Abstract
Introduction
Down syndrome (DS) can cause irregular dental eruption patterns and hypodontia. However, data on permanent tooth eruption in DS patients in Japan are insufficient. This study aimed to predict the dental characteristics of DS by conducting a nationwide survey in Japan.
Methods
Questionnaires were used to collect information about the age, sex, number of present teeth, and dental formula with DS from facilities providing dental care for the disabled. The findings were compared with the Survey of Dental Diseases and used as control survey.
Results
Data were collected from 3348 patients aged 5–69 years. The mean number of permanent teeth was highest ( N = 25.2) at 19, 20–24, and 25–29 years. At 5–19 years, the increase in the eruption rates was slower with DS compared to that in the control survey. At 25–29 years, the difference in eruption rates between the two surveys exceeded 20 % in the mandibular lateral incisors and maxillary second molars, except for third molars. Most of the second premolars were unerupted when the primary second molars were retained. Noneruption of the permanent canines and some adjacent teeth was observed when the maxillary primary canines were retained.
Conclusion
This study demonstrates the eruption status of permanent teeth with DS. The eruption of permanent teeth is delayed, the number of permanent teeth is low, and early tooth loss may be seen with DS. Thus, it is important to determine the overall eruption status and provide adequate support based on their age.
1
Introduction
Down syndrome (DS) is characterized by the existence of additional genetic material from chromosome 21. Although the average life expectancy of those with DS was low several decades ago, a significant increase has been observed worldwide, including in Japan, in recent years [ ]. DS is associated with a variety of systemic diseases, and patients may exhibit irregular dental eruption patterns, hypodontia, macroglossia, high-arched palate, prognathism, fissured tongues, and early tooth loss due to periodontal disease [ , ]. Several reports on the dentition of DS patients have been published worldwide. Nevertheless, a comprehensive nationwide investigation regarding the dental characteristics of individuals with Down syndrome (DS) has not been undertaken in Japan; moreover, data on the number of teeth present in these patients based on age is lacking.
In our previous study, we reported the status of primary teeth eruption and showed that some teeth had delayed eruption and some were missing or retained [ ]. This study aimed to predict the dental characteristics of patients with DS by conducting a nationwide questionnaire survey in Japan. As in the previous study, only the permanent teeth were compiled and analyzed in this study.
2
Methods
2.1
Questionnaire
Questionnaires were distributed to all 29 dental schools in Japan. Furthermore, the survey encompassed facilities that included physicians certified by the Japanese Society for Disability and Oral Health, along with those delivering dental care to patients with disabilities. These facilities were identified based on the information available on the association’s website in 2018 ( https://www.kokuhoken.or.jp/jsdh-hp/html/ ), resulting in a total of 565 entities surveyed. The questionnaire solicited information such as age, gender, the number of present teeth, and the dental formula of patients with DS. While the survey captured the count of present teeth at the time of the investigation, it did not delve into the reasons for tooth loss. A comparative analysis was conducted by juxtaposing the questionnaire findings with data from the 2016 Survey of Dental Diseases in Japan [ ]. The latter specifically focused on individuals aged one year and above, chosen through a stratified random sampling method that covered all regions of Japan, and served as the control dataset for the current study.
2.2
Study design
As shown in Fig. 1 , three parameters were investigated based on the age in the control survey. First, the mean number of permanent teeth per patient among the 5–69-year-olds was investigated and compared with that in the control data. In addition, the period of maximum mean number of permanent teeth in this range was determined, and two additional analyses were conducted. For two additional analyses, determining the individual permanent tooth eruption rate and the compensation for unerupted permanent teeth by the persistence of primary teeth was investigated. In particular, the maxillary primary canines and maxillary and mandibular primary second molars, which had the highest number of persistent primary teeth in the previous survey, were examined. Second, the rate of increase in the eruption of a permanent tooth from 5 to 19 years of age was investigated. Generally, permanent teeth erupt around 6 years of age [ , ]. Third, the decrease in the rate of permanent tooth eruption at over 20 years of age was investigated. Despite numerous reports on the eruption process of permanent teeth in DS, no study has described the tooth loss process. Therefore, the process involved in the decrease in the eruption rate of the permanent tooth during adulthood was investigated in this study. In addition, the wording of the text, for permanent teeth, central incisors shall be represented as #1, lateral incisors as #2, canines as #3, first premolars as #4, second premolars as #5, first molars as #6, second molars as #7 and third molars as #8. For primary teeth, primary central incisors shall be represented as #A, primary lateral incisors as #B, primary canines as #C, primary first molars as #D, and primary second molars as #E.
2.3
Statistical analysis
Statistical comparisons of the mean number of permanent teeth were conducted using the Mann–Whitney U test, while the individual permanent tooth eruption rate was assessed through Fisher’s exact test. Due to the unavailability of data on the number of individual teeth in the Survey of Dental Diseases, statistical analysis was employed as a control survey when necessary. The analyses were conducted utilizing SPSS version 27.0 (IBM, Tokyo, Japan), with the significance threshold established at P < 0.05.
2.4
Ethical approval
This study underwent review and approval from the Ethical Review Committee of the Japanese Society for Disability and Oral Health (no. 22014). To safeguard personal information, the data were anonymized.
3
Results
The survey exhibited a response rate of 45.1 % (268 out of 594 facilities). Table 1 delineates the status of permanent tooth eruption within each age group among individuals with DS. Valid responses were obtained from 3656 patients aged 0–69 years, of which those aged 0–4 years were excluded because they did not possess permanent teeth. Finally, data were collected from 3348 patients (1997 males [59.6 %] and 1351 females [40.4 %]) aged 5–69 years ( Table 1 ). The mean number of permanent teeth in this age group was 19.7, with no significant differences between males and females.
| Age group | Number of subjects | Total number of present permanent teeth | Mean number of present Permanent teeth | Number of persons | Total number of present Permanent teeth | Mean number of present Permanent teeth | |||
|---|---|---|---|---|---|---|---|---|---|
| Male | Female | Male | Female | Male | Female | ||||
| 5–69 | 3348 | 65,864 | 19.7 | 1997 | 1351 | 39,278 | 26,586 | 19.7 | 19.7 |
| 5–9 | 487 | 2260 | 4.6 | 313 | 174 | 1376 | 884 | 4.4 | 5.1 |
| 10–14 | 409 | 7361 | 18.0 | 238 | 171 | 4186 | 3175 | 17.6 | 18.6 |
| 15–19 | 354 | 8683 | 24.5 | 230 | 124 | 5742 | 2941 | 25.0 | 23.7 |
| 20–24 | 330 | 8314 | 25.2 | 194 | 136 | 4967 | 3347 | 25.6 | 24.6 |
| 25–29 | 326 | 8200 | 25.2 | 202 | 124 | 5150 | 3050 | 25.5 | 24.6 |
| 30–34 | 318 | 7898 | 24.8 | 184 | 134 | 4593 | 3305 | 25.0 | 24.7 |
| 35–39 | 326 | 7589 | 23.3 | 183 | 143 | 4282 | 3307 | 23.4 | 23.1 |
| 40–44 | 293 | 6661 | 22.7 | 165 | 128 | 3779 | 2882 | 22.9 | 22.5 |
| 45–49 | 261 | 5020 | 19.2 | 160 | 101 | 3039 | 1981 | 19.0 | 19.6 |
| 50–54 | 156 | 2709 | 17.4 | 84 | 72 | 1553 | 1156 | 18.5 | 16.1 |
| 55–59 | 53 | 752 | 14.2 | 26 | 27 | 358 | 394 | 13.8 | 14.6 |
| 60–64 | 23 | 263 | 11.4 | 13 | 10 | 165 | 98 | 12.7 | 9.8 |
| 65–69 | 12 | 154 | 12.8 | 5 | 7 | 88 | 66 | 17.6 | 9.4 |
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