ROUND TABLE Bonding, Part 1

DR. BRANDT Let's begin with a discussion about brackets. Would each of you indicate your preference in the type of bracket for bonding including a description of pad size, type of backing, mesh, vs. perforation, etc.

DR. ZACHRISSON Routinely, I use .018" twin edgewise brackets on small pads with as much gingival clearance as possible. Over the years, my brackets have become increasingly smaller in size. For lower anteriors, cuspids, and bicuspids, I prefer to use pads on which the brackets are placed eccentrically, and the gingival parts of the pads follow the tissue contour (Fig. 1). I no longer use the perforated brackets. Our recent studies (AJO, July 1978) have shown mesh-basked brackets give increased bond strength as compared to perforated pads, and they are more hygienic. For lower second molars, I am quite satisfied with the design and fit of the new GAC photoetched brackets, but I do not have enough data for these pads on other teeth. I prefer to band all first molars, both upper and lower, providing them with triple and double tubes, respectively, and with various types of lingual attachments.

DR. GORELICK I like the small, mesh-backed, well-contoured pads, and low profile, offset, vertical-slotted edgewise brackets. Plastic brackets are used selectively only on maxillary anteriors. This accounts for about 10% usage. Our records, comparing region for region, reveal the mini brackets had as low a failure rate as the larger ones, whether bonded with Endur or Concise. This I believe is because the smaller pads permit a closer fit to the contours of the tooth surfaces. Smaller pads permit the brackets to be placed further from the gingivae, which could minimize the untoward effects of plaque.

DR. THOMAS Since bonding is not limited by the technique you practice, the type of bracket is not as important an issue as pad size or the type of base that is used in the bonding. My preference is to use the smallest pad size that will accommodate the bracket. The type of backing I prefer is the mesh/foil combination. Clinically, we see that the mesh/foil combination gives a stronger bond strength than does the perforated base. The mesh/foil base is a more esthetic appliance than the perforated base and a much easier base to use than the perforated base. You don't have to worry about the material getting up under the bracket wings on the foil/mesh base, and it is not necessary to build up the material on the outer surfaces of the foil/mesh. These are strong points for the foil/mesh base that apply in both direct and indirect techniques.

DR. MASUNAGA My preference is the edgewise siamese brackets on medium size mesh pads on maxillary anteriors and bicuspids. On lower anteriors, I prefer the small mesh pads with small brackets.

DR. BRANDT Is there a hygienic difference between mesh-backed and perforated brackets?

DR. GORELICK Gwinnett and Ceen, using ultraviolet light and scanning electron microscopy (Journal of Dental Research, Vol. 57, 1978) and Zachrisson (AJO, July 1978) reported mesh-backed brackets were more hygienic. My own clinical experience supports these findings.

DR. ZACHRISSON Our studies regarding plaque retention on different types of brackets on the same patient (AJO, July 1978) showed that brackets with perforated bases retained significantly more plaque. Thus the mesh-backed brackets generally gave a cleaner clinical impression and better gingival condition.

DR. MASUNAGA Mesh-backed units appear much neater. It is probably easier to keep themcleaner.

DR. THOMAS Yes, the mesh/foil combination is far more hygienic. The resin material that is required to be on the labial surfaces of the perforated bases tends to collect materia alba and plaque.

DR. BRANDT Describe your experiences with plastic brackets.

DR. GORELICK My experience with the first generation of twin-bracketed plastic brackets and an unfilled polymethylmethacrylate was very poor for the maxillary anteriors and a disaster for the other regions. At the AAO meeting in 1974 I reported, after 12 months of observation, a failure rate of 9% for the maxillary incisors, 24% for mandibular anteriors, 15% for upper bicuspids, and 34% for lower bicuspids. About half of the failures were in the bracket itself. My report in the May 1977 issue of AJO indicated a failure rate with perforated metal brackets of 4% for maxillary incisors, 6.5% for mandibular incisors, 6.2% for upper bicuspids, and 7% for lower bicuspids, over a 12-month period. The improvement was related to a stronger adhesive and a stronger bracket. It is interesting that the preference expressed by the panelists parallels those of the respondents to a national bonding survey I recently completed (which will be published soon in JCO).

The second generation, non-siamese, redesigned plastic brackets may be used clinically with a reasonable degree of success. I use them about 10% of the time, but only on maxillary anteriors. They are prescribed when a patient prefers them esthetically, even after we have explained their limitations, such as possible discoloration and a greater failure rate than with metal brackets.

DR. ZACHRISSON On at least three different occasions over the past years, filled with enthusiasm, I have started a number of patients using different types of plastic brackets, only to be disappointed each time. While I prefer to use steel brackets in the upper anterior region as a routine, plastic brackets may be indicated in the maxillary anterior region when no major correction of these teeth is required, particularly in adults and in treatment of short duration.

DR. THOMAS I have not had a lot of experience with plastic brackets. In my practice, the use of plastic brackets is limited to the maxillary incisors of adult patients who strongly oppose the showing of any metal in the anterior portion of the mouth. However, those plastic brackets that I have used have been successful with materials such as Orthomite II, Genie, and Bond-Eze that are methylmethacrylate bonding agents. They work quite well in the direct approach, and I have also found that better "adhesion" of the composite type materials could be obtained by using a surface activating material such as Lee Bond's ultraviolet system for plastic brackets. This worked well in the indirect system. But overall, plastic brackets have not been desirable in my hands as a matter of

routine.

DR. MASUNAGA Esthetic orthodontic appliances were the prime consideration when the clear polycarbonate brackets were originally designed. They tended to lose their translucent characteristics after being worn for prolonged periods of time and the earlier designs were unsatisfactory due to the frequent breakage of wings. I use plastic brackets for patients whose treatment time is relatively short, 6-10 months, and if severe rotational and torque forces are not required.

DR. BRANDT How do you see the future of plastic brackets?

DR. ZACHRISSON There are several alternative ways to go. Improvement of plastic brackets may take place through improved materials, design, and metal reinforcement; but also via completely different tooth-colored materials. This is an interesting area for future research with great clinical significance.

DR. THOMAS I can envision a bright future for the use of plastic brackets, if the manufacturers can present the profession with a hard plastic material that is not brittle, and that will accept good torque forces without damage to the brackets or rolling of the wire in the bracket slots. We need brackets with wings that are not so fragile. Presently, they will not accept repeated ties with ligature wire or even moderate biting forces. Much research is needed to find a material compatible with the oral tissues, easily bondable, and that can withstand the normal orthodontic forces and stresses of occlusion throughout a 24-month period without breakage.

DR. GORELICK My guess is that plastic brackets will continue to be used on a minimal and selective basis, as they are now, until a novel technical breakthrough occurs.

DR. MASUNAGA Plastic brackets will be accepted by many orthodontists, if an esthetically pleasing, strong and economical material can be developed. Given a choice, patients prefer plastic brackets.

DR. BRANDT Let us now explore some of your thoughts about the adhesives.There are quite a few bonding systems now available to orthodontists. Are they basically the samechemically?

DR. MASUNAGA Bonding systems are not the same chemically. Each has different formulations. There are two types, the acrylic and the diacrylic. Since I am quite familiar with the acrylic, permit me to discuss this one. A special chemical termed 2-hydroxy-3-B-naphthoxy propylmethacrylate is added to the acrylic. The naphthol rings have the specific function to keep the water moisture away from the adhesive. Thus, the adhesive does not become water-logged. The addition of a catalyst to the acrylic system causes a chemical reaction described as graftcopolymerization. The catalyst drives out the H molecule and allows the acrylic (MMA) to chemically attach to the protein molecules of the enamel. A scanning electron micro graph (Fig. 2) of the junction of the adhesive and the enamel shows that some of the acrylic tags seem to have become chemically fused to the enamel. Other areas show only a mechanical bond to the enamel. These chemicals alter the curing characteristics of the acrylic adhesives. Most acrylics tend to cure towards the center of the bulk, which would tend to cause it to peel away from the enamel surface.

DR. ZACHRISSON As discussed by Reynolds (Brit.J.Orthodont.2,1977) there are two important

basic types of dental resins currently in use for orthodontic bonding. Both are polymers classified as acrylic resins and diacrylic resins. The acrylic resins are based on self-curing acrylics and consist of methylmethacrylate monomer and ultra fine powder, whereas most diacrylic resins are based on an acrylic modified epoxy resin, generally referred to as bis-GMA or Bowen's resin. A basic difference is that resins of the first type form linear polymers only, whereas the second type molecule may be polymerized also by crosslinking into a three-dimensional network. This cross-linking contributes to greater strength, lower water absorption, and less polymerization shrinkage.

Both types of adhesive may occur in either filled or unfilled forms. A number of independent investigations indicate that the filled diacrylate resins of the bis-GMA type have the best physical properties and are the strongest bonding adhesives. Most composite resins (including Concise, Nuva-Tach, Auto-Tach, etc.) contain large, coarse quartz or silica glass particles of highly variable size with an average from 3 to 20 microns. These large filler particles impart abrasion resistance properties. Other composites (like Endur) contain submicron filler particles, which average only 0.2 to 0.3 microns in size, and consequently yield a smoother surface that retains less plaque and is prone to abrasion.

DR. GORELICK There are several ways to describe the various bonding systems. One clinically useful classification of bonding systems, related to their chemistry, is the unfilled polymethylmethacrylates versus the filled bis-GMA derived composites. My survey indicates a definite trend of practitioners changing from unfilled polymethylmethacrylates to the composites.

DR. BRANDT Some adhesives are stronger than others. Do specific ingredients add strength to the bond?

DR. GORELICK My records indicate that the filled bis-GMA derived composites are stronger clinically than unfilled adhesives. Laboratory tests for "strength", i.e., shear, tensile, compression, etc., vary. These kinds of tests show a considerable superiority of the composites over the unfilled polymethylmethacrylates. Basically, this is due to the presence of filler and cross-linkage of the bis-GMA derived composites. By the term "stronger", I mean that which helps reduce the frequency of bond failures. Comparing unfilled polymethylmethacrylate to the composite Concise, showed a much lower failure rate for the composite. Example: 23% vs 6.5% for lower anteriors; 25% vs 7% for lower bicuspids. In both instances, perforated metal brackets were used.

DR. ZACHRISSON It is likely that the cross-linking is one major reason why the diacrylates give stronger bonds than the acrylic resins. I am not quite sure of why some diacrylate resins seem to give stronger bonds than others, but it might, at least in part, have something to do with filler particle size and composition. Theoretically, differences may lie in the ability of a particular resin to wet and adapt to the etched enamel surface, in the inherent strength of the resin tags adapted to enamel and to the bracket pad, and in the strength of the bulk of adhesive. However, our findings indicate that the thickness of adhesive is perhaps more important than specific different ingredients. Thus, good adaptation of the bracket pad to the tooth surface and a thin layer of adhesive should be aimed at.

DR. THOMAS It is my understanding that in the new bis-GMA resins strength is added to the basic resin by the addition of fillers such as heat-treated glasses having a high content of silica, and

by the addition of silane adhesion promoter, which promotes a bonding between the filler particles and the resin matrix and, therefore, increases the strength of the overall resin mass.

DR. BRANDT Would you advise an orthodontist to research all the PSI (pounds per square inch) data of the various products available on the market, then select the one that tests highest, and use that one?

DR. THOMAS I do not feel that PSI data should be the criterion for selecting a bonding agent, because there are many other considerations that are more important. In my clinical experience, I have found that most of the materials designed and available for bonding offer adequate strength for the techniques that orthodontists use presently. One possible exception is a nonfilled methylmethacrylate.

DR. ZACHRISSON Although PSI data are important, they are only one of the factors to consider.

DR. GORELICK PSI data is only one factor to consider. Indeed, the choice of an adhesive, while important, is only one of the many factors involved in successful bonding. As an example, at the AAO meeting in April 1978 I presented the results of a clinical research paper in which five of us compared the composites Concise and Endur, each of us using the same kind of mesh-padded metal brackets (Ormco), working in his own office, on his own patients, in his own way. The results showed that operator differences were more important, on average, than differences between the two adhesives.

DR. MASUNAGA PSI data may give some indication about the relative strength of the material. I would not select the materials with the lowest PSI data. In my experience, most of the bonding adhesives with high PSI data work fairly well.

DR. BRANDT What should the criteria be for selecting a bonding system?

DR. THOMAS Basic criteria for selecting a bonding system would be the ease of handling the material, the stability, shelf life and moderate cost, along with high positive values for lack of microleakage, moisture absorption, thermal stability, etc.

DR. ZACHRISSON In addition to bond strength the most important criteria would relate to (1) working time, (2) setting time, (3) ability to withstand bracket drift once placed in correct position of the tooth, (4) ease of removal of excess adhesive flash, and (5) filler particle composition. For direct bonding, an adhesive should have a minimal setting time, which nevertheless allows adequate time for manipulation, and sufficient strength to withstand the placing of archwires immediately after the initial set. In my opinion, even the more satisfactory present commercial bonding systems may be considerably improved.

Using a new technique (Fig. 3) we are testing some experimental fast-setting adhesives, with working times of about 30 seconds, the brackets are bonded one-by-one. Bonding of etched and sealed teeth from second bicuspid to second bicuspid should then not require more than 5 minutes, and the archwires can be placed directly without any waiting period. This technique is particularly valuable for avoiding water contamination in difficult-to-reach teeth like the lower second molars, and to prevent accidental dislodgement of brackets after placement. Ideally, there should be no bracket drift, and stickiness of the adhesive should be good enough for safe and easy removal of excess around the pad. It should also be easy and feasible to place additional adhesive to deficiency areas, and this might require a possibility to dilute the adhesive. With regard to fillers, they must not

be so large as to cause unnecessary plaque retention.

It is likely that different adhesive properties are needed when bonding brackets and retainers. For example, good abrasion resistance is a prerequisite for a lingual retainer, but is not required, and may even be a disadvantage, for bracket bonding. In summary, I believe the material selected by the clinician should be dictated by its bond strength, handling properties, viscosity, cleanliness, cost, and, of course, general availability and storage life.

DR. GORELICK The safest route for the novice, and for those experiencing higher than currently reported failure rates, is to take several continuing education courses. The recommendations should then be tried in one's own practice environment.

DR. BRANDT Is it conceivable that an adhesive could be so strong that it would be virtually impossible to remove bonded brackets from teeth?

DR. THOMAS Yes. In fact, research is being done today on materials that unite chemically with the enamel structure. For restorative dentistry this is an advantage. For orthodontic purposes, since the bracket must be removed after treatment, this would be a disadvantage.

DR. BRANDT What are the disadvantages in having adhesives too strong?

DR. GORELICK In theory, if an adhesive is too strong, it will be too difficult to debond. In practice, this is true for the heavily filled composites, primarily in the upper incisors. Therefore, it may be more expedient to take advantage of the greater retentive strength of the mesh-backed brackets by using them with a more easily debonded adhesive, but only in the maxillary anteriors. In other regions a stronger adhesive is indicated.

DR. THOMAS Where it would be virtually impossible to remove bonded brackets from the teeth, removal would require either grinding or breaking brackets off and possibly damaging the enamel surface. This is one of the greatest disadvantages of having an adhesive too strong.

DR. ZACHRISSON The question of how strong is strong enough has not yet been settled, and it certainly varies in the different regions of the mouth. Also, some difficult ligations really demand an excellent bond. But the problems with a superstrong adhesive would lie in the creation of enamel ruptures and cracks when debonding. It might also be a little difficult to remove such adhesive properly without marring the enamel, although this would probably only mean that the removal would be unnecessarily time-consuming.

DR. MASUNAGA Direct bonding was designed to save time for the clinician. If the orthodontist has to spend considerable time and effort to debond and clean the enamel surface, it defeats one of the main features of direct bonding.

DR. BRANDT What chemical ingredient controls the bracket from sliding on the crown?

DR. MASUNAGA The various types of catalysts used by the manufacturers control the setting time. The faster the setting time, the less the bracket slides. A thick coating of sealant on the enamel surface will cause the brackets to drift. Excess sealant should be blown with an air syringe. A very thin layer of sealant will reduce bracket slide. The consistency of the bonding material can also minimize bracket slide. This is probably controlled by the size of the silica particles, as well as the

amount of silica mixed with the adhesive.

DR. ZACHRISSON I wish I knew, because then I could tell most manufacturers to add more of it to their adhesives! It may have to do with viscosity and filler particle composition. However,bracket drift is not only a matter of ingredients. Thus, we have experienced considerably less bracket slide when the adhesive layer is minimal, that is when brackets are pressed firmly towards the tooth surface when bonding and the bracket pad has a good adaptation.

DR. THOMAS The type of filler and the size of the particles certainly has a bearing on the tackiness of the composite.

DR. BRANDT Do you know any technique currently used in orthodontics that should not use bonded attachments because of the strength factor?

DR. THOMAS No, I do not.

DR. GORELICK My guess is that routine use of headgear and lip bumpers would result in a failure rate that would be inexpedient clinically.

DR. MASUNAGA I do not use cervical headgear against bonded maxillary molar tubes. In case of sudden bond failure, there is the potential danger of the inner bow stabbing the patient in the throat. Such a responsibility should be avoided.

DR. ZACHRISSON There are some orthodontic techniques that in my opinion are not optimal for bonding. However, that has nothing to do with the strength factor, but rather to the fact that I consider them to use too many and/or too complicated archwires, uprighting springs, coils, lingual attachments, etc. With the possible exception of headgear to the upper first molars, the filled diacrylate resins seem to be strong enough to be reliable for clinical purposes.

DR. BRANDT Which teeth do you bond routinely? How far back in the arches do you reach?

DR. MASUNAGA I routinely bond all the maxillary and mandibular anteriors and bicuspids. I prefer steel molar bands when cervical headgear is necessary, when extraction spaces need to be closed, when there is repeated failure of a direct-bonded tube, especially on the lower molars, and when there is an amalgam filling on the buccal surface, because bonding materials do not work on metals.

DR. GORELICK I bond from molar to molar in both maxilla and mandible, except where headgear and lip bumpers are used. Second molars are bonded selectively.

DR. THOMAS I routinely bond second bicuspids forward in extraction cases. In nonextraction, the bonds will include the molars. Second molars are included if they are present and their crown length is adequate for bonding.

DR. ZACHRISSON I routinely place bands on the upper and lower first molars, but bond all other teeth, including the lower second molars. The reason I no longer bond the first molars is mainly because of the lingual attachments available on bands (for elastics, palatal bars, lingual arches, etc.) and interproximal caries protection. On some partly erupted second bicuspids, it is difficult to place even an eccentric bracket in a proper position, and it may be easier to band such teeth also. Teeth in the lower posterior region are the most difficult ones to bond satisfactorily, because of moisture problems and interfering chewing forces. Still, with proper technique the lower second molars lend themselves well to bonding and our failure rate on such teeth is now quite satisfactory. These teeth are often difficult to band because of partial eruption. But the buccal surface is usually accessible

for bonding.

DR. BRANDT Do any of you use headgear and lip bumpers againstbonded buccal tubes?

DR. THOMAS In growth guidance cases, where headgear is indicated in nonextraction cases, I have successfully used Kloehn headgear against bonded tubes. I do not use lip bumpers, but see no reason why it should not be acceptable.

DR. ZACHRISSON I tried it with considerable success a few years ago. As mentioned, however, I now prefer to band all first molars.

DR. BRANDT Are there some adhesives that bond better in the buccal segments?

DR. THOMAS Yes, there are, primarily the bis-GMA type of resin. These resins require dry tooth enamel just the same as other bonding resins, but their stability in the oral fluids is much better than the acrylic resins, and of course their strength is more desirable.

DR. GORELICK I prefer composites rather than unfilled adhesives in all buccal segments. Using Concise, for example, the failure rate on mandibular bicuspids went from 25% to 7% for Concise, a significant improvement.

DR. MASUNAGA In my experience, some adhesives do seem to bond better in the buccal segments. I have noticed a smaller rate of failure in the posterior segments when diacrylate resins are used. Interlok, Dynabond, Concise and Solo-Tach have all given very satisfactory bonding strength in the posterior region.

DR. ZACHRISSON Again, I think the technique is more important than the physical properties of the adhesive. But our failure rates with different adhesives do indicate that some are stronger than others. For example, the diacrylate resins are no doubt stronger in the buccal segments than the acrylic resins. With the former, failures where the brackets have come off from the weld to the pad, are not uncommon (Fig. 4). There also appears to be a difference in bond strength between various diacrylate resins, but we have not yet been able to show this statistically.

DR. BRANDT Do you bond more boldly in adults than in young patients?

DR. ZACHRISSON No, I bond all teeth except the first molars in all my patients. Many times, it is easier to bond in adults, however, as they have increased height of clinical crowns and salivary flow is not so intense, both facts reducing the risk of moisture contamination.

DR. THOMAS Personally, I see no difference in the bonding on adults and younger patients. The deciduous teeth do offer a problem.

DR. GORELICK I bond as much as possible on both.

DR. MASUNAGA I use some plastic brackets on selected adults and teen-aged girls. These patients tend to take better care and appreciate the better appearance. However, steel brackets are bonded routinely on adults as well as on children.

DR. BRANDT Are deciduous teeth bonded often? How does your technique differ?

DR. GORELICK I frequently bond second deciduous molars in early mixed dentition treatment. The technique has two variations. First, since the shape of these teeth results in poor fitting brackets, the enamel surface is stoned slightly to make it flatter. This also removes some of the aprismatic enamel. The etch time is extended slightly. My records indicate the average failure rate for second deciduous molars-- using Concise with mesh-backed brackets-- is double that for

second bicuspids, using the same combination of adhesive and brackets. This subject needs further study.

DR. ZACHRISSON I do not bond deciduous teeth very often, and when I do it is usually the primary second molars. Except for the fact that there aren't any primary molar bracket pads, mytechnique differs only with regard to the conditioning. In primary teeth, because of areas of prismless enamel and presence of large amounts of exogenous organic material in the enamel surface, the acid treatment period must be doubled in order to produce etching patterns comparable to those found in permanent enamel (Silverstone, 1975). A more practical alternative, however, is mechanical removal of the superficial enamel by slight grinding with sandpaper discs. Then, the etching time can be reduced to levels used in permanent teeth.

DR. MASUNAGA Deciduous molar teeth are seldom bonded. However, when necessary, the buccal surfaces are flattened with a stone, so the bracket can be adapted closely.

DR. THOMAS As a matter of routine, I do not bond deciduous teeth. On those occasions where it was necessary, the etch was longer (2-3 minutes). Otherwise the technique was the same.

DR. BRANDT Are there periodontal complications specifically caused by bonding?

DR. THOMAS No periodontal complications of bonding need be experienced. However, with a poor technique, where the bonding material is allowed to encroach upon the gingivae or flash is left unremoved, periodontal involvement in the form of gingival irritation will be seen. This is more noticeable in the quartz or silica-filled resins such as Concise, Adaptik, Nuva, etc., than in the lightly filled resins as Endur and Dynabond. Complications may be seen where the base size is too large and allowed to encroach upon the gingivae. In cases of extremely short crowns, gingival irritation is not uncommon, like that seen in banded cases with short clinical crowns.

DR. GORELICK Given good oral hygiene and proper bonding techniques, periodontal complications should be negligible and reversible. Given improper home care and improper bonding techniques, the results may be severe and chronic. Poor technique will result in adhesive placed too close to or in contact with the gingivae. Unfortunately, there are times when the demands of treatment require such a risk in bond or band placement. It is essential that all excess flash be removed and the part of the adhesive that extends a bit beyond the bracket be feathered and not ledged.

DR. MASUNAGA In indirect bonding techniques, excess adhesive may be forced out and harden as "flash" beneath the periodontal tissues. This will cause severe irritation. All excess flash must be removed. In direct technique, if the bracket pad and bonding material irritate the gingivae, complications will follow. All excess material must be removed and, ideally, bracket pads should not rest on the gingival tissues.

DR. ZACHRISSON Our studies show that when bonding is performed correctly and excess adhesive flash is removed carefully, the gingival condition in bonded patients is improved as compared to banded patients. This is particularly true interdentally, since irritation in the "col" area is avoided. On the other hand, whenever the flash problems are neglected, and excess adhesive approaches the gingival margin, particularly with adhesives containing large, coarse filler particles, the gingiva around bonded attachments can be much worse than when steel bands are used.

DR. BRANDT Are some adhesives kinder than others to the surrounding tissues?

DR. GORELICK My clinical experience is that heavily filled composites seem to be more

plaque-attractive than unfilled adhesives and sealants. Lightly filled composites are someplace in between. However, I feel very strongly that the variable of oral hygiene and improper placement is more important than the material.

DR. ZACHRISSON Yes, bonding adhesives containing large, coarse filler particles have a rough surface that retains plaque more easily than those without or with small filler particles. Therefore, whenever working with the first type of adhesive, it is particularly important to remove excess adhesive on the gingival side of the bracket pad.

DR. THOMAS Yes. The non-filled or lightly filled resins will show less tissue irritation. However,if the material is allowed to be in contact with the gingivae where food and materia alba collect, gingival irritation will be seen in all the adhesives.

DR. MASUNAGA All adhesives have the potential of irritating the surrounding tissues, and somepatients might be allergic to the acrylic of the bonding agents.

DR. BRANDT What has happened to the caries index since bonding came upon the scene?

DR. MASUNAGA The steel bands tended to protect the interproximal areas, which the bonding systems do not. Other areas, such as the labial and gingival, are still susceptible to caries. Good oral hygiene is essential, no matter what methods are used by the orthodontists.

DR. GORELICK More research is needed to answer this question. Frankly, I am uncertain. My survey reveals that some orthodontists feel there is more interproximal caries, some think there is less. There is nothing conclusive.

DR. THOMAS I have seen no change in the incidence of caries in my patients. As in banded cases, those patients with poor oral hygiene will experience decalcification at the periphery of the attachments. But in those patients with good oral habits, no damage whatsoever is seen. Interproximal caries tends to be another issue. I see absolutely no difference in the incidence of caries interproximally. As an additional preventive measure, I apply a fluoride gel immediately after bonding and every six months, and instruct the patient in using nightly fluoride rinses.DR . ZACHRISSON Orthodontic bands protect completely covered tooth surfaces against caries, while making partly covered surfaces more susceptible to destruction. Also, the progression of the caries process is retarded under a well-fitting band. This is of value when small interproximal lesions and/or secondary caries are not detected or treated before the strapup is made. Both these interproximal caries protection mechanisms are lacking in bonded appliances. In other regions, there is usually slight spacing between the teeth during major parts of the treatment, and if regular fluoride supplementation (mouth rinses) is given, the interproximal caries situation in bonded patients is quite satisfactory. In treatments of long duration, however, it is important to check carefully for new interproximal lesions and secondary lesions.

DR. BRANDT Are you finding more caries in the bicuspid areas since fewer bands are cemented on these teeth?

DR. MASUNAGA I have not made any special observation of this problem.

DR. THOMAS Definitely no.

DR. ZACHRISSON Our caries studies in banded patients demonstrated very few new interproximal carious lesions in the usual predilection sites, and it was, in fact, questionable whether the typical cavities registered should be regarded as new lesions at all. When the interproximal caries protection of bands is lacking, preventive measures must be intensified. In so doing, the

number of new interproximal carious lesions on an overall basis is quite low. But I have had a few bonded patients who evidently were careless with the fluoride mouth rinses and oral hygiene, and where caries developed and progressed rather rapidly in the bicuspid areas. Whenever tooth contacts in the bicuspid areas are tight for long periods, I check regularly for interproximal caries using an explorer and bite-wing radiographs.

DR. BRANDT Some discussion on moisture control. Would you all agree that moisture control is one of the essential items that will determine success or failure in bonding?

DR. ZACHRISSON There is no doubt that moisture control is one of the key factors for successful bonding. For example, when part of the bracket pads were placed subgingivally on erupting teeth, failure rates were much higher than usual (AJO, February 1977).

DR. MASUNAGA Yes. It is an important factor in determining the success of a bond.

DR. GORELICK Yes, by all means.

DR. THOMAS Without a doubt.

DR. BRANDT Are the lip retractors presently on the market adequate? How can they be improved?

DR. GORELICK I prefer lip retractors with a tab to hold dri-angles in place effectively. The GAC and Caulk retractors have this feature. They permit placing the dri-angles or even a double dri-angle bent into the mucobuccal fold, to cover the opening of the parotid gland. In other retractors, without this tab, the dri-angles will often slip.

DR. ZACHRISSON Several new types of lip retractors represent great improvements fromprevious types. The breakthrough came with the McSpreader, which allowed easy access to all four quadrants of the mouth simultaneously. I still consider the McSpreader to be the best lip retractor.But this expander can be improved by extending the wings to better lift away the upper and lower lips in anterior regions, and by adding distal ends that hold the dri-angles in place.

DR. THOMAS The present lip retractors available are adequate. They could be improved by making them more comfortable and adjustable. The old GAC type lip expander is the one I still favor. If it had an extension on it to the buccal mucosa, as does the new GAC lip expander, we would have a less cumbersome and more satisfactory unit. The McSpreader works very well, but the wire in the front of the mouth gets in the way of the operator. The new GAC lip expander with the plastic piece behind the neck is uncomfortable and the mouthpieces are small, offering lip-roll onto the labial surfaces of the maxillary and mandibular anteriors. So, for all-around efficiency, the old GAC oval shaped lip expander is the unit of choice in my office.

DR. MASUNAGA I do not use any lip retractors, only cotton rolls.

DR. BRANDT Is the hair dryer an important adjunct in your bonding procedures? What does it do for you?

DR. GORELICK Yes, it is. It is used routinely after bracket placement to hasten setting time and to increase bond strength. It permits tying-in sooner.

DR. THOMAS I do not find it necessary to use these dryers. I like to work on the principle of keeping armamentarium as simple as possible, yet allowing me to have good consistent bonding.

DR. MASUNAGA I do not find it necessary to use a hair dryer to help keep a dry working area.

DR. ZACHRISSON I no longer use a hair dryer. It was of help in some patients to remove water after the spray rinse, but, with our present approach to moisture control, such armamentarium is notneeded.

DR. BRANDT What about dri-angles? Are they helpful? Where do you use them?

DR. ZACHRISSON I use dri-angles over the parotid duct as a routine. These are preferable to cotton rolls in that they do not restrict the working field. Dri-angles may be helpful also in the mandible to keep the tongue away, but this is not routine in my practice.

DR. GORELICK The dri-angles are very helpful. I use them whenever posterior teeth are being bonded. The dri-angles should be bent and placed high into the mucobuccal fold to cover the opening into the parotid glands. If necessary, two dri-angles, slightly overlapping, should be utilized. The foil-covered dri-angle is more expedient to use, since it is a more effective barrier. Arecently introduced plastic covered dri-angle, made by 3M, is equally effective.

DR. THOMAS A dri-angle that is an absorbent cardboard with a foil covering that is placed over the parotid ducts in the buccal area works nicely. The new product, developed by 3M, called Iso-Shields, are very good. We use them to retract the cheeks from the buccal surfaces fo the teeth and to absorb the moisture from that area in the mouth.

DR. BRANDT Do any of you use banthine tablets or probanthine injections for improved moisture control? Routinely? With what dosage?

DR. MASUNAGA I have never used any of these drugs for moisture control. I have been using cotton roll isolation and saliva ejectors. I dry the teeth thoroughly with an air syringe and, if necessary, wipe with ethyl alcohol to enhance drying before the adhesives are placed.

DR. THOMAS I no longer use any antisialogogue in my office. I started using banthine tablets as a routine and did so for approximately three months. I prescribed 100mg to each child about 30 minutes prior to the appointed time for bonding. Patients with heart conditions of any kind, urinary problems, glaucoma or intraocular pressures are not candidates for banthine. Those wearing contact lenses were asked to remove them until normal moisture returned to the eye mucosa. I do recommend that any orthodontist doing bonding for the first time use an antisialogogue, such as banthine, until he has good control of the technique. I do not like injections, and would prefer not to premedicate at all.

DR. ZACHRISSON Yes, having tested various types of antisialogogue tablets with varying degrees of success for some years, our experiences with probanthine injections over the past year are much more successful. In fact, they make bonding in the mandibular regions so comfortable, that I have now started to do this as a routine when bonding a full mandibular arch. There is a slight practical problem, however. Probanthine is delivered as a dry powder in vials of 30mg that should be dissolved in injectable (bacteriostatic) water in a rather complicated procedure described by White (JCO, October 1975) to produce the 0.6% solution for injection. Since probanthine solution cannot be stored for an extended period, Swartz (1977) has recommended simply to dissolve 1 mlof water into the 30mg vial, which would prepare injectable solution for 4-5 patients. Although our experience is in agreement with this approach, I would feel safer and more confident if the dry powder could be delivered in vials containing only 6mg for one patient, so as to completely eliminate the risk for bacterial or fungal contamination and reduced effect after refrigeration.

DR. BRANDT When you inject probanthine, where is it placed?

DR. ZACHRISSON There seems to be no difference in effect whether injections are made in the floor of the mouth or in the vestibular fold in either arch. The injections have definite advantages as compared with the more common use of tablets. The effect is seen immediately and the mouth is

dry within 5-10 minutes and remains so for about 2 hours. In spite of some individual variation, this procedure almost totally eliminates the need for saliva ejectors, dri-angles, cotton rolls, etc., and bonding can be done so much more easily without such gadgets in the mouth. Thus, I can safely etch, seal, and bond both the right and left sides of all maxillary and mandibular teeth in one operation.

DR. BRANDT What are the contraindications?

DR. ZACHRISSON Contraindications to the use of the drug are the same as for other anticholinergics; that is, patients with severe cardiac diseases, urinary diseases and glaucoma. Also patients with a known allergic reaction should not be given probanthine. It has been advocated also that persons wearing contact lenses should remove them when taking antisialogogues. Generally speaking, the outstanding thing about probanthine injections, as compared with the injection of other anticholinergics, like methylscopolamine and atropine sulphate, is that not only is the mode of action in terms of effect and duration more suitable for orthodontic bonding purposes, but the doses are much farther away from the recommended maximal doses. Thus, injections with dosages as high as 100mg daily are often given in medicine to ulcer patients, with no toxic effects (White 1975).

DR. BRANDT Please give our readers your added recommendations for improving moisture control.

DR. MASUNAGA Moisture control can be very tricky. If a combination water and air syringe is used to dry the teeth, the air will contain fine microscopic traces of moisture. It is better to install a separate air syringe. Many air compressors in the average dental office produce "wet air" due to condensation. A small unit called the "moisture collector" to dry the air can be installed. The dental assistant helps by holding the cotton rolls in place while drying the teeth with the air syringe.

DR. GORELICK In performing a molar-to-molar bonding procedure in the mandible, it is safer to bond one side at a time. If both sides are done, inadvertent salivary flow may occur due to gravity, as the head is turned for better access, and result in contamination. As for armamentarium, it is useful to have a high speed evacuator with a buccal and lingual ejector. A proper retractor, single and triple cotton rolls, and dri-angles are very helpful. A triple syringe that is air-water combination should be avoided because as the head of the syringe is tilted, moisture may come out inadvertently, even though it had been tested previously on a mirror.

In bonding to posterior teeth, one step that needs emphasis and is most critical is that right after etching and washing, the next step must take place very rapidly. The excess moisture is removed with the buccal and lingual high speed evacuators. A triple cotton roll is placed between the teeth to isolate and baffle the tongue. Individual cotton rolls are placed in the mucobuccal fold. This sops up remaining moisture and provides sufficient isolation so when the air syringe is applied, saliva and moisture are not sprayed back onto the tooth. The single cotton rolls are removed if they interfere and air syringe continues until sealant placement. The operator's eye does not leave the etched surface. This requires a four-handed approach to mix the sealant and adhesive. A four-handed approach increases bonding efficiency significantly.

DR. THOMAS Most of our patients are very impressionable, intelligent people. By using a simple technique called waking suggestion our patients can be taught how to maintain a dry mouth. This

requires no added chair time, no medications, and no particular ability in the use of waking suggestion. The technique is simple. It is explained that for this technique to work adequately you will need their 100% cooperation. Once the teeth have been isolated, the saliva ejector placed and the conditioning procedure is initiated, they must have a dry mouth, otherwise the brackets will not adhere; and they can help by noticing how dry their mouth is getting. The suggestion is that the air used to dry their teeth, and the saliva ejector, will cause their mouth to become drier and drier as you work. The more they think about the dryness, the drier it will get. Simple suggestions of this nature will be very effective in moisture control and is all that is used in our office. This is a technique that I urge everyone to try.

DR. ZACHRISSON The only further recommendations in addition to what I mentioned above would be that, when I do not use the probanthine injection, I have found a double hygoformic saliva ejector to be useful when bonding single brackets simultaneously on both sides of the mandibular arch, such as two lower second molar attachments at a late stage in treatment.

TO BE CONTINUED IN NEXT ISSUE