This is a secondary analysis of data generated to determine the association between oral habits, caries [18], and periodontal health [19]. The study was a household survey of children resident in Ife Central Local Government Area of Osun State, a suburban area in Nigeria. The data were collected in the months of August and September 2013.
The study methodology has been extensively described by Folayan et al. [20] and Kolawole et al. [18]. Children 6 months to 12 years of age whose parents consented to their participation in study were recruited. Child’s sex was defined as the biological sex; age was defined as the age at last birthday. For children less than a year old, the age was defined as the number of months after birth.
Sampling was done with a multi-stage technique (Fig. 1), that involved random selection of enumeration areas within the Local Government Area; selection of every third household on each street; identification of eligible individuals within households; and selection of respondents for interview and clinical examination. Only one child per household was selected for study participation. A structured questionnaire was used for collection of data about the child from the mothers. Where mothers were unavailable, fathers completed the questionnaires. The questionnaire collected details on the child’s socio-demographic characteristics (age, sex, and socio-economic status), oral habits, and caries prevention habits. All study participants had oral examination performed on the same day.
Malocclusion
Children were examined in their homes under natural light while sitting on a chair. The occlusal features of each child were assessed in the antero-posterior, transverse and vertical planes of space. The presence of individual malocclusion traits, i.e., crowding, spacing, increased overjet, reverse overjet, anterior open bite, increased overbite, buccal and lingual crossbite were documented. Malocclusion was assessed with the dental aesthetic index (DAI), described by Cons et al. [21] Scores for each of the 10 morphologic characteristics assessed by the DAI, i.e., number of missing visible teeth, crowding and spacing in the incisal segments, midline diastema, anterior irregularity in the maxillary and mandibular arches, anterior maxillary overjet and mandibular overjet, vertical anterior open bite and the antero-posterior molar relationships, were determined. The values obtained were multiplied with the appropriate weighting factor, summed, and added to a constant value of 13 to get the DAI score. The DAI scores were graded into four groups based on pre-defined DAI scores [21] 13–25, Grade 1 (normal or minor malocclusions, with slight or no treatment need); scores 26–30, Grade 2 (definite malocclusions, with treatment considered elective); scores 31–35, Grade 3 (severe malocclusions, with treatment highly desirable); and scores 36 and higher, Grade 4 (very severe or disabling malocclusions, with treatment considered mandatory).
Caries
The caries status was assessed with the decayed, missing, and filled teeth/decayed, missing, and filled teeth (dmft/DMFT) index [22]. Caries severity was evaluated with the pufa/PUFA index [23]. Caries status was further divided into caries present or absent.
Oral hygiene
Oral hygiene status of participants was evaluated with the simplified oral hygiene index (OHI-S) described by Greene and Vermillion [24]. The amount of debris or calculus present on the facial or lingual surfaces of six index teeth (A, E, F, K, O, and P) in the primary and 8, 3, 14, 19, 24, and 30 in the permanent dentition was used to determine the debris and calculus index scores, from which the OHI-S score was calculated. The oral hygiene was classified as good, fair, or poor when the scores were 0.0–1.2, 1.3–3.0, and > 3.0, respectively. Oral hygiene was further dichotomized into good oral hygiene and fair/poor oral hygiene.
Gingival health
The presence and severity of gingivitis was evaluated with the gingival index, as described by Löe and Silness [25]. Changes in the gingiva in relation to the appropriate six index teeth (D, G, N, Q, K and T) in the primary and 7, 3, 12, 19, 23 and 28 in the permanent dentition were assessed. Four areas of each index tooth were scored, and the scores were summed and divided by four to give the gingival index for each tooth. The gingival index of each participant was obtained by adding the values of all index teeth and dividing by six. Gingivitis was classified as mild, moderate, or severe, with values of 0.1—1, 1.1—2, and 2.1–3, respectively. Gingivitis was dichotomized into mild gingivitis and moderate-to-severe gingivitis [26].
Calibration of examiners
The five members of the research team responsible for data collection were calibrated before the study commenced to determine inter- and intra-examiner reproducibility. The mean κ coefficients obtained were 0.86 for caries, 0.92 for the OHI-S, 0.94 for gingival index, and 0.90 for malocclusion.
Data analysis
The mean DAI scores of study participants were calculated. The association between the malocclusion traits, caries presence, oral hygiene status and gingival health were assessed with chi-square tests. Independent sample t-test was used for comparisons of the mean DAI scores. Malocclusion traits associated with the presence of caries, poor oral hygiene, and poor gingival health were also determined, using logistic regression. For the logistic regression model, oral hygiene status was dichotomized to good and poor (fair and poor) oral hygiene, and the severity of gingivitis was dichotomized to gingivitis present (moderate and severe) and gingivitis absent (mild). The Hosmer-Lemershow goodness-of-fit test was conducted to confirm the consistency of fit of the regression models. Also, collinearity was determined with tolerance and the VIF test. Statistical significance was inferred at p < 0.05.
Ethical consideration
The Obafemi Awolowo University Teaching Hospital Complex Ile-Ife Ethics and Research Committee gave ethical approval for the study (ERC/2013/07/14). The Ife Central Local Government Authority also gave written approval to conduct the study. All the parents of study participants gave written informed consent for their children to participate; children aged eight to 12 years also provided written assent. Data collection was done without indicating the names of participants. Participants did not receive cash compensation for participating in the study.