ORIGINAL ARTICLES
Evaluation of fluoride release from an orthodontic bonding system Samir E. Bishara, DDS, BDS, D. Orth., MS,* Edward J. Swift, Jr., DMD, MS,** and Daniel C. N. Chan, DDS, MS*** Iowa City, Iowa, and San Antonio, Texas
Decalcification around brackets is sometimes observed after orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed in an attempt to reduce the frequency and severity of decalcification. This study evaluated, in vitro, a light-activated, fluoride-releasing composite resin adhesive, FluorEver OBA. The findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. A mean of 2.6 ppm was released on day 1, decreasing to a mean of 0.42 ppm by day 2 and to 0.04 ppm by day 43. The clinical implications of these findings are discussed. (AMJ ORTHOD DENTOFACORTHOP 1991;100:106-9.)
I n their attempt to minimize the incidence of decalcification around orthodontic appliances, orthodontists have always emphasized the need for good oral hygiene. The role of fluoride in preventing caries has been well documented, t'2 As a result, the application of fluoride solutions topically to the etched tooth during bonding and the use of fluoride rinses during treatment have been suggested as means of reducing enamel decalcification. 3 Since decalcification around orthodontic brackets and bands is a particularly frustrating and all-toocommon problem, 4 several fluoride-releasing cements have been developed and used clinically to reduce decalcification. 5-7 In discussing fluoride-releasing materials, Gwinnett and Ceen 8 recommended that fluoride availability should be independent of patient cooperation and that the fluoride ion should diffuse or dissolve over a prolonged period. In addition, it would be beneficial if the fluoride ion release were site specific to those areas most susceptible to demineralization, namely, adjacent to bonded orthodontic brackets. Fluoride-releasing resins have been studied for more than 30 years. 9t3 Underwood et al. t4 examined in vivo, the durability and caries-inhibition properties of a fluoride-exchanging resin for 60 days after bonding. They concluded that the fluoride-exchanging resin has *Professor, Department of Orthodontics, College of Dentistry, The University of Iowa. **Assistant professor, Department of Operative Dentistry, College of Dentistry, The University of Iowa. ***Assistant professor, Division of Operative Dentistry, Department of Restorative Dentistry, The University of Texas Heahh Science Center. 811123996
106
a caries-preventive potential and reduces the incidence of very early demineralization of enamel surrounding orthodontic appliances. Commercial products, including composite resin orthodontic adhesives, have beerl introduced for clinical use. A fluoride-containing orthodontic bonding system, was recently removed from the market because of an increased incidence of bond failures. The resin initially released fluoride in very small amounts, with no measurable fluoride release detected after 3 days. t6 Another composite resin, FluorEver OBA (MacroChem Corporation, Billerica, Mass.), has recently become available. Accm'ding io the manufacturer, fluoride ions encapsulated in the resin are released by a diffusion or dissolution mechanism. In a studyby Sonis and Snell, 15a decrease in the amount of decalcification around orthodontic brackets bonded with FluorEver OBA was reported. They also reported that the fluoridereleasing resin provided bracket retention rates similar to those of conventional orthodontic bonding systems over a 2-year period. Since FluorEver orthodontic adhesive is light activated, metal brackets may not allow sufficient light penetration for'adequate conversion of composite. A recent comprehensive study by Chan et al.'7 evaluated various properties of FluorEver OBA, including fluoride release, tensile bond strength, and polymerization through metal brackets. They concluded that the tensile bond strength of the fluoride-releasing resin was significantly less than the conventional resin at 2 and 42 days after bonding. In addition, Chan et al.t7 found that the composite resins were harder in areas outside the brackets, regardless of the exposure time. There is presently little information on the concen-
Evaluation of fluoride release from a bonding system
Volume tO0 Number 2
Fluoride
release
following
bonding
FluorEver
and
of orthodontic
brackets
107
with
Concise
275 " 2 50 "
225 " 200-
E
1 75 -
"6
•
- FluorEver
•
- Concise
t 50 •
1 25 -
100-
0 75 -
050"
025 -
0CO-
t
L . _ ,
m
~
~
=
=
-_
_-
=
DAYS
Fig.
1. Fluoride ion retease from FluorEver OBA and Concise between days 1 and 43.
tration o f fluoride ion released from these adhesives from around and under orthodontic brackets. The purpose o f this report is to provide additional details on the quantity o f fluoride ions released, in vitro, from under orthodontic brackets bonded with FluorEver OBA.
ion-sensitive electrode connected to a calibrated SA 270 concentration, meter (Orion Research). The samples were transferred to test tubes containing 4 ml fresh deionized water.
MATERIALS AND METHODS Sample preparation
The data were subjected to analysis of variance (ANOVA) and Duncan's multiple range test to detect differences in fluoride ion concentration by material and time. '8 Statistical significance was predetermined at the 0.05 level of confidence.
Bonding sites on the buccal surfaces of 40 extracted teeth were etched according to the manufacturer's directions with 37% phosphoric acid gel. Metal orthodontic brackets were bonded to 20 teeth with FluorEver OBA that was polymerized for 30 seconds with visible light. Brackets were attached to the other teeth with chemical-cure Concise Orthodontic Bonding System (3M Dental Products Division, St. Paul, Minn.). The teeth were stored at 37 ° C in individual capped polystyrene test tubes containing 4 ml deionized water.
Fluoride release Fluoride ion measurements were made at 24-hour intervals for the first 7 days of the experiment. Thereafter, fluoride ion concentrations were measured every 72 hours for 5 weeks. Teeth were transferred to fresh media 24 hours before each scheduled measurement during those final 5 weeks. Each sample was removed from the test tube and rinsed with 1 ml deionized water, and the rinse water was collected in the test tube. An equal volume (5 ml) of TISAB II (Orion Research, Cambridge, Mass.) was added to each test tube. Fluoride ion concentrations were measured with a No. 9609 fluoride
Statistical analysis
FINDINGS Comparisons of fluoride ion release between the two adhesives For days 1 and 2, the average amount o f fluoride ion released by FluorEver O B A was 2.6 ± 0.85 parts per million (ppm) or 683.8 ± 223.6 i~g/ml and 0.42 ± 0.16 ppm or 1"10.5 ± 42.1 p.g/mi as compared with 0.03 ± 0.01 p p m (7.9 ± 2.6 p.g/ml) and 0.01 ± 0 ppm (2.6 ± 0 Ixg/ml), respectively, for Concise (Table I and Fig. 1). The differences were significant at the 0.0001 level of confidence. After the second day, no measurable fluoride ions were released in the solution containing the teeth bonded with Concise. The source of the fluoride ions in the Concise group is thought to be either the enamel surface left exposed around the bonded orthodontic brackets or traces present in the adhesive used.
108 Bishara, Swift, and Chan
Am. J. Orthod. Dentofac. Orthop. August 1991
Table I. Basic statistics and results of analysis of variance comparing fluoride ion release of two orthodontic adhesives between 1 and 43 days, measured as parts per million
FhtorEver OBA Day
x
1
2.60 0.42 0.20 0.17 0.15 0.12 0.08 0.09 0.09 0.09 0.09 O.I0 O.lO 0.08 0.07 0.07 0.06 0.05 0.04
2 3 4 5 6 7 l0 13 16 19 22 25 28 31 34 37 40 43
I
Concise
F
OBA VS.
SD
x
SD
Concise p vahte
0.85 0.16" 0.05** 0.04 0.03 0.03 0.02 0.03 0.04 0.03 0.06 0.06 0.04 0.03 0.03 0.02 0.02 0.01 0.0l
0.03 0.01
0.01 0.00
0.0001 0.0001
x, mean; SD, standard deviation. *Significant differences between days 1 and 2. **Significant differences between days 2 and 3.
Fluoride ion release from FluorEver (Table I and
Fig. 1) The average amount o f fluoride ion released during the first day was 2.6 ± 0.85 ppm (683.8 ± 223.6 p.g/ml). The concentration significantly declined to a o f 0.42 ± 0.16 ppm (110.5 - 4.21 p . g / m l ) o n the second day. Fluoride ion concentration continued to decline significantly by the third day to a ~ of 0.20 --0.05 ppm (52.6 _+ 13.0 ixg/ml). There was a gradual decrease in the fluoride ion concentration from the third to the forty third day o f 0.04 _+ 0.01 ppm (10.5 ± 2.6 Ixg/ml). This decrease was not statistically significant.
DISCUSSION AND CONCLUSIONS Recent studies indicate that the physical properties of FluorEver OBA, as measured by bond strength and microhardness, were not adversely affected b y water storage, t7 However, the tensile bond strength o f FluorEver OBA was significantly less (1/3 to 1/2) than that of the conventional composite a d h e s i v e ) 7.t9 It was also observed that most FluorEver failures were cohesive rather than adhesive, indicating failure within the material) 7
The relatively low tensile bond strength of FluorEver OBA could be the result o f either insufficient light penetration around metal brackets or the addition o f sodium fluoride to the composite resin. Microhardness testing showed that the resin beneath the brackets was softer (i.e., less thoroughly polymerized) than in adjacent a r e a s ) 7 Although some postirradiation hardening would be expected to improve physical properties, it needs to be remembered that underirradiated composites do not attain the same hardness as properly cured c o m p o s i t e s ? °'2~ It has been suggested that the addition o f a chemical catalyst to FluorEver OBA might improve its p e r f o r m a n c e ) 7 The findings from this study indicate that the fluoride ion concentration released from FluorEver OBA declined sharply after 24 hours and continued to decline over the entire 6-week experiment. This pattern was similar to that o f FluorEver restorative material, but the decline in released fluoride concentration from FluorEver O B A was more rapid. 22 The clinical significance o f these low but constant and site-specific fluoride concentrations was not determined by this study. The decrease observed in the incidence o f decalcification ts may be the result o f the availability o f low concentrations o f fluoride ion, or it may be the result o f initial changes in the enamel surface that occurred when the fluoride ion concentration was high. The changes in the enamel surface might be maintained even after the fluoride ion concentration becomes too low to be clinically effective in preventing decalcification. As a result, further investigations are needed to determine the efficacy o f these relatively low concentrations o f fluoride ions released from these resins in reducing demineralization of enamel around orthodontic brackets. Until this is determined, it might be wise to continue to supplement the oral hygiene regimen with fluoride rinses, especially in those cases in which the potential for decalcification is present or is to be expected.
REFERENCES I. Schrotenboer Gtt. Fluoride benefits--after 30 years. J Am Dent Assoc 1981;102:473-4. 2. Carlos JP. The prevention of dental caries: ten years later. J Am Dent Assoe 1982;104:193-7. 3. Bishara SE, Chan D, Abadir EA. The effects on the bonding strength of fluoride application after etching. AMJ ORTHODD ~ TOFACO~THOP 1989;95:259-60. 4. Shannon IL. Preventionof decalcificationin orthodontic patients. J Clin Orthod 1981;15:694-706. 5. Skibell RB, Shannon IL. Addition of stannous fluoride to orthodontic cement. I,,,rrJ ORTItOD1973;I 1:131-5. 6. Sadowsky PL, Retief DH, Bradley EL. Enamel fluoride uptake from orthodontic cement and its effect on demineralization. Ard J ORTIfOD1981;79:523-34.
109
Volume 100 Number 2
Evahtation of fluoride release from a bondh~g system
7. Rezich PM, Panneton MJ, Barkmeier WW. In vitro evaluation of fluoride and non-fluoride releasing orthodontic adhesives on bracket bond strength. J Esthet Dent 1989;1:101-4. 8. Gwinnett JA, Ceen F. Plaque distribution on bonded brackets. AM J OR'rHOD 19.79;75:667-677. 9. Phillips RW, Swartz ML. Effect of certain restorative materials on solubility of enamel. J Am Dent Assoc 1957;54:623-36. 10. Swartz ML, Phillips RW, Norman RD, Elliason S, Rhodes BF, Clark HE. Addition of fluoride to pit and fissure sealants: a feasibility study. J Dent Res 1976;55:757-71. 11. Rawls HR, Zimmerman BF. Fluoride-exchanging resins for caries protection. Caries Res 1983;17:32-43. 12. Temin SC, Csuros Z. Long term fluoride release from a composite restorative. Dent Mater 1988;4:184-6. 13. Cooley RL, Sandoval VA, Bamwell SE. Fluoride release and color stability of a fluoride-containing composite resin. Quintessence lnt 1988;19:899-904. 14. Underwood ML, Rawls HR, Zimmerman BF. Clinical evaluation of a fluoride-exchanging resin as orthodontic adhesive. AM J OR'mOP D.V_Y'roFAcOR'rHoe 1989;96:93-9. 15. Sonis AL, Snell W] An evaluation of a fluoride-releasing, visible light-activated bonding system for orthodontic bracket placement. AM J OR'naODD~,rrOFACORTHOP 1989;95:306-11.
16. Cooley RL, Barkmeier WW, Hicks JL. Fluoride release from orthodontic adhesives. Am J Dent 1989;2:86-8. 17. Chan DCN, Swift EJ Jr, Bishara SE. In vitro evaluation of a fluoride releasing orthodontic resin. J Dent Res 1990;69:!576-9. 18. SAS users guide. Cary, N.C.: SAS Institute, 1985. 19: Kao EC, Peng P, Johnston WM. Deboading orthodontic brackets with fluoride-releasing resin and cement. J Dent Res 1990;69: 210. Abstract No. 809. 20. Leung RL, Adishian SR, Fan PL. Postirradiation comparison of photoactivated composite resins. J Prosthet Dent 1985;54: 645-9. 21. Watts DC, NcNaughton V, Grant AA. The development of surface hardness in visible light-cured posterior composites. J Dent 1986;14:169-74. 22. Swift EJ Jr. Fluoride release from two composite resins. Quintessence Int 1989;20:895-7.
Reprint requests to: Dr. Samir Bishara University of iowa College of Dentistry Department of Orthodontics Iowa City, IA 52242
AAO MEETING CALENDAR
1992--St. Louis, Mo., May 9 to 13, St. Louis Convention Center 1993--Toronto, Canada, May 15 to 19, Metropolitan Toronto Convention Center 1994--Orlando, Fla., May 1 to 4, Orange County Convention and Civic Center 1995--San Francisco, Calif., May 7 to 10, Moscone Convention Center
(International Orthodontic Congress) 1996--Denver, Colo., May 12 to 16, Colorado Convention Center 1997--Philadelphia, Pa., May 3 to 7, PhiladeTphia Convention Center 1998--Dallas, Texas, May 16 to 20, Dallas Convention Center 1999--San Diego, Calif., May 15 to 19, San Diego Convention Center
Evaluation of fluoride release from an orthodontic bonding system Samir E. Bishara, DDS, BDS, D. Orth., MS,* Edward J. Swift, Jr., DMD, MS,** and Daniel C. N. Chan, DDS, MS*** Iowa City, Iowa, and San Antonio, Texas
Decalcification around brackets is sometimes observed after orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed in an attempt to reduce the frequency and severity of decalcification. This study evaluated, in vitro, a light-activated, fluoride-releasing composite resin adhesive, FluorEver OBA. The findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. A mean of 2.6 ppm was released on day 1, decreasing to a mean of 0.42 ppm by day 2 and to 0.04 ppm by day 43. The clinical implications of these findings are discussed. (AMJ ORTHOD DENTOFACORTHOP 1991;100:106-9.)
I n their attempt to minimize the incidence of decalcification around orthodontic appliances, orthodontists have always emphasized the need for good oral hygiene. The role of fluoride in preventing caries has been well documented, t'2 As a result, the application of fluoride solutions topically to the etched tooth during bonding and the use of fluoride rinses during treatment have been suggested as means of reducing enamel decalcification. 3 Since decalcification around orthodontic brackets and bands is a particularly frustrating and all-toocommon problem, 4 several fluoride-releasing cements have been developed and used clinically to reduce decalcification. 5-7 In discussing fluoride-releasing materials, Gwinnett and Ceen 8 recommended that fluoride availability should be independent of patient cooperation and that the fluoride ion should diffuse or dissolve over a prolonged period. In addition, it would be beneficial if the fluoride ion release were site specific to those areas most susceptible to demineralization, namely, adjacent to bonded orthodontic brackets. Fluoride-releasing resins have been studied for more than 30 years. 9t3 Underwood et al. t4 examined in vivo, the durability and caries-inhibition properties of a fluoride-exchanging resin for 60 days after bonding. They concluded that the fluoride-exchanging resin has *Professor, Department of Orthodontics, College of Dentistry, The University of Iowa. **Assistant professor, Department of Operative Dentistry, College of Dentistry, The University of Iowa. ***Assistant professor, Division of Operative Dentistry, Department of Restorative Dentistry, The University of Texas Heahh Science Center. 811123996
106
a caries-preventive potential and reduces the incidence of very early demineralization of enamel surrounding orthodontic appliances. Commercial products, including composite resin orthodontic adhesives, have beerl introduced for clinical use. A fluoride-containing orthodontic bonding system, was recently removed from the market because of an increased incidence of bond failures. The resin initially released fluoride in very small amounts, with no measurable fluoride release detected after 3 days. t6 Another composite resin, FluorEver OBA (MacroChem Corporation, Billerica, Mass.), has recently become available. Accm'ding io the manufacturer, fluoride ions encapsulated in the resin are released by a diffusion or dissolution mechanism. In a studyby Sonis and Snell, 15a decrease in the amount of decalcification around orthodontic brackets bonded with FluorEver OBA was reported. They also reported that the fluoridereleasing resin provided bracket retention rates similar to those of conventional orthodontic bonding systems over a 2-year period. Since FluorEver orthodontic adhesive is light activated, metal brackets may not allow sufficient light penetration for'adequate conversion of composite. A recent comprehensive study by Chan et al.'7 evaluated various properties of FluorEver OBA, including fluoride release, tensile bond strength, and polymerization through metal brackets. They concluded that the tensile bond strength of the fluoride-releasing resin was significantly less than the conventional resin at 2 and 42 days after bonding. In addition, Chan et al.t7 found that the composite resins were harder in areas outside the brackets, regardless of the exposure time. There is presently little information on the concen-
Evaluation of fluoride release from a bonding system
Volume tO0 Number 2
Fluoride
release
following
bonding
FluorEver
and
of orthodontic
brackets
107
with
Concise
275 " 2 50 "
225 " 200-
E
1 75 -
"6
•
- FluorEver
•
- Concise
t 50 •
1 25 -
100-
0 75 -
050"
025 -
0CO-
t
L . _ ,
m
~
~
=
=
-_
_-
=
DAYS
Fig.
1. Fluoride ion retease from FluorEver OBA and Concise between days 1 and 43.
tration o f fluoride ion released from these adhesives from around and under orthodontic brackets. The purpose o f this report is to provide additional details on the quantity o f fluoride ions released, in vitro, from under orthodontic brackets bonded with FluorEver OBA.
ion-sensitive electrode connected to a calibrated SA 270 concentration, meter (Orion Research). The samples were transferred to test tubes containing 4 ml fresh deionized water.
MATERIALS AND METHODS Sample preparation
The data were subjected to analysis of variance (ANOVA) and Duncan's multiple range test to detect differences in fluoride ion concentration by material and time. '8 Statistical significance was predetermined at the 0.05 level of confidence.
Bonding sites on the buccal surfaces of 40 extracted teeth were etched according to the manufacturer's directions with 37% phosphoric acid gel. Metal orthodontic brackets were bonded to 20 teeth with FluorEver OBA that was polymerized for 30 seconds with visible light. Brackets were attached to the other teeth with chemical-cure Concise Orthodontic Bonding System (3M Dental Products Division, St. Paul, Minn.). The teeth were stored at 37 ° C in individual capped polystyrene test tubes containing 4 ml deionized water.
Fluoride release Fluoride ion measurements were made at 24-hour intervals for the first 7 days of the experiment. Thereafter, fluoride ion concentrations were measured every 72 hours for 5 weeks. Teeth were transferred to fresh media 24 hours before each scheduled measurement during those final 5 weeks. Each sample was removed from the test tube and rinsed with 1 ml deionized water, and the rinse water was collected in the test tube. An equal volume (5 ml) of TISAB II (Orion Research, Cambridge, Mass.) was added to each test tube. Fluoride ion concentrations were measured with a No. 9609 fluoride
Statistical analysis
FINDINGS Comparisons of fluoride ion release between the two adhesives For days 1 and 2, the average amount o f fluoride ion released by FluorEver O B A was 2.6 ± 0.85 parts per million (ppm) or 683.8 ± 223.6 i~g/ml and 0.42 ± 0.16 ppm or 1"10.5 ± 42.1 p.g/mi as compared with 0.03 ± 0.01 p p m (7.9 ± 2.6 p.g/ml) and 0.01 ± 0 ppm (2.6 ± 0 Ixg/ml), respectively, for Concise (Table I and Fig. 1). The differences were significant at the 0.0001 level of confidence. After the second day, no measurable fluoride ions were released in the solution containing the teeth bonded with Concise. The source of the fluoride ions in the Concise group is thought to be either the enamel surface left exposed around the bonded orthodontic brackets or traces present in the adhesive used.
108 Bishara, Swift, and Chan
Am. J. Orthod. Dentofac. Orthop. August 1991
Table I. Basic statistics and results of analysis of variance comparing fluoride ion release of two orthodontic adhesives between 1 and 43 days, measured as parts per million
FhtorEver OBA Day
x
1
2.60 0.42 0.20 0.17 0.15 0.12 0.08 0.09 0.09 0.09 0.09 O.I0 O.lO 0.08 0.07 0.07 0.06 0.05 0.04
2 3 4 5 6 7 l0 13 16 19 22 25 28 31 34 37 40 43
I
Concise
F
OBA VS.
SD
x
SD
Concise p vahte
0.85 0.16" 0.05** 0.04 0.03 0.03 0.02 0.03 0.04 0.03 0.06 0.06 0.04 0.03 0.03 0.02 0.02 0.01 0.0l
0.03 0.01
0.01 0.00
0.0001 0.0001
x, mean; SD, standard deviation. *Significant differences between days 1 and 2. **Significant differences between days 2 and 3.
Fluoride ion release from FluorEver (Table I and
Fig. 1) The average amount o f fluoride ion released during the first day was 2.6 ± 0.85 ppm (683.8 ± 223.6 p.g/ml). The concentration significantly declined to a o f 0.42 ± 0.16 ppm (110.5 - 4.21 p . g / m l ) o n the second day. Fluoride ion concentration continued to decline significantly by the third day to a ~ of 0.20 --0.05 ppm (52.6 _+ 13.0 ixg/ml). There was a gradual decrease in the fluoride ion concentration from the third to the forty third day o f 0.04 _+ 0.01 ppm (10.5 ± 2.6 Ixg/ml). This decrease was not statistically significant.
DISCUSSION AND CONCLUSIONS Recent studies indicate that the physical properties of FluorEver OBA, as measured by bond strength and microhardness, were not adversely affected b y water storage, t7 However, the tensile bond strength o f FluorEver OBA was significantly less (1/3 to 1/2) than that of the conventional composite a d h e s i v e ) 7.t9 It was also observed that most FluorEver failures were cohesive rather than adhesive, indicating failure within the material) 7
The relatively low tensile bond strength of FluorEver OBA could be the result o f either insufficient light penetration around metal brackets or the addition o f sodium fluoride to the composite resin. Microhardness testing showed that the resin beneath the brackets was softer (i.e., less thoroughly polymerized) than in adjacent a r e a s ) 7 Although some postirradiation hardening would be expected to improve physical properties, it needs to be remembered that underirradiated composites do not attain the same hardness as properly cured c o m p o s i t e s ? °'2~ It has been suggested that the addition o f a chemical catalyst to FluorEver OBA might improve its p e r f o r m a n c e ) 7 The findings from this study indicate that the fluoride ion concentration released from FluorEver OBA declined sharply after 24 hours and continued to decline over the entire 6-week experiment. This pattern was similar to that o f FluorEver restorative material, but the decline in released fluoride concentration from FluorEver O B A was more rapid. 22 The clinical significance o f these low but constant and site-specific fluoride concentrations was not determined by this study. The decrease observed in the incidence o f decalcification ts may be the result o f the availability o f low concentrations o f fluoride ion, or it may be the result o f initial changes in the enamel surface that occurred when the fluoride ion concentration was high. The changes in the enamel surface might be maintained even after the fluoride ion concentration becomes too low to be clinically effective in preventing decalcification. As a result, further investigations are needed to determine the efficacy o f these relatively low concentrations o f fluoride ions released from these resins in reducing demineralization of enamel around orthodontic brackets. Until this is determined, it might be wise to continue to supplement the oral hygiene regimen with fluoride rinses, especially in those cases in which the potential for decalcification is present or is to be expected.
REFERENCES I. Schrotenboer Gtt. Fluoride benefits--after 30 years. J Am Dent Assoc 1981;102:473-4. 2. Carlos JP. The prevention of dental caries: ten years later. J Am Dent Assoe 1982;104:193-7. 3. Bishara SE, Chan D, Abadir EA. The effects on the bonding strength of fluoride application after etching. AMJ ORTHODD ~ TOFACO~THOP 1989;95:259-60. 4. Shannon IL. Preventionof decalcificationin orthodontic patients. J Clin Orthod 1981;15:694-706. 5. Skibell RB, Shannon IL. Addition of stannous fluoride to orthodontic cement. I,,,rrJ ORTItOD1973;I 1:131-5. 6. Sadowsky PL, Retief DH, Bradley EL. Enamel fluoride uptake from orthodontic cement and its effect on demineralization. Ard J ORTIfOD1981;79:523-34.
109
Volume 100 Number 2
Evahtation of fluoride release from a bondh~g system
7. Rezich PM, Panneton MJ, Barkmeier WW. In vitro evaluation of fluoride and non-fluoride releasing orthodontic adhesives on bracket bond strength. J Esthet Dent 1989;1:101-4. 8. Gwinnett JA, Ceen F. Plaque distribution on bonded brackets. AM J OR'rHOD 19.79;75:667-677. 9. Phillips RW, Swartz ML. Effect of certain restorative materials on solubility of enamel. J Am Dent Assoc 1957;54:623-36. 10. Swartz ML, Phillips RW, Norman RD, Elliason S, Rhodes BF, Clark HE. Addition of fluoride to pit and fissure sealants: a feasibility study. J Dent Res 1976;55:757-71. 11. Rawls HR, Zimmerman BF. Fluoride-exchanging resins for caries protection. Caries Res 1983;17:32-43. 12. Temin SC, Csuros Z. Long term fluoride release from a composite restorative. Dent Mater 1988;4:184-6. 13. Cooley RL, Sandoval VA, Bamwell SE. Fluoride release and color stability of a fluoride-containing composite resin. Quintessence lnt 1988;19:899-904. 14. Underwood ML, Rawls HR, Zimmerman BF. Clinical evaluation of a fluoride-exchanging resin as orthodontic adhesive. AM J OR'mOP D.V_Y'roFAcOR'rHoe 1989;96:93-9. 15. Sonis AL, Snell W] An evaluation of a fluoride-releasing, visible light-activated bonding system for orthodontic bracket placement. AM J OR'naODD~,rrOFACORTHOP 1989;95:306-11.
16. Cooley RL, Barkmeier WW, Hicks JL. Fluoride release from orthodontic adhesives. Am J Dent 1989;2:86-8. 17. Chan DCN, Swift EJ Jr, Bishara SE. In vitro evaluation of a fluoride releasing orthodontic resin. J Dent Res 1990;69:!576-9. 18. SAS users guide. Cary, N.C.: SAS Institute, 1985. 19: Kao EC, Peng P, Johnston WM. Deboading orthodontic brackets with fluoride-releasing resin and cement. J Dent Res 1990;69: 210. Abstract No. 809. 20. Leung RL, Adishian SR, Fan PL. Postirradiation comparison of photoactivated composite resins. J Prosthet Dent 1985;54: 645-9. 21. Watts DC, NcNaughton V, Grant AA. The development of surface hardness in visible light-cured posterior composites. J Dent 1986;14:169-74. 22. Swift EJ Jr. Fluoride release from two composite resins. Quintessence Int 1989;20:895-7.
Reprint requests to: Dr. Samir Bishara University of iowa College of Dentistry Department of Orthodontics Iowa City, IA 52242
AAO MEETING CALENDAR
1992--St. Louis, Mo., May 9 to 13, St. Louis Convention Center 1993--Toronto, Canada, May 15 to 19, Metropolitan Toronto Convention Center 1994--Orlando, Fla., May 1 to 4, Orange County Convention and Civic Center 1995--San Francisco, Calif., May 7 to 10, Moscone Convention Center
(International Orthodontic Congress) 1996--Denver, Colo., May 12 to 16, Colorado Convention Center 1997--Philadelphia, Pa., May 3 to 7, PhiladeTphia Convention Center 1998--Dallas, Texas, May 16 to 20, Dallas Convention Center 1999--San Diego, Calif., May 15 to 19, San Diego Convention Center
