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PURPOSE: Physiological and erosive wear reported in clinical studies were reviewed, and in vitro aging models were developed to simulate and compare the effect of aging on human teeth with the review data obtained from clinical studies. METHODS: A review of clinical studies and randomized clinical trials that quantify enamel wear was performed in the PubMed database. The first in vitro analysis evaluated the effect of mechanical chewing simulation only. Enamel specimens were aged in the chewing simulator (up to 1.2 million cycles) with two occlusal loads (30 and 50 N). In the second in vitro analysis, specimens were aged in two aging models. The first model (MT) simulated mechanical and thermal oral challenges: MT1- 240,000 chewing and 10,000 thermal cycles, MT2- 480,000 chewing and 20,000 thermal cycles, MT3- 1.2 million chewing and 50,000 thermal cycles. The second model (MTA) simulated mechanical, thermal, and acidic oral challenges as follows: MTA1- 240,000 chewing, 10,000 thermal and 3-h acidic cycles; MTA2: 480,000 chewing, 20,000 thermal and 6-h acidic cycles, MTA3- 1.2 million chewing, 50,000 thermal and 15-h acidic cycles. RESULTS: The review included 13 clinical studies evaluating tooth wear (eight physiological and five erosive). The results estimated the annual average physiological wear as 38.4 µm (9.37-51). In comparison, the MT1 showed wear of 60 (24) µm. Also, the average annual erosive wear in the literature was 179.5 µm (70-265) compared to MTA1-induced wear of 209 (14) µm. CONCLUSION: There was wide variation in tooth wear reported in clinical studies, suggesting a critical need for more accurate studies, possibly based on scanning technologies. Despite this, the data reported using the novel aging models are within a range to be considered consistent with and to simulate tooth wear measured in vivo.

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The article presents research results on the possibility of shaping the structure and properties of Co-Cr-W-C-Ti alloys (type Stellite 6) using laser cladding technology. Cobalt-based alloys are used in several industries because they are characterized by high erosion, abrasion, and corrosion resistance, retaining these properties at high temperatures. To further increase erosion resistance, it seems appropriate to reinforce material by in situ synthesis of hard phases. Among the transition metal carbides (TMCs), titanium carbide is one of the hardest and can have a positive effect on the extension of the lifetime of components made from cobalt-based alloys. In this article, concentration of C, W, and Ti due to the possibility of in situ synthesis of titanium carbides was subjected to detailed analysis. The provided research includes macrostructure and microstructure analysis, X-ray diffraction (XRD), microhardness, and penetrant tests. It was found that the optimal concentrations of Ti and C in the Co-Cr-W-C alloy allow the formation of titanium carbides, which significantly improves erosion resistance for low impact angles. Depending on the concentrations of titanium, carbon, and tungsten in the molten metal pool, it is possible to shape the alloy structure by influencing to morphology and size of the reinforcing phase in the form of the complex carbide (Ti,W)C.

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BACKGROUND: The study objective was to examine the effect of arginine-sodium fluoride (Arg-NaF) varnish on preventing enamel erosion by acidic paediatric liquid medicaments (PLM). METHODS: The treatment groups were: 1) 2% Arg-NaF; 2) 4% Arg-NaF; 3) 8% Arg-NaF; 4) NaF; 5) MI (CPP-ACFP) varnishes; and 6) no varnish. The pH of PLM (paracetamol and chlorpheniramine) was measured at baseline and after immersing the Perspex® blocks coated with varnishes at 0 min, 30 min, 1 h, and 4 h. Seventy-two enamel specimens (n = 72) were randomly divided into 2 groups by PLM and further by treatment groups. Then, the specimens were pre-treated with varnishes and subjected to erosive cycles (5 min, 2×/day for 4 days) by PLM. After each erosive challenge, the specimens were stored in artificial saliva. At baseline and after 4 days, the specimens were assessed for surface roughness (Ra) using 2D-surface profilometric analysis (SPA) and atomic force microscopy (AFM). Additionally, the Ca/P ratio was determined using scanning electron microscopy with energy-dispersive X-ray spectroscopy. Paired samples dependent t-test, 1-way ANOVA and 2-way ANOVA with Bonferroni post-hoc tests were used to analyse data with the level of significance set at p < 0.05. RESULTS: The pH of PLM with 8% Arg-NaF was significantly higher than the other groups at 30 min and 4 h (p < 0.05). With paracetamol, no significant difference was observed between the baseline and post-erosive cycle measured enamel Ra (by SPA/AFM) and Ca/P ratio for all treatment groups (p > 0.05). The Ra determined by AFM, at the post-erosive cycle with chlorpheniramine, when treated with 4 and 8% Arg-NaF was significantly lower than the other groups (p < 0.05); except CPP-ACFP (p > 0.05). With the chlorpheniramine post-erosive cycle, the Ca/P ratio for 4, 8% Arg-NaF and CPP-ACFP treated specimens was significantly higher than the baseline Ca/P (p < 0.05). CONCLUSION: The 4%/8% Arg-NaF and MI varnish® application exhibit an enhanced preventive effect against low pH (pH < 3.0) PLM-mediated enamel erosive challenges compared to 5% NaF varnish.

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Direct-drive electro-hydraulic servo valves play a key role in aerospace control systems, and their operational stability and safety reliability are crucial to the safety, stability, and efficiency of the entire control system. Based on the prediction of the performance change of the servo valve and the resulting judgement and prediction of its life, this can effectively avoid serious accidents and economic losses caused by failure due to performance degradation in the work. On the basis of existing research, factors such as opening, oil contamination, and pressure difference are used as prerequisites for the operation of direct-drive electro-hydraulic servo valves. In addition to the current research on pressure gain and leakage, the performance parameters of servo valves, such as overlap, threshold, and symmetry, are also expanded and selected as research objects, combined with pressure design servo valve performance degradation experiments for testing instruments such as flow and position sensors, and data are obtained on changes in various performance parameters. The experimental data are analyzed and a prediction model is built to predict the performance parameters of the servo valve by combining the existing popular neural networks, and the prediction error is calculated to verify the accuracy and validity of the model. The experimental results indicate that as the working time progresses, the degree of erosion and wear on the valve core and valve sleeve of the servo valve increases. Overall, it has been observed that the performance parameters of the servo valve show a slow trend of change under different working conditions, and the rate of change is generally higher under high pollution (level 9) conditions than under other conditions. The prediction results indicate that the predicted values of various performance parameters of the servo valve by the prediction model are lower than 0.2% compared to the experimental test set data. By comparing the two dimensions of the accuracy and prediction trend, this model meets industrial needs and outperforms deep learning algorithm models such as the exponential smoothing algorithm and ARIMA model. The experiments and results of this study provide theoretical support for the life prediction model of servo valves based on neural networks and machine learning in artificial intelligence, and provide a reference for the development of direct-drive electro-hydraulic servo valves in aerospace and other industrial fields for use and failure standards.

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OBJECTIVES: This systematic review evaluated the efficacy of monovalent and polyvalent fluoride group compared to the non-fluoride group on the prevention of enamel erosion associated or not with abrasion in in situ studies. DESIGN: This review was registered in the PROSPERO (CRD42017071118) and followed PRISMA 2020 guidelines. A systematic and comprehensive search was performed using PUBMED, WEB OF SCIENCE, SCOPUS, EMBASE, BBO, LILACS, SCIELO, and grey literature IBICT-BDTD. All in situ and ex vivo studies of erosion and erosion/abrasion tooth wear were included, with no language or date restrictions. RESULTS: 730 studies were obtained and after exclusion of duplicates, 311 were included for title and abstract reading. Two independent authors (kappa= 0.98) systematically conducted the selection phase. Considering the eligibility criteria and after full-text reading, 19 studies were included in qualitative and quantitative analysis. CONCLUSION: Network metanalysis showed that polyvalent fluoride group, especially Sn-compounded, prevented enamel wear by erosion and erosion/abrasion compared to the non-fluoride group and monovalent fluoride group. Both low and high concentration monovalent fluoride group were not able to prevent erosion wear associated or not with abrasion. Sensitivity analysis of the network metanalysis was performed with the low risk of bias studies and the results were confirmed. There is robust evidence that stannous-compounded fluoridated and titanium tetrafluoride agents are effective in preventing erosion and erosion/abrasion compared to the non-fluoride group and other interventions.

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While evidence shows that dental erosion (DE) is often caused by gastroesophageal reflux disease (GERD), the relationship of DE severity to a patient's symptoms and receipt of appropriate medical treatment for GERD is not clearly understood. The purpose of this study was to evaluate the association between DE and GERD. Eighty participants underwent a Basic Erosive Wear Examination for DE and completed the Patient-Reported Outcomes Measurement Information System (PROMIS) survey on symptoms of gastrointestinal reflux (PROMIS Scale v1.0, Gastrointestinal Gastroesophageal Reflux 13a) in English. Patients with observed erosive patterns were referred for gastroenterologic evaluation. The association between DE and GERD was assessed using multiple regression. The results showed that the extent of DE was positively associated with GERD symptoms (B = 0.585; 95% CI, 0.21-0.96), as measured by the PROMIS survey, in participants without a current diagnosis of GERD. Of the 80 patients in the study, 28 with more severe DE were evaluated in the gastroenterology department. A diagnosis of GERD was established for 27 of the 28, 9 of whom denied a past history of the disease. Twenty patients with GERD underwent upper endoscopy, and esophageal lesions were found in 6 patients (erosive esophagitis in 5 and Barrett esophagus in 1). Patients with clinically identified DE may benefit from medical evaluation and, if necessary, management of GERD. For a subset of patients, DE may be the only clinical indication of untreated or undertreated GERD, which could lead to serious esophageal changes. Dentists should consider referring patients with DE to primary care providers or gastrointestinal specialists to ensure that systemic conditions are identified and managed appropriately.

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Erosion caused by the repeated impact of particles on the surface of a substance is a common wear method resulting in the gradual and continual loss of affected objects. It is a crucial problem in several modern industries because the surfaces of various products and materials are frequently subjected to destructively erosive situations. Polymers and their hybrid materials are suitable, in powdered form, for use as coatings in several different applications. This review paper aims to provide extensive information on the erosion behaviors of thermoset and thermoplastic neat resin and their hybrid material composites. Specific attention is paid to the influence of the properties of selected materials and to impingement parameters such as the incident angle of the erodent, the impact velocity of the erodent, the nature of the erodent, and the erosion mechanism. The review further extends the information available about the erosion techniques and numerical simulation methods used for wear studies of surfaces. An investigation was carried out to allow researchers to explore the available selection of materials and methods in terms of the conditions and parameters necessary to meet current and future needs and challenges, in technologically advanced industries, relating to the protection of surfaces. During the review, which was conducted on the findings in the literature of the past fifty years, it was noted that the thermoplastic nature of composites is a key component in determining their anti-wear properties; moreover, composites with lower glass transition, higher ductility, and greater crystallinity provide better protection against erosion in advanced surface applications.

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BACKGROUND: Despite increasing prevalence, age-specific risk predictive models for erosive tooth wear in preschool-age children have not been developed. Identification of at-risk groups and the timely introduction of behavioural change or treatment will stop the progression of erosive wear in the permanent dentition. This study aimed to identify age-specific risk factors for erosive wear. Distinct risk prediction models for 3-year-old and 5-year-old children were developed. METHODS: A prospective cohort study included school-based clinical examinations and parent administered questionnaires for consented 3 and 5-year-old healthy children. Calibrated examiners measured the following health parameters under standardised conditions: erosion, using the Basic Erosive Wear Examination Index (BEWE), caries using the International Caries Detection and Assessment System (ICDAS), plaque and calculus according to the British Association for the Study of Community Dentistry (BASCD) scores, dental traumatic injuries and soft tissue lesions, salivary testing and BMI. Other health conditions were collected via a parent-administered questionnaire that explored oral- and general-health. Non parametric tests were utilised to explore the temporal relation of erosion with, demographic factors, oral hygiene habits, general health and dietary habits. Variables showing significance with a difference in BEWE cumulative score over time were utilised to develop two risk prediction models. The models were evaluated by Receiver Operating Characteristics analysis. RESULTS: Risk factors for the 3-year-old cohort (N = 336) included erosive wear (χ2(1, 92) = 12.829, p < 0.001), district (χ2(5, 92) = 17.032, p = 0.004) and family size (χ2(1, 92) = 4.547, p = 0.033). Risk factors for the 5-year-old cohort (N = 441) also included erosive wear (χ2(1, 144) = 4.768, p = 0.029), gender (χ2(1, 144) = 19.399, p < 0.001), consumption of iced tea (χ2(1, 144) = 8.872, p = 0.003) and dry mouth (χ2(1, 144) = 9.598, p = 0.002). CONCLUSIONS: Predictive risk factors for 3-year-old children are based on demographic factors and are distinct from those for 5-year-old children based on biological and behavioural factors. Erosive wear is a risk factor for further wear in both age cohorts.

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PURPOSE: The aim of the study was to assess the prevalence of erosive tooth wear (ETW) and risk indicators in the population of adolescents aged 15 in Poland. METHODS: Erosive tooth wear in 2639 participants was determined by calibrated examiners according to the BEWE scoring system, and the prevalence of risk factors was assessed on the basis of a survey. RESULTS: Erosive tooth wear was reported in 24.3% of participants. Initial loss of surface (BEWE 1) was the predominant finding, observed in 21.3% of participants. Hard tissue loss (BEWE 2 and 3) occurred very rarely, only in 3% of participants. Acidic diet, masculine gender and lower socio-economic status were associated with higher prevalence and severity of erosive lesions in the examined population. CONCLUSION: Two modifiable factors-acidic diet and low health awareness-were found to be highly unsatisfactory in the adolescents aged 15 in Poland. Accordingly, to prevent the deterioration of the functionality and aesthetics of the teeth in young people, certain measures, such as routine clinical examination, education, dietary consulting and prophylaxis, should be implemented as early as possible, focusing predominantly on families with lower socio-economic status.

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Objetivo: determinar prevalencia, extensión, severidad y distribución del desgaste erosivo (DE) en preescolares de Montevideo. Metodología: estudio transversal de base poblacional, muestra representativa de centros educativos públicos y privados. Fueron indagados aspectos sociodemográficos, biológicos y de comportamiento con un cuestionario auto-reportado por padres/responsables. Los exámenes fueron realizados por dos operadores Kappa ≥ 0,7. DE fue registrado con el índice O´Brien modificado, reportándose porcentaje y promedio; intervalo de confianza (IC) 95%. Se realizaron análisis de asociación con sexo y nivel socioeconómico. Resultados: se examinaron 614 preescolares. Prevalencia: 57,6% (IC95%: 52,7-62,5). Extensión: 4,8 (IC95%: 4,3-5,3). DE severo: 8,2% (IC95%: 5,5-10,9) Las superficies más afectadas fueron palatino de incisivos superiores. Los preescolares de nivel socioeconómico alto presentaron mayor DE que los de nivel bajo; 73,1% (IC95%:61,9-84,2) y 48,4% (IC95%:39,2-57,7) respectivamente (p≤0,01). Conclusiones: la prevalencia y extensión del DE fue alta. Estos datos pueden contribuir en la modificación de medidas que apunten a controlar la prevalencia de DE.

Aims: assess the prevalence, extent,severity, and distribution of erosive tooth wear (ETW) in preschoolers of Montevideo. Methods: cross-sectional populationbased study of representative sample of public and private educational centers. Sociodemographic, biological, and behavioral aspects were investigated with a self-reported questionnaire to parents /guardians. The examinations were performed by two examiners (Kappa ≥ 0.7). The ETW was registered with modified O´Brien index, reported in percentage and average, confidence interval (CI) 95%. Analysis of association with sex and socioeconomic level were carried out.Results: 614 preschoolers were examined. Prevalence: 57.6% [95%CI=52.7-62.5]. Severe ETW: 8.2% [95%CI 5.5-10.9]. ETW extension: 4.8 [95%CI=4.3-5.3]. The most affected surfaces were palatal upper incisors. Preschoolers of high socioeconomic level presented higher ETW than those of low level; 73.1% (95% CI: 61.9-84.2) and 48.4% (95% CI: 39.2-57.7) respectively (p≤0.01). Conclusion: ETW prevalence and extent was high. These data can contribute to the modification of measures that aim to control ETW prevalence.

Objetivo: determinar prevalência, extensão, severidade e distribuição do desgaste erosivo (DE) em pré-escolares de Montevidéu. Metodologia: estudo transversal de base populacional, amostra representativa de centros educacionais públicos e privados. Aspetos sociodemográficos, biológicos e comportamentais foram investigados por meio de questionário autorreferência pelos pais/responsáveis. Os exames foram realizados por dois operadores Kappa ≥ 0,7. DE foi registado com o Índice O´Brien modificado, relatando porcentagem e média; intervalo de confiança (IC) 95%. Foi realizada análise de associação com sexo e nível socioeconômico. Resultados: 614 pré-escolares foram examinados. Prevalência: 57,6% (IC95%: 52,7-62,5). Extensão: 4,8 (IC 95%: 4,3-5,3). DE grave: 8,2% (IC 95%: 5,5-10,9). As superfícies mais afetadas foram palatinas dos incisivos superiores. Pré-escolares de alto nível socioeconômico apresentaram maior DE que os de baixo nível; 73,1% (IC 95%: 61,9-84,2) e 48,4% (IC 95%: 39,2-57,7) respetivamente (p≤0,01). Conclusões: a prevalência e extensão da DE foi alta. Esses dados podem contribuir em la modificação de medidas que visam controlar a prevalência de DE.

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OBJECTIVE: To estimate the prevalence and distribution of tooth wear among groups of adolescents and adults in Shanghai, China through an epidemiological survey, and explore the associated factors. METHODS: Multistage, stratified, constant volume and cluster sampling methods were used in an epidemiological survey conducted in Shanghai in 2014. The basic erosive wear examination (BEWE) index was used to screen for tooth wear in different age groups: 12 years, 15 years, 18 to 35 years, 36 to 49 years and 50 to 74 years. A previously published questionnaire collected information including dietary habits, oral hygiene habits and general conditions. RESULTS: This survey reports the results for 1806 participants in Shanghai. The prevalence of tooth wear was 59.7% in adolescents (BEWE ≥ 1) and 93.1% in adults (BEWE ≥ 2). The prevalence and severity of disease increased with age (P < 0.01). The teeth most susceptible to wear were the central incisors and first molars. Multivariate analysis of covariance (ANCOVA) results showed that soft drinks, alcoholic drinks, pickled vegetables and hard food, gastroesophageal reflux disease (GERD), xerostomia and poor tooth brushing habits were statistically correlated with tooth wear in different age groups. CONCLUSION: The prevalence of tooth wear appears to be high in adolescents and adults in Shanghai. Frequent consumption of soft or alcoholic drinks, GERD, xerostomia and poor tooth brushing habits were positively associated with tooth wear in different age groups.

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The article presents research in the field of laser cladding of metal-matrix composite (MMC) coatings. Nickel-based superalloys show attractive properties including high tensile strength, fatigue resistance, high-temperature corrosion resistance and toughness, which makes them widely used in the industry. Due to the insufficient wear resistance of nickel-based superalloys, many scientists are investigating the possibility of producing nickel-based superalloys matrix composites. For this study, the powder mixtures of Inconel 625 superalloy with 10, 20 and 40 vol.% of TiC particles were used to produce MMC coatings by laser cladding. The titanium carbides were chosen as reinforcing material due to high thermal stability and hardness. The multi-run coatings were tested using penetrant testing, macroscopic and microscopic observations, microhardness measurements and solid particle erosive test according to ASTM G76-04 standard. The TiC particles partially dissolved in the structure during the laser cladding process, which resulted in titanium and carbon enrichment of the matrix and the occurrence of precipitates formation in the structure. The process parameters and coatings chemical composition variation had an influence on coatings average hardness and erosion rates.

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Basalt fibre is a promising mineral fibre that has high potential to replace synthetic based glass fibre in today's stringent environmental concern. In this study, friction and wear characteristics of glass and basalt fibres reinforced epoxy composites were studied and comparatively evaluated at two test stages. The first stage was conducted at fixed load, speed and distance under three different conditions; adhesive, abrasive and erosive wear, wherein each composite specimens slide against steel, silicon carbide, and sand mixtures, respectively. The second stage was conducted involving different types of adhesive sliding motions against steel counterpart; unidirectional and reciprocating motion, with the former varied at pressure-velocity (PV) factor; 0.23 MPa·m/s and 0.93 MPa·m/s, while the latter varied at counterpart's configuration; ball-on-flat (B-O-F) and cylinder-on-flat (C-O-F). It was found that friction and wear properties of composites are highly dependent on test conditions. Under 10 km test run, Basalt fibre reinforced polymer (BFRP) composite has better wear resistance against erosive sand compared to Glass fibre reinforced polymer (GFRP) composite. In second stage, BFRP composite showed better wear performance than GFRP composite under high PV of unidirectional sliding test and under B-O-F configuration of reciprocating sliding test. BFRP composite also exhibited better friction properties than GFRP composite under C-O-F configuration, although its specific wear rate was lower. In scanning electron microscopy examination, different types of wear mechanisms were revealed in each of the test conducted.

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OBJECTIVES: The objectives of the present study were to assess the consumption of acidic beverages, knowledge and concern about preventing dental erosive wear, and to examine potential associations between these variables, in a sample of high school students. MATERIALS AND METHODS: A survey measuring acidic beverage consumption, knowledge and concern about erosive tooth wear was conducted at 13 high schools in Rogaland county, Norway. RESULTS: Of the 850 students who completed the questionnaire, 26% reported that they drink acidic beverages every day. There were significant gender differences for the consumption of acidic drinks. The survey also demonstrated that a high proportion of students lacks basic knowledge of what erosive tooth wear is, and that this lack of knowledge is associated with a more frequent intake of acidic beverages. However, students who responded that they are concerned about preventing dental erosive wear reported that they drink soft drinks and energy drinks less frequently than students who are not concerned about this. CONCLUSIONS: Results from this study support assumptions about a lack of knowledge about dental erosive wear in youth, and that this lack of knowledge is associated with a more frequent intake of acidic drinks.

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OBJECTIVES: To determine the prevalence, severity and distribution of erosive tooth wear lesions in adult patients at the Universidad de los Andes Health Center in the San Bernardo Metropolitan Region, Chile, during a period of 4 months in 2016. METHODS: A cross-sectional study was conducted. A consecutive sample of patients from 18 to 46 years old who were receiving care at the Universidad de los Andes Health Center during a period from September 2016 to January 2017 was analysed. Basic erosive wear examinations (BEWEs) were performed by two calibrated examiners. RESULTS: A total of 535 adults were included in this study. An erosive tooth wear prevalence of 97.9% was found in which at least one surface had a BEWE score of 2 or 3 as the highest score (98.56% for females and 95.8% for males). In the sample, 75.70% and 74.77% of individuals had at least one surface with a BEWE score of 3 at the second and fifth sextant, respectively. The median of cumulative BEWE scores was 12. The median by individual of the affected percentage of tooth surfaces with BEWE scores 2 or 3 was 19.70%. CONCLUSIONS: We found a high prevalence of erosive tooth wear, mainly in the anterior group of teeth. No differences were found between the sexes, but a positive correlation with age was found. The percentage of surfaces affected was low or moderate.

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High-Cr hypo-eutectic white cast irons are used in very demanding environments that require high resistance to erosive wear. The influence on the microstructural variation and erosive wear resistance of several fundamental factors related to the thermal treatments of these cast irons was analysed by means of a fractional Design of Experiments (DoE). These factors included the ones related to the destabilization of austenite. The precipitated phases were identified by X-ray diffraction (XRD), while the Rietveld structural refinement method was used to determine their percentages by weight. Erosion wear resistance was calculated using the test defined by ASTM G76. It was concluded that the quench cooling medium does not significantly influence either erosive wear resistance or the proportion of martensite or retained austenite. The destabilization temperature is a key factor with respect to the percentage of retained austenite. In order to increase the amount of martensite and decrease the amount of retained austenite, temperatures not exceeding 1000 °C are required. An increase of 100 °C in the destabilization temperature can lead to a 25% increase in retained austenite. Moreover, tempering temperatures of around 500 °C favour an additional increase in the percentage of martensite. Erosive wear commences on the matrix constituent without initially affecting the eutectic carbides. Once the deterioration of the matrix constituent surrounding these carbides occurs, they are released. High tempering times provide an increase in resistance to erosive wear due to a second destabilization of austenite during the said tempering.

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PURPOSE: This questionnaire survey aimed to analyse management strategies for erosive tooth wear and to identify factors influencing dentists' decision-making. MATERIALS AND METHODS: A questionnaire presenting clinical cases with erosive tooth wear on anterior and posterior teeth (BEWE scores 1 to 3) was sent electronically to German dentists (n = 13.683). Statistical analysis was performed by Wilcoxon signed-rank tests, Kruskal-Wallis-tests and Fisher's exact tests (p <0.05). RESULTS: Only 455 dentists (3.3%, mean age: 52.3 ± 9.6) participated. Suggested therapeutic measures were statistically significantly different between BEWE 1, 2 and 3 (p <0.001) and between anterior and posterior teeth with BEWE scores 1 or 2 (p ≤0.025). Initial erosive lesions (BEWE 1) were mainly treated by information about the main causes and/or preventive measures (posterior teeth: 75.6%, anterior teeth: 64.4%), only 20.0% and 31.3% considered restorative treatment for posterior and anterior teeth, respectively. For teeth presenting score 2, a very high proportion of dentists considered restorative treatment (posterior teeth: 60.6%) additionally to prevention, especially when anterior teeth (91.0%) were affected. In case of severe erosive lesions (BEWE 3), the vast majority of dentists considered restorative treatment (posterior teeth: 98.3%, anterior teeth: 99.8%). The decision-making was mainly dependent on the lesion depth, size of affected surfaces and the presence of pain. Fluoride agents and agents containing tin chloride or tin fluoride were most frequently recommended as preventive measures. If distinct defects (BEWE 2) were treated restoratively, mainly composite restorations were performed (posterior teeth: 72.0%, anterior teeth: 90.5%). Severe defects (BEWE 3) were mostly restored with ceramic restorations (posterior teeth: 66.1%, anterior teeth: 66.6%). CONCLUSION: Stepwise management of erosive tooth wear was observed. Dentists' decision-making was related to severity and localisation of erosive tooth wear and to various patient-related factors (e.g. depth of lesion and size of affected surface per tooth).

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INTRODUCTION: Tooth wear is described as loss of hard tooth tissue with no occurrence of dental caries or trauma. Basic Erosive Wear Examination, a new scoring system, is a partial scoring system recording the most severely affected surface in a sextant and the cumulative score guides the management of the condition for the practitioner. The objectives of this study were to determine the prevalence of tooth wear and its association with its risk factors like gender, oral hygiene, diet, general health and life style. METHODS: A cross-sectional study was done in 364 dental patients of Kathmandu Medical College. A questionnaire was filled by interview and Basic Erosive Wear Examination was done. The data so collected were entered in Statistical Package for Social Sciences. Descriptive statistical analysis and Chi-square tests were done at confidence interval of 95% and statistical significance was set at P=0.05. RESULTS: The prevalence of tooth wear was 218 (60.1%) with no significant gender difference. A significant association was observed between tooth wear and age group (P<0.01), duration of brushing (P=0.05), method of brushing (P<0.01), swishing of soft drinks before swallowing (P<0.01) and tobacco chewing (P=0.02). CONCLUSIONS: The prevalence of tooth wear in the study population was high.

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OBJECTIVE: Consumption of acidic food and drinks is considered as important risk factor for development of dental erosion. There are several in vitro and in situ studies focusing on the risk indicators and preventive treatment, however, the need for a standardized animal model has been emphasised for many years. The aim was to establish an animal model of extrinsic dental erosion, which may serve as a standard for future studies to improve our understanding of the erosion. DESIGN: Two acidic drinks, sports drink and cola drink, were given to young mice for six weeks. Experimental and control (water) molars and incisors were dissected out and observed by scanning electron microscopy (SEM). Mandibular first molars were subsequently ground transversely and observed again by SEM. The tooth height and enamel thickness were measured on the SEM images. RESULTS: The lingual surface of the mandibular molars was most eroded after consumption of acidic drinks. The cola drink exhibited higher erosive effect on mandibular molars compared to sports drink. The lingual tooth height, compared to control, was about 34% and 18% lower in the cola drink and sports drink molars, respectively. Compared to the control molars, the lingual enamel was about 23% thinner in the sports drink molars and totally eroded on the certain lingual areas of the cola drink molars. CONCLUSIONS: This new animal model of extrinsic dental erosion and the presented method with ground molars observed in SEM are suitable for further studies, which will gain deeper insights into the erosive disease.

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OBJECTIVE: Palm oil has demonstrated preventive potential against initial erosive demineralization in vitro. This in situ study evaluated the effect of palm oil alone or associated with stannous-containing (Sn) solution on preventing enamel loss from an erosive/abrasive challenge. DESIGN: This single-blind, randomized, crossover in situ/ex vivo study was developed in four phases (one per group of five days) with sixteen volunteers. Enamel blocks (n = 256) were allocated to groups according to the treatment: Palm oil; Palm oil plus Sn solution; Sn solution - positive control; and Deionized water - negative control. Half of the enamel blocks of each group was subjected to erosion and the other half to erosion + abrasion. The daily ex vivo protocol consisted of four citric acid immersions (2 min). Before the first and third acid exposure, the blocks were treated with the test solutions (1 drop/block) for 1 min followed by acid immersion and abrasive challenge (toothpaste was applied on all blocks and half were brushed for 15 s/block). Enamel loss was quantified profilometrically and data were analyzed by two-way ANOVA and Tukey's test (p < 0.05). RESULTS: A significant difference was found for type of treatment (p < 0.001); wear condition (p = 0.38) and the treatment x condition interaction (p = 0.33) was non-significant. Palm oil associated or not to Sn solution significantly reduced enamel wear in comparison with the negative control but did not differ from the positive control (p > 0.05). CONCLUSIONS: Palm oil was able to prevent enamel loss under erosive and erosive + abrasive challenges in a similar extend to stannous-containing commercial solution.

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