恒牙阻生X线研究

目的 调查研究恒牙阻生发生情况及其发生的局部因素。材料与方法 509例（533个）恒牙阻生牙为本组研究对象，并进行X线影像分析。结果 恒牙阻生牙发生率为0．55％。8－14岁年龄组最多见，占65．0％。上下颌骨之比为1．3：1。上颌尖牙阻生发生率最高（146／533）为27．4％。发生阻生的局部因素主要是牙间隙不足。结论 除上颌第1磨牙外，全口恒牙均可发生阻生，保留牙间隙是十分重要的。     

Morphological features of the microdistribution of naturally occurring 10Pb/2l0Po and 226Ra in the teeth of children and juveniles

PURPOSE: To examine the microdistribution of natural alpha-radioactivity in deciduous teeth of children and the permanent teeth of juveniles extracted for orthodontic purpose from across the UK. MATERIALS AND METHODS: The microdistribution of 210Pb-supported 210Po and 226Ra in 708 deciduous and permanent teeth and 32 foetal teeth was measured on 1442 TASTRAK alpha-particle track detectors. RESULTS: Of the various findings, a number are of special interest. Around half of the 210Pb activity in the outer enamel of deciduous teeth appears to have been acquired in utero as a result of transplacental transfer. In deciduous and permanent teeth, 226Ra is concentrated mainly in the circumpulpal region, while the highest levels of 210Po are on the highly calcified outer enamel surface. Furthermore, activity concentrations recorded on this surface were In-normally distributed. CONCLUSIONS: 210Pb-supported 210Po activity on the outer enamel surface of permanent teeth constitutes an assay of cumulative environmental exposure with which to assess exposure in bone, both in utero and in childhood. Such assessment can be used to study geographical variations in the alpha-activity in teeth. More work is also required to determine the concentrations of both 210Po and 210Pb in the foetal skeleton.     

Radiographic examination of dentigerous cysts in the transitional dentition

OBJECTIVES: To examine radiographically the relationship between the deciduous tooth and dentigerous cyst of the permanent successor during the transitional dentition. METHODS: From a retrospective review of all patients who visited our institution from April 1988 to August 2001, 70 patients under 16 years of age who had histologically confirmed dentigerous cysts that had developed from the central incisor to the second premolar were identified. These 70 patients were investigated using panoramic and periapical radiographs. RESULTS: In most cases (54 cases; 77.1%) the cyst was in the premolar region. Of the 54 premolars with dentigerous cysts, the overlying deciduous tooth had already been lost in 7 cases. Of the 47 remaining premolars with associated deciduous tooth, 35 (74.5%) had bone resorption of the periapical or bifurcation region, or irregular resorption of the associated deciduous tooth. Of the remaining 12 deciduous teeth with no periapical lesions, 9 had been treated with root canal therapy. Thus, 44 of these 47 cases (93.6%) had the possibility of inflammation at the deciduous tooth associated with the dentigerous cyst. Evidence from one case in the present study suggesting the process by which cyst development occurs is also given. CONCLUSION: Inflammatory change at the apex of the deciduous tooth may bring on a dentigerous cyst of the permanent successor.     

Deciduous teeth development in fetuses using postmortem computed tomography image analysis

Fetal age is estimated widely by body length and weight and skeletal or dental development and maturation. Regarding dental development, dental development charts reported by Schour and Massler and Ubelaker are well known. We tried to calculate the calcification rate of the deciduous teeth, mandibular cortical bone, and clavicle in fetuses utilizing postmortem computed tomography (CT) image analysis. The CT values within the circumferential area of the region of interest were automatically calculated using a software, and the calcification rate was calculated by performing single regression analysis. Our results showed that deciduous tooth calcification could be detected in over 19-week-old fetuses using CT images. The calcification of bones (mandibular cortical bone and clavicle) started earlier than the calcification of deciduous teeth. However, the calcification rate of the bones was slower compared to that of the deciduous teeth. The calcification rate of the deciduous teeth in fetuses using CT value may be effective to estimate fetal age and evaluate deciduous teeth development, suggesting that our established method is effective for age estimation in forensic dentistry.     

口腔锥形束CT在上颌埋伏牙诊断中的应用价值研究

目的 探讨口腔锥形束CT在上颌埋伏牙诊断中的应用价值.方法 选择我院口腔科于2018年1月至2020年8月期间诊治、检查的120例上颌埋伏牙患者为研究对象,均接受口腔锥形束CT检查,总结分析检查结果,分析其在上颌埋伏牙诊断中的实际应用价值.结果 120例患者上颌埋伏牙均获得清晰显示,其中包括多生牙80颗,阻生牙40颗....     

Impacted teeth in the maxilla: usefulness of 3D Dental-CT for preoperative evaluation

OBJECTIVE: To compare the shapes of roots of impacted teeth shown in three-dimensional computed tomographic images (3D Dental-computed tomography (CT) images) and plain radiographs and to determine whether 3D Dental-CT images are useful for examination before performing an operation for extraction of a maxillary impacted tooth. METHODS AND PATIENTS: Images obtained from patients who had impacted teeth in the maxilla, including impacted mesial supernumerary teeth in 13 patients, impacted incisors in two patients, impacted canines in 11 patients, impacted premolars in four patients and impacted molars in three patients, were used in this study. In all patients, plain radiographs and 3D Dental-CT images were retrospectively reviewed by an oral radiologist for evidence of root dilaceration before operations to extract the impacted teeth were performed. The findings in the images were compared with intraoperative findings in all cases. RESULTS: The mean specificity and sensitivity of plain radiographs were 95 and 8%, respectively, while those of 3D Dental-CT images were 100 and 77%, respectively. There was a statistically significant (P<0.01) difference between the depiction capabilities of plain radiographs and 3D Dental-CT images with regard to dilacerations of roots of impacted teeth. DISCUSSION AND CONCLUSION: CT may enable radiologists to make a quick and accurate diagnosis of tooth impaction. 3D Dental-CT images are useful for determining the root shape of an impacted tooth in the maxilla.     

Morphological features of the microdistribution of naturally occurring 210Pb/210Po and 226Ra in the teeth of children and juveniles

Purpose: To examine the microdistribution of natural α‐radioactivity in deciduous teeth of children and the permanent teeth of juveniles extracted for orthodontic purpose from across the UK.

Materials and methods: The microdistribution of ²¹⁰Pb‐supported ²¹⁰Po and ²²⁶Ra in 708 deciduous and permanent teeth and 32 foetal teeth was measured on 1442 TASTRAK α‐particle track detectors.

Results: Of the various findings, a number are of special interest. Around half of the ²¹⁰Pb activity in the outer enamel of deciduous teeth appears to have been acquired in utero as a result of transplacental transfer. In deciduous and permanent teeth, ²²⁶Ra is concentrated mainly in the circumpulpal region, while the highest levels of ²¹⁰Po are on the highly calcified outer enamel surface. Furthermore, activity concentrations recorded on this surface were ln‐normally distributed.

Conclusions: ²¹⁰Pb‐supported ²¹⁰Po activity on the outer enamel surface of permanent teeth constitutes an assay of cumulative environmental exposure with which to assess exposure in bone, both in utero and in childhood. Such assessment can be used to study geographical variations in the α‐activity in teeth. More work is also required to determine the concentrations of both ²¹⁰Po and ²¹⁰Pb in the foetal skeleton.     

Characteristics and prevalence of non-syndrome multiple supernumerary teeth: a retrospective study

OBJECTIVE: The goal of this study was to evaluate the radiological and clinical findings of non-syndromic multiple (five or more) supernumerary teeth in patients radiographically examined between 1999 and 2004. METHODS: Among 9550 patients, 251 cases of supernumerary teeth were found, including six cases of multiple supernumerary teeth. Patients with multiple supernumerary teeth were evaluated for age, sex, unilateral or bilateral distribution of the teeth, localization, morphology and complications or associated pathologies such as dentigerous cysts, eruption anomalies, resorption of adjacent teeth, displacement of tooth germ, malformation, migration, neurological symptoms, and secondary and periapical infections. RESULTS: All patients were male and most of the multiple supernumerary teeth were seen in the premolar region. The prevalence of multiple supernumerary teeth was 0.06%. Out of 37 multiple supernumerary teeth examined, 30 were impacted. Various associated anomalies were seen in 21.6% of cases. Although the mean age was high (23.1 years), no pathologies such as root resorption on adjacent teeth or cystic formation were observed, in contradiction of previous studies. CONCLUSION: In agreement with previous studies, the majority of supernumerary teeth were seen in the lower premolar region. That all patients with multiple supernumerary teeth were male and that most of these teeth were impacted was also in agreement with previous studies. The order of location frequency in previous studies has been premolar-molar-anterior; we found the order to be premolar-anterior with no supernumerary molar teeth observed. It was also interesting that no serious pathological findings were recorded.     

Multi-detector dental CT in evaluation of impacted maxillary canine

Purpose

To evaluate the role of multi-detector dental CT in the evaluation of the impacted maxillary canine.

Methods and patients

This prospective study included 20 patients who were clinically suspected of having impacted permanent maxillary canines. They were 10 males and 10 females with mean age of 23.3 years. They were exposed to plain radiographs and referred for further evaluation using multi-detector dental CT scanner. The panoramic and paraxial images were obtained. Then reformatted images were done in different planes. Imaging data were analyzed for localization and complication of impacted maxillary canine. Distances and angles measurements were made. MDCT findings were compared with intra-operative data of 24 impacted canines.

Results

A total of 28 impacted maxillary canines were studied in 20 patients. Twelve patients presented with a unilateral impacted canines and 8 with bilateral impactions. The localization of the root apex was 3 (10.7%) labial, 6 (21.4%) palatal, and 19 (67.9%) mid alveolus. The average of the angulations of the impacted maxillary canines to the mid sagittal plane was 39.64. Root resorption was detected in 16 cases.

Conclusion

MD dental CT provides more reliable and accurate information for the intraosseous location, inclination, and morphology of impacted maxillary canine.     

螺旋CT最大密度投影(MIP)对上颌埋伏牙定位的研究

目的　探讨螺旋CT最大密度投影(MIP)对上颌埋伏牙定位的应用价值。方法　对26例疑为上颌埋伏牙的患者做上牙齿轴位螺旋CT扫描,应用图像后处理功能,做最大密度投影,并将MIP图像与多平面重建(MPR),曲面重建(CPR),表面遮盖重建(SSD)对上颌埋伏牙定位的显示率进行比较。结果　4种重建图像中,MIP图像对上颌埋伏牙定位的显示率最高,对埋伏内部结构的密度差异显示最好。26例患者中, 14枚埋伏牙位于腭侧, 10枚位于唇侧; 1枚埋伏牙牙根位于唇侧,而牙冠位于腭侧向内、下生长;另1枚萌出方向与其完全相反。结论　MIP图像对上颌埋伏牙定位的显示效果明显优于MPR、CPR、SSD,可作为颌埋伏牙CT定位的首选图像。     

螺旋CT图像重组对颌骨埋伏阻生牙的诊断价值

目的:探讨螺旋CT图像重组技术对颌骨埋伏阻生牙的诊断价值。方法:对31例颌骨埋伏阻生牙患者行横轴面薄层CT扫描,采用最大密度投影(MIP)、多平面重组(MPR)、曲面重组(CPR)及容积再现(VR)技术进行图像后处理。结果:对31例共38颗埋伏阻生牙,MSCT重组图像均能清楚显示其数量、位置、阻生方位、唇腭侧、萌出方向及与邻牙的关系。结论:螺旋CT图像后处理技术能够正确诊断埋伏阻生牙及其相关情况,对埋伏阻生牙正畸治疗具有重要指导意义     

Rosette formation of impacted molar teeth in mucopolysaccharidoses and related disorders.

The radiographic features of the jaws in the mucopolysaccharidoses and related disorders (MPS) have been reviewed and three further cases are reported here, with particular reference to a novel dental anomaly, not previously described in detail, in two of them. The dental changes appear to be fully developed by the third decade and are characterized by bilateral multiple impacted molar teeth, which conglomerate in a single follicle to form a characteristic rosette of teeth. Rosetting was present only in relatively mature cases of MPS. However, it was also seen in the fourth patient, where we could not detect any other abnormal clinical or radiographic features. We therefore propose that since multiple rosetting of molar teeth can also occur in an isolated form, it is only suggestive of MPS.     

Dental and facial bone abnormalities in pyknodysostosis: CT findings

Pyknodysostosis is an autosomal-recessive disorder of osteoclast dysfunction causing osteosclerosis, with associated maxillofacial anomalies. Multidetector CT with multiplanar and 3D reconstruction illustrated the pathologic findings in this case. Abnormalities included multiple retained deciduous teeth, unerupted teeth with associated follicles, an irregularly expanded alveolus and body of the mandible, and an obtuse mandibular angle. Volume-rendered imaging better delineated the irregular dentition, with crowding and retention of deciduous teeth.     

A method of calculating human deciduous crown formation times and of estimating the chronological ages of stressful events occurring during deciduous enamel formation

Knowledge of deciduous crown formation times is useful in forensic anthropology and when aging juvenile remains from an archaeological context. Until now, histological techniques for calculating enamel formation times in deciduous teeth have been completely dependent on being able to visualise clear daily incremental markings. In the first part of this study we took twenty deciduous teeth where daily incremental markings were easily visible on both aspects of the crown and used these as the basis for generating regression equations to predict enamel formation times. We were then able to use these regression equations to calculate deciduous crown formation times in a further fifty deciduous teeth where it was not possible to see daily increments. We present here new data for deciduous crown formation times based on these regression equations. In the second part of this study these regression formulae were applied blind to teeth from two individuals with known medical histories. The formulae were able to successfully determine the times of prenatal and postnatal enamel formation relative to the neonatal line and also to correctly estimate the ages at which accentuated ‘stress lines’ occurred during the period of deciduous crown formation.     

Dentascan软件在口腔正畸中的应用

目的探讨Dentascan软件在口腔正畸中的临床应用价值。方法对57例埋伏阻生牙患者行16层螺旋CT扫描，应用Dentascan软件重建出上、下颌的曲面全景体层图像及斜面体层图像，并与最大密度投影（MIP）、容积成像（VR）的图像进行对比。结果应用Dentascan软件生成的曲面体层图像及与其垂直的斜面体层图像可以清晰地显示埋伏阻生牙的位置、生长方向及与周围牙齿及颌骨的关系，并可显示埋伏牙的细节。而MIP及VR能直接显示立体三维图像，并且可以多角度旋转观察。结论Dentascan软件结合MIP及VR图像可以在任意方向获得直观清晰的二维及三维图像，对于口腔正畸具有重要的指导意义。     

螺旋CT对上颌前部埋伏牙定位的应用及评价

目的　评价螺旋CT对上颌前部埋伏牙定位的应用价值。方法　对 16例疑上颌埋伏牙患者作上颌牙轴位螺旋CT扫描 ,应用螺旋CT的图像处理功能作多层面重建 (Multiplanarreformation ,MPR)和三维重建 (3dimensionalreconstruction ,3D) ,获得单纯牙体的任何平面、任何曲面的断层像。结果　 16例患者 ,11例埋伏牙位于腭侧 ,4例埋伏牙位于唇侧 ,1例埋伏牙牙根位于腭侧 ,而牙冠位于唇侧。中切牙 9例 ,侧切牙 1例 ,尖牙 6例。结论　螺旋CT对上颌埋伏牙的定位精确 ,能清晰显示上颌前部埋伏牙的形态、唇侧或腭侧位置、萌出方向及与邻牙关系 ,可作为上颌埋伏牙外科处理和正畸治疗的重要检查手段。     

Dental radiographic information of term newborn babies within the first month: Analyzing five radiographic cases along with physical attributes in Japan

BackgroundAlthough dental radiography is a valuable tool for age estimation in forensic anthropology and odontology, very limited radiological data are available regarding tooth development in healthy newborn babies during the first month of life.AimThis study aimed to describe the radiological findings of tooth development in babies aged 0 days to 1 month.DesignWe analyzed the postmortem findings of five newborn babies with no known natural cause of death who had undergone autopsy, computed tomography (CT), and dental radiography. We estimated the gestational age for the babies aged 0 days and analyzed the condition of mandibular symphysis, existence of tooth germs, and presence or absence of calcification of the first permanent molars of all the babies.ResultsThe calcified form of 20 deciduous teeth, tooth germs of the permanent upper and lower first molars, and non-calcified mandibular symphysis were observed in each case. However, calcification of the first permanent molar was observed in only two 1-month-old babies.ConclusionThe dental radiographic findings and anthropometric measurements of non-skeletonized, non-mummified term babies confirmed calcification of all the deciduous teeth and the first permanent molar at the age of 0 days and 1 month, respectively.     

Vitapex用于乳牙根管治疗的临床疗效观察

目的观察Vitapex在乳牙根管治疗中的临床疗效。方法选择乳牙牙髓炎或根尖周炎患儿73例（97颗牙）,常规根管预备后,用Vitapex糊剂行根管充填,随访观察1年。结果成功83颗,失败7颗,成功率为92.2％。结论Vitapex用于乳牙根管治疗的临床疗效较好,是较为理想的乳牙根管充填材料。     

The influence of impaction on the rate of third molar mineralisation in male black Africans

One of the main criteria used in dental age diagnostics in living adolescents and young adults is assessment of the mineralisation stage of the third molars. In the case of Europid populations, it has been established that impaction status has an influence on the rate of mineralisation of the third molars. In view of this, a study was undertaken to determine whether the chronological process of wisdom tooth mineralisation is dependent upon impaction status in black Africans too. Orthopantomograms (553) of 437 male and 116 female black South Africans with verified birth dates in the age group between 10 and 26?years were studied. Mineralisation stage and impaction status were determined for all third molars. Statistical measures were calculated for the mandibular wisdom teeth at stages F, G and H and for the maxillary wisdom teeth at stage H in the male gender for both impacted and non-impacted third molars. It was ascertained that the minimum age in persons with impacted third molars, depending on the wisdom tooth observed, was 0.19–2.57?years higher than in those with non-impacted wisdom teeth. Test persons with impacted mandibular wisdom teeth at stage F or G were on average between 0.32 and 1.88?years older than those with non-impacted mandibular wisdom teeth. The 50?% probability values of impacted wisdom teeth at stage H were 1.85–3.31?years higher than those in non-impacted wisdom teeth. The conclusion was drawn that in male black Africans, impacted mandibular wisdom teeth mineralise more slowly than non-impacted lower third molars. The presence of impacted mandibular wisdom teeth in mineralisation stage H in male black Africans does not, however, furnish proof of completion of the 18^th year of life beyond reasonable doubt.     

Similarly impacted second and third maxillary and mandibular molars in a pair of monozygotic twins

Disturbances of eruption of second and third permanent molars in a monozygotic twin pair are reported. Similarly impacted teeth occurred bilaterally in the maxilla and mandible, with only minor differences between twins. The findings suggest the possibility of a genetic influence.