Stannous Fluoride Solution Research Articles

Comparative efficacy of stannous fluoride and zinc sulfate solution to copper sulfate footbath solutions for the treatment and prevention of digital dermatitis in lactating dairy cows

The objective of this study was to determine whether a novel footbath solution containing stannous fluoride (SnF2) was superior to 5% copper sulfate solution for the treatment and prevention of digital dermatitis (DD) in dairy cattle. Study 1 was conducted over 4 weeks in Missouri and involved 34 lactating Holstein-Friesian cows with hind feet DD lesions. Cows in group SF walked through a footbath containing a proprietary formulation of SnF2 once weekly, whereas cows in group CS walked through a 5% CuSO4 footbath once daily for 5 d each week. Study 2 was conducted over 8 weeks in California and involved 40 lactating Holstein-Friesian cows with hind feet DD lesions. Cows in group SF walked through a SnF2 footbath for 3 consecutive days then once a week for the following 7 weeks. Cows in group CS walked through a 5% CuSO4 footbath 3 times each week for 8 weeks. Data collection included lesion type, lesion area, locomotion score, and pain score. Digital dermatitis was actively transmitted in study 1, and lesion area and locomotion scores were lower in group SF than group CS. In contrast, DD was not actively transmitted in study 2, and lesion area and locomotion scores were similar in groups SF and CS. Stannous fluoride delayed the development of active DD lesions in study 1 compared with copper sulfate, with a lower relative risk (0.57, P < 0.001) of a hind foot developing an active DD lesion over 28 d. However, SnF2 decreased the rate that active DD lesions transitioned to M3, M4, or M0 lesions compared with 5% copper sulfate in both studies, with the relative risk of a hind foot with an active DD lesion transitioning to M3, M4, or M0 in group SF being slightly lower in study 1 (0.83, P = 0.042) and study 2 (0.90, P = 0.020) than group CS. Our findings demonstrated that walking cows through a stannous fluoride footbath once per week in a herd undergoing active transmission of infection was more effective in preventing active DD lesions, but less effective in treating active DD lesions, than walking cows through a copper sulfate footbath 4 times per week. The novel SnF2 footbath solution shows promise for controlling DD in dairy herds that want an alternative footbath solution to CuSO4 and are interested in limiting the environmental accumulation of copper.

In Vitro Effect Of Fluoride Prophylactic Agents On Titanium Molybdenum Alloy And Stainless Steel Orthodontic Wires – Scanning Electron Microscope Study

Background: TMA (Titanium-molybdenum) and SS (Stainless steel) wires are most commonly availed for orthodontic treatment. Meanwhile, patients are encouraged to employ mouthwashes containing fluoride to maintain their oral hygiene. Objective: To assess the effect of different fluoride prophylactic agents on TMA and SS wires for specific time periods namely 10 minutes, 1 hour, 24 hours. Material and Methods: The sample comprised TMA and SS wires immersed in agents such as Artificial saliva (pH = 6.8), Acidulated phosphate fluoride gel 1.23% and Stannous fluoride 0.4% to evaluate surface changes incorporated. 180 cut wires were used in this study; out of which half were SS and the other half were TMA wires. These wires were immersed for 10 minutes, 1 hour and 24 hours in each agent. Scanning electron microscope was also utilized to analyze the surface alterations. Results: The roughness of these wires increased after immersing in prophylactic agents. An increase in the surface roughness was found with SS wires in stannous fluoridesolution and APF gel on immersion at 10 minutes, 1 hour, and 24 hours’ time intervals with p-value being significant at 24 hour time in stannous fluoride. Conclusion: Orthodontists must avoid the contact of orthodontic wires containing titanium protective coating with prophylactic agents. Bangladesh Journal of Medical Science Vol.22 (Special Issue) 2023 p.47-51

Sequence of stannous and sodium fluoride solutions to prevent enamel erosion

ObjectivesInvestigate the timing of stannous (SnF2) and sodium fluoride (NaF) application with and without salivary pellicle to prevent enamel erosion. MethodsHuman buccal molar enamel samples (n=120, REC ref 12/LO/1836) were randomly assigned to three groups testing SnF2 and NaF basic fluoride formulation and commercial mouthrinses with and without the presence of human saliva. Samples were randomly allocated to 2 subgroups: immersion in either fluoride for 1min either before or after citric acid immersion (0.3%, pH 3.2, 10min), and the cycle repeated 5 times. For human saliva group, samples were immersed in 80ml of natural saliva for 24h prior to the experiment. Analysis was done using non-contacting profilometry and microhardness change. Data were not normal and were log transformed. A linear model tested statistical differences between the groups. ResultsSnF2 application before erosion statistically reduced step height compared to application after erosion for all groups (solutions: 6.5μm (±1.2), 7.5μm (±0.8); p=0.01, mouthrinses: 3.2μm (±0.6), 4.2μm (±0.7); p<0.0001, mouthrinses with saliva: 2.5μm (±0.4), 3.1μm (±0.6); p=0.002, before and after respectively). In contrast, application of NaF before erosion increased step height compared to application after, but this was only statistically significant for the saliva group (before: 5.6μm (±0.3) and after: 4.9μm (±0.3); p=0.023). Presence of saliva increased microhardness change (p<0.0001). Within this group, greatest microhardness change was observed when SnF2 was applied before erosion and when NaF was applied after erosion (SnF2: 156.6KHN (±32.8), 123KHN (±20.1); p=0.02. NaF: 119.5KHN (±33.5), 218KHN (±24.9), before, and after respectively). ConclusionSnF2 reduced step height formation overall when compared to NaF, but particularly when applied before citric acid immersion. In contrast, NaF reduced step height when applied after citric acid immersion, but only in the presence of saliva. Clinical significanceStannous fluoride can be recommended over sodium fluoride to patients at risk of dental erosion and is optimally applied before erosion occurs. If sodium fluoride is to be used in the presence of saliva it is optimally applied after erosion has occurred.

The protective effect of SnF2 containing toothpastes and solution on enamel surfaces subjected to erosion and abrasion in situ

Stannous fluoride solutions have shown promising protective effect against erosion/abrasion, but the effect of SnF2 toothpastes is uncertain. The aim of the study was to test the inhibiting effect of two SnF2 toothpastes and a SnF2 solution against erosive/abrasive wear in a single-blind, randomised in situ study, using a white light interferometer. Sixteen human molars were each divided into four specimens, mounted on mouth appliances and worn by 8 volunteers for 9 days. Specimens were brushed with toothpaste twice each day for 30 s either with fluoride-free toothpaste or toothpastes including SnF2. Toothpaste was left on the surface for 90 additional seconds. Group 1, fluoride-free toothpaste; Group 2, toothpaste A (0.4% SnF2, Solidox); Group 3, toothpaste B (0.454 % SnF2, Oral-B(®)); Group 4, brushed with fluoride-free toothpaste (30 s) and treated for 2 min with a 0.4 % SnF2 solution (1,000 ppm F). To mimic gastric reflux/vomit, specimens were etched for 2 min twice a day (0.01 M HCl). Procedures were performed extra-orally. The mean enamel wear (in μm) for the control specimens was: -29.2 ± SD 10.5; for group 2 -14.5 SD ± 9.3; for group 3 -33.3 SD ± 7.4, and for group 4 +0.4 SD ± 1.3. The specimens treated with SnF2 solution and toothpaste A showed significantly lower enamel wear than the control group. Toothpaste B gave no significant reduction in enamel wear. The SnF2 solution fully protected the enamel surface against erosive and abrasive challenges. The SnF2 toothpaste A (Solidox) showed less, but significant protection of the enamel, while no statistically significant protection was demonstrated by SnF2 toothpaste B (Oral-B(®) Pro-Expert).

The Effect of Daily Fluoride Mouth Rinsing on Enamel Erosive/Abrasive Wear in situ

It is not known whether application of fluoride agents on enamel results in lasting resistance to erosive/abrasive wear. We investigated if one daily mouth rinse with sodium fluoride (NaF), stannous fluoride (SnF₂) or titanium tetrafluoride (TiF₄) solutions protected enamel against erosive/abrasive wear in situ (a paired, randomised and blind study). Sixteen molars were cut into 4 specimens, each with one amalgam filling (measurement reference surface). Two teeth (2 × 4 specimens) were mounted bilaterally (buccal aspects) on acrylic mandibular appliances and worn for 9 days by 8 volunteers. Every morning, the specimens were brushed manually with water (30 s) extra-orally. Then fluoride solutions (0.4% SnF₂ pH 2.5; 0.15% TiF₄ pH 2.1; 0.2% NaF pH 6.5, all 0.05 <smlcap>m</smlcap> F) were applied (2 min). Three of the specimens from each tooth got different treatment, and the fourth served as control. At midday, the specimens were etched for 2 min in 300 ml fresh 0.01 <smlcap>m</smlcap> hydrochloric acid and rinsed in tap water. This etch procedure was repeated in the afternoon. Topographic measurements were performed by a white-light interferometer. Mean surface loss (±SD) for 16 teeth after 9 days was: SnF₂ 1.8 ± 1.9 µm, TiF₄ 3.1 ± 4.8 µm, NaF 26.3 ± 4.7 µm, control 32.3 ± 4.4 µm. Daily rinse with SnF₂, TiF₄ and NaF resulted in 94, 90 and 18% reduction in enamel erosive/abrasive wear, respectively, compared with control (p < 0.05). The superior protective effect of daily rinse with either stannous or titanium tetrafluoride solutions on erosive/abrasive enamel wear is promising.

Erosion-inhibiting potential of a stannous chloride-containing fluoride solution under acid flow conditions in vitro

Objectives This study aimed to analyse the erosion-inhibiting potential of a single application of stannous chloride-containing fluoride solution on pellicle-covered enamel and dentine under constant acid flow conditions in vitro. Design Bovine enamel ( n = 60) and dentine ( n = 60) samples were exposed 1 h to the oral cavity of 4 healthy volunteers to allow for in situ pellicle formation. Pellicle-covered samples were randomly assigned to three groups (each n = 20 enamel and n = 20 dentine samples; 5 enamel and 5 dentine samples/volunteer) and treated once with a SnCl2/AmF/NaF (800 ppm Sn(II), 500 ppm F, pH 4.5) or a NaF solution (500 ppm F, pH 4.5) for 2 min or remained untreated (controls). Samples were eroded with hydrochloric acid (pH 2.6) in a small erosion chamber at 60 μl/min for 25 min. Calcium release into the acid was monitored in consecutive 30 s intervals for 5 min, then at 1 min intervals up to a total erosion time of 25 min using the Arsenazo III procedure. Data were statistically analysed by random-effects linear models ( p < 0.05). Results The stannous chloride-containing fluoride solution reduced calcium loss of enamel and dentine to up to 6 min and 3.5 min, respectively. Calcium loss (% of control) amounted from 24 ± 7 (30 s) up to 93 ± 14 (6 min) in enamel and from 38 ± 13 (30 s) to 87 ± 15 (3.5 min) in dentine. The sodium fluoride solution was unable to reduce enamel and dentine erosion at any time point. Conclusion A single application of a stannous chloride-containing fluoride solution reduced enamel and dentine erosion up to 6 min and 3.5 min of constant acid flow, respectively.

Effect of Stannous Fluoride and Dilute Hydrofluoric Acid on Early Enamel Erosion over Time in vivo

Recent experimental in vivo studies have shown that aqueous solutions of stannous fluoride (SnF₂) and hydrofluoric acid (HF) can reduce enamel solubility after 5 min. The aim of this study was to evaluate the longer-term protective effect of SnF₂ (0.78%, pH 2.9) and HF (0.2%, pH 2.0) (both ∼0.1 mol/l F) using the same experimental model. Labial surfaces of healthy anterior teeth (all four surfaces when possible, otherwise a pair of surfaces) in 103 subjects (n = 399 teeth) were exposed to citric acid (0.01 mol/l, pH 2.7). The acid was applied using a peristaltic pump (5 ml, 6 ml/min) and was collected in coded test tubes (etch I). The test solutions were then applied to the same surfaces of the teeth (1 min, 6 ml/min). After either 1, 7, 14 or 28 days, citric acid was again applied to the same surfaces and subsequently collected (etch II). Enamel solubility was examined by assessment of calcium concentration in etch I and etch II solutions using atom absorption spectroscopy. Median values were calculated for all time periods and statistical analysis was carried out using the Wilcoxon signed-ranks test. Results showed that HF reduced enamel solubility by 54 and 36% after 1 and 7 days, respectively. After 14 and 28 days, there was no longer any effect. SnF₂ showed no protective effect after the first day. Given these results, repeated application of HF and especially SnF₂ may be necessary to improve the protective effect of these fluorides, and this requires further testing.

The Effect of Some Metal Ions on Volatile Sulfur-Containing Compounds Originating from the Oral Cavity

Wåler SM. The effect of some metal ions on volatile sulfur-containing compounds originating from the oral cavity.Halitosis originates mainly from the oral cavity, and the volatile sulfur-containing compounds (VSC) are the major contributors of the unpleasant odor. Anaerobic G− bacteria use sulfur-containing amino acids in their production of VSC. Zinc has been shown to inhibit production of odiferous VSC, and the mechanism proposed has been that zinc, with its affinity for sulfur, oxidizes thiol groups and thereby inhibits the precursors of VSC. The aim of the study was to investigate whether, and to what extent, other metal ions with affinity for sulfur exert the same effect and whether a correlation exists between the sulfur affinity and VSC-inhibiting activity of these metals. VSC levels were measured on the ‘morning breath’ of 10 test subjects, using a portable sulfide monitor. The mouthrinses tested were aqueous solutions of zinc chloride, zinc citrate, stannous fluoride, cuprous gluconate, ferrous gluconate, and silver acetate, and they contained equimolar amounts of metals (1.47 mmol/l). The results showed that the ranking of Zn++ and Sn++ differed in the clinical test compared with sulfur affinity, and likewise with Ag+ and Fe++. It may therefore be concluded that there is no positive correlation between the inhibiting effect of metal ions on VSC and their affinity for sulfur.

Fluorine doped tin oxide films from spray pyrolysis of stannous fluoride solutions

Transparent conducting films of fluorine doped tin oxide were deposited using spray pyrolysis. The spray solution was tin (II) fluoride in methanol with or without addition of acid. Film thickness, growth rates and polycrystal grain size increased with deposition time, substrate temperature and amount of hydrochloric acid added to the deposition solution. The crystallite orientations in the films depended also on those variables as well as on solution concentration.

Stabilization and multidose use of exametazime for cerebral perfusion studies

The efficient use of exametazime for cerebral blood flow imaging is restricted by the short useful life of the reconstituted kit due to the instability of the primary complex. It is therefore recommended that 99Tcm-exametazime be used within half an hour after preparation allowing only a single patient dose to be prepared from one vial of exametazime. The shelf-life of 'cold' reconstituted exametazime has been extended by means of stannous enhancement. Freshly prepared stannous fluoride solution, 0.8 ml (5.4 micrograms SnF2), was mixed with 0.5 ml (42 micrograms) exametazime solution followed by the addition of up to 1500 MBq pertechnetate. The radiochemical purity of the chelate was 91% (S.D. 3.6%, n = 3). The rate of conversion of the primary complex (kc = 0.012 +/- 0.011 h-1) was considerably slower than the rate of degradation obtained using the recommended method of preparation (kc = 0.17 +/- 0.02 h-1). Radiochemical purity levels greater than 80% were maintained for up to 2.5 h after preparation and the level of free pertechnetate did not exceed 7%. There was only a slight deterioration of the cold reconstituted exametazime on storage of 0.3 +/- 0.1% per day. However, exametazime reconstituted up to 3 weeks previously produced more than 80% purity. The mean radiochemical purity obtained in 22 studies was 90% with a range of 81-98%. Clinical validation was performed in a blinded study of 38 patients using single photon emission computed tomography (SPECT). There was no significant difference between the images obtained using the tin enhancement method of preparation and the manufacturer's method (chi 2 = 3.62, P = 0.16).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of stannous fluoride and tetracycline on periodontal repair after delayed tooth replantation in dogs.

Previous studies have indicated that inflammatory resorption and ankylosis, which are frequent sequela after delayed tooth replantation, can be greatly reduced by treating the root surface with 1% solutions of stannous fluoride and tetracycline. However, the SnF2 conditioning leaves a long-standing inflammatory reaction in the periodontal ligament. To examine whether a more dilute SnF2 solution would reduce postoperative inflammation without jeopardizing any beneficial effects, anterior teeth in three young adult beagles were extracted and allowed to air-dry for 45 min. They were then immersed in 0.1% SnF2 for 5 min, rinsed in saline, immersed in 1% doxycycline HCl for 5 min, rinsed, and replanted. Control teeth were air-dried and replanted without further treatment. Block biopsies were harvested after 4 wk of healing and processed for histometric analysis. In experimental teeth, 85% of the root surface area showed normal healing, compared to 33% in control teeth. Conversely, resorption and ankylosis were more frequent in controls than in experimental teeth. A persisting inflammatory reaction either adjacent to or at a distance from the root surface was seen in limited areas in both experimental and control teeth. Compared to preceding studies, the findings indicate that reducing the strength of the SnF2 solution from 1% to 0.1% may result in less persistent inflammation, at the cost, however, of less complete prevention of inflammatory resorption and ankylosis.

Technical note: Fluoride pre-treatment effects on microleakage of a resin bonding agent

This pilot study reports the effect of fluoride pre-treatment of dentin and enamel on microleakage of a resin bonding agent. Pairs of circular class V cavities involving 50% enamel and 50% cementum were cut in 12 extracted third molars. Each tooth contained a control and a treatment cavity (matched-pair design). A stannous fluoride solution (0.717% SnF 2, Gel-Kam, Scherer Laboratories, Dallas, TX) was applied to the entire treatment preparation of each tooth. A dentin resin bonding system (Scotchbond 2 with Scotchprep, a dentin primer, 3M Dental Products Div., St. Paul, MN) was applied per manufacturer's instructions. Silux resin (3M) was placed over the resin bonding agent, light-cured, and finished. The teeth were subjected to 500 temperature cycles between 5 and 55°C. A silver nitrate staining technique was used for evaluation of microleakage. The mean leakage for the control was 2235 ± 1146 μm, and 2105 ± 1052 μm for the fluoride treatment sites. It is concluded, from this pilot study with small sample size, that pre-treatment with fluoride of dentin and enamel prior to the placement of a resin bonding agent produced no significant change in microleakage (Student's t test for paired samples, p = 0.6492).

Scanning electron microscope and electron microprobe study of reactions of stannous fluoride and stannous chloride with dental enamel.

Stannous fluoride but not stannous chloride has shown a caries inhibiting effect in animal studies. The effect of aqueous solutions of stannous fluoride and stannous chloride on dental enamel surfaces was investigated by scanning electron microscope and analytical electron microprobe. Some large globules and a continuous layer of small globules were observed after stannous fluoride treatment. The large globules were soluble in both water and alkali, whereas the small ones were only soluble in alkali. Both fluoride and tin were found to be present on the enamel surfaces by the electron microprobe after stannous fluoride treatment. The fluoride could not be detected after immersion in distilled water whereas alkali treatment removed the tin. The large fluoride-containing globules may consist of calcium fluoride as this substance is known to be slightly soluble in water and soluble in alkali. Stannous chloride treatment gave a layer of small tin-containing globules with properties similar to the layer formed on enamel treated with stannous fluoride. It is therefore suggested that the tin-containing layer is not associated with caries protection whereas calcium fluoride-like deposition on the enamel probably is a factor in the caries inhibition caused by stannous fluoride.

On the properties of fluoride solutions used for topical treatment and mouth rinse.

A number of solutions used for topical application and mouth rinsing were analyzed and calcium fluoride formation on human enamel at 20 °C determined. In most solutions free fluoride and hydrogen fluoride were the main ion species, whereas stannous hydroxide and stannous fluoride ion pairs were the dominating components of stannous fluoride solutions. The calcium fluoride formation on enamel was assessed by chemical analysis. It was found that an increase in fluoride activity and a decrease in pH increased the calcium fluoride formation to almost the same extent.

Effect on plaque formation and acidogenicity of stored aqueous solutions of stannous fluoride.

Abstract – Stored aqueous solutions of SnF2 showed a reduced effect on plaque acidogenicity after 24 weeks, this being paralleled by reduced concentrations of Sn2+ and lowered pH. The plaque inhibiting effect was, however, maintained unchanged, indicating a different mechanism for this activity. Stored solutions caused a yellow dental stain probably consisting of SnS2.

SEM Evaluation of Fluoride Pretreatment Effects on Acid-Etching of Caries-Like Enamel Lesions In Vitro

Acid-etching of enamel surfaces has been performed routinely to bond adhesive resin materials to sound dental enamel as a caries-preventive measure. The effect of fluoride pretreatment on acid-etching of enamel has been reported to produce inconsistent and unsatisfactory etching patterns. The failure to obtain an adequate etch has been postulated to be due to fluoride precipitation products deposited on the enamel surface. The purpose of this study was to evaluate the effects of fluoride pretreatment on acid-etching of carieslike lesions of human dental enamel.Caries-like lesions of enamel were created in vitro on human molar and premolar teeth. The teeth were divided into two fluoride treatment groups. The specimens were exposed for 4 minutes to either a 2% Sodium Fluoride (NaF) solution or a 10% Stannous Fluoride (SnF2) solution. The specimens were then washed in deionized-distilled water. Each tooth was sectioned into four test regions. This was carried out to compare the effects of various time exposures (0 to 2 minutes) and differing concentrations (10 to 60% w/w) of phosphoric acid (H3PO4) on etching of caries-like lesions. Standard preparation techniques for SEM were performed on the specimens.

Factors affecting the adhesion of polycar☐ylate cement to enamel and dentin

The adhesive bond strength of polycarboxylate cement with enamel and dentin and the factors affecting the adhesion of the cement to both structure were studied. A thick cement film reduced the tensile and shear bond strengths of the cement. Although surface roughness reduced the tensile bond strength of the cement, it significantly increased the shear bond strength. The application of the cement under pressure increased its shear bond strength. Surface treatment with 4% sodium fluoride solution for 5 minutes, 4% stannous fluoride solution for 2 minutes, and a 10% suspension of calcium hydroxide for 5 minutes significantly increased the shear bond strength of the cement with dentin.

The effect of topical fluorides, after acid etching of enamel, on the bond strength of directly bonded orthodontic brackets

This study tests the hypothesis that the beneficial effects of topical fluoride can be realized without reducing the bond strength of the resin adhesive. Twenty-eight groups of four teeth (third molars and premolars) were extracted from twenty-eight patients and stored in distilled water. Twin brackets on Ormesh pads were bonded to all teeth with Endur adhesive. One tooth from each group was bonded according to the manufacturer's instructions. These teeth, Subgroup I, served as controls. Subgroup II teeth were etched for 4 minutes with 50% phosphoric acid containing 2 percent sodium fluoride. Subgroup III teeth received a 3-minute application of a basic phosphate fluoride solution (10 −2M Na 3PO 4, 10 3 ppm F) after 1 minute of etching with 50 percent phosphoric acid. Subgroup IV teeth received a 4-minute application of 8 percent stannous fluoride solution after 1 minute of etching with 50 percent phosphoric acid. Each tooth was mounted in a block of improved dental stone; guide wires were used to reproduce bracket orientation. The M.T.S. materials-testing apparatus was used to generate a torsional moment on the bracket at a rate of 1 degree per second. Fluoride uptake by enamel has been shown to be greater in an acid medium or after acid etching. The application of directly bonded orthodontic brackets and pit-and-fissure sealants requires acid etching of the enamel surface. This study supports the use of topical fluoride after acid etching, a procedure that achieves the benefits of increased fluoride uptake without changing the bond strength of the resin adhesive.

Uptake and retention of tin by S. mutans.

The uptake of tin by S. mutans from stannous fluoride or stannous chloride solutions was determined by atomic absorption spectroscopy. The uptake occurred rapidly, and the microorganism was shown to have a greater capacity and higher affinity to uptake of tin than of other metal ions tested. In 10 mM solutions, bound tin amounted to 17.5 per cent of the cellular dry mass. The tin uptake was independent of cell metabolism. The cell bound tin could not be washed out with water or saline, but 84 per cent was removed by ethylenediaminetetraacetic acid solutions. When pH was lowered by low 2, increasing loss of bound tin occurred. It is suggested that the binding occurs to polyanionic structural polymers in the cell wall and the cell capsule.

Effects of stannous fluoride and amine fluorides on caries incidence and enamel solubility in adults

Three groups of men aged 19 to 22 years were examined. Group A was regarded as control, group B was treated topically with stannous fluoride solution every 6 months, group C received a gel for brushing once a week. All the subjects were re-examined after 6, 12, 18, 24, 30 and 36 months and DMFS scores were analysed. In the end of the trial 639 teeth from 213 participants were evaluated in vivo for enamel solubility rates by the CRT test. After three years of treatment both examinations disclosed that the gel was more effective in dental caries inhibition and reduction of the enamel solubility in acids, than stannous fluoride solution.