Human tooth be categorized according to whether they have environmental or developmental causes. While environmental abnormalities may appear to have an obvious cause, there may not appear to be any known cause for some developmental abnormalities. Environmental forces may affect teeth during development, destroy tooth structure after development, discolor teeth at any stage of development, or alter the course of tooth eruption. Developmental abnormalities most commonly affect the number, size, shape, and structure of teeth. Tooth abnormalities caused by environmental factors during tooth development have long-lasting effects. Enamel and dentin do not regenerate after they mineralize initially. Enamel hypoplasia is a condition
Sociology of human consciousness presumed evolutionary advantages of human reflectivity must be qualified or viewed as conditional. In sum, recent research, building on the work of George Herbert Mead, suggests that a sociological and social psychological perspective can be a point of departure with which to define and analyze certain forms of human consciousness, or more precisely, one class of consciousness phenomena, namely verbalized reflectivity: monitoring, discussing, judging and re-orienting and re-organizing self; representing and analyzing what characterizes the self, what self perceives, judges, could do, should do (or should not do)). The "hard problem" of consciousness can be approached fruitfully by beginning with