British Journal of Orthodontics
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Decalcification During Orthodontic Treatment With Fixed Appliances—An Overview L. Mitchell B.D.S., F.D.S., M.D.S., D.Orth., M.Orth To cite this article: L. Mitchell B.D.S., F.D.S., M.D.S., D.Orth., M.Orth (1992) Decalcification During Orthodontic Treatment With Fixed Appliances—An Overview, British Journal of Orthodontics, 19:3, 199-205, DOI: 10.1179/bjo.19.3.199 To link to this article: http://dx.doi.org/10.1179/bjo.19.3.199
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British Journal of Orthodontics/ Vol. 19/1992/199-205
Decalcification During Orthodontic Treatment With Fixed Appliances-An Overview L. MITCHELL, B.D.S., F.D.S., M.D.S., D.ORTH., M. 0RTH Department of Orthodontics, The Dental School, Framlington Place, Newcastle upon Tyne NE4 48W Received for publication June 1991
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A~stract. The prevalence and aetiology ofdecalcification during orthodontic treatment with fixed appliances is dtscussed and consideration given to the methods of reducing this problem.
Index words: Decalcification, Fixed Appliances.
Introduction Decalcification is defined as loss of calcified tooth substance, and it occurs when the pH of the oral environment favours diffusion of calcium and phosphate ions out of the enamel. This dissolution follows the production of acid by bacterial plaque and results in an altered appearance of the tooth sur~ace. The early lesion is an opaque white spot, W~Ich in active lesions appears chalky, and if mmeralloss continues, frank cavitation may result. An accumulation of bacterial plaque and a supply of fermentable sugars are the prerequisites for decalcification to occur. Unfortunately, fixed orthodontic appliances hinder tooth cleaning, and favour plaque and food retention. A rise in the numbers of Streptococcus mutans and lactobacilli has been reported following the placement of orthodontic appliances (Lundstrom and Krasse, 1987). These micro-organisms are associated with the initiation of dental caries and further development of the carious lesion, respectively, and their presence increases the risk of decalcification occurring (Schwaninger and Vickers-Schwaninger, 1979).
Prevalence Ea~ly studies in this field investigated the overall canes experience of orthodontic patients and found that although the total number of carious lesions in this group did not differ significantly from untreated individuals, a greater proportion of buccal and lingual surface lesions were seen (Wisth and Nord, 1977). Subsequent workers have attempted 0301-22X/92/008000 + OOS02.00
to quantify the extent of the risk posed by decalcification during orthodontic treatment (Table 1). The prevalence reported among patients ranges from 2 to 96 per cent. This large variation is due to the variety of methods used to assess and score the presence of decalcification, whether idiopathic enamellucencies were included or excluded, and the use or otherwise of a fluoride regime during treatment. In a cross-sectional study design (orthodontic patients after treatment compared with another group of patients who have not had orthodontics) it is difficult to distinguish between idiopathic white spots and decalcification, which artificially increases the prevalence quoted. Zachrisson and Zachrisson ( 1971 ), and Zachrisson ( 1977) employed a longitudinal design and recorded only new white spots developing, yet despite this, the prevalences they found were 89 and 15 per cent, respectively. Surprisingly, only Stratemann and Shannon (1974), and Mizrahi (1982, 1983) used photographs to back up their clinical assessment. The results are more encouraging where the prevalence for teeth is quoted, as the results ranged from 0 to 24 per cent. The distribution of affected teeth has been studied by several workers. Gorelick et al. ( 1982) found maxillary incisors and mandibular first molars to be the teeth with the highest prevalence. Mizrahi (1983) found maxillary incisors and first molars to be most commonly affected. He also reported that the enamel opacities were found particularly on the cervical and middle thirds of the vestibular surface of affected teeth. 0gaard (1989) also found the first permanent molars in both arches to have the highest prevalence. In contrast, Geiger et al. (1988) reported that lesions occurred most frequently on © 1992 British Society ror the Study or Orthodontics
200 L. Mitchell
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TABLE I Studies into the prevalence of decalcification during fixed orthodontic treatment (whole mouth studies only)
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Comments
5·8% test teeth 23·8% control teeth
Test teeth treated with varnish prior to band placement
89% patients
Fluoride mouthrinse used during ortho.
58% of patients without fluoride 2% of patients on fluoride regime 15% patients
Comparison of prevalence in orthodontic patients with or without fluoride gel regime Fluoride mouthrinse used during ortho.
Design
Meyers 1952
Longitudinal Direct visual assessment
Zachrisson and Zachrisson (1971)
Longitudinal Direct visual assessment Direct visual assessment with photos
Caries ind~x (Fehr, 1961)
Zachrisson (1977)
Longitudinal Direct visual assessment
Gore lick et al. (1982)
Direct visual assessment at end of treatment
'New white spots' noted Presence (and severity) or absence of white spots
Mizrahi (1982, 1983)
Cross-sectional Direct visual assessment. In small sub-group photos used as well
Scored white opacities (after Curzon and Spector (1975))
Artun and Brobakken (1986)
Cross-sectional. Direct visual assessment
59% of patients Caries Index and Gorelick's after ortho. 45% of patients not Index requiring ortho.
Fluoride mouthrinse used during ortho.
Geiger et al. (1988)
Gorelick et al. ( 1972) used as baseline. Direct visual assessment Cross-sectional. Direct visual assessment
Gore lick's Index
34% of patients. 7·5% of teeth
Fluoride programme.
Gorelick's Index
95% of patients 5-7 years after ortho. 85% non-orthodontic controls.
Fluoride mouthrinse used during ortho.
After Mizrahi (1982)
13"/c, of teeth with Comparison of 2 adhesives conventional adhesive with and without fluoride. 0% of teeth with Fluoride adhesive
Stratemann and Shannon (1974)
0gaard (1989)
Sonis and Snell (1989) Scored at end of treatment by direct visual assessment
Index used
Prevalence
Author
maxillary lateral incisors and canines, and on mandibular premolars. In the studies by Meyers (1952), Zachrisson and z,achrisson (1971), Stratemann and Shannon (1974), and Mizrahi (1983, 1988) only bands were used, whereas in the remaining studies bonds were used on the anterior teeth. From Table I, it would appear that the method used to assess and score either the presence or absence of decalcification has a greater effect upon the prevalence noted, than the use of bands or bonded attachments. There has been considerable debate in the literature on the effect upon the enamel of the material used to cement orthodontic bands, particularly in relation to zinc phosphate cement. However, Durning (1989) in a comprehensive review of the problem, concluded that enamel surface • changes beneath orthodontic bands are due to a loss of integrity of the cement lute followed by accumu-
50% patients 11"1.. teeth
84% of patients after ortho. 72% of patients prior to ortho.
lation of oral fluids or bacteria in the space, which allows destructive processes to progress undetected. Aetiology
The inter-dependence of bacteria, sugar, enamel, and time in the aetiology of caries is well accepted (Murray, 1989), however, a number of factors can predispose to decalcification or increase its risk during orthodontic treatment, and these are considered briefly below. Oral hygiene
The presence of orthodontic attachments make tooth cleaning more difficult, and predispose to a build-up of plaque on the tooth surface around the attachment, and between it and the gingival margin (Ciancio et al., 1985). Streptococcus mutans and
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201
lactobacilli are associated with the initiation and development of caries and especially colonize tooth sites described as retentive (Lundstrom and Krasse, 1987). In addition, a layer of plaque on an enamel surface not only provides a source of acid production in the presence of a sugary substrate, but also acts as a physical barrier limiting the diffusion of acid away from the tooth surface, and preventing remineralization from calcium and phosphate ions in the saliva. Given these factors it is not surprising that decalcification is particularly associated with those areas where plaque accumulation occurs in the orthodontic patient (Saloum and Sondhi, 1987).
Careful consideration should be given to the design of bonded retainers as those too can hinder tooth cleaning. Bonding technique
The presence of adhesive 'flash' around a bonded orthodontic attachment can predispose to plaque accumulation (Gwinnett and Ceen, 1979), therefore, any excess should be cleared away before the adhesive cures. Methods of Reducing Decalcification During Fixed Orthodontic Treatment
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Diet
The role of fermentable carbohydrate in caries has been well documented (Murray, 1989). Frequent consumption of sugary foods or drinks has been shown to be most damaging, as following sugar intake the pH of plaque drops below the critical level of 5·5 for about 20 minutes. In addition, fixed appliances restrict the ability of the tongue and saliva to remove food particles from the mouth, with the result that breakdown of more complex carbohydrates gives rise to a prolonged acid challenge to the tooth surface. Appliance type and design
Generally, as the proportion of tooth surface covered by an orthodontic bracket increases, the more difficult it becomes for the patient to effectively clean the remaining uncovered enamel. However, this does not mean that using bands rather than bonded attachments is more likely to result in decalcification. In practice, a well cemented band appears to be protective of the tooth surface it covers, although should the cement lute fail, extensive demineralization can occur if the band is left in situ for any length of time (Zachrisson, l975b). In their study Gore lick et al. ( 1982), found no difference in the prevalence of white spot lesions in bonded or banded teeth. However, the site of plaque accumulation does differ between bonds and bands, with the latter favouring the development of plaque around the gingival margin (Ciancio et al., 1985) with an increase in the potential for loss of periodontal support. Archwire design will also affect the accumulation of plaque and food debris. One of the major disadvantages of the Begg appliance is the difficulty patients experience cleaning around the looped archwires and auxiliaries. However, the use of elastic thread or chain and other auxiliaries with any technique will make cleaning more difficult.
Patient selection and education
Most operators insist on a patient attammg a certain level of oral cleanliness before embarking on orthodontic treatment. However, there will always be a proportion of patients whose ability to clean their teeth deteriorates as treatment progresses. Remotivation and education of the patient in the importance of diet and tooth cleaning throughout treatment, ideally by a hygienist, can help to reduce this problem, but will not eliminate it. Lundstrom and Krasse ( 1987) have suggested using microbial monitoring to identify those patients most at risk of decalcification, as evidenced by high salivary Streptococus mutans and lactobacilli counts, and targeting them. Oral hygiene instruction
Although professional oral hygiene instruction for the duration of treatment has been shown to be effective in reducing decalcification (Artun and Brobakken, 1986), this approach is very labour intensive and costly. However, periodic re-inforcement by a professional can help to remotivate a patient and correct any errors in technique (Lundstrom et al., 1980). Bacterial plaque can be removed mechanically and/or chemically. Mechanical plaque removal. There is now an almost bewildering array of toothbrushes and cleaning aids available to the public. Some manufacturers even produce special orthodontic toothbrushes with a groove along the length of the head designed to fit over the brackets and archwire. There appears to be little hard evidence to support the contention that any type or design of toothbrush, or any toothbrushing technique is superior to another (Williams et al., 1987). However, toothbrushing twice daily with a conventional or othodontic brush should be supplemented by an
202
L. Mitchell
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interdental cleaning aid, e.g. a single tufted toothbrush, to clean between the teeth and under the archwire (Casey, 1988), and patients must be informed that it will take longer to clean effectively around a fixed appliance, than before orthodontic treatment. Electric toothbrushes and oral irrigation systems are heavily promoted by their manufacturers. The results of studies which have examined the effectiveness of an electric over a manual toothbrush for orthodontic patients are equivocal (Boyd et al., 1989; Jackson, 1991). However, Attarzadeh, (1986) suggested that oral irrigation should only be .used as an adjunct to other methods of tooth cleamng. Chemical plaque removal. It has been postulated that to be effective a chemical plaque remover must be capable of reducing the oral flora by 99·9 per cent (Hogg, 1990). In addition, the agent must not upset the balance of the oral microflora or promote resistant micro-organisms and be non-toxic. Given these stringent requirements it is surprising that any product has been developed as a chemical antiplaque agent. Nevertheless, a number of proprietary antiseptics are now available which claim to be active against plaque bacteria. Of these chlorhexidine is the most effective, due to its absorption onto the acquired pellicle, which prolongs its presence and effect in the mouth (Hogg, 1990). Chlorhexidine is not without its disadvantages, the most pertinent to orthodontics being the deposition of a brown stain. However, this staining is readily removed, albeit not until the end of active appliance therapy (Brightman et al., 1991). A recent study by Lundstrom and Krasse (1987), looked at the effect of chemical control (with chlorhexidine) of the numbers of Streptococus mutans in patients undergoing fixed orthodontic treatment. The subjects were selected for the study because of their initial high levels of Streptococcus 11)Utans (and associated high risk of decalcification), ano all received oral hygiene instruction, dietary advice, and topical fluoride, in addition to the application of chlorhexidine gel. The authors found that the chlorhexidine treatment had an additional preventive effect, but felt the gain was small, and did not justify the time and cost involved. Reducing plaque retention by the appliance
Selection of small brackets and their use with a careful technique involving removal of any composite flash, minimal use of looped archwires, and periodic checking of the cement Jute under bands, will help to reduce plaque accumulation by the appliance and decalcification.
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Protecting the enamel surface around attachments
Attempts at reducing the susceptibility of enamel to surface change have centred around two approaches. The first is directed at strengthening the enamel and reducing its acid solubility-that is, the use of topical fluoride agents before, during, and after orthodontic treatment. This approach is considered in more detail in the section entitled 'Fluoride' below. The other method involves protecting the surface of the tooth around and beneath the orthodontic attachment with a protective coating and a number of materials have been investigated. A polymer adhesive Protecto® (Lee Pharmaceuticals, South El Monte, California 91733) was used successfully by Tillery et al. ( 1976) to reduce decalcification under othodontic bands, but a subsequent study by Younis et al. (1979) found NuvaseaJ® (LD Caulk Division of the Amalgamated Dental Company, London), a fissure sealing material, to be more effective than Protecto. Painting sealant resin around orthodontic bonds has also been suggested, but oxygen inhibition of polymerisation limits the protection that is afforded (Saloum and Sondhi, 1987). A varnish containing 45 per cent chlorhexidine was found to reduce the numbers of Streptococus mutans 10-fold, locally, 22 weeks after a single application to the occlusal fissures of test teeth (Schaeken et al., 1989). Whether this varnish could provide a protective coating around orthodontic bonded attachments remains speculative, but is worthy of investigation. Fluoride
Post-eruptively fluoride can reduce caries by: ( 1) acting as a type of catalyst favouring the formation of high quality hydroxyapatite; (2) by aiding remineralisation during pH fluctuations; (3) by inhibiting glycolysis of plaque bacteria ( Levine, 1991 ). Almost all patients use a fluoridated toothpaste and for many this will suffice; however, for susceptible patients a number of different approaches have been employed to increase the availability of fluoride ions around fixed orthodontic attachments. Mouth-rinsing. Daily rinsing with a 0·5 per cent sodium fluoride solution has been shown to be effective at reducing the prevalence of decalcification during orthodontic treatment (Zachrisson, 1975a; Saloum and Sondhi, 1987). A number of other fluoride compounds have also been investi-
BJO August 1992
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gated, e.g. stannous fluoride, acidulated phosphate fluoride, but they appear to be no more effective than sodium fluoride (Carlos, 1985). The drawback to this approach is that those patients who would most benefit from topical fluoride are the least likely to comply with a regular rinsing regime. Professionally applied fluoride. Several investigators have advocated the application of topical fluoride before etching (Saloum and Sondhi, 1987); however, it has been shown that the bond strength between fissure sealant resin and enamel is reduced following a fluoride pre-etching treatment (Low et al., 1975). Interestingly, a recent study by Wang and Sheen (1991) using the technique prior to placing orthodontic bonds found no significant effect upon bond strength, but reported that enamel detachment during de-bonding was a potential complication. This problem was not reported in an in vitro study of sodium fluoride application, after etching, which also found no significant effect upon bond strength (Bishara et al., 1989). Only one study has examined the effect of fluoride varnish applied prior to placement of orthodontic bands (Adriaens et al., 1990). A polyurethane varnish containing 0·7 per cent fluoride was used in vivo and was found to significantly reduce decalcification under well fitting bands. Professional fluoride gel applications during orthodontic treatment are of proven efficacy (Zachrisson, 1975b; O'Reilly and Featherstone, 1985), but like professional tooth cleaning are expensive of operator time. Fluoride containing etchant. An in vitro study by Thornton (1986) concluded that the addition of fluoride to phosphoric acid etchant had little or no protective effect, which perhaps is not surprising given that etchant dissolves the enamel surface and is then rinsed away. Fluoride containing cements for banding. The development of fluoride containing cements for placing orthodontic bands has been extensively reviewed by Durning (1989). Interest now focuses on the polyalkenoate cements which have been shown clinically to be associated with less decalcification than zinc phosphate or zinc polyacrylate (Maijer and Smith, 1988; Mizrahi, 1988; Durning, 1989). Whether this is due to the increased fluoride content of glass ionomer cements per se, or their increased adhesion and better band retention, is still controversial. Fluoride containing bonding adhesives. Interest currently centres around two different types of fluoride containing material for attaching ortho-
Decalcification during Treatment with Fixed Appliances
203
dontic brackets. These are glass ionomer and composite resin to which fluoride has been added. An in vitro study (Valk and Davidson, 1987) indicated that glass ionomer cement protected the enamel beneath and also I mm around an orthodontic attachment, from decalcification. However, glass ionomer has been shown to have a weaker bond strength than composite (Cook and Youngson, 1988). Despite this, adequate retention has been reported clinically by Cook ( 1990) in 40 consecutive cases. The results of the studies by Sonis and Snell (1989), and Underwood et al. (1989) in America into the clinical durability and caries inhibition potential of fluoride releasing composite resins were encouraging, although a subsequent study (Chan et al., 1990) into the light-activated material used by Sonis and Snell reported that its tensile bond strength was significantly less than a conventional resin. However, Bishara et al. ( 1991) concluded that this was due to inadequate polymerization, rather than the addition of sodium fluoride. An in vivo investigation by Fox ( 1990) found that the fluoride release from another fluoride-containing adhesive available in the U.K. (Direct®, Orthocare, 5 Oxford Place, Bradford, W Yorkshire BD3 OEF) was 'very small'. A recent clinical study by the author as yet unpublished, also showed no reduction in decalcification, when the same material was compared to a conventional orthodontic bonding resin. Fluoride releasing modules. These have been investigated in an (unpublished) in vitro study by Schemehom and Farnham (1988). The 10 per cent stannous fluoride elastomeric ties showed greater remineralization of adjacent enamel than the 1·4 per cent modules. No clinical data has yet been published.
Management of the Patient with Decalcification During Orthodontic Treatment Despite the clinician's best intentions, the problem of what to do when demineralization occurs in the middle of fixed orthodontic treatment is a very real one. The dilemma is whether to remove the appliance immediately, or to try and achieve a reasonable result in the shortest possible time. Following removal of the appliance, regression of the lesions will occur provided other aetiological factors are favourable. Interestingly, 0gaard et al. ( 1988) warned against treating visible white spots on labial surfaces with concentrated fluoride agents, since this step arrests the lesion. Instead, they advocated allowing remineralization by saliva, as this results in greater repair and a less visible lesion.
204 L. Mitchell
For lesions on other surfaces application of concentrated fluoride was suggested to prevent further progression. The acid pumice abrasion technique developed by Croll and Cavanaugh (1986) has been used successfully to reduce the visible effects of decalcification (Kapila, 1988). This technique involves rubbing a mixture of 18 per cent hydrochloric acid mixed with pumice over the affected enamel and results in removal of the surface layer and an improvement in appearance.
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Conclusions Decalcification during orthodontic treatment with fixed appliances still remains a problem. Although there is much interest in achieving a reduction in enamel susceptibility around an orthodontic attachment, there is, at present, no universal method which is not either expensive in operator time or demanding in terms of patient co-operation. Careful patient selection, together with oral hygiene instruction and dietary advice by an auxiliary at regular intervals throughout treatment remains the most cost-effective approach. References Adrlaens, M. L., Dermaut, L. R. and Verbeeck, R. M. H. (1990) The use of Fluor Protector, a fluoride varnish, as a caries prevention method under orthodontic molar bands, European Jo.urnal of Orthodontics, 12, 316-319. Artun, J. and Brobakken, B. 0. (1986) Prevalence of carious white spots after orthodontic treatment with multibonded appliances, European Journal of Orthodontics, 8, 229-234. Attarzadeh, F. (1986) Water irrigating devices for the orthodontic patient, lnttrnational Journal of Orthodontics, 24, 15-20. Blshara, S. E., Chan, D. and Abadlr, E. A. (1989) The etfeet on the bonding strength of orthodontic brackets of fluoride application after etching, American Journal of Orthodontics and Dentofacial Orthopedics, 95. 259-.260. Blsharli, S. E~. Swift, E. J. and Chan, D. C. N. (1991) Evaluation of fluoride release from an orthodontic bonding system, . American 'Journal of Orthodontics and Dentofacial Orthopedics, 100, 106-=109. Boyd, R. L., Murray, R. and Robertson, P. B. (1989) Effect of rotary electric toothbrush versus manual toothbrush on periodontal status daring orthodontic treatment, American Journal of Orthodontics and Dentofacial Orthopedics, 96, 342-347. Brlghtman, L. J., Terexhalmy, G. T., Greenwell, H., Jacobs, M. and Enlow, D. H. (1991) The effects of a 0·12% chlorhexidine gluconate mouthrinse on orthodontic patients aged 11 through to 17 with established • gingivitis, American Journal of Orthodontics and Dentofacial Orthopedics, 100, 324-329.
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Carlos, J. P. 11985] In: S. H. Y. Wei (ed.) Clinical uses of.fluorides, Lea and Febiger, Philadelphia, 75-82. Casey, G. R. (1988) Maintenance of oral hygiene and dental health during orthodontic therapy, Clinical Preventive Dentistry, 10, 11-13. Chan, D. C. N., Swift, E. J. and Bishara, S. E. (1990) In vitro evaluation of a fluoride releasing orthodontic resin, Journal of Dental Research, 69, 1576-1579. Clanclo, S. G., Cunat, J. J., Mather, M. L. and Harvey, D. H. (1985) A comparison of plaque accumulation in bonded versus banded teeth, Journal of Dental Research, 64, 359 (abstr. 1664). Cook, P. A. (1990) Direct bonding with glass ionomer cement, Journal of Clinical Orthodontics, 14, 509-511. Cook, P.A. and Youngson, C. C. (1988) An in vitro study of the bond strength of a glass ionomer in direct bonding of orthodontic brackets, British Journal of Orthodontics, IS, 247-253. Croll, T. P. and Cavanaugh, R. R. (1986) Hydrochloric acid-pumice enamel surface abrasion for colour modification: results after six months, Quintessence International, 17, 335-343. Durning, P. D. (1989) A clinical and laboratory investigation into the cements used to retain orthodontic bands, M.D.S. thesis, Newcastle University. Fox, N. A. (1990) Fluoride release from orthodontic bonding materials. An in vitro study, British Journal of Orthodontics, 17, 293-298. Geiger, A. M., Gorellck, L., Gwlnnett, A. J. and Griswold, P. G. (1988) The effect of a fluoride program on white spot formation during orthodontic treatment, American Journal of Orthodontics and Dentofacial Orthopedics, 93, 29-37. Gorellck, L., Geiger, A. M. and Gwinnett, A. J. (1982) Incidence of white spot formation after bonding and banding, American Journal of Orthodontics, 81, 83-98. Gwlnnett, A. J. and Ceen, R. F. (1979) Plaque distribution on bonded brackets: A scanning microscope study, American Journal of Orthodontics, 75, 667-677. Hogg, S. D. (1990) Chemical Control of Plaque, Dental Update, 17, 330-333. Jackson, C. L. (1991) Comparison between electric toothbrushing and manual toothbrushing, with and without oral irrigation, for oral hygiene of orthodontic patients, American Journal of Orthodontics and Dentofacial Orthopedics, 99, 15-20. Kaplla, S; (1988) Hydrochloric acid-pumice treatment for post-orthodontic localised decalcification, American Journal of Dentistry, I, 15-19. Levlne, R. S. (1991) Fluoride and caries prevention: I. Scientific rationale, Dental Update, 18, 105-110.
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Low, T., von Fraunhofer, J. A. and Winter, G. B. (197S) The bonding of a polymeric fissure sealant to topical fluoridetreated teeth, Journal of Oral Rehabilitation, 2, 303-307. Lundstriim, F. and Krasse, B. (1987) Streptococcus mutans and lactobacilil frequency in orthodontic patients; the effect of chlorhexidine treatments, European Journal of Orthodontics, 9, 109-116. Lundstrom, F., Hamp, S. E. and Nyman, S. (1980) Systematic plaque control in children undergoing long-term orthodontic treatment, European Journal of Orthodontics, 2, 27-39. Maijer, R. and Smith, D. C. (1988) A comparison between zinc phosphate and glass ionomer cement in orthodontics, American Journal of Orthodontics, 93, 273-279. Meyers, M. J. (1952) Protection of enamel under orthodontic bands, American Journal of Orthodontics, 38, 866-874. Mizrahl, E. (1982) Enamel demineralisation following orthodontic treatment, American Journal of Orthodontics, 82, 63-67. Mizrahi, E. (1983) Surface distribution of enamel opacities following orthodontic treatment, American Journal of Orthodontics, 84, 323-331. Mizrahi, E. (1988) Glass ionomer cements in orthodontics-an update, American Journal of Orthodontics and Dentofacial Orthopedics, 93, 505-507. Murray, J. J. (1989) The Prevention of Dental Disease, Oxford University Press, Oxford. 0gaard, B. (1989) Prevalence of white spot lesions in 19-year-olds: A study on untreated and orthodontically treated persons 5 years after treatment, American Journal of Orthodontics and Dentofacia/ Orthopedics, 96,423-427. 0gaard, B., Rolla, G. and Arends, J. (1988) Orthodontic appliances and enamel demineralisation. Part I. Lesion development. Part 2. Prevention and treatment oflesions, American Journal of Orthodontics and Dentofacial Orthopedics, 94,68-73, 123-128. O'Rellly, M. M. and Featherstone, J. D. B. (198S) De and remineralistion around orthodontic appliances: an in vivo study, A. A. D. R. Abstract No. 1140. Saloum, S. S. and Sondhl, S. (1987) Preventing enamel decalcification after orthodontic treatment, Journal of the American Dental Association, liS, 257-261. &:haeken, M. J. M. and van der Hoeven, J. S. (1989) Effects of varnishes containing chlorhexidine on the human dental plaque flora, Journal of Dental Research, 68, 1786-1789. &:hemehom, B. R. and Farnham, R. (1988) An in vitro incipient lesion study of enamel remineralisation and fluoride bioavailability comparing two orthodontic ties, Indiana University School of Dentistry, OHEI Number R/D 50 (unpublished data).
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Schwaninger, B. and Vickers-Schwaninger, N. (1979) Developing an effective oral hygiene program for the orthodontic patient: Review, rationale and recommendations, American Journal of Orthodontics, 7S, 447-452. Sonis, A. L. and Snell, W. (1989) An evaluation of a fluoride releasing visible light activated bonding system for orthodontic bracket placement, American Journal of Orthodontics and Dentofacial Orthopedics, 9S, 306-311. Stratemann, M. W. and Shannon, I. L. (1974) Control of decalcification in orthodontic patients by daily selfadministered application of a water free 0·4 per cent stannous fluoride gel, American Journal of Orthodontics, 66, 273-279. Thornton, J. B. (1986) The effect of fluoride in phosphoric acid on enamel fluoride uptake and the tensile bond strength of an orthodontic bonding resin, American Journal of Orthodontics and Dentofacial Orthopedics, 90,91-101. Tillery, T. J., Timbree, J. H. and Webster, F. N. (1976) Preventing enamel decalcification during orthodontic treatment, American Journal of Orthodontics, 70, 435-439. Underwood, M. L., Rawls, H. R. and Zimmerman, B. F. (1989) Clinical evaluation of a fluoride-exchanging resin as an orthodontic adhesive, American Journal of Orthodontics and Dentofacial Orthopedics, 96,93-99. Valk, J. W. P. and Davidson, C. L. (1987) The relevance of controlled fluoride release with bonded orthodontic appliances, Journal of Dentistry, IS, 257-260. Wang, W. N. and Sheen, D. 11. (1991) The effect of pretreatment with fluoride on the tensile strength of orthodontic bonding, Angle Orthodontist, 61, 31-34. Williams, P., Fenwlck, A., Schou, L. and Adams, W. (1987) A clinical trial of an orthodontic toothbrush, European Journal of Orthodontics, 9, 295-304. Wlsth, P. J. and Nord, A. (1977) Caries experience in orthodonically treated individuals, Angle Orthodontist, 47, 59-64. Younis, D., Hughes, D. 0. and Weber, F. N. (1979) Enamel decalcification in orthodontic treatment, American Journal of Orthodontics, 75, 678-681. Zachrisson, B. U. (1975a). Fluoride application procedures in orthodontic practice, current concepts, Angle Orthodontist, 45, 72-81. Zachrisson, B. U. (1975b) Cause and prevention of injuries to teeth and supporting structures during orthodontic treatment, American Journal of Orthodontics, 69, 285-300. Zachrisson, B. U. (1977) Direct bonding in orthodontics, American Journal of Orthodontics, 71, 173-189. Zachrisson, B. U. and Zachrlsson, S. (1971) Caries incidence and oral hygiene during orthodontic treatment, Scandanavian Journal of Dental Research, 79, 394-401.
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Decalcification During Orthodontic Treatment With Fixed Appliances—An Overview L. Mitchell B.D.S., F.D.S., M.D.S., D.Orth., M.Orth To cite this article: L. Mitchell B.D.S., F.D.S., M.D.S., D.Orth., M.Orth (1992) Decalcification During Orthodontic Treatment With Fixed Appliances—An Overview, British Journal of Orthodontics, 19:3, 199-205, DOI: 10.1179/bjo.19.3.199 To link to this article: http://dx.doi.org/10.1179/bjo.19.3.199
Published online: 21 Jun 2016.
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British Journal of Orthodontics/ Vol. 19/1992/199-205
Decalcification During Orthodontic Treatment With Fixed Appliances-An Overview L. MITCHELL, B.D.S., F.D.S., M.D.S., D.ORTH., M. 0RTH Department of Orthodontics, The Dental School, Framlington Place, Newcastle upon Tyne NE4 48W Received for publication June 1991
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A~stract. The prevalence and aetiology ofdecalcification during orthodontic treatment with fixed appliances is dtscussed and consideration given to the methods of reducing this problem.
Index words: Decalcification, Fixed Appliances.
Introduction Decalcification is defined as loss of calcified tooth substance, and it occurs when the pH of the oral environment favours diffusion of calcium and phosphate ions out of the enamel. This dissolution follows the production of acid by bacterial plaque and results in an altered appearance of the tooth sur~ace. The early lesion is an opaque white spot, W~Ich in active lesions appears chalky, and if mmeralloss continues, frank cavitation may result. An accumulation of bacterial plaque and a supply of fermentable sugars are the prerequisites for decalcification to occur. Unfortunately, fixed orthodontic appliances hinder tooth cleaning, and favour plaque and food retention. A rise in the numbers of Streptococcus mutans and lactobacilli has been reported following the placement of orthodontic appliances (Lundstrom and Krasse, 1987). These micro-organisms are associated with the initiation of dental caries and further development of the carious lesion, respectively, and their presence increases the risk of decalcification occurring (Schwaninger and Vickers-Schwaninger, 1979).
Prevalence Ea~ly studies in this field investigated the overall canes experience of orthodontic patients and found that although the total number of carious lesions in this group did not differ significantly from untreated individuals, a greater proportion of buccal and lingual surface lesions were seen (Wisth and Nord, 1977). Subsequent workers have attempted 0301-22X/92/008000 + OOS02.00
to quantify the extent of the risk posed by decalcification during orthodontic treatment (Table 1). The prevalence reported among patients ranges from 2 to 96 per cent. This large variation is due to the variety of methods used to assess and score the presence of decalcification, whether idiopathic enamellucencies were included or excluded, and the use or otherwise of a fluoride regime during treatment. In a cross-sectional study design (orthodontic patients after treatment compared with another group of patients who have not had orthodontics) it is difficult to distinguish between idiopathic white spots and decalcification, which artificially increases the prevalence quoted. Zachrisson and Zachrisson ( 1971 ), and Zachrisson ( 1977) employed a longitudinal design and recorded only new white spots developing, yet despite this, the prevalences they found were 89 and 15 per cent, respectively. Surprisingly, only Stratemann and Shannon (1974), and Mizrahi (1982, 1983) used photographs to back up their clinical assessment. The results are more encouraging where the prevalence for teeth is quoted, as the results ranged from 0 to 24 per cent. The distribution of affected teeth has been studied by several workers. Gorelick et al. ( 1982) found maxillary incisors and mandibular first molars to be the teeth with the highest prevalence. Mizrahi (1983) found maxillary incisors and first molars to be most commonly affected. He also reported that the enamel opacities were found particularly on the cervical and middle thirds of the vestibular surface of affected teeth. 0gaard (1989) also found the first permanent molars in both arches to have the highest prevalence. In contrast, Geiger et al. (1988) reported that lesions occurred most frequently on © 1992 British Society ror the Study or Orthodontics
200 L. Mitchell
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TABLE I Studies into the prevalence of decalcification during fixed orthodontic treatment (whole mouth studies only)
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Comments
5·8% test teeth 23·8% control teeth
Test teeth treated with varnish prior to band placement
89% patients
Fluoride mouthrinse used during ortho.
58% of patients without fluoride 2% of patients on fluoride regime 15% patients
Comparison of prevalence in orthodontic patients with or without fluoride gel regime Fluoride mouthrinse used during ortho.
Design
Meyers 1952
Longitudinal Direct visual assessment
Zachrisson and Zachrisson (1971)
Longitudinal Direct visual assessment Direct visual assessment with photos
Caries ind~x (Fehr, 1961)
Zachrisson (1977)
Longitudinal Direct visual assessment
Gore lick et al. (1982)
Direct visual assessment at end of treatment
'New white spots' noted Presence (and severity) or absence of white spots
Mizrahi (1982, 1983)
Cross-sectional Direct visual assessment. In small sub-group photos used as well
Scored white opacities (after Curzon and Spector (1975))
Artun and Brobakken (1986)
Cross-sectional. Direct visual assessment
59% of patients Caries Index and Gorelick's after ortho. 45% of patients not Index requiring ortho.
Fluoride mouthrinse used during ortho.
Geiger et al. (1988)
Gorelick et al. ( 1972) used as baseline. Direct visual assessment Cross-sectional. Direct visual assessment
Gore lick's Index
34% of patients. 7·5% of teeth
Fluoride programme.
Gorelick's Index
95% of patients 5-7 years after ortho. 85% non-orthodontic controls.
Fluoride mouthrinse used during ortho.
After Mizrahi (1982)
13"/c, of teeth with Comparison of 2 adhesives conventional adhesive with and without fluoride. 0% of teeth with Fluoride adhesive
Stratemann and Shannon (1974)
0gaard (1989)
Sonis and Snell (1989) Scored at end of treatment by direct visual assessment
Index used
Prevalence
Author
maxillary lateral incisors and canines, and on mandibular premolars. In the studies by Meyers (1952), Zachrisson and z,achrisson (1971), Stratemann and Shannon (1974), and Mizrahi (1983, 1988) only bands were used, whereas in the remaining studies bonds were used on the anterior teeth. From Table I, it would appear that the method used to assess and score either the presence or absence of decalcification has a greater effect upon the prevalence noted, than the use of bands or bonded attachments. There has been considerable debate in the literature on the effect upon the enamel of the material used to cement orthodontic bands, particularly in relation to zinc phosphate cement. However, Durning (1989) in a comprehensive review of the problem, concluded that enamel surface • changes beneath orthodontic bands are due to a loss of integrity of the cement lute followed by accumu-
50% patients 11"1.. teeth
84% of patients after ortho. 72% of patients prior to ortho.
lation of oral fluids or bacteria in the space, which allows destructive processes to progress undetected. Aetiology
The inter-dependence of bacteria, sugar, enamel, and time in the aetiology of caries is well accepted (Murray, 1989), however, a number of factors can predispose to decalcification or increase its risk during orthodontic treatment, and these are considered briefly below. Oral hygiene
The presence of orthodontic attachments make tooth cleaning more difficult, and predispose to a build-up of plaque on the tooth surface around the attachment, and between it and the gingival margin (Ciancio et al., 1985). Streptococcus mutans and
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Decalcification during Treatment with Fixed Appliances
201
lactobacilli are associated with the initiation and development of caries and especially colonize tooth sites described as retentive (Lundstrom and Krasse, 1987). In addition, a layer of plaque on an enamel surface not only provides a source of acid production in the presence of a sugary substrate, but also acts as a physical barrier limiting the diffusion of acid away from the tooth surface, and preventing remineralization from calcium and phosphate ions in the saliva. Given these factors it is not surprising that decalcification is particularly associated with those areas where plaque accumulation occurs in the orthodontic patient (Saloum and Sondhi, 1987).
Careful consideration should be given to the design of bonded retainers as those too can hinder tooth cleaning. Bonding technique
The presence of adhesive 'flash' around a bonded orthodontic attachment can predispose to plaque accumulation (Gwinnett and Ceen, 1979), therefore, any excess should be cleared away before the adhesive cures. Methods of Reducing Decalcification During Fixed Orthodontic Treatment
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Diet
The role of fermentable carbohydrate in caries has been well documented (Murray, 1989). Frequent consumption of sugary foods or drinks has been shown to be most damaging, as following sugar intake the pH of plaque drops below the critical level of 5·5 for about 20 minutes. In addition, fixed appliances restrict the ability of the tongue and saliva to remove food particles from the mouth, with the result that breakdown of more complex carbohydrates gives rise to a prolonged acid challenge to the tooth surface. Appliance type and design
Generally, as the proportion of tooth surface covered by an orthodontic bracket increases, the more difficult it becomes for the patient to effectively clean the remaining uncovered enamel. However, this does not mean that using bands rather than bonded attachments is more likely to result in decalcification. In practice, a well cemented band appears to be protective of the tooth surface it covers, although should the cement lute fail, extensive demineralization can occur if the band is left in situ for any length of time (Zachrisson, l975b). In their study Gore lick et al. ( 1982), found no difference in the prevalence of white spot lesions in bonded or banded teeth. However, the site of plaque accumulation does differ between bonds and bands, with the latter favouring the development of plaque around the gingival margin (Ciancio et al., 1985) with an increase in the potential for loss of periodontal support. Archwire design will also affect the accumulation of plaque and food debris. One of the major disadvantages of the Begg appliance is the difficulty patients experience cleaning around the looped archwires and auxiliaries. However, the use of elastic thread or chain and other auxiliaries with any technique will make cleaning more difficult.
Patient selection and education
Most operators insist on a patient attammg a certain level of oral cleanliness before embarking on orthodontic treatment. However, there will always be a proportion of patients whose ability to clean their teeth deteriorates as treatment progresses. Remotivation and education of the patient in the importance of diet and tooth cleaning throughout treatment, ideally by a hygienist, can help to reduce this problem, but will not eliminate it. Lundstrom and Krasse ( 1987) have suggested using microbial monitoring to identify those patients most at risk of decalcification, as evidenced by high salivary Streptococus mutans and lactobacilli counts, and targeting them. Oral hygiene instruction
Although professional oral hygiene instruction for the duration of treatment has been shown to be effective in reducing decalcification (Artun and Brobakken, 1986), this approach is very labour intensive and costly. However, periodic re-inforcement by a professional can help to remotivate a patient and correct any errors in technique (Lundstrom et al., 1980). Bacterial plaque can be removed mechanically and/or chemically. Mechanical plaque removal. There is now an almost bewildering array of toothbrushes and cleaning aids available to the public. Some manufacturers even produce special orthodontic toothbrushes with a groove along the length of the head designed to fit over the brackets and archwire. There appears to be little hard evidence to support the contention that any type or design of toothbrush, or any toothbrushing technique is superior to another (Williams et al., 1987). However, toothbrushing twice daily with a conventional or othodontic brush should be supplemented by an
202
L. Mitchell
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interdental cleaning aid, e.g. a single tufted toothbrush, to clean between the teeth and under the archwire (Casey, 1988), and patients must be informed that it will take longer to clean effectively around a fixed appliance, than before orthodontic treatment. Electric toothbrushes and oral irrigation systems are heavily promoted by their manufacturers. The results of studies which have examined the effectiveness of an electric over a manual toothbrush for orthodontic patients are equivocal (Boyd et al., 1989; Jackson, 1991). However, Attarzadeh, (1986) suggested that oral irrigation should only be .used as an adjunct to other methods of tooth cleamng. Chemical plaque removal. It has been postulated that to be effective a chemical plaque remover must be capable of reducing the oral flora by 99·9 per cent (Hogg, 1990). In addition, the agent must not upset the balance of the oral microflora or promote resistant micro-organisms and be non-toxic. Given these stringent requirements it is surprising that any product has been developed as a chemical antiplaque agent. Nevertheless, a number of proprietary antiseptics are now available which claim to be active against plaque bacteria. Of these chlorhexidine is the most effective, due to its absorption onto the acquired pellicle, which prolongs its presence and effect in the mouth (Hogg, 1990). Chlorhexidine is not without its disadvantages, the most pertinent to orthodontics being the deposition of a brown stain. However, this staining is readily removed, albeit not until the end of active appliance therapy (Brightman et al., 1991). A recent study by Lundstrom and Krasse (1987), looked at the effect of chemical control (with chlorhexidine) of the numbers of Streptococus mutans in patients undergoing fixed orthodontic treatment. The subjects were selected for the study because of their initial high levels of Streptococcus 11)Utans (and associated high risk of decalcification), ano all received oral hygiene instruction, dietary advice, and topical fluoride, in addition to the application of chlorhexidine gel. The authors found that the chlorhexidine treatment had an additional preventive effect, but felt the gain was small, and did not justify the time and cost involved. Reducing plaque retention by the appliance
Selection of small brackets and their use with a careful technique involving removal of any composite flash, minimal use of looped archwires, and periodic checking of the cement Jute under bands, will help to reduce plaque accumulation by the appliance and decalcification.
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Protecting the enamel surface around attachments
Attempts at reducing the susceptibility of enamel to surface change have centred around two approaches. The first is directed at strengthening the enamel and reducing its acid solubility-that is, the use of topical fluoride agents before, during, and after orthodontic treatment. This approach is considered in more detail in the section entitled 'Fluoride' below. The other method involves protecting the surface of the tooth around and beneath the orthodontic attachment with a protective coating and a number of materials have been investigated. A polymer adhesive Protecto® (Lee Pharmaceuticals, South El Monte, California 91733) was used successfully by Tillery et al. ( 1976) to reduce decalcification under othodontic bands, but a subsequent study by Younis et al. (1979) found NuvaseaJ® (LD Caulk Division of the Amalgamated Dental Company, London), a fissure sealing material, to be more effective than Protecto. Painting sealant resin around orthodontic bonds has also been suggested, but oxygen inhibition of polymerisation limits the protection that is afforded (Saloum and Sondhi, 1987). A varnish containing 45 per cent chlorhexidine was found to reduce the numbers of Streptococus mutans 10-fold, locally, 22 weeks after a single application to the occlusal fissures of test teeth (Schaeken et al., 1989). Whether this varnish could provide a protective coating around orthodontic bonded attachments remains speculative, but is worthy of investigation. Fluoride
Post-eruptively fluoride can reduce caries by: ( 1) acting as a type of catalyst favouring the formation of high quality hydroxyapatite; (2) by aiding remineralisation during pH fluctuations; (3) by inhibiting glycolysis of plaque bacteria ( Levine, 1991 ). Almost all patients use a fluoridated toothpaste and for many this will suffice; however, for susceptible patients a number of different approaches have been employed to increase the availability of fluoride ions around fixed orthodontic attachments. Mouth-rinsing. Daily rinsing with a 0·5 per cent sodium fluoride solution has been shown to be effective at reducing the prevalence of decalcification during orthodontic treatment (Zachrisson, 1975a; Saloum and Sondhi, 1987). A number of other fluoride compounds have also been investi-
BJO August 1992
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gated, e.g. stannous fluoride, acidulated phosphate fluoride, but they appear to be no more effective than sodium fluoride (Carlos, 1985). The drawback to this approach is that those patients who would most benefit from topical fluoride are the least likely to comply with a regular rinsing regime. Professionally applied fluoride. Several investigators have advocated the application of topical fluoride before etching (Saloum and Sondhi, 1987); however, it has been shown that the bond strength between fissure sealant resin and enamel is reduced following a fluoride pre-etching treatment (Low et al., 1975). Interestingly, a recent study by Wang and Sheen (1991) using the technique prior to placing orthodontic bonds found no significant effect upon bond strength, but reported that enamel detachment during de-bonding was a potential complication. This problem was not reported in an in vitro study of sodium fluoride application, after etching, which also found no significant effect upon bond strength (Bishara et al., 1989). Only one study has examined the effect of fluoride varnish applied prior to placement of orthodontic bands (Adriaens et al., 1990). A polyurethane varnish containing 0·7 per cent fluoride was used in vivo and was found to significantly reduce decalcification under well fitting bands. Professional fluoride gel applications during orthodontic treatment are of proven efficacy (Zachrisson, 1975b; O'Reilly and Featherstone, 1985), but like professional tooth cleaning are expensive of operator time. Fluoride containing etchant. An in vitro study by Thornton (1986) concluded that the addition of fluoride to phosphoric acid etchant had little or no protective effect, which perhaps is not surprising given that etchant dissolves the enamel surface and is then rinsed away. Fluoride containing cements for banding. The development of fluoride containing cements for placing orthodontic bands has been extensively reviewed by Durning (1989). Interest now focuses on the polyalkenoate cements which have been shown clinically to be associated with less decalcification than zinc phosphate or zinc polyacrylate (Maijer and Smith, 1988; Mizrahi, 1988; Durning, 1989). Whether this is due to the increased fluoride content of glass ionomer cements per se, or their increased adhesion and better band retention, is still controversial. Fluoride containing bonding adhesives. Interest currently centres around two different types of fluoride containing material for attaching ortho-
Decalcification during Treatment with Fixed Appliances
203
dontic brackets. These are glass ionomer and composite resin to which fluoride has been added. An in vitro study (Valk and Davidson, 1987) indicated that glass ionomer cement protected the enamel beneath and also I mm around an orthodontic attachment, from decalcification. However, glass ionomer has been shown to have a weaker bond strength than composite (Cook and Youngson, 1988). Despite this, adequate retention has been reported clinically by Cook ( 1990) in 40 consecutive cases. The results of the studies by Sonis and Snell (1989), and Underwood et al. (1989) in America into the clinical durability and caries inhibition potential of fluoride releasing composite resins were encouraging, although a subsequent study (Chan et al., 1990) into the light-activated material used by Sonis and Snell reported that its tensile bond strength was significantly less than a conventional resin. However, Bishara et al. ( 1991) concluded that this was due to inadequate polymerization, rather than the addition of sodium fluoride. An in vivo investigation by Fox ( 1990) found that the fluoride release from another fluoride-containing adhesive available in the U.K. (Direct®, Orthocare, 5 Oxford Place, Bradford, W Yorkshire BD3 OEF) was 'very small'. A recent clinical study by the author as yet unpublished, also showed no reduction in decalcification, when the same material was compared to a conventional orthodontic bonding resin. Fluoride releasing modules. These have been investigated in an (unpublished) in vitro study by Schemehom and Farnham (1988). The 10 per cent stannous fluoride elastomeric ties showed greater remineralization of adjacent enamel than the 1·4 per cent modules. No clinical data has yet been published.
Management of the Patient with Decalcification During Orthodontic Treatment Despite the clinician's best intentions, the problem of what to do when demineralization occurs in the middle of fixed orthodontic treatment is a very real one. The dilemma is whether to remove the appliance immediately, or to try and achieve a reasonable result in the shortest possible time. Following removal of the appliance, regression of the lesions will occur provided other aetiological factors are favourable. Interestingly, 0gaard et al. ( 1988) warned against treating visible white spots on labial surfaces with concentrated fluoride agents, since this step arrests the lesion. Instead, they advocated allowing remineralization by saliva, as this results in greater repair and a less visible lesion.
204 L. Mitchell
For lesions on other surfaces application of concentrated fluoride was suggested to prevent further progression. The acid pumice abrasion technique developed by Croll and Cavanaugh (1986) has been used successfully to reduce the visible effects of decalcification (Kapila, 1988). This technique involves rubbing a mixture of 18 per cent hydrochloric acid mixed with pumice over the affected enamel and results in removal of the surface layer and an improvement in appearance.
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Conclusions Decalcification during orthodontic treatment with fixed appliances still remains a problem. Although there is much interest in achieving a reduction in enamel susceptibility around an orthodontic attachment, there is, at present, no universal method which is not either expensive in operator time or demanding in terms of patient co-operation. Careful patient selection, together with oral hygiene instruction and dietary advice by an auxiliary at regular intervals throughout treatment remains the most cost-effective approach. References Adrlaens, M. L., Dermaut, L. R. and Verbeeck, R. M. H. (1990) The use of Fluor Protector, a fluoride varnish, as a caries prevention method under orthodontic molar bands, European Jo.urnal of Orthodontics, 12, 316-319. Artun, J. and Brobakken, B. 0. (1986) Prevalence of carious white spots after orthodontic treatment with multibonded appliances, European Journal of Orthodontics, 8, 229-234. Attarzadeh, F. (1986) Water irrigating devices for the orthodontic patient, lnttrnational Journal of Orthodontics, 24, 15-20. Blshara, S. E., Chan, D. and Abadlr, E. A. (1989) The etfeet on the bonding strength of orthodontic brackets of fluoride application after etching, American Journal of Orthodontics and Dentofacial Orthopedics, 95. 259-.260. Blsharli, S. E~. Swift, E. J. and Chan, D. C. N. (1991) Evaluation of fluoride release from an orthodontic bonding system, . American 'Journal of Orthodontics and Dentofacial Orthopedics, 100, 106-=109. Boyd, R. L., Murray, R. and Robertson, P. B. (1989) Effect of rotary electric toothbrush versus manual toothbrush on periodontal status daring orthodontic treatment, American Journal of Orthodontics and Dentofacial Orthopedics, 96, 342-347. Brlghtman, L. J., Terexhalmy, G. T., Greenwell, H., Jacobs, M. and Enlow, D. H. (1991) The effects of a 0·12% chlorhexidine gluconate mouthrinse on orthodontic patients aged 11 through to 17 with established • gingivitis, American Journal of Orthodontics and Dentofacial Orthopedics, 100, 324-329.
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Carlos, J. P. 11985] In: S. H. Y. Wei (ed.) Clinical uses of.fluorides, Lea and Febiger, Philadelphia, 75-82. Casey, G. R. (1988) Maintenance of oral hygiene and dental health during orthodontic therapy, Clinical Preventive Dentistry, 10, 11-13. Chan, D. C. N., Swift, E. J. and Bishara, S. E. (1990) In vitro evaluation of a fluoride releasing orthodontic resin, Journal of Dental Research, 69, 1576-1579. Clanclo, S. G., Cunat, J. J., Mather, M. L. and Harvey, D. H. (1985) A comparison of plaque accumulation in bonded versus banded teeth, Journal of Dental Research, 64, 359 (abstr. 1664). Cook, P. A. (1990) Direct bonding with glass ionomer cement, Journal of Clinical Orthodontics, 14, 509-511. Cook, P.A. and Youngson, C. C. (1988) An in vitro study of the bond strength of a glass ionomer in direct bonding of orthodontic brackets, British Journal of Orthodontics, IS, 247-253. Croll, T. P. and Cavanaugh, R. R. (1986) Hydrochloric acid-pumice enamel surface abrasion for colour modification: results after six months, Quintessence International, 17, 335-343. Durning, P. D. (1989) A clinical and laboratory investigation into the cements used to retain orthodontic bands, M.D.S. thesis, Newcastle University. Fox, N. A. (1990) Fluoride release from orthodontic bonding materials. An in vitro study, British Journal of Orthodontics, 17, 293-298. Geiger, A. M., Gorellck, L., Gwlnnett, A. J. and Griswold, P. G. (1988) The effect of a fluoride program on white spot formation during orthodontic treatment, American Journal of Orthodontics and Dentofacial Orthopedics, 93, 29-37. Gorellck, L., Geiger, A. M. and Gwinnett, A. J. (1982) Incidence of white spot formation after bonding and banding, American Journal of Orthodontics, 81, 83-98. Gwlnnett, A. J. and Ceen, R. F. (1979) Plaque distribution on bonded brackets: A scanning microscope study, American Journal of Orthodontics, 75, 667-677. Hogg, S. D. (1990) Chemical Control of Plaque, Dental Update, 17, 330-333. Jackson, C. L. (1991) Comparison between electric toothbrushing and manual toothbrushing, with and without oral irrigation, for oral hygiene of orthodontic patients, American Journal of Orthodontics and Dentofacial Orthopedics, 99, 15-20. Kaplla, S; (1988) Hydrochloric acid-pumice treatment for post-orthodontic localised decalcification, American Journal of Dentistry, I, 15-19. Levlne, R. S. (1991) Fluoride and caries prevention: I. Scientific rationale, Dental Update, 18, 105-110.
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Schwaninger, B. and Vickers-Schwaninger, N. (1979) Developing an effective oral hygiene program for the orthodontic patient: Review, rationale and recommendations, American Journal of Orthodontics, 7S, 447-452. Sonis, A. L. and Snell, W. (1989) An evaluation of a fluoride releasing visible light activated bonding system for orthodontic bracket placement, American Journal of Orthodontics and Dentofacial Orthopedics, 9S, 306-311. Stratemann, M. W. and Shannon, I. L. (1974) Control of decalcification in orthodontic patients by daily selfadministered application of a water free 0·4 per cent stannous fluoride gel, American Journal of Orthodontics, 66, 273-279. Thornton, J. B. (1986) The effect of fluoride in phosphoric acid on enamel fluoride uptake and the tensile bond strength of an orthodontic bonding resin, American Journal of Orthodontics and Dentofacial Orthopedics, 90,91-101. Tillery, T. J., Timbree, J. H. and Webster, F. N. (1976) Preventing enamel decalcification during orthodontic treatment, American Journal of Orthodontics, 70, 435-439. Underwood, M. L., Rawls, H. R. and Zimmerman, B. F. (1989) Clinical evaluation of a fluoride-exchanging resin as an orthodontic adhesive, American Journal of Orthodontics and Dentofacial Orthopedics, 96,93-99. Valk, J. W. P. and Davidson, C. L. (1987) The relevance of controlled fluoride release with bonded orthodontic appliances, Journal of Dentistry, IS, 257-260. Wang, W. N. and Sheen, D. 11. (1991) The effect of pretreatment with fluoride on the tensile strength of orthodontic bonding, Angle Orthodontist, 61, 31-34. Williams, P., Fenwlck, A., Schou, L. and Adams, W. (1987) A clinical trial of an orthodontic toothbrush, European Journal of Orthodontics, 9, 295-304. Wlsth, P. J. and Nord, A. (1977) Caries experience in orthodonically treated individuals, Angle Orthodontist, 47, 59-64. Younis, D., Hughes, D. 0. and Weber, F. N. (1979) Enamel decalcification in orthodontic treatment, American Journal of Orthodontics, 75, 678-681. Zachrisson, B. U. (1975a). Fluoride application procedures in orthodontic practice, current concepts, Angle Orthodontist, 45, 72-81. Zachrisson, B. U. (1975b) Cause and prevention of injuries to teeth and supporting structures during orthodontic treatment, American Journal of Orthodontics, 69, 285-300. Zachrisson, B. U. (1977) Direct bonding in orthodontics, American Journal of Orthodontics, 71, 173-189. Zachrisson, B. U. and Zachrlsson, S. (1971) Caries incidence and oral hygiene during orthodontic treatment, Scandanavian Journal of Dental Research, 79, 394-401.
