___.The first title above is that of the 8^th chapter in an eye-opening book to be released soon, “Risk management in orthodontics: Expert’s guide to malpractice”¹, Proposition 65, now law in California, does not sue only orthodontic manufacturers (among which TP Orthodontics, Ortho-Organizers, 3M Unitek), but also clinicians’ offices. Indeed, according to the determinations made by the Dental Board of California³, the composites used by dentists contain compounds that are listed in Proposition 65. On its way to spread throughout the world, this law has as its aim to protect California citizens and the State’s drinking water sources from chemicals known to cause cancer, birth defects or other reproductive harm, and to inform about exposures to such chemicals. After mentioning his pa-tients problems with elastomers, the editor of the Am. Journal of Orthodontics & Dentofac. Orthop3 agreed that more research into the safety of the currently used orthodontic materials is needed and that patients should be better informed. “A dental practitioner should not asume that a dental product that can be purchased or is promoted in prominent dental publications necessarily fullfils all the advertised claims”⁴
___.Authorities’ attempt to control the iatrogenic effect of biomaterials may have started in Germany and Japan. The first country is host to ISO’s ‘Technical Committee 106 (Dental Products) that, among others, was the first to impose strict limits on the nickel in dental alloys: in Japan, the same task is carried out by the Ministry of Health. Germany’s concern that with harmful materials was evidenced by the recent selection by the journal Kieferorthopadie Nachrichten (News in Orthodontics5: of the many studies presented at the 79^th annual congres of the European Orthodontic Society in Prague, 2003, its choice was our study entitled “How to test biomaterials for safety” (see a portion of this two parts article in the next page).
___.The problem raised by the materials coming in contact with humans may have been first raised by the famous physician and alchemist Philippus Aureolus Theophrastus Bombastus von Hohenheim (1493-1541), who called himself Paracelsus (“Superior to Celsus”, an early Roman physician): “All substances are poisons. There is none which is not a poison. The right dose differentiates a poison from a remedy”. This may not have changed much after almost half of a millennium. Thus, Dr. Michael Spector, President of the Society for Biomaterials, delivered feweqars ago a keynote speach titled “Biomaterials: Taming the Beast”⁶. Some 10% of the studies published in the adjacent journals, all dedicated to biomaterials, are concerned with their noxious effects. As Benjamin Franklin once said, “an ounce of prevention is worth a pound of cure”: the simple procedure outlined in the following article should help any willing clinician to disclose leaching plastics.
References
1. Matasa CG, Polymers in Orthodontics: a Present Danger? In: Graber TM, Eliades T, Athanasiou AE editors, Quintessence, Chicago, 2004.
2. Composite resins: Dental Materials Fact Sheet), Chapter 801, Statutes of 1992, Dental Board of California http://www.cda.org/press/dental_ materials_factsheet_2001.htm,
3. Turpin DL, California proposition may help patients in search of better oral health, Am. J. Orthod. Dentofac Orthop. 2001: 120: 97
4. Stanley RH, in: Phillips’ Science of Dental Materials, Xth ed., Anusavice KJ, ed., WB Saunders, Philadelphia, 1996
5. Matasa CG, Wie man Biomaterialien aus Sicherheitsgrunden uberpruft, Kieferorthopadie Nachrichthen, Leipzig, 2003; 3 (October); 4-5
6. Spector M, Biomaterials: Taming the Beast. J. Biomed Mater Res 1992; 26: 1-5

Reactive gel entrapment, a new, simple way to
test leaching plastics

___.In two of our preceeding issues^1,2, as well as in an article recently published in World J. Orthodontics³, we have shown that it is possible to detect leaching plastics by submerging these in an acid solution of potassium permanganate, MnO₄K. This strongly oxidizing agent changes color as it is reduced, its fading indicating a certain degree of leaching particular to each sample. To use the method, equal weights of the minced samples were immersed separately in the same permanganate solution and then juxtaposed. Visual observation being subjective, for a more accurate reading, the use of a colorimeter or a spectrophotometer becomes necessary.
___.In contrast, reactive gel entrapment, a method we have developed and used to evaluate heavy metal leaching4, allows one to compare simultaneously a variety of plastics without having to transform these to a powder, a particularly difficult operation when applied to soft materials.
___.The test is based upon the fact that in while oxidizing a large spectrum of organic compounds, the related reduction of potassium permanganate, is accompanied by a change in color. Thus, in its higher state of oxidation, heptavalent manganese ions (Mn^VII) exhibit a purple color. When reduced to Mn^IV, the resulting manganese dioxide precipitates as a dark particles. In the presence of even small amounts of strong acids, this oxide is dissolved and reduced to colorless, soluble salts (Mn^II). In a gel, this leads to a noticeable white aura around the immersed plastic device, its further spreading being hindered by the gel’s retentive properties: the phenomenon is widely exploited in gel chromatography.
Materials and method
___.The plastic devices tested were:
a. Elastomeric ligatures from: Class One (Lubbock, TX), Ortho Source (North Hollywood, CA), Ortho Byte (Wilmington, DE, USA), Forestadent (St. Louis, MO, USA), Centric (Marietta, GA, USA), Lancer (San Marcos, CA, USA), Oscar (Indianapolis, IN, USA), Ormco (Orange, CA, USA), H. Schein (Melville, NY, USA), Unitek (Monrovia, CA, USA), Ortho Arch (Schaumburg, IL, USA), Ortho Specialty (Hickory Hills, IL, USA), GAC (Bohemia, NY, USA), Dynaflex (St. Louis, MO, USA), “A”-Co/Ormco (see above), American Orthodontics (Sheboygan, WI, USA), Adenta (Gilching, Germany);
b. Sealants and adhesives from: Dentsply/Caulk (Milford, DE, USA), Reliance (Itasca, IL, USA), Kerr (Orange, CA, USA), Lee Pharmacuticals (South El Monte, CA, USA). American Orthodontics, 3M/Unitek (see above), Bisco (Schaumburg, IL, USA), ESPE (Seefeld, Germany), Fuji Ortho (GC America, Chicago, IL, USA);
c. Composites and restoratives from some of the above companies and from Lang Dental (Wheeling, IL, USA);
d. Mouth guards and retainers from Masel (Bristol, PA, USA),Twin Lakes Labs (Union Mills, IN, USA), Raintree Essix (Maitairie, LA, USA), Walgreens (Deerfield, IL, USA), Align Technologies (Santa Clara, CA, USA), Athletic Works (Bentonville, AR, USA), Tru-Tain Orthod. (Rochester, MN, USA) Premier Dental (Norristown, PA, USA) .
___.All these devices were immersed as is (i.e. without rinsing), in gels which were obtained either by dissolving in distilled water 99+% granular potassium permanganate (Acros, Pittsburg, PA, USA; CAS#: 7722-64-7) and leaving them to rest for few days in a dark glass container, or by using a ready made 0.2% solution of potassium permanganate (0.05N, equivalent to 0.01M (Lab Chem, Pittsburgh, PA). In both cases, the solutions were acidified with sulfuric acid (Spectrum, Gardena, CA, CAS#: 7664-93-9) to pH 2 and then gellified by thoroughly stirring these with fumed silica (Aerosil 200, Degussa, Cleveland, OH, CAS#: 7631-86-9; CAS#: 112945-52-5). Since the reaction is very sensitive, it allows to evaluate even minute amounts of organic compounds in drinking water (see the Permanganate Index⁵). To evaluate small leachings, only low concentration permanganate solutions should be used .
In aqueous solution, potassium permanganate is unstable, leading to the formation of manganese dioxide, a dark precipitate. This reaction is not only catalyzed by impurities, but also autocatalytic, i.e. the more this oxide is formed, the faster the decomposition of the rest of the permanganate. To promote the desirable reaction of oxidation against the reaction of decomposition, purity and a lower pH is essential.

___.Important factors are the thickness of the gel and the concentration in permanganate: a too thick gel leads to smaller white auras. High concentrations of permanganate (Mn^VII, purple) may mask with its strong purple color the smaller amount of manganese that has been rendered colorless. The color changes in time: after a while and even in the presence of acids, the purple, Mn^VII ions turn brown due to the dioxide formed (Mn^IV): after a longer time, the color fades (Mn^II, clear).
Elastomeric ligatures. Sticks and chains immersed in Babes-Petri dishes containing each 25 ml of a solution of 0.3 g permanganate in water were photographed after a week exposure, before and after removing the elastomers Fig.1 & 2.
Sealants and adhesives. Equal hemipheres having 0.5cm diameter, made using a dent as a mold, were immersed in the gel above, acidified to pH 2 and photographed after 24h. Leaching in time was tested by immersing the samples in ceramic plate containing a gel made of 100 ml aqueous soln containing 2 g/l MnO₄K, 500 ml water, 45 g silica and 3 ml sulfuric acid. After 24 h and without moving the samples, the gel in each dish was carefuly removed and replaced with a new one having the same composition, and photographed.
Restoratives. The influence of post-treatment on leaching has been evaluated on a cold cure acrylate (Jet, Lang Dental, Wheeling, IL). The hemispheres made as described above were treated in different ways before their exposure to the gel described above for 24 h, Fig.7. The treated samples were arranged in columns: A was used for controls, i.e. for untreated samples, B for these left for 24 h in water added with a detergent followed by intense rinsing, C for boiled for ten minutes in water and D for these left for 24 h in rubbing alcohol (70% isopropanol).
___.To test leaching as a function of the ratio between the parts in chemically cured systems, equal hemispheres of these (liquid-liquid, paste-paste, liquid-powder) were made both by using the proportions recommended by their manufacturer, and by doubling or halving them. After being immersed in rows in the gel described above, these were photographed after 24 h, as seen in Fig. 8.
Mouth guards, retainers. Various plastic devices were partially immersed in gels made from 75g fumed silica and a solution comprising 10 cc 0.02% permanganate solution, 2 ml sulfuric acid and 1000cc distilled water, all placed in flat ceramic containers and covered with clinging plastic foils to limit evaporation. After durations varying between few hours to several days, the cover was removed and the system was photographed with a digital camera Nikon Coolpix 950, Fig. 9 & 10.
___.In an attempt to quantify the observed leaching, in the gel were partially immersed two identical double cushion mouth guards from Athletic works and a bar of dense hydroxyapatite (CAM Implants, Leiden, Netherlands). In parallel, one drop each (0.03 cc) of three oxalic acid solutions (1/100, 1/1000 and 1/10,000 weight in water) were added. Drops of the last two concentrations were placed also along the ceramic bar, Fig. 11. After a week, the size of the auras formed around the drops and the mouthguards were examined to evaluate the permanganate reacted, in a direct relation with the amount of leachate.

Qualitative results
Elastomeric ligatures. Almost all of these have leached: the smaller auras shown by the chains is due only to the smaller volumes involved. The brown color of the gel surrounding the white spots shows that, due to a long exposure, most of the manganese has taken the form of oxide, Fig.1 & 2.
Sealants and adhesives. The tests show that even after the gel was replaced three times, the polymers continued to leach, Fig. 3-6.
Restoratives. As column C in Fig. 7 shows, only boiling is effective enough to reduce leaching: the extraction with rubbing alcohol gave mixed results, as the composite actually absorbed part of it.
___.As Fig. 8 shows, significantly changing the proportion between the two parts of the composites tested didn’t affect too much their leaching.
Mouth guards, retainers. As the permangante solution was too concentrated, i.e. less sensitive, only two items showed some leaching, Fig. 10, column C (C-2 and C-4).
Quantitative results
___.The size and intensity of the auras generated by the mouth guards in the permanganate gel shown in Fig.11 can be compared with these surrounding the purposely added drops of the three oxalic acid solutions, each having a different concentration.
___.Analytical chemistry teaches that the decomposition of this acid into water and carbon dioxide takes place in direct proportion with the potassium permanganate consumed (the system is used as a standard in redox reactions):
___.___.16H⁺(aq)+2MnO₄-(aq)+5C₂O₄^2-(aq)=10CO₂(g)+2Mn²⁺(aq)+8H₂O(l)
___.Fig. 11 shows that the extent of the stain generated by the mouth guards is equivalent to that surrounding the drop containing 1/1000 oxalic acid. Based upon the molecular weights of the reagents involved, it is feasible to calculate the amount of lechate. Knowing the amount of that 158g of potassium permanganate are consumed to oxidize 90 g of oxalic acid, it is possible to infer how much of another reducing agent certain compound could generate a similar aura. If there is a single compound and its formula is known, the amount of lechate can be stoechiometrically calculated.
Discussion
___.In the presence of organic compounds, permangante ions decompose freeing oxygen in the presence of organic compounds:
___.___.4 MnO₄-(aq) + 4 H⁺(org) = 3 O₂(g) + 2 H₂O + 4 MnO₂(s)
___.The oxygen released transforms organic compounds in water and carbon dioxide almost quantitatively. The reaction can be so violent that if a drop of certain organic compounds is placed on a pile of solid permanganate,a flame is produced. In a gel, the mass transfer af the reagents is considerably slowed down, the unreacted permanganate being reduced into oxides and, in the presence of acids, into salts3. Details about permanganate’s reaction and the oxido-reduction process (redox) can be found on the Internet⁶.
___.As a difference from manganimetry, a method based upon the use of potassium permanganate to quickly evaluate the redox potential of various soluble systems, plastics continue to leach in time, as demonstrate Fig. 3-6 and 7. In other words, by the orthodontic devices continue to leach, the permanganate may have been already converted, i.e. ceased to be active. Even so, leaching can be acceptably estimated from the aura it generates for up to a week. As the size of the aura expands in time and varies with many parameters, an absolute evaluation may not feasible, leaving thus room for comparisons. These can be performed between similar devices, or related to standard reducing substances such as oxalic acid. In the last case, data can be obtained everywhere and without the need for other devices to be used as controls. In water testing and in the chemical industry, the purity of acetic acid, acetic anhydride, caprolactam, ethanol, methanol, pyridine, and tricresyl phosphate are evaluated by measuring time till the color of potassium permangante fades away.
___.Discussing each of the devices tested, it is obvious that elastomeric ligatures are leaching enough to generate problems, as shown in the previous article and in literature⁷. Only their relatively small volume may prevent these from being significantly hazardous. Their composition varies substantially from one brand to another, as shown by traces left behind in Fig. 1 and 2.
___.Plastic’s leaching in an aqueous environment at room temperature should decrease in time, leading eventually to a plateau^8-1. This is confirmed in Fig. 3-6 which show that the process continues after three gel substitutions, each followed by a day exposure.
___.Several attempts to curb leaching are shown in Fig. 7. Leaving over night a cured composite in water, even in the facilitating presence of a detergent, does not stop leaching, and neither does it an extraction with 70% isopropanol. Interestingly, the enhanced leaching shown by the composite demonstrates that some of the solvent has been absorbed in the polymer’s mass. In contrast, boiling the plastic for ten mintes in water (column C) stops leaching.
___.The variation of the ratio between the parts in a chemically cured system, may lead at some point to a more complete polymerization, but does not influence significantly leaching, as shown in Fig. 8. Neither the correct ratio, nor the use in excess of one part or the other of the system, do not seem to reduce it. As a difference from the plastic devices cured in the oral environment, those factory made, ready-to use exhibit less leaching. As expected, those destined for shorter exposures, such as the mouthguards, showed more leaching, Fig. 9, 10 and 11.
___.The addition of known solutions of oxalic acid provide, using standard conditions and a definite time, an independent method of evaluating the extent of the leaching. Besides comparing the leaching of various polymeric devices, the method can used to compare the aura generated not with known plastics, but with that of a common chemical compound. For a real quantitative evaluation, it may become necessary to differentiate the pink color of the permanganate from the brown of the manganese dioxide, operation feasible when using spectrophotometers¹³.
___.While an accurate quantitative analysis may not be feasible due to the number of variables possible, the size of the white aura formed around the plastic tested can be related to the one generated around a known amount of oxalic acid added to the same gel and thus to the amounts of permanganate and lechate reacted.

Conclusions
___.The color fading of the permanganate solutions is a time-proven method to measure the purity of many chemical substances. As far as we know, its use to determine leaching has never been used before, as is that of reactive gel entrapment, a method paralleling gel chromatography.
___.The combination of the two methods as shown above allows to discriminate dental devices using simple means. The examples studied above are just a fraction of their possible application: in the next issue we will continue to compare the leaching of other, polymer-derived dental devices. Further research may lead to refinements that would render even easier the detection of the harmful ones, building instead confidence in the acceptable ones.
___.While the method doesn’t discriminate between harmless and harmful leachates, and the amount and toxicity of the leached compounds may vary from a plastic device to another, it is safe to claim that in all cases leaching is highly undesirable. Allowing at once the visual comparison of many samples, the method substitutes spectrophotometric analyses which require not ony expensive instruments, but also highly qualified personnel.
___.The method allows both manufacturers and clinicians to prevent patient afflictions and their highly undesirable consequences, as examined in the preceeding article.
References
1. Matasa CG, A do-it-yourself detection of leaching polymers, The Orthodontic Materials Insider, 2002; 14 (1): 5-7
2. Matasa CG, A leaching test for plastic retainers, The Orthodontic Materials Insider, 2002; 14 (2): 7-8
3. Matasa CG, Screening orthodontic polymers for leaching, World J. Orthod. 2003; 4: 157-161
4. Matasa CG, Heavy metal release: a do-it-yourself test,World J. Orthod. 2003; 4: 348-357
5. Water Quality. Determination of Permanganate Index. Geneva: ISO 8467, 1993.6.
6. http://dbhs.wvusd.k12.ca.us/Redox/Meaning-of-Redox.html ( Last accessed March 2004)
7. Holmes J,. Barker MK, Walley EK, Tuncay OC, Cytotoxicity of orthodontic elastics Am J Orthod Dentofac Orthop 1993;104:188-91
8. Lee SY, Huang HM, Lin CY, Shih YH, Leached components from dental composites in oral simulating fluids and the resultant composite strengths, J Oral Rehab 25(8):575-88, 1998
9. Eliades T, Eliades G, Brantley WA, Johnston WM, Residual monomer leaching from chemically cured and visible light cured adhesives, Am J. Orthod Dentofac Orthop 1995; 108: 316-321
10. Geurtsen W, Substances released from dental resin composites and glass ionomer cements, Eur. J Oral Sci 1998; 106(2): 687-9
11.Thompson LR, Miller EG, Bowels WH. Leaching of unpolymerized materials from orthodontic bonding resins, J Dent Res 1982; 61: 989-92
12. Ferracane JL, Gordon JR. Rate of elution of leachable components from composites. Dent Mater 1990; 6: 282-7
13. http://www.paa.co.uk/process/products/ptscan.asp, Last accessed March 2004

See for yourself the difference!
There is no more need of sophisticated instruments
to test recycled brackets

___.Five years ago, we listed some thirty orthodontic recyclers spread all over the world: since then, their number has increased, as the savings they generate are substantial. Among recyclers, Ortho-Cycle Co. is the only one that, besides being accepted in the USA by FDA, has been globally certified to refurbish orthodontic attachments, see adjoining copies (ISO 9001: 2000, as well as the latest, ISO 13485: 2003 and EN 46002: 1996). In addition, it has been CE-certified for the production of medical devices for dentistry by the very respectable Scandinavian Institute of Dental Materials, in accordance with the European Economic Community (Council Directive 93/42) .
___.A quarter century ago, Buchman was the first to test brackets subjected to different refurbishing processes: measuring their magnetic properties (the Curie point), he found that only Ortho-Cycle‘s did not have the metal’s microstructure altered1. After twenty years, an accurate measurement of the dimensional changes involved in Ortho-Cycle’s process showed these to become insignificant when electro-polishing was replaced by burnishing2.
___.Today, anyone can see the differences: if thermally treated,gold-plated brackets will turn dark, and active, self-engaging ones will have their elastic spring annealed, i.e. having lost their springiness.In contrast, if properly gilded and the refurbished by Ortho-Cycle, the gold-plated ones will look like those shown below; likewise, removed escape-proof spring clips from Speed brackets (Strite Ind., Cambridge, ONT, Canada) will return to their initial form after being forcibly opened, see sketch. Try it for yourself!
References
1. Buchman DJL, Recycling of metallic brackets, Am J. Orthod. Dentofac Orthop 1980; 77: 654-668
2. Matasa CG., Orthodontic recycling at the crossroads, J. Clin. Orthod. 2003; 37(3): 133-138

___.Stop at our booths at the AAO meeting in Orlando, Florida, booth 2417, or at the EOS meeting in Aarhus, Denmark, to pick up your complementary gauges (.018" or .022") to help you save money by debonding undamaged brackets.
___.Bring your brackets/bands for reconditioning, or claim your already ordered purchase orders. Ask for info & details, we will be glad to share!