The significant advancement in the understanding of the caries process enables the treatment or arrest of dental caries in its early stages by remineralization. Even though the process of tooth remineralization has been researched for decades, there is a scarcity of solid data on remineralization in primary teeth enamel. [1–5]
Many in vitro and in vivo investigations have been undertaken to determine the optimal fluoride treatment for the prevention of tooth decay [22, 23, 24]. The most effective treatment regimen has been thought to be a high-frequency application of low doses of fluoride compounds. However, in instances when there is a significant risk of caries, the use of a technique that uses a high concentration of fluoride, such as professionally administered products, has been recommended. In early enamel lesions, both fluoride varnish and SDF have been suggested as treatment strategies especially in young children due to their easy application and safety. [5, 24, 25, 26]
As a result, the goal of this study was to compare the mineral content and lesion depth of artificial enamel caries treated with 5% NaF varnish (Clinpro™ white varnish 3M Espe, MN, USA ) ,5% NaF containing CPP-ACP varnish (MI varnish,GC, Tokyo, Japan) and 38% SDF (Globus Medisys Gujarat, India) in primary teeth .
In-vitro models are criticized because the pH in the oral cavity changes often relying on oral hygiene and an individual's dietary habits, making it impossible to precisely imitate the oral conditions that occur in the mouth. However, an in-vitro model was used in the current study as it allows for more control over these factors, and because artificial lesions are more homogenously produced [8, 10, 11]. Moreover, the used pH cycling model was found to be the most accurate in simulating the in-vivo situations, such as frequent demineralization attacks in high-caries-risk individuals. [12, 13]
When examined using EDX, all groups showed non-significant differences in Ca, P, F content or Ca/P compared to each other though significant differences were found compared to control teeth except for F content indicating that the 3 topical agents are effective in remineralizing decalcified enamel offering resistance to acid challenges. Ca and Ca/P mean values were highest in MI varnish followed by ClinproTMwhite varnish & SDF groups.
Fluoride content in the 3 agents enhances precipitation of minerals and remineralization of decalcified tissues [21, 27]. Although fluoride content in SDF is much higher than MI and Clinpro TM white varnishes, yet the adhesiveness of varnishes that allows prolonged contact with enamel and sustained controlled release of fluoride and other minerals may have contributed to the higher Ca content and Ca/P in MI and Clinpro™ white groups.
Moreover, CPP in MI varnish may have further contributed to a better remineralization by stabilizing ACP nanoclusters preventing them from growing to the threshold size for phase transitions keeping Ca and P ions freely accessible to diffuse into mineral-deficient lesions. [46, 49] Additionally, MI varnish was found in one study to exhibit the highest fluoride ion release compared to Clinpro TM white and SDF. [30]
The results of the present study were compatible with the results of Savas et al, 2016 [31], who found that the Ca/P ratio was significantly greater in the remineralization phase after a single application of MI varnish compared to demineralized surfaces in bovine incisor teeth. Our results also support the findings of Kariya et al, 2016 [29] who found that CPP-ACP interacts with fluoride ions to create an additive remineralization effect via the development of a stabilized amorphous calcium fluoride phosphate phase. Furthermore, our data matched those of Shen et al, 2016 [32], who concluded that MI Varnish was superior to Duraphat, Profluorid, Enamel Pro, and Clinpro™ White varnishes in preventing enamel demineralization in permanent teeth.
Results also matched those of De Carvalho Filho, 2011 [33], and Hicks et al, 2004 [48] where Clinpro™ white treated specimens showed significantly greater mean Ca content and Ca/P compared to control.
According to an in - vitro study, a Ca and P rich layer was formed on the surface of decalcified enamel following the application of SDF compared to non - treated decalcified enamel, which also justifies the findings of present study. [16, 34]
Our findings also showed that, there was no significant difference between different groups in mean F content although the highest value was found in SDF (0.93 ± 1.18). This finding might be attributable to the flowability of the SDF solution. Because SDF is a liquid, it may make complete contact with the enamel surface in a short period of time [11] or due to the SDF’s high fluoride content which is nearly double that of Clinpro™ white and MI varnishes. [11, 35]
Assessment of lesion depth is an important treatment outcome to assess the depth of effect of the remineralizing agents in the body of enamel lesions and not only the superficial effect. According to the present study, all fluoride varnishes and SDF exhibited reduced mean lesion depth values when compared to untreated control.
Our findings are in line with Santos, et al, 2009 [35] that examined the effects of various fluoride agents (gel, varnish, toothpaste) on the acid-resistance of primary-tooth enamel by measuring lesion depth and discovered significantly lower values for lesion depth in all the fluoride groups when compared to a control group that was not treated with fluoride.
When comparing MI varnish to the Clinpro™ white varnish and SDF, the MI varnish treated specimens exhibited a significantly lower mean lesion depth. This may be related to the addition of fluoride to CPP-ACP which aids in the formation of CPP-ACPF nanocomplexes that combine calcium and phosphate with fluoride ions at the tooth surface. This higher concentration of calcium, phosphate, and fluoride ions on the tooth surface causes ions to better diffuse into the enamel and subsurface lesion, resulting in higher amounts of remineralization and fluoride incorporation [8, 30, 36, 37, 38]. Additionally, the nano-sized particles of CPP-ACPF nanocomplexes may have caused better penetration depth of the remineralizing ions [4]
Our findings agreed with Cochrane et al, 2014. [30] and Agnihotri et al, 2011[39] who found that when CPP-ACP was combined with fluoride, it reduced caries score and inhibited demineralization of sound enamel.
However, this in-vitro study had certain limitations, such as difficulty mimicking the oral environment. In-vitro remineralization may be quite different when compared to the dynamic complex biological systems which occur in the oral cavity. Additionally, the antibacterial effect of the 3 tested agents was not taken into consideration where the clinical remineralization of carious lesions may be enhanced through availability of free mineral ions as well as the antimicrobial action of the used agents given that carious lesions are developed because of acid production by cariogenic bacteria. Therefore, due to the evident limitations of in-vitro investigations, caution must be used when making direct interpretations to clinical circumstances.