Maximum voluntary bite force is an indicator of the functional state of the masticatory system and the level of maximum bite force results from the combined action of the jaw elevator muscles modified by jaw biomechanics and reflex mechanisms. The measurement of bite force can provide useful data for the evaluation of jaw muscle function and activity. It is also an adjunctive value in assessing the performance of dentures. Technological advances in signal detection and processing have improved the quality of the information extracted from bite force measurements. However, these measurements are difficult and the reliability of the result depends on a number of factors, such as presence of pain and temporomandibular disorders, gender, age, cranio-facial morphology, and occlusal factors. In addition to these physiological factors, recording devices and techniques are important factors in bite force measurement. Therefore, one should be careful when comparing the bite force values reported in the research.

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This study investigated the effects of three bleaching agents (Whiteness Perfect, Whiteness Super, and Whiteness HP) on the color change and refractive index of three dental composites (Admira, Durafill VS, and Gradia Direct). Twenty diskshaped specimens (10×2 mm) of each composite were prepared and divided into four subgroups (n=5). An unbleached group was used as a control, while the remaining specimens in the three subgroups were bleached with one of the bleaching agents respectively. Color change was assessed according to CIELAB color system and refractive indices were determined by phase modulated spectroscopic ellipsometry. Color differences between bleaching and baseline value (ΔE) were less than 3.3 for all groups. However, bleaching with Whiteness HP led to noticeable color changes for Admira and Durafill VS. While this agent had no effect on the refractive indices of these composites, the other two agents containing carbamide peroxide increased their refractive indices. Therefore, results suggested that replacement of such composite restorations may be required after bleaching.

This study was performed to determine whether some flexural properties of a denture base resin material could be improved through reinforcement with five types of aesthetic fibers at 3% concentration by weight and in 2, 4, and 6 mm length. Five specimens of similar dimensions were prepared for each of the test groups; base resin and the same resin with glass, rayon, polyester, nylon 6 and nylon 6,6 fibers in three different lengths. Flexural properties were evaluated by using a 3-point bending test. A visual examination was also made to determine mode of fracture of the specimens. The incorporation of different fibers in varying lengths had no significant effect on flexural strength of the resin. The specimens reinforced with nylon 6,6 fibers of 6 mm length showed the highest flexural strength. Young's modulus and maximum load suggests that such reinforcement makes resin resistant to fracture.

This study examined the surface microhardness of four kinds of resin composites with different fillers and resin matrices. Ten specimens of 2 mm thickness and 4 mm diameter of each resin composite were polymerized using a halogen light, a blue light-emitted diode, and a plasma arc unit. Microhardness evaluation was performed at top and bottom surfaces for each specimen using a Vickers microhardness tester. Furthermore, morphologies of the polished top surfaces of composites cured with blue light-emitted diode were observed using scanning electron microscopy. Results indicated that composites cured with halogen or blue light-emitted diode light yielded higher microhardness values, although it also appeared to depend on the type of composite cured. Plasma arc curing according to manufacturer' s instructions yielded the lowest microhardness values for all the materials. Among the materials tested, the nanofilled resin composite displayed the highest microhardness values for each curing regime.

It has long been assumed that most parts of a genome and most genetic variations or SNPs are non-functional with regard to reproductive fitness. However, the collective effects of SNPs have yet to be examined by experimental science. We here developed a novel approach to examine the relationship between traits and the total amount of SNPs in panels of genetic reference populations. We identified the minor alleles (MAs) in each panel and the MA content (MAC) that each inbred strain carried for a set of SNPs with genotypes determined in these panels. MAC was nearly linearly linked to quantitative variations in numerous traits in model organisms, including life span, tumor susceptibility, learning and memory, sensitivity to alcohol and anti-psychotic drugs, and two correlated traits poor reproductive fitness and strong immunity. These results suggest that the collective effects of SNPs are functional and do affect reproductive fitness. collective effects, complex traits, minor alleles, SNPs, recombinant inbred lines, minor allele content (MAC) Citation:

This study was conducted to observe the changes in impact resistance of a denture base resin reinforced with five types of fiber. E-glass, polyester, rayon, nylon 6, and nylon 6/6 fibers were cut into 2, 4, and 6 mm lengths and added into the resin at a concentration of 3 ％ by weight. Five test specimens for each formulation, as well as control specimens without fiber, were prepared using a mold including a V-shaped notch with 55×10×10 mm dimensions. Impact tests were carried out using a Charpy-type tester. Additionally, surfaces of the impact sections were observed under a scanning electron microscope (SEM). Results indicated that impact energy tended to increase with fiber length, and that the highest value was recorded for rayon fiber-reinforced specimens of 6 mm length. E-glass fiber reinforcement produced relatively stable, high values for each length, whereby good interfacial strength between polymer matrix and glass fibers was confirmed by SEM analysis.