Mesial Step Research Articles

Evaluation of the Occlusion and Arch Dimensions in the Primary Dentition of an Iranian Population

Introduction: The objective of this study was to gather information about normal occlusion and arch dimensions in the primary teeth of the children belonging to an Iranian population. Methods: This descriptive cross-sectional study was performed on 68 children from the city of Mashhad in the 3-5 age range. Dental arch dimensions, interrelationships of primary canine and second molars, overbite and overjet were evaluated. Results: Primate space was observed on both sides of the arch in 82.2% of the subjects. The most prevalent type of primary molar relationship was flush terminal plane (52.1%) followed by distal step (31.3%) and then mesial step (16.7%). The primary canine relationship was ranked in the descending order of prevalence as Class I (77.1%), Class II (13.5%), end-to-end (5.2%) and Class III (4.2%). Normal overbite and normal overjet was observed in 50% and 81.3% of cases, respectively. Conclusion: This study provides an insight into the dental arch dimensions, occlusion, spacing and crowding in primary dentition in Iranian children. In most of the cases, primate space and flush terminal plane were observed.

Association of infantile bruxism and the terminal relationships of the primary second molars

The aim of this study was to analyze the association between infantile bruxism and the terminal relationships of the primary second molars. A total of 937 pre-school children (both genders), aged from 2 to 6 years, from municipal schools in São Paulo were evaluated. In this study, a questionnaire considering the bruxism habit and the presence of headaches and/or restless sleep was answered by the parents/guardians. A clinical exam of occlusion in the anteroposterior direction (vertical plane - VP, mesial step - MS and distal step - DS) was performed by the examiners in the school environment. Student's t test, Fisher's test and a logistic regression test were applied for the statistical analysis at a significance level of 5%. The prevalence of the bruxism habit was 29.3% among the total sample. Because there was no significant difference between the sides evaluated, the left side was taken as the standard. Among those children with bruxism, 25.7% presented a mesial step terminal relationship at the primary second molars, 29.1% had DS, and 30.2% had VP. Regarding the association of the parafunctional habit with the type of terminal relationship, no significant results were found. Children who slept restlessly or suffered from headaches were verified to show a higher chance of expressing the habit (OR = 2.4 and 1.6, respectively). The prevalence of bruxism in the studied sample was 29.3%, and its association with the primary second molars' terminal relationship was not statistically significant.

An innovative approach for correction of pseudo class III malocclusion with the use of "Planas direct tracks"

Anterior cross bite due to a pseudo Class III is a kind of malocclusion, which has a potential to turn into a facial deformity. This orthodontic emergency should be treated as soon as it is observed. A case of pseudo Class III was treated with Planas direct tracks (PDT). The PDT was designed such that the distal incline of the upper block occludes with mesial incline of the lower block such that the mandible will have a posterior path of closure with condyles in centric relation. Significant clinical change was seen in the subject. There was a significant reduction in mesial step and a considerable improvement in the facial profile. Cephalometrically, there was a significant increase seen in the lower anterior facial height. PDT is an efficient solution for the correction of early pseudo Class III malocclusion.

Relationship between Bruxism and Malocclusion among Preschool Children in Isfahan.

Background and aims Bruxism is defined as a habitual nonfunctional forceful contact between occlusal tooth surfaces. In younger children bruxism may be a consequence of the masticatory neuromuscular system immaturity. The aim of this study was to assess the prevalence of bruxism and investigate the relationship between occlusal factors and bruxism among preschool children. Materials and methods In this cross-sectional survey, 400 3-6-year-old children were selected randomly from different preschools in Isfahan, Iran. The subjects were divided into two groups of bruxers and non-bruxers as determined by the clinical examination and their parents’ reports. The examiner recorded the primary canines (Class I, Class II, and Class III) and molars (mesial step, distal step, flash terminal plane) relationship, existence of anterior and posterior crossbite, open and deep bite. Also, rotated teeth, food impaction, sharp tooth edges, high restorations, extensive tooth caries, and painful teeth (categorized as irritating tooth conditions) were evaluated. The relationship between bruxism and occlusal factors and irritating tooth conditions was evaluated with chi-square test. Results Bruxism was seen in 12.75% of the subjects. Statistically significant relationships existed between bruxism and some occlusal factors, such as flash terminal plane (P = 0.023) and mesial step (P = 0.001) and also, between food impaction, extensive tooth caries, tooth pain, sharp tooth edge and bruxism. Conclusion The results showed significant relationship of bruxism with primary molar relationships and irritating tooth conditions among preschool children.

Characteristics of occlusion in primary dentition of preschool children of Udaipur, India

The present study aimed to study the occlusion characteristics of the primary dentition in a group of 3-5 year-old Indian children and the differences with age in the same group. The study was a cross-sectional survey based on examination of the primary dentition of 200 preschool children aged 3-5 years who were selected from nursery schools in Udaipur, India, using a stratified random sampling technique. The study group was assessed for the several occlusal parameters, which included primary molar and canine relationship, degree of overjet and overbite, anterior and posterior crossbite, and the presence or absence of physiologic spaces and crowding. Flush terminal plane was more common at 3-4 years of age, mesial step at 4-5 years, and class I canine relationship in both age groups. The prevalence of overjet less than 1 mm and overjet exceeding 1 mm was almost comparable in both groups. Overbite with less than 30% overlap was most frequently observed in both age groups, with 30-60% overlap following closely behind. Physiologic and primate spacing were observed in less than half of the children examined, while a small percentage displayed the presence of either single-segment or two-segment crowding. The present study provided insight into the state of dentition, occlusal pattern, spacing, and crowding in the primary dentition of Indian children of Udaipur.

Prevalence of traumatic dental injuries to the anterior teeth among three to thirteen-year-old school children of Tamilnadu

Context:Dental trauma has become an important attribute of dental public health. The primary requisite before actively dealing with such problems is to describe the extent, distribution, and associated variables with the specific condition.Aims:The aim of the present study was to assess the prevalence and distribution of traumatic dental injuries (TDI) to anterior teeth among 3 to 13 years old Chidambaram school children.Settings and Design:A cross-sectional study was conducted. Data was collected through a survey form and clinical examination.Materials and Methods:A total of 3200 school children in the age group of 3-13 years were selected from 10 schools of Chidambaram, Tamilnadu. Information concerning sex, age, cause of trauma, number of injured teeth, type of the teeth, lip competence, terminal plane relationship and the molar relationship were recorded.Statistical Analysis Used:The statistical software EPIINFO (Version 6.0) was used for statistical analysis. In the present study, P≤0.05 was considered as the level of significance.Results:The trauma prevalence in the present study was 10.13%. Children with class I type 2 and mesial step molar relationship exhibited more number of dental injuries. Enamel fracture was the most common injury recorded. Only 3.37% of the children had undergone treatment.Conclusion:The high level of dental trauma and low percentage of children with trauma seeking treatment stresses the need for increased awareness in Chidambaram population.

Characteristics of Primary Dentition Occlusion in Preschool Children: An Epidemiological Study

ABSTRACTObjective: The establishment and maintenance of normal occlusion constitutes one of the important objectives of pediatric dentistry. There are very few studies assessing the occlusal characteristics of primary dentition in the preschool children. The objective of this study was to assess the occlusal characteristics of primary dentition and difference in various parameters, in children between 3 and 5 years of age.Materials and methods: Eight hundred and eight healthy children, of age group between 3 and 5 years, and having full set of deciduous dentition, were selected by random sampling. Examination and recording of occlusal characteristics were done by single examiner.Results: Flush terminal molar relationship was seen in 67.9% of children. Statistically significant (χ2 = 47.835, p = 0.001) increase in mesial step molar relationship was seen with age. The class I canine relationship was the most prevalent canine relation, however the agewise changes of canine relation were not statistically significant. Anterior open bite was observed in 0.2% of children, which was less than the prevalence reported earlier in literature. 91.2% of children had overjet of 1 to 2 mm. The incidence of anterior and posterior crossbite was 0.4%. No cases of infraocclusion and scissors bite were observed.Conclusion: There is change in deciduous molar relationship as age increases. There is a significant increase in mesial step molar relation in 5 years age group compared to 3 years. The low prevalence of posterior crossbite and anterior open bite is suggestive of lower prevalence of sucking habits in children. Larger sample size may be required to assess the prevalence of infraocclusion and scissors bite.How to cite this article: Bhat SS, Rao HTA, Hegde KS, Kumar BSK. Characteristics of Primary Dentition Occlusion in Preschool Children: An Epidemiological Study. Int J Clin Pediatr Dent 2012;5(2):93-97.

Association between infant feeding duration and the terminal relationships of the primary second molars

Aim: This study was developed to assess the effect of prolonged bottle feeding and breastfeeding on the anteroposterior relationship of the dental arches in 3-6-year-old children attending preschools in the eastern zone of Sao Paulo city. Methods: The association between infant feeding duration (artificial and natural) and occlusal characteristics were evaluated in 485 children at the stage of complete primary dentition, who attended municipal preschools in the eastern zone of Sao Paulo city. The information related to types and duration of child breastfeeding was investigated by means of questionnaires filled out by parents/guardians. The occlusal characteristics corresponding to the terminal relationships of the primary second molars were classified as vertical plane (VP), mesial step (MS) and distal step (DS). Logistic regression analysis (p < 0.05) was applied. Results: Considering the right and left sides, DS was diagnosed in 9.7% of the cases, MS in 14.2% and VP in 76.1%, without significant differences between sides and genders. The association between the presence of DS and the age of bottle-feeding and breastfeeding cessation was significantly high (p < 0.001). The older the child when bottle-feeding ceased (3- 4 years old) and the shorter the breastfeeding duration (<3 months), the greater the chances of the child presenting DS. Conclusions: Breastfeeding duration is one of the factors that could influence the development of DS because the longer the breastfeeding duration, the higher the percentage of children who were not bottle fed, ranging from 5.8% (among children who interrupted breastfeeding before the age of 3 months) to 63.8% (after 12 months of age).

전북지역 다문화가족 어린이의 구강건강 실태조사

본 연구는 전라북도 지역에 거주하는 다문화가족 어린이의 치아 우식 발생 양상과 빈도, 그리고 유구치 교합관계를 조사하였다. 이를 위해 익산시 인큰 지역의 다문화가족 지원센터와 협의하여 만 3-5세 유치열기 어린이 190명을 대상으로 각 치아 및 치면별 우식 발생 양상과 교합관계를 조사한 결과 다음과 같은 결론을 얻었다. 1. 전체 어린이의 유치우식경험자율(dmf rate) 는 3세에서 61.7%, 4세에서 88.7%, 5세에서 92.6%로 나타났으며 남녀간 유의 한 차이 가 없었다(p>0.05). 2. 우식경험유치지수는 3세에서 22.2, 4세에서 4.97, 5세에서 6.62로 남녀간 유의한 차이가 없었다(p>0.05). 3. 전체 연령을 대상으로 보았을 때 우식경험유치율은 3세에서 28.8%, 5세에서 56.7%를 나타낸 상악 유중절치가 높은 빈도를 보여주고 있다. 4. 필리핀, 캄보디아, 베트남 등의 동남아시아 여성의 어린이 우식경험유치지수와 우식경험유치면지수가 중국이나 일본 여성의 어린이보다 높은 수치를 나타냈다. 5. 유구치 교합관계에 있어 flush terminal plane type인 경우가 82.6%, distal step type이 5.4% 그리고 mesial step type이 8.4%로 나타났다. The purpose of this study was to obtain the data for dental caries experience and occlusal pattern to utilize these data for motivating oral health promotion and activating oral health care programme in preschool children of multicultural family. Caries prevalence on primary teeth was surveyed for 3-5 years old 190 children of multicultural families in Chonbuk province. The results were as follows : 1. Dental caries prevalence rate of primary teeth (dmf rate) was 61.7% at 3 years of age, 88.7% at 4 years of age, and 92.6% at 5 years of age (p>0.05). 2. Average score of dmft index was 2.22 at 3 years of age, 4.97 at 4 years of age, and 6.62 at 5 years of age (p>0.05). 3. Most of the caries-prevailed tooth was maxillary primary central incisor and showed 28.8% at 3 years of age, 56.7% at 5 years of age. 4. dmft index and dmfs index of children of Vietnamese, Cambodian, and Filipinos women were higher than those of Chinese and Japanese. 5. In sagittal primary molar relationship, flush terminal plane type was 82.6%, distal step type was 5.2% and mesial step type was 8.4%. This study is the first report for children of multicultural families in Korea. More attention for children of multicultural families will be needed in aspect of oral disease prevention and treatment.

Correction of skeletal Class III in a growing male patient by reverse pull facemask

The following case report describes the management of a 6-year-old male patient in early mixed dentition with a mesial step molar relation, an anterior reverse overjet, and skeletal Class III due to a slightly deficient maxilla. The treatment plan included protraction of the maxilla by a reverse pull Petit type facemask for 10 months followed by 15 months of active retention by a Frankel III appliance.

Longitudinal changes in the molar relationship from primary to permanent dentition

Preschool children (n=721) aged between 4 and 5 years were examined and 60 were selected. Two pairs of dental casts were obtained for each child. The first pair was from primary dentition before eruption of permanent first molars; the second pair had the permanent first molars in occlusion. The sample was divided into 3 groups, according to the terminal plane. The findings indicate that 55% of the group with flush terminal plane developed into Class I, 40% into Class II, and 5% into Class III molar relationship in the permanent dentition. The group with mesial step, 70% progressed to Class I, 25% to Class II, and 5% to Class III molar relationship in the permanent dentition. Finally, the group with distal step developed into Class II in the permanent dentition. It can be concluded that the terminal relationship of deciduous second molars was associated with the permanent first molars occlusion.

Revised criteria for the assessment and interpretation of occlusal deviations in the deciduous dentition: a public health perspective

Secondary data from a randomized sample of Brazilian preschool children were analyzed to evaluate the prevalence of occlusal deviations in the deciduous dentition that can adversely affect the permanent dentition, using revised criteria. Overjet and overbite used cut-off points described in the literature to exclude mild malocclusion cases. Overjet>3 mm and overbite>3 mm were present in 16% and 7% of the children, respectively. On the sagittal plane, only bilateral deviations were considered: molar relationship in distal step (9.7%) and mesial step (6%) and canine relationship class 2 (11%) and class 3 (2.9%). Regarding other occlusal deviations, severity criteria were not reported in the literature. Crude prevalence rates of openbite (27.9%), posterior crossbite (11.3%), and crowding in the maxillary arch (7%) and mandibular arch (11.3%) were recorded. The assessment of malocclusion in the deciduous dentition should focus on the severity of occlusal deviations for the identification of cases and non-cases that are relevant to public health. Need for further consensus and improvement in the interpretation of epidemiological data on malocclusion related to this developmental stage is emphasized.

Occlusal Changes from Primary to Mixed Dentitions in Nigerian Children

To evaluate longitudinally the occlusal changes between the deciduous and early mixed dentition stages in Nigerian children. The occlusion of 145 3- to 5-year-old children was initially assessed at a popular pre-primary school center in Ibadan, Nigeria in October 2002, using the Foster and Hamilton criteria. The same group of children was followed up for reexamination in October 2006 in the primary school section of the center. Of 61 students who were located and reexamined, 54 (26 male and 28 female) qualified for the study. The molar relationship was assessed using Angle classification, and other occlusal features such as spacing, crowding, overbite, and overjet were also assessed. Descriptive statistics, chi-square test, as well as Pearson correlation coefficient, were applied as appropriate in the analysis of the data. Of 32 subjects initially having a flush terminal relationship (Class 1), 22 (68.7%) resulted in a Class I molar relationship, seven (21.9%) had Class II, and three (9.4%) had asymmetric relationships. Mesial step (Class III) was formed initially in 18 and 11 (61.1%) resulted in Class I. A Class III developed in five (27.8%). Significant positive correlations were found for molar relationship, crowding, overbite, and overjet variables (P < .01) between the two periods of assessments, but all were below 0.7 value. Angle Class I molar relationship was favored by initial flush terminal plane and mesial step relationships in the deciduous dentition.

Morphological Study on Quadruplets by Cephalometric and Model Analyses

Clarifying the genetic factors involved in maxillofacial growth and development is very important in orthodontic treatment planning and prognosis. However, few dental studies have examined multiple births. The present orthodontic evaluation was conducted using orthodontic data from a set of quadruplets. Orthodontic evaluation was performed on a set of quadruplets (1 girl and 3 boys) aged 9 years and 7 months at the initial visit. Although all 4 children weighed only about 1,400 g each at birth, height and body weight subsequently normalized. Mean skeletal age of the quadruplets was 10 years and 2 months, about 6 months ahead of their calendar age. In all 4 children, facial profile was mostly symmetrical and convex. Intraoral findings showed a Hellman's dental age of IIIA, together with spacing of the upper anterior teeth. Both overbite and overjet were 5-7 mm, and mesial step of the terminal plane was noted. Model analysis showed that tooth materials were on the large side, while arch width was narrow. Cephalometric analysis revealed that the ANB of the first- and fourth-born children was 6 degrees , and skeletal maxillary protrusion due to mandibular retrusion was diagnosed. The second- and thirdborn children exhibited no marked skeletal abnormalities.

Estudo do relacionamento ântero-posterior entre os arcos dentários decíduos, de crianças nipo-brasileiras, dos dois aos seis anos de idade

OBJETIVO: verificar as prevalências dos diferentes tipos de relacionamentos ântero-posteriores entre os arcos dentários decíduos, bem como o possível dimorfismo sexual, em crianças nipo-brasileiras na faixa etária dos dois aos seis anos de idade. METODOLOGIA: foram avaliadas por inspeção visual 310 crianças nipo-brasileiras, matriculadas em 19 escolas do estado de São Paulo, sendo 154 do gênero masculino e 156 do feminino. Os resultados foram submetidos ao teste do qui-quadrado e revelaram ausência de dimorfismo sexual para a maioria dos relacionamentos analisados, permitindo apresentar os resultados conjuntamente para ambos os gêneros. RESULTADOS: as prevalências dos relacionamentos entre os segundos molares decíduos foram: 47,4% para o degrau mesial, 41,3% para o plano terminal reto, 5,5% para o degrau distal e 5,8% para os casos com assimetrias. Para os relacionamentos entre os caninos decíduos, conforme Foster e Hamilton, constataram-se prevalências de 77,4% para a Classe 1, 6,8% para a Classe 2, 6,8% para a Classe 3 e 9% para as relações assimétricas. Apenas a Classe 2 apresentou dimorfismo sexual, sendo de 3,9% para o feminino e de 9,7% para o masculino. Quanto à sobressaliência verificaram-se prevalências de 71,3% para a normal, 14,2% para a aumentada, 7,4% para a mordida cruzada anterior e 7,1% para a mordida topo-a-topo. RESULTADOS: concluiu-se que a maioria das crianças nipo-brasileiras avaliadas neste estudo, apresentaram um relacionamento ântero-posterior normal entre os arcos decíduos, merecendo atenção uma ligeira tendência para o desenvolvimento da Classe 3.

Occlusal development in children of African American descent. Types of terminal plane relationships in the primary dentition.

To compare the types and depths of the terminal plane relationships (mesial step, distal step, and flush) in the primary dentitions of African American (AA) and European (E) children. A convenience sample of 189 African American children (103 males and 86 females) was compared to a historical sample of 61 European children (39 males and 22 females, age range 2.1 to 5.2 years, mean age of 4.1 years). Plaster dental casts were analyzed for both samples. Terminal plane depth (TPD) was defined as the anteroposterior distance (APD) between the distal surfaces of the maxillary and mandibular second primary molars of dental casts registered in centric occlusion. Sample differences were evaluated using a 2-sample independent group t-test. Eighty-nine percent of African American children and 63% of European children exhibited a mesial step terminal plane. The average APD of the mesial step in African American children was 1.29 mm compared to 1.13 mm in European children, but this was not statistically significant (P = .18). The samples differed significantly (P = .001) in the average APD distal step relationship (AA, 1.08 mm vs E, 2.26 mm). The prevalence of distal step relationships was lower in African American children (5%) compared to European children (16%). African American children had a lower prevalence of flush terminal plane (6%) compared to European children (21%). In African American children as in European children, a mesial step, rather than a flush terminal plane, is the norm for the completed primary dentition.

Occurrence of malocclusion and need of orthodontic treatment in early mixed dentition

This study analyzed the occlusions of 489 children at the onset of the mixed dentition period (mean age 5.1 years, range 4.0-7.8 years). These children participate in an ongoing clinical trial that is investigating the effects of orthodontic intervention in the early mixed dentition. The aim was to report the occlusal findings at the baseline. The frequencies of mesial step, flush terminal plane, and distal step were 19.1%, 47.8%, and 33.1%, respectively. The canine relationship was Class I in 46.1%, Class II in 52.4%, and Class III in 1.5% of the sides examined. An asymmetrical canine relationship was found in 30.1% of the children, significantly more often on the right side than on the left ( P < .001). Overjet ranged from −2 to +10 mm with a mean of 2.9 mm. Overbite ranged from −5 to +8 mm with a mean of 2.8 mm. Excessive (≥4 mm) overjet was found in 26.7% and overbite in 33.8% of the children; in 15.5% of the children, both variables were 4 mm or more. Anterior crowding was detected in the maxillary arch in 11.6% and in the mandibular arch in 38.9% of the children. Girls showed mandibular crowding more often than boys ( P < .01). A posterior crossbite was found in 7.5% of the children, unilaterally in 6.4% and bilaterally in 1.1%. Scissors-bite was detected in 1.1% and an anterior crossbite in 2.2% of the children. The mean maximal opening was 40.3 mm. Joint sounds were registered in 5.2% of the children. The prevalence of malocclusion was between 67.7% and 92.7%, depending on the values of unacceptable parameters used for each occlusal characteristic.

Occlusion and tooth/arch dimensions in the primary dentition of preschool Jordanian children

To assess tooth and arch dimensions, occlusal relationships and the presence of spacing or crowding in primary dentition of Jordanian children. A list of 10 kindergartens was randomly selected in the governate of Irbid, Jordan. A total of 1048 children (2.5-6 years old) with complete primary dentitions were examined for occlusal relationships in three planes, and the presence of spacing or crowding. Of those, study casts were taken for 87 randomly selected 4-5-year-old children (39 girls, 48 boys). Measurements of tooth and arch dimensions were made using electronic digital sliding callipers. In general, males had larger mesiodistal tooth width and larger arch dimensions. Bilateral mesial step molar relationship was found in 47.7% of children followed by bilateral flush terminal molar relationship in 37% and bilateral distal step in 3.7%. Asymmetric right/left molar relationship was found in 11.6% of children examined. Class I canine relationship was found in 57% of children, followed by Class II canines in 29% and Class III canines in 3.7%. Fifty per cent of children examined had Class I incisors, 24.7% had Class II Division 1, 13.5% had Class II Division 2 and 11.8% showed reversed overjet. Ideal overbite was seen in 44.3% of children, reduced overbite in 21.8%, increased overbite in 28.2% and 5.7% had anterior openbite. Buccal crossbite was seen in 7% of the sample. Generalized spacing was found in 61.8% and 61.1% of children in the upper and lower arches, respectively. Anthropoid spaces were found in 70% of the upper arches and in 51% of the lower arches. Males had larger tooth/arch dimension than that of females in the primary dentition stage. Mesial step molar relationship was found in 47.7% of the subjects followed by flush terminal molar relationship in 37%. The majority of children examined had spaced primary dentition.

Changes in the molar relationship between the deciduous and permanent dentitions: A longitudinal study

The purpose of this study was to describe the changes in the molar relationship from the deciduous dentition to the permanent dentition in 121 subjects from the Iowa Longitudinal Growth Study. In addition, an attempt was made to determine the association between the various dentofacial variables and the changes in the molar relationship in 55 persons (33 male and 22 female subjects) with normal occlusion. All subjects were evaluated at three stages of dental development: stage I, completion of the deciduous_ dentition ( X age = 4.94 years); stage II, when permanent first molars initially erupt into occlusion ( X age = 6.91 years_); and stage III, at the completion of eruption of the permanent dentition excludng third molars ( X age = 13.01 years). The following sets of variables were evaluated: molar relationship, mesiodistal crown diameters of single and groups of deciduous and permanent teeth, dental arch widths, arch lengths, and various cephalometric dentofacial variables. Correlation coefficients and regression analyses were used to assess the relationships between these measurements and the changes in the molar relationship from the deciduous to the permanent dentition. The findings indicate that of the 242 sides evaluated in the deciduous dentition, 61.6% developed into a Class I molar relationship, 34.3% into Class II, and 4.1% into Class Ill. Those sides that started with a distal step in the deciduous dentition proceeded to develop into a Class II molar relationship in the permanent dentition. Of the sides with a flush terminal plane relationship in the deciduous dentition, 56% progressed to a Class I molar relationship and 44% to Class II in the permanent dentition. The presence of a mesial step in the deciduous dentition indicates a greater probability for a Class I molar relationship and a lesser probability for a Class II molar relationship. In the 55 subjects who achieved normal occlusion, the magnitude of change in the molar relationship was 1.91 mm in male subjects and 1.64 mm in female subjects. On the average, these cases had a mesial step in the deciduous dentition of 0.8 mm in male subjects and 1.0 mm in female subjects. There was a favorable difference between the maxillary and mandibular leeway spaces of 1.3 mm in male subjects and 1.1 mm in female subjects. There was also a favorable decrease in the Wits appraisal of 1.2 mm in male subjects and 0.6 mm in female subjects. There was only a weak correlation between the change in the molar relationship and the change in the Wits appraisal, and no correlation with the magnitude of the difference in the leeway space between the maxillary and mandibular arches. The results of the regression analysis indicated that a number of changes in various dentofacial variables-for example, intercanine widths, arch lengths, maxillary and mandibular relationships-are associated with changes in the molar relationship. The clinical implications of the present findings are discussed.

沖縄幼児における乳歯列弓の形態学的研究

Many investigators indicated that there are differences of race and area on human traits. For the present paper, comparative and morphological investigation of the deciduous dentition were made on the plastercasts from 143 Okinawa children (82 boys and 61 girls) ranging in age from 3-5 years Kitakyushu children in same age group. The results were as follows : 1. Percentage of normal occlusion of deciduous dentition in Okinawa children was showed 65% or more in both boys and girls, and it tended higher with an increase in age. In malocclusion, percentage of overbite totaly boys and girls was highest (11.9%), and percentage of edge to edge bite was higher but cross bite was lower in the girls than in the boys. 2. About type of interdental spaces, percentage of mixed type of primate space and developmental space was distinctly higher in the upper dental arch in both boys and girls. But, percentage of closed type as same level as mixed type of primate space and developmental space was higher in the lower dental arch, especially in the girls. 3. About type of terminal plane, percentage of bilateral vertical (straight) type was highest, 56.1% in the boys and 60.6% in the girls, then it was higher in order bilateral mesial step type, bilateral distal step type, vertical-mesial step type. No cases of vertical-distal step type and mesial-distal step type was observed. 4. Upper and lower dental arch lengths were not significantly different between boys and girls in OKinawa. It was recognized that lower anterior dental arch lengths were shorter, but upper anterior, upper posterior and lower posterior dental arch lengths were longer in the Okinawa than in the Kitakyushu children in both boys and girls. 5. Upper and lower dental arch breadths were significantly wider in the boys than in the girls. It was recognized that all the items, except lower posterior dental arch breadth in the girls, of Okinawa children showed wider levels than Kitakyushu children, especially upper and lower anterior dental arch breadths in the boys and upper anterior dental arch breadth in the girls. 6. All the dental arch indices were not significant difference between boys and girls in Okinawa. It was recognized that upper and lower anterior-posterior dental arch breadth indices were significantly higher in the Okinawa than in the Kitakyushu children in both boys and girls, but in the boys, lower anterior-posterior dental arch length index and lower anterior arch index were significantly lower in the Okinawa than in the Kitakyushu children.