Effect of Water and Chlorhexidine with Different Pressures of Oral Irrigation Device on the Surface Roughness and Topography of Giomer

Abstract Objective: To evaluate the effect of different pressures of an oral irrigation device (OID) and the irrigation solution type on the surface roughness of the giomer restorative material. Material and Methods: In this in vitro study, disk-shaped giomer samples were fabricated and assigned to 5 groups (n=23): Group 1, storage in distilled water (control); Group 2, OID #7 pressure/ water; Group 3, OID #10 pressure/ water; Group 4, OID #7 pressure/ 0.05% CHX; Group 5, OID #10 pressure/ 0.05% CHX. The samples' treatment simulated a one-year application of OID. Surface roughness (Ra) and topography of the giomer were evaluated using profilometry and scanning electron microscopy. The data were analyzed with Paired t-test, Tukey, and ANOVA tests (α=0.05). Results: The Ra of the samples increased significantly after treatment with OID (p<0.001). The roughness increase in groups with a pressure of 10 was higher than those with a pressure of 7 (p<0.001). The effect of pressure on surface changes was significant (p<0.001). However, the solution type and the cumulative effect of these two factors were insignificant (p=0.08 and p=0.43, respectively). Conclusion: Oral irrigation device with both solutions significantly increased the surface roughness and topographic changes of the giomer. The severity of these changes was related to the device's pressure.

Avaliação in vitro da microdureza e porosidade de duas resinas compostas fotopolimerizáveis / Evaluación in vitro de la microdureza y porosidad de dos resinas compuestas fotopolimerizables / In vitro evaluation of the microhardness and porosity of two photopolymerizable composite resins

RESUMO Introdução: Os estudos científicos acerca das propriedades físicas e mecânicas apresentadas pelas resinas compostas são cada vez mais necessários diante da grande variedade de produtos disponíveis no mercado atual, resultante do aumento de sua demanda dentro da odontologia que preza por preparos minimamente invasivos com a devolução das características estéticas e funcionais do elemento dentário. Objetivo: Avaliar e comparar a microdureza e porosidade das resinas compostas fotopolimerizavéis Filtek Z350 XT 3M e Zirconfill Technew. Métodos: Foram confeccionados 10 corpos de prova por amostra (n= 10) submetidos a teste microdureza Vickers e porosidade por microtomografia computadorizada. Resultados: Com relação à presença de porosidades, dada em porcentagem, o grupo da Filtek apresentou os menores valores médios. Quando comparado estatisticamente, os grupos apresentaram diferença estatística (p= 0,019), com uma magnitude de efeito alta. Com relação aos valores de microdureza, o grupo da Filtek apresentou os maiores valores médios. Quando comparados estatisticamente, os grupos não apresentaram diferença estatística (p > 0,05). Conclusões: A porosidade foi significativamente diferente entre os grupos estudados, sendo o grupo Filtek Z350XT de menor percentual. No entanto, os grupos não apresentaram diferença estatística para microdureza, apesar do grupo Filtek Z350XT ter apresentado maior valor médio(AU)

RESUMEN Introducción: Los estudios científicos sobre las propiedades físicas y mecánicas presentadas por las resinas compuestas son cada vez más necesarios ante la gran variedad de productos disponibles en el mercado actual, resultante del aumento de su demanda dentro de la odontología que aprecia por preparaciones mínimamente invasivas con la devolución de las características estéticas y funcionales del elemento dental. Objetivo: Evaluar y comparar la microdureza y porosidad de las resinas compuestas fotopolimerizables Filtek Z350 XT 3M y Zirconfill Technew. Métodos: Se han confeccionado 10 cuerpos de prueba por muestra (n= 10) sometidos a prueba de microdureza Vickers y porosidad por microtomografía computarizada. Resultados: Con respecto a la presencia de porosidades, dada en porcentaje, el grupo de Filtek presentó los menores valores medios. Cuando se comparó estadísticamente, los grupos presentaron una diferencia estadística (p= 0,019), con una magnitud de efecto alto. Con respecto a los valores de microdureza, el grupo de Filtek presentó los mayores valores medios. Cuando se comparó estadísticamente, los grupos no presentaron una diferencia estadística (p> 0,05). Conclusiones: La porosidad fue significativamente diferente entre los grupos estudiados, siendo el grupo Filtek Z350XT de menor porcentaje. Sin embargo, los grupos no presentaron diferencia estadística para microdureza, a pesar de que el grupo Filtek Z350XT presentó un valor medio más alto(AU)

ABSTRACT Introduction: Scientific studies about the physical and mechanical properties of composite resins are increasingly needed in view of the wide variety of products available in the market today, resulting from the increase in their demand for dental care purposes, with a preference for minimally invasive preparations aimed at restoring the esthetic and functional characteristics of the treated element. Objective: Evaluate and compare the microhardness and porosity of the photopolymerizable composite resins Filtek Z350 XT and Zirconfill Technew. Methods: Ten test bodies were developed per sample (n= 10) and subjected to Vickers microhardness and porosity testing by computerized microtomography. Results: With respect to the presence of porosity, expressed in percentages, the Filtek group had the lowest mean values. When compared statistically, the two groups showed a statistical difference (p= 0.019) with a high effect magnitude. Regarding microhardness, the Filtek group had the highest mean values. Statistical comparison did not find any difference between the groups (p> 0.05). Conclusions: Porosity was significantly different in the groups studied, the Filtek Z350XT group exhibiting the lowest percentage. However, the groups did not show any statistical difference concerning microhardness, despite the fact that the Filtek Z350XT group had a higher mean value(AU)

Use of Direct Liver Stiffness Measurement in Evaluating the Severity of Liver Cirrhosis in Patients with Hepatocellular Carcinoma.

BACKGROUND: Severity of liver cirrhosis plays an important role in determining the safe extents of hepatectomy in patients with hepatocellular carcinoma (HCC). The aim of this study was to investigate whether direct liver stiffness measurement can help surgeons to evaluate the severity of liver cirrhosis in HCC patients. METHODS: Overall, 119 HCC patients who underwent open hepatectomy were retrospectively studied. The severity of liver cirrhosis was histologically staged using the Laennec staging system. Direct liver stiffness measurement was performed during operation using a sclerometer device named LX-C Shaw hardmeter, and its efficacy in assessing the severity of liver cirrhosis was compared with that of transient elastography (TE) and cirrhotic severity scoring (CSS) previously proposed by our team. RESULTS: Liver stiffness measured by LX-C Shaw hardmeter was significantly correlated with the severity of liver cirrhosis. Spearman correlation coefficients for the correlation between the severity of liver cirrhosis and direct liver stiffness measurement, TE, and CSS were 0.751, 0.454, and 0.705, respectively (all P < 0.001). The areas under the receiver operating characteristic curves (AUCs) of direct liver stiffness measurement were 0.891 for moderate cirrhosis and 0.944 for severe cirrhosis and superior to those of TE (0.735 and 0.776, respectively) and CSS (0.888 and 0.905, respectively). CONCLUSIONS: Direct liver stiffness measurement is a useful method in evaluating the severity of liver cirrhosis in HCC patients.

Microhardness distribution of the tibial diaphysis and test site selection for reference point indentation technique.

Indentation hardness test is a good in vitro method of bone quality assessment. The purpose of this study is to explore the distribution characteristics of bone tissue microhardness in tibial diaphysis and provide theoretical support for the test site selection of the reference point indentation technique.Three fresh right tibias were obtained from 3 cadaver donors. The tibial diaphysis was evenly divided into 6 sections. Bone specimens with a thickness of 3 mm were cut from each part. After appropriate management, micro-indentation tests were performed in various regions of the specimens to acquire the microhardness values of the tibial diaphysis. Statistical analysis was performed by randomized block design variance analysis to study the distribution characteristics of bone microhardness.72 regions were selected for 360 effective indentations. We found that the bone microhardness is inhomogeneous in tibia diaphysis. Mean hardness value of the anterior, medial, posterior, lateral region of tibia diaphysis was 45.58 ±â€Š4.39 Vickers hardness (HV), 52.33 ±â€Š3.93 HV, 54.00 ±â€Š4.21 HV, 52.89 ±â€Š4.44 HV, respectively. The anterior cortex exhibits lower microhardness value than the other regions (P < .001). Within the same region, microhardness varies significantly with positions in the tibial diaphysis. The variations in indentation hardness are bound to have a significant impact on the comparability of different reference point indentation (RPI) studies.The results of this study indicated the regional microhardness difference in the human tibia diaphysis. The microhardness of different planes in the same region is also inconsistent. Inhomogeneous distribution of indentation microhardness would have considerable influence in the test site selection of RPI technique. The data collected in our study would contribute to the design of highly precise 3D printing implants and bionic bones with gradient elastic modulus.

The Impact of Radiotherapy in the in Vitro Remineralization of Demineralized Enamel

Objective: To evaluate the impact of radiotherapy on enamel around restorations of glass ionomer cement (GIC) and fluoride tooth paste (FTP). Material and Methods: Eighty enamel blocks were made and randomly distributed into two groups, according to the fluoride therapy, non-fluoride tooth paste (NFTP) and FTP (n=40) and in subgroups in conformity with radiation dose (0, 10, 30 and 60 Gy). Roughness and microhardness enamel analyses were conducted before radiotherapy. Enamel cavities were made and restored with two GIC (Ketac Molar Easy Mix or Vitremer). Enamel blocks were submitted to 10, 30 and 60 Gy. Then, artificial enamel caries lesions were created by a pH-cycling procedure and FTP or NFTP were used as treatment. The restored enamel blocks were submitted to final roughness and microhardness analyses. Roughness increase (ΔR) and hardness loss (ΔH) values of enamel were submitted to ANOVA and Tukey test (p=0.05). Results: The irradiated enamel group showed statistically higher ΔR (0.44 ±0.2) and ΔH (99.26±7.0) values compared to non-irradiated group (ΔR = 0.051±0.02; ΔH=66.16±12.7) when a resin-modified GIC and NFTP were used. Conclusion: Higher radiation dose increased dissolution of bovine enamel. The use of GIC associated with FTP decreased roughness and increased enamel hardness after radiotherapy.

Human cancellous bone mechanical properties and penetrator geometry in nanoindentation tests.

PURPOSE: The goal of the study was to determine the influence of the penetrator geometry on the human cancellous bone mechanical properties in indentation tests. The aim of this research was also the assessment of the material properties of bone structures, having in mind the energy aspects of the curve obtained in the cycle: inelastic loading and elastic unloading. METHODS: The samples were resected from a femoral heads of patients qualified for a hip replacement surgery. During the Depth Sensing Indentation tests, hardness and elastic modulus of the cancellous bone tissue were measured using the spherical and Vickers penetrators. Measurements were made in a node and in a trabecula for each sample. RESULTS: The analysis of the measurement results and the calculations of total energy, i.e., elastic and inelastic, and those of the parameters of hardness and elasticity made it possible to assess the influence of the penetrator geometry on the mechanical properties of bone structures at a microscopic level. CONCLUSIONS: It was found, with respect to the methodology of indenta- tion, that without determining the shape of the penetrator and the site of the indentation, an objective assessment of the micro mechanical properties of the tested material is not possible.

Truncated Hollow Cone Probe for Assessing Transepidermal Water Loss and Skin Hardness.

This study proposes a skin analysis device using a truncate hollow cone (THC) probe for measuring both transepidermal water loss (TEWL) and skin hardness. Because skin health is closely related to the epidermal barrier function and skin mechanical property, it is important to measure their biophysical indicators at the same time, to understand skin conditions and diagnose skin disorders such as atopic dermatitis and systemic sclerosis. Previous skin analyzers, however, required different probes with different protocols for each biophysical indicators, which makes the measurement inconvenient and increases the measurement uncertainty. The present device consists of a THC probe equipped with humidity and force sensors, and an actuator that simultaneously measure both TEWL and skin hardness which indicate the integrity of the epidermal barrier function and the skin mechanical property, respectively. Using artificial reference skins, the prototype device showed the TEWL with a sensitivity and linearity of 0.011 (%/s)/(g/m2/h) and 99.5%, and the hardness with 0.075 N/(Shore 00) and 97.6%, respectively, which are within the appropriate range for the properties of human skin. The on-body measurement of five subjects showed that the proposed device could measure both the TEWL and skin hardness without any crosstalk from each other. The proposed device has great potential for in-depth analysis of the health status of the skin which could indicate various skin diseases.

Erosive potential of sports beverages on human enamel "in vitro" / Potencial erosivo de bebidas esportivas no esmalte humano "in vitro" / Potencial erosivo de bebidas deportivas en el esmalte humano "in vitro"

INTRODUCTION: The low pH of sports drinks may cause tooth enamel demineralization. Objective: To measure Vickers hardness of human enamel exposed to sports drinks. METHODS: Human molars were used to collect the enamel samples. Each sample had a test surface (exposed to the drinks) and a control surface (unexposed). The samples were exposed to isotonic drinks Gatorade and Powerade, and to maltodextrin drinks Malto Advanced and Malto Active, for 10 minutes every 12 hours over 30 days. The Vickers microhardness test was conducted with three indentations on each surface. The mean of the indentations within each group was considered in the statistical analysis. Sports drinks variables were analyzed with ANOVA/Tukey (p≤0.01). The independent t-test was used in the comparison between the control and test surfaces of each drink (p ≤ 0.05). RESULTS: Enamel exposure to Gatorade (p = 0.000) Malto Advanced (p = 0.000) and Malto Active (p = 0.000) was seen to significantly reduce microhardness, while the isotonic drink Powerade had no significant effect on enamel (p = 0.248). CONCLUSION: It was concluded that with the exception of the isotonic drink Powerade, all the sports drinks tested caused a reduction in the microhardness of human enamel. Evidence Level III; Therapeutic studies - Investigating the Results of Treatment.

INTRODUÇÃO: O baixo pH de bebidas esportivas pode promover perda mineral do esmalte dental. OBJETIVO: Avaliar a microdureza Vickers do esmalte humano exposto a bebidas esportivas. MÉTODOS: Dentes molares humanos foram usados para coletar as amostras de esmalte. Cada amostra apresentou uma superfície de teste (exposta às bebidas) e uma superfície de controle (não exposta). As amostras foram expostas aos isotônicos Gatorade e Powerade e às maltodextrinas Advanced Series e Malto Active durante 10 minutos de 12/12 horas, durante 30 dias. O teste de microdureza Vickers foi realizado com três indentações em cada superfície. Na análise estatística, foi considerada a média das indentações dentro de cada grupo. As variáveis bebidas esportivas foram avaliadas com ANOVA/Tukey (p ≤ 0,01). Na comparação entre a superfície controle e teste de cada bebida foi utilizado o Teste t para amostras independentes (p ≤ 0,05). RESULTADO: Observou-se que a exposição do esmalte a Gatorade (p = 0,000), Malto Advanced (p = 0,000) e Malto Active (p = 0,000) reduz significativamente a microdureza, enquanto que o isotônico Powerade não produziu efeito significativo sobre o esmalte (p = 0,248). CONCLUSÃO: Concluiu-se que com exceção do isotônico Powerade, todas as bebidas esportivas testadas provocaram redução na microdureza do esmalte dental humano. Nível de Evidência III; Estudos terapêuticos ­ investiga o resultado de um tratamento.

INTRODUCCIÓN: El bajo pH de bebidas deportivas puede favorecer la pérdida mineral del esmalte dental. OBJETIVO: Evaluar el esmalte dureza Vickers humano expuesto a las bebidas deportivas. MÉTODOS: Se utilizaron los dientes molares para la toma de las muestras de esmalte. Cada muestra tenía una superficie de prueba (expuestos a las bebidas) y una superficie de control (no ex-puesta). Las muestras fueron expuestas en isotónica Gatorade y Powerade, y maltodextrinas, y la serie Advanced activo Malto durante 10 minutos 12/12 horas durante 30 días. La prueba de dureza Vickers se realizó con tres muescas en cada superficie. El análisis estadístico fue la media de las muescas dentro de cada grupo. variables de bebidas deportivas se analizaron con ANOVA / Tukey (p≤0,01). La comparación entre la superficie de control y prueba de cada bebida se utilizó la prueba t para muestras independientes (p ≤ 0,05). RESULTADOS: Se observó que la exposición del esmalte Gatorade (p = 0,000) Malto avanzada (p = 0,000) y Malto activo (p = 0,000) reduce significativamente la dureza, mientras que Powerade isotónica ningún efecto significativo sobre el esmalte (p = 0,248). CONCLUSIÓN: Se concluye que con la excepción de Powerade isotónica, todas las bebidas deportivas probados causó una reducción en la dureza del esmalte humano. Nivel de Evidencia; Estudios terapéuticos - Investigación de los resultados del tratamento.

Milk Reverts the Effects of an Enamel Erosive but Healthy Diet

Objective: To determine the erosive effects of popular fruits and vegetables on enamel, and the potential counter effects of milks. Material and Methods: Ten popular fruits and vegetables were individually blended in a juicer to form a fruit or vegetable juice. The labial surfaces (three for each treatment group) were then immersed for thirty minutes in a fresh juice of one of ten products: strawberry, spinach, pineapple, grapefruit, green pepper, pickle, orange, apple, tomato, and carrot. In a second experiment, human enamel was treated with Coca-Cola for 30 minutes, followed by a variety of milks: Skim, 2%, Whole, Chocolate, Lactaid, Almond, and Silk Soy. Three teeth were used for each treatments and enamel microhardness of each sample was measured at baseline, after erosive exposure, and after the 30-minute variable treatment. Results: All fruits and vegetables showed differences between the pre- and posttreatment microhardness values. For the second experiment, tested milks result in significant increases (p<0.05) in enamel microhardness. Paired-t test was used for all comparisons. A thirty-minute exposure to the juices of all fruits and vegetables examined in the study significantly changed the microhardness of enamel, with grapefruit and pickle having potentially the most erosive effect on enamel. Diets that are high in fruits and vegetables can predispose to enamel erosion. For the second experiment, filtered water, ACT fluoride rinse, and varying milks all result in remineralization of enamel. Conclusion: Eroded enamel exposed to milk demonstrated a significant greater gain of enamel microhardness as compared to filtered water.

Assessment of Enamel Surface Microhardness with different Fluoride Varnishes-An In Vitro Study.

AIM: This study aimed to assess the microhardness of the enamel surface after fluoride varnish application. MATERIALS AND METHODS: Thymol of 0.1% in distilled water was used to store the collected healthy sixty teeth. The samples were divided into three groups randomly as per the different applica -tion of fluoride varnish. Group A: Fluor protector varnish (FIV) application, group B: Duraphat varnish application and group C: Bifluorid 10 varnish application. The present study followed the pH cycling protocol. Microhardness tester was used to test the microhardness of enamel surface and was expressed as micro-hardness measurements of Vickers hardness number (VHN) which was performed at baseline, on the 3rd day andon 7th day. RESULTS: At baseline, group A samples mean SMH value was 230.64 ± 12.32 which was slightly more than group B with 229.45 ± 10.22 and group C with 230.10 ± 11.45. There was no significant difference showed with the analysis of variance between the groups. On the 3rd day, there was a slight increase in the mean SMH in group A with 235.39 ± 6.44 and no significant difference between the groups was seen statistically. On the 7th day, the group A showed high SMH value of 262.20 ± 4.89 compared to other groups which didn't show a significantly high statistical difference. CONCLUSION: On conclusion, post-application of fluorprotector varnish showed higher enamel surface microhardness compared to Duraphat and Bifluorid 10 varnishes. CLINICAL SIGNIFICANCE: In young children, fluoride varnishes are effectively used as a noninvasive, anti-caries agent in the treatment of initial caries. Therefore, in routine dental practice, the knowledge about different fluoride varnishes is of importance.

Studying Hardness Meter Spring Strength to Understand Hardness Distribution on Body Surfaces.

INTRODUCTION: For developing a hardness multipoint measurement system for understanding hardness distribution on biological body surfaces, we investigated the spring strength of the contact portion main axis of a biological tissue hardness meter (product name: PEK). METHODS: We measured the hardness of three-layered sheets of six types of gel sheets (90 mm × 60 mm × 6 mm) constituting the acupuncture practice pads, with PEK measurements of 1.96 N, 2.94 N, 3.92 N, 4.90 N, 5.88 N, 6.86 N, 7.84 N, 8.82 N, and 9.81 N of the main axis spring strength. We obtained measurements 10 times for the gel sheets and simultaneously measured the load using a digital scale. We measured the hardness distribution of induration embedded and breast cancer palpation models, with a main axis with 1.96 N, 4.90 N, and 9.81 N spring strengths, to create a two-dimensional Contour Fill Chart. RESULTS: Using 4.90 N spring strength, we could obtain measurement loads of ≤3.0 N, and the mean hardness was 5.14 mm. This was close to the median of the total measurement range 0.0-10.0 mm, making the measurement range the largest for this spring strength. We could image the induration of the induration-embedded model regardless of the spring strength. CONCLUSION: Overall, 4.90 N spring strength was best suited for imaging cancer in the breast cancer palpation model.

The influence of the cumulated deformation energy in the measurement by the DSI method on the selected mechanical properties of bone tissues.

PURPOSE: The goal of the study was to determine the influence of DSI test conditions, i.e., loading/unloading rates, hold time, and the value of the maximum loading force on selected mechanical properties of trabecular bone tissue. METHODS: The test samples were resected from a femoral head of a patient qualified for a hip replacement surgery. During the DSI tests hardness (HV, HM, HIT) and elastic modulus (EIT) of trabecular bone tissue were measured using the Micro Hardness Tester (MHT, CSEM). RESULTS: The analysis of the results of measurements and the calculations of total energy, i.e., elastic and inelastic (Wtotal, Welastic, Winelastic) and those of hardness and elasticity made it possible to assess the impact of the process parameters (loading velocity, force and hold time) on mechanical properties of bone structures at a microscopic level. CONCLUSIONS: The coefficient k dependent on the EIT/HIT ratio and on the stored energy (ΔW = Wtotal - Welastic) is a measure of the material reaction to the loading and the deformation of tissue.

Experimental testing and constitutive modeling of the mechanical properties of the swine skin tissue.

PURPOSE: The aim of the study was an estimation of the possibility of using hyperelastic material models to fit experimental data obtained in the tensile test for the swine skin tissue. METHODS: The uniaxial tensile tests of samples taken from the abdomen and back of a pig was carried out. The mechanical properties of the skin such as the mean Young's modulus, the mean maximum stress and the mean maximum elongation were calculated. The experimental data have been used to identify the parameters in specific strain-energy functions given in seven constitutive models of hyperelastic materials: neo-Hookean, Mooney-Rivlin, Ogden, Yeoh, Martins, Humphrey and Veronda-Westmann. An analysis of errors in fitting of theoretical and experimental data was done. RESULTS: Comparison of load -displacement curves for the back and abdomen regions of skin taken showed a different scope of both the mean maximum loading forces and the mean maximum elongation. Samples which have been prepared from the abdominal area had lower values of the mean maximum load compared to samples from the spine area. The reverse trend was observed during the analysis of the values of elongation. An analysis of the accuracy of model fitting to the experimental data showed that, the least accurate were the model of neo- -Hookean, model of Mooney-Rivlin for the abdominal region and model of Veronda-Westmann for the spine region. CONCLUSIONS: An analysis of seven hyperelastic material models showed good correlations between the experimental and the theoretical data for five models.

A Simulation of the Viscoelastic Behaviour of Heel Pad During Weight-Bearing Activities of Daily Living.

Internal strain is known to be one of the contributors to plantar soft tissue damage. However, due to challenges related to measurement techniques, there is a paucity of research investigating the strain within the plantar soft tissue during daily weight-bearing activities. Therefore, the main aim of this study was to develop a non-invasive method for predicting heel pad strain during loading. An ultrasound indentation technique along with a mathematical model was employed to calculate visco-hyperelastic structural coefficients from the results of cyclic-dynamic indentation and stress-relaxation tests. Subject-specific structural coefficients of heel pads were calculated from twenty participants along with the assessment of plantar pressure. The average difference between the predicted and the measured force during the cyclic-dynamic indentation test was only 5.8%. Moreover, the average difference between the predicted and the in vivo strain during walking was 14%. No statistically significant correlation was observed between maximum strain and peak plantar pressure during walking; indicating that the measurement of strain along with plantar pressure can improve our understanding of the mechanical behaviour of the plantar soft tissue.

Evaluación de la microdureza superficial de resinascompuestas: revisión de la literatura / Evaluation of the surface microhardness of composite resins: literature review

En la actualidad, ha aumentado considerablemente el uso de resinas compuestas, llegando a convertirse en el principal material restaurador utilizado por los odontólogos, tanto para el sector anterior como el posterior. Dentro de sus propiedades, encontramos la dureza, la cual forma parte muy importante para determinar su durabilidad en boca. Esta propiedad está determinada por la cantidad de relleno que presente la resina, por ende, a mayor cantidad de relleno, mayor será su dureza y menores cambios dimensionales. A pesar de todas las mejoras en tecnología y propiedades de las resinas compuestas, aún no se encuentra un material que posea características ideales que lo hagan indestructible al paso de los años. El objetivo de este artículo es revisar las principales características de las resinas compuestas, especialmente la microdureza superficial. La dureza es una condición de la superficie de un material determinado, no representa ninguna propiedad de la materia y está relacionada con las propiedades elásticas y plásticas de cada material. Existen en la actualidad muchos sistemas para medir la dureza, por ejemplo, sistema Brinell, Rockwell, Vickers y Knoop

At present, the use of composite resins has increased considerably, becoming the main restorative material used by dentists, both for the anterior and posterior sectors. Among its properties, we find the hardness, which is a very important part to determine its durability in the mouth. This property is determined by the amount of filler that the resin presents, therefore, the greater the amount of filler, the greater its hardness and smaller dimensional changes. Despite all the improvements in technology and properties of composite resins, there is still no material that has ideal characteristics that make it indestructible over the years. The objective of this article is to review the main characteristics of composite resins, especially surface microhardness. Hardness is a condition of the surface of a given material, it does not represent any property of the material and is related to the elastic and plastic properties of each material. There are currently many systems to measure hardness, for example, Brinell, Rockwell, Vickers and Knoop systems.

Strength of Occipital Hair as an Explanation for Pilonidal Sinus Disease Caused by Intruding Hair.

BACKGROUND: Pilonidal sinus disease is thought to be caused by intrusion of hair into healthy skin; loose hair in the intergluteal fold is thought to promote disease. However, compelling evidence to support these postulates is lacking; the cause of pilonidal sinus disease remains uncertain. OBJECTIVE: To determine whether particular properties of hair are associated with susceptibility to pilonidal sinus disease, we compared physical properties of hairs of patients with pilonidal sinus disease with hairs from control subjects who were matched for sex, BMI, and age. DESIGN: This was an experimental study with establishment of a mechanical strength test for single hairs to quantify the maximum vertical force that a hair could exert, following tests of strength of occipital, lumbar, and intergluteal hair. SETTINGS: Hair from patients with pilonidal sinus disease and matched control subjects were harvested from patients of the St. Marienhospital Vechta Department of Procto-Surgery. PATIENTS: A total of 17 adult patients with pilonidal sinus disease and 217 control subjects were included. MAIN OUTCOME MEASURES: ANOVA and intraclass and interclass variations of data gained from mechanical strength tests of occipital, lumbar, and intergluteal hair were included. RESULTS: Vertical hair strength was significantly greater in patients with pilonidal sinus disease. Occipital hair exhibited 20% greater, glabella sacralis 1.1 times greater, and intergluteal hair 2 times greater strength in patients with pilonidal sinus disease than in matched control subjects (all p = 0.0001). In addition, patients with pilonidal sinus disease presented with significantly more hair at the glabella sacralis and in the intergluteal fold. LIMITATIONS: The study was limited by its relatively small number of patients from a specific cohort of European patients. CONCLUSIONS: Occipital hair exhibited considerable vertical strength. Because occipital hair exerted the greatest force and cut hair fragments were found in the pilonidal nest in large quantities, these data suggest that pilonidal sinus disease is promoted by occipital hair. See Video Abstract at http://links.lww.com/DCR/A435.

A comparison of impact force reduction by polymer materials used for mouthguard fabrication.

PURPOSE: The essential function of mouthguards is protection against the effects of injuries sustained during sports activities. This purpose will be successfully achieved if appropriate materials ensuring sufficient reduction of the injury force are used for mouthguard fabrication. OBJECTIVE: The objective of the study was to investigate the force reduction capability of selected materials as well as to identify which material reduces the impact force to the highest degree. METHODS: The material for the study were samples of polymers (6 samples in total), obtained during the process of deep pressing (2 samples), flasking (3 samples) and thermal injection (1 sample), which were tested for impact force damping using an impact device - Charpy impact hammer. The control group comprised of the ceramic material samples subjected to the hammer impact. The statistical analysis applied in this study were one-way Welch ANOVA with post-hoc Games-Howell pairwise comparisons. RESULTS: The test materials reduced the impact force of the impact hammer to varying degrees. The greatest damping capability was demonstrated for the following materials: Impak with 1:1 powder-to-liquid weight ratio polymerized with the conventional flasking technique, and Corflex Orthodontic used in the thermal injection technique of mouthguard fabrication. CONCLUSIONS: Impak with 1:1 weight ratio and Corflex Orthodontic should be recommended for the fabrication of mouthguards since they demonstrated the most advantageous damping properties.

Assessing degradation of composite resin cements during artificial aging by Martens hardness.

BACKGROUND: Aim of the study was to verify the efficiency of Martens hardness measurements in detecting the degradation of composite resin cements during artificial aging. METHODS: Four cements were used: Variolink II (VL2), RelyX Unicem 2 Automix (RUN), PermaFlo DC (PDC), and DuoCem (DCM). Specimens for Martens hardness measurements were light-cured and stored in water at 37 °C for 1 day to allow complete polymerization (baseline). Subsequently the specimens were artificially aged by water storage at 37 °C or thermal cycling (n = 6). Hardness was measured at baseline as well as after 1, 4, 9 and 16 days of aging. Specimens for indirect tensile strength measurements were produced in a similar manner. Indirect tensile strength was measured at baseline and after 16 days of aging (n = 10). The results were statistically analyzed using one-way ANOVA (α = 0.05). RESULTS: After water storage for 16 days hardness was significantly reduced for VL2, RUN and DCM while hardness of PDC as well as indirect tensile strength of all cements were not significantly affected. Thermal cycling significantly reduced both, hardness and indirect tensile strength for all cements. No general correlation was found between Martens hardness and indirect tensile strength. However, when each material was analyzed separately, relative change of hardness and of indirect tensile strength revealed a strong linear correlation. CONCLUSIONS: Martens hardness is a sensible test method to assess aging of resin composite cements during thermal cycling that is easy to perform.

Novel intraoperative use of the "Tensipresser" to assess factors predictive of pancreatic fistula after pancreaticoduodenectomy.

PURPOSES: Pancreatic fistula (PF) is a challenging complication of pancreaticoduodenectomy (PD). 'Soft pancreas' is reported as a risk factor for PF; however, palpation by the surgeon is not an objective method of evaluating pancreatic texture. We conducted this study to investigate whether a texture analyzer called a "Tensipresser" can be used to quantify pancreatic tissue hardness and predict the development of postoperative PF. METHODS: We assessed pancreatic texture in 85 patients who underwent PD. After surgeons assessed the texture of the pancreas subjectively, the physical properties were measured on the pancreatic margin intraoperatively, by the two-bite method using the "Tensipresser". The incidence and severity of PF were based on the definitions of the International Study Group on Pancreatic Fistula. RESULTS: Symptomatic PF (grade B and C) developed in 16% of the patients. Patients were divided into two groups based on the Tensipresser measurement: those with a soft and fragile pancreas with hardness < 2070 gw/cm2 and cohesiveness < 0.65 (SF group); and all other patients (non-SF group). In the univariate and multivariate analysis, a small pancreatic duct diameter (<4 mm), no conduction of preoperative chemoradiation therapy, and inclusion in the SF group were significant predictors of PF. CONCLUSION: The Tensipresser can evaluate pancreatic texture objectively, helping to define intraoperatively, those at risk of the development of PF.

Tissue Deformation Index as a Reliable Measure of Lateral Abdominal Muscle Activation on M-Mode Sonography.

The aim of this article is to present a novel method of evaluating the activity of lateral abdominal muscles using M-mode sonography. The method leads to calculation of the tissue deformation index, representing the percent change in lateral abdominal muscle thickness over time. The objectives of this study were as follows: (1) to establish the mean tissue deformation index values for individual lateral abdominal muscles; and (2) to establish the reliability of the tissue deformation index. In a group of 34 healthy young volunteers (mean age, 24.03 years; body mass, 68.89 kg; body height, 174.25 cm), the reflex response of the lateral abdominal muscles to postural perturbation in the form of rapid arm abduction was recorded in 2 series, with 6 repetitions each, and the tissue deformation index was calculated. The mean tissue deformation index values formed a gradient, increasing from deep to superficial lateral abdominal muscles: 0.06%/ms for transversus abdominis, 0.11%/ms for oblique internal, and 0.16 for oblique external muscles. The tissue deformation index values differed significantly among individual lateral abdominal muscles (all paired comparisons, P < .001). Three repeated measurements are sufficient to achieve good intra-rater reliability of the tissue deformation index (intraclass correlation coefficient, > 0.8).