The Study Of Teeth And Jaw Bones In Skulls Excavated From The Site About 2,000 Years Ago In Long County, Shaanxi, China

The change of the masticatory organs and the prevalence of the oral diseases has been changing along the evolution of human beings. Many undiscovered are still there as the old specimens were absent and insufficient althoug Chinese and foreign reseachers have worked on this for many years. More new and deep researches are needed in this field.Since June 1991, the ancient tombs of the Long County in Shaanxi Pronvince were discovered by Shaanxi Archaeological Institute. Many cultural relics and jaw bones were were excavated from this site. In this study, the cross-sectional study in descriptive epidemiology was used to investigate the morphological measurements and the status of oral cavity diseases. The ages and sexes of the subjects were provided by the Shaanxi Archaeological Institute. The ages of the subjects arranged from 35 to 60 including male and female specimens. The newest and authoritative Diagnostic Standard of the oral disease was adopted. The indice were grouped according to the sex. The results of the measurements and statistics were listed below.1. The morphology of the teeth:832 permanent teeth of 59 individuals were measured. The result showed that canine was the longest the teeth in both maxilla and mandible. Maxillary central incisor was longer than lateral incisor, while mandibular central incisor was shorter than lateral incisor. The indexes of maxillary first premolar were larger than those of second premolar expect the thickness of the dental crown, while in mandible, there was no difference between first and second premolars. All indice of second molars were the largest in both maxilla and mandible, including the full length, the height of the crown and the length of root. There were no obvious differences in the width and thickness of crown and neck in maxilla while in mandible, all the indice of first molars were larger than second molars, and those of third molars were the smallest. In maxilla, crown and neck thickness of canine, crown thickness of first molar and root length of second molar in male specimens were larger than those in female specimens. In mandible, full length and crown width of lateral incisor, crown width of canine, crown and neck thickness and root length of premolar, crown thickness of first and second molars in male specimens were larger than those in female specimens.2. The measurements of the lower jaw bones:Some items were measured in the mandible, including bicondylar breadth(123.46±5.54mm), koronoid breite des unterkiefers (96.48±6.54mm), bigonial breadth(103.48±7.83mm), bimental breite(48.98±3.22mm), height of symphysis 32.64±4.30mm, the height of the mandibular body(left:31.46±3.13mm, 6 right:32.12±2.65mm), thickness of the mandibular body (left:12.77±1.34mm, right:12.86±1.56mm), breadth of the mandibular ramus(left:34.03±2.72mm, right:34.34±2.76mm), breadth of incisura mandibulae(left:36.41±2.90mm, right:37.52±2.62mm), length of the mandibular body(77.09±4.08mm), depth of incisura mandibulae(left:14.50±1.73mm, right:14.89±2.00mm) height of the mandibular ramus(left: 62.54±5.49mm, right: 63.08±5.46mm), mandibular angle(left:122.28±6.51mm, right: 120.75±5.15mm)After measurement of the mental foramen, it was showed that most foramina were ovate while few were oviform. The mental foramina mostly opened upside to the back, rarely opened to the directly upside. The location of mental foramen was mostly under the second premolar(37.08%), and then between the first and second premolar (28.09%). There was no mental foramen existing under the first premolar or the first molar.3. The epidemiology of the oral diseases:In the aspect of periodontal disease, there were 372 teeth in 46 objects having the periodontal disease including 150 in maxilla and 222 in mandible from all the 832 permanent teeth of 59 individuals. The percent of the suffering teeth is 44.72%. 261 teeth of 30 males and 60 teeth of 10 females were suffered. 51 teeth were suffered in 6 sex-unidentified objectsIn the aspect of dental caries, there were 22 males, 8 females and 4 sex-unidentified subjects had decayed teeth and the prevalence rate of dental caries was 57.63%.In the group, the proportion of root cavity was more than that of the neck, and then the occlusion surface while the interproximal caries was the highest and the lingual caries was the lowest according to the tooth surface the other groups. Among the proportion in the whole teeth, both in upper or lower jaws, the second molar was higher than the first molar.In the apects of the dental fluorosis, the maxillary first molar had the highest rate, and then was the maxillary canine. The maxillary central incisor had the least rate in dental fluorosis. In the mandible, the first molar, second premolar and second molar had the highest, second and third rate in dental fluorosis, respectively, while the mandibular central incisor had the lowest rate.As the above showed, many kinds of oral diseases were common in the people about 2000 years ago. Comparing to the modern people, the prevalence rate and the positions of dental caries were different. The prevalence of horizontal alveolar bone resorption was higher than modern people, and the tooth attrition was also severe in the specimens. The heredity and environment were the most important factors affecting the evolution of the jaw bones and teeth in the human, which also affected the clinical symptoms and development of oral diseases in different eras.