1. Poster #623
2294
Ion Measurements Following Chewing of Fluoride Containing Bioactive Glass Gums
Linda HASSANALI*1, DAVID GILLAM2 and ROBERT HILL1
1Dental Physical Sciences, and 2Adult Oral Health, Barts and the London School of Medicine and Dentistry, Queen Mary University London, United Kingdom.
Introduction
A novel bioactive glass gum containing the glass system SiO2 – P2O5 – CaO – Na2O was used with increasing amounts of fluoride added. A high phosphate proportion (6mol %) was used due to evidence of promoting apatite formation. Gums containing 0F, 0.25F, 0.5F, 1F and 5F wt% were made by blending two glasses together (0 mol% and 4.5 mol% CaF2). Manual mastication in 5ml tris buffer solution over 5, 10 and 20mins was then followed by analysis with ISE and ICP for F, Ca and P ion release. FTIR was used to identify Fluorapatite (FAP) formation on the inside surface of the chewing device. Data showed release of F, Ca and P from all bioactive glass gums into solution with release correlating to chewing time and fluoride content. The ratios of ions released over time and with increasing F content shifts towards the ideal ratio of 5:3:1 for FAP precipitation.
Objectives:
To identify if the bioactive glass gum releases ions into solution using ISE and ICP.
To identify the relationship between fluoride content and ion concentration in tris buffer
To confirm fluorapatite is formed and deposited within the specified time limit of 20mins using FTIR
Method
Gums with 5 wt% glasses composed of a range of fluoride concentrations (0-5F wt%) were used with each gum piece (approx. 1g) containing 0.05g of glass.
Conclusion
A release of 2.65% of the total fluoride content into solution was achieved. This may be due to precipitation of fluoride within the gum base. However, at 7ppm F, a therapeutic effect is still achievable in particular for those with dentine hypersensitivity. Ca and P in saliva may also promote FAP precipitation.
Decreases in Ca and P over time and with increasing F content suggests they are being precipitated. FTIR peaks forming in the apatite regions in the 5F 20min sample. Increased chewing time may be needed to see more definite peaks.
FTIR for apatite presence
Table 1. Glass composition in mol % of the two high phosphate glasses mixed together ito give 0F, 0.25F, 0.5F, 1F and 5F concentrations in the glasses used. (Mneimne et al 2011)
Results
Fig 1a. The apparatus set up for manually chewing the bioactive glass gums. Figures 1b-c. chemical analysis of F, Ca and P ion concentrations in tris buffer using ICP, Ca-ISE and F-ISE, respectively. FTIR was also used to establish the formation of FAP.
Results: As fluoride content increases, the concentration of fluoride released into tris buffer increases (fig. 2b and 2c) . At 0.5F onwards the fluoride release increases with time with the increase becoming more pronounced as the fluoride content increases. The 5F plateau (fig 2b) suggests fluoride is being precipitated in the gum base.
Calcium, Fluoride And Phosphorous ratios
Fluoride content (wt%)
Ca ppm
F ppm
Ca/F
187.5
0.014
13389:1
0.25
156.8
0.19
825:1
0.5
131.4
0.8
164:1 1
127.7
1.5
85:1 5
70.43
6.82
10:1
Fluoride content (wt%)
Ca ppm
P ppm
Ca/P
187.5
43.11
4.35:1
0.25
156.8
59.32
2.64:1
0.5
131.4
47.53
2.76:1 1
127.7
29.8
4.28:1 5
79.43
20.53
3.43:1 .
Fig 3. FTIR shows apatite-like peaks starting to form around the 1030cm-1 and 600cm-1 region (Mneimne et al 2011).
Table 2a and b: A ratio of 0.1 Ca/F falls within the range needed for fluor-hydroxyapatite (FHA) to form i.e (Table 2a).
A ratio of 3:1 Ca/P is achieved from 5F, ideal for FAP formation (Table 2b)
Fig 2b. Fluoride release (ppm) against time (mins). Fig 2c. F release against F wt% .
References: Bowen et al, Caries prevention--fluoride: reaction paper. Adv Dent Res. 1991, 5:46-9. De Paola et al, CaF2 in enamel biopsies 6 weeks and 18 months after fluoride treatment Caries Res. (1991), 25: Hench, The Story of Bioglass, J Mater Sci: Mater Med, 2006, 17: Larsen et al, Saturation of human saliva with respect to calcium salts. Arch Oral Biol. (2003) 48(4): Lin et al, effects of fluoride chewing gum on stimulated salivary flow rate and fluoride content, J Dent, 2004, 32 6: Mneimne et al, High Phosphate content significantly increases apatite formation of fluoride-containing bioactive glasses, Acta Biomaterialia, 2011, 7: Reynolds et al, Remineralization of Enamel Lesions by Various Forms of Calcium in a Mouthrinse or Sugar-free Chewing Gum J Dent Res (3):