According to a study by the Veterans Affairs Boston Healthcare System, cigarette smoking can lead not only to tooth dis coloration and gum disease, but often to the need for root canal treatment as well.

• 根据退伍老兵事务波士顿保健系统公司进行的一项研究，吸烟不仅会引起牙齿变色和齿龈疾病，而且通常会导致必须进行根管治疗。