Objective: To investigate the changes in the quantity of colonizing Streptococcus mutans(S. mutans) and Actinomyces on the root surface plaque before and after post-core crown restoration of the mandibular first molars in the elderly patients.
Methods: A total of 30 elderly patients, each with one post-core crown restoration of the mandibular first molar, were randomly chosen to participate in the studies. Patients with mandibular first molars with post-core crown restoration and those with healthy contralateral mandibular first molars were divided into the test and control groups, respectively. Root surface plaques of the two groups were collected before tooth preparation, 72 h after preparation, one week after preparation, and one month after restoration. S. mutans, Actinomyces naeslundii (A. naeslundii) and Actinomyces viscosus (A. viscosus), were identified using colony morphology, biochemical techniques, and polymerase chain reaction (PCR). Plaque count was measured using microbial colony count.
Results: The number of S. mutans and A. viscosus and A. naeslundii in the test group, which was statistically significant (P<0.05), increased 72 h after preparation. The quantities of S. mutans, A. viscosus, and A. naeslundii one week after preparation were significantly different (P<0.05). The plaque count of S. mutans, A. viscosus, and A. naeslundii in the test group decreased one month after restoration (P<0.05).
Conclusion: The quantities of S. mutans, A. viscosus and A. naeslundii increase one week after preparation but decrease one month after restoration. The finding suggests that dentists should educate patients about plaque control during the early period after tooth preparation.
目的: 研究老年人桩核冠修复前后不同时期根面菌斑中主要致龋菌定植数量变化。
方法: 以单纯随机法选择下颌第一磨牙无咬合功能的患者30人，将一侧需行桩核冠修复的第一磨牙和对侧健康第一磨牙分为受试牙和对照牙。受试牙预备前、预备后72 h、预备后1周及冠修复后1个月，分别采集受试牙与对照牙根面菌斑，然后进行厌氧培养、分离，通过菌落形态学检查、生化特征及聚合酶链反应（PCR）对其中变异链球菌、内氏放线菌和黏性放线菌进行鉴定和菌落计数。
结果: 受试牙变异链球菌预备前、预备后72 h、预备后1周、修复后1个月菌落计数的变化差异有统计学意义（P<0.05）。受试牙黏性放线菌菌落计数在预备前、预备后72 h、预备后1周、修复后1个月的变化差异有统计学意义（P<0.05）。受试牙内氏放线菌菌落计数在预备前、预备后72 h及1周、修复后1月的变化差异有统计学意义（P<0.05）。
结论: 变异链球菌、内氏放线菌及黏性放线菌在预备后1周菌落计数增加，修复后1个月菌落计数降低。以上结果提示在牙体预备后初期，应指导患者进行菌斑控制。