Can brushing with regular and whitening dentifrices influence changes in color and micromorphologic surfaces of ceramic brackets subjected to coffee staining?

The aim of the present study was to evaluate the influence of brushing with regular or whitening dentifrices on the change in color and micromorphologic surface of ceramic orthodontic brackets subjected to coffee staining. Fifty ceramic brackets were subjected to cycles of coffee staining followed by brushing according to the following groups (n = 10): C, control (no brushing); DW, brushing with distilled water; CT, brushing with Colgate Total 12 Clean Mint (regular toothpaste); COW, brushing with Colgate Optic White (containing 1% hydrogen peroxide); and CUWA, brushing with Close-Up White Attraction (containing blue covarine). The color of the brackets was assessed using the Commission Internationale de l'Eclairage (CIE) L*a*b* system at 5 different timepoints: prior to staining (baseline) and after 1, 7, 14, and 21 days of staining and brushing cycles. The surface micromorphology of the brackets was assessed at the baseline timepoint and after 21 days. Kruskal-Wallis, Dunn, Friedman, and Nemenyi tests were applied (α = 0.05) for the statistical analysis. The C group demonstrated a significant reduction in L* and a significant increase in a* and b* values over time. For the DW group, the L* value was reduced but was higher than in the C group, and there were also significant increases in a* and b* from baseline values. A significant increase in the a* and b* values was observed in all groups (P < 0.05). Total color change (∆E*) increased over the period of evaluation for all whitening groups, although only the CT group presented significantly lower ∆E* than the other dentifrices. At the end of the test period, only the COW group exhibited a surface with higher porosity. None of the dentifrices prevented the brackets from staining, but they did reduce the magnitude of color change caused by coffee. The most significant difference was found in the CT group. Micromorphologic surface changes were observed when COW was employed.

Precision and Bias of Target-Controlled Prolonged Propofol Infusion for General Anesthesia and Sedation in Neurosurgical Patients.

The aim of this study was to determine the relationship, precision, and bias of a propofol target-controlled infusion (TCI) system during prolonged infusion in neurosurgical patients. We retrospectively included patients undergoing general anesthesia for elective neurosurgical removal of brain tumors and postoperative sedation in the intensive care unit over a period of 3 months. TCI of propofol (Diprifusor - Marsh model) and remifentanil were used for general anesthesia and sedation. We compared propofol blood concentration (Cmeas ) measured by liquid chromatography-mass spectroscopy with predicted concentrations (Cpred ) by the TCI system at 40 minutes (T0), 2 hours (T1), and 4 hours (T2) and every 8 hours after starting the drug infusion and at the time of emergence from sedation. Ninety-four paired determinations of Cmeas and Cpred from 15 adult ASA I patients (8 men and 7 women 54.9 ± 13 years old; BMI, 24 ± 3.2 kg/m2 ) were analyzed. Mean duration of drug administration was 31 ± 6 hours. The coefficient of determination (R2 ) of the linear regression model for the relationship of Cmeas and Cpred was 0.43. At the time of emergence, Cmeas was 0.5 ± 0.18 µg/mL. The bias of the TCI system (median performance error) was -34.7%, and the precision (median absolute performance error) was 36%. Wobble and divergence were 0.3% and 12.3%, respectively. This study found bias of the system out of the range of tolerability and showed a high tendency toward overestimation. These findings may lead to undersedation when propofol TCI is used for prolonged infusion.

Modeling glucose and free fatty acid kinetics during insulin-modified intravenous glucose tolerance test in healthy humans: role of counterregulatory response.

Insulin administration during insulin-modified intravenous glucose tolerance test (IM-IVGTT) can induce transient hypoglycemia in healthy insulin-sensitive subjects. This triggers counterregulatory reflex (CRR) responses, which influence the kinetics of glucose and nonesterified fatty acids (NEFA), and undermines the accuracy of mathematical modeling methods that do not explicitly account for CRR. The aim of this study is to evaluate mathematical models of glucose and NEFA kinetics against experimental data in the presence or absence of CRR. Thirteen healthy nondiabetic subjects underwent a standard IM-IVGTT and a modified test (GC-IM-IVGTT) with a variable glucose infusion preventing hypoglycemia. While model predictions fit very well with glucose and NEFA data from GC-IM-IVGTT, they lagged behind observations from IM-IVGTT during recovery from hypoglycemia, independently of insulinemia, which did not differ significantly between protocols. A modification to the glucose minimal model, using the glucose concentration below a threshold as a signal for CRR, improves model predictions for both glucose and NEFA. The associated increase in endogenous glucose production correlates, among various CRR hormones, mainly with the dynamics of glucagon concentration. The modified minimal models introduce new parameters that quantify strength and duration of CRR following hypoglycemia. Although CRR represents an unwanted side-effect in IM-IVGTT occurring only in insulin-sensitive subjects, this study provides new insights leading to improved procedures for estimating insulin sensitivity from IM-IVGTT, which may also allow for assessing the individual capacity of recovery from hypoglycemic events in patients treated with insulin or insulin-releasing drugs.

Model-based assessment of insulin sensitivity of glucose disposal and endogenous glucose production from double-tracer oral glucose tolerance test.

A new mathematical model of short-term glucose regulation by insulin is proposed to exploit the oral glucose tolerance test (OGTT), which is commonly used for clinical diagnosis of glucose intolerance and diabetes. Contributions of endogenous and exogenous sources to measured plasma glucose concentrations have been separated by means of additional oral administration and constant intravenous infusion of glucose labeled with two different tracers. Twelve type 2 diabetic patients (7 males and 5 females) and 10 control subjects (5 males and 5 females) with normal glucose tolerance and matched body mass index (BMI) participated in this study. Blood samples for measurement of concentrations/activity of unlabeled and double-tracer glucose and insulin were collected every 15 min for 3 h following the oral glucose load. A minimal model combined with non-linear mixed-effects population parameter estimation has been devised to characterize group-average and between-patient variability of: (i) gastrointestinal glucose absorption; (ii) endogenous glucose production (EGP), and (iii) glucose disposal rate. Results indicate that insulin-independent glucose clearance does not vary significantly with gender or diabetic state and that the latter strongly affects, as expected, insulin-dependent clearance (insulin sensitivity). Inhibition of EGP, interpreted in terms of variations from basal of insulin concentrations, does not appear to be affected by diabetes but rather by BMI, i.e. by the degree of obesity. This study supports the utility of a minimal modelling approach, combined with population parameter estimation, to characterize glucose absorption, production and disposition during double-tracer OGTT experiments. The model provides a means for planning further experiments to validate the new hypothesis on the influence of individual factors, such as BMI and diabetes, on glucose appearance and disappearance, and for designing new simplified clinical tests.

Aspectos socioeconômicos versus hábitos bucais deletérios: análise de uma relação causal / Socioeconomic aspects versus harmful oral habits: analysis of a causal relationship

Os objetivos deste estudo foram averiguar a existência de uma elação causal entre fatores socioeconômicos com a presença de hábitos bucais deletérios, e a percepção dos pais quanto à freqüencia e remoção dos hábitos. Foram entrevistadas, por meio de um questionário semi-estruturado, mães (n=61), cujos filhos ingressaram no Centro de Educação Infantil "Betty Lafer" - Unibes/sp, em 2005. Os dados foram analisados qualitativamente pela análise de conteúdo, por meio da análise de conteúdo, por meio da análise temática categorial e, quantitativamente por intermédio do teste do qui-quadrado. Observou-se uma diferença estatisticamente significante entre a presença de hábito e o gênero (X2= 5,88, p<0,05). Houve maior freqüencia da sucção de chupetas por crianças que não receberam atenção odontológica, e por aquelas cujas mães estudaram até o ensino fundamental. A maioria das crianças portava o hábito uma vez por dia, e os pais salientaram que este deveria cessar no período de um a dois anos de idade. Concluiu-se que houve uma maior prevalência de hábitos no gênero feminino. Quanto às outras variáveis, detectou-se certa influência sobre a incidência de hábitos bucais, entretanto sem relação causal entre ambos.

Amamantamiento versus hábitos bucales deletéreos: ¿existe una relación causal? / Breastfeeding versus harmful oral habits: is there a causal relationship?

Introducción: El amamantamiento materno es una importante fuente de alimentación para el recién nacido, más allá de ser también un estimulante ortopédico natural al crecimiento normal de los maxilares. Objetivos: El trabajo evaluó la percepción de las madres cuanto a la importancia del amamantamiento; hasta qué edad el niño debe ser amamantado naturalmente, e investigar si existe una relación causal de este último con la adquisición de hábitos bucales deletéreos. Resultados: Se observó que el 88,52 por ciento de las madres asociaron el amamantamiento materno a la salud general del niño; y sólo el 1,64 por ciento a la salud bucal. Pese a que un 73,8 por ciento mencionaron que deben amamantar el niño por más de seis meses, conforme preconizado por la OMS/UNICEF (2004), apenas el 54,1 por ciento lo realizan. Se observó una relación de la presencia de hábitos de succión de chupete, aquellos niños en los que el período de amamantamiento materno fue corto, la prueba estadística empleada fue test X-cuadrado (p<0,05). Conclusión: Hay necesidad de difundirse la importancia del amamantamiento en la salud bucal del niño

O aleitamento materno é uma importante fonte de alimentação para o recém nascido, além de ser também um estimulante ortopédico natural ao crescimento normal dos maxilares. O trabalho avaliou a percepção de mães quanto a importância do aleitamento; até que idade a criança deve ser amamentada naturalmente, e investigar se existe uma relação causal deste último com a aquisição de hábitos bucais deletérios. Observou-se que 88,52% das mães associaram o aleitamento materno à saúde geral da criança; e somente 1,64% à saúde bucal. Apesar de 73,8% mencionarem que deve amamentar a criança por mais de 6 meses, conforme preconizado pela OMS/UNICEF, apenas 54,1% a realizam. Observou-se uma relação da presença de hábito de sucção de chupeta, àquelas crianças em que o período de aleitamento foi curto, a prova estatística empregada foi o teste qui-quadrado (p<0,05). Conclui-se que há necessidade de divulgação da importância do aleitamento na saúde bucal da criança.

Introduction: The Breastfeeding is an important nutrition source for the newborn, besides being also a natural orthopedic stimulant to the regular growth of maxillaries. Objective: The study evaluated the mothers perception about the importance of the breastfeeding; the maximum age that child should be naturally breastfeed, and to verify if there is an association between breastfeeding and malloclusion habits. Results: I was observed that 88.52% of the mothers associated breastfeeding to the health for the child; and only 1.64% to the oral health. Despite 73.8% mentioned they that should breastfeed the child for more than 6 months, according to WHO/UNICEF in 2004, only 54.1% did it. There was relationship between the presence of pacifiers and the short in time of breastfeeding, according to the qui-square test (p <0,05). Conclusion: There is a necessity of popularization of the importance of maternal breastfeeding for the child' oral health.

Modeling population kinetics of free fatty acids in isolated rat hepatocytes using Markov Chain Monte Carlo.

The aim of this study is the characterization, by means of mathematical models, of the activity of isolated hepatic rat cells as regards the conversion of free fatty acids (FFA) to ketone bodies (KB). A new physiologically based compartmental model of FFA metabolism is used within a context of population pharmacokinetics. This analysis is based on a hierarchical model, that differs from standard model formulations, to account for the fact that some data sets belong to the same animal but have been collected under different experimental conditions. The statistical inference problem has been addressed within a Bayesian context and solved by using Markov Chain Monte Carlo (MCMC) simulation. The results obtained in this study indicate that, although hormones epinephrine and insulin are important metabolic regulatory factors in vivo, the conversion of FFA to KB by isolated hepatic rat cells is not significantly affected by epinephrine and only little influenced by insulin. So we conclude that in vivo, the interaction of these two hormones with other compounds not considered in this study plays a fundamental role in ketogenesis. From this study it appears that mathematical models of metabolic processes can be successfully employed in population kinetic studies using MCMC methods.