This cross-sectional study was conducted in Ernakulam District, Kerala for a period of two months from February to March 2017. According to a previous study, 43.1%children had an impact on daily performances due to oral health problems [7]. The sample size was calculated based on this study using the formula n= 4PQ/d², where P stands for prevalence, Q is (1-P), and d is the allowable error which was 20%of P. From this the sample size was estimated to be 85. Since the study involves a cluster (schools as clusters) sampling method, sample size is multiplied by two and was estimated to be 170. Multistage random sampling was done to select the schools. The list of all upper primary schools was obtained and stratified under Private and Government schools. Three Government schools and two Private schools were randomly chosen using a random table. All 12-year-old children in seventh standard of the selected schools were included in the study based on cluster sampling which comprised of 281 Children and was considered adequate.

Children of only 12 years of age willing to take part in the study were included. Children who have cognitive impairment or chronic diseases were excluded from the study.

Prior information sheets and consent forms were sent to Parents through children. Ethical Committee approval was obtained from the institution, and authority consents were taken from the Head of the respective schools.

The data collection included self-administered COHIP questionnaire and oral examinations. The growth and eruption patterns of the teeth cannot be universally applied owing to ethnic variations. The standards for tooth eruption patterns derived from a western population cannot be extrapolated to an Indian scenario. The mean eruption ages of second molars can vary from 11.9±1.17 years to 12.64±1.13 years among South Indian children [8]. Hence, each child was given a separate index, one for permanent teeth (DMFT) and another for primary teeth (deft). The children underwent oral examinations and the deft (aggregate of decayed, extracted and filled teeth in the primary dentition) [9] and DMFT (aggregate of decayed, missing and filled teeth in the permanent dentition) indices were recorded to assess Dental Caries [10]. The examinations were conducted in the classrooms under natural light and artificial illumination was used whenever required. The oral examination was performed by a single investigator. The intra-examiner reliability was confirmed by directing replicate examinations in 20 people, a kappa score of 0.95 was obtained for DMFT/deft.

The COHIP comprises of 34 questions that attempted to get an idea of a child’s oral health status on five domains identified with oral health, functional well-being, social–emotional well-being, school environment and self image [11]. Participants are instructed to report on the frequency of events in the course of recent three months on a five-point Likert scale which is scored from 0-4. The responses for the five domains and the individual scores were: ‘Never’ (scoring 4); ‘Almost never’ (3); ‘Sometimes’ (2); ‘Fairly Often’ (1); and ‘Almost all the time’ (0). There were both positive and negative inquiries. The scores of the negative inquiries were reversed, with lower total COHIP scores indicating poorer oral health related quality of life. Frequency for each domain was calculated after assigning weights for each option considering positive and negative questions. For 34 questions the scores extended from 0 to 136 for which a higher score meant agreeable OHRQoL [11]. The questionnaire was self-administered and each child took around 20 minutes to complete the survey after which the survey sheets were collected back. The survey had inquiries in both English and regional language (Malayalam). The Cronbach’s alpha score for reliability test for the regional language questionnaire was 0.81.

Data analysis was done using the SPSS version 20 (SPSS Inc., Chicago, IL, USA).

For continuous data means and standard deviations were calculated. For categorical variables respective frequencies were generated. Correlation between each domain of questionnaire and Decay component of DMFT was analysed using Pearson’s correlation co-efficient. Statistical significance was set at 5%(p < 0.05).

The examination was conducted in 281 school children aged 12 years (43.77%males). 188 students in the sample belonged to Government schools (66.9%) and 93 students were from Private schools. COHIP scores obtained ranged from 42 to 132 [Table/Fig-1]. The mean COHIP score was 101.58 (±15.66). The caries prevalence in this population was found to be 71.5%.

Around 43.4%of children has experienced toothache often in the past three months. Due to oral health problems, 45.6%of children had missed school during the same period [Table/Fig-2].

The caries prevalence among government and private schools were found to be 71.8% and 71% respectively. Correlation between DMFT and COHIP scores were not significant in both Government and Private schools [Table/Fig-3].

An inverse correlation was obtained for all domains of the COHIP questionnaire except self image with dental caries experience, but it was not found to be significant [Table/Fig-4]. Overall mean DMFT and deft scores did not had any significant correlation with any of the five domains of the COHIP questionnaire. The association between healthy school environment (Domain 4) and decay component (D) of DMFT was found to be significant (p-value – 0.024) [Table/Fig-5].

The percentile distribution of COHIP scores with caries experience is given in [Table/Fig-6]. Considering the percentile distribution, children with a COHIP score below 78.32 indicating poor oral health related quality of life had a greater share of caries experience (12.5%) than children without caries (7.96%).

With the emergence of psycho social factors affecting health, subjective assessment of oral health has gained much significance today. The assessment of the extent to which oral health affects a child’s quality of life can gain insights into devising effective public health interventions. Connecting dental caries to oral health related quality of life is a much researched area. But there is an ambiguity on which is the ideal tool to make this connection. The method of reasoning behind opting COHIP to asses OHRQoL and connecting it to dental caries in this population is the capacity of this instrument to segregate between groups relying upon their experience of dental caries [11].

Children from two different categories of schools (Government and Private) are assessed in this study, thus facilitating comparison of oral health quality of life among two different strata of socioeconomic class. The COHIP questionnaire tool used to assess this has been rated as having excellent content development methodology, thereby adding to the strength of this study [6]. The selected age group of 12 years is also appropriate owing to the fact that all permanent teeth except third molars are erupting in this age. Thus, making this age group ideal for global monitoring of caries and for comparison of disease trends (WHO, 1997) [12]. The original questionnaire was translated into the regional language in this study. However, there is also a need for cross cultural adaptation for this questionnaire to Indian settings and validation of the same in order to achieve equivalence.

The general attitude of Indian society to oral diseases is of low priority and neglect even though there is a high prevalence of oral diseases and morbidity [13]. This may be a cause for no significant difference in the COHIP scores between the two socioeconomic classes owing to low priority for oral health. This is a self-administered questionnaire and one of the difficulties the children reported while answering was that the demarcation between the different response was not clear cut. For example, choosing responses between never, almost never, almost all the time and all the time, may be confusing to children of this age group, which suggests the need for clubbing of responses in the future for this age group.

The prevalence of dental caries across India ranges from 30% to 95% [14]. In the present study, the dental caries prevalence was found to be 71.5%, which can be considered as high. The two different types of schools—government and private can be used as a proxy for socioeconomic status [15]. The socioeconomic status may not be a risk factor for high prevalence of dental caries in this study since the caries prevalence were similar in government (71.8) and Private (71) schools. The cause for the high prevalence of dental caries needs to be further explored with focus on dietary factors and oral hygiene practices.

The COHIP mean score in this study (101.58±15.66) is found to be very similar to that of French COHIP mean score (101.9±16.84) [11]. The scores when compared, are higher in the USA and Canada indicating better oral health related quality of life in these countries [16]. Lower COHIP scores are noticed in countries like Korea and Iran indicating poorer OHRQoL [17,18].

In our literature search we couldn’t find any study in India using the complete 34 item COHIP questionnaire, only studies with the short form of COHIP (19 item) is available which made the comparisons difficult. The results of that study confirmed that dental caries lead to reduced OHRQoL in children [19]. Also, there is a need for a global score to identify and make comparisons and inferences from the scoring. Studies using other types of Child OHRQoL questionnaires are showing similar results that, dental caries has a significant association with low OHRQoL in India as well as other countries [7,4,19]. In a study where the Dental Health Status (DHS) and child OHRQoL was assessed, it was found that children with two or more carious teeth suffered from significantly higher oral symptoms and functional limitations compared with those having less than two carious teeth [20]. This finding strikes a similar chord with our findings, in which 79%of children had problems with chewing or biting food fairly often.

Around 43.4%children have often experienced toothache at least once in three months. Almost 68%children had often missed their school due to oral health problems. This is in line with other studies which has proved that children with poor oral health status will probably encounter dental pain, miss school, and perform inefficiently in academics, thereby indicating that improvement in the oral health related quality of life will indeed enhance their educational experience [21-23]. Similar results were also obtained in a study conducted among disadvantaged children. Thus, the loss of school hours can be considered as a useful statistic in measuring the impact of oral health in school children [24].

The necessity of maintaining adequate oral health for achieving optimum general health, needs to be taught to school children from a very young age. Therefore integration of oral health education into the school health curriculum is highly recommended.

Even though toothache and dental caries is present in high proportions in these children it does not correlate significantly with COHIP score. This may be attributed to the variation of perceptions between various cultures for which cross-cultural adaptation may be a solution, which is a limitation of this study.

The dental caries prevalence in this study population was found to be high (71.5%). But there was no significant correlation between the mean DMFT and deft scores and the domains of the COHIP questionnaire. However, an association was found to be significant between the domain school environment and decay component (D) of DMFT (p-value–0.024). The results suggest that dental caries has a negative effect on the oral health related quality of life. Accurate oral health indicators like oral health impact profile is necessary to plan successful oral health interventions in children.