Human tooth development is a consecutive process, which includes bud stage, cap stage, bell stage and tooth root development.

人类牙齿发育是一个连续的过程，经历了蕾状期、帽状期、钟状期和牙根发育期。

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In this case the cells were taken from what is known as the tooth germ, the little bud that appears before an animal grows a tooth.

在这一研究中，这些细胞来源于所谓的牙胚即动物出牙前发生的幼芽。

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Human tooth development is a reciprocal and consecutive process, which includes bud, cap, bell stages, tooth root development and tooth eruption.

人类牙齿的发育，经历蕾状期、帽状期、钟状期、牙根发育和牙齿萌出期。

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Tooth enamel begins to form in the human embryo when a specialised layer of cells, called ameloblasts, in the embryonic tooth bud secretes amelogenin proteins.

BBC: By BBC News Online Science Editor Dr David Whitehouse