During childhood , teen years and early adulthood , new bone tissue is added faster than existing bone is absorbed . as a result , bones become larger and heavier until about age 30 when peak bone mass is reached 儿童时期青春期和成年后的早期新骨的生成大于现有骨骼的吸收，骨骼越长越大，骨质也越来越密，
If true , this would mean that new dental stem cells capable of producing nearly all the dental tissue types required for bioengineering teeth might exist within teeth themselves , at least until early adulthood , when wisdom teeth erupt 如果这是真的话，那也就表示，能够制造出几乎所有生物工程牙齿所需组织的新生牙齿干细胞，可能就在牙齿里（至少在成年初期智齿冒出之前） 。
College students , in the period of transition from adolescence to early adulthood , have an intensive desire for recognition of individual abilities , and it is necessary to raise the degree of self - recognition and sense of accomplishment through training and elevation of practical ability 由青年期向成年早期过渡的大学生对个体能力的认同需求十分强烈，有必要通过实践能力的锻炼提高个体自我认同度和成就感。
