I'm a dental nurse and the answer is basically how the child feels. If the child feels like they could get a filling done then the dentist would be willing, with baby teeth usually there is no need to numb the teeth so it shouldn't be that bad. Cold feeling and a buzzy feeling
The fluid-filled cavity in an embryo, in the early embryonic stage, is called a blastocoele, or blastocyst cavity; this is perhaps the cavity you're referring to.See the link below for more information on the human embryo.
A blastocoele is the fluid-filled cavity in the blastula.
you get one for every cavity you have
A sinus is an air cavity in bone.
Mold
the bladder
The vacuole is a fluid-filled membrane-surrounded cavity located inside a cell
the cavity filled with grains of sand or clay.
A vesicle is a fluid, or air, filled cavity.
A blastocoel is the fluid-filled cavity in the blastula.
A blastocele is the fluid-filled cavity in the blastula.
The tympanic cavity.