Re: are infants mouths cleaner than adolescents and adults?

A baby's mouth have fewer bacteria than an adolescent. Babies acquire their 
first flora from the mother. Oral bacteria from mother can be transmitted 
to the fetus during pregnancy, during the birth process and from mother to 
child after birth during breast feeding, by example. 
After teeth emerge, the number of attachment sites for bacteria and 
potential bacterial niches increases significantly. The type of oral 
colonization is different between individuals already when they are babies; 
variable bacterial load in saliva of closely related persons and other 
close contacts and how often the baby is exposed to these bacteria may 
partly account for individual differences. In addition, the exposure of a 
baby to antibiotics affects the quality of colonizing bacteria. 
acquisition. At birth the oral cavity is relatively sterile (without 
bacteria) but rapidly becomes colonized from the environment, particularly 
from the mother in the first feeding. In the mouth of the baby, only 
mucosal (soft) surfaces are available.  The bacteria Streptococcus 
salivarius is dominant and may make up 98% of the total oral flora until 
the appearance of the teeth (6 - 9 months). The eruption of the teeth 
during the first year leads to colonization by S. mutans and S. sanguis. 
These bacteria require a nondesquamating (nonepithelial = teeth) surface in 
order to colonize. They will persist as long as teeth remain. Other types 
of streptococci adhere strongly to the gums and cheeks but not to the 
teeth. The creation of the gingival crevice area (supporting structures of 
the teeth) increases the habitat for the variety of anaerobic (live under 
low oxygen content) types of bacteria found. The complexity of the oral 
flora continues to increase with time, and bacteria Bacteroides and 
spirochetes colonize around puberty (teenagers).