Different roles of FeS and FeS2 on magnetic FeSx for the selective adsorption of Hg2+ from waste acids in smelters: Reaction mechanism, kinetics, and structure-activity relationship.

Magnetic FeSx was developed as a high-performance sorbent for selectively adsorbing Hg2+ from waste acids in smelters. However, further improvement of its ability for Hg2+ adsorption was extremely restricted due to the lack of reaction mechanisms and structure-activity relationships. In this study, the roles of FeS and FeS2 on magnetic FeSx for Hg2+ adsorption were investigated with alternate adsorption of Hg2+ without/with Cl-. The structure-activity relationship of magnetic FeSx for Hg2+ adsorption and the negative effect of acid erosion were elucidated using kinetic analysis. FeS can react with Hg2+ with 1:1 stoichiometric ratio to form HgS, while FeS2 can react with Hg2+ in the presence of Cl- with novel 1:3 stoichiometric ratio to form Hg3S2Cl2. The rate of magnetic FeSx for Hg2+ adsorption was related to the instantaneous amounts of FeS and threefold FeS2 on magnetic FeSx and the amount of Hg2+ adsorbed. Meanwhile, its capacity for Hg2+ adsorption was related to the initial sum of FeS amount and threefold FeS2 amount on the surface and their ratios by acid erosion. Then, magnetic FeSx-400 was devised with adsorption rate of 2.12 mg g-1 min-1 and capacity of 1092 mg g-1 to recover Hg2+ from waste acids for centralized control.

The effect of location/site on polished human enamel after mechanical and chemical wear.

OBJECTIVE: To compare profilometry and microhardness of polished occlusal and buccal human enamel following a mechanical and chemical wear regime. METHODS: Enamel from polished human molars were sectioned into buccal and occlusal surfaces and randomly allocated into two groups (n = 10) and then exposed to 0.3 % citric acid at pH 2.7 for 10, 20, 40 and 60 mins each followed by abrasion with non-fluoridated toothpaste for 240 strokes in a reciprocating brushing machine. A white light profilometer with a spot size of 12 um measured mean step-height following each cycle. Microhardness indentations were conducted following the final cycled 60 mins erosion/abrasion using 0.01, 0.02, 0.1, 0.5 and 2.5 kgf indentation load. Statistical disparity were evaluated using a two-way ANOVA and post-hoc Sidak's multiple comparisons tests at α = 0.05. RESULTS: After erosion/abrasion, the mean (SD) step-heights on occlusal and buccal surfaces were not significantly different until 60 mins, when occlusal surfaces exhibited greater step-heights, 32.9 µm (2.8) and 31.1 µm (1.8) and p = 0.02, respectively. Buccal and occlusal microhardness was statistically lower following erosion/abrasion at loads of 0.01 kgf (p = 0.0005) and 0.02 kgf (p = 0.0006) but no significant differences were observed in the microhardness between the surfaces at any loads. CONCLUSION: The occlusal and buccal surfaces were not statistically different for microhardness or step height suggesting the susceptibility to wear is not related to the anatomy and structure of the tooth and is more likely related to other factors such as the environment. CLINICAL SIGNIFICANCE: The study emphasizes that a notable difference in wear between occlusal and buccal enamel surfaces emerges only after prolonged exposure to simultaneous chemical and mechanical stress. This finding necessitates a preventive dental approach that accounts for both the duration of exposure and environmental factors.

Effect of Iron Tailing Powder-Based Ternary Admixture on Acid Corrosion Resistance of Concrete.

Exposure of concrete to acidic environments can cause the degradation of concrete elements and seriously affect the durability of concrete. As solid wastes are produced during industrial activity, ITP (iron tailing powder), FA (fly ash), and LS (lithium slag) can be used as admixtures to produce concrete and improve its workability. This paper focuses on the preparation of concrete using a ternary mineral admixture system consisting of ITP, FA, and LS to investigate the acid erosion resistance of concrete in acetic acid solution at different cement replacement rates and different water-binder ratios. The tests were performed by compressive strength analysis, mass analysis, apparent deterioration analysis, and microstructure analysis by mercury intrusion porosimetry and scanning electron microscopy. The results show that when the water-binder ratio is certain and the cement replacement rate is greater than 16%; especially at 20%, the concrete shows strong resistance to acid erosion; when the cement replacement rate is certain and the water-binder ratio is less than 0.47; especially at 0.42, the concrete shows strong resistance to acid erosion. Microstructural analysis shows that the ternary mineral admixture system composed of ITP, FA, and LS promotes the formation of hydration products such as C-S-H and AFt, improves the compactness and compressive strength of concrete, and reduces the connected porosity of concrete, which can obtain good overall performance. In general, concrete prepared with a ternary mineral admixture system consisting of ITP, FA, and LS has better acid erosion resistance than ordinary concrete. The use of different kinds of solid waste powder to replace cement can effectively reduce carbon emissions and protect the environment.

Morphological and Elemental Evaluation of Investigative Mouthwashes to Repair Acid-Eroded Tooth Surface.

Purpose: Erosive tooth wear (ETW) is characterized by subsurface demineralization and tooth substance loss with crater formation. Remineralization of subsurface demineralization has previously been demonstrated; however, repair of the eroded surface is still under investigation. This study investigated the effectiveness of mouthwashes containing hydrolyzed wheat protein (HWP) in repairing ETW through promotion of organized crystal growth. Methods: Enamel Erosion was created on 210 enamel blocks by 10-minute demineralization in 1% Citric Acid (pH 3.5). Then, blocks were randomly assigned to seven groups (30/group); (A) 0.2% HWP, B) 1% HWP, (C) 2% HWP, (D) 1% HWP + 0.05% NaF, (E) Listerine™ mouthwash, (F) 0.02% NaF Crest™ Pro-health mouthwash and (G) artificial saliva (AS) only. Groups were subjected to daily pH-cycling consisting of one 5-minute erosive challenge with citric acid, three 1-minute mouthwash treatment periods, and then storage in AS for the rest of the time for 28 days. Treatment effects were assessed using SEM-EDX. Statistical analysis was by ANOVA and Tukey's multiple comparison. Results: In groups exposed to HWP-containing mouthwashes, there was growth of fiber-like crystals that increased in packing density in a dose-dependent manner (0.2%, 1%, 2%) on the eroded enamel surfaces, with increased calcium and phosphate contents on the treated surfaces. The non-HWP-containing groups had the eroded surfaces covered by structureless deposit layer firmly attached to the surface. Conclusion: Treating eroded enamel surface with HWP-containing mouthwash resulted in repair of the damaged tissue by formation of a protective layer of crystal deposits within and on the eroded enamel tissue.

Prevalence and Risk of Dental Erosion in Patients with Gastroesophageal Reflux Disease: A Meta-Analysis.

AIM: The present paper aims to systematize data concerning the prevalence and risk of dental erosion (DE) in adult patients with gastroesophageal reflux disease (GERD) compared to controls. MATERIALS AND METHODS: Core electronic databases, i.e., MEDLINE/PubMed, EMBASE, Cochrane, Google Scholar, and the Russian Science Citation Index (RSCI), were searched for studies assessing the prevalence and risk of DE in adult GERD patients with publication dates ranging from 1 January 1985 to 20 January 2022. Publications with detailed descriptive statistics (the total sample size of patients with GERD, the total sample size of controls (if available), the number of patients with DE in the sample of GERD patients, the number of patients with DE in the controls (if available)) were selected for the final analysis. RESULTS: The final analysis included 28 studies involving 4379 people (2309 GERD patients and 2070 control subjects). The pooled prevalence of DE was 51.524% (95 CI: 39.742-63.221) in GERD patients and 21.351% (95 CI: 9.234-36.807) in controls. An association was found between the presence of DE and GERD using the random-effects model (OR 5.000, 95% CI: 2.995-8.345; I2 = 79.78%) compared with controls. When analyzing studies that only used validated instrumental methods for diagnosing GERD, alongside validated DE criteria (studies that did not specify the methodologies used were excluded), a significant association between the presence of DE and GERD was revealed (OR 5.586, 95% CI: 2.311-13.503; I2 = 85.14%). CONCLUSION: The meta-analysis demonstrated that DE is quite often associated with GERD and is observed in about half of patients with this extremely common disease of the upper gastrointestinal tract.

The neutralizing effect of mouth rinsing with alkaline electrolyzed water on different regions of the oral cavity acidified by acidic beverages.

PURPOSE: Acids contained in foods and drinks are involved in the initiation and progression of dental erosion which causes tooth wear. The authors evaluated the neutralizing activity of alkaline electrolyzed water (AEW) in vitro and in vivo. METHODS: The neutralizing ability of AEW against eight beverages was investigated in vitro. Furthermore, in an in vivo study, the effect of mouth rinsing with AEW on the pH of the oral cavity acidified with acidic beverages was examined. Following mouth rinsing, the oral pH was measured using a pH meter with a micro pH-sensor at the cervical surface of the mandibular teeth and the surface of soft tissues. RESULTS: Regarding the neutralizing ability, the higher the pH of the AEW, the lower the volume required for neutralization of the tooth surface. Changes in the pH by mouth rinsing with AEW and purified tap water (PTW) were analyzed. The degree of increase of pH with AEW was greater than with PTW at almost all sites. CONCLUSION: These results suggest that AEW has the potential to prevent the initiation and progression of dental erosion. Mouth rinsing with AEW could be a simple and effective way to prevent the initiation and progression of dental erosion and dental caries.

Alternativas de tratamiento para pacientes jóvenes con pérdida de estructura dentaria. Parte 1: caso clínico / Treatment alternatives for young patients with loss of dental structure. Part 1: a clinical Case

El objetivo de este artículo es presentar una alternativa de tratamiento rehabilitador para pacientes jóvenes con gran pérdida de estructura dental vinculada a lesiones de origen no bacteriano. Se presenta el caso clínico de un paciente de 36 años de edad, con reflujo gastroesofágico crónico bajo tratamiento médico, que concurrió a la Cátedra de Odontología Integral Adultos de la Facultad de Odontología de la Universidad de Buenos Aires (FOUBA), en busca de un cambio estético en su sonrisa y relatando sensibilidad al calor, al frío y dolor al masticar. No manifestó sintomatología dolorosa a nivel muscular ni articular. En función de sus posibilidades económicas y de la etiología erosiva de las lesiones existentes en sus piezas dentarias, se llevó a cabo una rehabilitación oral adhesiva con resinas compuestas utilizando la sistematización de atención que sugiere la Cátedra. Las resinas compuestas actuales, en combinación con las técnicas y procedimientos desarrollados en este artículo han demostrado un adecuado comportamiento al ser utilizadas como restauraciones definitivas en pacientes que necesitan rehabilitación oral total debido a la gran pérdida de estructura dental por erosión ácida (AU)

Sorción de humedad y resistencia a la disolución ácida de dos ionómeros de vidrio de restauración: estudio in vitro / Sorption of moisture and resistance to acid dissolution of two restoration glass ionomers: in vitro study

Resumen Introdución: En general el Ionómero de vidrio tiene algunas desventajas en la parte clínica, como es la fragilidad y la sensibilidad inicial a la humedad, lo que puede causar una disminución de la vida útil de la restauración. Estos efectos que sufre el ionómero como la sorción de humedad y la solubilidad a los ácidos puede causar daño a la restauración, facilitar su fractura y filtración marginal, lo que puede conllevar a una recidiva de caries y pérdida de sus propiedades. Objetivo: comparar in vitro la sorción de humedad y disolución ácida de dos ionómeros de restauración. Método: Se elaboraron 20 muestras de ionómero de vidrio Ketac molar y 20 de Fuji II. Se realizó una primera medición del peso con balanzas de precisión, obteniéndose un peso inicial. Los especímenes fueron sumergidos en agua destilada durante 24 horas, almacenadas en un calefactor; cada muestra fue pesada con una balanza de precisión, estableciéndose el porcentaje de humedad sorbida a partir del peso inicial. Posteriormente las muestras fueron sumergidas en solución de ácido cítrico al 3% durante 24 horas, para volver a ser pesadas, evaluándose la perdida de material por acción erosiva del ácido en porcentaje de peso. Conclusiones: La sorción de humedad en peso fue de 2,59% en el ketac molar y 1,45% en el Fuji II; al comparar las muestras mediante la prueba t, se obtuvo diferencias estadísticamente significativas. El porcentaje de pérdida de material por acción erosiva del ácido fue de 10,81% para Ketac molar y 18,62% para el Fuji II; al comparar las muestras mediante la prueba t, se obtuvo diferencias estadísticamente significativas. Se concluyó que la sorción de humedad fue mayor en el Ketac molar y la mayor solubilidad a la acción del ácido cítrico fue del Fuji II.

Abstract Introduction: Glass Ionomer has certain clinical disadvantages, such as fragility and moisture sensitivity, which might reduce the restauration´s lifespan. This effects, such as water absorption and acid solubility may damage the restauration, cause fracture and marginal filtration, this could trigger cavity relapse and the loss of the correct mechanical properties. Objective: Compare in vitro moisture sorption and acid solution of two restoration ionomers. Method: 20 samples of Ketac molar glass ionomer and 20 of Fuji II were made. A first weight measurement was made with precision scales, obtaining an initial weight. The specimens were submerged in distilled water for 24 hours, stored in a heater; Each sample was weighed with a precisión balance, establishing the percentage of moisture absorbed from the initial weight. Subsequently, the samples were submerged in 3% citric acid solution for 24 hours, to be re-weighed, evaluating the loss of material due to erosive action of the acid in percentage of weight. Conclusions: The moisture sorption by weight was 2.59% in the molar ketac and 1.45% in the Fuji II; When comparing the samples using the t-test, statistically significant differences were obtained. The percentage of material loss due to erosive action of the acid was 10.81% for molar Ketac and 18.62% for Fuji II; When comparing the samples using the t-test, statistically significant differences were obtained. It was concluded that the moisture sorption was higher in the molar Ketac and the greatest solubility to the action of citric acid was Fuji II.

Direct composite resin restorations for teeth with dental erosion: a case report.

Acid erosion should be treated according to its multifactorial etiology. This case report describes a patient with tooth wear caused by daily intake of acidic carbonated beverages. After meticulous clinical and radiographic analysis, the clinician restored the teeth temporarily with chemically cured glass ionomer cement. Afterward, the patient underwent basic periodontal therapy with scaling and coronal polishing. The patient received guidance regarding daily oral hygiene and eating habits to control the ingestion of acidic drinks. After reestablishing adequate oral conditions, the clinician placed direct composite resin restorations on the maxillary anterior teeth that displayed dental erosion. The clinical procedures improved the patient's oral health as well as the form, esthetics, and function of the worn teeth.

Protocol for measurement of enamel loss from brushing with an anti-erosive toothpaste after an acidic episode.

Tooth erosion from an acidic insult may be exacerbated by toothbrushing. The purposes of this study were to develop an in vitro methodology to measure enamel loss after brushing immediately following an acidic episode and to investigate the effect of brushing with an anti-erosive toothpaste. The null hypotheses tested were that tooth erosion after brushing with the toothpaste would not be different from brushing with water and that a 1-hour delay before brushing would not reduce tooth erosion. Forty bovine enamel slabs were embedded, polished, and subjected to baseline profilometry. Specimens were bathed in hydrochloric acid for 10 minutes to simulate stomach acid exposure before post-acid profilometry. Toothbrushing was then simulated with a cross-brushing machine and followed by postbrushing profilometry. Group 1 was brushed with water; group 2 was brushed with a 50:50 toothpaste-water slurry; and groups 3 and 4 were immersed in artificial saliva for 1 hour before brushing with water or the toothpaste slurry, respectively. The depth of enamel loss was analyzed and compared using 1-way analysis of variance and post hoc testing (α = 0.05). Greater enamel loss was measured in groups brushed with toothpaste than in groups brushed with water. One-hour immersion in artificial saliva significantly reduced enamel loss when teeth were brushed with water (group 3; P < 0.05) but not with toothpaste (group 4). This study established a protocol for measuring enamel loss resulting from erosion followed by toothbrush abrasion. The results confirmed the abrasive action of toothpaste on acid-softened enamel.

[Impact of Human Activities on Water-Rock Interactions in Surface Water of Lijiang River].

The influence of human activities on karst surface water quality has received increasing attention. To explore the impact of human activities on water-rock interactions in karst surface water, water samples were collected from July to November in 2016 in the Lijiang River, which is dominated by human activities. The samples were analyzed for the hydrochemistryand the characteristics of δ13CDIC. The results show that:①The Lijiang River is mainly characterized by HCO3-Ca chemical composition.. The SO42- and NO3- concentrations are inferior to HCO3- concentrations in the anion composition; besides, the concentrations of SO42- and NO3- in the river between Guilin and Yangshuo are higher than in the other sampling sites, caused by tourism and urban development. ②Equivalent ratios of[Ca2++Mg2+]/[HCO3-] are between 1.01 and 1.51 and the equivalent ratios of[Ca2++Mg2+]/[SO42-+NO3-+HCO3-] are between 0.85 and 1.12, indicating that the sulfuric acid and nitric acid have participated in the water-rock interaction. ③The proportions of carbonic acid dissolving carbonate rocks range from 32.10%-98.01% with an average of 75.89%. The proportions of sulfuric acid and nitric acid dissolving carbonate rocks vary from 1.99%-67.90% with an average of 24.11%. The proportions of sulfuric acid and nitric acid dissolving carbonate rocks in the rainy period with an average of 24.31% is higher than in the brief rain period with an average of 23.88%. In addition, the proportions of sulfuric acid and nitric acid dissolving carbonate rocks present a fluctuated increasing trend from upstream to downstream and the maximum strength and the minimum strength of the sulfuric and nitric acid dissolving carbonate rocks occur in Lingchuan and Huajiang, respectively. ④ HCO3- mainly originated from the carbonate rocks dissolved by carbonic acid, with an average of 83.58%, followed by the carbonate rocks dissolved by sulfuric acid and nitric acid, with an average of 14.24%. The contribution of carbonic acid weathering silicate rocks is the smallest with an average of 2.18%. ⑤ δ13CDIC of the Lijiang River ranges from -11.95‰--7.61‰; the calculated δ13CDIC-rock using the mixture endmember model ranges from -14.24‰--7.23‰. δ13CDIC is close to δ13CDIC-rock in the rainy period and δ13CDIC is significantly higher than δ13CDIC-rock in the brief rain period. The difference between δ13CDIC and δ13CDIC-rock is caused by the influence of aquatic photosynthetic organisms.

Sorción de humedad y resistencia a la disolución ácida de dos ionómeros de vidrio de restauración: estudio in vitro

Introdución: En general el Ionómero de vidrio tiene algunas desventajas en la parte clínica, como es la fragilidad y la sensibilidad inicial a la humedad, lo que puede causar una disminución de la vida útil de la restauración. Estos efectos que sufre el ionómero como la sorción de humedad y la solubilidad a los ácidos puede causar daño a la restauración, facilitar su fractura y filtración marginal, lo que puede conllevar a una recidiva de caries y pérdida de sus propiedades. Objetivo: comparar in vitro la sorción de humedad y disolución ácida de dos ionómeros de restauración. Método: Se elaboraron 20 muestras de ionómero de vidrio Ketac molar y 20 de Fuji II. Se realizó una primera medición del peso con balanzas de precisión, obteniéndose un peso inicial. Los especímenes fueron sumergidos en agua destilada durante 24 horas, almacenadas en un calefactor; cada muestra fue pesada con una balanza de precisión, estableciéndose el porcentaje de humedad sorbida a partir del peso inicial. Posteriormente las muestras fueron sumergidas en solución de ácido cítrico al 3% durante 24 horas, para volver a ser pesadas, evaluándose la perdida de material por acción erosiva del ácido en porcentaje de peso. Conclusiones: La sorción de humedad en peso fue de 2,59% en el ketac molar y 1,45% en el Fuji II; al comparar las muestras mediante la prueba t, se obtuvo diferencias estadísticamente significativas. El porcentaje de pérdida de material por acción erosiva del ácido fue de 10,81% para Ketac molar y 18,62% para el Fuji II; al comparar las muestras mediante la prueba t, se obtuvo diferencias estadísticamente significativas. Se concluyó que la sorción de humedad fue mayor en el Ketac molar y la mayor solubilidad a la acción del ácido cítrico fue del Fuji II.

Introduction: Glass Ionomer has certain clinical disadvantages, such as fragility and moisture sensitivity, which might reduce the restauration´s lifespan. This effects, such as water absorption and acid solubility may damage the restauration, cause fracture and marginal filtration, this could trigger cavity relapse and the loss of the correct mechanical properties. Objective: Compare in vitro moisture sorption and acid solution of two restoration ionomers. Method: 20 samples of Ketac molar glass ionomer and 20 of Fuji II were made. A first weight measurement was made with precision scales, obtaining an initial weight. The specimens were submerged in distilled water for 24 hours, stored in a heater; Each sample was weighed with a precisión balance, establishing the percentage of moisture absorbed from the initial weight. Subsequently, the samples were submerged in 3% citric acid solution for 24 hours, to be re-weighed, evaluating the loss of material due to erosive action of the acid in percentage of weight. Conclusions: The moisture sorption by weight was 2.59% in the molar ketac and 1.45% in the Fuji II; When comparing the samples using the t-test, statistically significant differences were obtained. The percentage of material loss due to erosive action of the acid was 10.81% for molar Ketac and 18.62% for Fuji II; When comparing the samples using the t-test, statistically significant differences were obtained. It was concluded that the moisture sorption was higher in the molar Ketac and the greatest solubility to the action of citric acid was Fuji II.

The effect of air-abrasion on the susceptibility of sound enamel to acid challenge.

OBJECTIVE: To evaluate the effect of air-abrasion using three abrasive powders, on the susceptibility of sound enamel to an acid challenge. METHODS: 40 human enamel samples were flattened, polished and assigned to 4 experimental groups (n=10); a: alumina air-abrasion, b: sodium bicarbonate air-abrasion, c: bioactive glass (BAG) air-abrasion and d: no surface treatment (control). White light confocal profilometry was used to measure the step height enamel loss of the abraded area within each sample at three stages; after sample preparation (baseline), after air-abrasion and finally after exposing the samples to pH-cycling for 10 days. Data was analysed statistically using one-way ANOVA with Tukey's HSD post-hoc tests (p<0.05). Unique prismatic structures generated by abrasion and subsequent pH cycling were imaged using multiphoton excitation microscopy, exploiting strong autofluorescence properties of the enamel without labelling. Z-stacks of treated and equivalent control surfaces were used to generate non-destructively 3-dimensional surface profiles similar to those produced by scanning electron microscopy. RESULTS: There was no significant difference in the step height enamel loss after initial surface air-abrasion compared to the negative control group. However, a significant increase in the step height enamel loss was observed in the alumina air-abraded samples after pH-cycling compared to the negative control (p<0.05). Sodium bicarbonate as well as BAG air-abrasion exhibited similar enamel surface loss to that detected in the negative control group (p>0.05). Surface profile examination revealed a deposition effect across sodium bicarbonate and BAG-abraded groups. CONCLUSION: This study demonstrates the importance of powder selection when using air abrasion technology in clinical dentistry. Pre-treating the enamel surface with alumina air-abrasion significantly increased its susceptibility to acid challenge. Therefore, when using alumina air-abrasion clinically, clinicians must be aware that abrading sound enamel excessively renders that surface more susceptible to the effects of acid erosion. BAG and sodium bicarbonate powders were less invasive when compared to the alumina powder, supporting their use for controlled surface stain removal from enamel where indicated clinically.

Dose-response effect of fluoride dentifrice on remineralisation and further demineralisation of erosive lesions: A randomised in situ clinical study.

OBJECTIVE: The objective was to evaluate the ability of fluoride in a conventional, non-specialised sodium fluoride-silica dentifrice to promote tooth remineralisation and enamel fluoride uptake (EFU), and assess the resistance of the newly formed mineral to attack by dietary acid, across the concentration range used in mass-market dentifrices. METHODS: Subjects wore a palatal appliance containing eight polished bovine enamel specimens, each including an early erosive lesion. In a randomised full-crossover sequence, 62 healthy subjects were treated with dentifrices containing four different fluoride concentrations: no fluoride; 250ppm, 1150ppm and 1426ppm fluoride. At each treatment visit, under supervision, subjects brushed with 1.5g dentifrice and rinsed once while wearing the appliance; the appliance was removed after a 4-h remineralisation period and effects on the enamel specimens determined. The primary efficacy variable was surface microhardness recovery (SMHR); others included EFU, relative erosion resistance (RER) and comparative erosion resistance. RESULTS: Highly significant linear and, with the exception of SMHR, quadratic dose-response relationships were observed between all efficacy variables and fluoride concentration. For SMHR, EFU and RER, values for the different fluoride concentrations were statistically resolved from one another, with the exception of the two highest fluoride concentrations. The degree of remineralisation and the acid resistance of enamel after treatment were closely related to EFU. CONCLUSION: After a single brushing, conventional non-specialised sodium fluoride-silica dentifrices promoted remineralisation of early enamel lesions, and imparted increased acid-resistance to the enamel surface, in a dose-dependent manner at least up to 1500ppm fluoride. CLINICAL SIGNIFICANCE: Enamel erosive tissue loss is an increasing concern, associated with modern diets. This study demonstrated that sodium fluoride, in a conventional non-specialised dentifrice formulation, can promote repair of the earliest stages of enamel erosion after a single application, in a dose-dependent fashion across the fluoride concentration range used in mass-market dentifrices. This study is registered in the GlaxoSmithKline Study Register (ID RH01299), available at: www.gsk-clinicalstudyregister.com/study/RH01299.

Tooth wear with an erosive component in a Mediaeval Iceland population.

OBJECTIVES: Dental erosion is generally thought of as a modern phenomenon, but there is emerging evidence that the condition has always been present in the human dentition to some degree. The aim of this study was to quantitatively evaluate the severity of tooth wear observed in skeletal material from a mediaeval population of the farm at Hofstaðir, Mývatnssveit, in northeast Iceland. METHODS: The teeth were examined and tooth wear was quantified using the Smith and Knight Tooth Wear Index. All surfaces of the teeth were examined by a single trained examiner from 53 adult skulls available (24 males and 29 female). The majority of the skulls were examined at the stores of Þjóðminjasafn Íslands (The National Museum of Iceland) using good lighting and magnification. RESULTS: There were a total of 1696 possible teeth and 6784 surfaces, and from this 69.5% were scored. There was a higher overall rate of wear in the mandibular dentitions and that the highest wear rates were seen on the occlusal/incisal surfaces of the 1st and 2nd molars and the premolars. For the group, and from those surfaces available for scoring, dentine was exposed on 1464 surfaces (31%). There was no evidence of cervical wear. CONCLUSION: High levels of tooth wear were observed in this Icelandic assemblage and the appearance was characteristic of both chemical and physical wear.

Microstructural analysis of restorative materials submitted to acid exposure / Análise microestrutural de materiais restauradores submetidos à exposição ácida

The study aimed to evaluate, through surface roughness and microhardness tests, the amount of damage caused by hydrochloric acid to restorative materials. Five different materials were used: direct composite resin (Z 350), indirect composite resin (Resilab Master), conventional glass-ionomer cement (GIC) (Vidrion R), resin modified GIC (Vitremer) and ceramic (Empress II). Twenty one specimens of each material were constructed and had their initial roughness and microhardness evaluated. Sixteen specimens of each material were immersed in a gastric fluid without enzymes simulating acid episodes. Other 5 specimens of each material were immersed in artificial saliva (control groups). After 7 days of immersion, the specimens had their surfaces evaluated again. Then, after another 21 days of immersion the specimens were submitted to a third mensuration. One specimen at each stage of the research was subjected to analysis in scanning electronic microscopy. The samples demonstrated changes in roughness and microhardness after the immersion of the restorative materials in the acid solution. The roughness results showed that for both glass ionomer cements, there was a significant difference between the first and last reading, with an increase in their roughness. In ceramic and direct resin materials, no significant difference among the periods was observed. Concerning to microhardness, the behavior of the materials showed a tendency towards decreasing hardness. The results showed the degradation of the restorative materials when exposed to acid episodes

O estudo teve como objetivo avaliar por meio dos testes de rugosidade superficial e microdureza os danos causados pelo ácido clorídrico em materiais restauradores. Utilizaram-se 5 materiais: resina composta direta (Z 350), resina composta indireta (Resilab Master), cimento de ionômero de vidro (CIV) convencional (Vidrion R), CIV modificado por resina (Vitremer) e uma cerâmica (Empress II). Vinte e um corpos de prova (cdp) de cada material foram confeccionados e tiveram suas superfícies iniciais avaliadas em um rugosímetro e um microdurômetro. Em seguida 16 cdp de cada material foram imersos em um suco gástrico sem enzimas simulando episódios ácidos. Outros 5 cdp de cada material serviram como grupo controle e ficaram imersos em saliva artificial. Após 7 dias de imersão os cdp tiveram suas superfícies novamente avaliadas. Após a segunda leitura, foi realizada imersão por mais 21 dias, completando um mês de experimento, e os cdp foram submetidos à terceira leitura de suas superfícies. Além disso, 1 cdp em cada fase da pesquisa foi submetido a uma análise em microscopia eletrônica de varredura (MEV) apenas como efeito ilustrativo. Amostras demonstraram alterações de rugosidade e microdureza diante da imersão de materiais restauradores em ácido. Os resultados de rugosidade mostraram que tanto para o ionômero convencional quanto para o modificado por resina houve uma diferença significante entre a primeira e a última leitura, havendo um aumento na rugosidade. Já para a cerâmica e a resina direta, não houve alteração significativa entre os períodos. O comportamento dos materiais mostrou uma tendência de diminuição da microdureza. Conclui-se que existe uma deterioração dos materiais restauradores frente a episódios ácidos