ABSTRACT The carapace of the tortoise Chinemys reevesii is an ingredient of “Guijia”, a traditional Chinese medicine. However, C. reevesii is difficult to raise in aquaculture and is rare in the wild. Counterfeit tablets are made from carapaces of other species. In addition to C. reevesii, other species including Mauremys sinensis, Indotestudo elongate and Trachemys scripta have been used in Plastrum Testudinis as well. After processing, these carapaces are difficult to identify on the basis of morphological characteristics, which impedes law enforcement. Our study used DNA barcoding technology to identify C. reevesii and its substitutes. We extracted concentrated genomic DNA for PCR amplification. Based on the analysis of 61 full-length COI sequences, we designed four pairs of mini-barcode primers: Tu-A, Tu-B, Tu-C and Tu-D. The Tu-B primers sequenced genomic DNA with a success rate of 76.47%, and the Tu-D primers sequenced genomic DNA with a success rate of 88.24%. The identification efficiency of these two mini-barcodes was 70.59% and 64.71%, and the overall identification efficiency was approximately 76.47%. Similarly, a set of mini barcode systems was generated, which may provide an effective and low-cost method for the identification of authentic tortoise shells.

As is commonly understood, the root canal morphology of the maxillary molars is usually complex and variable. It is sometimes difficult to detect the distobuccal root canal orifice of a maxillary second molar with root canal treatment. No literature related to the distobuccal root canals of the maxillary second molars has been published. Objective: To investigate the position of the distobuccal root canal orifice of the maxillary second molars in a Chinese population using cone-beam computed tomography (CBCT). Material and methods: In total, 816 maxillary second molars from 408 patients were selected from a Chinese population and scanned using CBCT. The following information was recorded: (1) the number of root canals per tooth, (2) the distance between the mesiobuccal and distobuccal root canal orifice (DM), (3) the distance between the palatal and distobuccal root canal orifice (DP), (4) the angle formed by the mesiobuccal, distobuccal and palatal root canal orifices (∠PDM). DM, DP and ∠PDM of the teeth with three or four root canals were analyzed and evaluated. Results: In total, 763 (93.51%) of 816 maxillary second molars had three or four root canals. The distance between the mesiobuccal and distobuccal orifice was 0.7 to 4.8 mm. 621 (81.39%) of 763 teeth were distributed within 1.5-3.0 mm. The distance between the palatal and distobuccal orifice ranged from 0.8 mm to 6.7 mm; 585 (76.67%) and were distributed within 3.0-5.0 mm. The angle (∠PDM) ranged from 69. 4º to 174.7º in 708 samples (92.80%), the angle ranged from 90º to 140º. Conclusions: The position of the distobuccal root canal orifice of the maxillary second molars with 3 or 4 root canals in a Chinese population was complex and variable. Clinicians should have a thorough knowledge of the anatomy of the maxillary second molars.