Influence of Occlusal Disorders, Food Intake and Oral Hygiene Habits on Dental Caries in Adolescents: A Cross-Sectional Study

1Multidisciplinary Department of Medical-Surgical and Dental Specialties, Second University of Naples, Naples, Italy 2Department of Chemistry, University of Sassari, Sassari, Italy 3Department of Health Sciences, University of Milan, Milan, Italy 4Department of Pediatric Dentistry, Dental School, University of Brescia, Brescia, Italy 5Department of Surgery, Microsurgery and Medical Sciences, Dental School, University of Sassari, Sassari, Italy


Introduction
Dental caries is a very common oral disease affecting children and adolescents throughout the world, though data from developed countries suggest a decline of dental caries in the last 30 years [1][2][3][4][5] (Table 1).
The complex multifactorial etiology of caries involves the host's characteristics (saliva and tooth enamel), the oral microflora (bacterial plaque), and the substrate (oral hygiene and diet) [3]. Occlusal disorders, like dental crowding and crossbite, may be a risk factor for dental caries. Crowding unsettles normal interproximal tooth contacts with improper embrasures leading to food accumulation and plaque retention [6]. In Italy, relatively few researches have been performed on caries prevalence to date [7][8][9][10], sometimes focusing in restricted geographic areas. Even more, poor information is available in literature [11][12][13][14]. Thus, more information is needed specially to support some useful prevention programs.
The aim of the present epidemiologic study was to calculate the DMFT (Decayed, Missed, Filled Teeth) index and to investigate the association among carious lesions and malocclusions, cariogenic food intake and oral care habits in 12-year-old school children in Southern Italy.
Therefore, the final sample to analyze comprised of 536 orthodontically untreated subjects.
The students were examined in a quiet classroom of their school without external interference, under natural or artificial illumination, approximately for 15 minutes. The dental occlusion assessment was carried out using latex gloves, sterile dental mouth mirrors and millimeter rulers. Personal data and information about orthodontic treatment were obtained directly from each student. No radiographs, study casts, or previous written records were used. The two examiners (Prof. Perillo and Dr. Giugliano) had previously undergone calibration to standardize their procedures before carried out clinical examination. The examination was focused on oral hygiene, occlusal variables and the evaluation of decayed (D), missing (M) and filled (F) teeth (T), or DMFT index [16]. Missing teeth were considered only if they were missing for caries [17,18].
The orthodontic variables considered were molar relationship, overjet and overbite, posterior crossbite, scissor bite, crowding and diastema. In particular, the molar relationship was determined like the relationship between the upper and lower first permanent molars according to the Angle's classification; patients with subdivision malocclusions were included in the Class II or Class III groups on the basis of the predominant occlusal characteristic, or of the relationship between the canines. Overjet and overbite with values between 0 and 4 mm were considered normal. A posterior crossbite, unilateral (right or left) or bilateral, was diagnosed when a crossover of at least one tooth was detected in the posterior segments of the dental arches. A scissor bite was considered when the palatal cusps of the upper molars were positioned buccally in relation to the buccal cusps of the lower molars. Crowding and diastema were recorded for the anterior or the posterior segments. A midline diastema was considered to be present when there was a space of at least 2 mm between the maxillary central incisors.

Questionnaire
Information about oral hygiene and dietary habits was obtained with a questionnaire on daily oral hygiene practices, intake and frequency of different types of foods (i.e., carbohydrates, dairy products, sweets). The frequency of dental check-ups was also investigated.
Regarding parents' scholarly level, a distinction was made between low educational level (no education or compulsory schooling) and high/medium educational level (apprenticeship training, vocational school, high school or higher education) [5,17,19].

Statistical analysis
DMFT values for each subject were used. The association between occlusion variables, oral health, dietary habits, and caries was assessed with the one-way ANOVA, the odds ratio and the χ 2 tests for evaluating the statistical significance. The significance level was set at 0.05.

Results
The study sample was composed of 536, 12-year old students (283 females, 253 males). Dental caries were recorded in 321 (59.8%) students. No difference was observed in the prevalence of caries between gender (χ 2 =0.70, p=0.40) or the different school districts (χ 2 =5.52, p=0.70). The mean value of DMFT was 1.81 ± 2.02 (1.94 ± 2.11 in girls and 1.67 ± 1.9 in boys, one-way ANOVA F=0.77, p=0.65); the decay (D) component was the most represented (1.45 ± 1.80) ( Table 2). The first permanent maxilla molar was the most affected by caries (46.83%) and the least prevalence was for the lateral incisors (0.34%) ( Table 3). Table 4 showed the distribution of the sample according to the occlusal variables. The first molar class was the most represented occlusion (59.41%), followed by second (35.66%) and third (4.94%) class. Overjet and overbite were normal for most students. A midline deviation was detected in the 32.09% of the sample, while the presence of crossbite was recorded in the 11.75% of the sample. Crossbite was the only occlusal variable significantly associated to caries experience (χ 2 =3.96, p=0.04) ( Tables 5 and 6). Crowding was more present in subjects with caries experience but not statistically significant (χ 2 =1.95, p=0.09) ( Table 7).
No association was found in group of adolescents brushing their teeth more time a day than who did not brush them assiduously (χ²=5.15; p=0.27) (Table 11).

Discussion
This study was designed and carried out in the schools of Naples, one of the most populous cities in Italy and one with the highest birth  be due to social and/or cultural differences [7,22,23]. Higher values of DMFT were found in students who had no intake of milk or dairy products. This finding may be in line with earlier studies showing that milk and dairy products consumption was associated with a less frequency of caries even if in this report the correlation was present but not statistically significant unlike other studies [22,[24][25][26], this discrepancy is probably due to the multifaceted etiology of caries.
In the last few years, a distinct association between oral hygiene and prevention of dental caries has been demonstrated [27][28][29]. Studies found out that the prevalence of caries was not related to correct oral hygiene practices, as also reported in other surveys, strengthening the         hypothesis of a multifactorial origin of caries [9,14,23,25,[27][28][29][30][31][32][33][34]. Several studies evaluating the relationship between crowding and dental caries have shown contradictory results, probably due to small sample size included in the studies [33,35,36].
The hypothesis that occlusal disorders may increase the risk of caries was also tested. The need of any orthodontic treatment should not be linked to a decreased risk of future caries, although the higher prevalence of caries was associated with the crossbite [30,32,37]. Today, the malocclusions and space anomalies are mainly not considered as predictors of caries [31]. However, further studies are needed to monitor whether South Italy students will achieve the ambitious DMFT goal of <1.5 for the year 2020 [17,18,[38][39][40][41].

Conclusion
Positive relationship was found between dental caries, parents' educational status and crossbite, whereas carious lesions, food intake, oral hygiene and the other type of occlusal disorder did not reveal any significant association in 12-year-old school children of Naples in the Southern Italy.