In vitro effect of topical fluorides on sealant materials.

The purpose of this study was to determine by visual inspection and by scanning electron microscopy (SEM) whether commercially available, topical, acidulated phosphate fluoride (APF) and neutral sodium fluoride (NaF) agents cause surface roughening of five sealant materials: two unfilled resins, two filled resins, and one glass-ionomer material. In addition, the effect of treatment with 1.23% APF and sonification on weight of an unfilled and a filled sealant was compared to treatment with controls. Unfilled sealants exhibited no surface changes visually or on micrographs following any treatment. Filled sealants and the glass-ionomer sealant exhibited visually apparent changes depending on the treatment. SEM inspection of filled sealants with visually apparent changes showed loss of filler particles whereas the glass-ionomer sealant exhibited apparent destruction both of the matrix and the filler particle. No significant differences in weight were found between sonicated and unsonicated specimens. However, significant loss of weight was found with filled sealant specimens, but not unfilled sealant specimens, treated with 1.23% APF gel as compared with the specimens treated with water. The results of this in vitro study indicate that preventive therapies that combine use of topical fluorides and sealants may cause deterioration of filled sealants and glass-ionomer sealant material, but not unfilled sealants.     

Further abrasion resistance and bond strength studies of fissure sealants

As part of a laboratory evaluation, measurements of abrasion loss and tensile enamel--sealant bond strengths have been made on three visible light cured sealants (two filled, one unfilled), two chemically cured sealants (one filled and one unfilled) and an experimental sealant with alumina filler particles. A UV-cured filled sealant was used as a control. The unfilled sealants had abrasion loss approximately twice that of the filled commercial sealants. The experimental sealant, with filler content above 50%, had an abrasion loss approximately half that of the filled commercial sealants. The chemical cured sealants had bond strengths lower than the UV-cured control, while the bond strengths of the two visible light-cured filled sealants and the experimental sealant were not statistically different from either the unfilled visible light-cured sealant or from the UV-cured filled sealant.     

Compressive strength, surface roughness, fluoride release and recharge of four new fluoride-releasing fissure sealants

The aim of this study was to investigate the compressive strength and surface roughness of two glass ionomer cements and two resin-based fissure sealants before and after fluoride release and recharge. Twenty-one specimens were prepared and divided into three groups for each material. First group was loaded in compression until failure. Fluoride released was measured from the remaining specimens, and then the second group of seven specimens was loaded at 28th day. The remaining seven specimens were exposed to 0.05% NaF solution and 1.23% APF gel. Fluoride amount was measured, and the last group was loaded at 70th day. Surface roughness measurement of five more disk-shaped specimens from each material was also carried out. After exposure to APF gel, all materials were recharged. At the end of experimental period, it was found that surface roughness increased, whereas compressive strength decreased, over time. In conclusion, fluoride-releasing fissure sealants could act as show, rechargeable fluoride release systems. However, if a fissure sealant exhibited high fluoride release, it had inferior mechanical properties.     

Clinical evaluation of Helioseal F fissure sealant

Unfilled resins are commonly in use as sealant material. In addition, there are filled sealants available. Helioseal F is a newly developed filled material with fluoride release. In this clinical trial, Helioseal F has been evaluated in one lower molar versus Delton opaque as an unfilled control in lower molars. After 12 months there were no significant differences in retention, porosities, and the number of clinically unacceptable margins between the materials. The complete retention was 30 out of 31 examined teeth for Delton and 28 out of 31 for Helioseal F. After 1 year of clinical testing, these results indicate that a sealant containing fluoride-releasing particles did not show a significant difference in retention rate compared to an unfilled conventional sealant. However, long-term results concerning marginal adaptation should be evaluated. Received: 20 June 1997 / Accepted: 3 November 1997     

An in vitro evaluation of the effect of sealant characteristics on laser fluorescence for caries detection

PURPOSE: The purposes of this study were to: (1) evaluate the ability of a laser fluorescence (LF) unit to detect simulated caries under pit and fissure sealants; (2) determine the effect of an opacifying agent in sealants on LF values; and (3) determine interexaminer reproducibility values of the unit in a highly controlled, laboratory setting. Sealant characteristics specifically considered were: (1) filler content; (2) opacity; and (3) intrinsic fluorescence. METHODS: Three sealants were used in this study: 2 unfilled and 1 filled. To evaluate the effect of an opacifying agent, titanium dioxide powder was added to both filled and unfilled sealants. 0.5-mm thick sealant discs were prepared for all samples. The sealant discs were individually placed on top of 3 wells filled with varying amounts of protoporphyrin IX, a fluorescent material that mimicked dental caries. A total of 270 readings were made through the different sealant discs to evaluate signal attenuation of the laser fluorescence unit. RESULTS: Clear sealants, without an added opacifying agent, attenuated LF readings. At baseline protoporphyrin IX levels yielding DIAGNOdent readouts of 20 and 60, there was a significant difference in the LF readings between the baseline protoporphyrin (uncovered) and with sealant disc covered in all 3 sealant types (P<.001). Furthermore, the filled sealant attenuated LF signals significantly more than the unfilled sealant (P<.001). Sealants with titanium dioxide added had variable levels of intrinsic fluorescence. Titanium dioxide added to the sealants also had a profound effect on fluorescence transmission of the underlying simulated caries. As the concentration of titanium dioxide approached 0.5%, the fluorescence signal was almost fully attenuated. CONCLUSION: Clinical detection of caries under dental sealants with the use of laser fluorescence units is unreliable and not recommended due to a high likelihood of inaccurate readings caused by: (1) intrinsic fluorescence of sealant material; and (2) attenuation of fluorescence signals by the sealant.     

Change in occlusal height resulting from placement of pit and fissure sealants.

This in-vitro study was done to identify the amount of change in occlusal height resulting from standard sealant application technique and to determine whether this change was uniform for both a filled and an unfilled sealant material. Twelve dental hygienists experienced in sealant technique each applied 10 filled sealants and 10 unfilled sealants in standardized artificial teeth mounted in a dentiform and mannikin setup in a dental unit. The teeth were measured with a digital caliper before and after sealant placement. Measurements were from a predetermined point at the apical area of the teeth to the depth of the central fossa. For the sample of 240 teeth, the mean sealant thickness was 0.43 +/- 0.20 mm. When the data for the filled and unfilled sealants were examined separately, the means were 0.47 +/- 0.23 mm and 0.38 +/- 0.16 mm, respectively. A t-test indicated a significant difference at p < 0.001. Analysis of variance revealed significant interoperator differences in sealant thickness (p < 0.01).     

Effects of professionally applied topical fluorides on surface hardness of composite-based restoratives

This study investigated the effects of professionally applied topical fluorides on the surface hardness of a composite (Spectrum TPH), a compomer (DyractAP) and a giomer (Reactmer). Thirty specimens of each material were fabricated and stored in distilled water at 37 degrees C for one week. These specimens were then randomly divided into five groups of six and treated for 36 hours at 37 degrees C with one of the following: distilled water (control), 1.23% acidulated phosphate fluoride (APF) foam, 0.9% neutral foam, 1.23% APF gel and 0.4% stannous fluoride gel. The treated specimens were subsequently subjected to microhardness testing (load = 500 gf; dwell time = 15 seconds). Results were analyzed using ANOVA/Scheffe's test (p<0.05). The effects of topical fluoride application on surface hardness was material dependent. For all materials, treatment with APF gel and foam significantly reduced surface hardness when compared to the control. KHN values after exposure to APF gel were consistently the lowest and ranged from 4.53 to 15.97. Control KHN values were higher, ranging from 32.88 to 47.47. The surface hardness of the compomer was also significantly reduced after exposure to neutral foam. Therefore, the use of professionally applied topical fluorides, especially APF gel and foam, may be detrimental to the long-term durability of composite-based restoratives.     

Laboratory studies of visible-light cured fissure sealants: setting times and depth of polymerization

Measurements were made, using an acoustic transmission method, of the setting times of three visible-light curing sealants (two filled, one unfilled). Five commercially available visible-light polymerizing sources were tested with each material. Only three of the light sources gave setting times not significantly different from the manufacturers' recommended times for all three materials tested. The variation in microhardness with depth of sealant was measured to study the depth of polymerization of the sealants, all of which were adequate. The filled sealants had microhardness values greater than the unfilled sealant, at all depths studied.     

Occlusal discrepancies after sealant therapy.

To date there has been no evidence concerning the need for adjusting the occlusion after sealant placement. Thus, this study investigated the occlusal effects of filled and unfilled sealants. For each of 18 subjects a sealant was applied and the occlusion monitored for 1 week. Each participant received a filled and an unfilled sealant for the specified period. With the filled sealant, nearly all subjects experienced a perceptable occlusal change and most were unable to abrade the interferences to a comfort level. These results indicate that the occlusion should be routinely verified and, if necessary, adjusted immediately after placement of a filled sealant.     

Uptake of fluoride into enamel and its effect on acid resistance by application of fluoride-releasing sealant--Part 1. Comparison with acid phosphate fluoride

The newly developed fluoride-releasing sealant (F + sealant) used in this experiment is expected to have the combined cariostatic effects of a sealant and fluoride. The purpose of this study was to investigate F + sealant's effects on the enamel in regard to the uptake of fluoride and resistance to acid. F + sealant's effect was compared to that of acid phosphate fluoride (APF) which has effect as topical fluoride applicant. Bovine teeth applied with F + sealant or APF were immersed for 4 weeks in a pH 7.0 phosphate buffer at 37 degrees C. After 4 weeks of immersion, each tooth was biopsied with pH 1.0 sodium acetate-hydrochloric acid buffer. The fluoride and calcium in the biopsy samples were analyzed by means of fluoride ion electrode and atomic absorption spectroscopy, respectively. The following results were obtained: (1) The fluoride in the enamel was significantly increased by the incorporation of fluoride from the F + sealant. Almost all fluoride in the surface enamel was found to be fluorapatite by the method of alkaline extraction. (2) The amount of fluoride increased by APF application was about 50% of that of F + sealant application. (3) The calcium released from the enamel treated with F + sealant or APF decreased by 13% and 9%, respectively, compared to that without treatment.     

Effect of 1.23 percent APF gel on fluoride-releasing restorative materials

This study evaluated the effect of a 1.23 percent APF gel on the surface morphological characteristics and surface roughness of one high-viscosity (Fuji IX GP), three polyacid-modified resin-based composites (Dyract AP, F2000 and Compoglass F) (PMRC), and two resin-modified glass-ionomer cements (Vitremer and Fuji II LC). A microfilled nonfluoridated resin-based composite (Silux Plus) was used as a control. All materials were handled according to the manufacturers' instructions. The fluoride gel used in the study was a 1.23 percent acidulated phosphate fluoride gel (APF) (Nupro APF). The specimens were repeatedly exposed to the APF gel with cotton applicators for a period that simulated the equivalent of 4 yrs (1 min/6 mo) under prophylactic fluoride treatment. Average surface roughness (Ra) of the control and treated specimens was measured. Three separate Ra measurements along the direction of rotation of the finishing and perpendicular to the finishing direction and edge of the mold were made for each specimen surface. In each group, specimens with Ra closest to the mean were removed from the molds, sputter-coated with gold and examined using a scanning electron microscope. The results showed that all tested materials, except Vitremer, displayed increased surface roughness values following APF treatment. However, this was not statistically significant for Compoglass F, Vitremer and Fuji II LC. Among PMRC materials, F2000 displayed the highest Ra average value, although the differences between F2000 and Dyract AP and of Compoglass F and Dyract AP was not statistically significant. Comparisons of the Ra values between Silux Plus and the other test materials revealed statistically significant differences except for Dyract AP and Compoglass F. No statistically significant difference was found between the Ra values of Vitremer and Fuji II LC following APF treatment. Among all groups, Fuji IX GP displayed the highest surface roughness.     

Fissure sealant retention: a comparison of three sealant types under field conditions

Two two-year double-blind clinical trials were undertaken involving the newly-erupted first permanent molars of 133 children aged 5-6 years at the outset. In one study of 76 subjects, half the teeth were sealed with the filled sealants Prismashield or Estiseal. In the other study of 58 children, half were again sealed with Prismashield, and the others with the unfilled Concise white sealant, by a community dental service hygienist, as part of her routine dental duties. Subjects were examined under blind conditions at 6 monthly intervals and, by 24 months in the first study, 71 per cent of Prismashield sites were intact and caries-free, compared with only 53 per cent of Estiseal-treated tooth units (P less than 0.001). In the second study comparing Prismashield and Concise, by two years, 81 per cent of Prismashield resins were complete, compared with 88 per cent of the nonfilled Concise material. There were, however, no differences noted with respect to buccal and palatal site retention for either study. It can be concluded that Estiseal is a poorer material than Prismashield, certainly in relation to its bulk retention properties. Nonetheless it is possible that, along with other tooth-coloured/transparent resins, small fragments may not be as readily detectable as is the case with the unfilled Concise white sealant. However, as the abrasion resistance of unfilled materials is poorer than that of filled resins, the similar buccal/palatal site retention for Prismashield and Concise was also unexpected. Nevertheless this study illustrates again the value of sealant placement in the erupting first permanent molars of 5-6-year-old children, at a time when these teeth are most susceptible to carious attack.     

含氟涂料对光固化复合树脂腐蚀作用的探讨

目的评估不同含氟涂料对5种光固化复合树脂表面的腐蚀作用。方法选取5种光固化复合树脂[微填料复合树脂（Ar）、纳米混合复合树脂（Gr）、纳米复合树脂（Su）、复合体（GI）和聚硅氧烷复合树脂（Ad）]制成φP6mm×3mm试样各25个。表面磨平抛光后分别用4种含氟涂料（F、G、D、B）于37℃100％相对湿度下处理30min，单次蒸馏水作为对照。扫描电镜观察试样表面的形态改变，并行激光共聚焦显微镜分析。结果含氟涂料对4种复合树脂均产生腐蚀作用（Su除外），腐蚀程度由强到弱的顺序为F、G、D、B。试样腐蚀形式均为表面粗糙。含氟涂料F和G作用于Ad后其改变最明显。经激光共聚焦显微镜分析，含氟涂料处理后复合树脂表面参数数值均增大。Su表面参数改变不明显。结论含氟涂料对复合树脂有腐蚀作用，腐蚀程度与复合树脂的类型、含氟涂料的种类相关。     

Fluoride-releasing capacity and cariostatic effect provided by sealants

This study evaluated the effect of sealants on enamel demineralization, focusing on physical protection of the sealed enamel and fluoride protection of the adjacent unsealed enamel. Occlusal fissures with areas measuring 12 mm2 were delimited in 48 extracted molars, randomly divided into 4 groups (n =12): 1) no sealing; 2) sealing with a resin-modified glass-ionomer (Vitremer, 3M ESPE); 3) sealing with a fluoride-releasing composite sealant (Clinpro Sealant, 3M ESPE); and 4) sealing with a non-fluoridated composite sealant (Concise, 3M ESPE). A 4-mm2 window was outlined on the buccal enamel for analysis of fluoride uptake. Following treatment, groups 2, 3 and 4 were subjected to 5-days of pH-cycling, while group 1 was kept in a moist environment at 37 degrees C. Fluoride uptake was assessed by dental biopsy, and the amount of fluoride released to the cycling solutions was determined by ion analysis. Enamel demineralization around the sealants was evaluated by cross-sectional micro-hardness analysis. Group 2 showed higher levels of fluoride release (P < 0.01) and uptake by enamel (P < 0.05), and lower levels of demineralization (P < 0.05) than groups 3 and 4. Group 3 exhibited reduced demineralization on unsealed enamel and provided fluoride uptake in a distant enamel area, while group 4 did not.     

Fluoride release/uptake of conventional and resin-modified glass ionomers, and compomers

OBJECTIVES: To assess the levels of fluoride ions released from a range of freshly-prepared aesthetic restorative materials, and then the effects of a topical acidulated phosphate fluoride (APF) gel. METHODS: Five specimens each of four conventional GICs, two resin-modified GICs, two compomers, and a resin composite (control) were assessed for their fluoride ion release over 6 weeks, before being exposed to 1.23% APF gel for 4 min and then measuring their fluoride ion levels for another 6 weeks. RESULTS: Following an initial brief, variable burst of fluoride ion release, the rates then fell quickly for most materials and, although high rates of fluoride ion release were measured immediately following the application of APF gel, these rates also fell quickly for most materials. After 12 weeks, the mean fluoride ion levels were much lower than immediately before gel application. The APF gel treatment caused surface damage to all materials, especially to the conventional GICs. CONCLUSION: The results of this study suggested that much of the increased fluoride ion release found following topical exposure of the fluoridated restorative materials to APF gel was caused by surface effects rather than by chemical recharging.     

The bonding of a polymeric fissure sealant to topical fluoride-treated teeth

The tensile bond strength of a polymeric fissure sealant to enamel treated with a variety of topical fluorides was determined. Application of acidulated phosphate fluoride solutions (APF) prior to and after acid etching reduces the tensile bond strength of Nuva Seal from 36·6±9·0 kg/cm² to 4·9±3·3 kg/cm² and 23·8±6·3 kg/cm³ respectively. The treatment of the etched enamel with freshly prepared 8% stannous fluoride solution prior to Nuva Seal® application significantly increases the tensile bond strength to 55·7±17·1 kg/cm². It is recommended that clinical procedures such as the application of fissure sealants, acid etch composite restorations and the direct attachment of orthodontic brackets, all of which involve etching of the enamel, should not be preceeded by the topical application of APF solutions.     

窝沟封闭前局部用氟对离体牙窝沟侧壁氟含量的影响

目的研究窝沟封闭前局部使用酸性磷酸氟（APF）对窝沟侧壁氟含量的影响。 方法收集第三恒磨牙共9对18颗,随机一侧为对照组、对侧同名牙为酸性磷酸氟处理组。（1）对照组：酸蚀60 s,窝沟封闭;（2）处理组：酸性磷酸氟溶液处理4 min后,酸蚀60 s,窝沟封闭。用电子探针显微分析（EPMA）对窝沟侧壁进行点检测,所得数据进行配对t检验统计学分析。 结果酸性磷酸氟处理组的窝沟侧壁氟含量为（0.50 ± 0.09）%,明显高于对照组含量（0.24 ± 0.12）%,差异有统计学意义（t=-4.670,P= 0.002）。 结论窝沟封闭前局部使用酸性磷酸氟溶液,可提高窝沟侧壁氟含量。     

Effects of DCPD/APF application and prolonged exposure to fluoride on caries-like lesion formation in vitro

The ability of a topical fluoride regimen consisting of a 4-min application of a saturated dicalcium phosphate dihydrate (DCPD) solution followed by a 4-min application of 1.23% acidulated phosphate fluoride (APF) to inhibit caries-like lesion formation in sound enamel was compared to that of a 4-min application of APF. Following the applications, specimens were washed for 24 h in an inorganic wash solution or for 28 days in a wash solution containing 1 ppm fluoride. The mean overall lesion depth for specimens treated with APF and washed for 28 days was significantly greater than that for the group treated with DCPD/APF and washed for 28 days, and for the group treated with APF and washed for 24 h (p less than 0.05). For those specimens washed for 24 h, the mean width of the surface zone was greater (p less than 0.05) for the DCPD/APF group compared to the APF group.     

Active management of incipient caries and choice of materials

Evidence of the effects of various sealant and fluoride materials in stabilizing or reversing incipient caries lesions has been reported. However, a knowledge gap still exists as to what material yields the best results. Thus, the objective of this study was to find the most effective material by comparing the effects of a resin-based sealant (sealant), a fluoride-containing sealant (F-sealant), a fluoride varnish (F-varnish), and a glass-ionomer cement (GIC) on de-remineralization of incipient artificial caries and adjacent intact enamel on proximal surfaces of posterior teeth. The 4 materials were applied to lesions created on proximal surfaces. Areas of intact enamel 0.5 mm adjacent to the materials were also studied. The specimens were thermo- and pH-cycled. Cross-sections of the two areas were analyzed under polarized light microscope and quantified with Image-Pro plus. The most effective material in reducing the carious areas was GIC, followed by F-varnish, F-sealant, and sealants. GIC followed by F-varnish was most efficient in inhibiting new caries lesions 0.5 mm adjacent to the materials.     

Effects of DCPD/APF application and prolonged exposure to fluoride on caries-like lesion formation in vitro

The ability of a topical fluoride regimen consisting of a 4-min application of a saturated dicalcium phosphate dihydrate (DCPD) solution followed by a 4-min application of 1.23% acidulated phosphate fluoride (APF) to inhibit caries-like lesion formation in sound enamel was compared to that of a 4-min application of APF. Following the applications, specimens were washed for 24 h in an in organic wash solution or for 28 days in a wash solution containing 1 ppm fluoride. The mean overall lesion depth for specimens treated with APF and washed for 28 days was significantly greater than that for the group treated with DCPD/APF and washed for 28 days, and for the group treated with APF and washed for 24 h (p<0.05). For those specimens washed for 24 h, the mean width of the surface zone was greater (p<0.05) for the DCPD/APF group compared to the APF group.