The effectiveness of sodium fluoride iontophoresis in patients

Dental Research

The effectiveness of sodium fluoride iontophoresis in patients withsensitive teethMichael A. McBride* / Russell 0. Gilpatrick** / Wiley L. Fowler'

This study investigated the use of iontophoresis in altering the sensitivity level of teeththat displayed thermal and tactile hypersensitivity. A total of 95 teeth were treated withan iontophoresis instrument. Forty-eight of these teeth were treated with a placebo ofdeionized water, and 47 were treated with a 2% sodium fluoride solution. Two of the 47teeth receiving sodium fluoride had identical pretreatment and posttreatment .sensitivityratings, while 40 teeth (85.1%) demonstrated a reduction in sensitivity. Twenty-nine ofthe 48 teeth receiving the placebo demonstrated no change in sensitivity. All teeth receiv-ing the placebo were re-treated with sodium fluoride. Forty-seven (97.9%) respondedwith reduced levels of sensitivity. {Quintessence Int 199!,-22:637-640.)

Introduction

In the United States, iontophoresis was first used fordesensitiïation of dentin by Siemon' and Manning.-Iontophoresis is also used for treatment of aphthoustilcers, lichen planus, herpes labialis,̂ "^ and hyperhy-drosis,'" for diagnosis of cystic fibrosis," for anesthesiaof the tympanic membrane,'' and as a local anesthesiafor minor surgery of surface tissue.

Iontophoresis utilizes a low-amperage direct electri-cal current to introduce ions or ionized drugs intotissue. This procedure allows a concentrated appliea-tion of the drug in a desired localized area. A muchhigher dose of drug can be introduced into the areato be treated without the systemie effects of conven-tional oral or parenteral drug therapy. Normally, ion-ized drugs will not penetrate tissue rapidly enough to

Assistant Professor, Depariment of General Dentistry, Univer-sity of Tennessee, Memphis, College of Dentistry, B75 tJnionAvenue, Memphis, Tennessee 38163.Associate Professor, Department of General Dentistry, Univer-sity of Tennessee, Memphis.Deceased.

be of therapeutic value. By applying the appropriatelycharged direct electrical current, ionized drugs can bedriven into tissue based on the principle that likecharges repel and opposite charges attract. For ex-ample, fluoride exists as a negative ion. By applyingfluoride under a negatively charged electrode, thefluoride can be driven with a direct electrical currentinto the tooth structure.

Grossman" stated that the treatment for dentinaldesensitization should be relatively nonirritating to thepulp, relatively painless, easily applied, and consist-ently and permanently effective; should act quickly;and should not cause tooth discoloration. Gangaro-sa''*" reported that fluoride iontophoresis fulfllls theserequirements.

The exact mechanism of this desensitization is notwell understood. A possible mechanism is that ion-tophoresis causes a microprecipitation of calciumfluoride that may block the hydrodynamically me-diated stimuli that induce pain. Wilson et al'* dem-onstrated that the surface of iontophoresis-treateddentin contained two to four times more fluoride thandid topically treated teeth and 24 to 30 times morefluoride than did control teeth. By etching off 4-iimintervals of dentin at a time, they were able to evaluate

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the fluoride content of each layer. Comparisons weremade between teeth treated wilh iontophoresis andothers to which only topical fluoride was applied. Thefourth layer showed that teeth treated with iontopho-resis had four to six limes more fiuoride content thandid those that were topically treated, and 50 to 70thïies more fiuoride than did the control. This con-centration of fiuoride gradually decreased after thesixth etched layer.

Dentinal pain may be caused by temperaturechanges, chemical changes, or tactile stimulation. Anyof these stimuli can, if continuous, cause pulpal irri-tation and possibly eventual necrosis. It would be inthe best interest of the patient to treat hypersensitivitybefore the pulpal infiammation eventually becomes anirreversible condition. Iontophoresis will block thesestimuli and stop them from irritating the pulp,"

There are always questions about the safety of pro-cedures used in any field. The safety of iontophoresisconcerning the pulp has been demonstrated in studiesby Scott,'* Lefkowitz," and Lefkowitz et al,'" Usingdogs, Walton et aP conducted a study of 78 teeth todetermine the effect of different treatment dosages ofiontophoresis on odontoblasts,'' The control groupreceived no treatment prior to extraction. The cervicalroot dentin of the remaining teeth was surgically ex-posed and then root planed. The teeth were dividedinto groups and treated as follows: with root exposureonly — no other treatment; with a single 1-mA/mindose of 2% sodium fluoride via iontophoresis; with asingle 5-mA/min dose of 2% sodium fiuoride via ion-tophoresis; with topical fluoride treatment; with elec-trical current dosage only; or exposed root surfaceswere ground with a diamond in an air-turbine hand-piece without water coolant.

The teeth were extracted at different time intervalsand examined histologically. The researchers conclud-ed that there was no statistically significant difference,at the histologie or ultrastructural level, in the odon-tobJasts of either the 1-mA/min or 5-mA/min ionto-phoresis dosage group and those of the unexposed,untreated group. This held true for both 7- and 80-day observation periods. It is still recommended thatthe normal dosage be 1 mA/min, Generally, a currentof 0,5 mA for 2 tninutes is used to treat dentinal hy-persensitivity.

Studies involving human subjects have reported awide variety of results; however, the trend toward suc-cess has increased in the more current studies,^^"" Thisis probably due to the refined technique and better,more rehable equipment.

Method and materials

The study consisted of treating selecicd teeth with ion-tophoresis using a 2% solution of --.oáiam fiuoride.Teeth were randomly divided into t w ¿loups. Group1 received 2% sodium fluoride at a current of 0,5 mAfor 2 minutes resulting in a 1-mA/min dose. Group IIreceived a placebo, ie, deionized water, under the sameelectrical dosage as that used with the 2% sodiumfluoride solution.

The teeth to be evaluated were isolated from adja-cent teeth and fissue by the use of cotton roll isolation,Stimuh, including air, cold water or ice, fruit juice, oran explorer tine, were applied to the tooth to assessthe patients' level of discomfort. The patient wasasked to rate the level of discomfort tising the follow-ing scale: 0 — no discomfort; 1 = mild discomfort;

2 = moderate discomfort; 3 = severe but transientdiscomfort; 4 = severe discomfort that confinued aft-er removal of stimulus.

All teeth that received a placebo and did not exhibita reduced level of sensitivity after treatment were re-treated with the 2% sodium fiuoride. All teeth thatresponded to treatment with 2% sodium fiuoride butwhose sensitivity was not reduced to zero were retreat-ed with an additional 1-mA/min dose of 2% sodiumfiuoride.

The patient's level of sensitivity was determined us-ing the previously described diagnostic parameters.The reported levels of sensitivity were entered on thediagnosfic form before treatment and immediately fol-lowing treatment.

Results

A total of 95 teeth were treated. Inifial treatment in-cluded 48 teeth that received a placebo (Fig 1) and 47that received sodium fluoride (Fig 2),

Ofthe 47 teeth receiving sodium fiuoride treatment,two teeth had identical pretreatment and posttreat-ment sensitivity ratings. Five teeth demonstrated aone-level reduction in sensitivity. Twenty-eight teethdemonstrated a two-level reduction in sensitivity.Twelve teeth demonstrated a three-level reducfion insensitivity. Forty teeth (85,1%) demonstrated a two-level or greater reduction in sensitivity. The averagepretreatment sensitivity rating for teeth receiving onetreatment of sodium fiuoride was 2,7. The averageposttreatment sensitivity rating for teeth receiving onetreatment of sodium fiuoride was 0,6,

Of the 48 teeth receiving a placebo as the initial

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Placebo group

Level of sensitivity

Fig 1 Pretreatment and posttreatment sensitivity in theplacebo group.

Sodium fluoride group

4 3 s

Level of sensitivity

Fig 2 Pretreatment and posttreatment sensitivity in the so-dium fiuoride group.

treatment, 29 had identical pretreatment and post-treatment sensitivity ratings. Eighteen teeth demon-strated a one-level reduction in sensitivity. One toothdemonstrated a two-level reduction iti sensitivity. Theaverage pretreatment sensitivity rating for teeth re-ceiving a placebo was 2.6. The average posttreatmentsensitivity rating for teeth receiving a placebo was 2.3.

The teeth initially treated with a placebo were re-treated with sodium fluoride if they did not exhibit atwo-level reduction in sensitivity. After re-treatmentwith 2% sodium fluoride, 13 teeth showed an addi-tiotial reduction in sensitivity by one level, 23 teethshowed a reduction in sensitivity by two levels, and11 showed a reduction in sensitivity by three levels.The average posttreatment sensitivity rating for teeththat first received a placebo and then were re-treatedwith sodium fluoride was 0.4. The average sensitivityrating for all teeth treated with one or two treatmentsof sodium fluoride was 0.4.

Chi-square tests were run to determine the statisticalsignificance of this information. Chi-square testing in-dicated that there was no statistically significant dif-ference between the pretreatment sensitivity levels ofteeth to be treated with a placebo and teeth to betreated with sodium fluoride or between the pretreat-ment and posttreatment sensitivity levels of teethtreated wilh only the placebo.

Chi-square testing also indicated that there was astatistically significant difference {P< .001) betweenthe posttreatment sensitivity levels of teeth treated

with a placebo and those of teeth treated with sodiumfluoride and between the pretreatment and posttreat-ment sensitivity levels of teeth treated with sodiumfluoride.

Discussion

In this study, most patients were treated under a cur-rent of 0.5 mA for 2 minutes while the iontophoresismachine was in an automatic mode. However, a fewpatients experienced some discomfort at this dosage,and these patients were taken off the automatic tnodeand placed on a manual mode so that the currentcould be increased incrementally to meet the patient'slevel of comfort.

It is worthwhile to explore some of the problemsencountered by the authors during the clinical trial toprevent similar problems for other practitioners. First,the patient must be grounded for proper conductionof the fluoride into the dentin. Any movement of theapplicator away from the tooth being treated will shortthe system and cause the patient to endure a smallshock. Being careful not to move the applicator duringthe 2-minute period will prevent this shorting.

One patient experienced severe discomfort duringan application, and it was found that this patient hada pin-retained composite resin restoration adjacent tothe treatment site. This pin was exposed on the lingualsurfaee and, being metal, drew all the current. Radi-ographs must always be checked before treatment.

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Since tissue will cause this same phenoinenon, isola-tion of the area to receive treatment must be strictlyapplied, because any tiietai or tissue will draw the cur-rent before dentin, elitninaling any hope of desensi-tization. This means that some areas of the mouth aremore accessible and therefore more easily treated.

Finally, it was found that if a tooth demonstratedsevere sensitivity, placement of the fluoride against thetooth eould elicit unwanted reactions from the patient.When patients presented with severe initial responsesat pretreatment, the fluoride, contained in a plastiebottle, was heated under warm tap water before ap-plication, and this seemed to help immensely.

Conclusion

Dentists are seeing more patients with cémentai anddentinal sensitivity today than they have in the past.This is due to many factors, such as the relativelycommon occurrence of periodontal disease, increasedlife expectancy, and the ability to retain teeth longer.Practitioners are being challenged to find answers tothese sensitivity problems. Many tnethods are avail-able for treating sensitivity, but only a few praetition-ers have reported complete or even hmited success intheir utilization. Because the success rates of thesedifferent methods are questionable at best, newermethods are being sought. An effective solution mayhave been found with the advent of controlled ion-tophoresis. The results of this study strongly supportthe use of iontophoresis as a reliable method of ob-taining significant reductions in levels of dentinal andcémentai sensitivity.

Acknowledgments

The authors lAtjuld like to express their thanks to Dr Diane Brownfor her assistance in the statistical support of this paper.

This paper is dedicated to the memory of our friend atid colleague,Dr Wiley L. Fowler.

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