|Silver Diamine Fluoride: Review of Positive Usage Against Caries
Caries is one the most prevalent oral diseases in most third world countries of our time. The lack of specialists, proper sanitation methods, and poor oral hygiene in these areas allows this infection to run rampant, especially among children and the elderly. Caries is a multi-staged bacterial growth, relying on several different bacteria to initiate and progress, both through the enamel and eventually into the root of teeth. Many measures have been proposed to put a halt to it’s spread, such as fluoridating water supplies or professional fluoride application, but are either too expensive for the regions affected or the proper professionals are too few in number for such actions to work with great effect. However, silver diamine fluoride (SDF) has recently received a push for application to fight caries. While few studies exist that support it’s positive outcomes, the ones that do prove that SDF is an incredibly inexpensive and effective compound that both slows and halts caries progression. This review will examine the positive aspects of silver diamine fluoride, it’s development in dentistry, and whether the concerns over it’s safety and disadvantages outweigh it’s advantages.
Due to adequate oral hygiene instruction and readily-available resources for increasing dental IQ, silver diamine fluoride is relatively unheard of in most first world countries. These areas are not affected by degenerative oral infections, at least no more than an occasional case. However, in countries where these resources are lacking or not accessible to most of the population, SDF has become a familiar treatment. Specialists using SDF “[date] back to the early 1960’s where it was shown to be successful in arresting caries” (Chen 2). Surprisingly though, SDF “has been accepted as a therapeutic agent by the Central Pharmaceutical Council of the Ministry of Health and Welfare in Japan for dental treatment since the 1960’s” (Hung 35) where it is offered as an inexpensive treatment to those with low income to combat an infection that becomes gradually harder to control and halt.
SDF has one main purpose, which is to “arrest and slow the rate of caries progression” (Chen 2). One of the main factors that makes caries such an uncomfortable and painful infection is that it is brought about by poor oral care. Once the infection roots, it becomes difficult for a patient to properly clean and maintain their whole dentition due to the pain that caries causes to the pulpal layer. It slowly breaks down the dentine mineral lining causing hypersensitivity which adds to the discomfort and makes care more difficult. SDF can successfully fight this “by combining the tooth-strengthening effect of sodium fluoride (NaF) and germicidal effects of silver nitrates on HA and bacterial survival” (Chen 2). By reducing the reproductive ability of bacteria on the teeth, “SDF inhibits the demineralization of dentin” (Mei 1). This process creates a “weakly soluble silver phosphate layer” (Chen 6) ceasing caries progression due to it becoming a “hard…impermeable layer on the tooth surface” (Chen 6). While helping to “promote remineralization of tooth mineral hydroxyapatite (HA)” (Chen 2), it also “reacts with HA to form fluorapatite (FA), which is more resistant to decay’ (Chen 2). The complete reaction that SDF causes helps “to manage dentine hypersensitivity” (Chu 12) due to layers of enamel being rebuilt and “[increasing] the hardness of carious dentine” (Chu 12). SDF also continues to protect the teeth after application by “[preventing] the formation of Streptococcus mutans [and] Actinomyces naeslundii mono-species biofilms” (Mei 1), both of which are major contributors to caries initiation and further root development. While this effect is remarkable, the number of studies addressing this is relatively sparse.
As mentioned previously, few studies have been undertaken on SDF treatment with a strong basis that excludes bias and firm direction. Most studies on “the effectiveness of SDF [have] a limited scope of control comparisons” (Chen 2) and therefore, lack a solid conclusion that can be stated without any flaws in their procedures. Because of the sporadic test parameters, there are few studies that are looked at as true portrayals of SDF efficacy. Even these are colored in their perspective due to the fact that “[much] of the available data was collected in vitro and lacks insight on the in vivo, long term effects of these interventions” (Chen 2), ignoring whether SDF carries any long-term effects on the subjects, positive or negative. However, there are a select few that are agreed to properly document whether SDF is an effective means to combat caries. These studies all show a common agreement: SDF can successfully prevent and halt caries progression. One study in particular “on 220 young children was carried out in Japan and found a 52% reduction in caries severity” (Hung 44) after treatment. These results were only strengthened by “a 47% reduction in teeth with new caries” (Hung 44) proving that SDF not only halts the infection from becoming worse, but it also prevents it from spreading to the rest of the mouth. Several studies were conducted with varying degrees of solution strength applied to carious lesion sites ranging from 0.2% SDF mouthwash solutions to 38% SDF topical solutions. These results were compounded to conclude “that regular application of 38% SDF solution (annual or biannual) can be used to arrest carious lesions” (Chen 4). This treatment also displayed signs of continued bacterial inhibition over time that held off the recurrent carious lesions. This effect only seemed to “[last] for the first 6 months, suggesting that the efficacy of SDF decreases with time” (Chen 4) and lesions reappear with higher frequency past this point. The effect is merely lessened after six months though, as one study demonstrated that “a three minute application of SDF was adequate to demonstrate an effect over three years” (Chen 4), however with a diminishing return. After careful review of these studies, it can be concluded that “SDF is more effective at arresting caries while just as effective in preventing dental decay” (Chen 7) as most common, expensive means of control. This begs the question of whether this effectiveness comes with any downsides.
SDF carries with it the potential of harmful side effects, mainly due to it’s two main components: silver and fluoride. Silver, being a heavy metal, has raised the issue of heavy metal concentration accumulation in the patients that receive SDF treatment. These have largely been dismissed as being too minuscule to account for a great concentration building even over time and with continued treatment. However, the “use of SDF has raised concerns in regards to to it’s [other] adverse effects, mainly fluorosis and pulp toxicity” (Chen 5). Fluorosis is the accumulation of fluoride within the body that is commonly associated with oral fluoride treatment where the body has “a significantly higher concentration of fluoride than the expected fluoride level of 60,000 ppm” (Hung 42). The point has been made; however, that because of the “less frequent and lower concentrations of SDF [applications, it] could completely eliminate the concern for fluorosis” (Chen 6). The most common issue that cannot be dismissed from SDF treatment is the silver phosphate layer that forms upon application to carious regions of the tooth. This layer is photosensitive and when exposed to light, “[black] staining was noted following SDF application in three of four studies” (Chen 1) that is both impermeable and “black permanently” (Fung 3). This raises concern for accepted treatment considering most esthetic countries, such as our own, would view this as a major issue that cannot be overlooked. This black stain bears no physical harm to the patient though, which gives a little less weight to it’s negativity when faced with the issue of whether to save one’s teeth from decay or not. The only other issue to arise from SDF usage is “in one study, 3 patients developed mild, painful white mucosal lesions where accidental contact of SDF with the gingiva occurred during application” (Chen 4). These slight lesions have been reported in few other studies and merely result from when the solution is accidentally applied to the sensitive areas normally unaffected by caries. These lesions, while worrisome, “disappeared after 48 hours without any treatment” (Chen 6) proving they were of no long-term harm. So with most disadvantages of SDF being easily countered or due to improper use, there are only positives left. SDF applications are proven to be “significantly less expensive than standard treatments” (Chen 6) making them very attractive for widespread use, especially in areas and for those who cannot afford more expensive methods. Silver diamine fluoride “allows for treatment and prevention at the same time, is easy to apply, non-invasive, requires minimal training, and is inexpensive” (Chen 2). Overall, the advantages and lack of safety issues of SDF heavily outweigh any disadvantages.
SDF presents itself as a cost-effective and truly effective means to fighting caries. It’s germicidal, constructive abilities coupled with it’s low risk usage help to prove the point of why it’s accepted but several countries as a safe and effective means of caries control. While it does have a sparse research base that exists on solid groundwork, the data is there to prove that it is effective at controlling an oral infection that renders it’s victims unable to proper care for themselves. Throughout this paper, all aspects have been studied and in doing so have only proven that it truly is a viable means to treatment and prevention. Perhaps with time, this compound will be accepted as an probable choice for treatment by everyone, regardless of it’s one true fault: the stain it leaves. There have been strides to discover a way to get rid of this effacement. With the idea that it’s possible, maybe with the right direction it would be possible.