Teeth eruption. If by delayed teeth you mean teeth that haven't erupted yet, there is concern for spacing issues with other teeth and your biting pattern or how your teeth fit together when you bite. This is known as occlusion. If you're occlusion is not right you can wear your teeth abnormally and cause teeth to fracture or chip.
Lots of reasons. Trauma, crowding, premature loss of baby teeth, and so many other things can cause delay of eruption of permanent teeth. Also, sometimes we have baby teeth with no underlying permanent teeth. Go see a cranio-facial growth and development specialist, an orthodontist, for examination and evaluation.