Abstract
Introduction
Down syndrome (DS) is often associated with delayed teeth eruption, gross motor skill acquisition, and feeding difficulties. In typically developing (TD) children, changes in weaning food texture with deciduous teeth eruption and motor skill acquisition, which improves feeding skills. However, in DS, these processes are delayed, and age alone is not a reliable predictor for such changes. Therefore, we investigated the association between these parameters in children with DS.
Methods
We administered questionnaires to parents of 56 children with DS aged 0–3 years. The survey items included timing of deciduous tooth eruption, physical development, acquired gross motor skills, and texture of weaning foods being consumed. The included children were allocated to two groups according to the confirmed eruption of mandibular deciduous central incisor by or after 12 months.
Results
The groups significantly differed in height, Kaup index, and acquisition age of pulling to stand, as determined by Mann–Whitney U test. Furthermore, multiple regression analysis revealed a significant association between the age of mandibular central incisor eruption and height along with that of acquisition age of pulling to stand. However, no significant difference was observed in the texture of weaning foods.
Conclusion
The observed associations between the eruption of mandibular central incisor, height, and acquisition age of pulling to stand suggest an association between teeth eruption, physical development, and motor development. Despite no differences in weaning food texture, most patients developed dysphagia habilitation, indicating the need to adjust food texture based on delays in physical and motor development.
1
Introduction
Down syndrome (DS) is a chromosomal disorder caused by trisomy 21. Its specific features are intellectual disability, hypotonia, and specific facial features [ , ]. In Japan, about 2200 new DS births are recorded annually, and the overall population is estimated to be 80,000; therefore, DS is considered to be one of the most common congenital diseases [ , ].
Oral findings in DS indicate delayed eruption in deciduous and permanent dentitions. Previous studies have reported a considerable delay in the eruption of some types of deciduous teeth in children with DS compared with typically developing (TD) children [ ]. Since these studies, the data from large-scale research on the eruption of deciduous teeth in DS has been limited [ ]. Furthermore, compared with TD children, those with DS have significantly more delayed acquisition of gross motor skills owing to hypotonia and heart disease [ ].
The texture of weaning foods sequentially changes with the eruption of deciduous teeth and acquisition of gross motor skills as these factors promote an increase in chewing power [ ]. However, it is inappropriate to follow the guidelines and wean children with DS who experience delayed eruption of deciduous teeth and acquisition of gross motor skills strictly according to their monthly age. If a weaning food texture is decided solely based on a child’s age without considering the possibility of these delays, there may be a higher risk of oral disorders, such as tongue protrusion or difficulties in masticating solid foods and swallowing, which are commonly observed in children with DS [ , ].
Tooth eruption is a significant milestone for both children and parents, and the mandibular deciduous central incisor often is the first to appear, making it an easily visually identifiable development. Previous studies have reported an association between the eruption of deciduous teeth and physical growth [ ]. Finding an association among the eruption of deciduous teeth, acquisition of gross motor skills, and a texture of weaning foods can be beneficial for the care of children with DS. Therefore, we determined whether the timing of mandibular deciduous central incisor eruption is associated with the acquisition of gross motor skills and the textures of ingested weaning foods.
2
Material and methods
2.1
Study design
This cross-sectional study was conducted using questionnaires regarding deciduous tooth eruption and acquisition of gross motor skills. The questionnaires were administered to parents of children with DS starting from November 2022. The study was conducted at various institutions, including the Department of Hygiene and Oral Health at Showa University School of Dentistry, the Department of Special Needs Dentistry at Nihon University School of Dentistry at Matsudo, and the Department of Pediatrics at Tokyo Teishin Hospital. To investigate the timing of deciduous tooth eruption, children with DS aged 0–3 years were enrolled. At each facility, when applicable, we explained the study to the parents of children with DS during their visits for dental appointment, dysphagia habilitation, occupational therapy, etc. Those who consented to participate were requested to sign a consent form. For deciduous teeth that had already erupted, we asked the parents to enter information only if they knew the exact eruption time, for example, if they had recorded it in their mother–child handbooks. Children in whom oral assessment was difficult, who had a complicated medical history, or with uncertain deciduous teeth eruption were excluded from the study. The filled-out questionnaires were collected in May 2024 either during patient visits to each facility or via mail ( Fig. 1 ).
2.2
Questionnaire
We defined the timing of deciduous tooth eruption as when part of the tooth was becoming visible. We also included photos in the questionnaire to ensure accurate recording by parents. At the time of eruption of each deciduous tooth, the main items evaluated in the questionnaire were the acquisition of gross motor skills and texture of weaning foods provided. The items under gross motor skills covered fixed neck, turning over, sitting, crawling, pulling to stand, and walking. As regards the texture of weaning foods, we asked to check all stages for main and side dishes: initial, middle, later, and final. Fig. 2 presents the description of the textures of weaning food [ ]. This detailed division of weaning foods according to different textures is unique to Japan. It serves as a guideline for changing the textures of the ingredients, starting from the initial stage, followed by the middle, latter, and final. According to the Breastfeeding and Weaning Support Guide published by the Ministry of Health, Labour and Welfare in 2019 [ ], the initial stage is from around 5 or 6 months old; middle stage, from around 7 or 8 months old; latter, from around 9 to 11 months old; and final, from around 12 to 18 months old.
Subendpoints were represented by date of birth, birth weight and height, gender, number of weeks of gestation, presence of heart disease, visual impairment, and hearing impairment. Furthermore, we included a question about whether the patients had ever undergone dysphagia habilitation.
2.3
Statistical analysis
The data from the returned questionnaires from each facility were compiled into a single database and analyzed. First, the eruption age of mandibular deciduous central incisors was compared with that of TD children reported by the Japanese Society of Pediatric Dentistry in 2019 [ ]. In addition, the acquisition age of pulling to stand was compared with that in the Infant Physical Growth Survey conducted by the Ministry of Health, Labour and Welfare every 10 years [ ].
The data from the returned questionnaires were first stratified by gender and comparatively analyzed. Gestational age, birth height and weight, eruption age of the mandibular deciduous central incisor, and acquisition age of pulling to stand were evaluated using the Mann–Whitney U test, whereas the presence of heart disease as well as visual and hearing impairments was analyzed using Fisher’s exact test.
The included patients were allocated to two groups based on whether their mandibular deciduous central incisors had erupted by 12 months of age or later. The age of 12 months is a significant milestone, and in the Japanese Breastfeeding and Weaning Support Guide, it is described as the time for transitioning to solid foods. Considering that the median eruption age of mandibular deciduous central incisors in this study is 12 months, this age was set accordingly for all patients. The eruption timing of LA in children with DS has been reported to vary, with averages of 13 months [ ] or 14–15 months [ ]. Eruption of LA before 12 months can be considered early for children with DS. Therefore, in this study, we divided the subjects into two groups: those with early eruption of LA before 12 months of age and those with eruption after 12 months, which is typical for children with DS, and performed analyses. Additionally, although not widely implemented, some municipalities offer voluntary health checkups for 12-month-old children. These checkups include the assessment of LA eruption, assessment of weaning practices including feeding difficulties, and confirmation of acquisition of gross motor skills. There is also a designated section in the mother–child handbooks for recording these observations, emphasizing the importance of 12 months milestone from the perspective of health guidance.
In the two groups, the median values for gestational age, birth height and weight, eruption age of the mandibular deciduous central incisor, height and weight at the time of eruption of the mandibular deciduous central incisor, Kaup index, and acquisition age of pulling to stand were also analyzed using the Mann–Whitney U test. The gender distribution, presence of heart disease, and visual and hearing impairments were assessed using Fisher’s exact test. In addition, the texture of weaning foods consumed at the time of the eruption of the mandibular deciduous central incisor, divided into two groups according to stage: Ⅰ: initial, middle, latter, and Ⅱ: final, was analyzed using Fisher’s exact test. The reason for dividing the patients into two groups was that the median eruption age for the mandibular deciduous central incisors in this study was 12 months, which is recommended by the Japanese Breastfeeding and Weaning Support Guide as the time for transitioning to the final stage involving the teeth. However, because mandibular deciduous central incisors alone are insufficient for this transition, it is considered to be more appropriate to preserve the latter stage, where food is chewed using gums. Multiple regression analysis was conducted using the eruption age of mandibular deciduous central incisors as the dependent variable to analyze factors related to eruption age.
Furthermore, the correlation between the acquisition age of pulling to stand and the presence of heart disease was analyzed using Spearman’s rank test.
Data analysis was conducted using SPSS version 27.0 (IBM, Tokyo, Japan). P < 0.05 was considered to indicate statistical significance.
Ethical approval
The study protocol was approved by the Ethics Review Board of Showa University and all the facilities where the questionnaires were distributed (22-107-B). Furthermore, the study was conducted in accordance with the Helsinki Declaration. Data were anonymized to maintain confidentiality.
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Results
The survey response rate was 54.1%, with 60/111 copies returned. Of the 60 copies, 56 had the eruption month of mandibular deciduous central incisors recorded. Table 1 presents the characteristics of the patients, which consisted of 33 boys and 23 girls. It shows the median and range of gestational weeks, the birth weight and height of the patients, and the number and percentage of children with heart disease as well as visual and hearing impairments. In addition, the median eruption age of mandibular deciduous central incisors for boys was 12 months, whereas for girls, it was 11 months. The total median age in the sample was 12 months. The median acquisition age of pulling to stand was 17 months for boys, girls, and total sample. The Mann–Whitney U test and Fisher’s exact test were conducted to compare between boys and girls, and no significant differences were observed in all items. Therefore, we analyzed without stratifying by gender.
The 56 respondents were divided into two groups: those whose mandibular deciduous central incisors erupted by 12 months (BE) and those after 12 months (AE). Table 2 presents the number of boys and girls in each group, the median and range of gestational weeks, birth weight and height, eruption age of the mandibular deciduous central incisor, weight and height at the time of eruption of the mandibular deciduous central incisor, Kaup index, acquisition age of pulling to stand, and percentages of those with heart disease as well as visual and hearing impairments. Furthermore, the proportions of the textures of weaning foods consumed at the time of the eruption of mandibular deciduous central incisors were categorized according to stage: initial, middle, latter, and final. The results of the analysis conducted using the Mann–Whitney U test and Fisher’s exact test were also presented. Significant differences were observed between the groups in terms of the eruption age of the mandibular deciduous central incisor ( P < 0.001), height at the time of eruption of the mandibular deciduous central incisor ( P = 0.033), and Kaup index ( P = 0.001). Furthermore, a significant difference was observed in terms of the acquisition age of pulling to stand ( P = 0.008).
