Voltammetric lability of multiligand complexes: the case of ML2

The voltammetric lability of a complex system, where a metal ion M and a ligand L form the species ML and ML₂, is examined. Together with the rigorous numerical simulation of the problem, two limiting cases are analysed for the overall process ML₂ → M: (i) the most common case for aqueous complexes, where ML → M is the kinetically limiting step and (ii) the case where ML₂ → ML is limiting. In both cases, analytical expressions for the lability criteria are provided which show good agreement with the results obtained from the rigorous numerical simulation of the problem.     

Microtensile bond strength tests: scanning electron microscopy evaluation of sample integrity before testing

The failure of a certain number of microtensile specimens during their preparation and before loading is a common and undesirable occurrence. This study was aimed at observing, under a scanning electron microscope, enamel and dentin microtensile specimens, in order to find structural faults that might be responsible for their premature failure. In a sample of 80 sticks, none of the specimens was found to be free of defects. These may consist of microcracks in enamel, most often at the periphery of the stick, or in dentin at the level of hybrid layer. Gaps were often seen at the interfaces between the substrates. Voids were sometimes visible within the resin composite thickness. Enamel specimens tended to exhibit more defects than dentin specimens. It is fair to suspect that, because of the brittleness of the tissue, enamel microtensile specimens are intrinsically more prone to failure, thus yielding bond strengths which are not significantly higher than those measured on dentin specimens. This leads one to question the reliability of the microtensile method for testing adhesion on enamel. It seems sensible to develop a method for a quantitative assessment of specimens integrity before loading as a possible predictor for their performance under load.     

Composite-to-composite microtensile bond strength in the repair of a microfilled hybrid resin: effect of surface treatment and oxygen inhibition

PURPOSE: To compare the 24-h microtensile bond strength of a microfilled hybrid composite to the same material after mechanical and/or chemical treatment and assess the effect of oxygen inhibition on the composite-composite bond. MATERIALS AND METHODS: Forty composite cylinders of Gradia Direct Anterior (GC) were prepared and stored 24 h prior to the following surface treatments: 50-microm aluminum oxide air abrasion and 37% phosphoric acid etching (group 1); hydrochloric acid and 6.9% hydrofluoric acid etching (group 2); diamond bur roughening and 37% phosphoric acid etching (group 3); diamond bur roughening (group 4). In all groups, Prime & Bond NT (Dentsply De Trey) was applied and light cured in air or under a nitrogen atmosphere, prior to layering a buildup of the repairing resin composite. Microtensile bond strength measurements were performed. Data were statistically analyzed with two-way ANOVA and Tukey's test (alpha = 0.05). RESULTS: The curing atmosphere did not significantly influence the interfacial strength (p < 0.05). Surface treatment significantly affected the composite-composite bond (p > 0.05). Air abrasion, regardless of curing atmosphere, resulted in the strongest bond (p < 0.05). The other treatments were comparable. CONCLUSION: Air abrasion and the application of a bonding agent offer satisfactory bond strengths for composite repair. The oxygen inhibition layer on a light-cured adhesive is not crucial to the success of the 24-h composite-composite bond.     

Palatine perforation induced by cocaine

Worldwide, the use of cocaine has an increased over the years, various secondary effects have been described. Here we present a 48 years old female with a 2-month evolution bucconasal ulcer in the hard palate induced by cocaine usage accompanied by swallow and phonation dysfunctions. Ethiopathogenesis, differential diagnoses and treatment are discussed.     

Effect of pre-cure temperature on the bonding potential of self-etch and self-adhesive resin cements.

OBJECTIVES: To assess whether the pre-cure temperature of resin cements significantly influenced the bonding potential to dentin. METHODS: Forty extracted molars were randomly divided into 8 groups (n=5): Groups (1-4) RelyX Unicem (RU, 3 M ESPE) and Groups (5-8) Panavia F 2.0 (PF, Kuraray Co.), at pre-cure temperatures of 4, 24, 37, and 60 degrees C, respectively. Cements were used in dual-cure mode for luting composite overlays (Paradigm MZ100, 3 M ESPE) to dentin. Microtensile bond strength testing and scanning electron microscope (SEM) observations of cement-dentin interfaces were performed. RESULTS: Group 4 had to be eliminated as RU at 60 degrees C underwent such an accelerated curing that was already set at the time of dispensing. The bond strengths (MPa) measured at refrigerator, room, and intraoral temperature were, respectively: RU 5.4+/-1.7, 11.4+/-6.1, 10.6+/-4.2; PF 7.4+/-3.7, 13.9+/-6.2, 12+/-5.2. The statistical analysis revealed that both luting agents developed a significantly weaker adhesion when used at refrigerator temperature (p<0.05). No statistically significant differences in bond strength were recorded when either cement was used at 24 or 37 degrees C (p>0.05). Pre-heating of PF to 60 degrees C resulted in a significant increase in bond strength (20.7+/-9.4 MPa; p<0.05). SEM observations disclosed an enhanced potential of PF to form a hybrid layer as the temperature increased over 4 degrees C. RU exhibited a less porous and more homogeneous layer at intraoral than at refrigerated temperature. SIGNIFICANCE: It is advisable to let refrigerator-stored resin cements warm up to at least room temperature prior to clinical use. Pre-heating to 60 degrees C enhances the bonding potential of PF.     

Monitoring of demineralized dentin microhardness throughout and after bleaching

PURPOSE: To evaluate the effect of six bleaching agents: Nite White [NW] 10% and 22% Excel 2Z (Discus Dental), Rembrandt (REM) 10% and 22% (DenMat), Opalescence (OPA) 10% and 20% (Ultradent) and a placebo agent on demineralized dentin microhardness at different time intervals. METHODS: 105 human dentin slabs (3 x 3 mm) were embedded, planed and submitted to cariogenic challenges, composed of de- and remineralization cycles. For 42 days, specimens were exposed to bleaching agents, consisting of applying them daily for 8 hours, removing and storing the specimens in artificial saliva for 16 hours. At the end of the bleaching treatment, specimens were kept in artificial saliva for 14 days. Knoop Microhardness tests were performed on specimens' surface before (baseline), during (8 hours, 7, 14, 21, 28, 35 and 42 days) and after bleaching procedures (7 and 14 days). RESULTS: The ANOVA for split-plot showed significant effect on the interaction between bleaching agent and time (alpha =0.05). Tukey's test revealed no significant differences on demineralized dentin microhardness exposed to bleaching agents until Day 7. Regression analyses demonstrated that NW 10% and 22% and OPA 10% and 20% increased dentin microhardness in different magnitudes, whereas REM 10% and 22% induced mineral loss during bleaching agent application, followed by microhardness recovery in the post-treatment period.     

Placement of fiber prefabricated or custom made posts affects the 3-year survival of endodontically treated premolars

PURPOSE: To assess whether the amount of residual coronal dentin and the placement of a prefabricated (DT Light Post) (LP) or a customized fiber post (Ever Stick Post) (ES) have a significant influence on the 3-year survival of endodontically treated premolars. METHODS: A sample of 345 patients provided six groups of 60 premolars in need of endodontic treatment. Groups were defined based on the amount of dentin left at the coronal level after endodontic treatment and before abutment build-up. Within each group teeth were randomly divided into three subgroups (n = 20). In Subgroup A, no root canal retention was provided for the coronal restoration. In Subgroups B and C, LP and ES, respectively, were placed inside the root canal. All the teeth were finally restored with a single unit metal-ceramic crown. RESULTS: Data were not affected by any loss to follow-up. The overall 36-month survival rate of crowned endodontically treated premolars was 76.7%. The lowest survival rate was recorded for teeth restored without any root canal retention (62.5%). Teeth restored with LP had a survival rate higher (90.9%) than those restored with ES (76.7%). The Cox regression analysis showed that the presence of root canal retention was a significant factor for survival (P < 0.05). The decrease in failure risk was higher in teeth restored with LP (HR = 0.1; 95% CI for HR = 0.09 to 0.34; P < 0.001) than when using ES (HR = 0.5; 95% CI for HR = 0.3 to 0.7; P = 0.003). Teeth retaining one (HR = 0.3; 95% CI for HR = 0.2 to 0.7; P = 0.003), two (HR = 0.2; 95% CI for HR = 0.1 to 0.5; P < 0.001), or three coronal walls (HR = 0.1; 95% CI for HR = 0.05 to 0.3; P < 0.001) had a significantly lower failure risk than teeth deprived even of the ferrule effect. Similar failure risks existed for teeth missing all the coronal walls regardless of the presence or absence of a ferrule effect (P > 0.05). Interaction terms were not significant (P > 0.05). Post placement and the amount of residual coronal dentin affected the 3-year survival of endodontically treated premolars.     

Expression of Phosphofructokinase in Skeletal Muscle Is Influenced by Genetic Variation and Associated With Insulin Sensitivity

Using an integrative approach in which genetic variation, gene expression, and clinical phenotypes are assessed in relevant tissues may help functionally characterize the contribution of genetics to disease susceptibility. We sought to identify genetic variation influencing skeletal muscle gene expression (expression quantitative trait loci [eQTLs]) as well as expression associated with measures of insulin sensitivity. We investigated associations of 3,799,401 genetic variants in expression of >7,000 genes from three cohorts (n = 104). We identified 287 genes with cis-acting eQTLs (false discovery rate [FDR] <5%; P < 1.96 × 10⁻⁵) and 49 expression–insulin sensitivity phenotype associations (i.e., fasting insulin, homeostasis model assessment–insulin resistance, and BMI) (FDR <5%; P = 1.34 × 10⁻⁴). One of these associations, fasting insulin/phosphofructokinase (PFKM), overlaps with an eQTL. Furthermore, the expression of PFKM, a rate-limiting enzyme in glycolysis, was nominally associated with glucose uptake in skeletal muscle (P = 0.026; n = 42) and overexpressed (Bonferroni-corrected P = 0.03) in skeletal muscle of patients with T2D (n = 102) compared with normoglycemic controls (n = 87). The PFKM eQTL (rs4547172; P = 7.69 × 10⁻⁶) was nominally associated with glucose uptake, glucose oxidation rate, intramuscular triglyceride content, and metabolic flexibility (P = 0.016–0.048; n = 178). We explored eQTL results using published data from genome-wide association studies (DIAGRAM and MAGIC), and a proxy for the PFKM eQTL (rs11168327; r² = 0.75) was nominally associated with T2D (DIAGRAM P = 2.7 × 10⁻³). Taken together, our analysis highlights PFKM as a potential regulator of skeletal muscle insulin sensitivity.