Faculty of Graduate Studies, Khon Kaen University; 2 Sirindhorn College of Public Health Khon Kaen; 3

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1 Journal of Disability and Oral Health (2011) 12/ Evaluation of noncavitated and cavitated carious lesions using the International Caries Detection Assessment System (ICDAS II) and oral hygiene in Thai students with disabilities Supatra Oranbundid BDH MPH 1,2, Nusara Poomat DDS 3, Somkiat Luengpailin DDS PhD 4, Araya Pisek DDS 3, Anwar T Merchant DMD ScD 5 and Waranuch Pitiphat DDS MPHM MS ScD 3 1 Faculty of Graduate Studies, Khon Kaen University; 2 Sirindhorn College of Public Health Khon Kaen; 3 Department of Community Dentistry, Faculty of Dentistry, Khon Kaen University; 4 Department of Oral Biology, Faculty of Dentistry, Khon Kaen University: Khon Kaen, Thailand. 5 Department of Epidemiology and Biostatistics, University of South Carolina, SC, USA Abstract Aim and objectives: Epidemiological data concerning oral health status of individuals with disabilities is sparse and most studies do not include the assessment of noncavitated lesions. This study aimed to evaluate noncavitated and cavitated carious lesions and oral hygiene status of students with disabilities in Khon Kaen, Thailand. Design: Participants included 285 students aged 6-15 years with visual impairment, hearing impairment or physical disability who attended special needs schools in Khon Kaen. Dental caries was examined using the International Caries Detection and Assessment System (ICDAS II). Oral hygiene was assessed using Silness and Löe plaque index (PI). Results: Almost all students had at least one noncavitated or cavitated lesion (97.1% in primary and 95.4% in permanent dentition). When considering only cavitated lesions, the prevalence was 90.6% in primary and 69.1% in permanent dentition. The overall mean (±standard deviation) dmft, dmfs, DMFT and DMFS scores were 6.3±4.6, 17.6±16.1, 9.7±6.1 and 16.0±11.0, respectively. The mean number of noncavitated surfaces (3.4±3.4) was lower than that of cavitated surfaces (11.8±13.5) in the primary dentition, but the opposite trend was observed in the permanent dentition: noncavitated (12.3±8.5) and cavitated (2.7±3.9) surfaces. Most carious lesions remained untreated in all groups. The overall PI score was 1.4±0.4 demonstrating a moderate level of oral hygiene. Conclusions: Students with disabilities experienced high levels of both noncavitated and cavitated lesions. Effective preventive measures are required to improve the oral health of this disadvantaged group. Key words: Disabled children, dental caries, oral hygiene, epidemiology Introduction Oral health problems continue to be common in persons with disabilities. Disabled schoolchildren and young adults had a higher percentage of dental caries and poorer oral hygiene as compared with their counterparts without disabilities (Shyama et al., 2000; U.S. Department of Health and Human Services, 2000; Mitsea et al., 2001; Shyama et al., 2001; Ministry of Public Health, 2002). Several causes for the higher level of oral diseases among disabled persons include limited physical ability, ineffective oral self-care, lack of cooperation (Griffiths, 2002) and limited access to oral care (U.S. Department of Health and Human Services, 2000). Dental caries and other oral diseases may result in pain, unhappiness and tooth loss among affected individuals, and a costly burden to health care services (World Health Organisation, 2007). It is thus essential to set up a surveillance system for early detection of oral diseases among disabled schoolchildren in order to provide appropriate information for oral health programme planning and intervention. Detection of early carious lesions is of paramount importance. Dental caries is a reversible, biological process in the early stages (Warren et al., 2002). If the disease is detected early enough at the noncavitated stage, it may be possible to enhance remineralisation or inhibit demineralisation by appropriate preventive measures (Featherstone, 2004).

2 100 Journal of Disability and Oral Health (2011) 12/3 However, the majority of caries detection methods were ambiguous and took into account only cavitated lesions (Ismail et al., 2007). The newly developed visual method for caries detection International Caries Detection and Assessment System (ICDAS II) (International Caries Detection and Assessment System Coordinating Committee, 2005) is therefore recommended to distinguish various stages of the carious process ranging from early clinically visible changes in enamel to extensive cavitations (International Caries Detection and Assessment System Coordinating Committee, 2005). The ICDAS criteria have also been reported to have good validity and high reliability for caries detection (Ismail et al., 1992; Ismail et al., 2007). Epidemiological data concerning the oral health status of individuals with disabilities in developing countries are sparse, with only a few studies being conducted in Thailand (Ministry of Public Health, 1993; Ministry of Public Health, 2002). Although noncavitated lesions occur in most populations (Ismail et al., 1992; Warren et al., 2002) most studies among disabled populations have not included the assessment of these. Hence, the aims of the study were: to determine the different stages of dental caries status using the ICDAS II, and to assess the level of oral hygiene in students with disabilities. Materials and method Study population This cross-sectional survey was conducted between June and August 2008 in three special needs schools in Khon Kaen, northeast Thailand: School for the Blind, School for the Deaf and Srisangwan School for the Physically Disabled. The study population consisted of all 285 students aged 6-15 years in these schools, including 157 (55.1%) hearing impaired, 44 (15.4%) visually impaired and 84 (29.5%) physically impaired (cerebral palsy, hydrocephalus, spina bifida, amputations or limb absences, muscular dystrophy, arthrogryposis multiplex congenita, paraplegia, and hemiplagia) (Table 1). Most students came from low income families across several provinces in northeast Thailand and were resident at the schools. The average age of the students was 11.1± 2.6 years, half of whom (49.8%) were males. The majority (76.1%) of them were studying in the primary school level or lower (Table 1). When the study was conducted, there was no oral health care programme in any of these schools. Students brushed their teeth twice daily (before having breakfast and before going to bed) without close monitoring. After lunch, tooth brushing was performed in few preschool classes, whereas flossing had never been used. The study was conducted in accordance with the principles of the Declaration of Helsinki. Parents or guardians of the subjects gave written informed consent before the examination. No students refused oral examination, although they had the right to do so. Approval for the study was granted by the Khon Kaen University Ethics Committee for Human Research. Table 1 Demographic characteristics of the study population by type of disabilities (n=157) (n=44) (n=84) (n=285) Age (yrs) Mean±Standard deviation 11.1± ± ± ±2.6 Range Age groups (yrs), n (%) (54.1) 38 (86.4) 29 (34.5) 152 (53.3) (45.9) 6 (13.6) 55 (65.5) 133 (46.7) Male, n (%) 73 (46.5) 26 (59.1) 43 (51.2) 142 (49.8) Education level, n (%) Primary or lower 111 (70.7) 44 (100) 62 (73.8) 217 (76.1) Secondary 46 (29.3) - 22 (26.2) 68 (23.9)

3 Oranbundid et al.: ICDAS II and oral hygiene in Thai students with disabilities 101 Data collection Oral health surveys were conducted at school under artificial light. Students were examined on a mobile dental chair in a supine position, unless they were confined to a wheelchair. Assessment of oral hygiene status A dentist assessed oral hygiene status of the subjects using Silness and Löe plaque index (PI) (Silness and Löe, 1964). The index includes 4 codes: code 0 = no plaque, code 1 = a film of plaque adhering to the free gingival margin and adjacent area of the tooth, code 2 = moderate accumulation of soft deposits within the gingival pocket or the tooth gingival margin, and code 3 = abundance of soft matter within the gingival pocket and/or on the tooth and gingival margin. Disclosing agent was applied on tooth surfaces to improve visualisation. The measurements were performed on six Ramfjord teeth, including teeth numbers 16, 21, 24, 36, 41, 44 on both buccal and lingual surfaces of the teeth. Assessment of dental caries Dental caries examinations were carried out by another dentist who was trained in a workshop on the ICDAS II. Additional calibration and standardisation were also performed before the actual examination. Assessment was done using a mouth mirror and a WHO periodontal probe. Before examination for dental caries the teeth were professionally cleaned thoroughly to remove plaque and the disclosing agent. Also, the teeth were dried during the examination by using compressed air, saliva ejector and mobile suction. Dental caries was recorded following the ICDAS II criteria (International Caries Detection and Assessment System Coordinating Committee, 2005). The ICDAS system includes 7 codes: code 0 = sound, code 1 = first visual change in enamel, code 2 = distinct visual change in enamel, code 3 = localised enamel breakdown without clinical visual sign of dentine involvement, code 4 = noncavitated surface with underlying dark shadow from dentine, code 5 = distinct cavity with visible dentine, and code 6 = extensive distinct cavity with visible dentine cavity. Codes 1 and 2 were grouped into noncavitated carious lesions, and codes 3 to 6 into cavitated carious lesions. The same criteria were applied for both permanent and primary teeth. During examination, approximately 5% of subjects were re-examined to test for consistency. Intra-examiner reliability was high with a kappa value of 0.8. Statistical analysis We used descriptive statistics to express general characteristics and oral health status of the subjects. Dental caries experience was described as decayed, missing and filled teeth (dmft) and surfaces (dmfs) scores for primary teeth, and DMFT/DMFS scores for permanent teeth. The dmft/dmfs scores were calculated for children under 12 years of age and DMFT/DMFS for those greater than 6 years of age. Prevalence of dental caries was calculated according to the ICDAS II criteria (code 1 to code 6: including both noncavitated and cavitated lesions) as well as the traditional method (code 3 to code 6, counting only cavitated lesions). Results Dental caries status Dental caries affected the majority of the participants in the study and affected virtually all students with visual impairment. Overall, the prevalence of dental caries in the primary dentition was 97.1% when including both noncavitated and cavitated lesions, and decreased to 90.6% when considering only cavitated lesions. For the permanent dentition, 95.4% of the participants had at least one noncavitated or cavitated lesion, and 69.1% had at least one cavitated lesion. The visually impaired group had the highest prevalence of dental caries when including both cavitated and noncavitated lesions (100%), but the lowest prevalence (53.5%) of cavitated carious lesions. Compared with cavitated lesions, noncavitated lesions occurred less frequently in the primary dentition but more frequently in the permanent dentition (Table 2). When focusing only among the WHO global monitoring age group of 12 years, the prevalence of dental caries in permanent dentition was 100% when including both noncavitated and cavitated lesions, and 74.3% when considering only cavitated lesions. Table 3 compares the caries experience in the primary dentition among different groups of students with disabilities. The mean numbers of primary teeth and tooth surfaces with noncavitated lesions (code 1 to code 2: d 1-2 t) were similar between the hearing impaired (d 1-2 t = 0.9, d 1-2 s = 2.6) and the physically impaired (d 1-2 t = 0.8, d 1-2 s = 2.4), which were much lower than those in the visual impaired group (d 1-2 t = 1.8, d 1-2 s = 6.1). However, the mean number of cavitated tooth surfaces (d 3-6 s = 14.5) was highest in students with physical disability. When considering noncavitated and cavitated lesions together, students with visual impairment had the highest mean score for both d 1-6 mft (7.9) and d 1-6 mfs (21.9), whereas these scores were lowest in the hearing impaired group (d 1-6 mft = 5.6 and d 1-6 mfs = 15.7). The same trend was found when considering only the cavitated lesions. The visually impaired had the highest mean scores of d 3- mft (6.2) and d mfs (15.8), while the hearing impaired subjects had the lowest mean scores of d 3-6 mft (4.8) and d 3-6 mfs (13.1). Approximately 94.6% and 95.0% of carious lesions were untreated in primary and permanent dentition, respectively. Data regarding the permanent dentition are presented in Table 4. The mean numbers of teeth and tooth surfaces were highest in physically disabled students which constituted the oldest study group, and lowest in visu ally impaired

4 102 Journal of Disability and Oral Health (2011) 12/3 students which were the youngest. The mean number of carious teeth was, however, highest in students with hearing impairment when combining both noncavitated and cavitated teeth, while it was highest in the physically disabled group when considering only cavitated teeth. Similar results were observed when examining the tooth surfaces. The mean number of noncavitated surfaces (12.3±8.6) was higher than that of cavitated lesions (2.7±3.9) in the permanent teeth, but the opposite result was found in the primary teeth: noncavitated lesions (3.4±3.4) and cavitated lesions (11.8±13.5) (Table 3). With regards to caries experience in the permanent dentition, the overall mean score was 9.7 for D 1-6 MFT and 16.0 for D 1-6 MFS. The scores were decreased markedly when considering only the cavitated lesions (D 3-6 MFT = 1.9, D 3-6 MFS = 3.7). The hearing impaired group had the highest DMF scores (D 1-6 MFT = 10.6, D 1-6 MFS = 17.5) when combining both noncavitated and cavitated lesions, while the physically disabled group had the lowest scores (D 1-6 MFT = 8.0, D 1-6 MFS = 13.1). In contrast, the mean scores were highest among the physically disabled group when considering only the cavitated lesions (D 3-6 MFT = 2.3, D 3-6 MFS = 4.3). The decayed component accounted for the major part of the DMFT and DMFS scores in all groups. Oral hygiene status Table 5 shows the oral hygiene status of the students by type of disabilities. The mean PI score of all subjects was 1.40±0.4, with the highest score being among physically disabled children aged 6-11 years (1.7±0.4). Among those with hearing impairment and physical disability, females had a slightly better oral hygiene status than their male counterparts, and oral hygiene appeared to improve with increasing age. In contrast, oral hygiene status was similar across all age groups and gender among students with visual impairment. Table 2 Prevalence of dental caries in primary and permanent dentitions by type of disabilities Primary dentition Including both noncavitated and cavitated lesions *, n/n (%) 78/81 (96.3) 33/33 (100) 24/25 (96.0) 135/139 (97.1) Noncavitated lesion only, n/n (%) 51/81 (63.0) 28/33 (84.8) 11/25(44.0) 90/139 (64.7) Cavitated or dentinal lesions only, n/n (%) 72/81 (88.9) 31/33 (93.9) 23/25 (92.0) 126/139 (90.6) Permanent dentition Including both noncavitated and cavitated lesions *, n/n (%) 150/156 (96.2) 43/43 (100) 76/83(91.6) 269/282 (95.4) Noncavitated lesion only, n/n (%) 150/156 (96.2) 43/43 (100) 75/83 (90.4) 268/282 (95.0) Cavitated or dentinal lesions only,n/n (%) 109/156 (69.9) 23/43 (53.5) 63/83 (75.9) 195/282 (69.1) * ICDAS code 1 to code 6 ICDAS code 1 to code 2 ICDAS code 3 to code 6

5 Oranbundid et al.: ICDAS II and oral hygiene in Thai students with disabilities 103 Table 3 Mean±standard deviation of number of teeth/tooth surfaces, noncavitated, cavitated teeth/tooth surfaces, and dental caries experience in primary dentition by type of disabilities Number of teeth 8.8± ± ± ±5.7 Noncavitated teeth (d 1-2 t) * 0.9± ± ± ±1.5 Cavitated teeth (d3-6 t) 4.2± ± ± ±4.2 All carious teeth ( d 1-6 t) 5.1± ± ± ±4.3 Missing teeth due to caries (mt) 0.3± ± ± ±0.7 Filled teeth (ft) 0.2± ± ± ±0.6 Decayed, missing and filled teeth (d 1-6 mft) 5.6± ± ± ±4.6 Decayed, missing and filled teeth (d 3-6 mft) 4.8± ± ± ±4.5 Number of tooth surfaces 39.8± ± ± ±25.4 Noncavitated surfaces (d 1-2 s) 2.6± ± ± ±3.4 Cavitated surfaces (d 3-6 s) ** 10.6± ± ± ±13.5 All carious surfaces ( d 1-6 s) 13.3± ± ± ±14.7 Missing surfaces due to caries (ms) 1.5± ± ± ±3.5 Filled surfaces (fs) 0.9± ± ± ±3.1 Decayed, missing and filled surfaces (d 1-6 mfs) 15.7± ± ± ±16.1 Decayed, missing and filled surfaces (d 3-6 mfs) 13.1± ± ± ±14.9 * Noncavitated teeth (code 1 to code 2: d 1-2 t) Cavitated teeth (code 3 to code 6: d 3-6 t) All carious teeth (code 1 to code 6: d 1-6 t) Noncavitated lesions on tooth surfaces (code 1 to code 2: d 1-2 s) ** Cavitated lesions on tooth surfaces (code 3 to code 6: d 3-6 s) All carious tooth surfaces (code 1 to Code 6: d 1-6 s

6 104 Journal of Disability and Oral Health (2011) 12/3 Table 4 Mean±standard of number of teeth/tooth surfaces, noncavitated, cavitated teeth/tooth surfaces, and dental caries experience in permanent dentition by type of disabilities Number of teeth 20.0± ± ± ±7.7 Noncavitated teeth (D 1-2 T) * 8.9± ± ± ±5.3 Cavitated teeth (D 3-6 T) 1.6± ± ± ±1.8 All carious teeth (D 1-6 T) 10.5± ± ± ±6.0 Missing teeth due to caries (MT) 0.1± ± ± ±0.4 Filled teeth (FT) 0.1± ± ± ±0.5 Decayed, missing and filled teeth (D 1-6 MFT) 10.6± ± ± ±6.1 Decayed, missing and filled teeth (D 3-6 MFT) 1.7± ± ± ±1.9 Number of tooth surfaces 90.2± ± ± ±35.6 Noncavitated surfaces (D 1-2 S) 14.0± ± ± ±8.6 Cavitated surfaces (D 3-6 S) ** 2.5± ± ± ±3.9 All carious surfaces (D 1-6 S) 16.5± ± ± ±10.6 Missing surfaces due to caries (MS) 0.5± ± ± ±1.8 Filled surfaces (FS) 0.5± ± ± ±1.3 Decayed, missing and filled surfaces (D 1-6 MFS) 17.5± ± ± ±11.0 Decayed, missing and filled surfaces (D 3-6 MFS) 3.5± ± ± ±4.5 * Noncavitated teeth (code 1 to code 2: D 1-2 T) Cavitated teeth (code 3 to code 6: D 3-6 T) All carious teeth (code 1 to code 6: D 1-6 T) Noncavitated lesions on tooth surfaces (code 1 to code 2: D 1-2 S) ** Cavitated lesions on tooth surfaces (code 3 to code 6: D 3-6 S) All carious tooth surfaces (code 1 to code 6: D 1-6 S) Table 5 Mean±standard deviation of plaque index score by type of disabilities (n=157) (n=44) (n=86) (n=285) Gender Male 1.5± ± ± ±0.4 Female 1.3± ± ± ±0.4 Age group (yrs) ± ± ± ± ± ± ± ±0.4 Total 1.4± ± ± ±0.4

7 Oranbundid et al.: ICDAS II and oral hygiene in Thai students with disabilities 105 Discussion This is the first study to assess dental caries status by using ICDAS II criteria among children with disabilities. Previous studies used the traditional method that included only cavitated lesions for caries evaluation (Mitsea et al., 2001; Shyama et al., 2001; Ministry of Public Health, 2002). The older methods underestimated dental caries and neglected the enamel carious lesions (Pitts and Fyffe 1988; Ismail et al., 2007). For example among children with visual impairment in this study, caries prevalence using ICDAS II criteria was 100% compared to 53.5% using older criteria. Therefore, we display both criteria in order to compare our results with those studies. Our findings confirm previous studies that reported high prevalence of cavitated carious lesions in schoolchildren with disabilities (Mitsea et al., 2001; Shyama et al., 2001). However, prevalence of cavitated lesions in the primary dentition observed in our study (90.6%) was approximately three times higher than that reported in two previous studies in Thailand (approximately 28.0% in both studies) (Ministry of Public Health, 1993; Ministry of Public Health, 2002), and earlier studies in the Northern Region of the United Kingdom (31%) (Nunn et al., 1993) and in Greece (39%) (Mitsea et al., 2001) This may suggest an increasing trend of dental caries among children with disabilities. Noncavitated lesions were more prevalent than cavitated lesions in permanent teeth (95.4% vs 69.1%), consistent with that reported in earlier studies (Ismail et al., 1992; Ismail et al., 2008). Additionally, the mean number of noncavitated surfaces (12.3) was higher than that of cavitated surfaces (2.7) in the permanent dentition, but the opposite result was observed in the primary dentition: noncavitated (3.4) and cavitated (11.8). Similarly, the prevalence of cavitated lesions was higher than noncavitated lesions in primary teeth (90.6% vs 64.7%). These results are to be expected in the mixed dentition stage as caries lesions in primary teeth are present in the oral cavity longer than those in permanent teeth and have more time to develop or progress. This notion is supported by a longitudinal study of 2.5 to 3.5-year-old children among whom 64% of noncavitated lesions progressed to cavitated or filled lesions within a one year period of observation (Grindefjord et al., 1995). Additionally, two longitudinal studies with long duration of follow-up demonstrated that noncavitated lesions usually progressed to cavitated lesions in primary teeth. In the first study 31% of noncavitated pit and fissure in primary dentition progressed to frank cavity or filled condition in four years (Warren et al., 2006). While in the latter study, using radiographic data, 60% of proximal noncavitated lesions progressed to cavitated lesions in 6-8 years (Vanderas et al., 2003 ). This may lead to more cavitated than early lesions in primary teeth. Individuals with physical disability suffered from higher prevalence and caries experience of cavitated lesions. They also tended to have more severe caries than other groups. This investigation was in accordance with the previous study (Shyama et al., 2001). The cause may be the students decreased ability for oral self-care (Griffiths, 2002), such as difficulty in tooth brushing. This may also be due to the fact that in our study, students with physical disabilities were somewhat older than the other groups. Furthermore, our findings have confirmed the highest PI score in physically disabled children. The previous study showed that poor oral hygiene was the main risk indicators to predict present caries (Mascarenhas, 1998). Other reasons for high caries could be that children with physical disabilities had less access to oral health care and there are no special programmes targeted to this group (Griffiths, 2002). Nevertheless, motivation and encouragement provided by schoolteachers, caregivers, and guardians were the most important factors to increase good oral hygiene in the disabled children. This study shows that the decay component was the major constituent of both dmft and DMFT indices in all groups. That is, these students had received insufficient dental care perhaps because of limited access to oral care (U.S. Department of Health and Human Services, 2000) and the complexity of provided treatment (Griffiths, 2002). Similar to most epidemiologic studies, we did not use dental radiographs and thus dental caries prevalence might still be underestimated. Another limitation was that no children without disability were examined as a control group. When we indirectly compared our results with the 6th National Oral Health Survey of Thailand conducted in (Ministry of Public Health, 2008) using the WHO s traditional criteria (World Health Organisation, 1997), children aged 12 years in our study had caries prevalence of 74.3% compared to 56.9% in healthy children of the same age. One of the reasons for a higher level of dental caries among children with disabilities may be that the surveillance dental health programme that operated in general elementary schools did not cover the schools for the disabled. Although the school-based oral health programmes for disabled students were launched in (Ministry of Public Health, 2002), they were subsequently discontinued. Consequently, disabled students lack oral health care and this may further increase their oral health problems. Our result shows an overall moderate level of oral hygiene and seemingly poor oral hygiene in younger children with physical disability, while the students with visual impairment and hearing impairment have slightly better oral hygiene status than the other group. This is in agreement with early findings in children attending special schools that students with physical impairment have difficulty using a toothbrush or cleaning their teeth, whereas students with visual impairment are capable of understanding oral health instruction better than other groups and also have better motor control (Mitsea et al.,

8 106 Journal of Disability and Oral Health (2011) 12/3 2001). However, individuals with severe disabilities were able to learn oral hygiene and perform tooth brushing for themselves, provided that they are encouraged and motivated (Shaw, et al. 1983). Conclusion This population of children with disabilities experienced high levels of both noncavitated and cavitated carious lesions. Most of the caries remained untreated among students with disabilities. The high prevalence of noncavitated lesions observed in this study suggests the need for preventive measures to enhance enamel remineralisation. Effective school-based oral health services are required to improve the oral health of this disadvantaged group. Acknowledgements This study was supported by Khon Kaen University Graduate School and the Khon Kaen Provincial Administrative Organisation. Our thanks to staff of the Department of Community Dentistry, Faculty of Dentistry, Khon Kaen University and Sirindhorn College of Public Health Khon Kaen, for their support in various ways. We are grateful to all students, teachers, and school administrators who participated in this study References Featherstone JDB. The continuum of dental caries-evidence for a dynamic disease process. J Dent Res 2004; 83 (suppl 1): C39-C42. Griffiths JE. Guidelines for oral health care for people with a physical disability. J Disabil Oral Health 2002; 3: Grindefjord M, Dahllof GTM. Caries development in children from 2.5 to 3.5 years of age: a longitudinal study. Caries Res 1995; 29: International Caries Detection and Assessment System Coordinating Committee. Rationale and evidence for the International Caries Detection and Assessment System (ICDAS II). School of Dentistry, University of Michigan; p. 12. Ismail AI, Brodeu J-M, Gagnon P, Payette M, Picard D, Hamalian T et al. 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J Public Health Dent 2002; 62: Warren JJ, Levey SM, Broffitt B, Kanellis MJ. Longitudinal study of non-cavitated carious lesion progression in the primary dentition. J Public Health Dent 2006; 66: World Health Organisation. Oral health surveys basic methods 4th edition. Geneva, World Health Organisation. What is the burden of oral disease? Web site: html Accessed Oct 1, Address for correspondence: Dr. Waranuch Pitiphat Department of Community Dentistry Faculty of Dentistry, Khon Kaen University Khon Kaen Thailand waranuch@kku.ac.th