Dentists have two main ways of applying Fluoride topically to your teeth. One method is to apply either a week solution or a gel which is a gentle way of poisoning you every 6 months that you go for a checkup. The other is a spot application of a highly concentrated solution of Silver Fluoride which is usually applied to cavities in children’s teeth. The concentration is so high that it presents a serious health risk to the child. In 1997 the Australian Dental Association published the following article in the ADA Journal. Interestingly the ADA still promote the use of fluoride for everyone.

Remember that you have a right to refuse fluoride treatment from your dentist!

Published in ADJ 1997

Safety issues related to the use of silver fluoride

in pediatric dentistry

Theo Gotjamanos, BDS, MDS, PhD, FRACDS, FFOP(RCPA)*

Abstract

Due to its exceedingly high fluoride content, 40% silver fluoride solution has the potential to cause fluorosis when used in young children. In vitro testing conducted in the present investigation indicates that application of 40% silver fluoride to deep carious lesions or its use as a 'spot' application agent could result in 3 to 4 mg of fluoride reaching ; the systemic circulation.

As scientifically-based clinical trials on the safety of 40% silver fluoride have not been conducted, it would be appropriate for it to be withdrawn from further clinical use until proper testing and evaluation have been carried out. In view of the possibility that lower strength solutions of silver fluoride (1-4%) may be just as effective as 40% in 'arresting' deep caries, testing should focus on such solutions, particularly as the potential for toxicity from their fluoride content would be reduced by a factor of 10-40.

Key words: Silver fluoride, toxicity, fluorosis. (Received for publication December 1994. Revised June

Introduction

Since 1984, the School Dental Service in Western Australia has used a 40% aqueous solution of silver fluoride as the standard treatment for deep carious lesions in primary teeth. The same strength solution has also been tested for its caries-preventive effect as a topical agent on the occlusal surfaces of newly erupted first permanent molars.' Although controlled trials of the efficacy of applying 40% silver fluoride to proximal surfaces of primary teeth do not appear to have been conducted, such a procedure has also been used routinely by dental therapists working for the Western Australian Health Department.

In view of the very high fluoride levels found in commercial preparations of silver fluoride,2 the aim of the present investigation was: (1) to determine the amount of fluoride that is deposited within a carious cavity as part of the 'atraumatic' technique; (2) to estimate the amount of fluoride that is deposited intra-orally as part of a 'spot' application of silver fluoride; and (3) to discuss the potential hazards of such procedures in young children.

Results

There was considerable variation in the size and masses of individual cotton pledgets ranging from 2.5 mg to 16.6 mg (mean 8.2 + 3.0; n = 55). A similar large variation in masses of pledgets containing absorbed AgF was found: 26.9 mg to 80.2 mg (mean = 55.8 + 14.4; n = 55), with the pledgets of lightest mass not necessarily holding the least amount of AgF. Net mass of AgF solution held by the cotton pledgets ranged from 23.7 mg to 71.9 mg (mean 47.6 mg + 12.4; n= 55). Net mass of AgF retained by carious teeth after application of pled gets to carious cavities (determined by subtraction) varied between 2.6 mg and 16.6 mg (mean 10.7 mg + 3.7; n = 25).

During the 'spot' application procedure, the mass of silver fluoride deposited in the vicinity of the respective distal and mesial surfaces of first and second primary molars (determined by subtraction) was found to range from 1.2 mg to 15.2 mg (mean 5.2 + 3.4; n = 36). Thus, for a full mouth 'spot' application (4 separate applications, one to each quadrant), 20.8 mg of silver fluoride would be deposited.

Using the 36 actual readings obtained for each sample weighed, and grouping these seriatim into groups of 4 to represent a 4-quadrant application, the mass of silver fluoride that a child could receive orally was found to range from 12.0 mg to 33.8 mg.

Discussion

There are three major safety issues concerning the clinical use of 40 per cent AgF solution:

(1) Accidental swallowing by a child of an AgF impregnated cotton pledges should it become dislodged from tweezers while being held in the mouth.

The present study has shown that the amount of silver fluoride contained in a cotton pledget from which excess solution has been removed ranges from 23 to 91 mg. Based on a fluoride ion concentration of 12 per cent ,2 this translates into a fluoride ion mass of between 2.8 mg to 10.9 mg.

According to Whitford,3 the 'probably toxic dose' of fluoride is 5 mg F/kg of body mass, while a dose of 4 mg F/kg body mass may be fatal for a young child. Average body masses of children aged between 4 and 6 years range from 15 to 20 kg. Therefore, accidental swallowing by a 4-6 year old child of 2.8 to 10.9 mg of fluoride contained within a cotton pledges represents a fluoride dose of between 0.14 and 0.73 mg F/kg of body mass. While such a dose is considerably less than the 'probably toxic' and lethal doses for young children, nevertheless, considerable care needs to be taken at all stages of the 'atraumatic' procedure. Failure to remove excess AgF solution from a cotton pledges prior to application to carious dentine could raise the fluoride dose to a level close to half the toxic dose.§

Should accidental swallowing of AgF occur, emergency procedures as described by Whitford3 and Ekstrand et al.4 must be implemented immediately. These include induction of vomiting in the conscious patient, oral administration of calcium gluconate or calcium chloride, or milk if either of these solutions are unavailable. The patient needs to be hospitalized as soon as possible for additional emergency treatment and monitoring of vital signs.

(2) Dentine and pulp permeation of fluoride and its subsequent entry into the systemic circulation following AgF application to carious and sound dentine.

According to data from the present investigation, between 2.6 and 16.6 mg of AgF could be deposited within carious dentine during application of AgF to a single carious cavity. This equates with a fluoride dose of up to 2.0 mg F per application.

The School Dental Service in Western Australia advises its dental personnel not to use the 'atraumatic' technique on more than four teeth in any one appointment. If half the fluoride that is released from AgF deposited in a carious cavity that extends close to a pulp horn can enter the systemic circulation via the dental pulp, then a patient who has had four teeth treated at the one sitting could receive in the order of 4 mg of fluoride systemically. Such a dose for a 4 to 6 year old child has the potential to cause Fibrosis of incisor and canine teeth, the crowns of which are still developing at 6 years of age.

(c) Oral ingestion of fluoride following topical application of silver fluoride solution to proximal surfaces of primary molars.

The 'spot' application procedure used by dental therapists employed by the School Dental Service in Western Australia is carried out at a single appointment. It entails four separate applications to the respective distal and mesial surfaces of first and second primary molars in each quadrant. If the same cotton pledges is used for each application, it may be re-dipped into silver fluoride solution prior to being applied to a new quadrant; alternatively, a new cotton pledges may be used for each separate application.

By applying moderate pressure via the tweezer tips to express some of the fluoride solution from the cotton pledges when applied to the marginal ridges of two adjacent teeth, the amount of fluoride

released has been calculated in the present study to range from 12.0 mg 33.8 33.8 per application to 4 quadrants.

Based on a 12% fluoride ion concentration in 40% silver fluoride,2 and assuming that up to 30% of the fluoride in the expressed solution could be incorporated into enamel during the 'spot' application procedure, the total residual fluoride that could be available for incorporation into crevicular fluid and/or saliva following 'spot' application to 4 quadrants is between 1.0 mg and 2.8 mg. This represents an estimate of the total amount of fluoride that could be ingested by a child receiving 'spot' application of silver fluoride to 4 quadrants at one appointment.

It is important to note that the estimated amount of 1.0 mg to 2.8 mg assumes only a single 'spot' application is made to each quadrant, that is, unlike other forms of topical application of a fluoride solution, the cotton applicator is not dipped several times into solution and re-applied to the teeth to ensure that they are kept moist for a 2 to 4 minute period. A conscientious dental therapist or dentist, who routinely uses several topical fluoride agents, could unintentionally misuse silver fluoride solutions in this way, re-dip and re-apply a cotton pledges several times to each of 4 quadrants, and thereby administer very high dose of fluoride to a young child. Even in the absence of such misuse, oral ingestion of 1.0 mg to 2.8 mg fluoride, when added to fluoride consumed from all other sources (water, beverages, food, toothpaste) would probably be sufficient to cause fluorosis in the permanent anterior teeth of children under the age of 7 years

With respect to the possible link between silver fluoride use and dental fluorosis, unless controlled clinical investigations have been conducted to determine whether the 'atraumatic' technique or the 'spot' application of silver fluoride can cause clinically detectable fluorosis or any other adverse effect, the assumption that such procedures do not result in adverse effects cannot be made. As controlled clinical testing of the safety of 40% silver fluoride has not been carried out, the onus is on the Western Australian Health Department, and other Government or private institutions which also advocate its clinical use, to conduct scientifically based clinical trials, or to arrange for such trials to be conducted on their behalf. Those responsible for the assessment of the presence or absence of adverse effects should not be aware of the particular treatment received by test and control subjects, that is, a 'double-blind' protocol should be followed. Until such testing is conducted and evaluated, it would be appropriate for the routine clinical use of 40% silver fluoride in paediatric dentistry to be suspended as a precautionary measure.

As the silver component of aqueous silver fluoride solution may play the principal role in arresting caries and preserving pulp vitality through its antibacterial properties and its ability to seal dentinal tubules,5 consideration should be given to abandoning the 40% solution and conducting laboratory and clinical testing of low strength silver fluoride solutions.

If silver ions at concentrations of 20-200 ppm can be lethal for organisms such as Streptococcus mutans,6 it may be unnecessary to use 40% silver fluoride containing ppm silver ions to 'arrest' carious dentine. Solutions ranging in concentration from 1 to 4% may be just as effective. Fluoride levels in such solutions would be in the order of ppm, with a corresponding decrease in the risk of toxic effects due to ingestion of excessive quantities of fluoride.

Animal investigations aimed at testing the effect of low strength silver fluoride solutions on the initiation and progression of dental caries are currently in progress in the Department of Pathology in the University of Western Australia. The results of such investigations will be reported in due course.

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