n
Effect of Calcium Pre-rinse and Fluoride on Enamel and on Dental Plaque Formed In Situ
ot
Q ui
by N ht
pyrig No Co t fo rP ORIGINAL ARTICLE ub lica tio n te ss e n c e Dentifrice
fo r
Tatiana Almeida Furlania/Ana Carolina Magalhãesa/Flávia Godoy Ianoa/ Vanessa Eid da Silva Cardosoc/Alberto Carlos Botazzo Delbemb/ Marília Afonso Rabelo Buzalafa
Purpose: The aim of this in situ double-blind randomised crossover study was to investigate the effect of calcium (Ca) pre-rinse on the composition of plaque and on enamel prior to the use of fluoride (F) dentifrice. Materials and Methods: During four phases (14 days each) of this study, 10 volunteers had agreed to wear dental appliances containing two healthy bovine enamel blocks. A fresh solution containing 20% weight/volume (w/v) sucrose was dripped on the enamel blocks ex vivo for 5 min three times a day. Subsequently, the appliances were replaced in the mouth, and the volunteers rinsed their mouth with 10 mL of a Ca (150 mmol/L) or a placebo rinse (1 min). In sequence, a slurry (1:3 w/v) of F (1030 ppm) or placebo dentifrice was dripped onto the blocks ex vivo for 1 min. During this time, the volunteers brushed their teeth with the respective dentifrice. The appliances were replaced in the mouth, and the volunteers rinsed their mouth with water. The plaque formed on the blocks was analysed for F and Ca. The enamel demineralisation as well as the incorporation of F on enamel was evaluated by cross-sectional microhardness and alkalisoluble F analysis, respectively. Data were tested using analysis of variance (P < 0.05). Results: The Ca pre-rinse prior to the use of the F dentifrice led to a three- and sixfold increase in the plaque F and Ca concentrations, respectively. It also did not have any additive effect on the F content on the enamel and the demineralisation of the enamel, in comparison with the use of F dentifrice alone. Conclusions: A Ca lactate rinse used prior to the F dentifrice was able to change the mineral content in the plaque, but it was unable to prevent enamel demineralisation. Key words: calcium, dental enamel, dental plaque, fluoride dentifrice, in situ Oral Health Prev Dent 2009; 7: 23–28.
he cariostatic effect of fluoride (F) dentifrices has been recognised for a long time, and, in conjunction with improved daily oral hygiene, F dentifrice is regarded as the major factor responsible for the
T a
Bauru School of Dentistry, University of São Paulo (USP), Bauru, SP, Brazil.
b
School of Dentistry of Araçatuba, São Paulo State University (UNESP), Araçatuba, SP, Brazil.
c
Institute of Chemistry, University of São Paulo (USP), São Paulo, SP, Brazil.
Correspondence: Marília Afonso Rabelo Buzalaf, Department of Biological Sciences, Bauru School of Dentistry, University of São Paulo, Al. Octávio Pinheiro Brisolla, 9-75 Bauru, SP 17012-901, Brazil. Tel: +55 14 32358246. Fax: +55 14 32343164. Email:
[email protected]
Vol 7, No 1, 2009
Submitted for publication: 23.12.07; accepted for publication: 05.02.08.
dramatic caries reduction in children and young adults in most industrialised countries during the past few decades (Blayney and Hill, 1967; Murray et al, 1991; Axelsson, 2004). Fluoride may be deposited on the enamel by the formation of a CaF2-like reservoir. During a cariogenic challenge, F released from this reservoir may diffuse into the enamel promoting reformation of apatite (ten Cate, 1997, 1999). Demineralised enamel contains larger amounts of F than sound enamel (Kielbassa et al, 2005) and the dental plaque is an important reservoir of this compound. Clinical studies have demonstrated an inverse relationship between the F concentrations in the dental plaque and the prevalence of dental caries (Arnold et al, 1962; Ast and Fitzgerald, 1962; Arends and Christoffersen, 1990). 23
• Ca solution rinse (Sigma–Aldrich, Atlanta, GA, USA) and F dentifrice (1030 ppm F, Crest, P&G, Cincinnati, OH, USA) (Ca–F) 24
fo r
This study was approved by the Research and Ethics Committee of the Bauru School of Dentistry, University of São Paulo. After signing an informed consent, ten volunteers (Cai et al, 2003; Martinhon et al, 2006) with good oral and general health (5 males and 5 females, mean age 24 years, mean DMFT 7.4, patient hygiene performance [PHP] index 0 to 1) took part in a double-blind and randomised crossover study conducted in four phases of 14 days each, with a 7-day washout period between them. During the 14 days, the cariogenic challenge was applied three times a day. After this, the following treatments were used:
ot
Experimental design (Fig 1)
•
n
MATERIALS AND METHODS
•
Q ui
It now appears certain that the uptake and the retention of F by dental plaque is mainly dependent on plaque calcium (Ca) concentrations (Whitford et al, 2002, 2005; Pessan et al, 2006; Magalhães et al, 2007). Following this rationale, attempts to increase the cariostatic effectiveness of F have focused on methods to increase Ca concentrations in dental plaque. It was reported that a 150 mmol/L Ca lactate prerinse significantly increased the salivary F concentrations after the use of a 228 ppm F rinse (Vogel et al, 2006a). Significant increases in F concentrations in biofilm fluid (Vogel et al, 2005) and in the entire biofilm (Vogel et al, 2006b) were also reported when the Ca lactate pre-rinse was used. In the studies mentioned above, the vehicle for the use of F was a mouth rinse. However, F dentifrices are by far the most frequently used topical F vehicle (Ammari et al, 2003). Despite a significant increase in salivary F levels after the use of F dentifrice preceded by a Ca pre-rinse (Vogel et al, 2006c), other authors have not observed these results (Whitford et al, 2005), or have identified an increase in 1-h post-treatment samples, but have not identified an increase in 12-h samples (Pessan et al, 2006). This study was designed as an attempt to reconcile these different findings. For this purpose, an in situ model using bovine enamel and including a cariogenic challenge was used, so that, besides the evaluation of plaque F and Ca concentrations, the associated enamel alterations could also be assessed.
by N ht
Furlani et al
pyrig No Co t fo rP ub lica tio Ca solution rinse and placebo dentifrice (identin t cal to Crest but with no detectable F)e s(Ca) se nc e placebo solution rinse (deionised water) and F
dentifrice (F) • placebo solution rinse and placebo dentifrice (P). The abrasive system in the dentifrices is the hydrated silica, and the dentifrices contain no detectable Ca.
Enamel blocks and palatal appliance preparation One hundred and twenty incisor bovine teeth, freshly extracted, sterilised by storage in 2% formaldehyde solution (pH 7.0) for 30 days at room temperature were cut. For this purpose, an ISOMET Low Speed Saw Cutting Machine (Buehler, Lake Bluff, IL, USA) and two diamond discs (Extec, Enfield, CT, USA), which were separated by a 4-mm diameter spacer were used. The 4 · 4 · 2.5 mm enamel blocks were ground flat with water-cooled carborundum discs (320, 600 and 1200 grades of Al2O3 papers; Buehler, Lake Bluff, IL, USA) and polished with felt paper wet by diamond spray (1 lm; Buehler), resulting in the removal of the enamel at a depth of about 100 lm. This was controlled with a micrometer. The surface microhardness determination was performed using five indentations (Knoop Diamond, 25 g, 10 s, HMV2000; Shimadzu, Tokyo, Japan). Eighty blocks with mean 330 to 380 Knoop harness number (KHN) were selected and randomly allocated for the intra-oral phases. One cavity of 5 · 5 · 3 mm was made on both the left and right sides of the acrylic resin palatal appliances, and in each of them one block of enamel was fixed with wax. For this purpose, a 4 mm deep space was created in the acrylic resin appliance, leaving a 1.5 mm space for plaque accumulation (Driessens et al, 1986). For the formation of dental plaque on the enamel block, the cavity was protected from mechanical disturbance by a plastic mesh fixed in the acrylic resin surface. The blocks were replaced after each washout phase.
Treatment procedure Three times a day, after meals, the volunteers dripped a fresh solution containing 20% w/v sucrose on the enamel blocks (3 drops/block) ex vivo. After 5 min, the appliances were replaced into the mouth and the volunteers rinsed their mouth with 10 mL of a 150 mmol/L Ca lactate or placebo solution, for Oral Health & Preventive Dentistry
n
ot
Q ui
by N ht
pyrig No Co t fo r P et al Furlani ub lica tio n te ss e n c e
fo r
Fig 1 Experimental design. (A) Sample preparation; (B) in situ phases (4 phases · 2 samples · 14 days) with participation of 10 volunteers; (C) application of 20% sucrose solution (three times a day, 5 min) on enamel surface; (D) rinsing with a Ca solution or water (10 mL, 1 min); (E) dripping of F or placebo dentifrice slurry (1 min); (F) plaque F analysis by electrode; (G) plaque Ca analysis by AAS; (H) CSMH assessment and (I) enamel alkali-soluble F analysis.
1 min. In sequence, the solution was expectorated and a slurry (1:3 w/v) of F or placebo dentifrice was dripped onto the enamel blocks (3 drops/block) ex vivo. For 1 min, the volunteers brushed their teeth with a pea-size amount (~0.3 g) of the respective dentifrice. The volunteers then replaced the appliance in the mouth and rinsed their mouth with 5 mL of drinking water (0.7 ppm F) for 10 s. All solutions and dentifrices used were placed in separate vials, which did not allow identification by the volunteers, so as to conform to the blind protocol of the study. In addition, all the solutions were prepared by the researcher 1 day before the experiment, and the volunteers were instructed to redisperse the mixture before use. A 7 day washout period was required before the beginning of the study and between the treatment phases to minimise the possible residual effects from the previous treatment. During the experimental period, the volunteers received instructions to wear the appliance at all times, including at night, but to remove it during mealtimes (1 h · 3 meals/ day), when it was placed in gauze, which was wet with deionised water. The volunteers received oral and written information instructing them to refrain Vol 7, No 1, 2009
from using any antibacterial or fluoridated product except the test dentifrice.
Analysis of dental plaque After each phase, the plastic meshes were removed, and the dental plaque formed on all the enamel blocks was collected with plastic curettes, 12 h after the last exposure to the solutions. The material was placed in pre-weighed microcentrifuge tubes. The wet weight of each sample was determined within approximately 10 mg. For inorganic composition analysis, 0.5 mmol/L HCl was added to each tube in the proportion of 0.5 mL/10.0 mg wet weight. After extraction for 3 h at room temperature under constant agitation, the same volume of total ionic strength adjustment buffer (TISAB) pH 5.0, was added to each tube as a buffer (Driessens et al, 1986; Dibdin and Shellis, 1988). The samples were centrifuged (11,000g) for 1 min and the supernatant was retained for the determination of F and Ca. In the acid extract of each plaque sample, F was determined with an ion-selective electrode Orion 96-09 and an ion analyser EA-940, using the method 25
The concentration of F was evaluated in the other half of the blocks that was not used for CSMH analysis (Caslavska et al, 1975). A circular hole (2.0 mm diameter) was punched in adhesive tape, which was applied firmly to the centre of the enamel block surface. The remaining surfaces of the block were painted with wax so that only a 3.14 mm2 surface area was exposed. The block was then placed in a plastic test tube containing 0.30 mL of 1 mol/L KOH for 24 h under constant agitation. An equal volume of TISAB II containing concentrated HCl (100 mmol/L TISAB II with 8.5 mmol/L HCl) was added. This solution was analysed with the electrode, along with standards containing 0.025 to 3.2 lg F/mL. Data were expressed as lg F/mm2.
Statistical analysis The data passed normality and homogeneity tests (except the data regarding dental plaque, which were subjected to logarithmic transformation) and were then analysed by repeated measures two-way analysis of variance (ANOVA) and Bonferroni test (for CSMH), and repeated measures ANOVA and Tukey– Kramer test were carried out (for the other variables), using the softwares GraphPad Prism 4 and GraphPad Instat (GraphPad Software, San Diego, USA), respectively. A significance level of 0.05 was selected a priori. 26
fo r
Determination of alkali-soluble F on enamel
Treatment** P Ca F Ca–F
Ca (lg/mg) 1.68 1.51 3.17 9.19
± ± ± ±
0.34a 0.32a 0.42a 0.99b
ot
To perform cross-sectional microhardness (CSMH) tests, the blocks of each volunteer in each treatment were longitudinally sectioned through the centre, embedded and polished. Three rows of eight indentations in each block were made, one in the central region of the dental enamel exposed and the other two 100 lm below and above this, under a 25 g load for 10 s. The indentations were made at 10, 30, 50, 70, 90, 110, 220 and 330 lm from the outer enamel surface. The mean values at all three measuring points at each distance from the surface were then averaged and were converted to percentage of mineral volume (Featherstone et al, 1983).
n
Microhardness analysis
Q ui
created by Hallsworth et al (1976). Ca was determined by atomic absorption spectrometry (AAS Vario 6, Analytik Jena, Germany), using lanthanum to suppress the phosphate interference.
by N ht
Furlani et al
pyrig No Co t fo rP ub lica t Table 1 Mean (±SE) Ca and F concentrations present ion t in the biofilm, according to the treatment e ss e nc e TF (ng/mg)* 14.29 16.86 187.24 578.70
± ± ± ±
1.51a 3.44a 44.54b 82.14c
Values in the same column followed by different superscript lower case letters indicate statistically significant differences (P < 0.05). * Statistical analysis conducted after log transformation; **P, placebo rinse and placebo dentifrice; Ca, Ca rinse and placebo dentifrice; F, placebo rinse and F dentifrice; Ca–F, Ca rinse and F dentifrice.
Table 2 Mean % mineral volume (±SD) and enamel alkali-soluble F concentrations (±SE) Treatment* P Ca F Ca–F
% min volume (10 lm) 52.27 71.74 72.45 72.99
± ± ± ±
13.00a 10.00b 14.50b 13.00b
F (lg/mm2) 1.42 0.78 10.65 14.52
± ± ± ±
0.39a 0.24a 2.90b 3.60b
Values in the same column followed by different superscript lower case letters indicate statistically significant differences (P < 0.05). * P, placebo rinse and placebo dentifrice; Ca, Ca rinse and placebo dentifrice; F, placebo rinse and F dentifrice; Ca–F, Ca rinse and F dentifrice.
RESULTS Table 1 presents the mean F and Ca concentrations in the plaque samples, according to the treatments. The mean F concentration was higher for the groups where F dentifrice was used (F and Ca–F). There was a 3-fold increase in F concentration, when the Ca prerinse was used along with the F dentifrice (Ca–F compared with F groups, P < 0.05). A similar result was found for the Ca concentrations. When the Ca prerinse was used along with F dentifrice (Ca–F group), a sixfold increase in plaque Ca concentration was seen when compared with the Ca rinse alone (Ca–F compared with Ca groups, P < 0.05). Table 2 presents the mean CSMH (% mineral volume) as well as alkali-soluble F concentrations according to the treatment. With respect to CSMH, at the distance of 10 lm from the surface, there was a significant reduction in the loss of mineral volume for all the treatments when compared with placebo (P < 0.05). For the other distances, no Oral Health & Preventive Dentistry
ot
fo r
Vol 7, No 1, 2009
by N ht
Toothbrushing with a F dentifrice is an important public health measure for the control of dental caries, because it combines the removal or disruption of dental plaque with the cariostatic effect of F. While it is not possible to completely remove the dental plaque by tooth brushing, the amount of F incorporated can play an important role in caries control. There is considerable evidence showing that the uptake and retention of F is directly related to the amount of Ca in plaque (Whitford et al, 2002; Vogel et al, 2005, 2006b; Pessan et al, 2006; Magalhães et al, 2007). In this study, the Ca lactate rinse prior to the use of F caused a threefold increase in plaque F concentrations, which is lower than the findings reported in a study in which the effect of a 150 mmol/L Ca lactate pre-rinse on F uptake from a 228 ppm F rinse by whole plaque was tested (Vogel et al, 2006b). This difference may be attributed to the different F vehicles used (F dentifrice · F rinse), as the surfactant sodium lauryl sulfate present in the dentifrice has been reported to have a strong affinity for Ca (Barkvoll et al, 1988; Rykke et al, 1990), which could affect the availability of ionic Ca and hence the uptake of F by plaque during the use of the dentifrice. Furthermore, the results of the study mentioned above (Vogel et al, 2006b) refer to the plaque collected 1 h after exposure to F, although in this study the plaque was collected 12 h after exposure to the treatments. On the other hand, the increase seen in plaque F concentrations when the Ca pre-rinse was used is in contrast with the results reported previously by Pessan et al (2006). However, it must be pointed out that in the study by Pessan et al (2006), the plaque was allowed to accumulate only for 12 h before collection, because the teeth surfaces were regularly brushed. In this study, the plaque remained undisturbed and protected by the plastic mesh during the whole experimental period (14 days), which allowed a cumulative effect to occur. This reason, in addition to the reduction in the bioavailability of F present in the dentifrice (due to the existence of sodium lauryl sulfate) may have led to a smaller F uptake in the study by Pessan et al (2006).
n
DISCUSSION
Q ui
significant differences among the groups and the control were seen. The area under the KHN versus lm curve was similar for all groups (data not shown). There was a significant increase in enamel alkali-soluble F, when the F dentifrice was used, but the Ca pre-rinse did not have any significant additive effect.
pyrig No Co t fo r P et al Furlani ub lic A similar result was found for Ca concentrations,atio te et al n in accordance with the study by Magalhães ss e n c e (2007). When the Ca pre-rinse was used along with F dentifrice, a sixfold increase in plaque Ca concentration was seen, when compared with the Ca rinse alone. This was expected, due to the close association between plaque F and Ca concentrations that have been extensively reported (Whitford et al, 2002, 2005; Pessan et al, 2006; Vogel et al, 2006b). The Ca probably reacted with F, forming CaF2 in the plaque. One interesting finding is that the use of the Ca rinse alone did not significantly increase the plaque Ca concentration. One probable reason for this is that the cariogenic challenge (20% sucrose, three times a day) may have released ‘free’ Ca from the plaque reservoirs, and this Ca may have been taken up by the enamel. The alkali-soluble F concentration in enamel, similar to what was reported for the plaque, significantly increased when the F dentifrice was used, but the Ca pre-rinse did not improve significantly the performance of the F dentifrice, which is in agreement with the results of the study performed by Magalhães et al (2007). The in situ design used in this study may have contributed to this result, as a space was created between the enamel block surface and the plastic mesh to allow plaque accumulation. Thus, it is possible that the layer of plaque deposited on the enamel block may have impaired the deposition of CaF2 globules on the enamel surface, which meant the CaF2 remained in the dental plaque. In addition, it is well known that F present in phosphate- and protein-covered CaF2 deposits (formed after a topical F application) is released with decreasing pH when the phosphate groups become protonated (ten Cate, 1997). The relatively small cariogenic challenge used in this study may not have been enough to dissolve the CaF2 deposits present in the plaque, thus releasing the respective ions to be incorporated into the enamel, which is confirmed by the high Ca and F concentrations found in the plaque of the Ca–F group. Further clinical trials should evaluate if higher degrees of F uptake in enamel are obtained when the plaque is constantly removed by toothbrushing and/or mastication and when higher cariogenic challenges are performed. Blake-Haskins et al (1992) showed in vitro that the treatment of enamel with Ca (CaCl2, 180 ppm, 10 min) prior to F (NaF, 100 ppm, 10 min) reduced the caries lesion formation (microradiography) to 90% for F solution and to 46% for F dentifrice in comparison with F treatment alone (68% for F solution and 32% for F dentifrice, respectively). One possible reason for the failure of the Ca pre-rinse to reduce enamel 27
1. Ammari AB, Bloch-Zupan A, Ashley PF. Systematic review of studies comparing the anti-caries efficacy of children’s toothpaste containing 600 ppm of fluoride or less with high fluoride toothpastes of 1000 ppm or above. Caries Res 2003;37:85–92. 2. Arends J, Christoffersen J. Nature and role of loosely bound fluoride in dental caries. J Dent Res 1990;69:601–605. 3. Arnold FA, Likins RC, Russel AL, Scott DB. Fifteenth year of the Grand Rapids fluoridation study. J Am Dent Assoc 1962;65:780–785. 4. Ast DB, Fitzgerald B. Effectiveness of water fluoridation. J Am Dent Assoc 1962;65:581–585. 5. Axelsson P. Use of fluorides. In: Axelsson P (ed). Preventive Materials, Methods and Programs. Vol IV. Carol Stream: Quintessence Books, 2004;263–368. 6. Barkvoll P, Rølla G, Lagerlöf F. Effect of sodium laurel sulfate on the deposition of alkali-soluble fluoride on enamel in vitro. Caries Res 1988;22:139–144. 7. Blake-Haskins JC, Mellberg JR, Snyder C. Effect of calcium in model plaque on the anticaries activity of fluoride in vitro. J Dent Res 1992;71:1482–1486. 8. Blayney JR, Hill IN. Fluorine and dental caries. J Am Dent Assoc 1967;74:225–302. 9. Cai F, Shen P, Morgan MV, Reynolds EC. Remineralization of enamel subsurface lesions in situ by sugar-free lozenges containing casein phosphopeptide–amorphous calcium phosphate. Aust Dent J 2003;48:240–243. 10. Caslavska V, Moreno EC, Brudevold F. Determination of the calcium fluoride formed from in vitro exposure of human enamel to fluoride solutions. Arch Oral Biol 1975;20: 333–339.
28
fo r
REFERENCES
ot
The authors thank FAPESP for the concession of a grant to the M.A.R.B. (Proc. No. 01/13588-9) and also a scholarship to the T.A.F. (Proc. No. 04/11653-6), which permitted the completion of the study. This publication was based on a thesis submitted by the T.A.F. to Bauru School of Dentistry, University of São Paulo, in partial fulfilment of the requirements for an MS Degree in Oral Biology. Figure 1 was prepared by Heitor Marques Honório and modified by Ana Carolina Magalhães.
n
ACKNOWLEDGEMENTS
Q ui
demineralisation, despite increasing Ca and F plaque concentrations, is the low cariogenic challenge. The subsurface demineralisation was limited to the outer 10 lm. Under more severe cariogenic conditions (20% sucrose, 8 times/day) or under extended cariogenic challenges (21 to 28 days), it is possible that the degree of demineralisation of the control group would be higher, thus allowing the detection of significant differences among the groups. In conclusion, this study showed that a Ca lactate pre-rinse, when compared with F dentifrice alone, despite increasing the plaque Ca and F concentrations, did not have any additive effect on the enamel subjected to a low cariogenic challenge.
by N ht
Furlani et al
pyrig No Co t fo rP ub lic 11. Dibdin GH, Shellis RP. Physical and biochemical studies a ofti o Streptococcus mutans sediments suggest tnew factor link- n e ing with cariogenicity of plaque with its sextracellular se nc e polysaccharide content. J Dent Res 1988;67:890–895. 12. Driessens FC, Theuns HM, Heijligers HJ, Borggreven JM. Microradiography and electron microprobe analysis of some natural white and brown spot enamel lesions with and without laminations. Caries Res 1986;20:398–405. 13. Featherstone JD, ten Cate JM, Shariati M, Arends J. Comparison of artificial caries-like lesions by quantitative microradiography and microhardness profiles. Caries Res 1983;17:385–391. 14. Hallsworth AS, Weatherell JA, Deutsch D. Determination of subnanogram amounts of fluoride with the fluoride electrode. Anal Chem 1976;L8:1160–1164. 15. Kielbassa AM, Gillmann L, Zantner C, Meyer-Lueckel H, Hellwig E, Schulte Mönting J. Profilometric and microradiographic studies on the effects of toothpaste and acid gel abrasivity on sound and demineralized bovine dental enamel. Caries Res 2005;39:380–386. 16. Magalhães AC, Furlani TA, Italiani FM, Iano FG, Delbem ACB, Buzalaf MAR. Effect of calcium pre-rinse and fluoride dentifrice on remineralization of artificially demineralized enamel and on the composition of the dental biofilm formed in situ. Arch Oral Biol 2007;52:1155–1160. 17. Martinhon CC, Italiani F de M, Padilha P de M, Bijella MF, Delbem AC, Buzalaf MA. Effect of iron on bovine enamel and on the composition of the dental biofilm formed ‘in situ’. Arch Oral Biol 2006;51:471–475. 18. Murray JJ, Rugg-Gunn AJ, Jenkins GN. Fluoride in Caries Prevention. Oxford: Butterworth–Heinemann, 1991;86–87. 19. Pessan JP, Sicca CM, Souza TS, Silva SMB, Whitford GM, Buzalaf MAR. Fluoride concentrations in dental plaque and saliva after the use of a fluoride dentifrice preceded by a calcium lactate rinse. Eur J Oral Sci 2006;114:489–493. 20. Rykke M, Rølla G, Sonju T. Effect of sodium lauryl sulfate on protein adsorption to hydroxyapatite in vitro and on pellicle formation in vivo. Scand J Dent Res 1990;98: 135–143. 21. ten Cate JM. Current concepts on the theories of the mechanism of action of fluoride. Acta Odontol Scand 1999;57:325–329. 22. ten Cate JM. Review on fluoride, with special emphasis on calcium fluoride mechanisms in caries prevention. Eur J Oral Sci 1997;105:461–465. 23. Vogel GL, Shin D, Schumacher GE, Takagi S. Plaque fluid and salivary fluid one hour after a Ca pre-rinse/NaF rinse. Caries Res 2005;39:316 (Abstract 85). 24. Vogel GL, Chow LC, Carey CM, Schumacher GE, Takagi S. Effect of calcium pre rinse on salivary fluoride after a 228-ppm fluoride rinse. Caries Res 2006a;40:178–180. 25. Vogel GL, Shin D, Takagi S, Schumacher GE, Chow LC. Calcium pre-rinse increases extractable fluoride in plaque from NaF rinse. 35th Annual Meeting and Exhibition of the AADR, Orlando, FL, 8–11 Mar 2006b. 26. Vogel GL, Shin D, Schumacher GE, Carey CM, Chow LC, Takagi S. Salivary fluoride from fluoride dentifrices or rinses after use of a calcium pre-rinse or calcium dentifrice. Caries Res 2006c;40:449–454. 27. Whitford GM, Buzalaf MA, Bijella MF, Walter JL. Plaque fluoride in a community without water fluoridation: effects of calcium and use of a fluoride or placebo dentifrice. Caries Res 2005;39:100–107. 28. Whitford GM, Wasdin JL, Schafer TE, Adair SM. Plaque fluoride concentrations are dependent on plaque calcium concentrations. Caries Res 2002;36:256–265.
Oral Health & Preventive Dentistry
