Background The prevalence of malocclusion in modern population is higher than that in the excavated samples from the ancient times.Presently,the prevalence of juvenile malocclusion in the early stage of permanent teet...Background The prevalence of malocclusion in modern population is higher than that in the excavated samples from the ancient times.Presently,the prevalence of juvenile malocclusion in the early stage of permanent teeth is as high as 72.92% in China.This study aimed to observe and evaluate the prevalence and severity of malocclusions in a sample of Xia Dynasty in China,and to compare these findings with the modern Chinese population.Methods The material consisted of 38 male and 18 female protohistoric skulls of Xia Dynasty 4000 years ago.Of 86 dental arches,29 cases had the jaw relationships.Tooth crowding,diastema,individual tooth malposition and malocclusion were studied.Results Of the samples,23.3% showed tooth alignment problems including crowding （8.1%）,diastema （9.3%）,and individual tooth malposition （5.8%）.The prevalence of malocclusion was 27.6%,mainly presented as Angle Class Ⅰ.Conclusions It is indicated that over thousands of years from Neolithic Age （6000-7000 years ago） to Xia Dynasty （4000 years ago）,the prevalence of malocclusion did not change significantly.The prevalence of malocclusion of Xia Dynasty samples was much lower than that of modern population.展开更多
The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation. The dentary and diastema lengths of iguanodontians were measured and compared to elucida...The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation. The dentary and diastema lengths of iguanodontians were measured and compared to elucidate the evolution of iguanodontian diastema. A gap in ratios between most non-hadrosaurid iguanodontians and hadrosaurids was observed, suggesting that all non- hadrosaurid iguanodontians, expect for Ouranosaurus nigeriensis and Protohadros byrdi, lack a diastema or have a short diastema, although some other taxa have been considered to have a long diastema in previous studies. In non-hadrosaurid iguanodontians, some large-sized forms, such as Iguanodon bernissartensis, Shuangmiaosaurus gilmorei, and possibly Eolambia caroljonesa, had a short diastema through ontogeny, whereas Ouranosaurus nigeriensis and Protohadros byrdi developed a long diastema convergently. The development of a long diastema of hadrosaurine hadrosaurids may be different from that of lambeosaurine hadrosaurids. Some hadrosaurines （Edmontosaurus annectens, Edmontosaurus regalis, and Saurolophus angustirostris） may have developed a long diastema in the subadult stage and showed little elongation of dentary diastema through ontogeny. Lambeosaurines （Corythosaurus casuarius and Lambeosaurus lambei） tend to have a short diastema in the embryonic and subadult stages, and an elongated diastema from the subadult to adult stages.展开更多
Purpose: With the increased demand for orthodontic treatments in adults, Diastemas have always been an obstacle for either pre or post orthodontic treatment. The purpose of the present investigation is to identify the...Purpose: With the increased demand for orthodontic treatments in adults, Diastemas have always been an obstacle for either pre or post orthodontic treatment. The purpose of the present investigation is to identify the prevalence and location of diastema among patients attending the dental clinics, School of Dental Medicine, University of Nevada, Las Vegas (UNLV). Methods: A retrospective keywords search of the clinical notes of UNLV School of Dental Medicine (SDM) patient charts in AxiUmTM (dental practice management software) was performed using the search terms “diastema” and “midline diastema” to identify the number of cases that clinically presented with diastema from 1/1/2014-9/30/2020. Demographic data were then analyzed using a Chi-square test and compared against Clark County population data. Results: 1182 patients’ records were identified to have one of the search keywords. 56.7% of the patients who presented with diastema were female, 43.1% were male and 0.2% were transgender. 31.5% of patients presenting with diastema were between the ages of 12 and 19. The majority of the diastema cases were in maxillary teeth, followed by diastema in both maxillary and mandibular. The least number of cases had only mandibular diastema. In regards to size, most (look up percent) were mild diastema (1 - 2 mm), followed by moderate (2 mm) and severe (above 2 mm). The reported ethnicity with highest diastema was Hispanic followed by Caucasians and 17% were African Americans. Chi square analysis showed ethnicity results are statistically significant (p Conclusion: Ethnicity and arch are integral predictors for patients who have diastema.展开更多
基金This study was supported by a grant from National Natural Science Foundation of China （No. 30271429）. Er-li-tou Working Team under the Institute of Archeology of Chinese Academy of Social Sciences and the Research Center of Frontier Archeology of Jilin University provided the samples and materials used in this study.
文摘Background The prevalence of malocclusion in modern population is higher than that in the excavated samples from the ancient times.Presently,the prevalence of juvenile malocclusion in the early stage of permanent teeth is as high as 72.92% in China.This study aimed to observe and evaluate the prevalence and severity of malocclusions in a sample of Xia Dynasty in China,and to compare these findings with the modern Chinese population.Methods The material consisted of 38 male and 18 female protohistoric skulls of Xia Dynasty 4000 years ago.Of 86 dental arches,29 cases had the jaw relationships.Tooth crowding,diastema,individual tooth malposition and malocclusion were studied.Results Of the samples,23.3% showed tooth alignment problems including crowding （8.1%）,diastema （9.3%）,and individual tooth malposition （5.8%）.The prevalence of malocclusion was 27.6%,mainly presented as Angle Class Ⅰ.Conclusions It is indicated that over thousands of years from Neolithic Age （6000-7000 years ago） to Xia Dynasty （4000 years ago）,the prevalence of malocclusion did not change significantly.The prevalence of malocclusion of Xia Dynasty samples was much lower than that of modern population.
文摘The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation. The dentary and diastema lengths of iguanodontians were measured and compared to elucidate the evolution of iguanodontian diastema. A gap in ratios between most non-hadrosaurid iguanodontians and hadrosaurids was observed, suggesting that all non- hadrosaurid iguanodontians, expect for Ouranosaurus nigeriensis and Protohadros byrdi, lack a diastema or have a short diastema, although some other taxa have been considered to have a long diastema in previous studies. In non-hadrosaurid iguanodontians, some large-sized forms, such as Iguanodon bernissartensis, Shuangmiaosaurus gilmorei, and possibly Eolambia caroljonesa, had a short diastema through ontogeny, whereas Ouranosaurus nigeriensis and Protohadros byrdi developed a long diastema convergently. The development of a long diastema of hadrosaurine hadrosaurids may be different from that of lambeosaurine hadrosaurids. Some hadrosaurines （Edmontosaurus annectens, Edmontosaurus regalis, and Saurolophus angustirostris） may have developed a long diastema in the subadult stage and showed little elongation of dentary diastema through ontogeny. Lambeosaurines （Corythosaurus casuarius and Lambeosaurus lambei） tend to have a short diastema in the embryonic and subadult stages, and an elongated diastema from the subadult to adult stages.
文摘Purpose: With the increased demand for orthodontic treatments in adults, Diastemas have always been an obstacle for either pre or post orthodontic treatment. The purpose of the present investigation is to identify the prevalence and location of diastema among patients attending the dental clinics, School of Dental Medicine, University of Nevada, Las Vegas (UNLV). Methods: A retrospective keywords search of the clinical notes of UNLV School of Dental Medicine (SDM) patient charts in AxiUmTM (dental practice management software) was performed using the search terms “diastema” and “midline diastema” to identify the number of cases that clinically presented with diastema from 1/1/2014-9/30/2020. Demographic data were then analyzed using a Chi-square test and compared against Clark County population data. Results: 1182 patients’ records were identified to have one of the search keywords. 56.7% of the patients who presented with diastema were female, 43.1% were male and 0.2% were transgender. 31.5% of patients presenting with diastema were between the ages of 12 and 19. The majority of the diastema cases were in maxillary teeth, followed by diastema in both maxillary and mandibular. The least number of cases had only mandibular diastema. In regards to size, most (look up percent) were mild diastema (1 - 2 mm), followed by moderate (2 mm) and severe (above 2 mm). The reported ethnicity with highest diastema was Hispanic followed by Caucasians and 17% were African Americans. Chi square analysis showed ethnicity results are statistically significant (p Conclusion: Ethnicity and arch are integral predictors for patients who have diastema.
