dentin

例句：

1. 1.The dentist examined her teeth and found a cavity.
   牙医检查了她的牙齿，发现有龋洞。
2. 2. The enamel on the front teeth is much harder than that on the back teeth.
   前牙的珐琅质比后牙的硬得多。
3. 3.The patient was advised to brush his teeth twice a day for better dental health.
   患者被建议每天刷牙两次以保持更好的口腔健康。