ABSTRACT
BACKGROUND: The number of roots and morphology of the root canal system of permanent mandibular first molars vary greatly among different populations; therefore, it is important to be familiar with the variations in the root and root canal for the location and negotiation of the canals. OBJECTIVE: To investigate the variations in the roots and root canal of permanent mandibular first molars in the Han population of southwest Shandong Province by cone-beam CT. METHODS: 656 patients undegoing cone-beam CT examination at the Department of Stomatology, Affiliated Hospital of Jining Medical University, from September 2012 to October 2015 were recruited, and all patients had healthy, well-developed, and untreated bilateral permanent mandibular first molars with normal appearance. Subsequently, the three-dimensional reconstruction based on cone-beam CT data was performed using Planmeca Romexis software to observe the variations in the root and root canal system of permanent mandibular first molars in the Han population of southwest Shandong Province. RESULTS AND CONCLUSION: Among 1312 permanent mandibular first molars, the incidence of permanent mandibular first molars with three roots was 70.66% (927/1312); the majority of root canal variations involved two roots and three root canals, accounting for 48.09% (631/1312). The incidence of distal root was 35.37% (232/656), the incidence of distal root was 29.34% (385/1312) in total teeth, and the incidence of distal root bilaterally was 68.95% (153/232). There was a significantly increased incidence of distal root on the right side than on the left side (P < 0.05), and the incidence in the male was significantly higher than that in the female (P < 0.05). These results suggest that most of Han populations in southwest Shandong Province have permanent mandibular first molars with two roots, and the root canal variations mainly involve two roots and three root canals, with the high incidence of distal root. Moreover, cone-beam CT is available for detecting the variation in roots and root canal system, which can provide references for root canal treatment.
ABSTRACT
BACKGROUND:Hydroxyapatite/gel nano-composite has the same mechanical strength to the natural bone, but its ability to repair bone defects and osteogenic effect need to be confirmed by further studies. OBJECTIVE:To explore the repair effect of hydroxyapatite/gel bionic composite in skul defects of rabbits. METHODS: The hole-like calvarium defect models were established in rabbits, and treated with hydroxyapatite/ gel composites (hydroxyapatite/gel group), autologous skul as positive control (autologous bone group) and nothing as negative control (blank group). The repairing condition in the skul defect areas were observed and analyzed by X-ray and CT at 4, 8, 12 weeks after implantation. RESULTS AND CONCLUSION: After 8 weeks, X-ray assessment showed that normal-like bone tissue appeared in the defect region of the autologous bone group; in the hydroxyapatite/gel group, dense bone with similar morphology to normal bone tissue was found in the central site of defect region, and the boundary was slightly blurred. After 12 weeks, the hydroxyapatite/gel showed blurred edge compared with autologous bone, and the center of the composite was disconnected; in the blank group, a clear and regular transmitted shadow was observed. After 12 weeks, CT examination showed that the hydroxyapatite/gel was connected tightly with the surrounding normal bone tissue. As a new bionic composite, the hydroxyapatite/gel can achieve good effect in repairing skul defects of rabbits.