Retention force of T-bar clasps for titanium and cobalt-chromium removable partial dentures

The objective of this study was to evaluate the retention force of T-bar clasps made from commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) alloy by the insertion/removal test simulating 5 years use. Thirty-six frameworks were cast from CP Ti (n=18) and Co-Cr alloy (n=18) with identical prefabricated patterns on refractory casts from a distal extension mandibular hemi-arch segment. The castings were made on a vacuum-pressure machine, under vacuum and argon atmosphere. Each group was subdivided in three, corresponding to 0.25 mm, 0.50 mm and 0.75 mm undercuts, respectively. No polishing procedures were performed to ensure uniformity. The specimens were subjected to an insertion/removal test and data was analyzed statistically to compare CP Ti and Co-Cr alloy in the same undercut (Student's t-test for independent samples) and each material in different undercuts (one-way ANOVA) (p=0.05). Comparisons between materials revealed significant differences (p=0.017) only for the 0.50-mm undercut. No significant differences (p>0.05) were found when comparing the same material for the undercuts. It may be concluded that for different undercuts, both Co-Cr alloy and CP Ti had no significant differences for T-bar clasps; CP Ti showed the lowest retention force values when compared to Co-Cr alloy in each undercut, but with significant difference only for the 0.50-mm undercut; and both materials maintained the retentive capacity during the simulation test.O objetivo deste estudo foi avaliar a força de retenção de grampos tipo barra T confeccionados em titânio cp e liga de Co-Cr, através do ensaio de simulação de uso de estruturas metálicas por um período de 5 anos. Sobre modelos de revestimento que simulavam uma extremidade livre unilateral, foram fundidas 36 estruturas em titânio cp (n=18) e em Co-Cr (n=18) utilizando padrões pré-fabricados. As fundições foram feitas em máquina de vácuo-pressão sob vácuo e atmosfera inerte de argônio. Cada grupo foi subdividido em três correspondendo às retenções de 0,25 mm, 0,50 mm e 0,75 mm, respectivamente. Para manter a uniformidade dos grampos, não foram realizados procedimentos de polimento. Os corpos-de-prova foram submetidos ao teste de inserção e remoção e os dados foram analisados estatisticamente (p=0,05) para comparar Ti cp e Co-Cr na mesma retenção (teste T de Student para amostras independentes) e cada material nas diferentes retenções (análise de variância a um fator). A comparação entre os materiais revelou diferença significativa apenas para retenção de 0,50 (p=0,017). Não foram encontradas diferenças quando se comparou o mesmo material nas diferentes retenções (p>0,05). Pode-se concluir que para as diferentes retenções, grampos barra T confeccionados em liga de Co-Cr e titânio não apresentaram diferença estatisticamente significante; o titânio apresentou menores valores de retenção quando comparado à liga de Co-Cr em cada uma das retenções, mas diferença estatisticamente significante só foi encontrada para a retenção 0,50-mm; e ambos materiais mantiveram a capacidade retentiva durante o teste de simulação de uso.FAPES

Effect of fluoride-containing solutions on the surface of cast commercially pure titanium

This study evaluated the effects of fluoride-containing solutions on the surface of commercially pure titanium (CP Ti) obtained by casting. CP Ti specimens were fabricated and randomly assigned to 5 groups (n=10): group 1: stored in distilled water at 37 ± 1ºC; group 2: stored in distilled water at 37 ± 1ºC and daily immersed in 0.05% NaF for 3 min; group 3: stored in distilled water at 37 ± 1ºC and daily immersed in 0.2% NaF for 3 min; group 4: stored in distilled water at 37 ± 1ºC; and immersed in 0.05% NaF every 15 days for 3 min; and group 5: stored in distilled water at 37 ± 1ºC and immersed in 0.2% NaF every 15 days for 3 min. Surface roughness was measured with a profilometer immediately after metallographic polishing of the specimens (T0) and at 15-day intervals until completing 60 days of experiment (T15, T30, T45, T60). Data were analyzed statistically by ANOVA and Tukey's test (α=0.05). There was no statistically significant difference (p>0.05) in surface roughness among the solutions. In conclusion, fluoride-containing solutions (pH 7.0) used as mouthwashes do not damage the surface of cast CP Ti and can be used by patients with titanium-based restorations.Este estudo avaliou o efeito de soluções para enxaguatório bucal contendo fluoreto sobre a superfície do titânio comercialmente puro (cp Ti) após fundição odontológica. As amostras (n=50) foram divididas igualmente: grupo A - armazenadas em água destilada a 37 ± 1ºC, grupo B - armazenadas em água destilada a 37 ± 1ºC e imersão diária em NaF a 0,05% durante 3 min, grupo C - armazenadas em água destilada a 37 ± 1ºC e imersão diária em NaF a 0,2% durante 3 min, grupo D - armazenadas em água destilada a 37 ± 1ºC e imersão em NaF a 0,05% a cada 15 dias por 3 min e grupo E - armazenadas em água destilada a 37 ± 1ºC e imersão em NaF a 0,2% a cada 15 dias durante 3 min. A rugosidade superficial foi medida logo após o polimento metalográfico das amostras (T0) e cada 15 dias de experiência até serem alcançados 60 dias (T15, T30, T45, T60). Os dados foram analisados usando ANOVA (α=0,05) e as diferenças não foram estatisticamente significantes (p>0,05) entre as diferentes soluções. Conclui-se que soluções contendo fluoreto (pH 7,0) não danificam a superfície do Ti cp e podem ser usadas como soluções para bochecho usadas por pacientes que possuem restaurações à base de titânio.FAPES

Classification of gasoline as with or without dispersant and detergent additives using infrared spectroscopy and multivariate classification

AbstractGasoline may contain additives which can minimize the amount of pollutants emitted to the atmosphere. Detergents and dispersants added to gasoline can reduce gas emissions towards atmosphere and the formation of deposits in engines. The Brazilian Agency of Petroleum, Natural Gas and Biofuel (ANP) has established that Brazilian commercial gasoline must contain detergent and dispersant additives, thus requiring the development of methods for their identification in commercial gasoline. This work proposes a methodology which uses infrared spectra in the medium and near region (MIR and NIR) of the residue of distillation for classification of gasoline samples into two groups: with or without detergent/dispersant additives. The performances of three types of classification methods were compared: linear discriminant analysis (LDA), partial least squares discriminant analysis (PLS-DA) and Support Vector Machines (SVM). Different algorithms for selection of spectral variables for LDA were evaluated: stepwise (SW), genetic algorithm (GA) and successive projections algorithm (SPA). The best results were obtained using LDA/GA or SPA/LDA for MIR region

Abrasion wear resistance of different artificial teeth opposed to metal and composite antagonists

One of the most important properties of artificial teeth is the abrasion wear resistance, which is determinant in the maintenance of the rehabilitation's occlusal pattern. OBJECTIVES: This in vitro study aims to evaluate the abrasion wear resistance of 7 brands of artificial teeth opposed to two types of antagonists. MATERIAL AND METHODS: Seven groups were prepared with 12 specimens each (BIOLUX & BL, TRILUX & TR, BLUE DENT & BD, BIOCLER & BC, POSTARIS & PO, ORTHOSIT & OR, GNATHOSTAR & GN), opposed to metallic (M & nickel-chromium alloy), and to composite antagonists (C & Solidex indirect composite). A mechanical loading device was used (240 cycles/min, 4 Hz speed, 10 mm antagonist course). Initial and final contours of each specimen were registered with aid of a profile projector (20x magnification). The linear difference between the two profiles was measured and the registered values were subjected to ANOVA and Tukey's test. RESULTS: Regarding the antagonists, only OR (M = 10.45 ± 1.42 µm and C = 2.77 ± 0.69 µm) and BC (M = 6.70 ± 1.37 µm and C = 4.48 ± 0.80 µm) presented statistically significant differences (p < 0.05). Best results were obtained with PO (C = 2.33 ± 0.91 µm and M = 1.78 ± 0.42 µm), followed by BL (C = 3.70 ± 1.32 µm and M = 3.70 ± 0.61 µm), statistically similar for both antagonists (p>0.05). Greater result variance was obtained with OR, which presented the worse results opposed to Ni-Cr (10.45 ± 1.42 µm), and results similar to the best ones against composite (2.77 ± 0.69 µm). CONCLUSIONS: Within the limitations of this study, it may be concluded that the antagonist material is a factor of major importance to be considered in the choice of the artificial teeth to be used in the prosthesis

Three-dimensional images contribute to the diagnosis of mucous retention cyst in maxillary sinus

Objective: To evaluate the detection of mucous retention cyst of maxillary sinus (MRCMS) using panoramic radiography and cone beam computed tomography (CBCT). Study Design: A digital database with 6,000 panoramic radiographs was reviewed for MRCMS. Suggestive images of MRCMS were detected on 185 radiographs, and patients were located and invited to return for follow-up. Thirty patients returned, and control panoramic radiographs were obtained 6 to 46 months after the initial radiograph. When MRCMS was found on control radiographs, CBCT scans were obtained. Cysts were measured and compared on radiographs and scans. The Wilcoxon, Spearman and Kolmorogov-Smirnov tests were used for statistical analysis. The level of significance was set at 5%. Results: There were statistically significant differences between the two methods (p<0.05): 23 MRCMS detected on panoramic radiographs were confirmed by CBCT, but 5 MRCMS detected on CBCT images had not been identified by panoramic radiography. Eight MRCMS detected on control radiographs were not confirmed by CBCT. MRCMS size differences from initial to control panoramic radiographs and CBCT scans were not statistically significant (p= 0.617 and p= 0.626). The correlation between time and MRCMS size differences was not significant (r = -0.16, p = 0.381). Conclusion: CBCT scanning detect MRCMS more accurately than panoramic radiography

Importance of a distal proximal contact on load transfer by implant-supported single adjacent crowns in posterior region of the mandible: a photoelastic study

OBJECTIVE: This study aimed to evaluate the importance of a distal proximal contact on the load transfer to the posterior region of the mandible by non-splinted adjacent implant-supported crowns using photoelastic stress analysis. MATERIAL AND METHODS: A rectangular model (68x30x15 mm) was made of polymethylmethacrylate resin to simulate half of the mandibular arch. One model was completed with resin replicas representing the first premolar and second molar and with two 3.75 mm dia.x11 mm internal hexagon threaded implants replacing the second premolar and first molar. The other model was manufactured in the same way but without the second molar. Both models were duplicated using photoelastic resin. The roots of the teeth replicas were covered with a layer of polyether impression material to simulate the periodontal ligament. Two different vertical loads were applied to the crowns as follows: 1 - single static point load alternately applied to the crowns replacing the second premolar and first molar (50 N); 2 - simultaneous static point loads applied to both of the crowns replacing the second premolar and first molar (100 N). The resulting isochromatic fringe pattern in the photoelastic model was monitored and photographed. RESULTS: All loading conditions studied showed that the presence of the second molar has changed the load transmission and the pattern of stresses. CONCLUSION: Results showed that the presence of a second molar proximal contact can help minimize the stresses around the implants

Comparative study of two commercially pure titanium casting methods

The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior. OBJECTIVE: This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure. MATERIAL AND METHODS: 72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (&#945;=0.05). RESULTS: Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (

Pacientes víctimas de politrauma con insuficiência renal aguda en la unidad de cuidados intensivos

OBJETIVOS: Identificar as características de pacientes portadores de insuficiência renal aguda (IRA), vítimas de politrauma, internados em uma unidade de terapia intensiva (UTI). MÉTODOS: Foi realizada uma análise retrospectiva de 357 prontuários de portadores de IRA, no período de 2002 a 2003, com creatinina sérica de 1,8 a 4 mg/dl. Destes pacientes internados na UTI, 10,6% eram vítimas de politrauma. RESULTADOS: Dos 38 (10,6%) pacientes portadores de IRA e vítimas de politrauma, 78,9% eram do sexo masculino; 47,3% tinham idade entre 16 e 45 anos; 84,3% apresentaram oligúria; 92,1% não receberam tratamento para IRA durante a internação; 50% permaneceram de um a cinco dias internados na UTI; 47,3% não apresentaram nenhuma doença de base e a mortalidade ocorreu em 50% desta amostra. CONCLUSÃO: Concluiu-se que a monitorização diária da função renal das vítimas de politrauma é um cuidado importante para evitar as complicações da IRA e a respectiva mortalidade.OBJECTIVE: To identify the characteristics of patients with acute renal failure (ARF), polytrauma victims hospitalized in an Intensive Care Unit (ICU). METHODS: A retrospective analysis was performed on 357 records of patients with ARF in the period of 2002 to 2003. These patients presented a creatinine index of 1.8 to 4 mg/dl. Of these patients, 10.6% in the ICU were polytrauma victims. RESULTS: Of the 38 (10.6%) patients with ARF and polytrauma victims, 78.9% of were males; 47.3% were aged between 16 and 45 years; 84.3% presented oliguria; 92.1% received no treatment for ARF during hospitalization; 50% remained from one to five days in the ICU; 47.3% had not presented any underlying disease and mortality occurred in 50%. CONCLUSION: Daily control of the renal function in polytrauma victims is important to prevent ARF complications and consequent mortality.OBJETIVOS: Identificar las características de pacientes portadores de insuficiencia renal aguda (IRA), víctimas de politrauma, internados en una unidad de cuidados intensivos (UCI). MÉTODOS: Se llevó a cabo un análisis retrospectivo de 357 historias clínicas de portadores de IRA, en el período de 2002 a 2003, con creatinina sérica de 1,8 a 4 mg/dl. De estos pacientes internados en la UCI, el 10,6% eram víctimas de politrauma. RESULTADOS: De los 38 (10,6%) pacientes portadores de IRA y víctimas de politrauma, el 78,9% eran del sexo masculino; el 47,3% tenían edades entre 16 y 45 años; el 84,3% presentaron oliguria; el 92,1% no recibieron tratamiento para IRA durante el internamiento; el 50% permanecieron de uno a cinco días internados en la UCI; el 47,3% no presentaron ninguna enfermedad de base y la mortalidad ocurrió en el 50% de esta muestra. CONCLUSIÓN: el monitoreo diario de la función renal de las víctimas de politrauma es un cuidado importante para evitar las complicaciones de la IRA y la respectiva mortalidad