The Effect of Metal/Fluoride Complexes on Fluoride Uptake and Caries-like Lesion Formation in Enamel BRIAN I1. CLARKSON
Dows Institute of Dental Research,
iow1a Citj, Iowao 52242. USA
College of )entistrv, The t TniVers1ty of Iozwa,
Pretreatment of enamiel with TiCl, and ZrOCL2-8H20 solutions prior to APF applicationi was shown to increase fluoride uptake and reduce caries-like lesion formation to a greater (-xtent than APF alonc. The increase in fluoridc ufptake by c?anel was not solely due to the low p1h of the Pretreatment solution.5. J Dent Res 57(7-8):784-789, July-August 1978.
Polvyalent metal ion salt solutions have been used as enamel pretreatment agents and have been found to enhance the fluoride uptake from acidulated phosphate fluoride (APF). It was suggested that this was because of their ability to form strong complexes with fluoride w-hile simultaneously binding with hydroxapatite. '2 Two further studies, in which rat molar teeth were pretreated with aluminum and titanium prior to fluoride application, showed increased fluoride uptake and decreased enamel solubility, but no effect on dental caries was noted.3'4 In this present study, a dual experimental approach was adopted which enabled additional information to be obtained concerning the caries preventive effect of metal/fluoride complexes. First, the fluoride concentration in enamel was determined after pretreatment with the titanium and zirconium salt solutions followed by an APF application. Second, the effect of these elevated fluoride levels on the formation of caries-like lesions in the acidified gel system5 was investigated. These caries-like lesions appear indistinguishable from natural enamel caries with respect to their detailed histopathology when viewed in polarized
light.6-8 Received for publication September 15, 1977. Accepted for publication January 18, 1978. *Analar grade, British Drug House Ltd., Dorset,
Materials and Methods PREPARATION OF TEETH.-All the human premolar teeth being used in the experiments were subjected to the same initial investigation, preparation, and storage.9 Teeth exhibiting cracks, hypoplastic areas, or caries on buccal surfaces were discarded. The remainder were sectioned longitudinally into halves through the buccal/lingual axis. The halves were painted with a colored acid-resistant varnish leaving two small windows of exposed enamel (6 mm2) on the buccal surface. The teeth were then divided into groups corresponding to the number of pretreatments to be given. Each group contained 6 teeth which gave a total of 12 control and 12 test enamel windows. FLUORIDE SOLUTION.-APF contained 1.23% F(w/v) as NaF and HF in 0.1 M orthophosphoric acid (pH 3.2). METAL SALT SOLUTIONS.-Solutions of titanium trichloride (TiC13) and zirconyl chloride (ZrOGl2.8H20)* were prepared at the following concentrations: 0.35 M (pH 1.1) and 0.15 AM (pH 1.2) respectively. TREATMENT OF TEETH.-One half of the tooth (test) received a 2-minute pretreatment followed by a 2-minute application of APF solution; the corresponding half (control) received a 2-minute application of APF. To establish the effect of the acidity of the metal salt solutions on fluoride uptake a series of experiments was devised in which halves of teeth were pretreated with acids of similar pH's to that of the metal salt solutions. Six teeth were prepared for each experiment. The control half of each tooth received a 2minute application of an acid and the test half received a -2-minute application of a metal salt solution. Both were followed by a 2-minute application of APF. WASHING PROCEDURE.-At the completion of the APF treatments, the experimental and control halves of teeth were each washed sepa-
784 Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
METAL/FL UORIDE COMPLEXES & CARIES
Vol. 57 No. 7-8
other metal ions in biological specimens.14,15 For use in these analyses, 12 teeth were selected after microscopic examination and the occlusal and root surfaces were varnished. Six teeth in each group were treated with either TiCl3 or ZrOCl9 8H20 for 2 minutes. The teeth were then washed for 2 minutes in deionized water. Enamel samples were removed by etching with hydrochloric acid. Hydrochloric acid was used because perchloric acid charred the cellulose powder with which the diluted, acid etch solution was mixed prior to analysis. ACIDIFIED GEL SYSTEM.-Preparation of the acidified gels and undecalcified ground sections has been described by Silverstone.5 In this study, a 20% (w/v) gelatin gel was used which was acidified with 1 M lactic acid to a pH of 4.3. Prior to the teeth being suspended in it was autoclaved, thus liquefying and sterilizing the gel. After initial preparation, 24 human teeth were sectioned longitudinally into halves and painted with varnish leaving 2 enamel windows exposed on the buccal and 1 on the lingual surface. The teeth were then divided into 6 groups of 4 teeth each. The treatment received by each of these groups is given in Table 1. The application times and washing regime were the same as those outlined earlier. After treatment these teeth were exposed to an acidified gel for 20 weeks. The teeth were then removed and longitudinal, undecalcified ground sections were prepared through the enamel windows. The sections were finally reduced to a thickness of 80 Am and viewed in polarized light.
TABLE 1 TREATMENT GIVEN TO SIX GROUPS OF TEETH Group
Treatment Received 4 Control Halves 4 Test Halves
TiC13 ZrOC12 T1C13 ZrOC12 TiC13 + APF
A B C D E F
ZrOC12 + APF
785
APF APF
Distilled H20 Distilled H20 APF APF
rately, in 25 cm3 of deionised distilled water which was agitated for 1 minute. This was repeated with fresh distilled water for a further minute. ANALYSES.-Enamel windows were etched for 60 seconds with 0.7 cm3 of 1 M perchloric or 6 N hydrochloric acid. The method of phosphorus determination used in this work was that described by Chen, Toribara, and Warner.'0 The calcium determination was carried out using a spectrophotometric technique-t The fluoride content of the acid etch solutions was determined using the Orion specific-ion fluoride electrode.11 The pretreatment samples were diffused for 24 hours according to the method of Singer and Armstrong,12 prior to fluoride concentrations being estimated with the electrode. Experiments were performed and confirmed that the polyvalent metal ions did not interfere with the measurement of fluoride ion concentration by the specific-ion electrode.13 Titanium and zirconium ions in enamel were detected using the technique of X-ray spectroscopy which had been used to detect
Results Table 2 shows that the fluoride uptake from APF was greater after enamel pretreat-
t "Rapid-Stat," Pierce Chemical Company, Rock-
ford, II.
BLE 2 FLUORIDE CONCENTRATIONS IN TITANIUM TRICHLORIDE- AND ZIRCONYL CHLORIDE-PRETREATED ENAMEL COMPARED WITH APF-TREATED ENAMEL Treatment
0.35 M TiC13 + APF APF 0.15 M ZrOCI, + APF APF +
P
-
Etch Depth ,Am mean +- S.D.
22.9 25.6 18.5 22.0
+ + + +
10.4 12.4 2.9 5.7
F Concentration ppm mean + S.D.
32348 4965 17410 2117
+ + + +
15808 1788 3272 1628
Comparison of differences in fluoride concentration between
nonpretreated halves of teeth using the paired difference t-test.
P+
< 0.005 n - 12 < 0.001 n= 12
pretreated
and
Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
786
CLARKSON
JDent Res July-August 1978
TABLE 3 CONCENTRATION OF TITANIUM AND ZIRCONIUM IN TrTANIUM TRICHLORIDEAND ZIRCONYL CHLORIDE-TREATED ENAMEL
Treatment
Etch*
Concentration ppm mean - S.D.
0.35 MTiC13
1 2 1 2
18327 ± 3172 6927 ± 2490 18400 ± 3355 5726 ± 2130
0.15 M ZrOC12
Etch Depth gm mean - S.D.
37.3 20.5 24.0 21.3
± 11.8 ± 7.5 ± 7.6 ± 6.9
* Two sequential etches of 60 seconds each.
ment with the metal salt solutions compared with the nonpretreated controls. These differences were found to be statistically significant for both the TiCl3 and ZrOCl28H20 pretreated teeth (P < 0.005 and P < 0.001, respectively). The metal ion concentrations are shown in Table 3. Approximately three times the concentration of both titanium and zirconium were found in the first enamel layer compared with the second. The two metal ions can be seen to have penetrated 45 to 55 jm into the enamel. Table 4 contains the results of experiments designed to establish the effects of the low pH of the pretreatment solutions on fluoride uptake. Higher fluoride concentrations were obtained in the halves pretreated with the polyvalent metal ions than in their acid pretreated controls. The difference in fluoride concentration between metal salt and acid pretreated halves of teeth was statistically significant (P < 0.005). In the in v tro caries part of the study, all lesions formed in groups A-D (see Table 1), whether in the test or control halves of teeth, were indistinguishable in terms of size and
depth of penetration. However, in groups E and F, distinct differences were seen between the lesions in the test and control halves of teeth. Ihe photomicrographs in Figure 1 are of 2 test and 2 control lesions from Group E and the photomicrographs in Figure 2 are of 2 test and 2 control lesions from Group F. The photomicrographs show a loss of surface enamel from the test windows because of the pretreatment with the metal salt solutions followed by APF, whereas no loss of enamel could be seen in the APF treated controls. The maximum enamel surface loss after TiCI3 (Fig 1) and ZrOClA8H20 (Fig 2) pretreatment was 20 ,im and 10 jAm, respectively. Despite this surface loss, no lesions were formed in the test halves (pretreated with the metal salt solutions followed by APF) but in their APFtreated controls classical caries-like lesions were produced (Figs 1 and 2). Similar results were observed in all test and control lesions in groups E and F. Discussion The greater uptake of fluoride by the enamel pretreated with the metal salt solu-
BLE 4 FLUORIDE CONCENTRATIONS OF TITANIUM TRICHLORIDE- AND ZIRCONYL CHLORIDE-PRETREATED ENAMEL COMPARED WITH ACID-PRETREATED ENAMEL Etch Depth gm mean + S.D.
Pretreatment
0.35 M
TiC3 4+
APF
HCI + APF 0.15 M ZrOC12 + APF HC1 + APF
26.2 31.3 22.3 25.4
± ± ± +
12.2 12.7 8.9 7.5
F Concentration ppm mean + S.D.
12430 + 3436 5240 4- 3480 8624 + 5685 5673 + 2097
P+
< 0.005 n = 12
< 0.005 n = 12
+ P - Comparison of differences in fluoride concentration between metal-pretreated and acid-pretreated halves of teeth using paired difference t-test.
Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
Vol.57 VIo ETAL/FLUORIDE COMPLEXES & CARIES No. 7-8
tioIns compared to the nonpretreated controls is ncot solely related to the low pH of these solutions (Table 4). It is probably due also to the high lev el Is `applroximiatexly I8,00(1 ppm) and deep penetration- of the ri-ietal salts (approximately 35 gon for Ti and 25 ym for Zr) into the enamel (Table 3). T-he imiiportance of t h e Luptake bx enlamel of tire nmetal ion xx as discussed by McCann.' He stated: "Howx ever, it is apparent that the iniitial fluoride Liptake is dependenit oni the amounit of aluminumn or other metals, initroduced into the enamiiel." Clarkson anid Silverstones have reported that multiple topical applications of sodium fltuoride, stannons fuitoricle and APF had no effect on the formIIatiotn or progression of tlhe (aries-like lesions)producCed in the acidified gMYels. In the present stuidy, it has been shomlsn thaat xvhen enamel lhas beenl pretreated xxith eitlher titanliuLm or zirconiuin and followed by onie application of APF, in vitro lesions do not form (Figs 1 and 2). Thus the pretreatimienit follossed by one APF application- produces an1 enamel which is more resistant to the condi-
787
tions founld in tlhe acidified gels, than that produced after multiple applicatioIns of topical fluoride oni nonpretreated cenanrel. This resistance miiay he conferred oII the enamel by the reaction- products formed after the pretreat-
ment/fluoride applications. In ani attempt to identifx these reaction products, X-ray diffraction analysis was carried
out on a samiiple of surface eniami-el after pretreatmnent xxith titanirrmi1 trichlor ide followed by APF application. It was concluded from the dliffractioni pattern that if crystalline mietal comiplexes xvere formicd they xxcrc in amounts too louv to he detected as separate phases. It may xxell he that soriie type of amorphous or
uricrrocrystalliuc substance is pr odtrced xxhicl xsworld not be detected bv x-rax diffractioni. Urlis findirno is siillar to thlat reported in ani earlier paper by McCann xvhere no change in the apatite of enamiiel pretreated xvith alumininiiii folloxed by APF could be detected by x-ray diffraction.' Further work to identify these reaction products is being undertaken. Attempts xere imade in more recent work
....:g........p:::S
w 1A;: 4W
:~~~ FIG
1.
Photomicrographs of adjacent,
un-
decalcitied sections of enamel from each half of the
same
sions.
tooth
Top,
left
showing and
in
right,
vitro
caries-like
treated
only
le-
APF; bottomn left and right, corresponding halves pretreated with titanium trichloride followed by APF.
with
Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
J DeiJnR t es Jut;y -A4 tixtj s 0 1 9 78
CLA,^RKSONV
788
-1
Dows Institute of Dental Research,
iow1a Citj, Iowao 52242. USA
College of )entistrv, The t TniVers1ty of Iozwa,
Pretreatment of enamiel with TiCl, and ZrOCL2-8H20 solutions prior to APF applicationi was shown to increase fluoride uptake and reduce caries-like lesion formation to a greater (-xtent than APF alonc. The increase in fluoridc ufptake by c?anel was not solely due to the low p1h of the Pretreatment solution.5. J Dent Res 57(7-8):784-789, July-August 1978.
Polvyalent metal ion salt solutions have been used as enamel pretreatment agents and have been found to enhance the fluoride uptake from acidulated phosphate fluoride (APF). It was suggested that this was because of their ability to form strong complexes with fluoride w-hile simultaneously binding with hydroxapatite. '2 Two further studies, in which rat molar teeth were pretreated with aluminum and titanium prior to fluoride application, showed increased fluoride uptake and decreased enamel solubility, but no effect on dental caries was noted.3'4 In this present study, a dual experimental approach was adopted which enabled additional information to be obtained concerning the caries preventive effect of metal/fluoride complexes. First, the fluoride concentration in enamel was determined after pretreatment with the titanium and zirconium salt solutions followed by an APF application. Second, the effect of these elevated fluoride levels on the formation of caries-like lesions in the acidified gel system5 was investigated. These caries-like lesions appear indistinguishable from natural enamel caries with respect to their detailed histopathology when viewed in polarized
light.6-8 Received for publication September 15, 1977. Accepted for publication January 18, 1978. *Analar grade, British Drug House Ltd., Dorset,
Materials and Methods PREPARATION OF TEETH.-All the human premolar teeth being used in the experiments were subjected to the same initial investigation, preparation, and storage.9 Teeth exhibiting cracks, hypoplastic areas, or caries on buccal surfaces were discarded. The remainder were sectioned longitudinally into halves through the buccal/lingual axis. The halves were painted with a colored acid-resistant varnish leaving two small windows of exposed enamel (6 mm2) on the buccal surface. The teeth were then divided into groups corresponding to the number of pretreatments to be given. Each group contained 6 teeth which gave a total of 12 control and 12 test enamel windows. FLUORIDE SOLUTION.-APF contained 1.23% F(w/v) as NaF and HF in 0.1 M orthophosphoric acid (pH 3.2). METAL SALT SOLUTIONS.-Solutions of titanium trichloride (TiC13) and zirconyl chloride (ZrOGl2.8H20)* were prepared at the following concentrations: 0.35 M (pH 1.1) and 0.15 AM (pH 1.2) respectively. TREATMENT OF TEETH.-One half of the tooth (test) received a 2-minute pretreatment followed by a 2-minute application of APF solution; the corresponding half (control) received a 2-minute application of APF. To establish the effect of the acidity of the metal salt solutions on fluoride uptake a series of experiments was devised in which halves of teeth were pretreated with acids of similar pH's to that of the metal salt solutions. Six teeth were prepared for each experiment. The control half of each tooth received a 2minute application of an acid and the test half received a -2-minute application of a metal salt solution. Both were followed by a 2-minute application of APF. WASHING PROCEDURE.-At the completion of the APF treatments, the experimental and control halves of teeth were each washed sepa-
784 Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
METAL/FL UORIDE COMPLEXES & CARIES
Vol. 57 No. 7-8
other metal ions in biological specimens.14,15 For use in these analyses, 12 teeth were selected after microscopic examination and the occlusal and root surfaces were varnished. Six teeth in each group were treated with either TiCl3 or ZrOCl9 8H20 for 2 minutes. The teeth were then washed for 2 minutes in deionized water. Enamel samples were removed by etching with hydrochloric acid. Hydrochloric acid was used because perchloric acid charred the cellulose powder with which the diluted, acid etch solution was mixed prior to analysis. ACIDIFIED GEL SYSTEM.-Preparation of the acidified gels and undecalcified ground sections has been described by Silverstone.5 In this study, a 20% (w/v) gelatin gel was used which was acidified with 1 M lactic acid to a pH of 4.3. Prior to the teeth being suspended in it was autoclaved, thus liquefying and sterilizing the gel. After initial preparation, 24 human teeth were sectioned longitudinally into halves and painted with varnish leaving 2 enamel windows exposed on the buccal and 1 on the lingual surface. The teeth were then divided into 6 groups of 4 teeth each. The treatment received by each of these groups is given in Table 1. The application times and washing regime were the same as those outlined earlier. After treatment these teeth were exposed to an acidified gel for 20 weeks. The teeth were then removed and longitudinal, undecalcified ground sections were prepared through the enamel windows. The sections were finally reduced to a thickness of 80 Am and viewed in polarized light.
TABLE 1 TREATMENT GIVEN TO SIX GROUPS OF TEETH Group
Treatment Received 4 Control Halves 4 Test Halves
TiC13 ZrOC12 T1C13 ZrOC12 TiC13 + APF
A B C D E F
ZrOC12 + APF
785
APF APF
Distilled H20 Distilled H20 APF APF
rately, in 25 cm3 of deionised distilled water which was agitated for 1 minute. This was repeated with fresh distilled water for a further minute. ANALYSES.-Enamel windows were etched for 60 seconds with 0.7 cm3 of 1 M perchloric or 6 N hydrochloric acid. The method of phosphorus determination used in this work was that described by Chen, Toribara, and Warner.'0 The calcium determination was carried out using a spectrophotometric technique-t The fluoride content of the acid etch solutions was determined using the Orion specific-ion fluoride electrode.11 The pretreatment samples were diffused for 24 hours according to the method of Singer and Armstrong,12 prior to fluoride concentrations being estimated with the electrode. Experiments were performed and confirmed that the polyvalent metal ions did not interfere with the measurement of fluoride ion concentration by the specific-ion electrode.13 Titanium and zirconium ions in enamel were detected using the technique of X-ray spectroscopy which had been used to detect
Results Table 2 shows that the fluoride uptake from APF was greater after enamel pretreat-
t "Rapid-Stat," Pierce Chemical Company, Rock-
ford, II.
BLE 2 FLUORIDE CONCENTRATIONS IN TITANIUM TRICHLORIDE- AND ZIRCONYL CHLORIDE-PRETREATED ENAMEL COMPARED WITH APF-TREATED ENAMEL Treatment
0.35 M TiC13 + APF APF 0.15 M ZrOCI, + APF APF +
P
-
Etch Depth ,Am mean +- S.D.
22.9 25.6 18.5 22.0
+ + + +
10.4 12.4 2.9 5.7
F Concentration ppm mean + S.D.
32348 4965 17410 2117
+ + + +
15808 1788 3272 1628
Comparison of differences in fluoride concentration between
nonpretreated halves of teeth using the paired difference t-test.
P+
< 0.005 n - 12 < 0.001 n= 12
pretreated
and
Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
786
CLARKSON
JDent Res July-August 1978
TABLE 3 CONCENTRATION OF TITANIUM AND ZIRCONIUM IN TrTANIUM TRICHLORIDEAND ZIRCONYL CHLORIDE-TREATED ENAMEL
Treatment
Etch*
Concentration ppm mean - S.D.
0.35 MTiC13
1 2 1 2
18327 ± 3172 6927 ± 2490 18400 ± 3355 5726 ± 2130
0.15 M ZrOC12
Etch Depth gm mean - S.D.
37.3 20.5 24.0 21.3
± 11.8 ± 7.5 ± 7.6 ± 6.9
* Two sequential etches of 60 seconds each.
ment with the metal salt solutions compared with the nonpretreated controls. These differences were found to be statistically significant for both the TiCl3 and ZrOCl28H20 pretreated teeth (P < 0.005 and P < 0.001, respectively). The metal ion concentrations are shown in Table 3. Approximately three times the concentration of both titanium and zirconium were found in the first enamel layer compared with the second. The two metal ions can be seen to have penetrated 45 to 55 jm into the enamel. Table 4 contains the results of experiments designed to establish the effects of the low pH of the pretreatment solutions on fluoride uptake. Higher fluoride concentrations were obtained in the halves pretreated with the polyvalent metal ions than in their acid pretreated controls. The difference in fluoride concentration between metal salt and acid pretreated halves of teeth was statistically significant (P < 0.005). In the in v tro caries part of the study, all lesions formed in groups A-D (see Table 1), whether in the test or control halves of teeth, were indistinguishable in terms of size and
depth of penetration. However, in groups E and F, distinct differences were seen between the lesions in the test and control halves of teeth. Ihe photomicrographs in Figure 1 are of 2 test and 2 control lesions from Group E and the photomicrographs in Figure 2 are of 2 test and 2 control lesions from Group F. The photomicrographs show a loss of surface enamel from the test windows because of the pretreatment with the metal salt solutions followed by APF, whereas no loss of enamel could be seen in the APF treated controls. The maximum enamel surface loss after TiCI3 (Fig 1) and ZrOClA8H20 (Fig 2) pretreatment was 20 ,im and 10 jAm, respectively. Despite this surface loss, no lesions were formed in the test halves (pretreated with the metal salt solutions followed by APF) but in their APFtreated controls classical caries-like lesions were produced (Figs 1 and 2). Similar results were observed in all test and control lesions in groups E and F. Discussion The greater uptake of fluoride by the enamel pretreated with the metal salt solu-
BLE 4 FLUORIDE CONCENTRATIONS OF TITANIUM TRICHLORIDE- AND ZIRCONYL CHLORIDE-PRETREATED ENAMEL COMPARED WITH ACID-PRETREATED ENAMEL Etch Depth gm mean + S.D.
Pretreatment
0.35 M
TiC3 4+
APF
HCI + APF 0.15 M ZrOC12 + APF HC1 + APF
26.2 31.3 22.3 25.4
± ± ± +
12.2 12.7 8.9 7.5
F Concentration ppm mean + S.D.
12430 + 3436 5240 4- 3480 8624 + 5685 5673 + 2097
P+
< 0.005 n = 12
< 0.005 n = 12
+ P - Comparison of differences in fluoride concentration between metal-pretreated and acid-pretreated halves of teeth using paired difference t-test.
Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
Vol.57 VIo ETAL/FLUORIDE COMPLEXES & CARIES No. 7-8
tioIns compared to the nonpretreated controls is ncot solely related to the low pH of these solutions (Table 4). It is probably due also to the high lev el Is `applroximiatexly I8,00(1 ppm) and deep penetration- of the ri-ietal salts (approximately 35 gon for Ti and 25 ym for Zr) into the enamel (Table 3). T-he imiiportance of t h e Luptake bx enlamel of tire nmetal ion xx as discussed by McCann.' He stated: "Howx ever, it is apparent that the iniitial fluoride Liptake is dependenit oni the amounit of aluminumn or other metals, initroduced into the enamiiel." Clarkson anid Silverstones have reported that multiple topical applications of sodium fltuoride, stannons fuitoricle and APF had no effect on the formIIatiotn or progression of tlhe (aries-like lesions)producCed in the acidified gMYels. In the present stuidy, it has been shomlsn thaat xvhen enamel lhas beenl pretreated xxith eitlher titanliuLm or zirconiuin and followed by onie application of APF, in vitro lesions do not form (Figs 1 and 2). Thus the pretreatimienit follossed by one APF application- produces an1 enamel which is more resistant to the condi-
787
tions founld in tlhe acidified gels, than that produced after multiple applicatioIns of topical fluoride oni nonpretreated cenanrel. This resistance miiay he conferred oII the enamel by the reaction- products formed after the pretreat-
ment/fluoride applications. In ani attempt to identifx these reaction products, X-ray diffraction analysis was carried
out on a samiiple of surface eniami-el after pretreatmnent xxith titanirrmi1 trichlor ide followed by APF application. It was concluded from the dliffractioni pattern that if crystalline mietal comiplexes xvere formicd they xxcrc in amounts too louv to he detected as separate phases. It may xxell he that soriie type of amorphous or
uricrrocrystalliuc substance is pr odtrced xxhicl xsworld not be detected bv x-rax diffractioni. Urlis findirno is siillar to thlat reported in ani earlier paper by McCann xvhere no change in the apatite of enamiiel pretreated xvith alumininiiii folloxed by APF could be detected by x-ray diffraction.' Further work to identify these reaction products is being undertaken. Attempts xere imade in more recent work
....:g........p:::S
w 1A;: 4W
:~~~ FIG
1.
Photomicrographs of adjacent,
un-
decalcitied sections of enamel from each half of the
same
sions.
tooth
Top,
left
showing and
in
right,
vitro
caries-like
treated
only
le-
APF; bottomn left and right, corresponding halves pretreated with titanium trichloride followed by APF.
with
Downloaded from jdr.sagepub.com at University of Sydney on May 4, 2015 For personal use only. No other uses without permission.
J DeiJnR t es Jut;y -A4 tixtj s 0 1 9 78
CLA,^RKSONV
788
-1
