Preparation of Dental Resins Resistant to Enzymatic and Hydrolytic Degradation in Oral Environments

The short average service life of traditional dental composite restorative materials and increasing occurrence of secondary caries adjacent to composite restorations and sealants are necessitating the development of new, longer lasting compositions. Novel monomers and their polymers, reinforcing fillers, and adhesive components are needed. The goal of this research is to develop resin systems for use in restorations, sealants, and other dental services that are superior in properties and endurance to currently used bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) and urethane–dimethacrylate products. Ether-based monomers and their polymers that were not susceptible to enzymatic or hydrolytic degradation were prepared and characterized. They showed no degradation under hydrolytic and enzymatic challenges, whereas the hydrolysis of ester links weakened contemporary resins within 16 days under these challenges. The success of the ether-based materials is promising in making durable systems that are subjected to long-term biochemical and hydrolytic challenges in oral environments

SPM results for the gender by cues (Neutral > Cocaine-cues) interaction on the “normalized” metabolic images.

<p>Comparison correspond to Females > Males for uncorrected threshold p_u<0.001 cluster >200 voxels. There were no regions where males had larger changes than females.</p

Demographic and clinical characteristics of participants.

<p>Demographic and clinical characteristics of participants.</p

Clusters where the SPM analysis showed significant Cues by Gender interaction (Females > Males) for p_c>0.05, cluster >200 voxels after covarying for gender differences in daily cocaine use.

<p>The clusters show the location of anatomical region including Brodmann Area (BA) and the coordinates in the Montreal Neurological Institute coordinates x (left to right), y (anterior to posterior) and z (top to bottom), and the corresponding statistical measures at the voxel level (T and Z scores) along with the cluster size for number of voxels. Females showed significantly larger changes in regional metabolism (decreases) than males and there were no brain regions where males had larger changes than females. Note that we report on clusters >45 voxels in order to identify the regions within the large cluster that emerged when we used the preset >200 voxels level.</p

Clusters where the SPM analysis done on the normalized metabolic images showed significant changes (Neutral > Cocaine-cues) for the female participants (p_c>0.05, cluster >200 voxels) after covarying for amount of cocaine used (daily use).

<p>The clusters show the location of anatomical region including Brodmann Area (BA) and the coordinates in the Montreal Neurological Institute coordinates x (left to right), y (anterior to posterior) and z (top to bottom), and the corresponding statistical measures at the voxel level (T and Z scores) along with the cluster size for number of voxels. There where no regions where (Neutral < Cocaine-cues). Note that in the males none of the clusters was significant at p_c<0.05.</p

A. SPM results for the “normalized” metabolic images for Neutral vs Cocaine-cues video conditions in the Females.

<p>Comparison correspond to Neutral > Cocaine-cues for uncorrected threshold p_u<0.001 cluster >200 voxels. There were no regions where metabolism was higher during the Cocaine-cues than the Neutral conditions. <b>B.</b> SPM results for the “normalized” metabolic images for Neutral vs Cocaine-cues video conditions in the Males. Comparison correspond to Neutral > Cocaine-cues for uncorrected threshold p_u<0.005 cluster >200 voxels; we used this lower threshold since there were no significant differences for p_u<0.001. There were no regions where metabolism was higher during the Cocaine-cues than the Neutral conditions.</p

Association between Dopamine D4 Receptor Polymorphism and Age Related Changes in Brain Glucose Metabolism

<div><p>Aging is associated with reductions in brain glucose metabolism in some cortical and subcortical regions, but the rate of decrease varies significantly between individuals, likely reflecting genetic and environmental factors and their interactions. Here we test the hypothesis that the variant of the dopamine receptor D4 (<i>DRD4</i>) gene (VNTR in exon 3), which has been associated with novelty seeking and sensitivity to environmental stimuli (negative and positive) including the beneficial effects of physical activity on longevity, influence the effects of aging on the human brain. We used positron emission tomography (PET) and [¹⁸F]fluoro-D-glucose (¹⁸FDG) to measure brain glucose metabolism (marker of brain function) under baseline conditions (no stimulation) in 82 healthy individuals (age range 22–55 years). We determined their DRD4 genotype and found an interaction with age: individuals who did not carry the 7-repeat allele (<b>7R−</b>, n = 53) had a significant (p<0.0001) negative association between age and relative glucose metabolism (normalized to whole brain glucose metabolism) in frontal (r = <b>−</b>0.52), temporal (r = <b>−</b>0.51) and striatal regions (r = <b>−</b>0.47, p<0.001); such that older individuals had lower metabolism than younger ones. In contrast, for carriers of the 7R allele (<b>7R+</b> n = 29), these correlations with age were not significant and they only showed a positive association with cerebellar glucose metabolism (r = +0.55; p = 0.002). Regression slopes of regional brain glucose metabolism with age differed significantly between the <b>7R+</b> and <b>7R−</b> groups in cerebellum, inferior temporal cortex and striatum. These results provide evidence that the DRD4 genotype might modulate the associations between regional brain glucose metabolism and age and that the carriers of the 7R allele appear to be less sensitive to the effects of age on brain glucose metabolism.</p></div

Differences in brain metabolic activation to the task (percent change) when given with MP when compared with placebo (PL) between subjects in whom MP attenuated brain activation versus those in whom it enhanced activation along with their baseline metabolic measures.

<p>Two subjects showed no differences between MP and placebo (data not included). Comparisons correspond to chi square for the subject numbers (Ss) and to student t-tests (unpaired, two test) for the other comparisons.</p

BOLD signals in hypo-activated regions vs. BMI.

<p>Scatter plots exemplifying the negative correlations between BMI and the average BOLD-fMRI responses across all volumetric conditions (125, 375, 500, 600, and 700 ml) in dopaminergic brain regions (hypothalamus, midbrain, and amygdala) during gradual GD (N = 24).</p

Regional glucose metabolism (µg/100 g/min) when subjects were tested during the neutral non-task with placebo (control condition), cognitive task with MP and cognitive task with placebo.

<p>Data corresponds to mean and standard deviation. Subscripts correspond to paired t-test comparisons with respect to the control condition:</p>a<p>p<0.05, ^b p<0.01, ^c p<0.005, ^d p<0.001. The last column corresponds to the significance level for comparison between the cognitive task when given with MP or when given with placebo (PL).</p