Fédération Dentaire Internationale (FDI) World Dental Federation defines oral health as “it is multi-faceted and includes the ability to speak, smile, smell, taste, touch, chew, swallow and convey a range of emotions through facial expressions with confidence and without pain, discomfort and disease of the craniofacial complex (head, face, and oral cavity)” (1). This definition indicates that oral health is not merely the absence of disease, but a complete physical, psychological and social well-being of an individual. In clinical settings, dental professionals usually focus on oral disease diagnosis and have developed various objective measurements, such as using the decayed, missing, and filled teeth index to assess caries conditions and the community periodontal index to assess periodontal diseases (2, 3). However, little emphasis has been placed on patients' subjective perceptions of their oral condition. In light of this, dental researchers introduced the concept of Oral Health-Related Quality of Life (OHRQoL) in the early 2000s (4). OHRQoL is defined as “a multidimensional construct that reflects people's comfort when eating, sleeping and engaging in social interaction; their self-esteem; and their satisfaction with respect to their oral health” (5). This concept has been used to evaluate and understand people's feelings towards their oral condition in different circumstances.

In response to various oral diseases and functional needs, researchers have designed several OHRQoL diagnostic scales to meet the evaluation needs under different circumstances, allowing adult patients to express their subjective feelings. However, there are limited tools developed to measure the OHRQoL of children (6). Because preschool children are in the early stages of growth and development, their cognition, social psychology, and linguistic abilities are not sufficient to support them in accurately and fully expressing their emotions and thoughts (7). Therefore, the evaluation of OHRQoL of young children has always been challenging in oral healthcare (8). There are a few OHRQoL diagnostic scales available for use in young children at present, but the vast majority of these scales are completed by their parents (6). Those scales usually express what the parents believe to be their children's thoughts, rather than directly reflecting the true feelings of the children themselves.

In 2012, scholars developed a Scale of Oral Health Outcomes for 5-year-old children (SOHO-5) (8). It is the first structured questionnaire used to measure the OHRQoL of preschool children by both children's (SOHO-5c) and parental reports (SOHO-5p). SOHO-5c contains seven items, which refer to whether the child has any difficulties in eating, drinking, speaking, playing and sleeping because of his/her teeth, and avoids smiling due to pain or appearance. The answers are recorded by a 3-point scale: 0 = “No”, 1 = “A little”, and 2 = “A lot”. The total score of SOHO-5c is the sum of the scores of individual questions. The SOHO-5p also contains seven items, which refer to whether the parents consider their child has any difficulties in eating, speaking, playing and sleeping because of the child's teeth, avoids smiling due to pain or appearance, and whether their child's self-confidence is affected because of his/her teeth. The answers are recorded by a 5-point scale: 0 = “Not at all”, 1 = “A little”, 2 = “Moderate”, 3 = “A lot”, and 4 = “A great deal”. The total score of SOHO-5p is the sum of the scores of these seven questions. For both SOHO-5c and SOHO-5p, a higher score indicates a greater negative impact on the child and therefore a poorer OHRQoL of the child. Dental healthcare professionals can use these questions in an interview format to ask children about their feelings about their teeth; children can express their thoughts using verbal and visual methods. SOHO-5 has been translated and adapted by scholars from various countries and regions, including Bangladesh, Brazil, the Dominican Republic, Indonesia, Iran, Myanmar and Hong Kong (using the Cantonese dialect), for diagnosing the self-perceived OHRQoL of local preschool children (9–14). Studies from different regions indicate that SOHO-5 has good psychometric properties and is a reliable self-rated OHRQoL diagnostic scale for preschool children. However, there is no Mandarin Chinese version of SOHO-5, and it has not been used in preschool populations in mainland China. Therefore, the aim of this study is to translate and culturally adapt SOHO-5 into Mandarin Chinese and to assess the reliability and validity of the Mandarin version of the SOHO-5 (hereinafter referred to as M-SOHO-5) for preschool children in Xiamen, a city in the southeastern part of China.

This study was conducted in Xiamen, Fujian province, China, from November 2023 to December 2024. Ethical approval was obtained from the Institutional Review Board of the Medical Ethics Committee at Xiamen University (No. XDYX202305K29).

We invited 363 5-year-old children and their parents to participate in this study, and 345 children-parent pairs (95%) accepted the invitation. Children who were absent from school on the examination day and who could not cooperate with all the procedures were excluded from this study. Therefore, 259 children and their parents (75%) were included in this study. The prevalence of dental caries was 70% among the participating children, with a mean dmft index of 3.61 (SD = 3.92). About one-third (34%) of the children reported that their dental condition had at least one adverse effect on their oral health-related quality of life. The mean M-SOHO-5c score was 0.78 (SD = 1.77), ranging from 0 to 12. In addition, 28% of parents reported that their children have experienced negative consequences in daily activities because of the children's dental problems. The mean M-SOHO-5p score was 0.79 (SD = 2.10), with a range between 0 and 18 (Table 1). Detailed distribution of the responses for each question of M-SOHO-5c and M-SOHO-5p was presented in Table 2 and Table 3, respectively.

The overall Cronbach's alpha value of M-SOHO-5c was 0.80 (Table 4). Deleting any item in M-SOHO-5c will result in an equivalent or decrease in its Cronbach's alpha value. Corrected item-total correlation for all the items was equal to or higher than 0.40, which was considered a moderately strong relationship (18). The overall Cronbach's alpha value of M-SOHO-5p was 0.85 (Table 5). However, if the item “difficulty in eating because of his/her teeth” was deleted, the Cronbach's alpha value of M-SOHO-5p could be increased to 0.89. The corrected item-total correlation ranged from 0.45 to 0.83, indicating a good relationship between a single item and the whole questionnaire. A total of 52 children (20%) participated in the retest of M-SOHO-5c. The ICCs of M-SOHO-5c were 0.51 [95% confidence interval (CI) was 0.07 to 0.74, p-value = 0.014]. Meanwhile, 49 parents (19%) completed the retest questionnaire of M-SOHO-5p. The results demonstrated that M-SOHO-5p had a medium test-retest reliability (ICCs = 0.65, p = 0.001) (Table 4 and Table 5).

The results of the discriminant validity were presented in Table 6. Although children with dental caries showed a higher mean rank of the total score of M-SOHO-5c than children without dental caries, the result was not significant (130.88 vs. 124.68, p = 0.465). On the other hand, children with dental caries showed a significantly higher mean rank of the total score of M-SOHO-5p than children without dental caries (136.58 vs. 114.72, p = 0.007), which indicated that M-SOHO-5p had a satisfactory discriminant validity. The total scores of both versions of M-SOHO-5 were significantly associated with most of the global rating questions (Table 7 and Table 8). Children with higher M-SOHO-5c scores were less satisfied with their oral health (r = −0.194, p = 0.002). An increase in M-SOHO-5p score was correlated with lower parents-rated oral health of their children (r = −0.421, p < 0.001), less satisfaction with their children's teeth (r = −0.459, p < 0.001), higher parental perceived treatment need for their children (r = 0.362, p < 0.001), and more parental reported negative impact on children's general health (r = 0.532, p < 0.001).

This study successfully translated and validated SOHO-5 in Chinese Mandarin and supported its use in 5-year-old children and their parents in Xiamen, Fujian province, China. It is the first tool in the Mandarin language for preschool children to self-rate their OHRQoL. All the questions in the original SOHO-5 were retained in the Mandarin version, and M-SOHO-5 shows good reliability and acceptable validity. Moreover, all 5-year-old children who participated in the interview were able to understand and answer the questions of M-SOHO-5c smoothly, laying the foundation for promoting the use of this scale by dental healthcare workers in Fujian Province and other regions of China to diagnose OHRQoL in children.

The results of this study showed that the mean scores of M-SOHO-5c and M-SOHO-5p were relatively low (less than 1) despite the high caries prevalence in this group of children. This finding is similar to the Cantonese version (13) but lower than other language versions (9, 11, 12, 14). There may be two major reasons. First, we only recorded caries experience in this study. Other oral health-related conditions, for example, pulp involvement, trauma experience or self-reported toothache, were not included due to the feasibility issue. Although caries prevalence was high in the study group, dental caries cannot completely represent the discomfort that the children felt because of their teeth. Future studies can be performed to understand the correlation between M-SOHO-5 and different oral conditions in more detail. Second, children tend to habituate to chronic pain as time passes (19), so the discomfort may not influence their daily life functions and quality of life (20). The results of this study showed some differences between children and their parents in reporting the OHRQoL of the children. In general, more children reported at least one daily life-related negative impact caused by their teeth than their parents. Children also expressed a higher concern that their teeth condition could influence speaking, playing and sleeping activities. In particular, more than 10% children reported that they avoided smiling due to the appearance of their teeth. However, only 6% parents reported this behaviour. These findings were consistent with the Cantonese version (13). The Cantonese version reported that more children reported negative impacts caused by their teeth than their parents did. They also found that the responses of “avoided smiling due to the appearance of their teeth” were significantly different between the children's version and the parents' version. These results indicated that children themselves might be more sensitive to their personal feelings about oral health. Therefore, oral health researchers should not only rely on parental reports to study OHRQoL in young children, but also need to fully consider the direct feedback from children themselves.

In this study, internal consistency was assessed by two aspects: 1) whether all the items in M-SOHO-5 measured the same concept, and 2) whether the items were closely related to each other as a whole (21). The overall Cronbach's alpha value of M-SOHO-5c was 0.80, which was higher than the results in the original study (Cronbach's alpha=0.74) (7) and similar to other language versions (Brazilian – 0.77, Cantonese – 0.71, Myanmar – 0.82) (9, 13, 14). For a scale containing only seven items, such a Cronbach's alpha value was considered quite high, as lower reliability was common in questionnaires with fewer items (22). If any item was deleted in M-SOHO-5c, the Cronbach's alpha value would remain the same or decrease. In addition, the corrected item-total correlation of all items was considered a moderately strong relationship between items (18). Therefore, all of this evidence indicates that M-SOHO-5c has favourable internal consistency. For M-SOHO-5p, although the Cronbach's alpha value slightly increased after removing the item “difficulty in eating because of his/her teeth”, the increase was very small (from 0.85 to 0.89). This situation was also identified in the Cantonese version and Myanmar version (13, 14). In addition, this item was strongly correlated with the prevalence of dental caries in children and all the global rating questions in M-SOHO-5p. Therefore, we decided to keep this significant question in the questionnaire. Except for this issue, M-SOHO-5p showed high Cronbach's alpha values and high item-total correlations, demonstrating its good internal consistency.

This study used ICCs to evaluate the test-retest reliability of the questionnaire, aiming to measure the correlation and consistency of the answers provided by the same participant at different time points (23). In this study, the ICCs values of both M-SOHO-5c and M-SOHO-5p were considered at a moderate level with statistical significance (24). Our ICCs values were lower than other language versions (Brazilian and Myanmar – higher than 0.9, Persian – 0.8, Indonesian – higher than 0.8) (9, 11, 12), while the Cantonese version reported relatively lower test-retest reliability for the parents' version (13). It is worth noting that a relatively low ICC value does not necessarily mean a low degree of consistency, which may also be due to a small number of participants in the test-retest or a lack of sufficient variability between answers (25). In this study, only 52 children and 49 parents joined in the retest, which may be one reason for the relatively low ICC values.

Dental caries status was used in all other language versions to study the discriminant validity (8–14). Given that dental caries was the most widespread oral problem among preschool children in Xiamen, this study used the presence of dental caries as the basis for evaluating the discriminant validity of the M-SOHO-5 (26). Most of the other versions demonstrated that the total score of SOHO-5 in caries-free children was significantly lower than that in children with caries experience (8–14). The results showed that children with dental caries had higher M-SOHO-5c and M-SOHO-5p scores than children without caries experience. However, the result of M-SOHO-5c was not significant. The main reason might be that the result of “avoid smiling due to pain in his/her teeth” was in contrast to other items. Because the Cronbach's alpha if this item were deleted was lower than the overall Cronbach's alpha value, and the corrected item-total correlation of this item was good, we decided to keep this item in M-SOHO-5c. Nevertheless, the interpretation of the results is important and should be paid more attention to. Moreover, it was worth noting that most of the single items in M-SOHO-5c and M-SOHO-5p did not show a significant correlation to caries status. Therefore, it is recommended to take M-SOHO-5 as a whole to evaluate the general OHRQoL in Mainland Chinese children. In addition, more extensive research on young child populations in other regions of China is needed to further validate the above findings.

This study adopted Spearman's correlation coefficient to evaluate the construct validity of M-SOHO-5 because the results of M-SOHO-5 did not follow normal distributions (27). The results showed a significant correlation between the scores of both M-SOHO-5c and M-SOHO-5p with the answers to most of the global questions, indicating that M-SOHO-5 has good construct validity. Our findings were consistent with other language versions (9–14). However, it was worth noting that the correlation between the total M-SOHO-5c score and children's perception of dental caries was considered statistically non-significant. The main reason for this result may be the insufficient sample size. In this study, the sample size was determined by Cronbach's alpha statistics because it is the primary parameter of a newly developed questionnaire (28). However, the sample size may not be sufficient for Spearman's correlation coefficient analysis. Further studies can consider slightly increasing the sample size to meet the requirements for other statistical analyses.

This study has some limitations. First, we used dental caries status as the only oral health-related condition to measure the discriminant validity for M-SOHO-5. Future studies should consider including pulpal status or the presence of dental trauma experience to evaluate the validity of M-SOHO-5 on different occasions. Second, this study is a small-scale local study. Future studies should be performed in other communities to achieve a larger sample size. Third, the discriminant validity of M-SOHO-5c in dental caries was not statistically significant. The solitary interpretation of M-SOHO-5c data should be taken with caution. Oral health workers should combine the opinions from both children and their parents to achieve a more comprehensive understanding of young children's OHRQoL.

The Mandarin version of SOHO-5 exhibits high internal consistency reliability, moderate test-retest reliability and discriminant validity, and good construct validity. This tool can be used to evaluate the OHRQoL of 5-year-old children in communities where Mandarin is the primary language.