The majority of babies are born with their baby, or primary teeth, already lying in wait under the gums. Babies generally start to cut their baby teeth beginning at 6 months, according to the American Dental Association. Primary teeth may continue to erupt until age 3. The age at which your child's baby teeth will appear ranges widely from child to child. In some rare cases, baby teeth do not come in, and in fact have never developed.
Genetic birth defects that affect a child's physical development may also affect his appearance in that he may not cut baby teeth. The National Institutes of Health's MedlinePlus information service explains that babies born with progeria or Down syndrome could end up missing a set of primary teeth. Progeria is a condition in which a child's body ages much more rapidly than her peers. Down syndrome, referred to medically as trisomy 21, occurs when a person is born with three chromosomes instead of two in a particular section of her DNA. Science Daily reports that a gene mutation in a gene called PAX9 can also cause tooth abnormalities and even missing teeth, but that this situation usually consists of a person developing baby teeth and not forming adult teeth.
Hormonal irregularities of the thyroid and parathyroid glands can contribute to the delayed or complete absence of baby teeth, according to MedlinePlus. Both of these glands are located in the neck and secrete hormones that control many different processes in the body, ranging from metabolism to the levels of certain nutrients in the blood. Hypothyroidism and hypoparathyroidism are conditions in which your body doesn't make enough of the hormones secreted by each gland. Suffering from either one or both of these conditions--each one is a separate issue--can affect the development of primary teeth.
The parathyroid glands control the amount of vitamin D and calcium levels in the body, and calcium is a major tooth component. A child suffering from low levels of parathyroid hormone may not get his baby teeth, cut them much later than average age, or experience weak tooth enamel, which could increase his chance of developing cavities.
Bone and Skin Diseases
Diseases of the skin and bones can also contribute to delayed or absent primary teeth, according to MedlinePlus. These diseases are genetic and hereditary in nature. Cleidocranial dystosis and Ellis van Creveld syndrome are conditions in which bones do not develop normally.
Children with cleidocranial dystosis suffer from a malformation of the skull, brow, jaw and collarbones, and may either get primary teeth that do not fall out, or do not cut baby teeth at all.
Ellis van Creveld syndrome, which is fairly rare in the general population, is a condition characterized by short stature or shorter-than-normal limbs, possible cleft palate and a variety of disorders involving the teeth. Children with Ellis van Creveld syndrome might have wide spaces between their teeth or oddly shaped teeth. Some people do not cut primary teeth at all, while others may be born with baby teeth already erupted.
A birth defect causing unusual pigmentation of the skin, called incontinentia pigmenti achromians, might also be a reason why your child is not cutting teeth. Though most of the symptoms of this condition involve lighter-than-normal patches of skin, the bones and teeth can also be affected.