Table 1: Details of the restorative materials used in this study.  

Sample preparation

A total of 60 discs are created from these three materials using custom-built moulds with a diameter of 3 mm and a thickness of 8 mm, as shown in Figure 1. To release any air bubbles and remove extra material, a clear acetate sheet with glass slabs was put below and above the material-filled moulds, as shown in Figure 2. The disk was then cured according to each material's manufacturer's specifications, as shown in Figure 3. The discs were completed with a hand instrument.

Figure 1: SP 1.

Figure 2: SP 2.

Figure 3: SP 2.

Fluoride releasing measurement

Each disk will then be immersed in a 15 ml securely sealed centrifuge tube containing 10 ml de ionized distilled water to remove any ions from the water, and the tubes will be kept in an incubator at 37±1˚C.

A fluoride ion selective electrode (ISE) MM 41 MultiMeter designed and manufactured by CRISON INSTRUMENTS, Made in EU, was connected to a digital ion analyzer to calculate fluoride releasing readings. The electrode was calibrated using a standard solution of NaF at successive dilutions of 10-1,10-2,10-3,10-4, and 10-5 ppm F-, as shown in figure(4). Each solution's concentration is shown in millivolts on the instrument display (mv). The measurement was then converted to molarity using the calibration curve, and then multiplied by 1000 times the atomic weight of fluoride to convert to ppm. (10) At 7 days and 28 days, the quantity of fluoride emitted was measured.

Figure 4:Fluoride release.

The Statistical Package for Social Science (SPSS version 21) was used to examine the data statistically (Chicago, Illinois, USA). The difference between k independent groups was tested using One Way Analysis Of Variance (ANOVA) and Dunnett T3 tests (Unequal variance). All tests had a p 0.05 significance level.

Results

Results in Table 2 show that in each group the fluoride release is higher in 7-day than that in 28-day with significant finding in GIC while not significant difference in other two groups.

Table 2: Descriptive and statistical test of fluoride release among storage period by groups.

Our findings show that equia has the most fluoride release in each storage period, followed by Activa, and Predicta have the least. There is a significant difference in each storage period, with the most difference found in the first week compared to the fourth week. Following that, after multiple comparisons, there is a significant difference in the first week when comparing each group to each other, while after four weeks, all results are significant except when comparing Activa with Predicta the result is not significant (Tables 3 and Table 4) (Figure 4).

Table 3: Descriptive and statistical test of fluoride release among groups by storage periods.

Table 4: Multiple comparisons of fluoride release among groups by storage periods using dunnett T3.

Discussion and Conclusion

Fluoride release

Fluoride is released from restorative materials in different stages. Water is the first to diffuse into the substance, followed by fluoride ion dissolution and diffusion out of the material [11]. Several variables influence the complicated process of fluoride release from restorative materials. The quantity of fluoride released is affected by intrinsic characteristics such as the material's composition, solubility or porosity [12].

Our findings revealed a statistically significant difference in fluoride release across the three tested materials, with Equia forte HT samples having the greatest fluoride release, followed by active samples, and Predicta samples having the lowest. The F content in these materials is directly related to the increase in the quantity of F released by raising the F concentration gradient between the material and the solution [13].

Furthermore, because the matrix synthesis of GI-based materials is a maturation process, it slowed F release by reducing F diffusion. [14]. Hardness and maturation are increased [15]. It has previously been demonstrated that the curing process, whether light or chemical, influences fluoride release from glass ionomers, resin modified glass ionomers, and dualcured resin materials, and that photo initiated polymerization enhances cross-linking density, resulting in lower resin matrix permeability for fluoride ions [16,17].

However, because Equia Forte ht Fil is a chemically cured material, our findings of increased fluoride emission in non-light cured Equia samples cannot be explained by increased cross-linking due to light curing. Because of the aforementioned problems, Equia may have received the highest F rating. The kind and amount of resin used in RMGICs (active) must be considered, such as UDMA resin, which is a hydrophobic polymer with low water sorption and solubility [ 18,19]. Their hydrophobic nature, supplied by UDMA, results in decreased water absorption and filler dissolution. As simple as it may appear, the level of fluoride ions freed by RMGICs is lower than that of GICs, which might be due to the UDMA changing the acid-base interaction, resulting in less fluoride release [18,19].

The equia specimens emitted fluoride ions in the first 7 days (12.470 -20.010 ppm) and more than discharged by the second period, according to our findings (7.300-17.060).

The substantial amount of fluoride emitted in the first few days is referred to as "The Initial Burst Effect," since Fluoride release from glass ionomer is constrained by concentration and diffusion in the matrix as well as the particles.

Following the initial acid dissolution of powder particle surfaces, a significant amount of fluoride becomes part of the reaction product matrix; this fluoride diffuses rapidly from the matrix exposed on the material's surface and is gradually substituted by fluoride diffusing from the matrix beneath the surface [20-22].

RMGI (activa) shows similar dynamics of fluoride release, An acid-base interaction occurs between carboxylate groups of the acidic monomer and F-containing glass-fillers when resin-based ion leaching materials comprising ionomer-like fluorosilicate glass absorb water, resulting in the release of fluoride ions[23].

As the raw material of the specimen is resinmodified glass ionomer cement, one of the hardening mechanisms of this material is the acid-base reaction; this can be explained by the rapid elution of fluoride liberated as a result of the acid-base reaction, which takes place on the particles glass surface. This was consistent with a number of in vitro investigations that found increased release of fluoride in the first several days than in the last 28 days [18,19,22, 24].

All glass-ionomer systems have an acid/base hardening reaction owing to their glass particles and polyacid components, as well as light and chemical cure capabilities due to their "bioactive ionic resin matrix" component, are all involved in the hardening mechanisms of the Activa resin samples tested in this study [25].

The kind The fluoride release potentiality of resin modified glass is affected by the kind and amount of resin used in the photochemical polymerization technique, as well as the formation of complex fluoride compounds and their interactions [26].

The data showed that the fluoride leakage decreased during the next few days. This was caused by the slower disintegration of glass particles through the pores of the repairs over time. Bulk fluoride release occurs throughout the maturation stage as a result of material interaction with the storage media. This was consistent with other research [18,21,27].

Predicta samples had considerably lower fluoride release than Equia and Activa samples, and there is no significant variation in fluoride release between the two periods. It most likely includes bioactive glass. The breakdown of bio glass rapidly raises the concentration of fluoride ions; nevertheless, the contribution from the dissolution process is extremely little, possibly because to the presence of hydrophobic resins that rejects water.

It is possible that the impact of recharging fluoride is more than the effect of ion release in this material, and that the bioactivity property is greater than the effect of ion release. There is no detailed information available on the composition of predicta bulk bioactive composite, and no study has been conducted. More research is needed to understand the composition and other features of this novel composite.

Fluoride is released from composite resins and RMGIC via the diffusion process [28]. Because the free flow of water is likely hindered in the cured resin matrix, the fluoride source surrounded by a resin matrix may have trouble coming into touch with water. In 1997, Kanchanavasita, Anstice, and Pearson published Kanchanavasita, Anstice, and Pearson [29]. When they evaluated the water sorption qualities of cements, they discovered that GICs and resin-modified glass-ionomer cements absorbed more water than a resin composite. In 1998, Martin and Jodynakiewicz [28,30]. This might explain why resin-modified glass-ionomer cements and glass ionomer cements released more fluoride than fluoridereleasing resin composites, as demonstrated in this work.

Because the release is governed by the mix of filler particles and the matrix of set material, fluoride release after setting continued to follow the same pattern in all three groups in our investigation: Fluoride ions diffuse through the pores of the substance [31]. Previous research on GICs and resin modified GICs found the similar pattern of fluoride emission [18,19,22,32].

Conclusion

In comparison to the predicta bulk bioactive, the active kids exhibited higher fluoride ions release concentrations. The CGI, on the other hand, showed larger fluoride ion release concentrations than the other two materials.

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