Common environmental chemicals, drugs, or physical agents can adversely affect human teeth during their embryonic development and after their eruption into the oral cavity. One of the more common elemental toxicants is lead. Teeth are known to accumulate lead during their development. Both animal and human studies have shown that teeth with high lead levels are generally more susceptible to dental caries. Similarly, although inorganic fluorides have long been recognized for their potential to prevent dental caries, exposure to excessive amounts of fluoride when enamel is forming often leads to a type of enamel hypoplasia referred to as dental fluorosis or mottled enamel. Teratogenic agents, such as tetracyclines, a class of antibiotic drugs commonly administered to infants and children, will often result in the discoloration of tooth enamel when prescribed during tooth development. It has recently been suggested that childhood exposure to passive smoking increases the risk for dental caries. Environmental tobacco smoke has previously been linked to periodontal disease in adults. However, this is the first report of an association between passive tobacco smoke and increased susceptibility to dental caries. Last, an often-overlooked source of damage to teeth among all age groups after their eruption into the oral cavity is physical trauma from a variety of sources, especially sports-related injuries. Epidemiologic data suggest that up to one third of all dental injuries are sports related.