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Journal of Indian Society of Pedodontics and Preventive Dentistry Official publication of Indian Society of Pedodontics and Preventive Dentistry
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Year : 2007  |  Volume : 25  |  Issue : 3  |  Page : 122-125

Study of changes in phosphate, calcium and fluoride ions in plaque and saliva after the administration of a fluoride mouth rinse

1 Faculty of Dentistry, Kerman University of Medical Sciences, Iran
2 Master of Science in Clinical Biochemistry, Kerman High Technology Centre, Iran
3 Health Centre, Kerman University of Medical Science, Iran

Correspondence Address:
H R Poureslami
Dental School, Shfa Ave, Kerman
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-4388.36561

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In this study, the effects of 0.2% sodium fluoride mouthwash solution on calcium, phosphate and fluoride ion contents of saliva and microbial plaque was assessed. Fourteen volunteer students (7-12 years of age) of a boarding educational centre in Kerman City (Iran) were selected and under defined conditions, their saliva and plaque samples were collected. The concentrations of fluoride, calcium and phosphate ions of the samples were determined, and after 14 days, under the same conditions, the students were asked to rinse their mouth with 0.2% sodium fluoride mouthwash solution. The second set of saliva and plaque samples were collected and the concentrations of the ions were determined. Data was analyzed using paired t-test and the results were presented as tables. P <0.05 was considered as statistically significant. After using 0.2% sodium fluoride mouthwash solution, a significant increase was observed in the F 2 ion concentration both plaque ( P < 0.000) and saliva ( P <0.000) of all the studied subjects, while the concentration of phosphate decreased in both saliva and plaque; however, this decrease was significant only in plaque ( P <0.01). The calcium ion concentration decreased in both plaque and saliva; however, in none of them, the decrease was significant ( P >0.09 and P >0.2, respectively).

Keywords: Calcium, fluoride, phosphate, plaque, saliva

How to cite this article:
Poureslami H R, Torkzadeh M, Sefadini M R. Study of changes in phosphate, calcium and fluoride ions in plaque and saliva after the administration of a fluoride mouth rinse. J Indian Soc Pedod Prev Dent 2007;25:122-5

How to cite this URL:
Poureslami H R, Torkzadeh M, Sefadini M R. Study of changes in phosphate, calcium and fluoride ions in plaque and saliva after the administration of a fluoride mouth rinse. J Indian Soc Pedod Prev Dent [serial online] 2007 [cited 2022 Aug 10];25:122-5. Available from: http://www.jisppd.com/text.asp?2007/25/3/122/36561

   Introduction Top

Mouthwash solutions and fluoride gels are beneficial in preventing dental caries. [1] In Iran, the distribution of 0.2% sodium fluoride mouthwash solution in primary schools has been started since a few years and students have been advised to use it once a week; however, the efficacy of this measure has not been studied clinically and paraclinically. The studies carried out in this regard are very few and a summary of their results is presented in [Table - 1]. [2],[3]

In this study, for the first time, the researchers aimed to assess the quality of the abovementioned mouthwash solution with regard to its effect on the concentrations of different ions.

The concentration of fluoride in the microbial plaque of tooth surface varies continuously. Fluoride may be taken up either directly from fluoridated water, fluoride containing foods, toothpaste and other topical sources or transported indirectly by saliva from similar sources. Fluoride ion in plaque and saliva controls the demineralization process, and its presence in the surface between plaque- enamel is the key for its efficacy since it improves the remineralization process by the deposition of phosphate and calcium ions. The formation of calcium fluoride on the surface of the enamel is the main product of all types of topical fluoride systems containing fluoride ions greater than 100 ppm. Calcium fluoride deposits act as an essential fluoride source and the gradual release of these globules covered with phosphate in the presence of organic acids provides a significant source of fluoride and phosphate, which promotes remineralization of the decalcified parts. [4]

The objective of the present study was to investigate the variations in calcium, phosphate and fluoride ion concentrations in the plaque and saliva following use of 0.2% sodium fluoride mouthwash solution in 7-12-year-old children.

   Materials and Methods Top

A group comprising 22 students of a boarding educational center in Kerman/Iran were selected for this study. Eight students were excluded due to active caries, cavity and\or space maintainers. The remaining 14 students were enrolled for the study after taking the informed consent from them and the center manager. The research was approved by the Ethics Committee of Kerman University of Medical Sciences. In the first stage of this study, the microbial plaque on children's teeth was removed using a slow-speed hand piece and a rubber cup without using any other substance. Subjects were asked to avoid brushing teeth, using tooth paste, floss or fluoride and other medical substances for 48 hours. After 48 hours, sampling of saliva and plaque was performed as follows.

Collecting and preparing saliva samples

Saliva sampling was done prior to plaque sampling. After giving a plastic container to each subject they were instructed to expectorate at least 1 ml of unstimulated saliva over 5 minutes into the container. Then, by using a sampler, saliva was transferred into a coded microtube. In order to homogenize the saliva samples, they were vertexed for a duration of 1 min by a vertex appliance. For the preparation of the samples, 100 ml of 1 M HClO 4 was mixed with 900 ml of saliva sample. After 2 hours, 100 ml of 90% total ionic strength adjusting buffer solution (TISAB 3; JENWAY, England) was added to the mixture and samples were centrifuged at 12000 rpm at the laboratory temperature for 3 minutes and prepared for laboratory investigation.

Collecting and preparing plaque samples

The children were asked to swallow their saliva to remove any pooled saliva in their mouth. Using sterile Kerr applicators, plaque samples were collected from the buccal surfaces of the two first permanent molars on the upper jaw and 1 mg of the sample was transferred into a microtube containing 1.5 ml of mineral oil. In order to increase the sensitivity of measurements, plaque samples were weighted with a digital scale with the sensitivity of 10 -4 g. All microtubes were centrifuged for 5 minutes. The plaque sample was placed in the lower part of tube and under the mineral oil so that the weight loss due to CO 2 was avoided. Subsequently, the collected samples were digested with 200 ml HClO 4 for later analyses and were diluted with 1800 ml TISAB for stability and recording ionic power. All saliva and plaque samples were filtered by a 0.2 m filter. The preparation of saliva and plaque samples were performed according to the technique described by Vogel et al. [8]

The amount of fluoride and phosphate ions of saliva and plaque samples was determined by Ion Chromatograph instrument (Metrohm Co. Swiss) using their specific columns. The instrument was calibrated with 10 standard samples. The amount of calcium ions was determined by Ion meter instrument (Metrohm Co, Swiss) and a calcium specific electrode.

After the first stage of research, subjects followed their usual diet and oral health habits for 14 days. Subsequently, identical to the first stage, microbial plaque from the surface of subjects' teeth was removed and they were asked to avoid brushing of teeth, use of toothpaste, floss, fluoride and medical substances for 48 h. Subsequently, the subjects were provided with 0.2% sodium fluoride mouthwash solution (Iran DAROO Co, BATCH No. 232), and they were asked to rinse with 5 ml of the solution for 1 minute. Saliva sampling was performed 1 minute after rinsing, and plaque sampling was performed after 60 minutes. The procedures were similar to the first stage. Subjects were instructed to abstain from eating, drinking and rinsing the mouth in the period between the rinsing with fluoride solution and the sample collection. Saliva and plaque samples were centrifuged and calcium, fluoride and phosphate ion contents were determined. Data was analyzed by SPSS (v.11.5) software package and using a paired t-test. P < 0.05 was considered as statistically significant.

   Results Top

The mean concentrations of calcium, fluoride and phosphate ions before and after using 0.2% sodium fluoride mouthwash are presented in [Table - 2],[Table - 3],[Table - 4].

After the administration of sodium fluoride mouthwash, fluoride concentration showed a significant increase in both the plaque and saliva ( P <0.0000), and the phosphate concentration decreased in saliva, but it increased in the plaque ( P <0.005) [Table - 3]. The calcium concentration in both the saliva and plaque decreased after using the mouthwash, but in none of them, the decrease was significant ( P >0.2 and P >0.09, respectively).

   Discussion Top

Fluoride has an important protective role for controlling the demineralization process of enamel. It has been previously thought that the effectiveness of topically applied sodium fluoride is due to formation of a fluorohydroxyapatite; however, later studies showed that the primary reaction product involved is the transformation of surface hydroxyapatite to calcium fluoride. The apatite crystal is disintegrated into its components and following that, the reaction between fluoride and calcium ions leads to the production of calcium fluoride with a net loss of phosphate ions. It has been proved that calcium fluoride deposit on enamel surface following the topical use of fluoride prevents dental caries. The initial deposition of calcium fluoride on the treated tooth surfaces is not permanent; a relatively fast decrease in the fluoride content occurs during the first 24 hours, and a gradual decrease occurs during the subsequent 15 days. In spite of this, the deposit leads to an increase in the fluoride content in the outermost layers of the enamel. [4],[5]

Researchers believe that fluoride enters into the plaque directly and indirectly. [4],[6] In the present study, the mean fluoride content of plaque prior to using 0.2% sodium fluoride mouthwash solution was 0.62 mg/l [Table - 2]. It appears that this fluoride accumulated in the plaque through water and food substances during the duration of 48 hours between the professional plaque removal using rubber cup and plaque sampling - both directly (topical use) and indirectly (systemic absorption, salivary glands and the fluid of gingival sulcus). The mean fluoride content of the saliva prior to the use of mouthwash was 0.319 mg/l [Table - 2]; which is relatively half the content in plaque. This can only be due to the systemic absorption of fluoride from water and food substances prior to the sampling.

After using the mouthwash solution, the fluoride content of plaque increased to approximately three times [Table - 3]. The findings show that 0.2% sodium fluoride mouthwash solution can increase fluoride ions in both plaque and saliva; however, due to the composition of plaque, ions can concentrate in the plaque more than that in saliva. Kato and coworkers (2002) reported that the calcium concentration of saliva has a direct effect on the accumulation of fluoride on plaque; however, they did not find any clear relationship between other salivary variables and fluoride accumulation in plaque. They attributed this fact to the role of calcium in the bacterial cell wall bonding of fluoride. [7] Moreover, it appears that in the present study, higher accumulation of fluoride in plaque than the saliva is related to the role of salivary calcium that binds fluoride ions to the bacterial cell walls and leads to greater accumulation of fluoride in plaque in comparison to saliva.

As shown in [Table - 2], the mean concentration of fluoride ion in plaque is three times as much as that in saliva. In the study by Vogel et al. (2002), the number of fluoride ions in 48-hour plaque, which was collected after 1 hour of using a mouthwash containing Na 2 SiF 6 was 7.5 times as much as that in saliva, which was collected after 1 min. [8] This difference may be due to the different mouthwashes used in the two studies with regard to their composition and amount of fluoride ions.

The results of the present study showed a decrease in the number of calcium and phosphate ions in plaque after using sodium fluoride mouthwash [Table - 3],[Table - 4]. According to Tanaka, following acid production, the amount of calcium and phosphate ions in the plaque increased. [9] They asked the subjects to rinse with sucrose solution instead of fluoride mouthwash so that the plaque pH decreased to a level lower than the critical pH and consequently the calcium and phosphate contents of plaque increased in order to neutralize the effect of the acid produced. In the present study, the fluoride ions were bound to the calcium and phosphate ions, thereby forming calcium fluoride globules covered with calcium phosphate. The amount of calcium decreased but plaque increased [Table - 3]. According to Harris and Garcia Godoy, the main mechanism of fluoride is related to its capability in facilitating the remineralization of demineralized sites. This ion enters the demineralized sites and reacts with calcium and phosphate during the remineralization process. [4]

Phosphate and bicarbonate are the most important components of the salivary buffering system; therefore, their amount in the whole saliva, particularly the saliva which is released from parotid glands is much more than calcium. The only exception in this regard is the minor salivary glands that release more calcium and less phosphate. It has been also said that unstimulated saliva has considerably greater amount of phosphate. [10] Moreover, in this study, the amount of phosphate in saliva was much more than calcium both before and after using mouthwash [Table - 3],[Table - 4].

It is assumed that calcium and phosphate crystals are present even in immature plaque, and at the time of acid attack, they amplify the buffering system significantly. With time, their amount in the plaque increases; in general, 10-day plaque contains approximately 25% of calcium mineral content. [11]

In the present study, the amount of phosphate in 48-hour plaque was more than calcium [Table - 3],[Table - 4]. Since in this study, sampling was done from the buccal surface of first molars in the upper jaw and the saliva from parotid glands contains higher amount of phosphate and lesser calcium as compared with the other salivary glands (4:1), [10] it seems that saliva content of parotid and also plaque have affected the amount of phosphate.

In conclusion, after administration of the 0.2% sodium fluoride mouthwash solution, fluoride ions accumulate in plaque and saliva.

   Acknowledgment Top

The financial support provided by the Vice Chancellor for Research, Kerman University of Medical Sciences is warmly acknowledged.

   References Top

1.McDonald AD, Avery DA, Dean JA. Text book of dentistry for the child and adolescent. 8 th ed. 2004 p. 227-9  Back to cited text no. 1    
2.Mahmoodian J, Kosari A, Esmaili B. A comparison of Fluoride Uptake by Sound enamel following application of sodium fluoride mouthrinses and APF gels produced in Iran with standardized foreign samples. J Dent Tehran Univ Med Sci 2002;14:43-9  Back to cited text no. 2    
3.Ansari G, Sadr AR. Evaluation of fluoride uptake by enamel from Iran school's rinse in comparison with Naf rinse. Beheshti Univ Dent J 2004;21:642-51  Back to cited text no. 3    
4.Harris No, Garcia Godoy F. Primary preventive dentistry. 6 th ed. 2004. p. 241-84  Back to cited text no. 4    
5.ten Cate JM. Review on fluoride, with special emphasis on calcium fluoride mechanisms in caries prevention. Eur J Oral Sci 1997;105:461-5  Back to cited text no. 5    
6.Bowen WH, Geddes DA. Fluoride in saliva and dental plaque. J Dent Res 1990;69:637-8  Back to cited text no. 6    
7.Kato K, Nakagaki H, Arai K, Pearce EI. The influence of salivary variables on fluoride retention in dental plaque exposed to mineral-enriching solution. Caries Res 2002;36:58-63  Back to cited text no. 7    
8.Vogel GL, Zheng Z, Chow LC, Schumacher GE. Changes in lactate and other ions in plaque and saliva after a fluorid rinse and subsequent sucrose administration. Caries Res 2002;36:44-52  Back to cited text no. 8    
9.Tanaka M, Margolis HC. Release of mineral ions in dental plaque following acid production. Arch Oral Biol 1999;44:253-8  Back to cited text no. 9    
10.Edgar M, Dawes C, Mullane D. Saliva and oral health. 3 rd ed. BDJ Books: 2004. p. 32-94  Back to cited text no. 10    
11.Ashley FP. Calcium and phosphorus concentrations of dental plaque related to dental caries in 11-14 year old subjects. Caries Res 1975;9:351-62  Back to cited text no. 11    


  [Table - 1], [Table - 2], [Table - 3], [Table - 4]

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