Tooth spacing occurs if there is excessive space in the jawbone . treatment varies from case to case 牙齿排列出现空隙，最主要的原因是恒齿的体积跟发育中的颌骨不配合。
2.
Bring the fragment of the fractured tooth . root or bone injury can be detected by professional dental staff only 因为碰伤的部份可能在表面看不到的位置，例如牙根；而且，乳齿受创可能伤害形成中的恒齿。
3.
Tooth crowding occurs if there is inadequate room for all permanent teeth to erupt or when the permanent premolars erupt and the growth of the jawbone stablizes 牙齿排列不整齐由于恒齿的体积比乳齿大，恒齿长出时可能不够空位，引致牙齿排列参差不齐。
4.
The permanent incisor will assume normal position and it is not necessary to extract the mobile primary incisor if there is enough room for the permanent incisor . delayed eruption of permanent teeth 一般来说，乳齿会因为牙根收缩而变得松动，跟着自然脱落，这是正常现象，不会影响恒齿的生长，所以不一定要拔掉松动的乳齿。
5.
Tooth discolouration can lead to intrinsic or extrinsic stains . intrinsic stains may be caused by tetracycline stain , excessive fluoride intake , pulp degeneration after tooth trauma and the presence of metallic restorative materials such as silver amalgam 外在变色是由于食物中的色素附在牙面上，形成斑渍，只要洗牙便可以清除这类斑渍。内在变色的其中一个原因是在乳齿或恒齿的形成过程中，受到一些药物例如四环素的影响。
6.
The permanent teeth may appear darker in colour when compared with the primary teeth because the enamel of the permanent teeth is more highly mineralized and more translucent than that of the primary teeth , allowing the underlying yellow - coloured dentine to show through 由于恒齿的珐琅质钙化得比较好，透光度也比较高，光线可以把珐琅质下层黄色的象牙质呈现出来，恒齿看起来也就比乳齿黄。不过，在某一些情况下，牙齿是会变色的。
