A lay box has nothing to do with eggs being healthy. The question doesn't really make sense. A laybox is a merely tool that stimulates the natural behavior a female dragon exhibits while laying her eggs. Many dragons will retain eggs or not lay them if she is not provided a safe and comfortable place to dig and lay. I've seen eggs laid in hot cages, but they were dry and dimpled, the dry heat will kill them quickly. A lay bin is more suitable because it has stable temps and moist substrate, similar to what they would find in nature. Its a mothers instinct to dig a tunnel and bury her eggs to protect them from predators, then the perfect combination of warmth and moisture from the earth is necessary to incubate them. We provide these things artificially because its what works best. On the other hand, an incubator and moist substrate is very necessary for the eggs to stay healthy, as long as they are healthy to start with, from a healthy dragon who laid them.