as well as the impression tray 200 with the dental guard 100 positioned therein the storage case 300 is further provided with a cover member 302 secured to the closed base 303 via a living hinge connection 316 the perimeter edge 318 of the cover member 302 is shaped and dimensioned to mate with the upper ends 320 of the side walls 310 when the cover member 302 is brought into engagement with the storage case base 303 the perimeter edge 318 of the cover member 302 opposite the edge of the cover member 302 with the living hinge 316 is provided with a fastening notch 322 shaped and dimensioned to engage a fastening notch 324 formed along the upper end 320 of the side wall 310 in this way the cover member 302 may be secured to the closed base 303 so as to enclose the cavity defined by the closed base 303 while the closed base 303 is formed without holes or other apertures so as to provide a cavity 308 in which water may be contained the cover member 302 includes a plurality of venting apertures or holes 304 allowing for the venting of water vapor when the system 10 is subjected to microwave energy and heated in accordance with the present invention thus excess pressure in the storage case 300 and over heating of the dental guard is prevented in accordance with a preferred embodiment the dental guard 100 is impregnated.