Influence of the Topical Application of Fluoride on the In Vitro Adhesion of Fissure Sealants T. Low,* J. A. VON FRAUNHOFER,t and G. B. WINTER
Department of Children's Dentistry and Department of Dental Materials, Institute of Dental Surgery, London, England
The adhesion of four polymeric sealant materials to enamel treated with a topical application of fluoride has been assessed by tensile bond strength tests. The ultraviolet light-activated resin, Nuva Seal, was found to bond adequately to stannous fluoride-treated teeth. The tensile bond strength of Espe 71730, Alpha Seal, and Epoxylite 9075 to enamel was reduced by treatment of the enamel with stannous fluoride. Treatment of the etched enamel with acidulated phosphate fluoride reduced the bond strength of all four fissure sealants. Numerous clinical studies have been conducted in the past, and many are still in progress, to determine the effectiveness of fissure sealing as a caries preventive measure. A sealant retention rate of 40 to 90% during periods of up to two years' duration has been reported for the various sealant materials. However, one study conducted to investigate the effectiveness of fissure sealing in a public health program carried out under normal dental service conditions in schools found a total retention rate of 83.2%, with complete retention being found for 39% of the teeth.1 The onset of caries in unsealed teeth is usually associated with the loss of the sealant coating. Furthermore, the possibility that etching of the enamel surface with concentrated acid may predispose the enamel to the development of caries has been raised by some workers,2 although other studies have indicated that acid-etched enamel will be remineralized by saliva.3'4 Clearly, an additional method of protection of the sealed tooth surface after loss of its sealant coating would be desirable. Received for publication June 20, 1975. Accepted for publication June 11, 1976. * Present address: Department of Children's Dentistry, Faculty of Dentistry, University of Malaya, Kuala Lumpur. t For reprints.
The topical application of fluoride agents either before or at some time during fissure sealing would seem to be an appropriate approach to the problem. Topical application of neutral sodium fluoride, acidulated phosphate fluoride, or stannous fluoride before acid etching has been found to be unsuitable.2'56 The incorporation of fluoride agents into the etching solution seems to be feasible from scanning electron microscope (SEM) studies,2 but tensile bond strength tests have shown that the bond strength is reduced considerably by the procedure.7 Etched enamel has been shown to take up a much higher quantity of topically applied fluoride than unetched enamel.2'8'9. Furthermore, the uptake of fluoride by the surface enamel is a function of the concentration of the applied fluoride and the time of contact between the fluoride agent and enamel. The coating of the etched enamel surface with a sealant after topical application of fluoride therefore would provide the right environment to ensure maximum uptake of fluoride by the enamel. Evidence on this approach based on SEM studies has not been encouraging,2 10 and there are few experimental data from bond strength studies using the currently available sealant materials. In a previous limited study, Nuva Seal was found to adhere significantly better to etched enamel treated with stannous fluoride before sealing.5 This article reports on the effect of the topical application of fluoride treatment of etched enamel on the bond strength of four polymneric sealant materials to human enamel.
Materials and Methods The materials used in this study are given in Table 1. The acid-conditioning agents used were those provided by the manufacturer except in the case of Espe 71730 where no con17
Downloaded from jdr.sagepub.com at FLORIDA INTERNATIONAL UNIV on July 12, 2015 For personal use only. No other uses without permission.
J
LOW, VON FRAUNHOFER, AND WINTER
18
Dent Res
January 1977
TABLE 1 FISSURE SEALANTS INVESTIGATED Material
Supplier
Nuva Seal Alpha Seal Espe 71730 Epoxylite 9075
L. D. Caulk Ltd., York, Pa Amalgamated Dental, UK Espe GmbH, Ger Lee Pharmaceuticals, South El Monte, Ca
ditioning agent was supplied. The conditioning agent used for Espe 71730 was 50% phosphoric acid containing 7% acid oxide. Materials were cured by exposure to an ultraviolet light source, a Spectroline Lamp* for one minute. For Alpha Seal, a 60-second exposure was found to be insufficient and the fissure sealant was exposed to the ultraviolet light source until the material had set, as determined by a straight probe. This usually took several minutes although for the other ultraviolet lightpolymerizable materials, Nuva Seal and Espe 71730, the polymerization times were consistently 45 and 60 seconds, respectively. This suggests that the Spectroline Lamp was less effective than a Nuva Light for this class of material, but the latter was not available for this study. Nuva Seal was included in this study because tensile bond strength tests on recent batches of material gave a bond strength much greater than reported previously.'" Thirty teeth freshly extracted for orthodontic reasons were prepared using the method described by Williams, von Fraunhofer, and Winter'2 for each fissure sealant. The teeth were etched and separated into three groups of
t
Instron Universal
Availability
Ultraviolet light Ultraviolet light Ultraviolet light Chemical
Commercial Commercial Research Commercial
ten teeth each. One group of teeth was then treated with an acidulated phosphate fluoride solution (Rafluor Topical Solutiont) for four minutes. The second group was treated with freshly prepared 8% stannous fluoride for four minutes. The third group received no fluoride treatment and served as the control. Test specimens for determining the tensile bond strength of fissure sealant to enamel in the three groups of teeth were prepared using the method described previously.513 The prepared test specimens were stored in tap water at 37 + IC seven days. After the lapse of this storage period, the test specimens were mounted on a constant strain testing machine+ and load was applied to a cross-head speed of 0.5 cm/min until the sealant separated from the tooth. The bond strength was then calculated from the load at failure.
Results The mean tensile bond strengths and their standard deviations recorded for each sealant material are given in Table 2 and a statistical analysis using the student's t test is given in Table 3. Discussion Treatment of etched enamel with acidulated phosphate fluoride reduced the tensile
* Black Light Eastern Co., New York, NY. t Pascal Corp., Inc., Seattle, Wa.
Canton, Ma:
Curing Method
Testing Machine, Instron Corp.,
TABLE 2 TENSILE BOND STRENGTH (X + SD) OF THE FOUR FISSURE SEALANTS Tensile Bond Strength in kg Cm-2
MtIaterial
Nuva Seal Alpha Seal Espe 71730 Epoxylite 9075
Control
81.8 39.1 59.3 41.4
+ ± + +
18.9 13.6 21.6 19.0
SnF, Treated 87.1 ± 23.7 28.8 + 16.5 38.1 ± 16.7 16.8 + 9.1
APF Treated
37.4 30.8 24.1 22.8
+ + ± ±
18.9 8.9 8.3 9.2
N\ote: APF, acidulated phosphate fluoride. Downloaded from jdr.sagepub.com at FLORIDA INTERNATIONAL UNIV on July 12, 2015 For personal use only. No other uses without permission.
19
TOPICAL APPLICATION OF FLUORIDE & ADHESION
Vol. 56 No. I
TABLE 3 STATISTICAL ANALYSIS OF THE DIFFERENCES IN TENSILE BOND STRENGTH RESULTING FROM DIFFERENT FLUORIDE TREATMENTS Control:
SnF2 Material
Treated
Nuva Seal Alpha Seal Espe 71730 Epoxylite 9075
NS NS PS S
Control: APF SnF2 APF Treated Treated:Treated
HS NS HS PS
HS NS PS NS
Note: HS, highly significant (P
Department of Children's Dentistry and Department of Dental Materials, Institute of Dental Surgery, London, England
The adhesion of four polymeric sealant materials to enamel treated with a topical application of fluoride has been assessed by tensile bond strength tests. The ultraviolet light-activated resin, Nuva Seal, was found to bond adequately to stannous fluoride-treated teeth. The tensile bond strength of Espe 71730, Alpha Seal, and Epoxylite 9075 to enamel was reduced by treatment of the enamel with stannous fluoride. Treatment of the etched enamel with acidulated phosphate fluoride reduced the bond strength of all four fissure sealants. Numerous clinical studies have been conducted in the past, and many are still in progress, to determine the effectiveness of fissure sealing as a caries preventive measure. A sealant retention rate of 40 to 90% during periods of up to two years' duration has been reported for the various sealant materials. However, one study conducted to investigate the effectiveness of fissure sealing in a public health program carried out under normal dental service conditions in schools found a total retention rate of 83.2%, with complete retention being found for 39% of the teeth.1 The onset of caries in unsealed teeth is usually associated with the loss of the sealant coating. Furthermore, the possibility that etching of the enamel surface with concentrated acid may predispose the enamel to the development of caries has been raised by some workers,2 although other studies have indicated that acid-etched enamel will be remineralized by saliva.3'4 Clearly, an additional method of protection of the sealed tooth surface after loss of its sealant coating would be desirable. Received for publication June 20, 1975. Accepted for publication June 11, 1976. * Present address: Department of Children's Dentistry, Faculty of Dentistry, University of Malaya, Kuala Lumpur. t For reprints.
The topical application of fluoride agents either before or at some time during fissure sealing would seem to be an appropriate approach to the problem. Topical application of neutral sodium fluoride, acidulated phosphate fluoride, or stannous fluoride before acid etching has been found to be unsuitable.2'56 The incorporation of fluoride agents into the etching solution seems to be feasible from scanning electron microscope (SEM) studies,2 but tensile bond strength tests have shown that the bond strength is reduced considerably by the procedure.7 Etched enamel has been shown to take up a much higher quantity of topically applied fluoride than unetched enamel.2'8'9. Furthermore, the uptake of fluoride by the surface enamel is a function of the concentration of the applied fluoride and the time of contact between the fluoride agent and enamel. The coating of the etched enamel surface with a sealant after topical application of fluoride therefore would provide the right environment to ensure maximum uptake of fluoride by the enamel. Evidence on this approach based on SEM studies has not been encouraging,2 10 and there are few experimental data from bond strength studies using the currently available sealant materials. In a previous limited study, Nuva Seal was found to adhere significantly better to etched enamel treated with stannous fluoride before sealing.5 This article reports on the effect of the topical application of fluoride treatment of etched enamel on the bond strength of four polymneric sealant materials to human enamel.
Materials and Methods The materials used in this study are given in Table 1. The acid-conditioning agents used were those provided by the manufacturer except in the case of Espe 71730 where no con17
Downloaded from jdr.sagepub.com at FLORIDA INTERNATIONAL UNIV on July 12, 2015 For personal use only. No other uses without permission.
J
LOW, VON FRAUNHOFER, AND WINTER
18
Dent Res
January 1977
TABLE 1 FISSURE SEALANTS INVESTIGATED Material
Supplier
Nuva Seal Alpha Seal Espe 71730 Epoxylite 9075
L. D. Caulk Ltd., York, Pa Amalgamated Dental, UK Espe GmbH, Ger Lee Pharmaceuticals, South El Monte, Ca
ditioning agent was supplied. The conditioning agent used for Espe 71730 was 50% phosphoric acid containing 7% acid oxide. Materials were cured by exposure to an ultraviolet light source, a Spectroline Lamp* for one minute. For Alpha Seal, a 60-second exposure was found to be insufficient and the fissure sealant was exposed to the ultraviolet light source until the material had set, as determined by a straight probe. This usually took several minutes although for the other ultraviolet lightpolymerizable materials, Nuva Seal and Espe 71730, the polymerization times were consistently 45 and 60 seconds, respectively. This suggests that the Spectroline Lamp was less effective than a Nuva Light for this class of material, but the latter was not available for this study. Nuva Seal was included in this study because tensile bond strength tests on recent batches of material gave a bond strength much greater than reported previously.'" Thirty teeth freshly extracted for orthodontic reasons were prepared using the method described by Williams, von Fraunhofer, and Winter'2 for each fissure sealant. The teeth were etched and separated into three groups of
t
Instron Universal
Availability
Ultraviolet light Ultraviolet light Ultraviolet light Chemical
Commercial Commercial Research Commercial
ten teeth each. One group of teeth was then treated with an acidulated phosphate fluoride solution (Rafluor Topical Solutiont) for four minutes. The second group was treated with freshly prepared 8% stannous fluoride for four minutes. The third group received no fluoride treatment and served as the control. Test specimens for determining the tensile bond strength of fissure sealant to enamel in the three groups of teeth were prepared using the method described previously.513 The prepared test specimens were stored in tap water at 37 + IC seven days. After the lapse of this storage period, the test specimens were mounted on a constant strain testing machine+ and load was applied to a cross-head speed of 0.5 cm/min until the sealant separated from the tooth. The bond strength was then calculated from the load at failure.
Results The mean tensile bond strengths and their standard deviations recorded for each sealant material are given in Table 2 and a statistical analysis using the student's t test is given in Table 3. Discussion Treatment of etched enamel with acidulated phosphate fluoride reduced the tensile
* Black Light Eastern Co., New York, NY. t Pascal Corp., Inc., Seattle, Wa.
Canton, Ma:
Curing Method
Testing Machine, Instron Corp.,
TABLE 2 TENSILE BOND STRENGTH (X + SD) OF THE FOUR FISSURE SEALANTS Tensile Bond Strength in kg Cm-2
MtIaterial
Nuva Seal Alpha Seal Espe 71730 Epoxylite 9075
Control
81.8 39.1 59.3 41.4
+ ± + +
18.9 13.6 21.6 19.0
SnF, Treated 87.1 ± 23.7 28.8 + 16.5 38.1 ± 16.7 16.8 + 9.1
APF Treated
37.4 30.8 24.1 22.8
+ + ± ±
18.9 8.9 8.3 9.2
N\ote: APF, acidulated phosphate fluoride. Downloaded from jdr.sagepub.com at FLORIDA INTERNATIONAL UNIV on July 12, 2015 For personal use only. No other uses without permission.
19
TOPICAL APPLICATION OF FLUORIDE & ADHESION
Vol. 56 No. I
TABLE 3 STATISTICAL ANALYSIS OF THE DIFFERENCES IN TENSILE BOND STRENGTH RESULTING FROM DIFFERENT FLUORIDE TREATMENTS Control:
SnF2 Material
Treated
Nuva Seal Alpha Seal Espe 71730 Epoxylite 9075
NS NS PS S
Control: APF SnF2 APF Treated Treated:Treated
HS NS HS PS
HS NS PS NS
Note: HS, highly significant (P
