Oral health-related quality of life and caries experience of Hong Kong preschool children

Abstract

Objective: This study aimed to investigate the association between oral health-related quality of life (OHRQoL) and caries experience of Hong Kong preschool children. Methods: Parents or primary caregivers of Hong Kong preschool children were invited to complete a self-administered dental health questionnaire. The study children were examined in their classrooms. The decayed, missing and filled primary teeth (dmft) index was used for documenting the caries status. The questionnaire included the Chinese Early Childhood Oral Health Impact Scale (ECOHIS) and collected sociodemographic information on the parents and children. Logistic regression analysis was used to determine the association between OHRQoL and caries experience of preschool children. Results: A total of 434 preschool children were invited to participate in the study; 336 (77.4%) received a dental examination and returned a parental questionnaire. The mean (SD) age of the study children was 4.7 (0.3) years. An OHRQoL impact (ECOHIS score of >0) for at least one item was reported by 236 (70.2%) parents/caregivers of the children included in the study. The overall mean (SD) ECOHIS score was 5.8 (6.2). A caries prevalence (dmft > 0) of 36.9% and a mean (SD) dmft score of 1.7 (3.2) were calculated for the study children. In the final logistic regression model, children with a higher dmft score had a significantly higher chance of having a poorer OHRQoL (OR = 1.20, 95% CI: 1.07–1.35, P = 0.002), whereas children’s sex, parent’s education levels and the respondent’s relationship to the child were not associated with OHRQoL (P > 0.05). Conclusion: Caries experience is associated with lower OHRQoL of Hong Kong preschool children.

INTRODUCTION

According to the American Academy of Pediatric Dentistry, early childhood caries (ECC) is defined as the presence of one or more decayed (non-cavitated or cavitated lesions), missing (from caries) or filled tooth surfaces in any primary tooth in a child under the age of six¹. Dental caries in primary teeth was reported as the 12th most frequent medical condition in children, affecting approximately 560 million young children globally². A study published in 2017 reported that in Hong Kong, approximately half (55%) of preschool children have decayed teeth and almost all (93%) of such teeth are unrestored or left untreated³. Compared with a previous survey⁴, there has been no significant improvement in the caries status among Hong Kong preschool children in the intervening 20 years⁵. To monitor the severity and distribution of caries experience, several epidemiological dental survey have been conducted. However, clinical outcome measures, such as the decayed, missing and filled primary teeth (dmft) index, represent only one physical aspect of dental caries and do not reflect its impact on psychological and social factors in the affected children⁶.

Following the definition of the World Health Organization (WHO), ‘health’ is a stage of complete well-being and not just the absence of disease⁷. Evaluating patients’ perceptions is vital when planning and allocating appropriate resources to promote health and eradicate diseases⁸. Oral health-related quality of life (OHRQoL) is described as the impact of dental problems on persons and patients, affecting factors such as perception and self-esteem⁹. Several OHRQoL tools used in assessing patient-based outcomes and patients’ needs have been verified to be valid and reliable¹⁰. Nevertheless, young children usually lack the ability to think in an abstract manner, which is the basis of health perceptions. Thus, parents or primary caretakers are considered to be their representatives in observing and describing the impacts and consequences of any health problem. The Early Childhood Oral Health Impact Scale (ECOHIS) is a parental proxy measure used to assess the impact of oral diseases and dental-treatment experiences on the quality of life of young children¹¹. A recent study showed the Chinese ECOHIS to have high validity and reliability¹².

As the last community-wide oral health survey on OHRQoL and dental caries in preschool children was conducted in Hong Kong in 2011¹³ (PubMed search carried out on 15 October 2018), updated patient-based outcomes would be valuable for planning and implementing preschool oral health-care programmes. It is unknown if socio-economic status and other effect modifiers may influence the impacts of ECC on the quality of life of affected children.

The aims of this study were to investigate the association between caries experience and OHRQoL of preschool children and to investigate other risk factors associated with their OHRQoL.

METHODS

The present study received ethics approval from the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (UW 17–414). This study was performed in full accordance with ethical principles, including the World Medical Association Declaration of Helsinki. An invitation letter describing the purpose and procedures of the study was submitted to the parents of the preschool children. Written parental consent was obtained prior to implementing the study. Inclusion criteria was the ability of parents/caregivers of preschool children to read and write in Chinese. Exclusion criteria were preschool children who had major systemic illnesses or refused the dental examination. All participating children were examined in their kindergartens. The present study was carried out from 1 November 2017 to 30 April 2018.

Study population and sample size calculation

A non-probability sampling technique was adopted. We purposely selected six kindergartens that had not participated in any research study and were located in different districts from the list of participating kindergartens in the dental outreach service funded by The University of Hong Kong in 2017–2018. The G*Power 3.1.9.2 software (University of Düsseldorf, Düsseldorf, Germany) was used to estimate the sample size. In a previous study among Hong Kong preschool children, an impact on OHRQoL (i.e., an ECOHIS score of >0) was reported for approximately 70%¹³. The ratio of children having an ECOHIS score of 0 to those having an ECOHIS score of >0 was anticipated to be 0.3/0.7, with 80% power (type II error set as 0.2) and the two-sided test at the 0.05 statistical significance level. It was estimated that of all children with caries experience, an impact on OHRQoL (ECOHIS score >0) would be demonstrated by 75%, and the lowest ORs to be detected was set as 2.5¹⁴. Thus, at least 323 children in total (225 children with an ECOHIS score of >0 and 98 children with an ECOHIS score of 0) were required. With an estimated participation rate of 80%, at least 404 children would need to be invited to take part.

Questionnaire survey

A self-administered questionnaire was submitted to the parents of the study children. The questionnaires were completed at home before their children had received the dental examination. Thus, when completing the questionnaire, the respondents were unaware of their child’s caries status. This questionnaire featured two parts: (i) child and parents’ demographic background, including child’s sex and age, mother’s and father’s educational attainments and relationship of respondent to the child; and (ii) the Chinese ECOHIS, ¹² which contains two sections, as follows.

• •
  Child impact section (CIS)

  • ○
    Child symptoms – one item (toothache or oral pain)
  • ○
    Child function – four items (having difficulty in eating, drinking and pronouncing words, and missing school)
  • ○
    Child psychology – two items (trouble sleeping and frustrated/irritable)
  • ○
    Self-image/social interaction – two items (avoiding smiling and avoiding talking with others)
• •
  Family impact section (FIS)

  • ○
    Parental distress – two items (upset and guilty)
  • ○
    Family function – two items (taken day off and affecting family economy).

The response scores of the ECOHIS were as follows: score 0, never; score 1, hardly ever; score 2, occasionally; score 3, often; score 4, very often; and score 5, don’t know. The score for each individual domain, section and in total were computed as a sum of the response scores. The response ‘don’t know’ was recorded as missing. The sum ECOHIS score ranges from 0 to 52. Lower ECOHIS scores indicated lower impact on the quality of life of the child and his/her family.

Clinical examination

Dental examinations were conducted in classrooms. A single examiner (DD) had been trained and was supervised by ECML and CCH, who are specialists in dental public health. The examiner visually inspected each child’s teeth using WHO Community Periodontal Index (CPI) dental probes and disposable mirrors (MirrorLite; Kudos Crown Limited, Hong Kong) connected with an illuminated intraoral handle. Clinical data were recorded onto a paper sheet by a research assistant. The dmft index was adopted for documenting the caries experience. A tooth was noted as decayed (dt) when dentine caries was present, as filled (ft) when a permanent filling without caries was present and as missing (mt) when a tooth had been extracted because of dental caries. In the present study, dental caries was diagnosed at the cavitation level based on the WHO criteria¹⁵. The consequences of untreated caries were diagnosed using the four codes of the modified pufa index¹⁶: ‘p’ was noted when pulpal involvement was present; ‘u’ was recorded if there was ulceration; ‘f’ was recorded if a fistula was present; and ‘a’ was noted when an abscess was present. Duplicate dental examinations on approximately 10% of the participants were conducted on the same day of the dental examination to evaluate intra-examiner reliability of caries assessment. Between the duplicate examinations, at least 30 other children were examined so that the examiner did not memorise the first recording.

Statistical analysis

Data were cleaned and proofread before being transferred to a computer database for storage, and were analyzed. Cohen’s kappa coefficient (κ) was adopted to assess intra-examiner reliability regarding the caries diagnosis. The chi-square test was used to investigate the relationships between categorical variables and the impact on OHRQoL. Multiple logistic regression analysis was used to determine the child factors (sex, age, dmft, modified pufa) and parental factors (father’s education level, mother’s education level, respondent’s relationship to a child) associated with ECOHIS. The dependent variable was the impact of OHRQoL (having at least one OHRQoL impact or an ECOHIS score of >0). Regarding the independent variables, caries prevalence and modified pufa were continuous variables in model A and dichotomous variables (yes/no) in model B; all other variables in models A and B were categorised as dichotomous. The backward stepwise procedure was performed until all variables in the final model were statistically significant (P < 0.05). The level of statistical significance was set at 0.05.

RESULTS

In total, 434 children attending the second year of six selected kindergartens were invited to participate; written informed consent was provided, prior to implementation of the study, for 398 (91.7%). Thirty-six children were absent on the day of examination and therefore, in total, 362 children received the dental examination. Of these 362 children, 10 who did not return their questionnaires and 16 for whom more than two items of the ECOHIS were not given a score, were excluded. No significant difference was observed regarding the caries prevalence of those 26 children who did not return the questionnaire or for whom more than two items of the ECOHIS were not given a score, compared with those for whom the instrument was answered properly (P = 0.185, chi-square test). No significant difference was found between those 16 children for whom more than two items of the ECOHIS were not given a score and those remaining in the study regarding demographic background (age, gender, respondent and parents’ education) and caries prevalence (P > 0.05) . Thus, 336 (77.4%) children were included in the study. Among these children, eight missing values were detected. For each of these children, the mean ECOHIS score for the items given a score was calculated and inserted where scores were missing. Among the participants, 169 (50.3%) were boys. The mean age (SD) of the participants was 4.7 (0.3) years. Children’s and parents’ demographic background and clinical characteristics are shown in Table 1. Of all participants, 124 (36.9%) had caries experience (dmft ≥ 1): dmft, 1.6 (3.2); dt, 1.6 (3.0); and ft, 0.1 (0.6). None of the study children had teeth missing as a result of caries. Nearly all of the decayed teeth were unrestored: the dt component accounted for 98.5% of the dmft index. Regarding intra-examiner reliability, κ = 0.95 for caries diagnosis. The prevalence of negative consequences from untreated caries (modified pufa score of ≥ 1) was 3.3%. The mean (SD) modified pufa was 0.1 (0.5), with range 0–7. Most (86%) of the respondents were mothers. Just under half of the mothers (44.3%) and the fathers (43.4%) had attained a secondary education.

Table 1.

Parent and child’s characteristics in the study (n = 336)

Parent and child’s characteristics	Frequency	Percentage
Parent’s demographics
Relationship of the respondent to the child
Mother	289	86.0
Other family member	47	14.0
Mother’s education level
Up to junior secondary school	88	26.2
Secondary school	149	44.3
Post-secondary school/University	99	29.5
Father’s education level
Up to junior secondary school	89	26.5
Secondary school	146	43.4
Post-secondary school/University	101	30.1
Child’s demographics and caries status
Sex
Male	169	50.3
Female	167	49.7
Age (years)
4	264	78.6
5	72	21.4
Decayed teeth (dt)
dt = 0	213	63.4
dt ≥ 1	123	36.6
Missing teeth (mt)
mt = 0	336	100
mt ≥ 1	0	0
Filled teeth (ft)
ft = 0	323	96.1
ft ≥ 1	13	3.9
Decayed, missing or filled teeth (dmft)
dmft = 0	212	63.1
dmft ≥ 1	124	36.9
Oral conditions of untreated caries (Modified pufa)
Modified pufa = 0	325	96.7
Modified pufa ≥ 1	11	3.3

The frequency of ECOHIS responses is shown in Table 2. In the child section, the most frequently reported items were ‘difficulty pronouncing any words’ (51.2%) and ‘had difficulty eating some foods’ (44.0%). Parental distress, including ‘been upset’ (46.5%) and ‘felt guilty’ (41.1%), were the most commonly reported items in the family section. Overall, in the present study the ECOHIS scores ranged from 0 to 39, and 235 (70.2%) parents/caregivers reported an impact on OHRQoL (ECOHIS score > 0) for at least one ECOHIS item. However, the magnitude of impacts was low, with the mean (SD) score being 5.8 (6.2) out of 52. The mean (SD) ECOHIS scores in the child and family sections were 3.8 (4.3) and 2.0 (2.6), respectively. The responses to each ECOHIS item for children with and without caries experience are shown in Table 3. The mean (SD) ECOHIS scores of children with and without caries experience were 7.4 (7.1) and 4.8 (5.5), respectively.

Table 2.

Responses to the Chinese Early Childhood Oral Health Impact Scale (ECOHIS) items (n = 336)

Impact	ECOHIS response, n (%)					Mean (SD)
	Never	Hardly ever	Occasionally	Often	Very often
Child impact section
How often has your child …… because of dental problems or the need for dental treatments?
Child symptom
a) Had pain in the teeth, mouth or jaws?	201 (59.8)	102 (30.4)	28 (8.3)	4 (1.2)	1 (0.3)	0.5 (0.7)
Child function
b) Had difficulty drinking beverages?	211 (62.8)	107 (31.8)	16 (4.8)	2 (0.6)	0 (0)	0.4 (0.6)
c) Had difficulty eating some foods?	188 (56.0)	103 (30.7)	37 (11.0)	6 (1.8)	2 (0.6)	0.6 (0.8)
d) Had difficulty pronouncing words?	164 (48.8)	93 (27.7)	66 (19.6)	9 (2.7)	4 (1.2)	0.8 (0.9)
e) Missed preschool, day care?	274 (81.5)	59 (17.6)	2 (0.6)	1 (0.3)	0 (0)	0.2 (0.4)
Child psychology
f) Had trouble sleeping?	250 (74.4)	71 (21.1)	12 (3.6)	2 (0.6)	1 (0.3)	0.3 (0.6)
g) Been irritable or frustrated?	216 (64.3)	97 (28.9)	19 (5.7)	2 (0.6)	2 (0.6)	0.4 (0.7)
Self-image and social interaction
h) Avoided smiling or laughing?	259 (77.1)	69 (20.5)	7 (2.1)	1 (0.3)	0 (0)	0.3 (0.5)
i) Avoided talking with other children?	260 (77.4)	72 (21.4)	3 (0.9)	1 (0.3)	0 (0)	0.2 (0.5)
Family impact section
How often have you or another family member because of your child’s dental problems or treatment?
Parental distress
j) Been upset?	183 (54.5)	105 (31.3)	39 (11.6)	8 (2.4)	1 (0.3)	0.6 (0.8)
k) Felt guilty?	198 (58.9)	89 (26.5)	38 (11.3)	7 (2.1)	4 (1.2)	0.6 (0.9)
Family function
l) Had to take hours or days off work?	239 (71.1)	81 (24.1)	12 (3.6)	3 (0.9)	1 (0.3)	0.4 (0.6)
m) Had the family’s economic situation affected?	234 (69.6)	83 (24.7)	15 (4.5)	3 (0.9)	1 (0.3)	0.4 (0.6)

Table 3.

Responses to the Chinese Early Childhood Oral Health Impact Scale (ECOHIS) responses from children with (n = 124) and children without (n = 212) caries experience

Impact	ECOHIS response, n (%)					Mean (SD)
	Never	Hardly ever	Occasionally	Often	Very often
Children with caries experience (n = 124)
Child impact section
Child Symptom
a) Had pain in the teeth, mouth or jaws?	59 (47.6)	44 (35.5)	16 (12.9)	4 (3.2)	1 (0.8)	0.7 (0.9)
Child function
b) Had difficulty drinking beverages?	65 (52.4)	46 (37.1)	12 (9.7)	1 (0.8)	0 (0)	0.6 (0.7)
c) Had difficulty eating some foods?	58 (46.8)	47 (37.9)	17 (13.7)	2 (1.6)	0 (0)	0.7 (0.8)
d) Had difficulty pronouncing words?	57 (46)	39 (31.5)	24 (19.4)	3 (2.4)	1 (0.8)	0.8 (0.9)
e) Missed preschool, day care?	92 (74.2)	29 (23.4)	2 (1.6)	1 (0.8)	0 (0)	0.3 (0.5)
Child psychology
f) Had trouble sleeping?	81 (65.3)	38 (30.6)	4 (3.2)	1 (0.8)	0 (0)	0.4 (0.6)
g) Been irritable or frustrated?	74 (59.7)	45 (36.3)	4 (3.2)	1 (0.8)	0 (0)	0.5 (0.6)
Self-image and social interaction
h) Avoided smiling or laughing?	86 (69.4)	34 (27.4)	3 (2.4)	1 (0.8)	0 (0)	0.4 (0.6)
i) Avoided talking with other children?	88 (71)	34 (27.4)	1 (0.8)	1 (0.8)	0 (0)	0.3 (0.5)
Family impact section
Parental distress
j) Been upset?	56 (45.2)	42 (33.9)	18 (14.5)	7 (5.6)	1 (0.8)	0.8 (0.9)
k) Felt guilty?	54 (43.5)	43 (34.7)	19 (15.3)	5 (4)	3 (2.4)	0.9 (1.0)
Family function
l) Had to take hours or days off work?	73 (58.9)	40 (32.3)	8 (6.5)	2 (1.6)	1 (0.8)	0.5 (0.8)
m) Affected family’s economic situation?	73 (58.9)	40 (32.3)	8 (6.5)	2 (1.6)	1 (0.8)	0.5 (0.8)
Children without caries experience (n = 212)
Child impact section
Child symptom
a) Had pain in the teeth, mouth or jaws?	142 (67)	58 (27.4)	12 (5.7)	0 (0)	0 (0)	0.4 (0.6)
Child Function
b) Had difficulty drinking beverages?	146 (68.9)	61 (28.8)	4 (1.9)	1 (0.5)	0 (0)	0.3 (0.5)
c) Had difficulty eating some foods?	130 (61.3)	56 (26.4)	20 (9.4)	4 (1.9)	2 (0.9)	0.6 (0.8)
d) Had difficulty pronouncing words?	107 (50.5)	54 (25.5)	42 (19.8)	6 (2.8)	3 (1.4)	0.8 (1.0)
e) Missed preschool, day care?	182 (85.8)	30 (14.2)	0 (0)	0 (0)	0 (0)	0.1 (0.3)
Child psychology
f) Had trouble sleeping?	169 (79.7)	33 (15.6)	8 (3.8)	1 (0.5)	1 (0.5)	0.3 (0.6)
g) Been irritable or frustrated?	142 (67)	52 (24.5)	15 (7.1)	1 (0.5)	2 (0.9)	0.4 (0.7)
Self-image and social interaction
h) Avoided smiling or laughing?	173 (81.6)	35 (16.5)	4 (1.9)	0 (0)	0 (0)	0.2 (0.4)
i) Avoided talking with other children?	172 (81.1)	38 (17.9)	2 (0.9)	0 (0)	0 (0)	0.2 (0.4)
Family impact section
Parental distress
j) Been upset?	127 (59.9)	63 (29.7)	21 (9.9)	1 (0.5)	0 (0)	0.5 (0.7)
k) Felt guilty?	144 (67.9)	46 (21.7)	19 (9)	2 (0.9)	1 (0.5)	0.4 (0.7)
Family function
l) Had to take hours or days off work?	166 (78.3)	41 (19.3)	4 (1.9)	1 (0.5)	0 (0)	0.3 (0.5)
m) Affected family’s economic situation?	161 (75.9)	43 (20.3)	7 (3.3)	1 (0.5)	0 (0)	0.3 (0.5)

Bivariate analysis of various factors related to the overall impacts, child impacts and family impacts are displayed in Table 4. In total, 79% of the children who had caries experience reported an impact on OHRQoL. The dt and caries experience (dmft) were statistically associated with the CIS and FIS of the ECOHIS and with the overall section (P < 0.05, chi-square test), whereas other factors were not. For the FIS, child’s sex was associated with the family impact (P = 0.049, chi-square test). Table 5 shows the results of the final logistic regression model of significant factors associated with an ECOHIS of >0 in the CIS, FIS and the overall (child and family) sections. After adjusting for the father’s and mother’s educational attainment, relationship of respondent to a child, child’s sex and age, and consequences of untreated dental caries (modified pufa), caries experience (dmft score) was the only significant variable affecting OHRQoL of children and families (overall ECOHIS score > 0) (OR = 1.20, 95% CI: 1.07–1.35, P = 0.002). The results of the Hosmer and Lemeshow test (P = 0.732) implied goodness of fit with a P > 0.05. For the FIS, parents having a son were 1.63 times more likely to have a higher negative impact on their OHRQoL, compared with parents who had a daughter (95% CI: 1.04–2.56, P = 0.032). When using caries experience as a categorical variable (yes/no) instead of a continuous variable (dmft score), caries experience was 2.02 times as likely to have a negative impact on a child’s OHRQoL compared with no caries experience (95% CI: 1.20–3.39, P = 0.008).

Table 4.

Bivariate analysis of various factors related to the Chinese Early Childhood Oral Health Impact Scale

Variable	% of child impacts (CIS score > 0)	% of family impacts (FIS score > 0)	% of overall impact (ECOHIS > 0)
Parent demographics
Relationship to the child
Mother	64.0% (185/289)	48.1% (139/289)	70.2% (203/289)
Other family member	66.0% (31/47)	46.8% (22/47)	70.2% (33/47)
Mother’s education level
Lower secondary school or lower	60.2% (53/88)	50.0% (44/88)	65.9% (58/88)
Secondary school	71.1% (106/149)	47.0% (70/149)	75.2% (112/149)
Post-secondary school/University	57.6% (57/99)	47.5% (47/99)	66.7% (66/99)
Father’s education level
Lower secondary school or lower	64.0% (57/89)	47.2% (42/89)	68.5% (61/89)
Secondary school	65.8% (96/146)	48.6% (71/146)	70.5% (103/146)
Post-secondary school/University	62.4% (63/101)	47.5% (48/101)	71.3% (72/101)
Child demographics and caries status
Sex		*
Male	67.5% (114/169)	53.3% (90/169)	73.4% (124/169)
Female	61.1% (102/167)	42.5% (71/167)	67.1% (112/167)
Age (years)
4	68.2% (180/264)	62.9% (166/264)	46.2% (122/264)
5	77.8% (56/72)	69.4% (50/72)	54.2% (39/72)
Decayed teeth (dt)	*	**	**
dt = 0	59.6% (127/213)	40.8% (87/213)	65.3% (139/213)
dt ≥ 1	72.4% (89/123)	60.2% (74/123)	78.9% (97/123)
Missing teeth (mt)
mt = 0	64.3% (216/336)	47.9% (161/336)	70.2% (236/336)
mt > 1	NA	NA	NA
Filled teeth (ft)
ft = 0	64.4% (208/323)	47.1% (152/323)	70.3% (227/323)
ft ≥ 1	61.5% (8/13)	69.2% (9/13)	69.2% (9/13)
Decayed, missing or filled teeth (dmft)	*	***	**
dmft = 0	59.9% (127/212)	40.6% (86/212)	65.1% (138/212)
dmft ≥ 1	71.8% (89/124)	60.5% (75/124)	79% (98/124)
Modified pufa
Modified pufa = 0	69.5% (226/325)	63.4% (206/325)	47.4% (154/325)
Modified pufa ≥ 1	90.9% (10/11)	90.9% (10/11)	63.6% (7/11)

CIS, child impact section; FIS, family impact section; NA, not applicable; pufa, oral conditions of untreated caries.

Chi-square test, *P < 0.05, **P < 0.01, ***P < 0.001.

Table 5.

Final model of logistic regression of ECOHIS

	Odds ratio	95% CI	P value
Model A: Caries experience(dmft score) and modified pufa -continuous variables
Child impacts†
dmft score	1.18	1.07–1.31	0.001
Family impacts‡
dmft score	1.23	1.12–1.35	<0.001
Child’s sex			0.032
Female*
Male	1.63	1.04–2.56
Overall (Child+Parent) impacts†
dmft score	1.20	1.07–1.35	0.002
Model B: Caries experience and modified pufa (yes/no)-categorical variables
Child impacts†
Caries experience (yes/no*)	1.70	1.06–2.75	0.029
Family impacts‡
Caries experience (yes/no*)	2.30	1.46–3.63	<0.001
Child’s sex
Female*
Male	1.61	1.03–2.50	0.035
Overall (Child+Parent) impacts†
Caries experience (yes/no*)	2.02	1.21–3.39	0.008

^*Reference group; CI, confidence interval.

^†Excluded variables: relationship of respondent to a child, education level of mother and father, child’s sex and age, modified pufa.

^‡Excluded variables: relationship of respondent to the child, education level of mother and father, child’s age, modified pufa.

DISCUSSION

Quality of life has important implications for health research and practice¹⁰. Subjective oral health status should be considered when assessing oral health status and perceived needs in a community⁸. The results of the present study indicate that although the overall impact of oral health was not high (scoring 5 out of 52), the majority (70%) of the parents reported an adverse effect on OHRQoL (ECOHIS score of > 0) for at least one item. Parents reported a slightly higher adverse effect of caries on OHRoL in the current study compared with a previous population-based survey¹³. This may be because the children in the present study were older than those in the previous study (4.7 years vs. 3.9 years) and had higher caries prevalence (36.9% vs. 19.9%)¹³.

Regarding the association between OHRQoL and dental caries, the chances of having negative impacts were observed among children with higher caries experience. For every one unit increase in dmft score, the chance of having an impact on a child’s OHRQoL was 1.2 times as likely. This is in agreement with the results of studies conducted in diverse geographical areas such as Brazil¹⁷, France¹⁸ and Trinidad¹⁴. The caries status of Hong Kong preschool children has not been improved in the last decade. No third-party payment coverage or government-subsidised dental care services exist for preschool children in Hong Kong¹⁹. Our results corroborate the evidence that untreated caries has ramifications not just for oral health but also for the general health of the affected children20, 21. The burden of ECC and its impacts beyond the clinical aspects suggest the need to address specific strategies to improve dental health in childhood. Effective evidence-based approaches, including a supervised toothbrushing program with fluoridated toothpaste and topical fluoride treatment in a school setting, should be established to improve the oral health of Hong Kong preschool children⁵.

In the current study, the most frequently reported domains were symptoms and functional limitations, whereas the domains of child self-image and social interaction were reported least frequently. These results are consistent with those in previous studies17, 18. Thus, pain relief and functional improvement should be primary treatment goals for managing tooth decay in young children. In the current situation where most cavities are untreated, simple and cost-effective approaches, such as silver diamine fluoride therapy, may be beneficial in preventing and controlling disease progression²². Although no missing teeth due to caries (mt) were recorded, difficulty pronouncing any words was the prevalent OHRQoL impact rated by parents. Possibly, this may be related to non-caries-related factors, such as malocclusion or previous traumatic dental injury. Although the results of the Hosmer–Lemeshow test implied goodness of fit with P > 0.05, the association of other unmeasured oral conditions with an impact on OHRQoL should be further explored. In the family section, guilty and upset feeling by the parents were the most frequently reported impacts, which were similar to the results of previous studies18, 20. Within the same ethnic group, Chinese parents in Hong Kong had higher distress than those in Mainland China, although the status of their children’s caries was similar²³. The discrepancy in parental responses may be a result of the different social and economic development in these two areas.

Socio-economic status has been found to be one of the risk factors associated with dental caries²⁴. In addition, children from low social classes had worse OHRQoL after adjustment for potentially confounding factors²⁵. Conflicting findings were published²⁶. In the present study, no association between socio-economic status and OHRQoL was observed. Although mothers and fathers were allowed to be proxies in the present study, most (86%) were mothers. The depth of awareness and agreement in child’s oral health between proxies may be different. Following the results of multivariate logistic regression analysis, relationship of respondent to child (either mother or others) had no effect on child’s OHRQoL. Interestingly, association between the child’s gender and parental distress was observed. Parents having a boy had higher negative family impacts than those having a girl, even after adjustment. This may be due to the patrilineal culture. Gender values in Chinese sociocultural contexts were associated with the functionality of family in several aspects, including child-rearing²⁷. This may lead to higher parental expectation and social pressure when parenting a boy. The parent–child relationship is complex and individualised²⁸. Social and behavioural factors influencing child oral health should be further studied.

The strengths of this study include the use of a validated OHRQoL measure, good intra-examiner reliability of the dental examination, acceptable participation rates and sufficient sample size. Several study limitations should be addressed. The reliability of the parents’ answers was not assessed. In addition, the study children were selected using a non-probability sampling method. Moreover, the caries prevalence (36.9%) of the study children aged 4 years was lower than that (43.1%) of the same age group in a recent territory-wide oral health survey²⁹. However, parental educational attainment in the present study was similar to that of the Hong Kong population overall regarding attainment of secondary (47.3%) and higher (32.7%) education levels³⁰. As a result of the sampling bias from non-probability sampling, we cautiously make inferences from these study samples to the general population. In addition, this was a cross-sectional study; the exposure (dental caries), outcome (ECOHIS) and other confounding factors were simultaneously evaluated. Thus, there is no evidence regarding a temporal relationship between dental caries and OHRQoL. Recall bias also possibly influenced the caregivers’ responses. The adoption of parent proxy may not be ideal, but it is satisfactory and reasonable given the linguistic and cognitive aspects of early childhood³¹. A well-designed prospective study using representative samples is required to provide more information regarding the causal effect of dental caries on OHRQoL of the affected children and their families.

Dental caries in primary teeth may be a potential health problem, with repercussions extending beyond its clinical signs and symptoms. An increase of more than one decayed primary tooth has a significantly negative impact on the OHRQoL of the affected children and families. However, the magnitude of the perceived impact on OHRQoL was low in Hong Kong. Attention should be paid, at a broader policy level, to increase knowledge and awareness as well as to improve access to oral care for preschool children, thus improving the quality of life of preschool children.

In summary, caries experience of preschool children is significantly associated with negative family and child experiences, contributing to a lower OHRQoL, regardless of their socio-economic status.

Acknowledgements

The authors thank Ms Samantha K, Y Li for her assistance with statistical analysis. This study did not receive any financial support from funding agencies.

Conflict of interests

All authors declare no conflict of interest.