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This study is intended to investigate oral exostoses of 5 sample populations, spanning over 6000 years, from the same region of Northern China, to determine the significance of sex and age on the development of oral exostoses during each time period. The samples analyzed were 306 dry jaws from human skeletons, which were excavated from 4 archeological sites: Banpo (6700-5600 y BP), Shaolingyuan (3000 y BP), Shanren (2200 y BP), and Chang'an (1000-1300 y BP), as well as the modern Xi'an district. The sex and the age of the samples at death were estimated. The degree of buccal exostosis (BE), torus mandibularis (TM), and torus palatinus (TP) and the TP shape were recorded. The results showed BEs in the Banpo and Chang'an regions, TMs in the Banpo region were more often diagnosed in males than in females. Conversely, females in Shaolingyuan showed a higher prevalence and severity of TM than that in males. The occurrence of BEs in the Shanren and Xi'an regions, TMs in the Banpo, Chang'an, and Xi'an regions, as well as TPs in the Banpo region significantly increased with age at death. In conclusion, sex differences and increasing trends with age in relation to oral exostoses were found in samples from Northern China during the past six millennia.

Dens invaginatus (DI) is a developmental anomaly of teeth. Here we observed the characteristics of DI in 517 permanent teeth from 67 ancient Chinese people using micro-computed tomography (micro-CT) scanning techniques. The individuals were excavated from Shaanxi province of China and identified to be about 2,000 years old. Four DI categories are proposed to distinguish the different types of DI. The invaginated lingual fossa is classified into three classes. The overall prevalence of DI in 67 individuals was 31.34% (21 of 67). DI was found in 25 of 517 teeth (4.83%). All affected teeth were maxillary lateral incisors. The invaginated lingual fossa (Type I DI) occurred most frequently (84%), followed by radicular grooves (Type II; 16%), while Type III and Type IV were not found in the present study. Some of fossae correspond with radicular grooves (8 of 21; 3 located at mesial, 5 were distal). The bilateral incidence of DI was 19.05%. Comparing our results to those of a retrospective survey of DI from 1873 to present, we found a higher rate of DI in the excavated teeth of Chinese individuals 2,000 years ago. The use of the micro-CT technique and ethnic origin might have contributed to the higher incidence of DI.

Objective The aim of this study was to evaluate the biomechanical feasibility of a short wide implant in a moderately atrophic posterior maxilla. Study Design A normal maxillary posterior section with a standard screwed implant (model 1) and a moderately atrophic maxillary posterior section with a short wide screwed implant (model 2) were created. The maximum von Mises stresses in maxilla and the maximum displacements in the implant-abutment complex were evaluated. Results When the implant diameter exceeded 5.0 mm, the most stable and minimal value of stress in maxilla and displacement in the implant-abutment complex could be achieved in model 2, which were almost all lower than those in model 1. Conclusions The effect of a short wide implant in the moderately atrophic maxillary sinus region is favorable and similar to that of the standard implant in the normal sinus region. From the biomechanical point of view, implant diameter exceeding 5.0 mm is a relatively optimal selection in a moderately atrophic maxilla.

This study aimed to evaluate continuous and simultaneous variations of dental implant diameter and length, and to identify their relatively optimal ranges in the posterior mandible under biomechanical consideration. A 3D finite element model of a posterior mandibular segment with dental implant was created. Implant diameter ranged from 3.0 to 5.0 mm, and implant length ranged from 6.0 to 16.0 mm. The results showed that under axial load, the maximum Von Mises stresses in cortical and cancellous bones decreased by 76.53% and 72.93% respectively, with the increasing of implant diameter and length; and under buccolingual load, by 83.97% and 84.93%, respectively. Under both loads, the maximum displacements of implant-abutment complex decreased by 58.09% and 75.53%, respectively. The results indicate that in the posterior mandible, implant diameter plays more significant roles than length in reducing cortical bone stress and enhancing implant stability under both loads. Meanwhile, implant length is more effective than diameter in reducing cancellous bone stress under both loads. Moreover, biomechanically, implant diameter exceeding 4.0 mm and implant length exceeding 12.0 mm is a relatively optimal combination for a screwed implant in the posterior mandible with poor bone quality.

Background: Dental caries appears long time ago and attracts great attention in the paleopathological research all over the world. However, few reports presented the status of dental caries in Chinese ancient people. Aim: To describe the prevalence of dental caries in 104 skulls about 2,200 years ago. Materials and Methods: This cross-sectional study was performed using 104 skulls which were excavated from the ar- chaeological sites of Emperor QinShihuang's Mausoleum and Terra-Cotta Warriors and Horses. The degree of caries le- sions was identified and the distribution of tooth cavity was recorded and all the data were statistically analyzed using SPSS15.0 for Windows. Results: Dental caries was common before 2,200 years and the prevalence of dental caries increased with age. The posi- tion of dental caries in the skeletal remains was significantly different and the sequence of prevalence of dental caries was M2 > M3 > M1 > P2 > P1 > I1 > I2 > C. The interproximal lesions were identified as the most common type and the se- verity of every caries lesions was not the same in every skull. Conclusion: This investigation drew a picture of the dental caries of Chinese males living around 2,200 years ago, which will be beneficial to understanding the people's working and living conditions at that time.

Dens invaginatus (DI) is a developmental anomaly of teeth. Here we observed the characteristics of DI in 517 permanent teeth from 67 ancient Chinese people using micro-computed tomography (micro-CT) scanning techniques. The individuals were excavated from Shaanxi province of China and identified to be about 2,000 years old. Four DI categories are proposed to distinguish the different types of DI. The invaginated lingual fossa is classified into three classes. The overall prevalence of DI in 67 individuals was 31.34% (21 of 67). DI was found in 25 of 517 teeth (4.83%). All affected teeth were maxillary lateral incisors. The invaginated lingual fossa (Type I DI) occurred most frequently (84%), followed by radicular grooves (Type II; 16%), while Type III and Type IV were not found in the present study. Some of fossae correspond with radicular grooves (8 of 21; 3 located at mesial, 5 were distal). The bilateral incidence of DI was 19.05%. Comparing our results to those of a retrospective survey of DI from 1873 to present, we found a higher rate of DI in the excavated teeth of Chinese individuals 2,000 years ago. The use of the micro-CT technique and ethnic origin might have contributed to the higher incidence of DI.

This study aimed to create a 3D finite element model for continuous variation of implant diameter and length, thereby identifying their optimal range in type IV bone under biomechanical consideration. Implant diameter ranged from 3.0 to 5.0mm, and implant length ranged from 6.0 to 14.0mm. The results suggest that under axial load, the maximum Von Mises stresses in cortical and cancellous bones decrease by 50% and 27%, respectively; and under buccolingual load, by 52% and 60%, respectively. Under these two loads, the maximum displacements of implant-abutment complex decrease by 39% and 43%, respectively. These results indicate that in type IV bone, implant length is more crucial in reducing bone stress and enhancing the stability of implant-abutment complex than implant diameter. Biomechanically, implant diameter exceeding 4.0mm and implant length exceeding 9.0mm are the combination with optimal properties for a screwed implant in type IV bone.

In this paper, a new analysis method based on the clinical knowledge is proposed and described for the automatic identification of cephalometric landmarks in digital cephalometric radiographs. A layer algorithm for image enhancement is also developed according to the gray-level distribution of the objects and the backgrounds. The experimental results have demonstrated that the proposed method performs better than the existing methods do in terms of their identifiability, accuracy, and dynamic range of images.