The applicability of diode-pumped solid state (DPSS) laser for light curing the composite resins was tested with a quartz-tungsten-halogen lamp-based unit and a light emitting diode unit. The emission spectra of the light-curing systems used match with the absorption spectrum of camphorquinone. Among the light-curing systems, DPSS laser showed the narrowest emission bandwidth. The light intensity of DPSS laser was approximately 64% of the other two light-curing units. In most specimens, DPSS laser showed the least attenuation of the number of incident photons. On the top surface, specimens cured with DPSS laser showed similar microhardness values compared to the specimens cured with the other two light-curing units. During the light curing, DPSS laser induced the lowest temperature rise (25.5-35.5 degrees C) in the specimens compared to the other two light-curing units (34.2-41.7 degrees C). In conclusion, DPSS laser has high potential to be an alternative to the other light-curing units or a new light-curing unit.

The quality of polymerization of hybrid composite resins was tested to explore their feasibility for dental restorations. For this, microhardness, polymerization shrinkage, the coefficient of thermal expansion, and surface morphology were evaluated during or after light curing in conjunction with the thermocycling process. Each product had different microhardness values. The repeated thermal stimulus has no specific effect on the change of microhardness. The difference of microhardness between the thermocycled specimens and specimens stored only in distilled water was minor. The measured microhardness had a linear correlation with the filler content (vol %) of the tested specimens. The polymerization shrinkage had rapidly increased only during the light curing, and then it reached a plateau. Among the specimens, Z250 showed the least amount of shrinkage for all tested thicknesses. Regardless of the product, the shrinkage values increased as the specimens became thick. The coefficient of thermal expansion of the control specimens ranged between 42 and 55 microm/degrees C in the temperature range of 30-80 degrees C. The coefficient showed an inverse correlation with the filler content. Through the thermocycling process, Palfique Estelite showed randomly propagating cracks on the surface. Larger fillers showed a more apparent detachment than the smaller fillers.

The present study investigated the effect of fluoride released from dental restoratives on orthodontic NiTi wires. Five different restoratives (four fluoride-containing and one non-fluoride-containing) and four different NiTi wires were examined in this study. The pH of artificial saliva (AS) was adjusted to 2.5 and 6. Content of released fluoride was determined daily for 10 days. The morphology of wires was observed using a scanning electron microscope. After immersion for 10 days, the initial microhardness of the wires decreased by 0.3-5.6％ depending on the test solution. Dyract AP (DA) and F2000 (F2) (compomers) released significantly more fluoride than the other resin products (composite resins) regardless of the test solution. In pH 2.5 solution, both DA and F2 released 40-45 ppm/day fluoride for five to six days. As for the wires in contact, they did not show any visible modification in surface morphology. Therefore, despite the released fluoride, wires in contact with the fluoride-containing restoratives were not damaged regardless of the pH value of test solution.

LAS effectively polymerizes dental nanocomposite resins to an extent similar to that of recently available light-curing units. The results suggest that LAS has good potential as a light source for light curing of dental nanocomposite resins.