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Adherence of Streptococcus mutans to orthodontic brackets
ORIGINAL ARTICLE Adherence of Streptococcus mutans to orthodontic brackets André Fournier, DMD,a and Lise Payant, BSc, DMD, MHE,b and Robert Bouclin, BScc Sainte-Foy, Quebec The affinity of Streptococcus mutans to orthodontic brackets made from metal, plastic, and ceramic was tested. Twelve saliva-coated brackets and 12 noncoated brackets of each type were immersed in a S. mutans solution labeled with [3H] thymidine. Each sample was then immersed in distilled water at 20°C for 24, 48, and 72 hours to measure the adherence of S. mutans to these samples. During the first 24 hours, the adherence of S. mutans decreased with and without saliva coating. Between 24 and 72 hours, the adherence of S. mutans to the saliva-coated brackets remained unchanged; the adherence to uncoated brackets showed a decrease. Saliva coating caused a decreased affinity of S. mutans for all products tested. The initial affinity of S. mutans to metal brackets was statistically significantly lower than that to plastic and porcelain brackets with and without saliva coating. (Am J Orthod Dentofacial Orthop 1998;114:414-7)
T
he initial affinity of bacteria to solid surfaces is due mostly to electrostatic and hydrophobic interactions.1-3 It has also been shown that the physicochemical properties of the bacteria as well as those of the solid surface contribute as mediators during the process of adherence to hard surfaces.4 The composition, as well as the rate of saliva secretion, may also affect bacterial adherence.4 It is well known that the adherence of oral bacteria to enamel tooth surfaces and orthodontic materials has a harmful effect on teeth and periodontal tissues.5 Recent studies indicate that patients who received orthodontic treatments were more susceptible to enamel white spot formation.6,7 In particular, metallic orthodontic brackets have been found to induce specific changes in the buccal environment such as decreased pH, increased plaque accumulation,8,9 and elevated S. mutans colonization.10,11 Thus, metal brackets impose a potential risk for enamel decalcification.12,13 Although ceramic and plastic brackets are relatively new in the orthodontic armamentarium, their bond strength, morphologic nature, and plaque-retaining capacities have been studied.14-16 In a recent article, Eliades et al.16 studied the surface tension of raw material used to fabricate metal, plastic, and ceramic brackets. Stainless steel presented the highest critical surface tension and is expected to have the higher plaqueretaining capacity. From the Faculté de Médecine Dentaire Université Laval. aProfessor, Department of Orthodontics, Faculty of Dentistry, Université Laval. bProfessor, Department of Prosthodontics, Faculty of Dentistry, Université Laval. cUndergraduate student, Faculty of Dentistry, Université Laval. Reprint requests to: Dr. André Fournier, Faculté de Médecine Dentaire, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4 Copyright © 1998 by the American Association of Orthodontists. 0889-5406/98/$5.00 + 0 8/1/87455
414
The objectives of this investigation are (1) to compare the initial affinity of S. mutans to metal, plastic, and ceramic brackets, (2) to compare the adherence of S. mutans to metal, plastic, and ceramic brackets over time, and (3) to study the effect of saliva on the affinity and adherence of S. mutans to orthodontic brackets. MATERIAL AND METHODS Bacteria and Cultivation Conditions
S. mutans was isolated from the saliva of 48 young adults (age range, 26 to 52 years) on solid trypticase medium containing 3% yeast extract (TSBYA) and stored in aliquots at –20°C as described by Parrot et al.17 Radioactive Labeling of Cells
S. mutans strains were routinely grown in liquid TSBYA. For each milliliter of TSBYA broth, 10 µl of frozen stock of S. mutans and .5 µCi [3H] thymidine (New England Nuclear Corp., Boston, Mass.) were added. The culture was incubated overnight at 37°C, without agitation in an aerobic environment. The purity of the culture was verified with a TSBYA petri dish. The suspension was placed in the centrifuge (Sorvall RCSC with SS-34 rotor) at 7700g for 10 minutes at 4°C and the supernatant was removed. The pellet was washed twice with sterile distilled water and placed in a centrifuge at 7700g for 10 minutes at 4°C. Finally, the pellet was resuspended in a potassium phosphate buffer (l mm, pH 6.0) with 50 mm potassium chlorine, 1 mm calcium chloride, and .01 mm magnesium chloride at a density of approximately 108 cells per ml. The suspension was sonified on ice (Sonifier Cell Disruptor w350, Smithkline Co.) at an intensity of 110 watts for a period of 20 seconds.
Fournier, Payant, and Bouclin
American Journal of Orthodontics and Dentofacial Orthopedics Volume 114, Number 4
415
Fig 1. Initial affinity and adherence of S. mutans to saliva-coated brackets over time. All values represent the average of 12 measurements. Percentage of adherence represents the radioactive counts from brackets/total counts per minute per milliliter of the S. mutans solution × 100%. Time refers to storage time of brackets in distilled water after immersion in S. mutans solution.
Fig 2. Initial affinity and adherence of S. mutans to non–saliva-coated brackets over time. All values represent the average of 12 measurements. Percentage of adherence represents the radioactive counts from brackets per counts per minute per milliliter of the S. mutans solution × 100%. Time refers to storage time of brackets in distilled water after immersion in S. mutans solution.
To measure radioactivity, samples (.l ml) were added to 5 ml of a scintillation cocktail and radioactivity was counted with a liquid scintillation counter (model LS 7500, Beckman Instruments).
Table I.
Preparation of Clarified Saliva
Paraffin-stimulated saliva was collected on ice from six individuals. The saliva was clarified by centrifugation at 12,000g for 10 minutes at 4°C and heated to 60°C for 30 minutes as described by Nesbitt et al.18 Preparation of the Orthodontic Brackets
Brackets were made from either plastic, porcelain, or metal. All brackets come from a commercial brand. Metal brackets were Ormco mini-diamond brackets welded on mesh pads. Plastic brackets were Ormco spirit brackets without silanated bases and without steel reinforced slot. Ceramic brackets were from Cerum Ortho Organisers with mechanical mesh (without silanated bases). Saliva-coated brackets were placed in a scintillation vial and immersed in 2 ml of clarified saliva for 2 hours with agitation at 20°C. Non–salivacoated brackets were placed in a scintillation vial and immersed in 2 ml of distilled water for 2 hours with agitation at 20°. Adherence of S. mutans to Brackets
Each bracket was placed in a scintillation vial and immersed in 2 ml of a labeled S. mutans suspension for 6 hours without agitation at 20°C in an aerobic environment. After this period of time, the brackets were rinsed three times in 5 ml of sterile distilled water and were immersed in 5 ml of sterile distilled water for 24, 48, or 72 hours at 20°C in an aerobic environment
Affinity of S. mutans to saliva-coated brackets
Metal Plastic Ceramic
Metal
Plastic
Ceramic
— S S
S — N.S.
S N.S. —
without agitation. After their respective period of immersion, the brackets were transferred to scintillation vials with 5 ml scintillation liquid; the radioactivity was counted with the scintillation counter. Calculations and Statistics
The average of 12 measurements was calculated for each parameter. The mean radioactive counts were divided by the total counts per minute per milliliter of the S. mutans suspension solution. From this calculation, the percentage of adherence of S. mutans was obtained. With the use of a Statview program, differences between groups were tested for statistical significance (P < .05) by use of an analysis of variance (ANOVA). A Fisher posthoc test was further applied to locate the significant differences. RESULTS Affinity of S. mutans for Metal, Plastic, and Porcelain Brackets
Saliva-coated brackets (Table I and II and Fig 1). The initial affinity of S. mutans to metal brackets was significantly lower (P < .05) than the affinity to plastic brackets and porcelain brackets. No significant difference was found between porcelain and plastic brackets. At time 24, 48, and 72 hours, there was no significant
416
Fournier, Payant, and Bouclin
Table II.
American Journal of Orthodontics and Dentofacial Orthopedics October 1998
Analysis of variance of initial affinity of S. mutans to saliva-coated brackets Group
Count
Mean
SD
Metal Plastic Ceramic
11 11 11
1325 1430 3153
325 227 1111
Source Between subjects Within subjects Treatments Residual Total
df
Sum of Squares
Mean Square
10 22 2 20 32
4489181,303 32591077,027 23160950,622 9430126,404 37080258,33
448918,13 1481412,592 11580475,311 471506,32
F-test
P-value
,303
,9726
24,561
,0001
SD, Standard deviation. df, Degrees of freedom.
statistical difference among the adherence of S. mutans to metal, plastic, or porcelain brackets. Non–saliva-coated brackets (Fig 2). The initial affinity of S. mutans to porcelain brackets was significantly higher that the affinity to metal brackets and to plastic brackets. After 24 and 48 hour storage time, the adherence of S. mutans to metal and plastic brackets was again statistically significantly lower than to porcelain brackets. After 72 hour storage time, the adherence of S. mutans to metal was significantly lower than to porcelain and plastic brackets. No significant difference was found between porcelain and plastic brackets after 72 hours in distilled water. Effect of Storage Time on Adherence to Brackets
Saliva-coated brackets (Fig 1). The initial affinity of S. mutans to saliva-coated metal, porcelain, and plastic brackets was significantly higher than the adherence to the same product after 24-hour, 48-hour, and 72-hour storage times. There was no significant difference among 24-hour, 48-hour, and 72 hour storage times. Non–saliva-coated brackets (Fig 2). For non–saliva-coated metal, plastic, and porcelain brackets, the initial affinity was statistically significantly higher than the adherence of the same product at 24-hour, 48-hour, and 72-hour storage times. There was, however, no significant difference between 24 hours and 48 hours for all products. The adherence at 72 hours was lower than after 24 and 48 hours for all products. Effect of Saliva-coating on Adherence
For metal, plastic, and porcelain brackets, non–saliva-coated samples showed a significantly greater initial affinity and a greater adherence after 24-hour and 48hour storage times than saliva-coated samples. No statistically significant difference was observed at 72-hour
storage time for all products among coated and noncoated samples. DISCUSSION
The main objective of this study was to determine if the material used for orthodontic brackets has an effect on bacterial affinity to these appliances in a situation that simulates that of clinical use (except for the temperature, which was not the body temperature, only for convenience). For that same reason, we preferred to collect a pool of S. mutans rather than to use an isolated strain of S. mutans. We think that isolated strains are more susceptible to genetic mutations, and it was not necessary in our experiment to use strains from which the genetic code has been studied. One could also question our use of distilled water rather than a growth medium to study the adherence of S. mutans to the specimen. This question is of clinical importance, but we focused our attention more on the elution phenomenon than on the growth of the bacteria. In fact, we do not want cell division to occur because it would then be impossible to measure unlabeled bacteria. Our findings seem to indicate that adherence of S. mutans is weaker on metal than plastic and ceramic brackets. In our experimental design, we assumed that the surface of all the brackets were the same, which we know is not absolutely true. This fact may partly explain why our findings differ from what we should expect from an analysis of exact dimension samples from raw material. However, our experimental surface (with the exception of the portion of the bracket that binds to the tooth) is equivalent to the surface encountered in a clinical situation. Our findings also seem to indicate that the presence of saliva tends to lower the adherence of S. mutans to each of the materials tested. These results are in accordance with those of Suljak et al19 who reported that precoating composites with saliva led to decreased
Fournier, Payant, and Bouclin
American Journal of Orthodontics and Dentofacial Orthopedics Volume 114, Number 4
binding of viable cells of Streptococcus sanguis and Streptococcus salivarius. The decreased adherence may result from an alteration in the chemical composition at the surface of the composite. A deposition of carbon nitrogen and oxygen onto composite material has been detected by Auger analysis after a 2-hour incubation in the mouth.20 The presence of histatins and lyzozymes in saliva, which possess exceptional antibacterial activities, may also contribute to the decreased adhesion of S. mutans to composites.21
4.
5. 6. 7.
8. 9.
CONCLUSION
10.
The above results seems to indicate that because of their lower affinity, metal brackets present a lower potential for bacterial accumulation than plastic and ceramic brackets. However, because we found no statistical difference in adherence over time, it is difficult to make a clear assessment that metal brackets have a lower cariogenic effect on the teeth than plastic and ceramic brackets. Also many parameters have not been taken into account in this experiment. To mention a few, there is the form, size, and position of the brackets, the presence or absence of a gingival hook, prophylaxis, etc.
11.
12.
13.
14. 15. 16.
17. 18.
REFERENCES 1. Rutter PR, Abbott A. A study of the interaction between oral streptococci and hard surfaces. J Gen Microbiol 1978;105:219-26. 2. Larsson K, Glantz PO. Microbial adhesion to surfaces with different surface charges. Acta Odontol Scand 1981;39:79-82. 3. Minagi S, Miyake Y, Inagaki K, Tsum H, Suginaka H. Hydrophobic interaction in
19. 20. 21.
417
Candida albicans and Candida tropicalis adherence to various denture base resin materials. Infect Immun 1985;47:11-4. Van Pelt AW, Weerkamp AH, Uyen MHWJC, Busscher HJ, DeJong HP, Arends J. Adhesion of Streptococcus sanguis CH3 to polymers with different surface free energies. Appl Envir Microbiol 1985;49:1270-5. Satou J, Fukunaga A, Satou N, Shintani H, Okuda K. Streptococcal adherence on various restorative materials. J Dent Res 1988;67:588-91. Gorelick L, Geiger AM, Gwinnet AJ. Incidence of spot formation after bonding and banding. Am J Orthod 1982;81:93-8. Ogaard B. Prevalence of white spot lesions in 19 year olds: a study on untreated and orthodontically treated persons 5 years after treatment. Am J Orthod Dentofacial Orthop 1989;96: 423 -7. Balenseifen JW, Madonia JV. Study of dental plaque in orthodontic patients. J Dent Res 1970;49:320-4. Menzaghi N, Saletta M, Garattini G, Brambilla E, Strohmenger L. Changes in the yeast oral flora in patients in orthodontic treatment. Prev Assist Dent 1991;17:26-30. Rosenbloom RG, Tinanoff N. Salivary Streptococcus mutans levels in patients before, during and after orthodontic treatment. Am J Orthod Dentofacial Orthop 1991;100:35-7. Forsberg CM, Brattström V, Maimberg 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. Saemundsson SR, Bergmann H, Magnúsdóttir MO, Holbrook WP. Dental caries and Streptococcus mutans in a rural child population in Iceland. Scand J Dent Res 1992; 100:299-303. Sansone C, Van Houte J, Jodhipura K, Kent R, Margolis,HC. The association of mutans streptococci and non-mutans streptococci capable of acidogenesis at low pH with dental caries on enamel and root surfaces. J Dent Res 1993;72:50816. Eliades T, Viazis AD, Eliades G. Bonding of ceramic brackets to enamel: morphologic and structural considerations. Am J Orthod Dentofacial Orthop 1991;99:369-75. Eliades T, Viazis AD, Lekka M. Failure mode analysis of ceramic brackets bonded to enamel. Am J Orthod Dentofacial Orthop 1993;104:21-6. Eliades T, Eliades G, Brantley WA. Microbial attachment on orthodontic appliances: I. Wettability and early pellicle formation on bracket materials. Am J Orthod Dentofacial Orthop 1995;99:351-75. Parrot M, Dréan MF, Trahan L, Lavoie MC. Incidence of bacteriocinogeny among fresh isolates of Streptococcus mutans. Can J Microbiol 1990;36;507-9. Nesbitt WE, Doyle RJ, Taylor KG. Hydrophobic interaction and the adherence of Streptococcus sanguis to hydroxyapatite. Infect and Immun 1982;38:637-44. Suljak JP, Reid G, Wood SM, McConnell RJ, Van der Mei HC, Busscher HJ. Bacterial adhesion to dental amalgam and three resin composites. J Dent 1995;23:171-6. Skjorland KK. Auger analysis of integuments formed on different dental filling materials in vivo. Acta Odontol Scand 1982;40:129-34. Schenkels L, Veerman E, Nieuw Amerongen A. Biochemical composition of human saliva in relation to other mucosal fluids Crit Rev Oral Biol Med 1995;6:161-75.
T
he initial affinity of bacteria to solid surfaces is due mostly to electrostatic and hydrophobic interactions.1-3 It has also been shown that the physicochemical properties of the bacteria as well as those of the solid surface contribute as mediators during the process of adherence to hard surfaces.4 The composition, as well as the rate of saliva secretion, may also affect bacterial adherence.4 It is well known that the adherence of oral bacteria to enamel tooth surfaces and orthodontic materials has a harmful effect on teeth and periodontal tissues.5 Recent studies indicate that patients who received orthodontic treatments were more susceptible to enamel white spot formation.6,7 In particular, metallic orthodontic brackets have been found to induce specific changes in the buccal environment such as decreased pH, increased plaque accumulation,8,9 and elevated S. mutans colonization.10,11 Thus, metal brackets impose a potential risk for enamel decalcification.12,13 Although ceramic and plastic brackets are relatively new in the orthodontic armamentarium, their bond strength, morphologic nature, and plaque-retaining capacities have been studied.14-16 In a recent article, Eliades et al.16 studied the surface tension of raw material used to fabricate metal, plastic, and ceramic brackets. Stainless steel presented the highest critical surface tension and is expected to have the higher plaqueretaining capacity. From the Faculté de Médecine Dentaire Université Laval. aProfessor, Department of Orthodontics, Faculty of Dentistry, Université Laval. bProfessor, Department of Prosthodontics, Faculty of Dentistry, Université Laval. cUndergraduate student, Faculty of Dentistry, Université Laval. Reprint requests to: Dr. André Fournier, Faculté de Médecine Dentaire, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4 Copyright © 1998 by the American Association of Orthodontists. 0889-5406/98/$5.00 + 0 8/1/87455
414
The objectives of this investigation are (1) to compare the initial affinity of S. mutans to metal, plastic, and ceramic brackets, (2) to compare the adherence of S. mutans to metal, plastic, and ceramic brackets over time, and (3) to study the effect of saliva on the affinity and adherence of S. mutans to orthodontic brackets. MATERIAL AND METHODS Bacteria and Cultivation Conditions
S. mutans was isolated from the saliva of 48 young adults (age range, 26 to 52 years) on solid trypticase medium containing 3% yeast extract (TSBYA) and stored in aliquots at –20°C as described by Parrot et al.17 Radioactive Labeling of Cells
S. mutans strains were routinely grown in liquid TSBYA. For each milliliter of TSBYA broth, 10 µl of frozen stock of S. mutans and .5 µCi [3H] thymidine (New England Nuclear Corp., Boston, Mass.) were added. The culture was incubated overnight at 37°C, without agitation in an aerobic environment. The purity of the culture was verified with a TSBYA petri dish. The suspension was placed in the centrifuge (Sorvall RCSC with SS-34 rotor) at 7700g for 10 minutes at 4°C and the supernatant was removed. The pellet was washed twice with sterile distilled water and placed in a centrifuge at 7700g for 10 minutes at 4°C. Finally, the pellet was resuspended in a potassium phosphate buffer (l mm, pH 6.0) with 50 mm potassium chlorine, 1 mm calcium chloride, and .01 mm magnesium chloride at a density of approximately 108 cells per ml. The suspension was sonified on ice (Sonifier Cell Disruptor w350, Smithkline Co.) at an intensity of 110 watts for a period of 20 seconds.
Fournier, Payant, and Bouclin
American Journal of Orthodontics and Dentofacial Orthopedics Volume 114, Number 4
415
Fig 1. Initial affinity and adherence of S. mutans to saliva-coated brackets over time. All values represent the average of 12 measurements. Percentage of adherence represents the radioactive counts from brackets/total counts per minute per milliliter of the S. mutans solution × 100%. Time refers to storage time of brackets in distilled water after immersion in S. mutans solution.
Fig 2. Initial affinity and adherence of S. mutans to non–saliva-coated brackets over time. All values represent the average of 12 measurements. Percentage of adherence represents the radioactive counts from brackets per counts per minute per milliliter of the S. mutans solution × 100%. Time refers to storage time of brackets in distilled water after immersion in S. mutans solution.
To measure radioactivity, samples (.l ml) were added to 5 ml of a scintillation cocktail and radioactivity was counted with a liquid scintillation counter (model LS 7500, Beckman Instruments).
Table I.
Preparation of Clarified Saliva
Paraffin-stimulated saliva was collected on ice from six individuals. The saliva was clarified by centrifugation at 12,000g for 10 minutes at 4°C and heated to 60°C for 30 minutes as described by Nesbitt et al.18 Preparation of the Orthodontic Brackets
Brackets were made from either plastic, porcelain, or metal. All brackets come from a commercial brand. Metal brackets were Ormco mini-diamond brackets welded on mesh pads. Plastic brackets were Ormco spirit brackets without silanated bases and without steel reinforced slot. Ceramic brackets were from Cerum Ortho Organisers with mechanical mesh (without silanated bases). Saliva-coated brackets were placed in a scintillation vial and immersed in 2 ml of clarified saliva for 2 hours with agitation at 20°C. Non–salivacoated brackets were placed in a scintillation vial and immersed in 2 ml of distilled water for 2 hours with agitation at 20°. Adherence of S. mutans to Brackets
Each bracket was placed in a scintillation vial and immersed in 2 ml of a labeled S. mutans suspension for 6 hours without agitation at 20°C in an aerobic environment. After this period of time, the brackets were rinsed three times in 5 ml of sterile distilled water and were immersed in 5 ml of sterile distilled water for 24, 48, or 72 hours at 20°C in an aerobic environment
Affinity of S. mutans to saliva-coated brackets
Metal Plastic Ceramic
Metal
Plastic
Ceramic
— S S
S — N.S.
S N.S. —
without agitation. After their respective period of immersion, the brackets were transferred to scintillation vials with 5 ml scintillation liquid; the radioactivity was counted with the scintillation counter. Calculations and Statistics
The average of 12 measurements was calculated for each parameter. The mean radioactive counts were divided by the total counts per minute per milliliter of the S. mutans suspension solution. From this calculation, the percentage of adherence of S. mutans was obtained. With the use of a Statview program, differences between groups were tested for statistical significance (P < .05) by use of an analysis of variance (ANOVA). A Fisher posthoc test was further applied to locate the significant differences. RESULTS Affinity of S. mutans for Metal, Plastic, and Porcelain Brackets
Saliva-coated brackets (Table I and II and Fig 1). The initial affinity of S. mutans to metal brackets was significantly lower (P < .05) than the affinity to plastic brackets and porcelain brackets. No significant difference was found between porcelain and plastic brackets. At time 24, 48, and 72 hours, there was no significant
416
Fournier, Payant, and Bouclin
Table II.
American Journal of Orthodontics and Dentofacial Orthopedics October 1998
Analysis of variance of initial affinity of S. mutans to saliva-coated brackets Group
Count
Mean
SD
Metal Plastic Ceramic
11 11 11
1325 1430 3153
325 227 1111
Source Between subjects Within subjects Treatments Residual Total
df
Sum of Squares
Mean Square
10 22 2 20 32
4489181,303 32591077,027 23160950,622 9430126,404 37080258,33
448918,13 1481412,592 11580475,311 471506,32
F-test
P-value
,303
,9726
24,561
,0001
SD, Standard deviation. df, Degrees of freedom.
statistical difference among the adherence of S. mutans to metal, plastic, or porcelain brackets. Non–saliva-coated brackets (Fig 2). The initial affinity of S. mutans to porcelain brackets was significantly higher that the affinity to metal brackets and to plastic brackets. After 24 and 48 hour storage time, the adherence of S. mutans to metal and plastic brackets was again statistically significantly lower than to porcelain brackets. After 72 hour storage time, the adherence of S. mutans to metal was significantly lower than to porcelain and plastic brackets. No significant difference was found between porcelain and plastic brackets after 72 hours in distilled water. Effect of Storage Time on Adherence to Brackets
Saliva-coated brackets (Fig 1). The initial affinity of S. mutans to saliva-coated metal, porcelain, and plastic brackets was significantly higher than the adherence to the same product after 24-hour, 48-hour, and 72-hour storage times. There was no significant difference among 24-hour, 48-hour, and 72 hour storage times. Non–saliva-coated brackets (Fig 2). For non–saliva-coated metal, plastic, and porcelain brackets, the initial affinity was statistically significantly higher than the adherence of the same product at 24-hour, 48-hour, and 72-hour storage times. There was, however, no significant difference between 24 hours and 48 hours for all products. The adherence at 72 hours was lower than after 24 and 48 hours for all products. Effect of Saliva-coating on Adherence
For metal, plastic, and porcelain brackets, non–saliva-coated samples showed a significantly greater initial affinity and a greater adherence after 24-hour and 48hour storage times than saliva-coated samples. No statistically significant difference was observed at 72-hour
storage time for all products among coated and noncoated samples. DISCUSSION
The main objective of this study was to determine if the material used for orthodontic brackets has an effect on bacterial affinity to these appliances in a situation that simulates that of clinical use (except for the temperature, which was not the body temperature, only for convenience). For that same reason, we preferred to collect a pool of S. mutans rather than to use an isolated strain of S. mutans. We think that isolated strains are more susceptible to genetic mutations, and it was not necessary in our experiment to use strains from which the genetic code has been studied. One could also question our use of distilled water rather than a growth medium to study the adherence of S. mutans to the specimen. This question is of clinical importance, but we focused our attention more on the elution phenomenon than on the growth of the bacteria. In fact, we do not want cell division to occur because it would then be impossible to measure unlabeled bacteria. Our findings seem to indicate that adherence of S. mutans is weaker on metal than plastic and ceramic brackets. In our experimental design, we assumed that the surface of all the brackets were the same, which we know is not absolutely true. This fact may partly explain why our findings differ from what we should expect from an analysis of exact dimension samples from raw material. However, our experimental surface (with the exception of the portion of the bracket that binds to the tooth) is equivalent to the surface encountered in a clinical situation. Our findings also seem to indicate that the presence of saliva tends to lower the adherence of S. mutans to each of the materials tested. These results are in accordance with those of Suljak et al19 who reported that precoating composites with saliva led to decreased
Fournier, Payant, and Bouclin
American Journal of Orthodontics and Dentofacial Orthopedics Volume 114, Number 4
binding of viable cells of Streptococcus sanguis and Streptococcus salivarius. The decreased adherence may result from an alteration in the chemical composition at the surface of the composite. A deposition of carbon nitrogen and oxygen onto composite material has been detected by Auger analysis after a 2-hour incubation in the mouth.20 The presence of histatins and lyzozymes in saliva, which possess exceptional antibacterial activities, may also contribute to the decreased adhesion of S. mutans to composites.21
4.
5. 6. 7.
8. 9.
CONCLUSION
10.
The above results seems to indicate that because of their lower affinity, metal brackets present a lower potential for bacterial accumulation than plastic and ceramic brackets. However, because we found no statistical difference in adherence over time, it is difficult to make a clear assessment that metal brackets have a lower cariogenic effect on the teeth than plastic and ceramic brackets. Also many parameters have not been taken into account in this experiment. To mention a few, there is the form, size, and position of the brackets, the presence or absence of a gingival hook, prophylaxis, etc.
11.
12.
13.
14. 15. 16.
17. 18.
REFERENCES 1. Rutter PR, Abbott A. A study of the interaction between oral streptococci and hard surfaces. J Gen Microbiol 1978;105:219-26. 2. Larsson K, Glantz PO. Microbial adhesion to surfaces with different surface charges. Acta Odontol Scand 1981;39:79-82. 3. Minagi S, Miyake Y, Inagaki K, Tsum H, Suginaka H. Hydrophobic interaction in
19. 20. 21.
417
Candida albicans and Candida tropicalis adherence to various denture base resin materials. Infect Immun 1985;47:11-4. Van Pelt AW, Weerkamp AH, Uyen MHWJC, Busscher HJ, DeJong HP, Arends J. Adhesion of Streptococcus sanguis CH3 to polymers with different surface free energies. Appl Envir Microbiol 1985;49:1270-5. Satou J, Fukunaga A, Satou N, Shintani H, Okuda K. Streptococcal adherence on various restorative materials. J Dent Res 1988;67:588-91. Gorelick L, Geiger AM, Gwinnet AJ. Incidence of spot formation after bonding and banding. Am J Orthod 1982;81:93-8. Ogaard B. Prevalence of white spot lesions in 19 year olds: a study on untreated and orthodontically treated persons 5 years after treatment. Am J Orthod Dentofacial Orthop 1989;96: 423 -7. Balenseifen JW, Madonia JV. Study of dental plaque in orthodontic patients. J Dent Res 1970;49:320-4. Menzaghi N, Saletta M, Garattini G, Brambilla E, Strohmenger L. Changes in the yeast oral flora in patients in orthodontic treatment. Prev Assist Dent 1991;17:26-30. Rosenbloom RG, Tinanoff N. Salivary Streptococcus mutans levels in patients before, during and after orthodontic treatment. Am J Orthod Dentofacial Orthop 1991;100:35-7. Forsberg CM, Brattström V, Maimberg 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. Saemundsson SR, Bergmann H, Magnúsdóttir MO, Holbrook WP. Dental caries and Streptococcus mutans in a rural child population in Iceland. Scand J Dent Res 1992; 100:299-303. Sansone C, Van Houte J, Jodhipura K, Kent R, Margolis,HC. The association of mutans streptococci and non-mutans streptococci capable of acidogenesis at low pH with dental caries on enamel and root surfaces. J Dent Res 1993;72:50816. Eliades T, Viazis AD, Eliades G. Bonding of ceramic brackets to enamel: morphologic and structural considerations. Am J Orthod Dentofacial Orthop 1991;99:369-75. Eliades T, Viazis AD, Lekka M. Failure mode analysis of ceramic brackets bonded to enamel. Am J Orthod Dentofacial Orthop 1993;104:21-6. Eliades T, Eliades G, Brantley WA. Microbial attachment on orthodontic appliances: I. Wettability and early pellicle formation on bracket materials. Am J Orthod Dentofacial Orthop 1995;99:351-75. Parrot M, Dréan MF, Trahan L, Lavoie MC. Incidence of bacteriocinogeny among fresh isolates of Streptococcus mutans. Can J Microbiol 1990;36;507-9. Nesbitt WE, Doyle RJ, Taylor KG. Hydrophobic interaction and the adherence of Streptococcus sanguis to hydroxyapatite. Infect and Immun 1982;38:637-44. Suljak JP, Reid G, Wood SM, McConnell RJ, Van der Mei HC, Busscher HJ. Bacterial adhesion to dental amalgam and three resin composites. J Dent 1995;23:171-6. Skjorland KK. Auger analysis of integuments formed on different dental filling materials in vivo. Acta Odontol Scand 1982;40:129-34. Schenkels L, Veerman E, Nieuw Amerongen A. Biochemical composition of human saliva in relation to other mucosal fluids Crit Rev Oral Biol Med 1995;6:161-75.