gingival discoloration

例句：

1. 1. The patient's gingival discoloration was caused by poor oral hygiene.
   患者的牙龈着色是由于口腔卫生不良引起的。
2. 2. The dentist advised the patient to visit more frequently for regular check-ups.
   牙医建议患者定期来诊所做常规检查。
3. 3. The doctor found that the patient had developed a mild form of gingival discoloration.
   医生发现患者患有轻微的牙龈着色症。