齰

昔 = 井 + 日 : Mnemonic symbol: From 奶昔, milkshake

In former times (昔), at the end of the day the sun (日) used to go down in a well (井) in front of the space station (Ø1). Xi Shi (xi) made the sun go out by pouring a milk shake (mnemonic symbol for 昔) over it.

齿 = 止 + 凵 + 人 : Charlie Chaplin (ch) has an aching tooth (齿), and Neanderthal Man (人) is about to help him take it out using an electrical barrier (止) in the space station (Ø3). They attached the barrier to the tooth and as Neanderthal Man will plug it into the receptacle (凵), the barrier will pull out the tooth.