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A longitudinal laser fluorescence study of white spot lesions in orthodontic patients
American Journal of ORTHODONTICS and DENTOFACIAL ORTHOPEDICS Founded in 1915
Volume 113 Number 6
June 1998
Copyright © 1998 by the American Association of Orthodontists
ORIGINAL ARTICLE
A longitudinal laser fluorescence study of white spot lesions in orthodontic patients Susan AI-Khateeb, DDS,a Carl-Magnus Forsberg, DDS, PhD,b Elbert de Josselin de Jong, MSc, PhD,c and Birgit Angmar-Månsson, DDS, PhDd Huddinge, Sweden, and Amsterdam, The Netherlands Orthodontic treatment with fixed appliances increases the caries risk in young persons. The aim of this study was to apply a new caries diagnostic method, quantitative laser fluorescence, for longitudinal in vivo quantification of changes in incipient enamel lesions related to fixed orthodontic appliances. Seven young patients with active caries lesions disclosed at removal of the orthodontic brackets and bands were enrolled in the study. Caries preventive measures were intensified, including dietary advice, oral hygiene instructions, and the regular use of a fluoride dentifrice. The caries lesions were monitored with the quantitative laser fluorescence method after removal of the brackets and once a month thereafter. For each lesion, three quantities were measured: lesion area (mm2), mean fluorescence loss (%) over the lesion, and maximum loss of fluorescence (%) in the lesion. During a 1-year follow-up period, the areas of the lesions decreased and the enamel fluorescence lost was partly regained indicating that a remineralization process had occurred. It was concluded that quantitative laser fluorescence seems suitable for in vivo monitoring of mineral changes in incipient enamel lesions, and useful for the evaluation of preventive measures in caries prone persons, such as orthodontic patients. (Am J Orthod Dentofacial Orthop 1998;113:595-602)
E
namel demineralization with white spot formation on buccal surfaces of teeth is a relatively common side effect from orthodontic treatment with fixed appliances.1-3 Treatment with fixed appliances makes conventional oral hygiene for plaque removal more difficult, thus increasing the cariogenic challenge on surfaces that normally show a low prevalence of dental caries.4 White spot formation has been attributed to the effect of prolonged accumulation and retention of the bacterial plaque on enamel surfaces adjacent to the appliances. There is evidence, however, that suggests that such small areas of superficial enamel demineralization may remineralize.6,7 From Karolinska Institutet. a Departments of Cariology and Orthodontics. b Associate Professor, Department of Orthodontics. c Inspektor Research Systems BV. d Professor and chair, Department of Cariology. Reprint requests to: Susan Al-Khateeb, Department of Cariology, Faculty of Odontology, Karolinska Institutet, P.O. Box 4064, SE-141 04 Huddinge, Sweden. E-mail: [email protected] Copyright © 1998 by the American Association of Orthodontists. 0889-5406/98/$5.00 1 0 8/1/83878
Sensitive methods that enable early detection and quantification of caries lesions make it possible to monitor changes in the enamel over time. Laser light induced fluorescence as a diagnostic method for detection of enamel caries at an early stage was introduced in 1982.8 When the tooth is illuminated with a broad beam of bluegreen laser light (488 nm) according to this method, enamel autofluorescence occurs in the yellow region of the light spectrum and may be observed through a yellow high pass filter9 that excludes the tooth scattered blue laser light. When enamel demineralization takes place, minerals will be replaced mainly by water causing a decrease in the light path in the tooth substance. This will result in reduction of light absorption by enamel.10 Because fluorescence is a result of absorption, the intensity of fluorescence will decrease in demineralized regions of the enamel, which appear darker than the sound tooth structure.11,12 A quantitative version of the laser fluorescence method (QLF) has been tested for assessment of mineral changes in artificial lesions during demineralization in vitro,13 during remineralization in situ,14 595
596 Al-Khateeb et al.
and for assessment of mineral loss in natural incipient caries lesions in human enamel from a single measurement.15 These studies have indicated that changes in mineral contents of enamel lesions may be accurately recorded with the QLF method. Furthermore, transverse microradiography has been used to validate data obtained by the QLF method,14,16,17 and these studies have shown that there is a strong correlation between the two methods. This suggests that it should also be possible to calculate the lesion depth from the fluorescence loss value. The result of such a calculation, however, would be only an approximation of the lesion depth because the microradiographic method permits quantification of mineral content in thin sections obtained from the middle of the lesions, whereas the QLF method gives information about mineral loss over the whole lesion. The QLF method has undergone further development for in vivo quantification of mineral loss in natural enamel lesions with the use of a CCD micro video camera and computerized image analysis.18 The aim of the present study was to use the laser fluorescence method to quantitatively and longitudinally assess the changes in white spot lesions that had been formed around orthodontic bands and brackets in vivo. MATERIAL AND METHODS Patients This study was carried out on seven adolescents, aged 13-15 years, who exhibited white spot lesions. They were chosen from a number of patients who had just finished their orthodontic treatment with full fixed appliances (standard edgewise technique). The average treatment time was 2 years. After removal of the appliances, the patients were found to have 15 teeth with white spot lesions (10 first molars, 3 premolars, and 2 canines). Four of the affected molars had been banded with glass ionomer cement. The other molars had been bonded with buccal tubes using standard orthodontic bonding material. The premolars and the canines had been bonded with brackets. Enamel fluorescence images of the affected teeth were recorded just after debanding and debonding. Subsequent recordings were made monthly over a 1-year period. At each visit, three images were produced for each tooth. When the images were analyzed and the fluorescence loss and the size of the lesion areas were calculated, the mean values of the data obtained from the three recordings were used. Instructions about dietary habits and efficient oral hygiene including fluoride (F) toothpaste were given to the patients during the orthodontic treatment and during the study. The patients were provided with F toothpaste (Pepsodent Super Fluor, 0.145% F, Elida Robert, Stock-
American Journal of Orthodontics and Dentofacial Orthopedics June 1998
holm, Sweden) to be used twice a day throughout the investigation period. The study was approved by the Ethical Committee at Huddinge Hospital, and all patients gave their informed consent before the study. Measuring equipment A color CCD micro video camera (Panasonic WV-KS 152) equipped with a 15 mm focal-length lens was used to record the fluorescence images.18 The tooth surfaces were illuminated by blue-green light from an argon ion laser source (l 5 488 nm, 10 to 20 mW z cm–2). In order to exclude the tooth-scattered laser light and enable detection of the autofluorescence emitted by enamel, a yellow high pass filter (Hoya O-54) was placed in front of the camera to cut off light with a wave length less than 540 nm. The CCD camera viewed and recorded the fluorescence images through a dental mirror, as demonstrated in Fig. 1. The images were stored in a computer, processed, and analyzed by custom-made software (QLF 1.92, Inspektor Research Systems BV, Amsterdam, The Netherlands). Fig. 2 left shows the clinical image of a white spot lesion as it appears on the computer screen, and Fig. 2 right shows the laser fluorescence image of the same lesion. To calculate the fluorescence loss in the lesion in relation to sound enamel, the program reconstructed the fluorescence radiance (L, expressed in [W/m2.sr] 5 power per area per solid angle) at the lesion site from the fluorescence radiance of the surrounding sound enamel, which was assumed to be 100%. The difference between the reconstructed and the actual fluorescence radiance (DL) represented the fluorescence loss at the lesion site as demonstrated in Fig. 3. Three quantities were measured: the mean fluorescence loss over the lesion (DLmean/L in %), maximum fluorescence loss (DLmax/L in %), and lesion area (defined as the area [mm2] where fluorescence loss is $5%). Statistical analysis The paired Student’s t test was used to compare the fluorescence loss and the size of the lesion areas at the beginning of the study and 1 year later. The level of significance was chosen as p , 0.05. On studying the probability distribution of the recorded quantities, one variable was found to be slightly skewed: the DLmean/L showed a tendency toward positive skewness (1.664, p , 0.05). It is usually not appropriate to apply the t test to variables that depart from normality. In cases of minor skewness, however, and when the size of the sample is adequate, the t test may still provide an acceptable approximation of the true degree of difference between the two measurements. RESULTS
During the 1-year period of study, the fluorescence radiance in the enamel lesions increased indicating a mineral gain, and the lesion areas of
American Journal of Orthodontics and Dentofacial Orthopedics Volume 113, No. 6
Al-Khateeb et al. 597
Fig. 1. Schematic presentation of quantitative laser fluorescence set-up.
almost all white spots had decreased. The differences between the base-line and final values for Dmean/L and DLmax/L were highly significant, p 5 0.001, and p , 0.001, respectively (Table I). The mean area of the lesions was reduced at the end of the study (p , 0.01, Table II). Fig. 4A and B show the visual changes in the fluorescence images over time in two of the lesions (lower left first molar in subject B and lower left second premolar in subject D, respectively), i.e., less darkness at the lesion sites by the end of the study period. The quantitative data for the parameters Dmean/L, DLmax/L, and area of the lesion in Fig. 4A are presented as a function of time in Fig. 5A, B, and C, respectively. Data from the lower right canine (patient F) were excluded from the statistical analyses. Part of the lesion was obscured by inflamed and edematous gingiva at the baseline recording that was taken immediately after debonding. Thus, the data obtained for that lesion were not comparable at the two time points. DISCUSSION
Results of previous follow-up studies of white spot lesions have suggested that remineralization
Fig. 2. Left, shows clinical view of a buccal surface with an enamel white spot lesion illuminated with ordinary white light as presented on computer screen. Right, clinical laser fluorescence image of same lesion. Demineralized areas appear dark in laser fluorescence with higher contrast between sound and demineralized areas and less reflections compared with white light image.
may occur in such lesions.7,19 However, because of the lack of means to quantify the changes in the mineral contents of these lesions, it has not been possible to document to which extent, in which pattern, and for how long a remineralization process continues. In the present study white spot lesions that had formed around fixed appliances during orthodontic treatment were followed lon-
598 Al-Khateeb et al.
American Journal of Orthodontics and Dentofacial Orthopedics June 1998
Fig. 3. Fluorescence radiance of original sound enamel at lesion site was reconstructed by interpolation of sound values around the lesion. Difference between measured and reconstructed values gave resulting fluorescence loss in lesion. Table I. Changes in fluorescence radiance DLmean/L%
DLmax/L%
Subject
Tooth*
Before
After
dmean†
Before
After
dmax†
A B
46 16 26 36 26 35 36 46 36 45 33 34 36 43 46
12.9 9.6 10.8 27.0 11.4 12.2 14.3 18.7 10.8 9.4 13.5 10.5 12.4 14.5 12.2
8.8 7.8 9.8 12.9 6.8 8.8 11.5 9.1 8.3 8.5 10.5 10.2 7.9 14.3 6.8
4.1 1.8 1.0 14.1 4.6 3.4 2.8 9.6 2.5 0.9 3.0 0.3 4.5 0.2‡ 5.4
40.0 25.0 33.0 66.7 34.7 77.7 44.7 50.3 31.3 38.3 40.0 34.0 31.2 65.0 43.0
21.0 17.3 23.3 28.7 16.3 47.7 38.7 33.0 22.0 26.7 26.3 24.0 19.0 57.0 15.3
19.0 7.7 9.7 38.0 18.4 30.0 6.0 17.3 9.3 11.6 13.7 10.0 12.2 8.0‡ 27.7
SD 5 3.59 n 5 14
dmax 5 16.24 p , 0.001
C D
E F
G
d# mean 5 4.02 p 5 0.001
SD 5 8.89 n 5 14
*According to the FDI system of notation. †The difference between fluorescence radiance at the beginning and the end of the study. ‡These values were excluded from the calculations.
gitudinally over a period of 1 year. Light-induced enamel autofluorescence was used as the basis for quantitative assessment of mineral changes. During the follow-up period of 1 year, partial regain of the fluorescence lost in the lesions and a decrease in the lesion areas occurred, which suggests that a process of remineralization had taken place. Both rate and pattern of remineralization were investigated during the study by monthly recordings of mineral changes in the lesions. The pattern of remineralization followed a time trend, i.e., the fluorescence regain was pronounced during the first few months and then continued at a slower rate. Such a pattern was also reported by AlKhateeb et al.14 about white spot lesions that were
produced in vitro and then remineralized in situ. A similar observation was also made in a study by Øgaard and ten Bosch.20 In that study, experimentally induced caries lesions were followed quantitatively in vivo during a 1-month period after which the teeth were extracted. It was reported that the remineralization process followed an exponential pattern. When considering the remineralization rate, the time period needed for the lesions described in the latter study20 to remineralize was much shorter than that for the lesions investigated in this study. This difference in the remineralization rate could be explained by differences in the surface layer of the two types of lesions, such as its thickness, porosity,
Al-Khateeb et al. 599
American Journal of Orthodontics and Dentofacial Orthopedics Volume 113, No. 6
Table II. Changes in lesion area Lesion area mm2 Subject
Tooth*
Before
After
darea†
A B
46 16 26 36 26 35 36 46 36 45 33 34 36 43 46
3.1 1.1 3.5 2.9 1.3 3.3 4.8 10.5 2.0 5.2 1.2 0.8 1.7 3.2 2.3
1.9 0.7 0.6 1.5 0.6 0.9 3.3 3.1 1.1 0.5 1.2 0.5 1.0 5.6 0.7
1.2 0.4 2.9 1.4 0.7 2.4 1.5 7.4 0.9 4.7 0.0 0.3 0.7 22.4‡ 1.6
C D
E F
G
darea 5 1.85 p , 0.01
SD 5 2.02 n 5 14
*According to the FDI system of notation. †The difference between the lesion areas at the beginning and the end of the study. ‡This value was excluded from the calculations.
and mineral content. The lesions investigated in the present study had developed during a relatively long time and were assumed, therefore, to be subsurface in nature. Lesions described by Øgaard and ten Bosch,20 on the other hand, were induced experimentally within a few weeks. They were characterized by surface softening with preferential removal of the interprismatic substance and mineral loss that was particularly pronounced in the outermost enamel layer.4 Thus, remineralization occurred within only 1 month. In another study by Marcusson et al.,7 changes in white spot lesions formed around orthodontic brackets were recorded by photography during a 2-year period. For evaluation of the records, an index modified from that described by Geiger et al.22 was applied. They found that the size of the lesions decreased during the period of observation. This result was supported by the findings of the present study. The remineralization of the white spot lesions after removal of the fixed orthodontic appliances, as seen in the present study, can be attributed to a reduction of the cariogenic challenge. By removal of the accumulated plaque and cariogenic microorganisms around the appliances, which has been noticed to increase significantly during orthodontic treatment,23-27 the cariogenic challenge is substantially reduced. Other factors of importance in this respect could be reduced oral clearance time for cariogenic
food items and also more efficient tooth brushing after the appliances have been removed. Moreover, some studies19,28 have suggested that regression of white spot lesions after the removal of orthodontic appliances is concomitant with marked surface wear of the lesion area as a result of the mechanical removal of the partly softened surface enamel. During the present study, no topical fluoride was used in addition to the recommended F toothpaste. It was intended to induce gradual remineralization without using excessive fluoride concentration. Slow and gradual recovery of white spot lesions would have a beneficial effect on the quality of remineralization and would be favorable from an aesthetic point of view as well. During and after application of high concentration of fluoride, large amounts of fluoride are adsorbed in the lesion because of the great affinity of the demineralized regions to fluoride.29 As a result of this high fluoride concentration, mineral precipitation will be accelerated in the outermost region of the lesion; this process draws away many of the free mineral ions from the inner pores of the lesion and thus slows down diffusion toward the lesion interior.30 This will result in a delay of the remineralization of the lesion body. In addition, the excess deposition, also described by O’Reilly and Featherstone31 as hyperremineralization, may cause the lesion pores to be blocked with mineral and result in a more pronounced diffusion inhibition.30
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American Journal of Orthodontics and Dentofacial Orthopedics June 1998
Fig. 4. A and B, Changes in fluorescence images over time for two of lesions.
Facilitated oral hygiene and improved dietary habits are the essential prerequisites to initiate the healing process of the white spot lesions. Fluoride per se cannot prevent caries development if the cariogenic challenge is unchanged.32 This could be seen in patient F who did not exhibit better oral hygiene after removal of the fixed appliance; there
was general plaque accumulation on all teeth, especially in the lower right quadrant of the dental arch. The optical caries monitor used by Øgaard and ten Bosch20 is another quantitative method for assessment of mineral changes in enamel. This method is based on optical fiber technology with a light-scattering phenomenon that has the potential
Al-Khateeb et al. 601
American Journal of Orthodontics and Dentofacial Orthopedics Volume 113, No. 6
Fig. 5. A, Change in mean fluorescence loss; B, maximum fluorescence loss at deepest point of lesion; and C, size of lesion area of the same tooth as in Fig. 4,A.
for quantification of mineral changes in the enamel over time. However, there are a few limitations to the method when used clinically.33 Such limitations include difficulties in repositioning the optical monitoring probe at the same measuring point on different occasions when used longitudinally, especially when the lesion area might change over time regarding shape, size, surface structure, etc. There is also the problem with sterilization of the optical caries monitor probe, which needs to be overcome before clinical application of that method. With the QLF method a good reproducibility of the measurements can be obtained by standardization of the images based on the recordings from the previous images. Furthermore, problems with sterilization of the measuring equipment do not affect the QLF method.
CONCLUSION The results from this study demonstrate the efficiency of the QLF method to monitor longitudinally small changes in incipient enamel lesions. The method could be very useful, therefore, for investigations of the effect of preventive and therapeutic measures in various cariogenic risk groups, such as orthodontic patients. Furthermore, it was concluded that white spot lesions formed around fixed orthodontic appliances recover partly over a relatively long period of time. Long-term follow-up studies and investigations would be necessary to further evaluate the development of these lesions quantitatively and aesthetically.
REFERENCES 1. Wisth PJ, Nord A. Caries experience in orthodontically treated individuals. Angle Orthod 1977;47:59-64. 2. Gorelick L, Geiger A, Gwinnett AJ. Incidence of white spot formation after bonding and banding. Am J Orthod 1982;81:93-8.
602 Al-Khateeb et al. 3. Årtun J, Brobakken BO. Prevalence of carious white spots after orthodontic treatment with multibonded appliances. Eur J Orthod 1986;8:229-34. 4. Øgaard B, Rolla G, Arends J. Orthodontic appliances and enamel demineralization. Part 1. Lesion development. Am J Orthod Dentofacial Orthop 1988;94:68-73. 5. Zachrisson BU, Zachrisson S. Caries incidence and oral hygiene during orthodontic treatment. Scand J Dent Res 1971;79:394-401. 6. Backer-Dirks O. Post-eruptive changes in dental enamel. J Dent Res 1966;45:50311. 7. Marcusson A, Norevall L-I, Persson M. White spot reduction when using glass ionomer cement for bonding in orthodontics: a longitudinal and comparative study. Eur J Orthod 1997;19:233-42. 8. Bjelkhagen H, Sundstro ¨m F, Angmar-Månsson B, Ryde´n H. Early detection of enamel caries by the luminescence excited by visible laser light. Swed Dent J 1982;6:1-7. 9. Sundstro ¨m F, Fredriksson K, Montan S, Hafstro ¨m-Bjo ¨rkman U, Stro ¨m J. Laser induced fluorescence from sound and carious tooth substance: spectroscopic study. Swed Dent J 1985;9:71-80. 10. Angmar-Månsson B, ten Bosch JJ. Optical methods for the detection and quantification of caries. Adv Dent Res 1987;1: 14-20. 11. de Josselin de Jong E, Hall AF, van der Veen MH. Quantitative light-induced fluorescence detection method: a Monte Carlo simulation model. In: Stookey GK, editor. Early detection of dental caries. Indianapolis: Indiana University, School of Dentistry; 1996. p. 91-103. 12. ten Bosch JJ. Light scattering and related methods in caries diagnosis. In: Stookey GK, editor. Early detection of dental caries. Indianapolis: Indiana University, School of Dentistry; 1996. p. 81-90. 13. Hafstro ¨m-Bjo ¨rkman U, Sundstro ¨m F, de Josselin de Jong E, Oliveby A, AngmarMånsson B. Comparison of laser fluorescence and longitudinal microradiography for quantitative assessment of in vitro enamel caries. Caries Res 1992;26:241-7. 14. A1-Khateeb S, Oliveby A, de Josselin de Jong E, Angmar-Månsson B. Laser fluorescence quantification of remineralisation in situ of incipient enamel lesions: influence of fluoride supplements. Caries Res 1997;31:132-40. 15. Emami Z, AI-Khateeb S, de Josselin de Jong E, Sundstro ¨m F, Angmar-Månsson B. Mineral loss in incipient caries lesions quantified with laser fluorescence and longitudinal microradiography. Acta Odontol Scand 1996;54:8-13. 16. Ando M, Hall AF, Eckert GJ, Schemehorn BR, Analoui M, Stookey GK. Relative ability of laser fluorescence techniques to quantitate early mineral loss in vitro. Caries Res 1997;31:125-31. 17. A1-Khateeb S, ten Cate JM, Angrnar-Månsson B, de Josselin de Jong E, Exterkate RAM, Sundstro ¨m G, Oliveby A. Quantification of lesion formation and remineralization with a new portable fluorescence device. Adv Dent Res 1997;11:502-6. 18. de Josselin de Jong E, Sundstro ¨m F, Westerling H, Tranaeus S, ten Bosch JJ, Angmar-Månsson B. A new method for in vivo quantification of mineral loss in enamel with laser fluorescence. Caries Res 1995;29:2-7.
American Journal of Orthodontics and Dentofacial Orthopedics June 1998 19. Årtun J, Thylstrup A. A 3-year clinical and SEM study of surface changes of carious lesions after inactivation. Am J Orthod Dentofacial Orthop 1989;95:327-33. 20. Øgaard B, ten Bosch JJ. Regression of white spot enamel lesions: a new optical method for quantitative longitudinal evaluation in vivo. Am J Orthod Dentofacial Orthop 1994;106:238-42. 21. Fejerskov O, Clarkson BH. Dynamics of caries lesion formation. In: Fejerskov O, Ekstrand J, Burt BA, editors. Fluoride in dentistry. Copenhagen: Munksgaard; 1996. p. 187-213. 22. Geiger AM, Gorelick L, Gwinnett AJ, Griswold PG. The effect of a fluoride program on white spot formation during orthodontic treatment. Am J Orthod Dentofacial Orthop 1988;93:29-37. 23. Corbett JA, Brown LR, Keene HJ, Horton TM. Comparison of Streptococcus mutans concentrations in non-bonded and bonded orthodontic patients. J Dent Res 1981;60:1936-42. 24. Mattingly JA, Sauer GJ, Yancey JM, Arnold RR. Enhancement of streptococcus mutans colonization by direct bonded orthodontic appliances. J Dent Res 1983; 62:1209-11. 25. Scheie AA, Arneberg P, Krogstaad O, Effect of orthodontic treatment on prevalence of streptococcus mutans in plaque and saliva. Scand J Dent Res 1984;92:211-7. 26. Lundstro ¨m F, Krasse B. Streptococcus mutans and lactobacilli frequency in orthodontic patients; the effect of chlorhexidine treatments. Eur J Orthod 1987;9: 109-16. 27. Forsberg C-M, Brattstro ¨m V, Malmberg E, Nord CE. Ligature wires and elastomeric rings; two methods of ligation and their association with microbial colonization of streptococcus mutans and lactobacilli. Eur J Orthod 1991;13:416-20. 28. Holmen L, Thylstrup A, Årtun J. Surface changes during the arrest of active enamel carious lesions in vivo: a scanning electron microscope study. Acta Odontol Scand 1987;45:383-90. 29. Sakkab NY, Cilley WA, Haberman JP. Fluoride in deciduous teeth from an anticaries clinical study. J Dent Res 1984;63:1201-5. 30. ten Cate JM, Featherstone JDB. Physicochemical aspects of fluoride-enamel interactions. In: Fejerskov O, Ekstrand J, Burt BA, eds. Fluoride in dentistry. Copenhagen: Munksgaard, 1996:252-72. 31. O’Reilly MM, Featherstone JDB. Demineralization and remineralization around orthodontic appliances: an in vivo study. Am J Orthod Dentofacial Orthop 1987;92:33-40. 32. Holmen L, Øgaard B, Rolla G, Thylstrup A. A polarized light and scanning electron microscope study of the effect of Duraphat treatment on in vivo caries. Scand J Dent Res 1986;94:521-9. 33. Angmar-Månsson B, A1-Khateeb S, Tranaeus S: Monitoring the caries process optical methods for clinical diagnosis and quantification of enamel caries. Eur J Oral Sci 1996; 104:480-5.
Volume 113 Number 6
June 1998
Copyright © 1998 by the American Association of Orthodontists
ORIGINAL ARTICLE
A longitudinal laser fluorescence study of white spot lesions in orthodontic patients Susan AI-Khateeb, DDS,a Carl-Magnus Forsberg, DDS, PhD,b Elbert de Josselin de Jong, MSc, PhD,c and Birgit Angmar-Månsson, DDS, PhDd Huddinge, Sweden, and Amsterdam, The Netherlands Orthodontic treatment with fixed appliances increases the caries risk in young persons. The aim of this study was to apply a new caries diagnostic method, quantitative laser fluorescence, for longitudinal in vivo quantification of changes in incipient enamel lesions related to fixed orthodontic appliances. Seven young patients with active caries lesions disclosed at removal of the orthodontic brackets and bands were enrolled in the study. Caries preventive measures were intensified, including dietary advice, oral hygiene instructions, and the regular use of a fluoride dentifrice. The caries lesions were monitored with the quantitative laser fluorescence method after removal of the brackets and once a month thereafter. For each lesion, three quantities were measured: lesion area (mm2), mean fluorescence loss (%) over the lesion, and maximum loss of fluorescence (%) in the lesion. During a 1-year follow-up period, the areas of the lesions decreased and the enamel fluorescence lost was partly regained indicating that a remineralization process had occurred. It was concluded that quantitative laser fluorescence seems suitable for in vivo monitoring of mineral changes in incipient enamel lesions, and useful for the evaluation of preventive measures in caries prone persons, such as orthodontic patients. (Am J Orthod Dentofacial Orthop 1998;113:595-602)
E
namel demineralization with white spot formation on buccal surfaces of teeth is a relatively common side effect from orthodontic treatment with fixed appliances.1-3 Treatment with fixed appliances makes conventional oral hygiene for plaque removal more difficult, thus increasing the cariogenic challenge on surfaces that normally show a low prevalence of dental caries.4 White spot formation has been attributed to the effect of prolonged accumulation and retention of the bacterial plaque on enamel surfaces adjacent to the appliances. There is evidence, however, that suggests that such small areas of superficial enamel demineralization may remineralize.6,7 From Karolinska Institutet. a Departments of Cariology and Orthodontics. b Associate Professor, Department of Orthodontics. c Inspektor Research Systems BV. d Professor and chair, Department of Cariology. Reprint requests to: Susan Al-Khateeb, Department of Cariology, Faculty of Odontology, Karolinska Institutet, P.O. Box 4064, SE-141 04 Huddinge, Sweden. E-mail: [email protected] Copyright © 1998 by the American Association of Orthodontists. 0889-5406/98/$5.00 1 0 8/1/83878
Sensitive methods that enable early detection and quantification of caries lesions make it possible to monitor changes in the enamel over time. Laser light induced fluorescence as a diagnostic method for detection of enamel caries at an early stage was introduced in 1982.8 When the tooth is illuminated with a broad beam of bluegreen laser light (488 nm) according to this method, enamel autofluorescence occurs in the yellow region of the light spectrum and may be observed through a yellow high pass filter9 that excludes the tooth scattered blue laser light. When enamel demineralization takes place, minerals will be replaced mainly by water causing a decrease in the light path in the tooth substance. This will result in reduction of light absorption by enamel.10 Because fluorescence is a result of absorption, the intensity of fluorescence will decrease in demineralized regions of the enamel, which appear darker than the sound tooth structure.11,12 A quantitative version of the laser fluorescence method (QLF) has been tested for assessment of mineral changes in artificial lesions during demineralization in vitro,13 during remineralization in situ,14 595
596 Al-Khateeb et al.
and for assessment of mineral loss in natural incipient caries lesions in human enamel from a single measurement.15 These studies have indicated that changes in mineral contents of enamel lesions may be accurately recorded with the QLF method. Furthermore, transverse microradiography has been used to validate data obtained by the QLF method,14,16,17 and these studies have shown that there is a strong correlation between the two methods. This suggests that it should also be possible to calculate the lesion depth from the fluorescence loss value. The result of such a calculation, however, would be only an approximation of the lesion depth because the microradiographic method permits quantification of mineral content in thin sections obtained from the middle of the lesions, whereas the QLF method gives information about mineral loss over the whole lesion. The QLF method has undergone further development for in vivo quantification of mineral loss in natural enamel lesions with the use of a CCD micro video camera and computerized image analysis.18 The aim of the present study was to use the laser fluorescence method to quantitatively and longitudinally assess the changes in white spot lesions that had been formed around orthodontic bands and brackets in vivo. MATERIAL AND METHODS Patients This study was carried out on seven adolescents, aged 13-15 years, who exhibited white spot lesions. They were chosen from a number of patients who had just finished their orthodontic treatment with full fixed appliances (standard edgewise technique). The average treatment time was 2 years. After removal of the appliances, the patients were found to have 15 teeth with white spot lesions (10 first molars, 3 premolars, and 2 canines). Four of the affected molars had been banded with glass ionomer cement. The other molars had been bonded with buccal tubes using standard orthodontic bonding material. The premolars and the canines had been bonded with brackets. Enamel fluorescence images of the affected teeth were recorded just after debanding and debonding. Subsequent recordings were made monthly over a 1-year period. At each visit, three images were produced for each tooth. When the images were analyzed and the fluorescence loss and the size of the lesion areas were calculated, the mean values of the data obtained from the three recordings were used. Instructions about dietary habits and efficient oral hygiene including fluoride (F) toothpaste were given to the patients during the orthodontic treatment and during the study. The patients were provided with F toothpaste (Pepsodent Super Fluor, 0.145% F, Elida Robert, Stock-
American Journal of Orthodontics and Dentofacial Orthopedics June 1998
holm, Sweden) to be used twice a day throughout the investigation period. The study was approved by the Ethical Committee at Huddinge Hospital, and all patients gave their informed consent before the study. Measuring equipment A color CCD micro video camera (Panasonic WV-KS 152) equipped with a 15 mm focal-length lens was used to record the fluorescence images.18 The tooth surfaces were illuminated by blue-green light from an argon ion laser source (l 5 488 nm, 10 to 20 mW z cm–2). In order to exclude the tooth-scattered laser light and enable detection of the autofluorescence emitted by enamel, a yellow high pass filter (Hoya O-54) was placed in front of the camera to cut off light with a wave length less than 540 nm. The CCD camera viewed and recorded the fluorescence images through a dental mirror, as demonstrated in Fig. 1. The images were stored in a computer, processed, and analyzed by custom-made software (QLF 1.92, Inspektor Research Systems BV, Amsterdam, The Netherlands). Fig. 2 left shows the clinical image of a white spot lesion as it appears on the computer screen, and Fig. 2 right shows the laser fluorescence image of the same lesion. To calculate the fluorescence loss in the lesion in relation to sound enamel, the program reconstructed the fluorescence radiance (L, expressed in [W/m2.sr] 5 power per area per solid angle) at the lesion site from the fluorescence radiance of the surrounding sound enamel, which was assumed to be 100%. The difference between the reconstructed and the actual fluorescence radiance (DL) represented the fluorescence loss at the lesion site as demonstrated in Fig. 3. Three quantities were measured: the mean fluorescence loss over the lesion (DLmean/L in %), maximum fluorescence loss (DLmax/L in %), and lesion area (defined as the area [mm2] where fluorescence loss is $5%). Statistical analysis The paired Student’s t test was used to compare the fluorescence loss and the size of the lesion areas at the beginning of the study and 1 year later. The level of significance was chosen as p , 0.05. On studying the probability distribution of the recorded quantities, one variable was found to be slightly skewed: the DLmean/L showed a tendency toward positive skewness (1.664, p , 0.05). It is usually not appropriate to apply the t test to variables that depart from normality. In cases of minor skewness, however, and when the size of the sample is adequate, the t test may still provide an acceptable approximation of the true degree of difference between the two measurements. RESULTS
During the 1-year period of study, the fluorescence radiance in the enamel lesions increased indicating a mineral gain, and the lesion areas of
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Fig. 1. Schematic presentation of quantitative laser fluorescence set-up.
almost all white spots had decreased. The differences between the base-line and final values for Dmean/L and DLmax/L were highly significant, p 5 0.001, and p , 0.001, respectively (Table I). The mean area of the lesions was reduced at the end of the study (p , 0.01, Table II). Fig. 4A and B show the visual changes in the fluorescence images over time in two of the lesions (lower left first molar in subject B and lower left second premolar in subject D, respectively), i.e., less darkness at the lesion sites by the end of the study period. The quantitative data for the parameters Dmean/L, DLmax/L, and area of the lesion in Fig. 4A are presented as a function of time in Fig. 5A, B, and C, respectively. Data from the lower right canine (patient F) were excluded from the statistical analyses. Part of the lesion was obscured by inflamed and edematous gingiva at the baseline recording that was taken immediately after debonding. Thus, the data obtained for that lesion were not comparable at the two time points. DISCUSSION
Results of previous follow-up studies of white spot lesions have suggested that remineralization
Fig. 2. Left, shows clinical view of a buccal surface with an enamel white spot lesion illuminated with ordinary white light as presented on computer screen. Right, clinical laser fluorescence image of same lesion. Demineralized areas appear dark in laser fluorescence with higher contrast between sound and demineralized areas and less reflections compared with white light image.
may occur in such lesions.7,19 However, because of the lack of means to quantify the changes in the mineral contents of these lesions, it has not been possible to document to which extent, in which pattern, and for how long a remineralization process continues. In the present study white spot lesions that had formed around fixed appliances during orthodontic treatment were followed lon-
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Fig. 3. Fluorescence radiance of original sound enamel at lesion site was reconstructed by interpolation of sound values around the lesion. Difference between measured and reconstructed values gave resulting fluorescence loss in lesion. Table I. Changes in fluorescence radiance DLmean/L%
DLmax/L%
Subject
Tooth*
Before
After
dmean†
Before
After
dmax†
A B
46 16 26 36 26 35 36 46 36 45 33 34 36 43 46
12.9 9.6 10.8 27.0 11.4 12.2 14.3 18.7 10.8 9.4 13.5 10.5 12.4 14.5 12.2
8.8 7.8 9.8 12.9 6.8 8.8 11.5 9.1 8.3 8.5 10.5 10.2 7.9 14.3 6.8
4.1 1.8 1.0 14.1 4.6 3.4 2.8 9.6 2.5 0.9 3.0 0.3 4.5 0.2‡ 5.4
40.0 25.0 33.0 66.7 34.7 77.7 44.7 50.3 31.3 38.3 40.0 34.0 31.2 65.0 43.0
21.0 17.3 23.3 28.7 16.3 47.7 38.7 33.0 22.0 26.7 26.3 24.0 19.0 57.0 15.3
19.0 7.7 9.7 38.0 18.4 30.0 6.0 17.3 9.3 11.6 13.7 10.0 12.2 8.0‡ 27.7
SD 5 3.59 n 5 14
dmax 5 16.24 p , 0.001
C D
E F
G
d# mean 5 4.02 p 5 0.001
SD 5 8.89 n 5 14
*According to the FDI system of notation. †The difference between fluorescence radiance at the beginning and the end of the study. ‡These values were excluded from the calculations.
gitudinally over a period of 1 year. Light-induced enamel autofluorescence was used as the basis for quantitative assessment of mineral changes. During the follow-up period of 1 year, partial regain of the fluorescence lost in the lesions and a decrease in the lesion areas occurred, which suggests that a process of remineralization had taken place. Both rate and pattern of remineralization were investigated during the study by monthly recordings of mineral changes in the lesions. The pattern of remineralization followed a time trend, i.e., the fluorescence regain was pronounced during the first few months and then continued at a slower rate. Such a pattern was also reported by AlKhateeb et al.14 about white spot lesions that were
produced in vitro and then remineralized in situ. A similar observation was also made in a study by Øgaard and ten Bosch.20 In that study, experimentally induced caries lesions were followed quantitatively in vivo during a 1-month period after which the teeth were extracted. It was reported that the remineralization process followed an exponential pattern. When considering the remineralization rate, the time period needed for the lesions described in the latter study20 to remineralize was much shorter than that for the lesions investigated in this study. This difference in the remineralization rate could be explained by differences in the surface layer of the two types of lesions, such as its thickness, porosity,
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Table II. Changes in lesion area Lesion area mm2 Subject
Tooth*
Before
After
darea†
A B
46 16 26 36 26 35 36 46 36 45 33 34 36 43 46
3.1 1.1 3.5 2.9 1.3 3.3 4.8 10.5 2.0 5.2 1.2 0.8 1.7 3.2 2.3
1.9 0.7 0.6 1.5 0.6 0.9 3.3 3.1 1.1 0.5 1.2 0.5 1.0 5.6 0.7
1.2 0.4 2.9 1.4 0.7 2.4 1.5 7.4 0.9 4.7 0.0 0.3 0.7 22.4‡ 1.6
C D
E F
G
darea 5 1.85 p , 0.01
SD 5 2.02 n 5 14
*According to the FDI system of notation. †The difference between the lesion areas at the beginning and the end of the study. ‡This value was excluded from the calculations.
and mineral content. The lesions investigated in the present study had developed during a relatively long time and were assumed, therefore, to be subsurface in nature. Lesions described by Øgaard and ten Bosch,20 on the other hand, were induced experimentally within a few weeks. They were characterized by surface softening with preferential removal of the interprismatic substance and mineral loss that was particularly pronounced in the outermost enamel layer.4 Thus, remineralization occurred within only 1 month. In another study by Marcusson et al.,7 changes in white spot lesions formed around orthodontic brackets were recorded by photography during a 2-year period. For evaluation of the records, an index modified from that described by Geiger et al.22 was applied. They found that the size of the lesions decreased during the period of observation. This result was supported by the findings of the present study. The remineralization of the white spot lesions after removal of the fixed orthodontic appliances, as seen in the present study, can be attributed to a reduction of the cariogenic challenge. By removal of the accumulated plaque and cariogenic microorganisms around the appliances, which has been noticed to increase significantly during orthodontic treatment,23-27 the cariogenic challenge is substantially reduced. Other factors of importance in this respect could be reduced oral clearance time for cariogenic
food items and also more efficient tooth brushing after the appliances have been removed. Moreover, some studies19,28 have suggested that regression of white spot lesions after the removal of orthodontic appliances is concomitant with marked surface wear of the lesion area as a result of the mechanical removal of the partly softened surface enamel. During the present study, no topical fluoride was used in addition to the recommended F toothpaste. It was intended to induce gradual remineralization without using excessive fluoride concentration. Slow and gradual recovery of white spot lesions would have a beneficial effect on the quality of remineralization and would be favorable from an aesthetic point of view as well. During and after application of high concentration of fluoride, large amounts of fluoride are adsorbed in the lesion because of the great affinity of the demineralized regions to fluoride.29 As a result of this high fluoride concentration, mineral precipitation will be accelerated in the outermost region of the lesion; this process draws away many of the free mineral ions from the inner pores of the lesion and thus slows down diffusion toward the lesion interior.30 This will result in a delay of the remineralization of the lesion body. In addition, the excess deposition, also described by O’Reilly and Featherstone31 as hyperremineralization, may cause the lesion pores to be blocked with mineral and result in a more pronounced diffusion inhibition.30
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Fig. 4. A and B, Changes in fluorescence images over time for two of lesions.
Facilitated oral hygiene and improved dietary habits are the essential prerequisites to initiate the healing process of the white spot lesions. Fluoride per se cannot prevent caries development if the cariogenic challenge is unchanged.32 This could be seen in patient F who did not exhibit better oral hygiene after removal of the fixed appliance; there
was general plaque accumulation on all teeth, especially in the lower right quadrant of the dental arch. The optical caries monitor used by Øgaard and ten Bosch20 is another quantitative method for assessment of mineral changes in enamel. This method is based on optical fiber technology with a light-scattering phenomenon that has the potential
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Fig. 5. A, Change in mean fluorescence loss; B, maximum fluorescence loss at deepest point of lesion; and C, size of lesion area of the same tooth as in Fig. 4,A.
for quantification of mineral changes in the enamel over time. However, there are a few limitations to the method when used clinically.33 Such limitations include difficulties in repositioning the optical monitoring probe at the same measuring point on different occasions when used longitudinally, especially when the lesion area might change over time regarding shape, size, surface structure, etc. There is also the problem with sterilization of the optical caries monitor probe, which needs to be overcome before clinical application of that method. With the QLF method a good reproducibility of the measurements can be obtained by standardization of the images based on the recordings from the previous images. Furthermore, problems with sterilization of the measuring equipment do not affect the QLF method.
CONCLUSION The results from this study demonstrate the efficiency of the QLF method to monitor longitudinally small changes in incipient enamel lesions. The method could be very useful, therefore, for investigations of the effect of preventive and therapeutic measures in various cariogenic risk groups, such as orthodontic patients. Furthermore, it was concluded that white spot lesions formed around fixed orthodontic appliances recover partly over a relatively long period of time. Long-term follow-up studies and investigations would be necessary to further evaluate the development of these lesions quantitatively and aesthetically.
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American Journal of Orthodontics and Dentofacial Orthopedics June 1998 19. Årtun J, Thylstrup A. A 3-year clinical and SEM study of surface changes of carious lesions after inactivation. Am J Orthod Dentofacial Orthop 1989;95:327-33. 20. Øgaard B, ten Bosch JJ. Regression of white spot enamel lesions: a new optical method for quantitative longitudinal evaluation in vivo. Am J Orthod Dentofacial Orthop 1994;106:238-42. 21. Fejerskov O, Clarkson BH. Dynamics of caries lesion formation. In: Fejerskov O, Ekstrand J, Burt BA, editors. Fluoride in dentistry. Copenhagen: Munksgaard; 1996. p. 187-213. 22. Geiger AM, Gorelick L, Gwinnett AJ, Griswold PG. The effect of a fluoride program on white spot formation during orthodontic treatment. Am J Orthod Dentofacial Orthop 1988;93:29-37. 23. Corbett JA, Brown LR, Keene HJ, Horton TM. Comparison of Streptococcus mutans concentrations in non-bonded and bonded orthodontic patients. J Dent Res 1981;60:1936-42. 24. Mattingly JA, Sauer GJ, Yancey JM, Arnold RR. Enhancement of streptococcus mutans colonization by direct bonded orthodontic appliances. J Dent Res 1983; 62:1209-11. 25. Scheie AA, Arneberg P, Krogstaad O, Effect of orthodontic treatment on prevalence of streptococcus mutans in plaque and saliva. Scand J Dent Res 1984;92:211-7. 26. Lundstro ¨m F, Krasse B. Streptococcus mutans and lactobacilli frequency in orthodontic patients; the effect of chlorhexidine treatments. Eur J Orthod 1987;9: 109-16. 27. Forsberg C-M, Brattstro ¨m V, Malmberg E, Nord CE. Ligature wires and elastomeric rings; two methods of ligation and their association with microbial colonization of streptococcus mutans and lactobacilli. Eur J Orthod 1991;13:416-20. 28. Holmen L, Thylstrup A, Årtun J. Surface changes during the arrest of active enamel carious lesions in vivo: a scanning electron microscope study. Acta Odontol Scand 1987;45:383-90. 29. Sakkab NY, Cilley WA, Haberman JP. Fluoride in deciduous teeth from an anticaries clinical study. J Dent Res 1984;63:1201-5. 30. ten Cate JM, Featherstone JDB. Physicochemical aspects of fluoride-enamel interactions. In: Fejerskov O, Ekstrand J, Burt BA, eds. Fluoride in dentistry. Copenhagen: Munksgaard, 1996:252-72. 31. O’Reilly MM, Featherstone JDB. Demineralization and remineralization around orthodontic appliances: an in vivo study. Am J Orthod Dentofacial Orthop 1987;92:33-40. 32. Holmen L, Øgaard B, Rolla G, Thylstrup A. A polarized light and scanning electron microscope study of the effect of Duraphat treatment on in vivo caries. Scand J Dent Res 1986;94:521-9. 33. Angmar-Månsson B, A1-Khateeb S, Tranaeus S: Monitoring the caries process optical methods for clinical diagnosis and quantification of enamel caries. Eur J Oral Sci 1996; 104:480-5.