Preparation and quantitative characterization of polydimethylsiloxane optical phantoms with zinc-phthalocyanine dye absorbers

We described a method for the preparation of polydimethylsiloxane (PDMS) phantoms to mimic the optical properties of biologic tissues at distinct wavelengths ranging from the visible to the near-infrared spectra. The present method for fabricating solid optical tissue phantoms using zinc-phthalocyanine chromophores has demonstrated high photostability with optical absorption coefficients up to 1.0  mm^-1, making this phantom proper with absorption bands ranging from 600 to 850 nm. It also happens that the chromophore absorption coefficient is linear as a function of its concentration inside the previous optical window. The optical scattering properties were quantitatively selected by adding TiO₂ particle concentrations to the PDMS phantom. Thus, the quantitative optical properties of absorption and scattering for a large-batch fabrication were demonstrated, making the zinc-phthalocyanine phantoms suitable for use as a reference standard.

Effect of Different Adhesive Systems Used for Immediate Dentin Sealing on Bond Strength of a Self-Adhesive Resin Cement to Dentin

OBJECTIVE

The purpose of this study was to investigate the immediate and three-month water storage behavior of adhesives when used for immediate dentin sealing (IDS).

METHODS AND MATERIALS

Four adhesive systems were used to perform IDS: a one-step self-etch (Xeno V), a two-step self-etch (Clearfil SE Bond), a two-step etch-and-rinse (XP Bond), and a three-step etch-and-rinse (Optibond FL). For the control group, IDS was not performed. The self-adhesive resin cement RelyX Unicem was used for the luting procedures. After seven days of water storage, specimens (n=6) were sectioned into beams (n=5) with an approximately 1-mm² cross-sectional area. Half of the specimens were tested in tension after seven days of water storage at 37°C, while the other half was stored for three months prior to testing in tension using a universal testing machine (1 mm/min). The failure pattern was determined using a stereomicroscope and scanning electron microscopy. Microtensile bond strength (μTBS) data were statistically analyzed by two-way analysis of variance and Tukey post hoc test (α=0.05).

RESULTS

After seven days, the control group presented the lowest μTBS but did not differ from XP Bond and Clearfil SE Bond. After three months, there was no μTBS difference between the IDS groups and the control.

CONCLUSIONS

After seven days of water storage, the groups with IDS presented higher μTBS values than the control group, although XP Bond and Clearfil SE Bond did not present significant differences. However, after three months of storage in water, IDS groups did not differ significantly from control group, which did not receive IDS.

Circulating levels of adiponectin and extent of coronary artery disease in patients undergoing elective coronary angiography

Adiponectin (APN), an adipose tissue-released adipokine with demonstrated anti-inflammatory and anti-atherogenic properties, is encoded by a gene whose polymorphisms are associated with presence of coronary artery disease (CAD). Serum APN levels are inversely related with presence and complexity of CAD. Within this context, we sought to compare levels of total APN and its high molecular weight form (HMW APN) according to clinical presentation and extent of CAD in patients undergoing elective cardiac catheterization. From March 2008 to June 2010, clinical data and blood samples for APN and HMW APN measurements were collected from 415 subjects undergoing cardiac catheterization at two tertiary centers. CAD extent was estimated by the number of coronary arteries with significant stenosis (≥70% obstruction in a major coronary artery) and by Duke Jeopardy Score (DJS). Serum APN levels were similar between groups with stable or unstable CAD (APN 9.20±5.88 vs 9.47±6.23 μg/mL, P=0.738, and HMW APN 5.31±3.72 vs 5.91±4.16 μg/mL, P=0.255), even after stratification by the number of arteries involved (single-vessel vs multivessel disease: APN 9.39±5.76 vs 9.26±6.27 μg/mL, P=0.871; HMW APN 5.29±3.79 vs 5.83±4.04 μg/mL, P=0.306) and DJS score (APN, P=0.718; HMW APN, P=0.276). We conclude that APN and HMW APN serum levels are similar across clinical presentations and different extents of CAD, despite being significantly lower in the presence of obstructive CAD.

Effects of Immediate Dentin Sealing and Pulpal Pressure on Resin Cement Bond Strength and Nanoleakage

Objective: The object of this study was to evaluate the simulated pulpal pressure (SPP) and immediate dentin sealing technique (IDS) effects on the microtensile bond strength (μTBS) and nanoleakage of interfaces produced by different luting agents.

Methods and Materials: Two self-adhesive luting agents (RelyX Unicem [UC] and Clearfil SA Luting [SA]) and two conventional luting agents (Rely X ARC [RX] and Panavia F [PF]) were evaluated. Eighty human molars were divided in four groups according to luting agents. Each group was subdivided according to SPP (with or without) and dentin sealing (immediate or delayed) using Clearfil SE Bond (n=5). After IDS was performed, specimens were stored in water for seven days before luting procedures. Composite blocks were luted according to the manufacturers' instructions. One half of the specimens were subjected to 15 cm H2O of hydrostatic pressure for 24 hours before cementation procedures and continued for 24 hours afterward. Then, restored teeth were sectioned into beams and tested in tension. Two additional teeth per group were prepared for nanoleakage evaluation with scanning electron microscopy. Bond strength data were statistically analyzed by three-way analysis of variance and Tukey test.

Results: μTBS of RX decreased when it was subjected to SPP without IDS. However, in the same conditions, μTBS of UC increased. The IDS prevented negative influence of SPP on μTBS of RX and PF; however, a decrease in μTBS of SA and UC was observed. Except for RX, IDS increased μTBS for all resin cements.

Conclusion: Independent of SPP, the IDS technique obtained higher μTBS for PF, SA, and UC and did not influence RX μTBS.

Two-year Randomized Clinical Trial of Self-etching Adhesives and Selective Enamel Etching

OBJECTIVE

The aim of this randomized, controlled prospective clinical trial was to evaluate the clinical effectiveness of restoring noncarious cervical lesions with two self-etching adhesive systems applied with or without selective enamel etching.

METHODS

A one-step self-etching adhesive (Xeno V(+)) and a two-step self-etching system (Clearfil SE Bond) were used. The effectiveness of phosphoric acid selective etching of enamel margins was also evaluated. Fifty-six cavities were restored with each adhesive system and divided into two subgroups (n=28; etch and non-etch). All 112 cavities were restored with the nanohybrid composite Esthet.X HD. The clinical effectiveness of restorations was recorded in terms of retention, marginal integrity, marginal staining, caries recurrence, and postoperative sensitivity after 3, 6, 12, 18, and 24 months (modified United States Public Health Service).

RESULTS

The Friedman test detected significant differences only after 18 months for marginal staining in the groups Clearfil SE non-etch (p=0.009) and Xeno V(+) etch (p=0.004). One restoration was lost during the trial (Xeno V(+) etch; p>0.05).

CONCLUSIONS

Although an increase in marginal staining was recorded for groups Clearfil SE non-etch and Xeno V(+) etch, the clinical effectiveness of restorations was considered acceptable for the single-step and two-step self-etching systems with or without selective enamel etching in this 24-month clinical trial.

Assessment of the hemodynamic profile in periodontal tissues of diabetic subjects with periodontitis by optical spectroscopy

BACKGROUND AND OBJECTIVE

The influence of diabetes mellitus (DM) on the hemodynamics of periodontal tissues has not been assessed previously. The primary objective of this study was to validate optical spectroscopy as a periodontal diagnostic tool for subjects with type 2 DM and chronic periodontitis.

MATERIAL AND METHODS

Using a portable optical near-infrared spectrometer, optical spectra were obtained from healthy (n = 127), gingivitis (n = 115), and periodontitis (n = 109) sites of 65 subjects with type 2 DM and chronic periodontitis. Healthy (n = 65) sites of 15 nondiabetic subjects without periodontitis were used as controls. A modified Beer-Lambert unmixing model that incorporates a nonparametric scattering-loss function was used to determine the relative contribution of deoxygenated hemoglobin and oxygenated hemoglobin (HbO2 ) to the overall spectrum. The balance between tissue oxygen delivery and oxygen utilization in periodontal tissues was assessed.

RESULTS

In diabetic subjects, tissue oxygen saturation and HbO2 concentration were significantly decreased in the periodontitis sites (p < 0.01) compared with the healthy and gingivitis sites. Furthermore, tissue oxygenation in healthy sites of control subjects was significantly higher than that in sites of diabetic subjects (p < 0.01).

CONCLUSION

In summary, the results of this study suggest that optical spectroscopy can monitor the hemodynamic profile in diabetic subjects with chronic periodontitis. Furthermore, healthy sites of diabetic subjects presented lower tissue oxygenation than did those of nondiabetic subjects.

Effect of Simulated Tooth Temperature on the Degree of Conversion of Self-adhesive Resin Cements Exposed to Different Curing Conditions

Objectives

This study evaluated the degree of conversion (DC) of two commercial, self-adhesive resin cements (SARCs) using Fourier transform infrared analysis (FTIR) polymerized at simulated prepared tooth surface temperatures and under different curing conditions.

Materials and Methods

RelyX U100 (U100, 3M ESPE) and Maxcem Elite (MX, Kerr Corporation) were mixed at 25°C and applied to the surface of a horizontal attenuated total reflectance (ATR) unit, which was near room temperature (RT, control) (25°C) or heated to simulate prepared tooth surface temperatures (28°C and 32°C) and then attached to an infrared spectrometer. The products were polymerized using one of three conditions: direct light exposure through a glass slide (DLE), exposure through a 1.5-mm thick ceramic disc overlay (CO) (A2 shade, IPS e.max, Ivoclar Vivadent), or self-curing (SC). FTIR spectra were recorded for 12 minutes (1 spectrum/s, 16 scans/spectrum, resolution 4 cm−1) immediately after application to the ATR. The DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios before and 12 minutes after curing, as well as during each 1-second interval. DC data (n=7) were analyzed by two-way analysis of variance and Tukey's post-hoc test (p=0.05).

Results

Both simulated tooth temperatures significantly increased DC in all groups of MX and in the CO and SC groups of U100 compared with the RT control. For MX, the self-cure groups exposed to tooth temperatures showed DC values similar to those of the CO groups. For U100, the CO groups showed higher DC values than SC groups regardless of temperature. Time-based conversion profiles ranged according to product, temperature, and curing mode.

Conclusions

Causing SARCs to polymerize at simulated tooth temperatures increases DC of SARCs compared with room-temperature curing values, mainly in the SC mode.

Effect of long-term simulated pulpal pressure on the bond strength and nanoleakage of resin-luting agents with different bonding strategies

This study evaluated the effects of simulated hydrostatic pulpal pressure (SPP) on the microtensile bond strength (μTBS) to dentin and nanoleakage patterns produced by self-adhesive luting agents after 12 months. Three self-adhesive luting agents (RelyX Unicem [UN], RelyX U100 [UC], and Clearfil SA Luting [SA]) and three conventional luting agents (Rely X ARC [RX], Panavia F [PF], and a two-step self-etching adhesive system [Clearfil SE Bond] associated with Panavia F [PS]) were evaluated. One hundred twenty-three human molars were abraded to expose occlusal surfaces. Resin cements were used to lute cylindrical composite blocks to the teeth either subjected or not to SPP. Sixty specimens were subjected to 15 cm H2O of SPP for 24 hours before and 24 hours or 12 months after cementation procedures. Afterward, restored teeth were serially sectioned into beams with a cross-sectional area of 1 mm(2) at the bonded interface and were tested in tension (cross-head speed of 1 mm/min). Failure mode was determined using scanning electron microscopy (SEM). Data were statistically analyzed by three-way analysis of variance and post hoc Tukey test (p=0.05). Two additional teeth in each group were serially sectioned into 0.9-mm-thick slabs, which were submitted to a nanoleakage protocol with AgNO3 and analyzed with scanning and transmission electron microscopes. The μTBS values of the etch-and-rinse group (RX) were negatively influenced by SPP and long-term water storage with SPP. After 12 months, UC and SA presented premature failures in all specimens when submitted to SPP. SPP increased silver deposition in most groups in both evaluation times. The hydrostatic pulpal pressure effect was material dependent. The storage time without SPP did not affect bond strength. However, long-term SPP influenced the performance of the etch-and-rinse and self-adhesive cements regarding μTBS and nanoleakage pattern, except to UN.

Allelic variations of the vitamin D receptor (VDR) gene are associated with increased risk of coronary artery disease in type 2 diabetics: the DIABHYCAR prospective study

AIM

Vitamin D deficiency is associated with coronary artery disease (CAD), and the actions of vitamin D are mediated by binding to a specific nuclear vitamin D receptor (VDR). This study investigated the associations of VDR gene variants with CAD in two cohorts of type 2 diabetes patients.

METHODS

A cohort of 3137 subjects from the prospective DIABHYCAR study (CAD incidence: 14.8%; follow-up: 4.4 ± 1.3 years) and an independent, hospital-based population of 713 subjects, 32.3% of whom had CAD, were assessed. Three SNPs in the VDR gene were genotyped: rs1544410 (BsmI); rs7975232 (ApaI); and rs731236 (TaqI).

RESULTS

In the DIABHYCAR cohort, an association was observed between the A allele of BsmI and incident cases of CAD (HR: 1.16, 95% CI: 1.05-1.29; P = 0.002). Associations were also observed between BsmI (P = 0.01) and TaqI (P = 0.04) alleles and baseline cases of CAD. The AAC haplotype (BsmI/ApaI/TaqI) was significantly associated with an increased CAD prevalence at the end of the study compared with the GCT haplotype (OR: 1.12, 95% CI: 1.02-1.28; P = 0.04). In a cross-sectional study of the independent hospital-based cohort, associations of ApaI (P = 0.009) and TaqI (P = 0.03) alleles with CAD were observed, with similar haplotype results (OR: 1.33, 95% CI: 1.03-1.73; P = 0.03).

CONCLUSION

The haplotype comprising the minor allele of BsmI, major allele of ApaI and minor allele of TaqI of VDR (AAC) was associated with an increased risk of CAD in type 2 diabetes patients. This effect was independent of the effects of other known cardiovascular risk factors.

Decreased insulin secretion and increased risk of type 2 diabetes associated with allelic variations of the WFS1 gene: the Data from Epidemiological Study on the Insulin Resistance Syndrome (DESIR) prospective study

AIMS/HYPOTHESIS

We investigated associations of allelic variations in the WFS1 gene with insulin secretion and risk of type 2 diabetes in a general population prospective study.

METHODS

We studied 5,110 unrelated French men and women who participated in the prospective Data from Epidemiological Study on the Insulin Resistance Syndrome (DESIR) study. Additional cross-sectional analyses were performed on 4,472 French individuals with type 2 diabetes and 3,065 controls. Three single nucleotide polymorphisms (SNPs) were genotyped: rs10010131, rs1801213/rs7672995 and rs734312.

RESULTS

We observed statistically significant associations between the major alleles of the three variants and prevalent type 2 diabetes in the DESIR cohort at baseline. Cox analyses showed an association between the G-allele of rs10010131 and incident type 2 diabetes (HR 1.34, 95% CI 1.08-1.70, p = 0.007). Similar results were observed for the G-allele of rs1801213 and the A-allele of rs734312. The GGA haplotype was associated with an increased risk of diabetes as compared with the ACG haplotype (HR 1.26, 95% CI 1.04-1.42, p = 0.02). We also observed statistically significant associations of the three SNPs with plasma glucose, HbA(1c) levels and insulin secretion at baseline and throughout the study in individuals with type 2 diabetes or at risk of developing diabetes. However, no association was observed in those who remained normoglycaemic at the end of the follow-up. Associations between the three variants and type 2 diabetes were replicated in cross-sectional studies of type 2 diabetic patients in comparison with a non-diabetic control group.

CONCLUSIONS/INTERPRETATION

The most frequent haplotype at the haplotype block containing the WFS1 gene modulated insulin secretion and was associated with an increased risk of type 2 diabetes.

Antibacterial Activity of Various Self-etching Adhesive Systems Against Oral Streptococci

An antimicrobial effect is desired for adhesive systems in order to avoid cariogenic bacterial colonization and also the growth of remaining bacteria in the cavity preparation.

In vivo preservation of the hybrid layer by chlorhexidine

Host-derived proteases have been reported to degrade the collagen matrix of incompletely-resin-infiltrated dentin. This study tested the hypothesis that interfacial degradation of resin-dentin bonds may be prevented or delayed by the application of chlorhexidine (CHX), a matrix metalloproteinase inhibitor, to dentin after phosphoric acid-etching. Contralateral pairs of resin-bonded Class I restorations in non-carious third molars were kept under intra-oral function for 14 months. Preservation of resin-dentin bonds was assessed by microtensile bond strength tests and TEM examination. In vivo bond strength remained stable in the CHX-treated specimens, while bond strength decreased significantly in control teeth. Resin-infiltrated dentin in CHX-treated specimens exhibited normal structural integrity of the collagen network. Conversely, progressive disintegration of the fibrillar network was identified in control specimens. Auto-degradation of collagen matrices can occur in resin-infiltrated dentin, but may be prevented by the application of a synthetic protease inhibitor, such as chlorhexidine.

Interfacial ultramorphology of single-step adhesives: nanoleakage as a function of time

The aim of this study was to examine the effectiveness of single-step self-etching adhesives in preventing nanoleakage over a 90-day water-storage period, and analyse the ultramorphological characteristics of resin-dentin interfaces. Three single-step self-etching adhesives were evaluated: Adper Prompt L-Pop - LP (3M ESPE), iBond - iB (Heraeus Kulzer), and Clearfil Tri-S Bond - S3 (Kuraray). Bonded specimens were sectioned into 0.9-mm thick slabs and stored in water for 1, 60 or 90 days. After the storage periods, a silver tracer solution was used to reveal nanometer-sized spaces and evidence of degradation within resin-dentin interfaces. Epoxy resin-embedded sections were prepared, and the interfaces observed with the TEM. Nanoleakage patterns were compared among adhesives and storage periods using image analysis software. Data were statistically analysed by two-way anova and Tukey test. Nanoleakage was observed in all resin-dentin interfaces produced by the single-step self-etching adhesives. Results showed that LP presented the lowest silver deposition means at 1 day. However, after 60 and 90 days, the area of silver deposition significantly increased for LP. iB presented intense silver deposition after 1 day and a small increase after 90 days. S3 presented the lowest silver deposition means after 60 and 90 days of water-storage.

The Ala45Thr polymorphism of NEUROD1 is associated with type 1 diabetes in Brazilian women

BACKGROUND

NEUROD1 encodes a transcription factor expressed in the endocrine pancreas, and involved in beta-cell development, function and mechanisms of apoptosis. In this study, we investigated the association of a frequent polymorphism in exon 2 of NEUROD1 (G > A; Ala45Thr) with Type 1 diabetes in Brazilian subjects.

METHODS

A population/association study comprising 246 unrelated Type 1 diabetic and 275 nondiabetic white Brazilian subjects. The Ala45Thr variant was genotyped by a PCR-RFLP method.

RESULTS

The frequency of the Thr allele was significantly higher in patients with Type 1 diabetes than in controls (42.3% vs 35.3%, P=0.02). Stratification by gender showed that homozygosity for the Thr allele was associated with Type 1 diabetes in women with odds ratio of 3.66 (95% C.I. 1.43-10.11, P=0.009) as compared to homozygosity for the Ala allele. This effect was not observed in men.

CONCLUSIONS

We found a gender-specific association of the Ala45Thr variant of NEUROD1 with Type 1 diabetes in Brazilian women. Our results suggest that gender as well as ethnicity might modulate the association of NEUROD1 with Type 1 diabetes.

Vitamin D endocrine system and the genetic susceptibility to diabetes, obesity and vascular disease. A review of evidence

The Vitamin D endocrine system regulates multiple aspects of calcium metabolism and cellular differentiation and replication in the immune system, endocrine pancreas, liver, skeletal muscles and adipocytes. It plays an important role in glucose homeostasis, notably, in the mechanism of insulin release. Actions of vitamin D are mediated by the binding of 1, 25-(OH)2D3 to a specific cytosolic/nuclear vitamin D receptor (VDR), a member of the steroid/thyroid hormone receptor superfamily. Several frequent polymorphisms are found in the VDR gene and were reported to be associated with a variety of physiological and pathological phenotypes in many populations. In this paper, we will review the evidences suggesting associations of allelic variations in the VDR gene and phenotypes related to body weight, glucose homeostasis, diabetes and its vascular complications.

The Gly482Ser polymorphism in the peroxisome proliferator-activated receptor-gamma coactivator-1 gene is associated with hypertension in type 2 diabetic men

AIMS/HYPOTHESIS

Peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) acts as a cofactor for several nuclear hormone receptors in many tissues and organs implicated in blood pressure regulation. Here, we assessed the association between the Gly482Ser variant of PPARGC1 and the arterial hypertension frequently found in subjects with type 2 diabetes.

METHODS

We studied a group of 479 men and 253 women with type 2 diabetes. Arterial hypertension was present in 70% of the men and in 73% of the women. Genotypes were examined by PCR restriction fragment length polymorphism. A logistic regression analysis was performed to assess the covariables associated with arterial hypertension.

RESULTS

There was an association between Ser allele homozygosis and arterial hypertension in type 2 diabetic men (odds ratio of 2.52 vs Gly allele homozygosis; 95% CI: 1.32-5.00; p=0.0064), but not in women. The prevalence of arterial hypertension in type 2 diabetic men was 77% vs 73% vs 67% for Ser-Ser, Gly-Ser and Gly-Gly carriers respectively (p=0.021). Age, BMI, the use of insulin, and triglyceride and creatinine levels were also independently associated with arterial hypertension in this cohort.

CONCLUSIONS/INTERPRETATION

We have observed a sex-specific association between the PPARGC-1 gene Gly482Ser polymorphism and arterial hypertension in type 2 diabetic men. Further studies are needed to investigate the genetic, biochemical and pathophysiological basis of this allelic association.

Allelic variation in exon 18 of the sulfonylurea receptor 1 (SUR1) gene, insulin secretion and insulin sensitivity in nondiabetic relatives of type 2 diabetic subjects

BACKGROUND

We have previously observed associations of the T-allele of the exon 18 variant (ACC --> ACT; Thr759Thr) of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus (T2DM). Here we assess beta-cell function and insulin sensitivity in carriers of different genotypes at this locus.

METHODS

Pre-hepatic insulin secretion rates (ISR) derived by deconvolution of circulating C-peptide levels, and glucose clearance were assessed during graded infusions of intravenous glucose in CC-homozygous (n=6) and CT-heterozygous (n=6) nondiabetic relatives of CT-heterozygous type 2 diabetic subjects.

RESULTS

Average ISR over the duration of the study, adjusted for sex, age, BMI and prevailing glucose levels, were lower in CT-heterozygous subjects as compared with CC-homozygous subjects (3.91 +/- 0.40 vs. 4.84 +/- 0.28 pmol/kg x min(-1); p=0.048). The correlation curves relating ISR to glucose levels were significantly different in the two groups (analyses of covariance p=0.029). Glucose clearance was similar in both groups.

CONCLUSIONS

Insulin secretion rates, but not insulin sensitivity, assessed during graded infusion of glucose were mildly decreased in nondiabetic relatives of type 2 diabetic subjects, who carry the at risk T-allele of exon 18 variant of the SUR1 gene. These results suggest that the at-risk allele might have a small effect on pancreatic B-cell function and contribute to the development of T2DM in these families.

Sulfonylurea receptor -1 (SUR1): genetic and metabolic evidences for a role in the susceptibility to type 2 diabetes mellitus

The pancreatic B-cell ATP-sensitive potassium channel (K(ATP)) is composed of two distinct subunits, an inwardly rectifying ion channel forming the pore (Kir6.2), and a regulatory subunit, namely the sulfonylurea receptor-1 (SUR1), which binds this widely used class of insulin-secreting drugs. Mutations in the genes encoding Kir6.2 and SUR1 may result in familial persistent hyperinsulinemic hypoglycaemia of infancy, demonstrating their role in the regulation of insulin secretion. Studies in various populations with different ethnic background provided evidence that various alleles of single nucleotide polymorphisms (SNPs) in the SUR1 gene, and to a less extent in the Kir6.2 gene, confer a significantly increased risk for the development of type 2 diabetes mellitus (T2DM). Allelic variations of these SNPs were shown to modulate insulin secretion and insulin sensitivity in vivo, thus providing a pathophysiological background to explain their contribution to the genetic susceptibility to T2DM. The aim of this review is to summarise and discuss the significant results of recent literature on the implication of K(ATP), and particularly of SUR1, in the genetic and pathopysiological mechanisms of T2DM.

The effect of elapsed time following bleaching on enamel bond strength of resin composite

Recent studies have concluded that carbamide peroxide bleaching agents significantly affect the bond strength of composite to bleached enamel. This study evaluated the effects of bleaching regimen with different carbamide peroxide concentrations and post-treatment times on composite bond strength to enamel. Two hundred and four flat buccal and lingual enamel surfaces obtained from erupted sound third molars were randomly divided into 17 groups (n = 12). Sixteen experimental groups comprised the evaluation of four carbamide peroxide home bleaching agents (Opalescence 10%-20% and Whiteness 10%-16%) and four time intervals after bleaching (one day, one, two and three weeks). Specimens of control group were not submitted to bleaching and were stored in artificial saliva at 37 degrees C for 10 days. The specimens of experimental groups were exposed to one daily application of carbamide peroxide for six hours for 10 consecutive days. After each daily treatment and post-bleaching, the specimens were stored in artificial saliva solution. Bonds were formed with Scotchbond MP and Z-100 composite resin, and shear bond test was carried out 24 hours after adhesive-composite application. Two-way ANOVA showed that the bond strengths were significantly different (p < 0.05). For the first two weeks post-bleaching, the bond strengths of resin to enamel were low. After a lapse of three weeks, the bond strength returned to that of the untreated control group. Increased concentration did not prolong the time needed prior to bonding.

Vitamin D receptor gene polymorphisms are associated with obesity in type 2 diabetic subjects with early age of onset

OBJECTIVE

Allelic variations in the vitamin D receptor (VDR) gene were reported to modulate insulin secretion in response to glucose. VDR was investigated as a candidate gene for type 2 diabetes mellitus (T2DM).

METHOD

Four single nucleotide polymorphisms (SNPs) in intron 8 (BsmI, Tru9I, ApaI) and exon 9 (TaqI) of the VDR gene were examined in 309 unrelated French subjects with T2DM and 143 controls.

RESULTS

The distribution of alleles and genotypes of the four SNPs was similar in patients and controls. However, in patients whose age at diagnosis of diabetes was < or =45 years, homozygous subjects for the T-allele of the TaqI SNP had a higher body mass index (BMI) (31.7+/-6.7 kg/m2, P=0.0058) and an increased prevalence of obesity (81%, P=0.005) with respect to heterozygous subjects (27.9+/-5.0 kg/m2; 46%) or homozygous subjects for the t-allele (27.7+/-5.0 kg/m2; 52%). Similar results were observed for homozygous subjects for the b-allele of the BsmI SNP. Logistic regression analysis demonstrated that TT homozygosity was independently associated with obesity in these subjects (odds ratio, 4.64; 95% confidence interval (CI), 1.64-14.76; P=0.0056).

CONCLUSION

VDR is not a major gene for T2DM in French Caucasians. However, polymorphisms in the VDR gene are associated with the susceptibility to obesity in subjects with early-onset T2DM. The pathophysiological mechanisms of these associations remain unexplained, but they could be related to a direct effect of vitamin D in adypocyte differentiation and metabolism, or to an indirect effect by modulation of insulin secretion.

Mutations in the insulin promoter factor-1 gene in late-onset type 2 diabetes mellitus

OBJECTIVE

Insulin promoter factor-1 (IPF-1) is a transcription factor expressed in pancreatic beta cells. Following the identification of missense variants in the coding regions of the IPF-1 gene, in subjects selected for a strong family history of type 2 diabetes, the aim of our study was to evaluate the prevalence of these variants in the common form of type 2 diabetes.

METHODS

Three variants (C18R, Q59L and D76N) were screened by PCR-RFLP in a group of 296 unrelated French late-onset type 2 diabetic subjects consecutively recruited in a diabetes department of a university hospital, regardless of family history of diabetes.

RESULTS

The C18R and Q59L variants were each found in 0.37% of the diabetic patients, and in none of 147 controls. We did not detect the D76N variant, which was the most frequent variant in subjects with a strong family history of diabetes, in patients or controls.

CONCLUSIONS

We have observed a combined prevalence of missense variants in the coding region of the IPF-1 gene of around 1%, in unselected patients with the common form of late-onset type 2 diabetes. The prevalence of these variants in subjects with a strong family history of type 2 diabetes had been found to be as high as approximately 6%. These differences in prevalence might be related to differences in the clinical profile of patients, such as age of onset of diabetes and associated obesity, as well as a family history of diabetes.

Association of a variant in exon 31 of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus in French Caucasians

The sulfonylurea receptor (SUR1) of the pancreatic beta-cell ATP-sensitive potassium channel plays a key role in glucose-induced insulin secretion. The A-allele of a single nucleotide polymorphism (SNP) in exon 31 of the SUR1 gene (AGG-->AGA; Arg1273Arg) has previously been shown to be associated with hyperinsulinemia in nondiabetic Mexican-American subjects. Here, we have investigated the association of this SNP with type 2 diabetes mellitus (T2DM) in French Caucasian subjects. We have observed an increased frequency of the A allele (37.1% vs 27.6%, P=0.0048; odds ratio 1.54), of the AA genotype (15.7% vs 9.8%; P=0.025), and of the combined AA/AG genotypes (58.5% vs 45.5%, P=0.0098; odds ratio 1.69) in patients compared with controls. This association is stronger in the subgroup of patients with age of diagnosis of diabetes equal to or less than 45 years: A allele 43.2% (P=0.0003 compared with controls; odds ratio 1.99), AA genotype 21.4% (P=0.0032), and combined AA/AG genotypes 65.1% (P=0.0022; odds ratio 2.23). Unexpectedly, the G allele is strongly associated with arterial hypertension in obese diabetic subjects (GG vs AA odds ratio 19.97). In conclusion, we have observed an association of an SNP in exon 31 of the SUR1 gene with T2DM. These data reinforce the hypothesis that insulin secretion defects in T2DM might be at least partially related to allelic variations in the SUR1 gene.

Identification of a novel Tru9 I polymorphism in the human vitamin D receptor gene

We found a novel Tru9 I restriction polymorphism in intron 8 of the vitamin D receptor (VDR) gene in healthy French Caucasians. It corresponds to a substitution of A for G at nucleotide +443 bp from the end of exon 8. The allelic frequency of G and A in 151 unrelated subjects was 0.894 and 0.106, respectively. This polymorphism is located in the reverse primer binding site of primers that have been frequently used in the literature to genotype a BsmI restriction polymorphism. The presence of the Tru9I A allele may result in allele drop-out when the BsmI restriction fragment length polymorphism (RFLP) is genotyped with the original set of primers. This novel Tru9I polymorphism may be useful for analysis of the VDR gene.

[Assessment of quality of obstetric hospital care: use of corticoid in preterm labor]

This study aimed to assess quality of obstetric care for preterm labor patients, using referents, indicators, and standards derived from scientific evidence, focusing on antenatal corticotherapy. Available meta-analyses and randomized controlled trials were examined to establish referents, defining indicators and estimating process and outcome standards for the present study. Data from hospital discharge summaries of seven public maternity hospitals in Rio de Janeiro were analyzed. The standard of process used was 100%. It was not possible to estimate outcome standards, since the necessary adjustment for gestational age was not feasible. Utilization of antenatal corticotherapy in the present study was very low, about 4% and 2%, considering patients up to 33 weeks and 6 days and 36 weeks and 6 days, respectively. Failure to use antenatal corticotherapy when formally indicated deserves attention by health planners and managers, considering: a) the ease in incorporating such a technology, in contrast to the adequate incorporation of special/intensive neonatal care; b) benefits and costs associated with this technology compared to those of delivering neonatal care to premature babies.

[Analysis of adequacy and effectiveness in the use of tocolytics in preterm labor]

The objective of this study was to assess quality of care for premature labor at public maternity facilities in Rio de Janeiro, Brazil, using referents, indicators, and standards of care derived from scientific evidence. The standard utilized in the process analysis for use of betamimetic tocolytics was 100%, considering the related referents. For outcome analysis, the standard applied was the occurrence of premature delivery in 11% of patients within 24 h and in 24% of patients (referent) within 48 h of hospital admission. Use of tocolytics was observed in 18.7% of patients admitted in premature labor. At gestational age from 28 weeks to 33 weeks and 6 days, especially critical for neonatal survival, tocolytics were used in 32.6% of patients. Premature birth occurred in 59% of patients within 24 h and in 64% within 48 h. These outcomes were consistent with the low rate of utilization of tocolytics. Effectiveness of care for preterm labor measured by rate of premature birth was low. Results of the corresponding process and outcomes analysis were consistent.

Low levels of sex hormone-binding globulin and hyperproinsulinemia as markers of increased pancreatic beta-cell demand in men

Low levels of sex hormone-binding globulin (SHBG) are considered to be an indirect index of hyperinsulinemia, predicting the later onset of diabetes mellitus type 2. In the insulin resistance state and in the presence of an increased pancreatic beta-cell demand (e.g. obesity) both absolute and relative increases in proinsulin secretion occur. In the present study we investigated the correlation between SHBG and pancreatic beta-cell secretion in men with different body compositions. Eighteen young men (30.0 +/- 2.4 years) with normal glucose tolerance and body mass indexes (BMI) ranging from 22.6 to 43.2 kg/m2 were submitted to an oral glucose tolerance test (75 g) and baseline and 120-min blood samples were used to determine insulin, proinsulin and C-peptide by specific immunoassays. Baseline SHBG values were significantly correlated with baseline insulin (r = -0.58, P < 0.05), proinsulin (r = -0.47, P < 0.05), C-peptide (r = -0.55, P < 0.05) and also with proinsulin at 120 min after glucose load (r = -0.58, P < 0.05). Stepwise regression analysis revealed that proinsulin values at 120 min were the strongest predictor of SHBG (r = -0.58, P < 0.05). When subjects were divided into obese (BMI > 28 kg/m2, N = 8) and nonobese (BMI < or = 25 kg/m2, N = 10) groups, significantly lower levels of SHBG were found in the obese subjects. The obese group had significantly higher baseline proinsulin, C-peptide and 120-min proinsulin and insulin levels. For the first time using a specific assay for insulin determination, a strong inverse correlation between insulinemia and SHBG levels was confirmed. The finding of a strong negative correlation between SHBG levels and pancreatic beta-cell secretion, mainly for the 120-min post-glucose load proinsulin levels, reinforces the concept that low SHBG levels are a suitable marker of increased pancreatic beta-cell demand.

Fractures of the proximal femur: correlation with vitamin D receptor gene polymorphism

Fractures are the feared consequences of osteoporosis and fractures of the proximal femur (FPF) are those that involve the highest morbidity and mortality. Thus far, evaluation of bone mineral density (BMD) is the best way to determine the risk of fracture. Genetic inheritance, in turn, is one of the major determinants of BMD. A correlation between different genotypes of the vitamin D receptor (VDR) and BMD has been recently reported. On this basis, we decided to determine the importance of the determination of VDR genotype in the presence of an osteoporotic FPF in a Brazilian population. We studied three groups: group I consisted of 73 elderly subjects older than 65 years (78.5 +/- 7.2 years) hospitalized for nonpathological FPF; group II consisted of 50 individuals older than 65 years (72.9 +/- 5.2 years) without FPF and group III consisted of 98 young normal Brazilian individuals aged 32.6 +/- 6.6 years (mean +/- SD). Analysis of VDR gene polymorphism by restriction fragment length polymorphism (RFLP) was performed by PCR amplification followed by BsmI digestion of DNA isolated from peripheral leukocytes. The genotype distribution in group I was 20.5% BB, 42.5% Bb and 37% bb and did not differ significantly from the values obtained for group II (16% BB, 36% Bb and 48% bb) or for group III (10.2% BB, 47.6% Bb and 41.8% bb). No differences in genotype distribution were observed between sexes or between the young and elderly groups. We conclude that determination of VDR polymorphism is of no practical use for the prediction of FPF. Other nongenetic factors probably start to affect bone mass, the risk to fall and consequently the occurrence of osteoporotic fractures with advancing age.

Different growth hormone (GH) response to GH-releasing peptide and GH-releasing hormone in hyperthyroidism

Altered GH responses to several pharmacological stimuli, including GHRH, have been found in hyperthyroidism. The mechanisms underlying these disturbances have not been fully elucidated. GH-releasing peptide-6 (GHRP-6) is a synthetic hexapeptide that specifically stimulates GH release both in vitro and in vivo. The mechanism of action of GHRP-6 is unknown, but it probably acts by inhibiting the effects of somatostatin on GH release. The aim of this study was to evaluate the effects of GHRP-6 on GH secretion in patients with hyperthyroidism (n = 9) and in control subjects (n = 9). Each subject received GHRP-6 (1 microg/kg, iv), GHRH (100 microg, iv), and GHRP-6 plus GHRH on 3 separate days. GH peak values (mean +/- SE; micrograms per L) were significantly lower in hyperthyroid patients compared to those in control subjects after GHRH alone (9.0 +/- 1.3 vs. 27.0 +/- 5.2) and GHRP-6 plus GHRH (22.5 +/- 3.5 vs. 83.7 +/- 15.2); a lack of the normal synergistic effect of the association of both peptides was observed in thyrotoxicosis. However, a similar GH response was seen in both groups after isolated GHRP-6 injection (31.9 +/- 5.7 vs. 23.2 +/- 3.9). In summary, we have shown that hyperthyroid patients have a normal GH response to GHRP-6 together with a blunted GH responsiveness to GHRH. Our data suggest that thyroid hormones modulate GH release induced by these two peptides in a differential way.