBSTRATES
The choice of which bonding agent to use depends on the substrate being bonded to. When we have simply dentin and enamel, Photobond is my first choice, I believe MDP is the better monomer of the two. When there are mixed substrates in the application, then All-Bond III is the more expedient product. The manufacturer makes claims for effective bonding to these substrates without intervening primers. See Table 1 below.
For example, an expedient application would be restoring gingival repair to ceramo-metal restorations. Another application would be restoring endodontic access openings through PFG crowns., (See Class V). Adhesion to both the ceramic and metal portions, and the dentin, all in one mix is a clinical efficacy. . It is really possible to prime these substrates with specific primers in the 0.5mm.gingival margin of a ceramo-metal crown?
Another application is when bonding new composite to old composite. Without any corresponding evidence of effectiveness for Photobond, I am forced to resort to Bisco’s test results for this situation.
TABLE 1: ADHESION OF ALL-BOND III TO VARIOUS SUBSTRATES
TABLE 2: SYNOPSIS OF BONDING METHOD
| PRODUCT | APPLICATION TIME AND DEVICES | REMOVE/THIN | DRY | CRITERIA |
| 37% PHOSPHORIC
ACID ETCH |
10-15 SECONDS
VOCO #1 PELLET BENDABRUSH (REGULAR)(RED) #60 PAPER POINT |
DISTILLED WATER 412 MONOJECT SYRINGE
OR 3CC SYRINGE/27 GUAGE TIP
|
3-5 SECS RINSE | LIGHTLY FROSTY |
| PRIME | VOCO PELLET#1
OR BENDABRUSH (REGULAR) GREEN NO DURATION REQ’D |
5 SECONDS | 5 SECONDS | SLIGHTLY GLOSSY |
| BOND | 3 SEC MIX TWO COMPONENTS IN A WELL
APPLY BENDABRUSH (REGULAR YELLOW) |
3-5 SECS
AIR BLAST |
3-5 SECS
AIR BLAST |
NOFURTHUR FLOW, QUIVERS |
DEMONSTRATED EFFECTIVENESS
What proof is there of the effectiveness of these adhesives? As stated at the outset, manufacturers need not prove very much to the regulators. However, Bisco has undertaken 6- year thermocycling studies on All-Bond III. Their study shows 86% bond retention. Other components of their system, Hi-X or D/E resin, show lower results, and therefore are not advantageous.
Note that thermocycling in distilled water is only a crude approximation of clinical service. It is probably only indicative of aqueous lysis.
However, this same study shows competitive products retaining less than 20% of initial bond strength, some are so weak that sample disintegrated before they could be tested.
Other bonds fared well and showed good clinical performance in 2 and 5-year tests by The Dental Advisor, so there appears to be broad clinical correlation to Bisco’s test method.
It would benefit the profession greatly if an accelerated aging test ere developed that exposed bonding agents to a wide spectrum of challenges beyond thermocycling in 37-degree distilled water. If the excellent minds of the research community were applied to this issue, something could be developed. There appears to be a lack of will to do so. So, the manufacturers currently run the show, much to their marketing advantage and much to the detriment of the patient, practitioner, and profession.
What proof can I offer for Photobond? Its proof is clinical. I have 25 years of successful restorations behind me – no sensitivity, no lost restorations, no marginal stain. Study club members who I have taught over the same time frame have had the same outcome. It is not personal.
This can be challenged scientifically, but it cannot be denied.
Objectively, the monomer of Photobond is based on MDP. Its formulation is like Panavia F2.0 without the particulate of that product. F2.0 one of the least soluble resin cements with an unparalleled clinical record. In fact, with a 25-year track record. Panavia F2,0 and its predecessors in the powder/liquid mixing format are one of the unequivocal success stories of the adhesive era.
ARE THERE NEWER MDP BONDING SYSTEMS THAT CAN BE RECOMMENDED?
There are many new Generation VII adhesives utilizing MDP. Sadly, none have effective dual-cure capacity. They claim so, but independent testing by Reality Research does not corroborate this. Don’t want to believe this? Subscribe and read for yourself. Some products demonstrate dentin bond strengths in the realm of 8MPa, far short of clinically adequate, which has been determined as 17MPa.
So, we wait in the wings until they get their act together, and slowly fume that we dentists are not informed, and the public is duly deprived of objective proof of success. Unfortunately, nobody can do any better than this in the current state of evolution of our profession.