恒牙牙冠与牙根长度发育完成时间及性别差异探讨

目的 确定不同恒牙(除第三磨牙外)的牙冠与牙根长度的发育完成时间,探讨牙冠与牙根长度发育完成时间的性别差异。方法 选择3304例3~18岁儿童与青少年全口曲面体层片,应用Haavikko法分别记录每个恒牙的发育分期,采用SPSS 25.0软件包计算男女不同恒牙的牙冠与牙根长度发育完成时间的中位数,利用Mann-whitney U检验进行男女性别间差异比较。结果 中切牙和第一磨牙的牙冠发育完成时间无性别差异,P值分别为0.143(上颌中切牙)、0.122(上颌第一磨牙)、0.191(下颌中切牙)和0.558(下颌第一磨牙),其余牙女性均显著早于男性。上颌中、侧切牙、第二前磨牙和第二磨牙的牙根长度发育完成时间无性别差异,P值分别为0.057、0.130和0.294;下颌中,第二前磨牙和第二磨牙的牙根长度发育完成时间无性别差异,P值分别为0.428、0.057;上、下颌其余牙牙根长度发育完成时间女性均显著早于男性。结论 恒牙牙冠与牙根长度发育完成时间女性普遍早于男性,上、下颌恒牙牙冠与牙根长度发育完成时间的性别差异相似。     

Polymorphisms in sequence of permanent tooth emergence: a cross-sectional study on Jordanian children and adolescents

Abstract

Objective. This study aimed at providing the norms of polymorphic gender- variation in the sequence of permanent tooth emergence in Jordanian children and adolescents. Materials and methods. A total of 2650 Jordanian children and adolescents (1232 males and 1418 females) aged 4–16 years were examined for permanent tooth emergence. By counting the cases of present–absent and absent–present across all possible intra-arch tooth pairs, the frequencies of sequence polymorphisms were calculated and expressed as percentages in and arch-specific matrices. Results. Sequence polymorphisms were more common in tooth pairs in phase II than in phase I of permanent tooth emergence and only rarely did teeth in phase I reverse sequence with teeth in phase II. In addition, maxillary and mandibular polymorphisms were most common in the sequences of canine–second premolar and first premolar–canine, respectively. Furthermore, central incisor–first molar and second molar–second premolar sequences were much more common in the mandible than in the maxilla. It was noticed that males and females had more similar frequencies of polymorphic sequences in the maxillary than in the mandibular tooth pairs. Conclusions. This study presented the norms of pairwise sequence polymorphisms in permanent tooth emergence in the Jordanians. Such norms are adequately useful for the evaluation and prediction of tooth emergence sequence in individual children and valuable in the assessment of emergence sequence problems in pediatric dentistry and in planning and following-up orthodontic treatment.     

Hypodontia and hyperdontia of permanent teeth in Hong Kong schoolchildren

This study was performed to determine the prevalence of hypodontia and hyperdontia of permanent teeth amongst Southern Chinese children in Hong Kong. The sample consisted of 1093 12-yr-old children on whom a panoramic radiograph was taken. The prevalence of congenitally missing teeth (third molars excluded) was 6.1% in boys, 7.7% in girls, and 6.9% for both sexes combined. On the average, each child was missing 1.5 teeth. The most commonly absent tooth was the mandibular incisor, affecting 58.7% of the children with hypodontia. Thirty children (2.7%) had supernumerary teeth, with a male:female ratio of 6.5:1; in four cases the tooth had erupted. Three children had fourth molars and one case of a supplemental premolar was recorded (all unerupted). Four cases of a maxillary supernumerary tooth and hypodontia in the mandible were seen.     

Emergence of permanent teeth in Tanzanian children

OBJECTIVE: The aim of the present study was to investigate the emergence of permanent teeth among Tanzanian children. METHODS: A total of 869 Tanzanian children were recruited from 16 schools in age groups 3.5-5, 6.5-8, 9.5-11 and 15-16 years of whom 428 (49%) were boys and 441 (51%) were girls. The effects of age and gender on the emergence stages of the dentition were determined for the four age groups. RESULTS: Girls, but not boys, had some permanent maxillary canines, second premolars and mandibular and maxillary second molars as early as at the age of 6.5-8 years. Permanent teeth of both the first and the second transitional periods were already emerging at the age of 3.5-5 years and 6.5-8 years, respectively. At 3.5-5 years, 9% of the permanent teeth belonging to the first transitional period were already in occlusion. Emergence of incisors and first molars was more advanced in girls than in boys in age groups 3.5-5 and 6.5-8 years. CONCLUSIONS: Parallel to earlier reports on different ethnic groups, the results of this study indicate that the permanent teeth of Tanzanian children erupt earlier in girls than in boys, and the mandibular teeth erupt earlier than the corresponding maxillary teeth. The difference between boys and girls was found in both the first and second transitional period. Permanent teeth in Tanzanian children clearly emerge earlier than in Caucasian children.     

Radiographic observations on root resorption in the primary dentition.

In order to construct standardized charts for root resorption in the primary dentition of Japanese children, we investigated the stages of resorption (1/4, 1/2 and 3/4 of the root) based on the criterion of Fanning, et al. using 11,167 panoramic radiographs (5,759 of boys and 5,408 of girls). The following information was obtained. 1) The root resorption for a tooth on one side was the same as for its counterpart on the other side regardless of differences in sex or arch. 2) The average age for each root resorption stage was lower in girls than in boys regardless of differences in sex or arch. 3) The average age for each root resorption stage was lower in the mandible than in the maxilla for every tooth. 4) In the maxilla, the period between 1/4 to 3/4 resorption of the root was greater in the primary molars than in the primary anterior teeth. However, the opposite was true in the mandible. 5) Although no difference was observed between the maxilla and the mandible in the resorption period for the primary incisors and canines, the resorption time for the primary molars was greater in the maxilla than in the mandible. 6) When the relationship was observed between the resorption stages for each tooth and the calcification stages for the corresponding successional permanent tooth. a) With the exception of the maxillary and mandibular canines, the average age for 1/4 resorption of the primary root corresponded to the period between completion of the permanent crown and initial root formation of the successional permanent tooth. b) With the exception of the maxillary and mandibular canines, and the mandibular second premolars, the average age for 3/4 resorption of the primary root corresponded to the period between 1/4 and 1/2 formation of the root of the successional permanent tooth. From these results, standardized charts were constructed for the resorption of the roots of primary teeth in Japanese children. These standardized charts are useful in daily clinical practice in such areas as endodontic treatment of primary teeth and orthodontics.     

Time of permanent teeth eruption in schoolchildren of Saint-Petersburg

The terms of permanent teeth eruption were analyzed in 909 children (permanent residents of St. Petersburg) aged 7-15 years. The study showed that all groups of permanent teeth, except the first molars, erupted on the mandible earlier than on the maxilla. In girls only canines and second molars erupted earlier than in boys. There was virtually no sex-specific difference in the terms of eruption of both premolars, and the terms of the end of eruption of both groups of canines were virtually the same in boys and girls. Twenty-one children lacked some of permanent teeth by 15 years (the age considered as the upper threshold level for the end of normal tooth eruption). The most frequent teeth that failed to erupt in time were the upper lateral canines (33.3% of all teeth which failed to erupt by the age of 15 years), lower central canines and upper first premolars and molars (12.8% each).     

Emergence of permanent teeth: secular trends and variance in a modern sample

The purpose of this study was to update the most commonly used tables of dental eruption (emergence), which are more than 50 years old and do not distinguish between ethnic and socio-economic groups. Clinical emergence data was collected for a modern sample of 574 French children and adolescents, aged 5.5 years to 15 years (294 girls and 280 boys). With respect to the present sample, the commonly used eruption tables of Hurme were accurate for most aspects of mandibular emergence, but were seriously flawed for the maxillary arch. Emergence of all permanent maxillary teeth varied by at least 3 months from Hurme's means; lateral incisors, canines, and second molars erupted earlier, but both premolars emerged later. Compared to similar French data collected in 1958, there appears to be a secular trend for later eruption of the maxillary premolars and earlier emergence of permanent second molars. These changes may reflect an evolutionary reduction in the size of the maxilla, a progressive decrease in genetic control of permanent canines, as well as first and second premolars, and/or progress in dental preventive measures to conserve primary molars. From a clinical perspective, appropriate dental emergence data are essential for effectively intercepting developmental malocclusions in children and adolescents.     

Timing of permanent tooth emergence in Danish children

abstract Mean times of emergence of the permanent teeth, except the third molars, and mean times of onset of specific dental stages were studied cross-sectionally in nearly 8,000 Danish children. In both sexes, a tendency for grouped emergence was observed, the teeth within a group showing similar mean times of emergence. The following groups were distinguishable: (1) the first molar in each jaw and the mandibular central incisor, (2) the maxillary central and mandibular lateral incisor, (3) the mandibular canine and the first premolar in each jaw, and (4) the maxillary canine and the second premolar in each jaw. The sex difference in emergence timing ranged from 2–11 months. In Denmark, the first visit to the Child Dental Services usually takes place when the children enter school in the year they attain the age of 7 years. The present findings indicate that, in order to include the initial phase of permanent tooth emergence, organized dental care should be introduced at least 1 year earlier.     

Timing of permanent tooth emergence in Danish children

abstract Mean times of emergence of the permanent teeth, except the third molars, and mean times of onset of specific dental stages were studied cross-sectionally in nearly 8,000 Danish children. In both sexes, a tendency for grouped emergence was observed, the teeth within a group showing similar mean times of emergence. The following groups were distinguishable: (1) the first molar in each jaw and the mandibular central incisor, (2) the maxillary central and mandibular lateral incisor, (3) the mandibular canine and the first premolar in each jaw, and (4) the maxillary canine and the second premolar in each jaw. The sex difference in emergence timing ranged from 2–11 months. In Denmark, the first visit to the Child Dental Services usually takes place when the children enter school in the year they attain the age of 7 years. The present findings indicate that, in order to include the initial phase of permanent tooth emergence, organized dental care should be introduced at least 1 year earlier.     

A prospective cohort study on emergence of permanent teeth and caries experience in Korean children

International Journal of Paediatric Dentistry 2011; 21: 254–260 Objectives. The objectives of this study were to investigate permanent tooth emergence during a 9‐year longitudinal study and to assess the effect of dental caries in primary teeth on the emergence of permanent teeth. Methods. Data on caries occurrence in primary teeth were obtained at the baseline by a trained dentist. Permanent tooth emergence data of 539 students from 16 elementary schools in Yeoncheon were examined annually from 1995 to 2003 using dental casts. The median age at emergence of the teeth was calculated using a linear logistic regression model. A multiple linear regression model was used to evaluate the effect of caries on the emergence of permanent teeth. Results. The age of permanent tooth emergence was different between boys and girls, but the difference was not statistically significant at the 5% level. Having ‘decayed teeth’ hastened the emergence of most second premolars and second molars, whereas the regression coefficients ranged from ?1.23 to ?0.82. The number of ‘filled teeth’ showed a correlation with maxillary second premolars and mandibular first premolar, and the regression coefficients ranged from ?1.92 to ?3.25. Conclusions. Having dental caries in primary teeth can be a strong predictor of earlier emergence of permanent teeth.     

Dental caries prevalence and CPITN of 12-year-old rural schoolchildren in Transkei

The study investigated the prevalence and pattern of caries with particular reference to tooth and surface type and the CPITN of 12-y-old rural schoolchildren in Engcobo, Transkei. 349 schoolchildren, with a 4:6 male:female ratio were examined. The fluoride content of the water varied from 0-0.5 p.p.m. The results indicate that caries levels are low--47 per cent of the sample was caries-free. Both the median DMFT and DMFS was 1.0 (with a mean 1.7 and 2.8). The D component comprised 89 per cent, the M-10 and F-1 per cent of the total DMFT. Amongst boys, caries was distributed almost equally between the maxillary (112) and mandibular (114) arches whereas for girls more teeth were affected in the mandibular arch. Molar teeth in boys and girls accounted for 90 per cent of all teeth affected with the first molars accounting for 50 per cent and the second molars 40 per cent. In the maxillary and mandibular arch for the total group, a greater number of first molars were affected than the second molars. For girls in both the maxilla and mandible, the second molars were affected more frequently than the first molars. Overall the occlusal surfaces were affected most frequently followed by the buccal, distal, lingual and mesial. Gingival bleeding and calculus were prevalent in most sextants. Less than 6 per cent of the total subjects had no periodontal disease. Calculus was found in over 70 per cent of the children. The vast majority of the sample (94 per cent) needed oral hygiene instruction.     

Development of permanent tooth length in patients with unilateral cleft lip and palate

The aim of this study was to compare permanent tooth length development in children with complete unilateral clefts of the lip, alveolus, and palate (UCLP) with that of tooth length development in a normal reference population. From the data of the Cleft Palate Clinics of Amsterdam and Nymegen (The Netherlands), 350 orthopantomograms of 64 boys and 24 girls with complete UCLP were selected. The control data were taken from approximately 2000 orthopantomograms collected from 180 boys and 157 girls in the same age range. For canines, premolars, and molars in the mandible, and for canines and second premolars in the maxilla, three to six landmarks were digitized directly from the orthopantomograms. It was concluded that, for both boys and girls, development of permanent tooth length in children with complete UCLP is significantly delayed, compared with the normal reference population. This significant difference was found in the maxilla as well as in the mandible.     

A survey of hypodontia in Japanese orthodontic patients.

INTRODUCTION: The purpose of this retrospective study was to assess the prevalence and distribution of hypodontia in the permanent dentition, excluding the third molars, in a sample of Japanese orthodontic patients. METHODS: Orthopantomograms of 3358 Japanese orthodontic patients (1453 boys and 1905 girls) between the ages of 5 and 15 years were examined for evidence of hypodontia. RESULTS: The prevalence of hypodontia was 8.5% (7.5% for boys, 9.3% for girls) with no statistically significant difference between the sexes. The average number of missing teeth per child was 2.4 (2.5 for boys, 2.4 for girls). Most (76.3%) children with hypodontia were missing either 1 or 2 teeth (77.1% for boys, 75.7% for girls). The prevalence of advanced hypodontia was 10.1% (11.0% for boys, 9.7% for girls). The most commonly missing teeth were the mandibular second premolars, followed by the mandibular and maxillary lateral incisors, and the maxillary second premolars; minor differences in the order of prevalence existed among groups of children classified by the number of missing teeth. Symmetrical hypodontia was predominant, and the most commonly symmetrical hypodontia was mandibular second premolar agenesis. No consistent finding was obtained as to which jaw had more missing teeth. The distribution of missing teeth was similar between the right and left sides of the dental arches in each group of children. Anterior tooth agenesis was predominant in children with minor hypodontia, and posterior tooth agenesis increased with hypodontia severity. CONCLUSIONS: The distinct characteristic of hypodontia in the Japanese population compared with other populations was a higher prevalence of both advanced hypodontia and mandibular lateral incisor agenesis in children with minor hypodontia.     

Timing of permanent tooth emergence in a Southeastern Dominican schoolchildren population sample

Abstract The purpose of this study was to establish the mean timing of permanent tooth emergence in a low to middle socioeconomic level schoolchildren population sample from the Southeastern part of the Dominican Republic. A total of 900 children (15.6%of the 5–14-year-old schoolchildren from this city) were studied. Girls were relatively advanced in their emergence times except for the canine and second premolar in the maxilla and the first premolar in the mandible. The mean emergence times were, in general, relatively advanced when compared with those of United States whites and blacks, Danish, Canadian Eskimos, French-Canadians, Greenland Eskimos, Icelandics, Southern Chinese and South Africans.     

A longitudinal study on growth and development of dental arches of primary, mixed and permanent dentitions

In dental clinic for children, criteria for growth and developmental changes related to increases in the width and length of the dental arch at the primary, mixed, and permanent dentition stages are essential. This study was carried out to measure the width and the length of normal dental arch and to make detailed observations of growth and developmental processes in the dental arch at each dentition stage. Materials were serial study casts of the maxilla and the mandible taken every 2 month from 127 children (74 boys and 54 girls). The casts were made from 6 months after birth until the age of 15. Measurements of the width of the dental arch were made between bilateral teeth of the same tooth type, both deciduous and permanent. The length of the dental arch was measured on the basis of the perpendicular distance from the contact point of mesial surfaces of central incisors to a line between bilateral teeth of the same tooth type. Measured values were categorized according to either chronological age or tooth age on the basis of the eruption of the central permanent incisors. The indices of the dental arch with relation to the width and the length at each dentition stage were calculated for the sake of partial and total observations of alterations in dental arch form. The results were as follows: 1) In terms of chronological age, until 1 year before the eruption of permanent replacements, the width of the dental arch gradually decreased in both the maxilla and the mandible in the regions of the deciduous central and lateral incisors. Increasing slightly from about the age of 6 years and the period of mixed dentition, the width of the dental arch remained stable until the permanent dentition stage. From the primary dentition stage, the width of the dental arch in the region of the maxillary and mandibular canines and first and second molars gradually increased. Therefore it remained stable until the eruption of permanent dentition. The width in the region of the permanent maxillary and mandibular first molars gradually increased and attained a stable condition at about 12 years of age. In males, the width in the area of the maxillary secondary molars decreased slightly and tended to decrease in the mandible. In females, on the other hand, the width showed a tendency to increase with advancing ages. With the exception of the second permanent molars, the width between the distance of bilateral teeth were consistently larger in males than in females.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparison of normal permanent and primary dentition sagittal tooth-crown inclinations of Japanese females

The purpose of this study was to clarify the characteristics of permanent and primary tooth-crown inclinations. Landmark points from cephalograms and dental casts of two groups; 23 women (mean 20.3 +/- 3.3 years) and 11 girls (mean 5.2 +/- 0.1 years) were digitized, and the coordinates were integrated and transformed to a standardized plane. The 3-dimensional crown inclinations were projected on the sagittal plane, and the angles between the tooth vectors and the FH plane were calculated. An independent-group t-test was used to test for group differences of each tooth inclination, and correlation coefficients were generated for the inclination angles among the permanent and primary teeth. Most maxillary tooth-crown inclinations showed significant age-related differences, while only the second premolar and primary second molar differed significantly in the mandible. The maxillary molars were parallel to the corresponding mandibular molars and correlated with each other, but the primary molars were not. Significant correlations were found between inclinations of most permanent teeth, but not the primary teeth. Maxillary tooth-crown inclinations change during growth, but tooth-crown inclinations of the mandibular teeth do not.     

An epidemiological survey of the time and sequence of eruption of permanent teeth in 4-15-year-olds in Tehran, Iran

AIM: The aims of this study were to define the average time of eruption of permanent teeth, the range of variation of the eruption time of each tooth, and their sequence of eruption amongst boys and girls in Tehran, Iran. METHODS: The population under study comprised 3744 pupils and students in the 4-15-year-old age group (1786 girls and 1958 boys) who were randomly selected from schools and training centres in the 20 districts covered by the General Department of Education and Training in Tehran. The research was carried out on a cross-sectional basis. The average age at eruption of permanent teeth, excluding third molars, was given as the mean (+/- SD) and median in months for each gender. A table of percentiles of the eruption time was also determined. RESULTS: The results show that, with the exception of the maxillary second premolars, the average age at eruption of permanent teeth in girls is less than in boys. The results also show that mandibular teeth have an earlier eruption time than maxillary teeth in both boys and girls. By the age of 96 months, 97% of the girls had all their first permanent molars. In boys, the corresponding age was 99 months. Amongst girls, maxillary canines erupt earlier than maxillary second premolars. CONCLUSION: On average, girls have their permanent teeth erupt earlier than boys. The sequence of eruption differs between girls and boys for maxillary canines and maxillary second premolars.     

Simultaneous presence of a congenitally missing premolar and supernumerary incisor in the same jaw: report of case

Supernumerary teeth and hypodontia can be regarded as opposite developmental phenomena. An eight-year-old girl presented a concomitant occurrence of a supernumerary tooth and two congenitally missing teeth. The supernumerary tooth was found in the left maxillary incisor region, while the left second premolar in the maxilla and the left lateral incisor in the mandible were congenitally missing. The supernumerary tooth showed a similar color and morphology to those of the maxilla lateral incisor, and the lateral incisor on the mesial side was diagnosed as a supernumerary tooth from dental age, eruption time, and mesiodistal crown dimension. The supernumerary incisor was guided labially to cure an anterior cross-bite, and the lateral incisor, canine, and first premolar were guided distally to compensate for the space left by the congenitally missing left second premolar.     

Multiple supernumerary teeth in the maxillary canine and mandibular premolar regions: a case in the postpermanent dentition

BACKGROUND: A supernumerary tooth is an extra tooth above the normal number, of which approximately 90% occur in the premaxillary region and show rudimentary forms of crown morphology. Most cases occur singly, with bilateral occurrence in the maxillary canine regions very rare in children with no other associated diseases or syndromes. CASE REPORT: A case of a 14-year-old boy with bilateral supernumerary teeth with normal crown shapes in both the maxillary canine and mandibular premolar regions. The supernumerary teeth in the maxilla were diagnosed at 12.2 years of age and in the mandible at 14.1 years of age. CONCLUSION: Four supernumerary teeth in the maxillary and mandibular canine-premolar region is a rare finding.     

Prevalence of hypodontia and malformations of permanent teeth in Iceland

This study was performed to elucidate the prevalence of hypodontia and congenital malformations of permanent teeth in Iceland. Computer analysis was done on the basis of results from examining 1,116 children (521 boys and 595 girls), or about 9.5% of all schoolchildren in Reykjavík in stages DS 3 (canines and premolars erupting) and DS 4 (canines and premolars fully erupted) of dental development at the time of the study. The age range was mainly from 8-16 years. The prevalence of congenitally missing teeth (second and third molars excluded) was 6.7% in boys and somewhat higher, 8.9%, in girls, 7.9% for both sexes combined. On the average, each child was missing 1.9 teeth. In the girls, the most commonly absent teeth were the mandibular second premolar (55%), the maxillary second premolar (19%), and the maxillary lateral incisors (18%). In the boys the figures were 51%, 18%, and 10%, respectively. Malformation of permanent teeth, mainly in the form of pegshaped maxillary laterals, was also less common in the boys, 1.3% against 3.0% in the girls, and 2.2% for both sexes combined. Among Icelandic children hypodontia and/or congenital malformation of permanent teeth were found in 9.1%.