Hypodontia in 9-year-old Norwegians related to need of orthodontic treatment

The present study reports on the prevalence of hypodontia in a Norwegian population and classifies children with hypodontia according to need of orthodontic treatment. Orthopantomograms of 1953 children (960 girls and 993 boys) at the age of 9 were available for examination. Of the boys registered with hypodontia of second premolars at the age of 9, 11.3% showed late mineralization between the ages of 9 and 12. Only 2.9% of the girls showed late mineralization. The corrected prevalence of hypodontia, excluding third molars, in the girls was 7.2%, in the boys 5.8%, and in both sexes combined 6.5%, the difference between sexes not being statistically significant. Of the children with hypodontia, 86.6% lacked only one or two permanent teeth. The most frequently missing teeth were the mandibular second premolars, the maxillary second premolars, and the maxillary lateral incisors, in that order. Classification of children with hypodontia according to need of orthodontic treatment showed that about two-thirds had hypodontia only of single posterior teeth with a moderate need of treatment. About one-third had hypodontia involving anterior teeth, and only 3.1% had hypodontia of two or more teeth in the same quadrant with a great need of treatment.     

Hypodontia of permanent teeth in Danish schoolchildren

Hypodontia, congenitally missing teeth, is one of the conditions recorded during systematic orthodontic screening of groups of children attending a community child dental health service. The present investigation reports the prevalence of hypodontia in 3325 9–10-year-old children in the 3rd schoolgrade examined with an orthopantornographic radiograph. The prevalence of children with hypodontia was found to be 7.8%. Fifty percent of these children were missing only one tooth while 85% were missing either one or two teeth. More teeth were missing in the mandible than in the maxilla. The teeth most frequently missing were the second premolars, representing 67% of the congenitally missing teeth. Symmetrical hypodontia of second premolars occurred approximately twice as often in girls as in boys. Though more teeth were congenitally missing in girls than in boys, no difference could be seen in the prevalence of hypodontia in boys (7.7%) and girls (7.8%).     

Hypodontia in children with various types of clefts

The prevalence of hypodontia in children with clefts, both inside and outside the cleft region, and the possible association between the side of the cleft and the side of the missing teeth were studied using radiographs of 278 patients with cleft lip, cleft palate, or both (158 boys and 120 girls), age 5 to 18 years (mean age 10.4 years). A hypodontia prevalence of 77% (excluding third molars) was found for the total cleft sample. This was significantly higher, both statistically and clinically, than the incidence of hypodontia reported for noncleft populations, and considerably higher than the prevalence reported in other studies of children with clefts. The maxillary permanent lateral incisors were the teeth most frequently missing on the cleft side (259 teeth) followed by the maxillary (47 teeth) and mandibular (23 teeth) second premolars, in both boys and girls. The teeth that were most often missing on the noncleft side were the maxillary second premolars (12 teeth), followed by the maxillary lateral incisors (10 teeth) and mandibular second premolars (6 teeth). Hypodontia of both the maxillary lateral incisors and second premolars was found more frequently on the left side, which also has a higher frequency of clefting.     

Patterns of tooth agenesis in Japanese subjects with bilateral agenesis of mandibular second premolars

The aim of this study was to explore the patterns of tooth agenesis in Japanese orthodontic patients with bilateral agenesis of mandibular second premolars. A total of 80 Japanese orthodontic patients with 2 congenitally missing mandibular second premolars were selected as the subjects of this study (experimental group). Another 80 individuals without bilateral agenesis of mandibular second premolars were collected for comparison (control group). The 2 groups were matched with regard to sex. Radiographs, dental casts and records of medical and/or dental treatment were used to identify tooth agenesis. The Chi-square test, odds ratio, and test for equality were used to make statistical comparisons. The prevalence rates of other types of tooth agenesis were significantly higher in the experimental group than in the control group. The occurrence of agenesis of maxillary and mandibular lateral incisors and third molars, and maxillary second premolars was also significantly higher in the experimental group than in the control group. Significantly increased prevalence rates of symmetrical tooth agenesis, with third molars included, and oligodontia were observed in the experimental group. Japanese subjects with bilateral agenesis of mandibular second premolars are at significantly high risk of agenesis of other types of permanent teeth, symmetrical tooth agenesis and oligodontia.     

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%.     

儿童口腔科门诊先天缺牙患者临床特征和发病因素研究

目的    研究儿童口腔科门诊先天缺牙患者的临床特征和可能影响发病的因素。方法    对2014年1—12月于中国医科大学附属口腔医院儿童口腔科就诊的16 320例患者进行先天缺牙的临床调查,针对先天缺牙的部位、数目及可能影响发病的因素等进行分析。结果    326例患者确诊为先天缺牙,占调查患者人数的2.0 %。其中,多数牙缺失患者44例,平均缺牙数为（7.98 ± 2.98）颗;个别牙缺失患者282例,平均缺牙数为（2.09 ± 1.04）颗。多数牙缺失患者中具有家族遗传史者所占比例明显高于个别牙缺失患者。缺牙好发部位依次为下颌第二前磨牙、上颌第二前磨牙、上颌侧切牙、下颌中切牙、第一前磨牙、上颌尖牙。采用非条件Logistic回归对先天缺牙的可能影响因素进行分析,发现家族史是先天缺牙的危险因素（P < 0.01）,而患者父母的文化程度、母亲受孕年龄、母亲妊娠期放射线接触史及是否为早产儿等因素,均不是先天缺牙的影响因素（P > 0.05）。结论    先天缺牙多为个别牙缺失,好发部位主要为下颌第二前磨牙;多数牙缺失可能与家族遗传密切相关。     

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??Objective    To investigate the clinical characteristics and possible related factors of tooth agenesis in the patients in the pediatric dentistry. Methods    A total of 16320 children?? who came to Pediatric Dentistry Clinic of Stomatology Hospital affiliated to China Medical University from January to December in 2014?? were examined. The number?? position and the influencing factors were analyzed. Results    Totally 326 children were diagnosed with tooth agenesis?? accounting for 2.0%. Among these patients?? 44 were oligodontia with the average number of missing teeth at 7.98 ± 2.98?? 282 were hypodontia with the average number of missing teeth at 2.09 ± 1.04. The proportion of children with family history in oligodontia was significantly higher than that in hypodontia. Most of the missing teeth were located in the second mandibular premolar?? followed by the second maxillary premolar?? maxillary lateral incisor?? mandibular central incisors?? the first molar and maxillary cuspid. Influencing factors for tooth agenesis were analyzed by non-conditional Logistic regression. Family history was a risk factor for congenital missing teeth ??P < 0.01??. Parents' educational level?? pregnancy age?? history of radiation exposure during pregnancy and preterm birth were not the influencing factors for tooth agenesis ??P > 0.05??. Conclusion    Hypodontia is the most common type of tooth agenesis and the second mandibular premolars are predominantly affected. Oligodontia might be closely relate to genetic factor.     

Non-syndromic hypodontia in an Iranian orthodontic population

To investigate the prevalence, characteristics (ie, malocclusion, location, type), and sex distribution of hypodontia in an Iranian orthodontic population. A retrospective study was conducted using periapical and panoramic radiographs and study models of 1,751 subjects attending university orthodontic clinics (870 females, 881 males, age 9-27 years). The Chi-square test was used to analyze differences in the distribution of hypodontia, after stratification by sex and malocclusion type. A total of 197 congenitally missing teeth were observed in 160 patients (9.1%; 74 boys and 86 girls); there were no statistically significant differences between sexes (Chi-square = 0.832, P = 0.36). Hypodontia was more common in patients with Class III malocclusion (45.2%), and was more prevalent in the maxilla (71%) than in the mandible (29%). Maxillary lateral incisors (35.6%) and maxillary second premolars (13.0%) were the most commonly missing teeth, followed by mandibular lateral incisors (9.6%) and mandibular second premolars (8.2%). The prevalence of missing teeth was higher in the anterior segment (incisors and canines) than in the posterior segment (premolars and molars). The prevalence of oligodontia was 0.34%. The prevalence and characteristics of the most frequently missing teeth accorded with the findings of most studies conducted in other countries.     

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.     

Agenesis of permanent teeth in 8138 Danish schoolchildren: prevalence and intra-oral distribution according to gender

Objective.  The purpose of this study was to describe agenesis of permanent teeth in children with respect to prevalence and intra-oral distribution according to gender.
Methods and subjects.  The study was population based and included all children in one district of the municipality of Aarhus, Denmark, in 1974–1979 (1657 girls and 1668 boys) and 1992–2002 (2409 girls and 2404 boys). The children underwent systematical clinical and radiographic examination.
Results.  The period prevalence rates were almost identical for the two time periods (1972–1979: 7.8%; 1992–2002: 7.1%). Girls were affected more frequently than boys, and affected girls had more congenitally missing teeth than affected boys. Unilateral agenesis of the second premolars was more frequent than bilateral agenesis. In children with only one congenitally missing tooth, agenesis of the upper lateral incisors was asymmetrical in girls, but not in boys, whereas the opposite was true for the lower second premolars in boys.
Conclusion.  The prevalence of agenesis of permanent teeth in Danish schoolchildren seems to be constant over time, and similar to that found in other large, population-based studies. Intra-oral distributions of congenitally missing teeth indicate gender-specific patterns.     

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目的调查分析大连地区正畸患者恒牙先天缺失的发生率及分布,包括第三磨牙。方法随机抽取2008年7月至2011年6月来大连市口腔医院就诊的正畸患者800例(男260例,女540例;年龄9～40岁),通过观察其全颌曲面断层片,分析恒牙先天缺失的发生率及分布。结果包括第三磨牙在内的恒牙先天缺失发生率为36.13%,除第三磨牙外的恒牙先天缺失发生率为12.5%。性别间差异无统计学意义(P>0.05)。除第三磨牙外的轻度先天缺牙例数(缺失1～2颗牙)占87%,中度先天缺牙例数(缺失3～5颗牙)占10%,重度先天缺牙例数(缺失牙≥6颗)占3%。常见的缺失牙位因缺牙程度的不同而不同,轻度缺失时,最常见的缺失牙位在前牙(最多见的是右下侧切牙),随着缺牙程度的加重,常见的缺失牙位在后牙(最常见的是下颌第二前磨牙)。上、下颌的缺牙情况是,轻度缺牙(缺失1～2颗)时,下颌的发生率高于上颌;中、重度缺牙时,上、下颌之间差异无统计学意义(P>0.05)。上、下牙弓左右侧的缺牙发生率差异无统计学意义(P>0.05)。缺失牙≥2颗时,对称缺失占大多数,最常见的对称缺失牙位是下颌第二前磨牙。结论除第三磨牙外,大连地区正畸患者最常见的缺失牙位是下颌侧切牙;随先天缺牙程度加重,则以下颌第二前磨牙先天缺失最常见。     

Patterns of bilateral agenesis of maxillary third molars and agenesis of other teeth

The purpose of this study was to investigate the patterns of bilateral agenesis of maxillary third molars and other tooth agenesis in Japanese orthodontic patients. A group of 262 subjects with bilateral agenesis of maxillary third molars (group A) was divided into three subgroups: group 1A consisting of 114 subjects without agenesis of mandibular third molars; group 2A, 31 subjects with unilateral agenesis of mandibular third molars; and group 3A, 117 subjects with agenesis of all third molars. As controls, 926 other subjects without third molar agenesis were selected (group C). Panoramic radiographs were mainly used to examine for tooth agenesis. The Chi square test and odds ratio were used to make statistical comparisons. The prevalence rates of agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, and bilateral agenesis of maxillary lateral incisors and second premolars were significantly higher in any one of the third molar agenesis groups than in the control group. Characteristically, no significant increase in occurrence of bilateral agenesis of mandibular second premolars was demonstrated by the subjects with bilateral agenesis of maxillary third molars. Irrespective of whether unilateral or bilateral agenesis of mandibular third molars is present or not, the Japanese orthodontic patients with bilateral agenesis of maxillary third molars exhibited a significantly increased occurrence of unilateral or bilateral agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, except for bilateral agenesis of mandibular incisors and second premolars.     

石家庄地区正畸患者恒牙先天缺失的调查分析

目的调查分析石家庄地区正畸患者恒牙先天缺失的发病率及特征。方法对河北医科大学口腔医院正畸科2010~2012年正畸患者中3274名有效病例的病历资料进行回顾分析。通过观察其全颌曲面断层片,分析恒牙先天缺失的发病率及分布差异。结果除第三磨牙外恒牙先天缺失的发病率为9.13,性别间差异无统计学意义（P〉0.05）。个别缺牙例数（缺牙数〈6）占总缺牙例数的95,其中缺失1~2颗牙的例数占总缺牙例数的88.6;多数缺牙例数（缺牙数≥6）占总缺牙例数的5。前、后牙区的缺牙发病情况在缺失1~2颗牙时,主要发生在前牙区,缺失2颗以上时,后牙区的缺失发病率高于前牙区（P〈0.05）;下颌缺牙发病率高于上颌（P〈0.05）。缺牙频率最高的是下颌侧切牙（25.3）,其次是下颌第二前磨牙（18.3）。结论石家庄地区正畸患者恒牙先天缺失（不包括第三磨牙）发病率为9.13,。其中以缺失1~2颗牙最常见,恒牙先天缺失更多的发生在前牙区及下颌,最常见的缺失牙位是下颌侧切牙和下颌第二前磨牙。     

800例正畸患者中先天缺失牙及其与多生牙、锥形牙相关性分析

目的：观察正畸患者中伴有恒牙先天缺失、多生牙和锥形牙或过小牙的发生率及分布,并分析其相关性。方法：随机抽取正畸患者800例,男260例,女540例,年龄12-40岁。通过石膏模型和曲面断层片统计先天缺牙、多生牙、锥形牙或过小牙的发生率及分布。通过分类变量的关联性来分析多生牙和锥形牙或过小牙与先天缺牙的相关性,假设检验采用列联表的独立性x2检验,并采用Pearson列联系数r来描述两变量关联程度。结果：800例中发生恒牙先天缺失100例,发生率为12．5％。常见的缺失牙位从多到少依次为下颌侧切牙、下颌第二前磨牙、下颌中切牙、上颌侧切牙、上颌第二前磨牙。多生牙的发生率为3．1％,锥形牙或过小牙占8．3％。通过分类变量的关联性分析得出,锥形牙或过小牙的发生与先天缺牙有相关性,Pearson列联系数r为0．173。结论：正畸患者中恒牙先天缺失的发生率为12．5％,最常见的缺失牙位是下颌侧切牙和下颌第二前磨牙;正畸患者中恒牙先天缺失和锥形牙或过小牙的发生具有相关性。     

Maxillary first molar agenesis and other dental anomalies

Objective: To explore the association of maxillary first molar agenesis with other dental anomalies in Japanese orthodontic patients.Materials and Methods:A total of 32 subjects with one or two congenitally missing maxillary first molars (group M) were selected and divided into group 1M (12 subjects with one maxillary first molar missing) and group 2M (20 subjects with two maxillary first molars missing). As controls, 32 sex-matched subjects without agenesis of maxillary first molars were collected (group C). Panoramic and periapical radiographs, cephalograms, study models, intraoral photographs, and anamnestic data were used to identify anomalies of permanent teeth. Chi-square, Fisher''s exact, Kruskal-Wallis, and Steel-Dwass tests were used to make statistical comparisons.Results:The prevalence rates of tooth agenesis other than the maxillary first molars and advanced tooth agenesis, with third molars excluded, were significantly higher in group 2M than in group C. The absence of second premolars was most common. The prevalence rate of third molar agenesis was significantly higher in groups 1M and 2M than in group C. The occurrence of symmetrical agenesis of the mandibular third molars was particularly notable in group 2M as compared to group 1M, in which maxillary third molar agenesis was predominant. There was no significant association between maxillary first molar agenesis and other dental anomalies, except for agenesis of teeth other than maxillary first molars.Conclusion:Agenesis of maxillary first molars is associated with a higher prevalence of other permanent tooth agenesis and advanced tooth agenesis.     

An orthopantomographic study of hypodontia in permanent teeth of Japanese pediatric patients

Hypodontia of permanent teeth was evaluated from orthopantomograms of 2072 apparently healthy pediatric patients at The Hospital of Nihon University School of Dentistry at Matsudo. The prevalence of congenitally missing teeth (CMT) was 8.7% in boys and 10.8% in girls, and 9.4% for both sexes combined. Most cases (67.8%) involved either one or two missing teeth. There were in total 574 CMT, and on average 2.8 teeth were missing per child. The most commonly absent tooth was the mandibular second premolar. On the other hand, no first molars were missing in any case. A high frequency of CMT mandibular incisors (18.82%) was observed, and this seems to be a characteristic peculiar to individuals of Asian ethnicity. Oligodontia (6 or more CMT excluding the third molar) ranged from 6 to 14 teeth, with a prevalence of 1.4% in general: 1.8% for girls and 0.9% for boys. Symmetry of CMT was predominant: 214 pairs for bilateral symmetry and 107 pairs for symmetry between two antagonistic quadrants. The distribution of CMT between maxillary and mandibular hypodontia in the right and left quadrants for boys and girls no had significant association (P < 0.05).     

Dental development and tooth agenesis in children with velocardiofacial syndrome

BACKGROUND. Variations in dental development and tooth agenesis have been reported in children with velocardiofacial syndrome (VCFS). AIM. The aim was to evaluate the dental development and missing permanent teeth in children with VCFS. DESIGN. Forty-five children (23 girls) with VCFS who had visited the cleft palate and craniofacial centre were studied retrospectively from orthopantomograms taken at the mean age of 7.9 years (range 5.8-12.9). Thirteen of the children with VCFS had palatal clefts. The deletion of 22q11 was verified by FISH techniques. The dental stages were assessed by the method of Demirjian, and the dental age was calculated according to the Finnish dental maturity reference values. A paired Student's t-test was used in the statistical analysis. RESULTS. Eight children (17%), four with palatal clefts, had tooth agenesis. Four children (9%) had agenesis of mandibular incisors. The missing teeth (n = 19) were mainly mandibular incisors (n = 6), maxillary lateral incisors (n = 2), and maxillary second premolars (n = 4). The dental age of the children with VCFS was not different from their chronological age, but there was great individual variation. CONCLUSIONS. A high prevalence of missing permanent teeth, especially mandibular incisors, was observed. The need for thorough clinical and radiological dental examination in children with VCFS is emphasized.     

Dental agenesis patterns in Crouzon syndrome

Dental agenesis may be present in an isolated familiar manner, or occur as a part of a syndrome.To date, this clinical trait seems to have been overlooked in patients with Crouzon syndrome.The aim of the present study was to investigate dental agenesis and dental agenesis patterns in a population of persons with Crouzon syndrome in Sweden. Serial panoramic radiographs of 26 individuals with Crouzon syndrome (20 males, 6 females) were examined.Third molars were excluded from the assessment. The prevalence of agenesis for at least one tooth was 42.3%. Each affected patient was found to have up to 5 missing teeth. Upper and lower second premolars were the most frequently congenitally missing teeth. Eleven dental agenesis patterns of the entire dentition were identified, as described by the tooth agenesis code (TAC). All patterns were unique and asymmetric,with only one exception, a symmetric pattern of the maxillary and mandibular second premolars. In conclusion, persons with Crouzon syndrome were found to have a high prevalence of dental agenesis and a remarkable variability of dental agenesis patterns. It is important to be aware of this clinical situation, especially when orthodontic treatment planning for these patients is performed as early as in the mixed dentition.     

Tooth dimensions in hypodontia patients,their unaffected relatives and a control group measured by a new image analysis system

Tooth dimensions were compared between index patients with severe hypodontia (six or more congenitally missing teeth), their relatives with a full complement of teeth, and a control group. The groups consisted of 12 index cases (seven females and five males), 21 relatives without hypodontia (13 females and eight males), and a control group of 10 males and 10 females with complete dentitions, and no family history of hypodontia. All formed teeth were imaged buccally and occlusally from study models, with a digital camera linked to a computer. The images were acquired and measured using Adobe Photoshop and Image Pro Plus, respectively. Mesiodistal, buccolingual, or occlusogingival area and perimeter measurements were determined from each image. In the index hypodontia group tooth dimensions were significantly smaller (P < 0.001, Bonferroni corrected level) for maxillary and mandibular canines, and first premolars for all dimensions from the buccal view, and for maxillary and mandibular canines and first premolars, maxillary central incisors, maxillary first molars, mandibular lateral incisors, and mandibular second premolars for all dimensions from the occlusal view. In the relatives without hypodontia compared with the control group, mesiodistal dimensions from the buccal view were significantly smaller (P < 0.001) for the central incisors and maxillary first and second premolars, and for the maxillary and mandibular first premolars for all dimensions from the occlusal view. There was a trend for the tooth dimensions of all teeth in the index group to be smaller compared with the control group. The tooth dimensions of the relatives without hypodontia also tended to be smaller than the control group, but were larger than those of the index cases.     

Trends in orthodontic management strategies for patients with congenitally missing lateral incisors and premolars

ObjectivesTo identify changes in orthodontic management strategies in patients with hypodontia seen in 2000, 2010, and 2017/2018 (during a 1-year period).Materials and MethodsAn assessment of the panoramic radiographs of 3701 patients from a Western Australian private practice identified 276 individuals demonstrating hypodontia. The location of missing teeth, age, sex, type of malocclusion, and the management strategies (space closure or opening) for each patient were noted.ResultsMost hypodontia involved agenesis of three or fewer teeth (90%). Maxillary lateral incisors and mandibular second premolars were the most commonly missing teeth. Female preponderance was noted. When considering treatment, the odds ratio for orthodontic space opening and prosthetic replacement in 2000 was 3.266 (P value = 7e-04; 95% confidence interval [CI], 1.464–4.633) compared with patients seen in 2010 and 1.632 (P value = 7e-04; 95% CI, 0.811–2.434) compared with patients in 2017/2018. For patients demonstrating bilateral absence of maxillary lateral incisors, the odds ratio for orthodontic space opening was 3.185 (P value = 0.0215; 95% CI, 1.182–9.243) compared with counterparts with unilateral agenesis. None of the factors investigated were significantly associated with the types of treatment planned/provided for the patients with missing mandibular second premolars.ConclusionsMaxillary lateral incisors and mandibular second premolars were the most commonly missing teeth. A trend away from space opening and prosthetic replacement toward orthodontic space closure was observed from 2000 to 2017/2018. This may reflect a change in attitude toward prosthetic replacement options and/or greater optimism with biomechanical strategies since the implementation of temporary anchorage devices to assist in space closure.