Introduction: The purpose of this in vitro study was to evaluate the effect of thermocycling on the compressive strength of selected luting cements. Material and methods: 5 types of luting cements were tested. A total of thirty cylindrical specimens measuring 6mm in height and 4mm in diameter were prepared for each type of cement which were then divided into two groups ie Group 1: Exposure, and Group 2: Control. Both groups were stored in distilled water at 37°C for 24 hours. Group 1 was subjected to 500 cycles in a thermocycling baths of 5ºC and 55ºC with 20 seconds in each bath. Group 2 was not exposed to thermocycling procedure. The compressive strength for each cement type was determined by using a universal testing machine. Results: Resin adhesive cement had the highest compressive strength; followed by conventional glass ionomer cement (GIC) whilst resin modified GIC was the least. Thermocycling had no significant effect on the compressive strength of RelyXTM ARC and Fuji I (p>0.05), but a significant effect on Fuji I CAPSULE, Fuji CEM, Fuji Plus CAPSLUE (p
Reproduction is associated with the circadian system, primarily as a result of the connectivity between the biological clock in the suprachiasmatic nucleus (SCN) and reproduction-regulating brain regions, such as preoptic area (POA), anteroventral periventricular nucleus (AVPV), and arcuate nucleus (ARC). Networking of the central pacemaker to these hypothalamic brain regions is partly represented by close fiber appositions to specialized neurons, such as kisspeptin and gonadotropin-releasing hormone (GnRH) neurons; accounting for rhythmic release of gonadotropins and sex steroids. Numerous studies have attempted to dissect the neurochemical properties of GnRH neurons, which possess intrinsic oscillatory features through the presence of clock genes to regulate the pulsatile and circadian secretion. However, less attention has been given to kisspeptin, the upstream regulator of GnRH and a potent mediator of reproductive functions including puberty. Kisspeptin exerts its stimulatory effects on GnRH secretion via its cognate Kiss-1R receptor that is co-expressed on GnRH neurons. Emerging studies have found that kisspeptin neurons oscillate on a circadian basis and that these neurons also express clock genes that are thought to regulate its rhythmic activities. Based on the fiber networks between the SCN and reproductive nuclei such as the POA, AVPV, and ARC, it is suggested that interactions among the central biological clock and reproductive neurons ensure optimal reproductive functionality. Within this neuronal circuitry, kisspeptin neuronal system is likely to "time" reproduction in a long term during development and aging, in a medium term to regulate circadian or estrus cycle, and in a short term to regulate pulsatile GnRH secretion.
This study is conducted to compare two resin luting cements (Rely XTMARC,3M and Compolute™ESPE) on their microleakage with one composite inlay system (Filtek™ Z250 Universal Restorative Materials, 3M). Thirty conventional inlays, Class II MOIDO cavity with gingival margin I mm above the cementoenamel junction, were prepared in premolar teeth. The composite inlays were fabricated directly on the prepared teeth using layering technique. Fifteen of the inlays were cemented with RelyTMX ARC and fifteen with Compolute™ (ESPE). The specimens were kept at 370 C for 10 days before thermocycling and immersed in methylene blue 2% solution for 24 hours. The teeth were sectioned mesio-distally. The site and degree of leakage of each section was scored using a visual scoring system under a stereomicroscope at a magnification of 1.5X. Results showed that there was no significant difference in'leakage extent (p>O.05), between Rely X™ARC and Compolute™. For both materials, leakage occurred most commonly within the enamel surface and between the cement-tooth interfaces. None of the leakage occurred between inlay - cement interface. There is no significant difference in the extent of leakage between Rely XTMARC compared to Compolute™.