Oral health is an integral component of general health and well-being and is essential for growth, nutrition and quality of life from childhood onwards. Oral diseases are among the most common non-communicable conditions worldwide, affecting close to 3.5 billion people [1]. Dental caries is driven largely by frequent intake of free sugars, inadequate fluoride exposure and insufficient removal of dental plaque [2]. Children with special health care needs are those with any physical, developmental, mental, sensory, behavioural, cognitive or emotional impairment or limiting condition that requires medical management, health care intervention and/or the use of specialised services or programmes [3]. The Rights of Persons with Disabilities Act, 2016 recognises 21 categories of disability in India, including blindness, hearing impairment, intellectual disability and cerebral palsy [4]. According to the Census of India 2011, approximately 26.8 million people, or 2.21% of the population, live with a disability [5]. Children with disabilities are at increased risk of oral disease throughout life. Although their oral health may initially resemble that of their peers, diet and feeding patterns, long-term medication, physical limitations, limited ability to clean the teeth, and the attitudes of parents and health care providers contribute to its progressive decline [6]. Difficulty in establishing routine oral care, a lack of effective preventive strategies and inadequate supervision of oral hygiene by caregivers compound this risk [7,8]. Supplementary practices such as flossing and mouth rinsing are seldom followed [9]. Limited comprehension of oral hygiene instructions, difficulty in communicating symptoms, and inadequate training or reluctance among dental practitioners to treat these children further restrict care [10]. Children with intellectual disability, in particular, often lack the motor coordination and understanding required for effective daily toothbrushing [11], and limited oral health awareness among parents has been linked to higher caries experience [12]. Transportation difficulties, limited access to treatment and poor inter-professional coordination add further barriers [10]; because these children may not communicate symptoms clearly, disease is often detected late [13]. Medications that reduce salivary flow or contain sugars may also predispose them to oral disease [14]. Consequently, children with disabilities carry a higher burden of untreated oral disease than their typically developing peers, and oral health remains one of their greatest unmet health needs [15,16]. Although the oral health of children without disabilities has been studied extensively in India, relatively few studies have focused on children with disabilities in special-school settings, and no published data are available from the Union Territory of Dadra and Nagar Haveli and Daman and Diu. Such local evidence is needed to plan targeted preventive services. The aim of this study was therefore to assess the oral hygiene status of children with disabilities attending a special school in Silvassa. The specific objectives were (i) to assess oral hygiene status using the Oral Health Index for Children (OHI-C); (ii) to estimate the prevalence of dental caries and gingival inflammation; and (iii) to compare oral hygiene status across disability categories.

Study design and setting A school-based cross-sectional study was conducted over a period of four months [specify month–month and year of data collection] at a special school for children with disabilities in Silvassa, Union Territory of Dadra and Nagar Haveli and Daman and Diu, India. The study is reported in accordance with the STROBE guidelines for cross-sectional studies. Participants and eligibility Children aged 5–15 years enrolled in the school with intellectual disability, hearing impairment, visual impairment or developmental delay were eligible, provided that written informed consent was given by a parent or legal guardian. Children who had received any dental treatment in the preceding year, who could not cooperate with a dental examination because of the severity of their disability, who were absent on the days of examination, or whose parents did not consent were excluded. Sample size The sample size was calculated using Statulator. Assuming an expected proportion of 50% (to maximise sample size), an absolute precision of 5% and a 95% confidence level, the required sample for an infinite population was 385. Applying the finite population correction for the 150 children enrolled in the school [n = 385 / (1 + 384/150)] yielded a required sample of 108 children. Sampling technique Children were stratified by disability category, and the sample was allocated to each stratum in proportion to its size; participants were then selected from each stratum by simple random sampling. The final sample comprised 67 children with intellectual disability, 35 with hearing impairment and 6 with visual impairment. Data collection tool Data were collected using a pre-tested, structured proforma recording demographic details (age, sex and residence), type of disability and the findings of the clinical oral examination. For this study, oral health was defined as a standard of health of the oral and related tissues that enables an individual to eat, speak and socialise without active disease, discomfort or embarrassment and that contributes to general well-being [17]. Clinical examination Clinical examinations were conducted on the school premises under natural daylight with the child seated on an ordinary chair by the dental faculty investigator (SK) and trained undergraduate investigators. Examiners were trained and calibrated before the survey. Infection-control precautions were followed, and sterile mouth mirrors and short-shank spoon excavators were used. The mouth was examined quadrant by quadrant in a clockwise sequence starting from the maxillary right quadrant. Oral hygiene was assessed using the Oral Health Index for Children (OHI-C) described by Takate et al. [18]. Six index teeth were examined, one tooth per sextant, with the primary tooth scored where the permanent tooth had not erupted: 16/55, 11/51, 26/65, 36/75, 31/71 and 46/85. Each tooth was scored from 0 to 4 (0, no materia alba, plaque, stain or calculus; 1, materia alba or plaque around the free gingival margin; 2, materia alba, plaque or extrinsic stain covering not more than one-third of the clinical crown; 3, materia alba, plaque or extrinsic stain covering about half of the clinical crown; 4, materia alba, plaque or extrinsic stain covering more than half of the clinical crown, or calculus regardless of the area covered). The OHI-C score was calculated as the total score divided by the number of teeth examined and categorised as very good (< 0.5), good (0.5–1.0), average (1.1–2.0), bad (2.1–3.0) or very bad (> 3.0) [18]. Dental caries was recorded as present when a visible carious lesion was detected on any tooth, and gingival inflammation was recorded as present when visible clinical signs of gingival inflammation redness, swelling or bleeding of the marginal gingiva were observed. Ethical considerations The study was approved by the Institutional Ethics Committee of NAMO Medical Education and Research Institute, Silvassa (Letter No. NAMOMERI-SVBCH/IEC/2023-24/230) before data collection began and was conducted in accordance with the Declaration of Helsinki. Permission was obtained from the school authorities. Written informed consent was obtained from the parent or legal guardian of every participant. Data were anonymised using unique identification numbers, and confidentiality was maintained throughout. Statistical analysis Data were entered in Microsoft Excel and analysed using SPSS software. Categorical variables are presented as frequencies and percentages, with 95% confidence intervals (Wilson method) for prevalence estimates, and OHI-C scores as mean ± standard deviation (SD). The association of dental caries with age group and sex was assessed with Pearson’s chi-square test. Mean OHI-C scores were compared across disability categories using one-way analysis of variance (ANOVA) with Tukey–Kramer post-hoc comparisons. To compare the distribution of OHI-C categories, categories were collapsed into three levels (very good/good, average and bad/very bad), and children with intellectual disability were compared with those with sensory impairment (hearing and visual impairment combined, because the visual impairment group was too small for separate analysis) using the chi-square test. A p-value < 0.05 was considered statistically significant.

All 108 sampled children were examined. Of these, 72 (66.7%) were boys, 76 (70.4%) were aged 12–15 years, and 94 (87.0%) resided in Silvassa. Intellectual disability was the most common disability (62.0%), followed by hearing impairment (32.4%) and visual impairment (5.6%) (Table 1). The overall mean OHI-C score was 1.54 ± 0.74. Average oral hygiene was the most frequent category (50; 46.3%), followed by good (27; 25.0%), bad (25; 23.1%), very good (4; 3.7%) and very bad (2; 1.9%). Overall, 27 children (25.0%; 95% CI 17.8–33.9) had bad or very bad oral hygiene (Table 2). Oral hygiene differed by disability category. Children with intellectual disability had the highest proportion of bad or very bad oral hygiene (21/67; 31.3%), and no child in this group had very good oral hygiene. Among children with hearing impairment, 14 (40.0%) had good or very good oral hygiene and none had very bad oral hygiene; three of the six children with visual impairment had good oral hygiene. The distribution of OHI-C categories differed significantly between children with intellectual disability and those with sensory impairment (χ² = 6.67, df = 2, p = 0.036) (Table 2). Mean OHI-C scores fell within the average category in all three groups but differed significantly across them (F = 5.35, df = 2, 105; p = 0.006). The mean score of children with intellectual disability (1.71 ± 0.73) was significantly higher than that of children with hearing impairment (1.27 ± 0.68; mean difference 0.44, p = 0.011). Differences between intellectual and visual impairment (p = 0.151) and between hearing and visual impairment (p = 0.911) were not statistically significant (Table 3). Dental caries was present in 58 children (53.7%; 95% CI 44.3–62.8) and gingival inflammation in 5 (4.6%; 95% CI 2.0–10.4) (Table 4). The prevalence of caries was 60.0% in children aged 5–7 years, 63.6% in those aged 8–11 years and 50.0% in those aged 12–15 years (χ² = 1.45, df = 2, p = 0.484), and 52.8% in boys and 55.6% in girls (χ² = 0.07, df = 1, p = 0.785); neither difference was statistically significant (Table 5). Table 1. Sociodemographic characteristics and disability categories of the study participants (n = 108) Variable Category n % Sex Male 72 66.7 Female 36 33.3 Age group (years) 5–7 10 9.3 8–11 22 20.4 12–15 76 70.4 Residence Silvassa 94 87.0 Outside Silvassa 14 13.0 Disability category Intellectual disability 67 62.0 Hearing impairment 35 32.4 Visual impairment 6 5.6 Table 2. Distribution of OHI-C categories by disability category (n = 108) OHI-C category (score) Intellectual disability (n = 67) n (%) Hearing impairment (n = 35) n (%) Visual impairment (n = 6) n (%) Total (n = 108) n (%) Very good (< 0.5) 0 (0.0) 4 (11.4) 0 (0.0) 4 (3.7) Good (0.5–1.0) 14 (20.9) 10 (28.6) 3 (50.0) 27 (25.0) Average (1.1–2.0) 32 (47.8) 16 (45.7) 2 (33.3) 50 (46.3) Bad (2.1–3.0) 19 (28.4) 5 (14.3) 1 (16.7) 25 (23.1) Very bad (> 3.0) 2 (3.0) 0 (0.0) 0 (0.0) 2 (1.9) Bad or very bad 21 (31.3) 5 (14.3) 1 (16.7) 27 (25.0) OHI-C, Oral Health Index for Children. Very good/good vs average vs bad/very bad, intellectual disability vs sensory impairment (hearing + visual): χ² = 6.67, df = 2, p = 0.036. Table 3. Mean OHI-C score by disability category (n = 108) Disability category n Mean ± SD 95% CI Interpretation Intellectual disability 67 1.71 ± 0.73 1.53–1.89 Average Hearing impairment 35 1.27 ± 0.68 1.04–1.50 Average Visual impairment 6 1.14 ± 0.71 0.39–1.89 Average Total 108 1.54 ± 0.74 1.40–1.68 Average One-way ANOVA: F = 5.35, df = 2, 105; p = 0.006. Tukey–Kramer post-hoc: intellectual disability vs hearing impairment, p = 0.011; intellectual disability vs visual impairment, p = 0.151; hearing vs visual impairment, p = 0.911. SD, standard deviation; CI, confidence interval. Table 4. Prevalence of dental caries and gingival inflammation (n = 108) Condition Present, n (%) Absent, n (%) 95% CI for prevalence (%) Dental caries 58 (53.7) 50 (46.3) 44.3–62.8 Gingival inflammation 5 (4.6) 103 (95.4) 2.0–10.4 CI, confidence interval (Wilson method). Table 5. Association of dental caries with age group and sex (n = 108) Variable Category Caries present n (%) Caries absent n (%) χ² (df) p-value Age group (years) 5–7 (n = 10) 6 (60.0) 4 (40.0) 1.45 (2) 0.484 8–11 (n = 22) 14 (63.6) 8 (36.4) 12–15 (n = 76) 38 (50.0) 38 (50.0) Sex Male (n = 72) 38 (52.8) 34 (47.2) 0.07 (1) 0.785 Female (n = 36) 20 (55.6) 16 (44.4) Pearson’s chi-square test; percentages are row percentages.

This study describes the oral health of children with disabilities attending a special school in Silvassa, a population for which no previous data were available. Three principal findings emerged: oral hygiene was predominantly average, with one in four children having bad or very bad oral hygiene; children with intellectual disability had significantly poorer oral hygiene than those with hearing impairment; and more than half of the children had dental caries. The caries prevalence of 53.7% in this study is lower than the pooled prevalence of 64% (95% CI 45–79%) reported in a recent meta-analysis of Indian children with intellectual and developmental disabilities [15], but it nevertheless represents a substantial burden. Similarly, the proportion with bad or very bad oral hygiene (25.0% overall; 31.3% in intellectual disability) lies within the wide confidence interval of the pooled estimate of 38% (95% CI 21–59%) for poor oral hygiene in that review [15]. The lower estimates in our sample may partly reflect the exclusion of children who had received dental treatment in the preceding year, the predominance of adolescents, and the use of a dichotomous visual criterion for caries rather than a full DMFT/deft assessment, which may miss early lesions. Caries prevalence did not differ significantly by age group or sex, consistent with the view that disability-related factors rather than demographic characteristics drive caries risk in this population [6,12]. The poorer oral hygiene of children with intellectual disability agrees with systematic reviews showing that children and adults with intellectual disability have poorer oral hygiene and more periodontal disease than their peers [16,19], and with Indian studies of institutionalised and special-school populations [8,20,21]. Misrabi et al. likewise found the highest caries prevalence (75%) among children with intellectual disability [13]. Impaired manual dexterity and motor coordination, limited understanding of the purpose of oral hygiene, dependence on caregivers for toothbrushing, and behavioural difficulties during oral care are the most plausible explanations [10,11]. These findings indicate that interventions for this group must extend beyond instruction of the child to include supervised or assisted toothbrushing and hands-on training of parents, teachers and caregivers. Children with hearing impairment had comparatively better oral hygiene; 40% had good or very good scores and none had very bad scores. Because their manual dexterity and cognition are usually unaffected, these children can generally brush independently once instructions are delivered effectively, for example through sign language and visual demonstration. Nonetheless, studies from Udaipur have documented considerable caries experience and unmet treatment needs among children with hearing impairment [22], so better plaque control should not be assumed to mean freedom from disease. Half of the children with visual impairment had good oral hygiene, and their mean score did not differ significantly from that of the other groups; however, with only six children, this subgroup does not permit firm conclusions. Previous Indian studies have reported fair to poor oral hygiene among visually impaired children and highlighted the value of tactile and audio-based instruction [9,23]. The low prevalence of gingival inflammation (4.6%) contrasts with the fact that one in four children had bad or very bad oral hygiene, and with the high prevalence of periodontal disease reported among children with intellectual disability [8,16]. This discrepancy most likely reflects under-detection, because gingival inflammation was recorded as a simple present/absent finding on visual inspection without a standardised index or assessment of bleeding on probing. Future studies should use a validated gingival index alongside a plaque index to capture the gingival consequences of poor plaque control. The findings have direct implications for school health and oral health programmes in the Union Territory. Special schools offer an efficient platform for daily supervised toothbrushing with fluoride toothpaste, periodic screening, topical fluoride and fissure-sealant application, and training of teachers and caregivers, with priority given to children with intellectual disability. Establishing referral linkages with dental services that are experienced in, and willing to manage, children with special needs would help to address the barriers to care described earlier [10]. Limitations This study has several limitations. First, its cross-sectional design permits estimation of prevalence but not inference of causality. Second, the sample was drawn from a single special school, which limits generalisability to children with disabilities who are not enrolled in school or who attend other institutions. Third, the visual impairment group comprised only six children, so estimates for this subgroup are imprecise. Fourth, the OHI-C was developed and validated for children aged 6–12 years with primary or mixed dentition [18], whereas our sample included children aged 5–15 years, most of them adolescents with permanent dentition; in addition, the index showed only moderate inter-examiner reproducibility in its validation study [18]. Fifth, dental caries and gingival inflammation were recorded dichotomously on visual examination rather than with standard indices such as the DMFT/deft and a gingival index, which probably underestimated disease, particularly gingival inflammation. Sixth, the exclusion of children who had received dental treatment in the previous year, who could not cooperate, or whose parents did not consent may have introduced selection bias. Finally, the severity of disability, socioeconomic status, oral hygiene practices and diet were not analysed, so the determinants of poor oral health could not be examined.

More than half of the children with disabilities attending a special school in Silvassa had dental caries, and one in four had bad or very bad oral hygiene. Children with intellectual disability had the poorest oral hygiene and constitute the highest-priority group for intervention. School-based preventive programmes that combine supervised toothbrushing, caregiver and teacher training, periodic dental screening and topical fluoride, tailored to each type of disability, are recommended. Larger multicentre studies using standardised caries and gingival indices are needed to identify the determinants of poor oral health in this population.

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