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Oral Health and Occlusion in Tunisian Preschool Children

Published papers also revealed that occlusion in deciduous dentition are often closely related to that in permanent dentition. The careful examination of occlusal features in children, often gives an idea about the future occlusion in permanent dentition. The follow-up and the early management of slight malocclusion in children will therefore prevent the occurrence of malocclusion in permanent dentition [2]. Since the papers of Chapman (1935) [3] and later Baume (1950) [4], many epidemiological studies have been carried out to investigate the occlusal features in the deciduous dentition. It is generally agreed through these papers that the flush terminal plane relationship was accepted as the norm in the complete deciduous dentition [3,5-8]. However many authors did not support this view and concluded that the mesial step, rather than the flush terminal plane, was the most commonly observed terminal plane relationship [9,10]. Unfortunately, such studies were rare in Tunisia as in many of developing countries, so the aim of this investigation, conducted in Tunisian preschool children was to collect and analyse data about oral health status and the occlusal features in deciduous dentition.

approval and the authorizations by the educational and the health authorities; the parents were well informed, and had given their written agreement. During the survey, children with oral diseases were referred to our paediatric dentistry department for free management according to the directives of the Tunisian National Program of Oral Health.

Sampling
A bi-stage clustered sampling technique was used. In the first stage, of 42 kindergarten stratified by district, 11 were randomly selected. Secondly, 36 children were selected in each institution. The sample was chosen in respect of the following inclusion criteria: • No dental anomalies of number (agenesis or supernumerary teeth) • No malocclusion (teeth version) because of premature loss of deciduous teeth.

Methods
A session for oral hygiene education was performed in a first contact with children. During the next meeting, a clinical examination was carried out, according to the World Health Organization (WHO) criteria [11], to detect oral affections. Children were examined in a classroom, under daylight, with the usual dental examining instruments (dental mirror, explorer and tongue depressor); no radiographs were taken. The same investigator performed all examinations in order to avoid "inter-examiner reliability" bias. Data were recorded in a modified WHO oral health assessment form [11].
The family income was assessed from the profession of the parents. Besides the frequency of daily toothbrushing, the oral hygiene was evaluated by the simplified Oral Hygiene Index (OHI-S) described by Greene and Vermillion (1964) [12]. The scores were classified into three levels: [0-1] Good oral hygiene; [1][2] fair; [2][3] Poor.
The caries experience was also assessed according to WHO criteria. The decayed (d), missing (m) and filled (f) teeth index (dmft) was determined with the significant caries index (SiC). According to Bratthall [13], the SiC index was calculated by "considering the mean dmft values of the one-third of the individuals with the highest caries score".
In addition, the occlusion characteristics in deciduous dentition were recorded; notably physiologic spacing teeth and terminal molar plane, which describes the relationship, in vertical plane of the maxillary and mandibular second primary molar. As previously defined by Baume, in the flush terminal plane, "the distal surfaces of upper and lower primary second molars lie in the same vertical plane". While in the mesial step plane, "the distal surface of the lower primary second molar is mesial to that of the upper primary second molar" and in the distal step plane, "the distal surface of the lower primary second molar is distal to that of the upper primary second molar" [4]. As regards malocclusion assessment, the Dental Aesthetic Index (DAI) introduced by WHO in 1997 [11] seemed not indicated to be used in primary dentition. The occlusal index (WHO 1987) [14] was more adapted. Its three categories are defined as follow: (Normal) "absence of occlusal alterations"; (Slight malocclusion) "when one or more teeth presented disturbance of position like rotation; or slight crowding; or spacing harming regular alignment"; (Moderate to severe malocclusion) "when there was an unacceptable effect on facial appearance; or a significant reduction in masticatory function or phonetic problems."

Processing Data
The Statistical Package for the Social Sciences SPSS® Software, version 20.0, was used for data processing and statistical analysis. The Pearson chi-squared test was calculated to compare the different percentages and type I error risk was set at 5% level of significance. Table 1, the sample included 392 children; 197 females (50.3%) and 195 males (49.7%). The gender ratio was 1.005 and the mean age of participants was 4.36 ± 0.7 years. The majority of them had a middle family's income (55.5%).

As shown in
With respect to the teeth brushing and the oral hygiene, we noted that of the children involved in the survey, 316 had a toothbrush (80%), but only 265 (67.6%) used it twice a day in average (1.93 ± 2.49 times a day). These rates seemed overestimated, because only 27.3% of children had a good oral hygiene A significant statistical relation was observed between rate of toothbrush possession with family income; in fact, this rate was lower in children from lower income family (χ2=12.53, p<0.001). No significant relation was observed between rate of toothbrush possession with age or with gender (p>0.05). In addition, there was not difference of oral hygiene according to age nor according to gender ( Table 2).
The findings related to the caries experience showed that 140 children (35.7%) were affected. This prevalence varied with oral hygiene, 50% of affected children had a poor oral hygiene (χ2=17.06, p<0.01).
In the present study, the mean dmft scores were 426 decayed teeth (mean 1.10 ± 1.0), five missed (mean 0.01 ± 0.8) and nine filled (mean 0.01 ± 0.05) giving overall 440 affected teeth and mean dmft of 1.12 ± 1.97. The significant caries index value (SiC) was about 5.57 ± 2.26 and concerned 45 children (12.8%) with dmft >3. No significant difference was found by age, gender and family income between children above and below 3 dmft (Table 2).
Besides, the findings also showed that 326 children (83.1%) had a deciduous dentition. This percentage was lower in girls than in boys (χ2=6.9, p<0.01) with 89.5% and 93.6% respectively ( Figure 1) and decreased logically with age (χ2=62.13, p<0.000) (Figure 2 had distal step ( Figure 2). Asymmetrical (right/left) molar relationship was noted in 12% of cases. No significant difference was noted in these occlusal patterns by age and gender.
The prevalence of malocclusion was about 24.7%, with only 13.3% children presenting moderate to severe malocclusion and needing orthodontic follow up. The analysis revealed that malocclusion was less frequent in children with spaced teeth (χ2=39.04, p<0.000) and in children presenting flush molar relationship (χ 2 =21.6, p<0.001) but malocclusion was more frequent in children with dental caries (χ 2 =13.16, p<0.01).

Discussion
Several limitations of this study must be taken into consideration; the major one was the subjectivity of some information given by    the children or their educators like daily tooth brushing frequency. Another limitation was due to some difficulties in observing occlusion characteristics in the conditions of this survey.
As regards caries experience, whereas our prevalence (35.7%) was similar to that reported by Maatouk et al. [6] (36 %), it was lower than those revealed by Abid [15] (56 %) in the last Tunisian national survey which investigated 670 six-year-old schoolchildren and by Henkuzena et al. [1] whose study conducted in Latvia to 638 children 2-6-yearold reported that 48% of them were affected. The dmft index, which increased with age, revealed a very high "d" component while its "f" component, a conservative care indicator, was very low revealing a very important need for restorative treatment in preschoolers that may suggest a lack of motivation among practitioners and parents towards appropriate care for primary dentition, high costs and difficult access to health care.
Many studies pointed out that besides the comparison with literature data, SiC index is a reliable tool used to assess the caries risk and to identify the group of at risk children who showed caries level significantly higher than a general population [16][17][18]. In our sample the SiC index value (5.57) was almost equivalent to that revealed by Städtler in 516 Austrian children 6-year-olds [17] (6.1); while it was higher (8.1) in a study carried out by Adewakun in Eastern Trinidad for 6-year-olds children [18]. The figure is also worse, as reported by Namal et al. [18], in 542 Turkish children, five-six years old (7.75); however, it was better in Australia for 6 years old children with SiC index about 4.7 [19,20].
Even, if these comparisons are not statistically valid because of disparities of the studied samples, our findings highlighted that a community-based strategies should be adapted where the oral health goal is to increase the proportion of caries free 6 year-olds. We should therefore use SiC index to target at-risk groups for the introduction of reinforced prevention actions. Besides, this index permits an appropriate use of resources by indicating the prevention measures for children who really need them [20]. In our sample, Health promotion programs to stimulate tooth brushing and healthy dietary habits are strongly needed especially in Children at high risk.
It is interesting to note, on another hand, that more girls than boys were in mixed dentition, which revealed that dental eruption was earlier in girls as generally shown in literature; Shaweesh had previously reported in a study, which involved 2672 Jordanian children 4-16 years old that even in permanent dentition, teeth emerge sooner in girls [21,22].
The published studies, about occlusal patterns in the deciduous dentition, reported large differences in their results. According to Farsi, these observed variations may depend on ethnicity, hereditary variations or a different methodology and sample composition so the comparisons between them are not reliable.
Concerning spaced teeth, the present study confirmed that this phenomenon is common with a percentage of 68.7% while the study of Mahmoodian conducted in 248 Iranian children aged from 4 to 5 years revealed a clearly upper frequency of these physiologic spaces with 90%. No significant difference was found according to gender [23]. The absence of these spaces can be an expression of future discrepancies between jaw and tooth size in permanent dentition [9,24].
Moreover, many studies reported that the deciduous molar relationship could be the best indication for the future permanent molar occlusion [2,3,9,10]. They showed that the flush terminal plane relationship progressed in the permanent dentition to a Class I molar relationship in 56% of cases and to Class II in 44%. Distal step molar relationship leads often to Class II molar relationship in permanent dentition while mesial step progressed in a greater probability for a Class I molar relationship and a lesser probability for a Class II molar relationship [2,5]. In our study, the flush terminal plane was the most frequent molar relationship with a very high percentage (81%); these findings are very close to those reported by Baume in 1905 and by Farsi among 520 Saudi Arabian's children 3-5-year-old [22]. Farsi's study revealed that 80 % of these children presented a flush molar relationship, 12 % had a mesial step and 8 % a distal step. In the same way, Bhayya et al., [5] revealed that of 1000 Indian children 4-6-yearold, 52.5% had a flush terminal plane, whereas 36% had a mesial step and 8.4% showed a distal step. Finally, Maatouk et al., [6], Keski-Nisula et al., [7] and Sukhia et al., [8] also reported the ascendancy of the flush molar relationship with 50.2%, 47.8% and 63.2%, respectively (Table 3).
However, these findings contrasted with those reported in Abu Alhaija study which was conducted in 1048 Jordanian children (2.5 to 6 years old): this study revealed that the mesial step molar relationship was a predominant type of molar relationship (48%) followed by the flush relationship (37%) and finally the distal step (4%) [9]. These results were consolidated by those reported by Anderson in 189 African American children where 89% of them exhibited a mesial step terminal plane [10]. In another study carried out by Hedge in Udaipur (India) on 200 children 3-5-year-old, findings revealed almost equal rates between the flush terminal plan (49%) and the mesial step (50%) [25] (Table 3).
The prevalence of malocclusion in our sample (24.7%) was lower than those revealed by Abid in the last Tunisian national survey [15] and in Maatouk's study [6] with 37% and 31%, respectively. Carvalho [25]   children aged from five to six years, whereas Keski-Nisula reported a higher frequency (68%) in 953 Finnish children 4.0 to 7.8 years old [7].
As Frazao et al. [26] previously reported in 2004, our study suggested that severity of malocclusion was significantly associated with dental caries but not with gender or ethnic group. In fact, malocclusion has long been accepted as a risk factor for dental caries because of increased food and plaque accumulation in areas of crowding. It is evident, on another hand that a precocious tooth extraction due to dental caries can lead to a space loss and malocclusion. However, Hafez et al., concluded in their systematic review study that there are no high-quality studies to resolve the possible association between dental crowding and caries [27,28].
Our study also revealed relatively low needs for orthodontic follow up (13.3%); some authors reported that the crowding in deciduous or mixed dentition is often passing and settles spontaneously during the implementation of the permanent dentition if the leeway space is well used. In the mixed dentition, early interceptive treatment of some slight malocclusions can be successful, what reduces significantly the need for orthodontic treatment in the permanent dentition according to King.

Conclusion
The present paper gave an outline onto the oral health status, the occlusal patterns and malocclusion in the deciduous dentition in Tunisian children. Findings revealed a poor oral hygiene and a high dental caries experience with a high needs for restorative treatment. The spaced dentition was more frequent than closed dentition and flush plane was the most frequent type of terminal molar relationship in deciduous dentition.

Conflict Interests
None declared