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JCO Interviews Dr. Elliott Silverman, Dr. Morton Cohen, and Dr. A.J. Gwinnett on Bonding

VOLUME 13 : NUMBER 04 : PAGES (236-251) 1979

SIDNEY BRANDT, DDS, Interviews Editor

Dr. Elliott Silverman

Dr. Morton Cohen

Dr. A.J. Gwinnett

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JCO Can you estimate how much bonding is being done?

DR. GWINNETT In a recent survey of orthodontists, Gorelick (JCO, January 1979) found that only about 7% were not bonding at all. 93% were bonding in varying amounts.

DR. SILVERMAN I would add that perhaps 20% are bonding indirectly in some form. My whole practice is done indirectly. It is fast, clean, accurate, and automatic. I do direct bonding only when replacing the few brackets that are lost, or on newly erupted teeth.

JCO Do you keep a number count of failures?

DR. SILVERMAN Not any more. In the beginning it was perhaps 2%.

JCO How accurate is the placement of brackets indirectly?

DR. SILVERMAN More accurate than bonding directly, and more accurate than banding. How can you talk about 2º or 3º when you are cementing bands. One push of the band pusher too hard will place a band 2-3mm off. With indirect bonding, you can use measuring calipers and an angulator at the bench. That's a true method of putting brackets on whether it be Straight-Wire, Creekmore, or any other preangulated and pretorqued method. There are a lot of positives for indirect bonding. I can't think of any negatives, except the expense. But, you've got to pay for a good thing.

DR. COHEN You can make up the expense in accuracy and time. The time spent bonding directly is much more than for indirect. So, chair time is involved and that is expensive too.

JCO What is your timing now for a complete indirect strapup?

DR. SILVERMAN Twenty-five minutes, including cleanup. Both arches in twenty-five minutes.

JCO A quadrant at a time or an arch at a time?

DR. SILVERMAN One arch at a time. I could strap up twenty cases a day in my office with no trouble at all.

JCO How soon do you tie them in?

DR. SILVERMAN Immediately on nonextraction cases. On extraction cases, we have the teeth removed after the brackets are put on. Then they are tied in.

JCO How heavy a wire would you tie in over how long a range?

DR. SILVERMAN Right up to edgewise. It is not the heaviness of the wire. It is the labial pull. If a tooth is lingually locked, even a light wire creates a tremendous tensile force on the bracket, especially if we use ligature tying pliers. We could not do that earlier with the weaker adhesives. Now, with Auto-Tach and Solo-Tach, we do it as freely as if we had a band.

JCO John, which adhesives were used for your bonding testing?

DR. GWINNETT The study was done by my colleague, Leonard Gorelick. He and several clinical colleagues conducted a contralateral study of Concise (a heavily filled resin) and Endur (a lightly filled resin), using one resin on one side of the arch and the other on the opposite side.

JCO What was the conclusion?

DR. GWINNETT Both resins performed with comparable success, with some variations from site to site in the mouth and from clinician to clinician. It is interesting that the clinicians' success rate was not as high as they thought, with success rates in the 90% range when molars were included.

DR. SILVERMAN I don't consider 90% to be a good level. Our failure rate has been 2% or less and we have debonded hundreds of cases. We have debonded ten cases every week for the last two years.

JCO Is bonding success in the posterior region significantly less than in the anterior?

DR. GWINNETT Studies generally support this view. However, Zachrisson and Brobakken (1978) reported improved retention, particularly in the posterior quadrants, using antisialagogues such as probanthine and atropine to provide a dry field.

DR. SILVERMAN We do not use probanthine or banthine and we claim the same success rate in the posterior region. Moisture control while bonding is certainly harder in the posterior, and you are just not as good in the posterior part of the mouth, because it is harder to see and gain access. Another reason might be that you didn't etch as well. But, I think that the greatest reason is the contour of the bracket to the tooth. You are dealing with a flat surface in the incisor and you are almost sure to have about 90% to 100% contour to contour. In the posterior, the contour is so varied, that no one manufacturer can accommodate to that.

DR. COHEN That is where the indirect system is so beautiful. The lab approach creates adhesive backings to give you that 100% contour relationship on all teeth.

DR. SILVERMAN The best bonding is accomplished if the parts to be bonded are mirror images of each other. The smaller the amount of resin between the tooth and the bracket, the stronger the bond. The thicker the resin, the weaker the bond.

JCO How do you manage partially erupted teeth?

DR. SILVERMAN I have an occasional problem on lower molars in the mixed dentition, because they are young teeth and not fully erupted. It is rare for a bracket to come off an adult. I think it is due to the chemistry of the enamel.

DR. GWINNETT In the absence of traumatic factors, I believe the problem lies primarily with the mechanics of isolation and the amount of enamel available for bonding. In reference to your observation on the chemistry of enamel, young teeth frequently etch to a different degree than old teeth, since they often contain more soluble components such as carbonates. These are usually lost during exposure of the teeth to the oral environment, to be replaced by less soluble components such as fluoride and exogenous proteins. There is, therefore, a decrease in enamel solubility with age.

JCO Has it anything to do with the pellicle on the tooth surface?

DR. GWINNETT Miura and his coworkers (1973) showed a reduction in bond strength if a prophylaxis was not conducted to remove tooth integuments. Most, if not all the pellicular integument will be removed during prophylaxis and conditioning. I do not believe that any remnants of pellicle, even subsurface pellicle (Meckel, 1968) affect bond performance clinically.

DR. SILVERMAN I think with partly erupted teeth, part of the problem is that there is less tooth surface and you are getting occlusal interference, especially on lower molars. The maxillary molar cusp almost completely encompasses that surface. I try to bond smaller tubes to these teeth, but if it doesn't work -- if they are lost repeatedly -- I band them. These lower permanent molars in the mixed dentition are the only teeth I am banding in my practice on occasion.

JCO Is there a difference in bonding deciduous and permanent teeth?

DR. GWINNETT Early studies showed differences in pit and fissure sealant retention, with the primary dentition exhibiting slightly lower rates (Buonocore, 1970). The differences were thought to be due to the presence of prismless enamel, common in primary teeth. Prismless enamel, by definition, lacks enamel rods. Resin penetration into it is markedly less than into the prismatic counterpart (Gwinnett, 1973). One is tempted to speculate that lower bond strengths may exist for the lesser penetration, but this has yet to be demonstrated. The clinical significance of prismless enamel related to bonding is unknown. However, recent reports suggest comparable results for pit and fissure sealant retention in the primary and permanent dentition, when the etching time is extended for primary teeth (Gourley, 1974).

JCO Does the length and strength of etching, then, make a difference in bond strength?

DR. GWINNETT Laboratory studies, e.g. Soetopo, Beech and Hardwick (1978) have shown that bond strengths may vary according to the strength of the acid. Retief (1975) however observed no significant difference in tensile bond strength in acid concentrations up to 50%. He recorded a highly significant decrease with 60-85% concentrations.

There has been a clinical orthodontic study in which no differences were found in clinical bond performance whether one etches for one minute with 30% phosphoric acid or 30 seconds with a 65% phosphoric acid gel (Gorelick, 1977, 1978). Such findings are interesting, since 65% phosphoric acid produces less porosity in depth in enamel with a lesser volume and shallower penetration of resin. This is a clinically significant observation, since there are forces such as occlusal interference, which exceed those associated with tooth movement and which dictate that one must obtain bond strengths greater than those forces simply related to tooth movement. One must also understand that acid strength and time are not the sole influence, since some resins perform differently.

DR. COHEN You compared a gel conditioner with a liquid conditioner. On which teeth was the gel used? I found it very hard to get rid of the gel.

DR. GWINNETT I agree with you that the gel can be more difficult to remove. The thixotropic agent in the gel can penetrate the enamel and I have seen examples in which it has impaired resin penetration. While the agent is water soluble, copious and thorough washing is necessary for 20-30 seconds.

DR. COHEN There was a significant improvement in bonding to deciduous teeth when we doubled our conditioning time from one minute to two minutes. The two-minute etch probably removed the prismless layer to expose the prismatic enamel. This would insure deeper resin penetration and possibly improve clinical performance if all other factors remained equal.

DR. SILVERMAN When we have a bracket failure, or if we are not satisfied with a bracket position, we remove the bracket and repeat the bonding procedure. We find that a 15-second etch is satisfactory for that.

DR. GWINNETT Provided resin penetration occurred initially, the surface with which you deal at the time of bracket replacement is essentially primed with resin. A prophylaxis and re-etching for as little as fifteen seconds removes any surface contaminants, allowing for successful rebonding, as is your experience. If bulky resin remnants remain, it is usually necessary to reduce them with a stone before rebonding.

DR. COHEN In that instance, re-etching is used to clean. Water won't do it.

DR. GWINNETT Salivary and other proteins, together with other contaminants, rapidly adsorb on the enamel. Even in microscopic amounts, they influence the wetting characteristics of the surface, which are so important in bonding. Water is ineffective in removing most surface contaminants. The surface must be re-etched for 10-15 seconds.

JCO Does that statement apply to the surface of a sealant?

DR. GWINNETT It is of paramount importance to stress the need for dryness throughout the bonding procedure. It is important initially when you apply a primer or sealant, and equally so when you add composite resin to the primer. Water not only competes for bonding sites, but can also physically interfere with the establishment of bonds.

JCO On the re-etching procedure, if it is proteins that you are cleaning off, how does that happen using an inorganic acid?

DR. GWINNETT Some oral proteins are soluble in inorganic acid, while others become physically detached by dissolution of the inorganic components and flotation from the enamel.

JCO Is the smallest base the most desirable one as far as retention of the bracket is concerned?

DR. COHEN It wouldn't be wise to have a base smaller than the bracket, even if you-could do it. You would have a food trap problem. In addition, materials caught under the wings of the brackets would overhang enamel, and that is dangerous.

DR. SILVERMAN The new Micro-Loc brackets from GAC are quite successful. Very few of these brackets come off. The older brackets only had the periphery holding them on. With the new Micro-Loc brackets, the entire base is involved in the holding process. The small size means less occlusal interference and little or no gingival impingement. Some of the older brackets were so large that they actually touched the gingival margins. With the Micro-Loc brackets, there is a desirable self-cleansing area between the gingiva and the gingival border of the bracket.

DR. COHEN Their contour is important as well. This bracket base has a double curve, occlusogingival and mesiodistal, which conforms better to the labial or buccal surface.

JCO Aren't other manufacturers going to smaller bases?

DR. GWINNETT Yes! Such a move had been fostered, in part, by changes in the retention design of metal brackets. Formerly, resin overlap onto the flange or extrusion through perforations in the base provided retention. With the development of undercut and meshback forms, the mechanical locking with resin now lies beneath an orally smooth base.

Base contour is also important to keep the bracket assembly and bonding resin away from the soft tissues. Direct contact between resin and gingival tissues may promote inflammatory change. This may be compounded by the presence of plaque whose accumulation is encouraged by the presence of exposed resin filler particles (Gwinnett and Ceen, 1978). Base contour is also important for fit or adaptation to the enamel surface. The achievement of a thin, uniform layer of bonding resin ensures maximum retentive strength and minimizes the need to remove bulky remnants during debonding .

DR. SILVERMAN That's what I like about the Micro-Loc bracket.

DR. COHEN The free margin of the bracket backing should be a feather edge. Some are thick and, as you thin them down, you run into loss of contour. The assurance we get from the use of the total lingual surface of the backing of the bracket for bonding has allowed us to put double buccal tubes on molars with Solo-Tach. We are using facebows on them. I have eliminated bands in my practice. There may be other adhesives that permit the same thing, but Solo-Tach is the one we have found to work best for that application. The mesh backing design has helped in retention.

JCO What can we say about plastic brackets?

DR. SILVERMAN Mort and I were the first practitioners to develop commercially available plastic brackets. You remember the IPB brackets, manufactured by GAC in 1963. They were the first plastic brackets on the market. At that time, when I gave children a choice of metal or plastic, nine out of ten chose metal. They wanted to show off their braces! It was a status thing. Then came bonding of a white plastic bracket. You didn't see any metal at all, whereas with the IPB bracket you did. The children still said they wanted the metal. Not because they wanted to show off the metal, but because they didn't want to be different. Today, when I ask the same question, I have not had one person say they would rather have the metal. So, the choice has reversed, at least in my area.

JCO Most orthodontists seem to prefer metal brackets.

DR. SILVERMAN It bothers some orthodontists that they have to alter their technique to use plastic brackets. You can't torque with plastic brackets and an edgewise wire, unless you use auxiliaries.

DR. COHEN Before the effective primers came out, we had to overlap the backing to retain the plastic brackets. We needed a mechanical lock. However, the primer that Lee puts out, and now L.D. Caulk has a primer which is effective, eliminates that problem and, therefore, eliminates the thick edges around the plastic brackets. It makes for a neater bracket.

JCO The primer is placed on the under-surface of the backing of the plastic bracket?

DR. COHEN Yes. You paint a very minimal amount on the under-surface of the plastic bracket and let it dry.

JCO What does the primer do?

DR. GWINNETT It renders the bracket base chemically compatible with the bonding resin.

DR. COHEN If you get it on the bracket, it will soften that also. So, you have to be cautious in the use of the primer.

DR. SILVERMAN I wouldn't advise using plastic brackets except on the upper six anterior teeth. Since it is strictly for esthetics, there is no need to put them on upper bicuspids, and I see no

reason for plastic molar tubes.

DR. COHEN There are dimensional problems in using plastic brackets on posterior teeth. They are too wide buccolingually to allow proper positioning in relation to the molar tube and you don't get a good in-and-out relationship, unless you have a different slot depth. But, I agree that there is no point to the use of plastic brackets except on the upper six anterior teeth for esthetics.

DR. SILVERMAN I believe there is smoother tooth movement with plastic brackets. Metal moving through plastic seems to have less resistance than metal against metal. At least, that is my observation.

JCO Metal wires in metal slots have been shown to have a great deal of play. I can visualize an even greater problem with metal wires in plastic slots, especially as you approach finishing in certain techniques. At a time when you want less tolerance between wires and bracket, with plastic brackets are you likely to have more because the slot is wearing and/or distorting?

DR. SILVERMAN The wear is not that great that I have seen it affect the finish of a case. I have not seen teeth uneven occlusogingivally, which you might think would happen with slot wear. Nor have I seen rotations. They are improving plastic brackets. Now you can tie most plastic brackets with a ligature locker, which you couldn't do with the older plastic brackets.

JCO Do you use elastomers as ties?

DR. COHEN I use elastomers. The A1 Alastiks that Unitek makes are beautiful. The clear ones seem to yellow in most mouths and we are using the gray ones by GAC.

JCO They are strong enough to engage the wire?

DR. COHEN Yes. I use them even with a torquing auxiliary which displaces the main archwire labially. I find that tying a wire ligature too often can split a wing off the plastic bracket.

JCO What is the purpose in using a sealant?

DR. COHEN There are two. One is that some systems need it to improve the bond to the enamel. The other is to protect the free enamel.

JCO Which systems need the sealant to improve the bond?

DR. GWINNETT One can divide currently available products into two broad groups in this context. The first comprises resins, sometimes referred to as "wet film" composites, that do not require sealants, since they have sufficient free monomer for enamel penetration. Solo-Tach is an example of such a resin. There are others. One is tempted to speculate that physical properties are increased by eliminating the sealant. Recent studies (Faust et al., 1978) have shown that resins like Solo-Tach and Auto-Tach show high tensile and shear values even though no sealant was used. In such a case, the filler particles of the composite can pack closer to the enamel surface and enhance bulk strength. It is yet to be determined if the degree of packing and filler size enhances bond strength values.

The second group of composites (e.g. Concise, Endur, Bondmor) use a sealant to improve bond strength, provide protection and reduction of marginal percolation. There is also a group of unfilled resins based on methylmethacrylate (e.g. Bracket Bond) which perform quite creditably in the upper anterior region. In other regions, these resins do not compete well with the filled and lightly filled resins. Gorelick (1978) has suggested using two types of resin for bonding, unfilled for upper anteriors, permitting easier debonding, and lightly filled for the remainder of the dentition.

DR. SILVERMAN When we were using Nuva-Seal and Bracket Bond which require a sealant, we were popping off brackets ligating to a lingually placed upper incisor. Using Auto-Tach and Solo-Tach without a sealant, we no longer have that problem.

DR. COHEN You can't really be replacing the sealant every three months anyway.

DR. SILVERMAN If the sealant stays in the area under the wire, that may help. It is a question whether it helps enough to warrant putting a sealant on just for that much protection.

JCO Is the Water-Pik useful there?

DR. GWINNETT There is conjecture as to the effectiveness of such devices. It will remove soft, loosely attached deposits in sites inaccessible to other means.

JCO But, it is of some help to get rid of materia alba.

DR. GWINNETT Removing the gross, loosely attached deposits such as materia alba will moderate plaque activity by allowing better salivary access. The aim is to exclude substrates that encourage acid production in plaque. It is difficult for a patient to do any more than control plaque growth and activity. We have shown that even a thorough dental prophylaxis fails to remove all plaque organisms. A patient has specific plaque patterns which rapidly reestablish after prophylaxis (Gwinnett, Golub, and Kleinberg, 1978). Additional plaque patterns form in association with directly bonded brackets (Gwinnett and Ceen, 1978).

JCO What is the action of fluoride on plaque?

DR. GWINNETT It is known that fluoride not only reduces enamel solubility, but also moderates and/or interferes with plaque growth and activity. There is a therapeutic effect from daily fluoride rinses, even in optimally fluoridated areas.

JCO Patients rinse once a day?

DR. GWINNETT Yes, at least once a day. It can be done at night after brushing. It allows us to complement the benefit of sealants.

DR. SILVERMAN I have always maintained that the sealant adds an extra step and an added chance for the teeth to get wet. I know there are those who say that if you have nothing to lose, why not put on a sealant. Unless it can be proven worthwhile, I am going to continue without a sealant.

DR. COHEN I think that bracket design and the home care that John suggests are much more important.

DR. SILVERMAN Other important factors are good technique to make sure that you don't have voids or lumps of adhesive at the periphery, and the cleanup when you are done strapping up a case, to make sure that you go around with a scaler and get excess resin off, particularly from embrasures.

JCO Do you use disclosing solutions on patients with appliances to demonstrate plaque?

DR. SILVERMAN It is an excellent idea.

DR. GWINNETT It is a motivating component of prevention, because a patient can clearly identify problem areas.

JCO If you see plaque accumulating on a surface, will daily fluoride rinses help that?

DR. GWINNETT Daily fluoride rinses will help to control plaque. I must emphasize that it is adjunctive to other preventive procedures.

DR. COHEN I'd like to see a program for restoring enamel.

DR. GWINNETT A great deal of laboratory work (e.g. Silverstone, 1977) has been done concerning the remineralization of white spots. We need clinical studies.

JCO There was a suggestion that just the saliva would remineralize a decalcified area.

DR. GWINNETT Saliva is rich in calcium and phosphate and may be presumed to be an excellent calcifying medium. The question is one of access of these ions to the lesion, which is a subsurface phenomenon. Saliva also contains factors which moderate calcium phosphate deposition. It is by no means a simple process, and a great deal of research effort is being directed toward understanding salivary mechanisms such as its mineralizing potential.

JCO What about just polishing decalcification away?

DR. GWINNETT You cannot remove white spot lesions by polishing. White spots can involve the full thickness of the enamel and dentin without cavitation.

JCO What about the possibility of getting a plastic that has the same refractive index into the subsurface spaces?

DR. GWINNETT Work is presently being conducted along those very lines with encouraging results.

DR. COHEN Composites on the surface can improve the appearance.

DR. GWINNETT Yes, but they can add bulk to the surface and introduce unesthetic contour.

JCO Would you have to break the surface over the white spot in order to impregnate it?

DR. GWINNETT No. Enamel is a porous tissue and may be rendered more porous by etching. The resin must have a small enough molecule to permeate the tissue pores. Resin penetration into white spot lesions has been demonstrated by Davila and Buonocore (1975).

JCO What about the question of cracks in enamel? Zachrisson said that they found as many cracks preorthodontically and nonorthodontically as they did postorthodontically.

DR. GWINNETT It should be no surprise to the clinician that anterior teeth are frequently cracked. The cracks are usually confined to enamel. Endodontically treated teeth, especially, show a number of cracks. The significance of cracking in debonding is that overexuberance could lead to tooth fracture.

DR. COHEN A new instrument is being sold for debonding -- an automatic mallet.

DR. GWINNETT I am familiar with the instrument, but cannot comment objectively on its value.

JCO Has not the problem in bonding become more one of removing the bonded attachments when you are ready, rather than keeping them on until you are ready to remove them?

DR. GWINNETT Yes. We must generate bonds strong enough to resist forces of dislodgement.

DR. SILVERMAN The overkill is really needed for the forces on the teeth other than the moving forces -- biting forces, hard toothbrushing, facebow treatment, a blow to the teeth, biting into a bone. We have to have overkill. We are dealing with a very hazardous environment.

DR. GWINNETT Removal is a twofold procedure, one involving removal of the bracket and the other the removal of the resin. Such procedures can be time-consuming.

DR. COHEN I have had to grind the attachments off periodontally involved teeth in adults. It did take long, but it was still better than banding.

DR. GWINNETT Considerable cost, time and effort has been spent over the years in the research and development of materials that bond to enamel. Now we are faced, uniquely in orthodontics, with having to debond and remove them. Incorrectly, many have approached debonding in a manner similar to debanding. We, and others (e.g. Burapavong et al.), have looked critically at the tissue response to various debonding modalities. We divided these into rotary instrumentation, hand instrumentation, and ultrasonics. On the basis of laboratory and clinical investigations, a number of these modalities create considerable real or potential damage. The aim of debonding is to remove the bracket and resin, and to restore as nearly as possible the original anatomical and topographical features of the tooth. The emphasis on morphology is important, since there appears to be a clear relationship between it and staining and plaque development.

We recommend the following bonding procedure, based on our laboratory and clinical studies. Removal of the bracket can be accomplished with either a bracket removing plier or ligature cutter. Both should be sharp and engage the interface between the bracket and the resin mesiodistally. The bracket is then dislodged using a rotational, peel motion. Methods advocating grasping the bracket and twisting it will sometimes leave the base on the tooth, requiring a further step.

We found a relationship between the extent of damage caused by hand instruments and the type of resin. Heavily filled resins required greater removal force than lightly filled or unfilled resins. We concluded that hand instruments should only be used judiciously to remove small remnants, e.g. a scaler in the embrasure area.

Bulky resin remnants should be removed with rotary instrumentation. High speed, 12 or 16 fluted finishing burs, or slow speed and an air-cooled Dedico green, medium rubber wheel is recommended. A dry field with good lighting, preferably fiber optics, is important. Resin bulk should be reduced to a relatively thin layer, thus avoiding bur contact with the enamel and the production of facets and deep scratches. The layer is then removed with the Dedico rubber wheel. This wheel can be shaped to reach such sites as the embrasures. The surface appears clinically smooth, yet microscopic scratches dominate the surface. These scratches can be removed with a water slurry of flour of pumice, a most important final step.

JCO Some orthodontists are using sandpaper discs to remove the resin. Is that not effective?

DR. GWINNETT We evaluated sandpaper discs and found them to be slow by comparison with other modalities. They also produced faceting of the enamel. I do not favor discs, since they can be difficult to control.

DR. COHEN I found the same results with discs-- facets, etc.

JCO Which burs do you recommend?

DR. GWINNETT We have been satisfied with the results of FG 7901 and 7406 finishing burs.

DR. SILVERMAN You do need high speed. I tried the 7901 at low speed and it would not even cut the adhesive.

DR. GWINNETT The bur is designed for high speed use and it should be confined to the removal of resin bulk. Contrary to the claims about finishing burs, they will cut enamel. Pumice will not remove all the scratches produced on the enamel by these burs in a reasonable time.

JCO How serious is scratching and gouging of enamel over the long run? Does it affect the life of the tooth? Will it eventually smooth out anyway due to wear and attrition?

DR. GWINNETT There is a clear relationship between plaque accumulation, stain, and tooth surface defects. We must, therefore, take steps to avoid introducing surface defects such as grooves and scratches.

DR. SILVERMAN We've always had this hazard. I don't know of any case that I have done with bands in which, after removal of the bands, there wasn't at least some microscopic white spot, some decalcification, even though I was very fastidious in my banding procedures.

JCO Has there been a study comparing damage to teeth from debanding and from debonding?

DR. GWINNETT Not to my knowledge.

JCO Is the eye a good enough test for iatrogenic damage?

DR. GWINNETT While iatrogenic damage can be seen by eye, its limits of resolution means that tissue damage may go undetected.

JCO How significant is it to see it dry and not wet?

DR. GWINNETT A wet surface covers a multitude of sins, since water or saliva alters surface and subsurface optical properties to mask irregularities.

DR. SILVERMAN Another cause for decalcification that we haven't mentioned is the case of the bracket that stays on for two years. We etched well and thought we dried thoroughly, yet we can have islands or spots that didn't get dry. We can have a void at the border of the bracket where the bond interface between the resin and the enamel failed and capillary action draws saliva into it. Saliva penetrates under the bracket, but not enough to loosen it.

DR. GWINNETT When brackets are stressed by strong occlusal forces, a blow to the mouth or biting on a hard object, it is conceivable that cohesive failures may occur in the resin on the bracket. If failure occurs at the enamel/resin interface opening it up to the oral environment, then bacteria or their products may percolate through the interface, some of which may be cariogenic.

DR. SILVERMAN It is a tack, not a bond. I have seen decalcification under a bracket which is hard to understand, except in those terms. I have seen it on few occasions, but I have seen it.

DR. COHEN It is too much to expect perfection from adhesives, although they represent a vast improvement. It has its hazards, but they are reduced compared to banding.

DR. SILVERMAN A loose band frequently went undetected, but a loose bracket is off and self-cleansing. After eight years of bonding, I see very little decalcification. It used to be a major topic of concern among orthodontists when we banded. I don't see enough to concern me.

JCO If you can't see decalcification by eye, is there nevertheless decalcification around a bond and is it of any significance?

DR. GWINNETT I have seen decalcification associated with bonded brackets which was not recognizable clinically. The lesions may appear as a narrow line or U-shaped with the base toward the gingival margin. My colleague, Richard Ceen, and I found preferential plaque accumulation at the boundary between the bracket and the resin extending cervically and into the embrasures. Even though sealants are applied with a view to protect enamel, they abrade away providing little protection to the enamel. I believe the subject warrants immediate investigation since our observations show that only microscopically thin films of polymerized sealant remain on enamel immediately following its clinical placement during orthodontic bonding (Ceen and Gwinnett, 1978).

We have little clinical evidence to support the complete reversal of extensive white spot lesions by remineralization. While I do not think that a white spot lesion which is accessible to oral hygiene procedures and saliva will progress, it will remain an esthetic problem.

DR. SILVERMAN Isn't it true that bands did the same thing?

DR. GWINNETT Yes. We should temper our criticism of bonding in this context, since white spots are quite common, much more prominent, and usually more extensive in the presence of bands.

DR. COHEN We have been bonding in my office for eight years. We have patients returning, let's say for wisdom tooth evaluation, who were bonded earlier. I don't see decalcification of any noticeable degree or caries on the teeth that were bonded.

JCO What should the practicing orthodontist do to minimize decalcification for his patients?

DR. GWINNETT In addition to following ideal bonding procedures closely, the clinician should control the factors that contribute to plaque formation and growth. These include eliminating or minimizing food and bacterial stagnation by using contoured brackets, removing excess bonding resin, and finishing resin margins to a feather edge.

Sealants will provide protection, at least for a period, but they are merely adjunctive to other preventive procedures such as a good oral hygiene regimen, dietary counseling, and daily fluoride rinses. One must motivate as well as educate the patient to accomplish the home care components of prevention.

JCO Since you brought up sealants again, maybe we ought to have a final word on the efficacy of sealants with respect to decalcification.

DR. GWINNETT Our current observations indicate that white spots occur with or without sealant having been applied. Zachrisson (1977) observed, in a limited sample, a reduction in the

incidence of white spots when sealant was applied. More studies are indicated, and we are presently working in this area. It is our experience that some sealants are lost within a short period due to abrasion and may be removed totally, before treatment completion, at sites where their benefit is most needed.

JCO Let's summarize your opinions on the usefulness of the various adhesive materials that are available to the clinical orthodontist today.

DR. COHEN There are the unfilled resins, the lightly filled resins, and the heavily filled resins. Even though the heavily filled resins are not as readily removed and require more chair time to obtain a smooth enamel surface after debonding, I prefer them for greater bond strength.

DR. SILVERMAN I can only tell you what has held up in my office. Concise, Solo-Tach, and Auto-Tach are probably in a class by themselves.

JCO These are heavily filled resins?

DR. SILVERMAN Yes, heavily filled. They would be the only type I would want to use, because I can't afford the time to replace lost brackets on a busy afternoon; and it is bad public relations for my patients to come many miles for such repairs.

JCO Are the ones you mentioned the only heavily filled resins on the market?

DR. SILVERMAN No, there are several heavily filled resins available commercially, though the recent trend has been toward lightly filled composites.

JCO How is an orthodontist to make up his mind about bonding today, when he is faced with so many different resins and brackets?

DR. GWINNETT There is understandable confusion. There has been a tremendously rapid evolution, some say revolution, of bracket design, materials, and techniques. Those who recognized the physiologic advantages and the great simplicity of attaching brackets directly or indirectly to teeth were limited initially, primarily by a narrow selection of materials and brackets. Through worldwide research efforts in the laboratory, clinic, and private office, we now see bonding as clinically effective and often a superior alternative to conventional banding. We are surely past the stage of cautious optimism and into the realm of everyday application. Study clubs, meetings, and continuing education programs provide an excellent forum for demonstration and debate of the indications and contraindications for these new bonding techniques.

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