Fluoride-releasing restorative materials and secondary caries

Effect of fluoride recharge on the microleakage of fluoride-releasing restorative materials: An ex vivo confocal laser scanning microscopy study

Context:

Success or failure of a restoration depends on its ability to bond to the tooth structure, to reduce microleakage, and to inhibit secondary caries. Fluoride-releasing materials have the inherent potential to release fluoride and are also capable of recharging themselves with topical agents.

Aim:

The aim of this study was to compare and evaluate the effect of fluoride recharge on microleakage of different restorative materials.

Materials and Methods:

Eighty extracted teeth were collected and split mesiodistally into 160 specimens. Class V cavities were prepared on buccal and lingual surfaces. Specimens were divided into four groups of 40 each based on the restorative material. Group I: Glass ionomer; Group II: Resin composite; Group III: Giomer; and Group IV: Alkasite. The restored teeth were stored in artificial saliva. Each group was divided into four subgroups for fluoride recharge and subsequent confocal laser scanning microscopy (CLSM) examination: (A) no fluoride recharge and CLSM examination after 24 h, (B) no fluoride recharge and CLSM examination after 3 weeks, (C) fluoride recharge once at third week followed by CLSM examination at 6 weeks, and (D) fluoride recharge twice at third week and sixth week followed by CLSM examination at 9 weeks.

Statistical Analysis:

Kruskal−Wallis and Mann−Whitney U tests were performed to analyze the obtained data.

Results:

A significant difference in microleakage was noted among resin composite and other groups except Cention-N, whereas no significant difference was noted pre- and post-fluoride recharge.

Conclusion:

Increased microleakage was noted post-fluoride recharge, although statistically not significant.

In Vitro Studies concerning Selected Properties of a Composite Material Blended with Nanofluoroapatite Crystals

The aim of the paper was to determine the potential for fluorine release from an original composite material blended with nanofluoroapatite (FAp). The level of fluoride ion emission into deionized water and saline was studied over a period of 12 weeks. Values were recorded after 1, 3, 24, 48, 72, and 96 h and then weekly for a period of 12 weeks. There were statistically significant differences in the periods of fluoride ion release from 5%FAp and 2%FAp materials into saline solution as well as into deionized water. The highest fluorine release from 5%FAp + polymer was observed in the 10th and 11th week of incubation (for saline solution) and in the 9th, 10th, and 11th week (for deionized water). The highest fluorine release from 2%FAp + polymer was observed in the 9th, 11th, and 12th week of incubation for both environments. Total fluoride ion release from 5%FAp + polymer and mean fluoride release levels were similar in 5%FAp and 2%FAp in both environments. Both tested materials (5%FAp and 2%FAp) show the ability to release fluoride ions over a long time in the experimental environment.

Comparative evaluation of Rheological characteristics of Giomers and other Nano-flowable resin composites in vitro

Objective

The purpose of this research was to determine the viscoelastic properties of a group of commercially available nano-flowable resin composites; and to explore the relation between these properties and the materials’ composition (with/without fluoride), filler size description (nano-filled, nanohybrid and submicron-filled) and filler loading (by volume).

Methods

Rheological measurements were performed using a rheometer. A Dynamic frequency sweep test was conducted to evaluate the complex viscosity, storage and loss moduli, loss tangent, and complex shear modulus at an angular frequency (ω) of 0.1–100 rad/s. Comparative evaluations of the nano flowable resin composites on rheological properties was performed, and statistically analyzed using one-way ANOVA.

Results

The results indicated that all the tested materials exhibited shear-thinning flow behaviour. As the shear rate increased, the complex viscosity of the nano-flowable composites decreased. The nanohybrid filled flowable resin composites exhibited the highest complex viscosity, while the nano-filled flowable resin composites exhibited the lowest value. The submicron-filled materials exhibited the lowest complex shear moduli and loss tangent values. Conclusions: The findings from the current study provided comprehensive evaluation of the rheological properties of different nano-flowable composites. The observed differences in rheological properties among the tested materials were independent of their fluoride content or filler size. Furthermore, no relationship was found between the complex viscosity of the tested nano-flowable resin composites and their filler volume.

Glass Ionomer Cements for the Restoration of Non-Carious Cervical Lesions in the Geriatric Patient

Background: The restoration of non-carious cervical lesions in geriatric patients is a demanding process. Glass ionomer cements can be promising materials for the management of these lesions in older adults. The aim of this literature review is to present the benefits of glass ionomers and how they can be used for the restoration of non-carious cervical lesions of older adults depending on the geriatric patient’s profile. Data sources: All available in vitro and in vivo studies from Google Scholar, PubMed and Scopus search engines corresponding to glass ionomer cements, geriatric dentistry, elderly patients, and non-carious lesions as key words were reviewed. Data synthesis: The advantages of glass ionomer cements, such as good retention and fluoride release, make them suitable for the restoration of non-carious cervical lesions. However, several factors related to the geriatric patient’s profile determine the most suitable material type. Conclusion: In general, the resin modified glass ionomer cements (RMGICs) appear to be preferred, but under certain circumstances the use of the conventional product is more appropriate, despite its poorer mechanical features. Further studies are required for more reliable data analysis and clinical interpretation of the relevant results.

Evaluation of Ion Release from Four Dental Sealants

The purpose of this study was to determine the ion release from four commercially available pit-and-fissure sealants [3M Clinpro, 3M Concise™, BeautiSealant (BS), and GI FX-II)]. With each brand, 18 specimens were prepared. Their fluoride release in de-ionized water was measured by fluoride electrode, while the release of silicate (Si), aluminum (Al), sodium (Na), calcium (Ca), strontium (Sr), and phosphorus (P) was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) on days 1, 3, 7, 14, 21, and 28. The result showed that fluoride was not released from 3M Concise™. GI FX-II displayed the largest fluoride release, which, however, dropped rapidly on day 3. 3M Clinpro exhibited less fluoride release than GI FX-II and BS did. At any time during the 28-day experimental period, GI FX-II released more Na than the other sealants (P<0.001). BS ranked the second in Na release, and a small amount of Na ions was released from the 3M Clinpro and 3M Concise™ samples. Al ions were only detected from BS and GI FX-II, but not from the 3M Clinpro and 3M Concise™. Additionally GI FX-II had the largest Si release among the four brands at any time during the experimental period (P<0.001). Ca ions were detected from 3M Clinpro and 3M Concise™, but not from GI FX-II. BS released more Sr than the other sealants at any time during the experimental period (P<0.001). All the samples released similar amounts of P continuously during these 28 days. In conclusion, based on the type and the amount of ion release, BS is the best pit-and-fissure sealant among the four brands.

Remineralization of Natural Human Carious Dentin Lesions with an Experimental Whisker-Reinforced Atraumatic Restorative Treatment Composite

PURPOSE

To evaluate the remineralization of natural human dentin caries with an experimental whisker-reinforced Atraumatic Restorative Treatment (ART) composite.

MATERIALS AND METHODS

Teeth with moderate active dentin caries were prepared with caries-disclosing dye and hand instruments, restored with ART or resin-modified glass ionomer cement (RM-GIC), and then wet sliced into 120-µm sections with 15 sections in each group. After taking transverse microradiographs and implementing digital image analysis to determine the "mineral-loss-before," each section was incubated in artificial saliva solution (pH = 7.0) for 4 weeks and 8 weeks with 1 hour each workday in demineralization solution (pH = 4.3). Transverse microradiographs of each section were retaken, and the "mineral-loss-after" was determined. The remineralization was calculated from [1-("mineral-loss-after"/"mineral-loss-before")] × 100%. Results were statistically analyzed with a repeated-measures ANOVA with one within-subject factor (time: 4 and 8 weeks) and one between-subject factor (material: ART and RM-GIC) (α = 0.05).

RESULTS

The statistical analysis indicated that ART composite resulted in significantly higher remineralization than the RM-GIC (p ≤ 0.05). For the remineralization of each material, there was a statistical difference between 4 weeks and 8 weeks (p ≤ 0.05).

CONCLUSIONS

This experimental ART composite remineralized natural human dentin caries better than the RM-GIC.

A Comparative Evaluation of the Amount of Fluoride Release and Re-Release after Recharging from Aesthetic Restorative Materials: An in vitro Study

AIM

To measure the amount of fluoride released and re released after recharging from various restorative materials: Conventional Glass Ionomer Cement (Fuji II), Light Cure Resin Modified GIC (Fuji II LC), Giomer (Beautifil II), Compomer (Dyract).

MATERIALS AND METHODS

Fifteen cylindrical specimens were prepared from each material. The specimens were immersed in 20 ml of deionized water. The amount of released fluoride was measured during the 1(st) day, 7(th) day and on the day15 by using specific fluoride electrode and an ion-analyser. After 15 days each material was divided into three Sub Groups of five samples each. Sub Group A served as control, Sub Group B was exposed to 2% NaF solution, Sub Group C to 1000ppm F toothpaste. The amount of fluoride re-released was measured during the 1(st) day, 7(th) day and on the day15 by using specific fluoride electrode and an ion-analyser. The results were statistically analysed using analysis of variance (one-way ANOVA) and Tukey Kramer multiple comparison tests (p≤0.05).

RESULTS

Independent of the observation time period of the study the Conventional GIC released the highest amount of fluoride followed by RMGIC, Giomer and Compomer. The initial burst effect was seen with GIC'S but not with Giomer and Compomer. After topical fluoride application fluoride re release was highest in Sub Group B and GIC had a greater recharging ability followed by RMGIC, Giomer and Compomer. The fluoride re release was greatest on 1(st) day followed by rapid return to near exposure levels.

CONCLUSION

From the study it was concluded that, the initial Fluoride release was highest from Conventional GIC followed by Resin Modified GIC, Giomer and Compomer. The Fluoride re release was high when recharging with professional regime (2% NaF) as compared to home regime (Toothpaste). Conventional GIC had a greater recharging ability followed by Resin Modified GIC, Giomer and Compomer.

Influence of the curing mode on fluoride ion release of self-adhesive resin luting cements in water or during pH-cycling regimen

This study evaluated the effects of curing modes and storage conditions on fluoride release of resin cements. In phase 1, the cumulative fluoride release rate from samples of the resin cements (Panavia F 2.0, RelyX Unicem, MaxCem, and BisCem) was quantified after 15 days storage in water (n=4). In phase 2, the fluoride release profiles from the same materials were analyzed during pH cycling (n=4). In this second phase, fluoride was measured at specific times (one, two, three, five, eight, and 15 days). Disk-shaped specimens were prepared (10 mm × 0.5 mm), and the materials were either light activated or allowed to autopolymerize. For both phases, the fluoride release was measured using a fluoride ion-specific electrode. The fluoride release in water was not affected by the curing mode of RelyX Unicem and Maxcem resin cements. Panavia F. 2.0 and BisCem resin cements, either light cured or autopolymerized modes, released higher amounts of fluoride in water than the other self-adhesive cements. In phase 2, the concentration of fluoride released decreased from the first day of pH cycling until the 15th day for all resin cements, for both curing modes, regardless of the storage solution used (demineralizing/remineralizing). The fluoride release rate during pH cycling by Panavia F 2.0 and MaxCem was not affected by the curing mode. The effect of the curing mode on fluoride ion release in water or during pH cycling was product dependent.

In Vitro Secondary Caries Inhibition by Adhesive Systems in Enamel Around Composite Restorations

The ability of the adhesive system to inhibit secondary caries was similar among the materials tested, according to the enamel mineral content around restorations.

Linear regression modeling to compare fluoride release profiles of various restorative materials

OBJECTIVES

The aim of this study was to compare the released fluoride profiles of various restorative materials by using linear regression analysis.

METHODS

Specimens were prepared using a cylindrical Teflon mold with a height of 2 mm and a radius of 8 mm. After being prepared, specimens were immediately placed into artificial saliva which was replaced at various times during 6 weeks. These released intrinsic fluoride amounts were measured by using an ion selective electrode. Then, data obtained cumulatively were statistically analyzed, and the released profiles were compared.

RESULTS

It was observed that the materials released fluoride at different levels of concentration and the largest fluoride release was obtained from the conventional glass ionomer cement. This was followed by resin modified glass ionomer cement, polyacid modified composite resin, and fluoride releasing composite resin, respectively. Although the released fluoride amounts of the materials were different, their release profiles were found to be similar in that the release was initially fast and then it became steady as time passed.

SIGNIFICANCE

The statistical modeling of the release profiles helps to compare the fluoride release behavior of materials and also to predict fluoride release amounts for the future. In literature, for these purposes, separate nonlinear statistical models have extensively been utilized. However, the single linear statistical modeling approach has numerous advantages such as providing estimators having good statistical properties, exact results, precise inference and simplicity in calculation. Therefore, this study was conducted to introduce the use of single linear regression modeling to compare release profiles statistically.

Clinical Performance and Wear Resistance of Two Compomers in Posterior Occlusal Restorations of Permanent Teeth: Six-Year Follow-up

The restoration quality has decreased and the wear increased for two compomers placed in the occlusal surface of permanent posterior teeth after six years; however, the restorations were clinically acceptable at the end of the evaluation.

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.

Effect of double-application of all-in-one adhesives on dentin bonding

OBJECTIVES

To evaluate the effect of double-application of all-in-one adhesives using the micro-shear bond test.

METHODS

The occlusal surfaces of extracted human third molars were ground perpendicular to the long axis of each tooth to expose a flat dentin surface. Three commercially available and one experimental bonding system were used in this study: Adper Prompt L-Pop (APL, 3M ESPE), REACTMER BOND (RB, Shofu), XENO III (Xeno, Dentsply-Sankin) and newly developed OBF-2 (OB2, Tokuyama Dental). These adhesives were applied on the dentin surfaces by either the manufacturers' instructions or by an experimental method (single-application or double-application). Resin composite was then placed and light-cured for 40s. After 24h immersion in water, a micro-shear bond test was carried out and the fractured dentin surfaces were observed microscopically. The data were analyzed by one-way ANOVA and Tukey's HSD tests (p<0.05).

RESULTS

The mean bond strengths of APL, RB, Xeno and OB2 with single-application were 22.7, 28.3, 30.3 and 34.6MPa, respectively. The mean bond strengths of APL, RB, Xeno and OB2 with double-application were 29.5, 27.2, 29.6 and 32.5MPa, respectively. There were no statistically significant differences in micro-shear bond strengths between the single- and double-application methods for each adhesive system (p>0.05). The morphological observation of the fractured dentin surfaces revealed differences between the single- and double-application groups especially for APL and OB2.

CONCLUSIONS

Micro-shear bond strengths of all-in-one adhesives in this study showed no statistically significant differences between the single-application and the double-application method.

Biological factors in dental caries: role of remineralization and fluoride in the dynamic process of demineralization and remineralization (part 3)

Dental caries is a complex disease process that afflicts a large proportion of the world, regardless of gender, age and ethnicity, although it does tend to affect more with a low socioeconomic status to a greater extent. Remineralization may be enhanced by providing low levels of calcium and phosphate, in conjunction with minimal amounts of fluoride. It is truly remarkable the difference that a very small amount of fluoride (<1 ppm) has upon demineralization and remineralization. This is because fluoride acts as a catalyst and influences reaction rates with dissolution and transformation of various calcium phosphate mineral phases within tooth structure and resident within plaque adjacent to tooth surfaces. The incorporation of minimal amounts of fluoride into HAP yields FHAP that resists demineralization to similar level as FAP. New and emerging methods have been and are in the process of being developed. These hold great promise for preventing and reversing caries, especially in the one-fifth of the population that accounts for two-thirds of the caries experience. Still, the mainstay in caries prevention and remineralization is frequent exposure to low levels of fluoride. This may be accomplished with fluoridated toothpastes, supplemented with fluoride mouthrinses, CPP-ACP containing chewing gum and application of fluoride varnishes. The role of systemic fluorides appears to be limited and primarily has a topical effect.