揭秘牙齿中的VIP 5类牙齿需重点保护

　　CANINES

　　犬牙

　　These are the strongest teeth; their pointed shape makes them useful for shredding, cutting and tearing food. There are four: two on the top, two on the -bottom, on the side of the lateral incisors.

　　犬牙是最坚固的牙齿，锥形的构造让磨牙在碾碎、切断和撕裂食物方面“得心应手”，四颗犬牙上下平均分布，位于门牙的左右两边。

　　PROBLEMS: These contain more dentine to make them stronger so they are difficult to whiten.

　　问题：因为富含牙本质，所以犬牙也非常的坚固，但却也非常难以达到洁白光亮的效果。