Morphological Study Of Permanent Teeth Of Hui Nationality And Mongolian

Tooth morphology research is the foundation of clinical treatment. Many researches showed that tooth morphology is diverse in different times, nationalities and areas. Therefore investigations of morphology for permanent human teeth of different races are especially important in which it could provide anatomic data for clinical treatment of tooth. However systematic study of tooth morphology in different nationalities is scattered in current period.1. Anatomic measurement of the Mongolian and Hui Nationality Permanent teeth348 Mongolian permanent teeth and 314 Hui Nationality permanent teeth were collected and length of the teeth , height of dental crowns, length of dental roots,mesiodistal and buccolingual crown diameters, width of the dental neck were measured, and then data was analyzed by SPSS software package. The results indicates that the crown length of the maxillary canine, mandibular molar and the length of maxillary, mandibular canine, maxillary first molar of Hui adults are significantly longer than those of Mongolian (p<0.05). The length of mandibular lateral incisor, mesiodistal and buccolingual crown diameter of maxillary first premolar, and the dental neck width of maxillary first molar of Hui adults are significantly shorter than those of the Mongolian (p<0.05). The position of root bifurcation of mandibular second molar of Hui adults are significantly closer to apex than those of Mongolian (p<0.05). The average distance between main foramen and anatomic root apex of Hui Nationality Permanent teeth are 0.42-0.62mm, while distance of Mongolian Permanent teeth are between 0.38—0.60mm. There are close relations among crown length with the span, width of the dental neck, the mesiodistal length and the buccolingual length (P<0.05). It could be possible to estimate other indices through crown length.Differences in Morphology of permanent teeth existed among Mongolian, Hui Nationality and Han Nationality.2. Study of root Canal Curvatures in Mongolian and Hui Nationality Permanent teethMongolian and Hui Nationality Permanent teeth were examined by indirect digital radiography both from huccolingual and mesiodistal directions.Curvature and the curve length of the roots, and position of the curve were measured based on modified Schneider method.54.55% of mandibular lateral incisor, 68.42% of mandibula canines and 64.52% maxillary first premolar in bucco-lingual directions of Hui Nationality have curved root canals,which are significantly higher than those of the Mongolian (17.65%,23.53%,20%) (p<0.05), but approximately to Han nationality. In mesiodistal direction , curved root canal length of Hui Nationality mandibular second premolar is significantly longer than that of the Mongolian (p<0.05),and curvature of Hui Nationality mandibular central incisor is significantly bigger than that of the Mongolian (p<0.05). In buccolingual directions, curvature of Hui Nationality mandibular central incisor, manibular first premolar is significantly bigger than that of the Mongolian (p<0.05). In anterior teeth and premolars, most of root canals are of typed I.Curves of anterior teeth and premolars mainly appear in the one third of the apical part of the root, while a few of curves appear in one third of cervical region.The conclusion is consistent with Han nationality.3. Root canal morphology of Mongolian and Hui Nationality Permanent teethThe root canal system of the collected teeth was observed. The ink was pressed into pulp cavities from the apical foramen by high pressure oxygen technique. After decalcification and dehydration in series of alcohol solutions, the teeth were finally fixed in methysalicylate and made into transparent specimen.The study shows that the incidence of two canals in mandibular anterior teeth are approximately 30%, which is insignificantly different between Mongolian and Hui Nationality (p>0.05). The incidence of two canals in mandibule premolars are lower than maxillary premolars (P<0.05).All mandibular first molar have two separate roots. The incidence of two canals in the mesial roots are significantly higher than distal roots (P<0.05). More than 85% of distal roots in mandibular molar have single canal. The incidence of accessory roots canal were lower than 10%, and could be found only in maxillary molars and mandibular molar. Intercanal communications appeare in maxillary premolars and molars. The incidence of the intercanal communications, apical ramification and apical furcation between Mongolian and Hui Nationality didn't show obvious difference (p>0.05). Root canal morphology of Mongolian and Hui Nationality is as complex as Han nationality. The differences of the anatomical shape of root canal do exist among different races.