Received: January 2025 | Accepted: March 2025 | Published: April 2025

Background: Dental caries, particularly Class I pit-and-fissure lesions of the first permanent molar, constitutes the most prevalent restorative diagnosis encountered among young Iraqi adults. Whether academic discipline serves as a meaningful proxy for oral health literacy — and whether that literacy translates into measurable differences in caries burden — has not been evaluated within private Iraqi universities.

Objectives: To compare the prevalence of Class I caries in first permanent molars across students from three faculties at Al-Turath University College, Baghdad (Dentistry, Anaesthesia, and Law), and to identify the behavioural and socioeconomic variables most strongly predictive of caries experience.

Methods: A cross-sectional study enrolled 150 undergraduate students (50 per faculty) through stratified random sampling during the 2024–2025 academic year. Clinical examinations were conducted by a single calibrated examiner following WHO 2013 diagnostic criteria. The DMFT index was recorded for each participant. A structured questionnaire captured dietary habits, oral hygiene practices, dental attendance, and socioeconomic background. Analyses employed descriptive statistics, chi-square tests, one-way ANOVA with Tukey’s post-hoc test, and multivariate binary logistic regression (SPSS v.26; significance threshold p < 0.05).

Results: Overall Class I caries prevalence in first molars was 70.7% (n = 106). Mean DMFT scores were 2.38 ± 1.18 (Dentistry), 3.94 ± 1.52 (Anaesthesia), and 5.12 ± 1.71 (Law); one-way ANOVA confirmed highly significant intergroup differences (F = 41.7; p < 0.001). All pairwise comparisons were significant on post-hoc testing. Independent predictors of caries on multivariate analysis included dental visits less than once yearly (OR 3.3; 95% CI 2.0–5.5), daily intake of two or more sugar-sweetened beverages (OR 2.9; 95% CI 1.7–5.1), and absence of prior fissure sealant application (OR 2.4; 95% CI 1.4–4.2).

Conclusion: Caries burden in first molars at Al-Turath University College rises progressively from health-science to non-health students, with faculty affiliation persisting as an independent predictor after sociodemographic adjustment. Expanding pit-and-fissure sealant outreach services and embedding oral health literacy content in non-health curricula are the most actionable recommendations arising from these data.

Dental caries is a biofilm-mediated, sugar-dependent, non-communicable disease characterised by the progressive demineralisation of tooth hard tissues under the influence of organic acids generated by fermentative oral microorganisms. Its global scale is formidable: the 2017 Global Burden of Disease Study estimated that untreated caries of the permanent dentition affected approximately 2.3 billion individuals worldwide, making it the single most prevalent condition in the GBD survey.¹ In Iraq, national and institutional data have repeatedly documented caries prevalence among schoolchildren and young adults that substantially exceeds WHO benchmarks, with DMFT values in late adolescence commonly reported between 3.0 and 5.5 depending on the study population and diagnostic criteria employed.²

Among all permanent teeth, the first molar carries the heaviest and earliest caries burden. Erupting around the age of six years — before the child has typically established consistent brushing habits and before parents have recognised the tooth as permanent — it enters a prolonged period of cariogenic challenge without the benefit of adequate preventive care. Its occlusal topography, comprising a network of deep central fossae, developmental grooves, and supplemental pits, creates ecological niches that are effectively inaccessible to a toothbrush and where the oxygen tension is low enough to favour the proliferation of acidogenic and aciduric bacteria, principally Streptococcus mutans and Lactobacillus species.³ Under the widely adopted Black classification, carious lesions originating in these sites are designated Class I, and they represent the highest-volume category of restorative treatment delivered in both public and private Iraqi dental clinics.?

University enrolment coincides with a phase of life during which multiple caries risk factors converge. Students transitioning into independent living characteristically shift toward energy-dense, carbohydrate-rich diets; increase their consumption of sugar-sweetened beverages and caffeinated drinks; adopt irregular meal patterns; and reduce the frequency of professional dental attendance owing to financial constraints or perceived low need.? Psychological stress — whether from examinations, social pressures, or financial concerns — has been associated with elevated salivary cortisol, reduced salivary flow, and impaired immune surveillance in the oral cavity, all of which may facilitate caries progression.? The combination of these exposures renders the undergraduate years a period of heightened vulnerability even in students who maintained reasonable oral health during childhood.

Within any university, students in different faculties share a campus environment yet diverge sharply in the health content of their academic programmes. Students enrolled in dentistry receive systematic instruction in the aetiology, epidemiology, clinical diagnosis, and management of dental caries, as well as in the personal and professional dimensions of oral health promotion.? This immersion in health-science thinking arguably reshapes attitudes toward self-care in ways that extend beyond mere knowledge acquisition, generating a form of professional identity that motivates behaviour change. Students in anaesthesia techniques occupy an intermediate position: their medical science training provides partial exposure to concepts of infection, inflammation, and systemic health, but oral health is rarely foregrounded in the curriculum. Students in law, by contrast, receive no formal health-science education whatsoever, leaving their oral health literacy dependent entirely on informal sources such as family habits, media, and serendipitous healthcare encounters.?

In the Iraqi context, studies comparing dental caries across students from different academic disciplines within the same institution are rare. Published mean DMFT values for Iraqi dental students range from approximately 2.1 to 3.9, depending on the university and year of study, while equivalent values for non-health university students have been reported as high as 5.3.? These disparities point to a discipline-linked gradient in caries experience, yet the evidence base is fragmented across different institutions, time points, and diagnostic protocols, making direct comparison unreliable. Al-Turath University College, which houses faculties of Dentistry, Anaesthesia, and Law on a single campus in Baghdad, offers an unusually controlled natural setting in which to examine this gradient with all three groups examined simultaneously by the same examiner under identical conditions.

Pit-and-fissure sealants represent one of the most robustly evidence-based preventive interventions available for Class I caries in first molars, with Cochrane-level evidence documenting a substantial reduction in occlusal caries incidence when sealants are placed at or shortly after eruption.¹? Yet sealant uptake in Iraq remains low outside specialised dental training clinics, and awareness of the procedure is negligible among non-health student populations. Identifying the magnitude of unmet sealant need across faculties is therefore a prerequisite for designing targeted outreach programmes.

Against this background, the present study was designed to determine and compare the prevalence of Class I caries in first permanent molars across students from the Colleges of Dentistry, Anaesthesia, and Law at Al-Turath University College, to quantify the DMFT burden in each group using a standardised protocol, and to identify the behavioural and socioeconomic predictors that drive intergroup differences. The findings are intended to provide an evidence base for faculty-level oral health policy at Al-Turath and to contribute to the growing body of Iraqi epidemiological literature on caries in young adults.

A descriptive cross-sectional study was conducted between October 2024 and February 2025 at Al-Turath University College, Baghdad — a private institution that accommodates faculties of Dentistry, Anaesthesia Techniques, and Law on a unified campus in the Al-Karkh district. Ethical approval was secured from the Al-Turath University College Research Ethics Committee (Reference: ATUC-REC-2024-088) in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants before enrolment, and confidentiality of data was guaranteed throughout.

The required sample size was calculated using the standard formula for estimating a proportion: n = Z² × p(1 − p) / d², where Z = 1.96 (95% confidence level), anticipated caries prevalence p = 0.68 (based on Al-Nakash and colleagues’ 2021 Baghdad survey²), and acceptable margin of error d = 0.08. This yielded a minimum of 131 participants. The target was inflated to 150 (50 per faculty) to ensure balanced three-group comparisons and to accommodate up to 10% incomplete records. Participants were recruited by stratified random sampling from the official enrolment registers provided by each faculty’s administrative office, with individual students selected using computer-generated random numbers.

Inclusion criteria were: Iraqi nationality; age 18–26 years; enrolment in the second, third, or fourth academic year; presence of at least one erupted first permanent molar; and provision of written informed consent. Students were excluded if they reported a systemic condition affecting salivary function (e.g., Sjögren’s syndrome, uncontrolled diabetes mellitus), were currently undergoing or had previously undergone fixed orthodontic treatment involving molar bands, presented with confirmed molar hypomineralisation, or were unable to cooperate with the clinical examination.

All clinical examinations were performed by a single examiner to eliminate inter-examiner variability. Calibration was conducted one week before data collection: the examiner independently assessed 20 non-study volunteers and then repeated the assessment 72 hours later; intra-examiner agreement was evaluated using the kappa statistic (κ = 0.89, near-perfect agreement). Examinations were performed under standardised conditions: portable LED headlamp illumination, participants reclined in a portable dental chair, and teeth dried with cotton pellets before assessment. A WHO ball-ended probe (diameter 0.5 mm) and front-surface mouth mirror were used throughout. The WHO 2013 diagnostic threshold was applied: a surface was recorded as carious only when the probe tip engaged a clearly cavitated defect. Stained but intact fissures were recorded as sound. Bitewing radiographs were not obtained, meaning proximal and subclinical enamel lesions were not captured.

The DMFT index was recorded for all 28 teeth (third molars excluded). For the primary outcome measure, Class I caries status was assessed on the occlusal surfaces of the four first permanent molars (FDI notation: 16, 26, 36, 46). Each tooth was classified as Decayed (D), Missing due to caries (M), or Filled (F) in accordance with WHO 2013 criteria. Teeth that were congenitally absent, unerupted, or lost due to trauma were excluded from the denominator. A participant was classified as caries-positive if at least one first molar displayed an active or restored Class I lesion.

A structured, self-administered questionnaire was developed, pre-tested on 15 pilot participants not included in the main analysis, and revised for clarity before final deployment. It captured: age and sex; monthly household income (categorised in Iraqi Dinar: < 500,000; 500,000–1,000,000; > 1,000,000); daily toothbrushing frequency; type of dentifrice used; frequency of dental attendance; daily number of sugar-sweetened beverage portions; previous experience of fissure sealant application; current smoking status; and self-rated oral health on a five-point Likert scale.

Data were entered in duplicate and analysed using IBM SPSS Statistics version 26. Continuous variables are presented as mean ± standard deviation (SD); categorical variables as absolute frequency and percentage. The Shapiro–Wilk test was used to assess normality of DMFT distributions. One-way ANOVA with Tukey’s Honest Significant Difference post-hoc test compared mean DMFT across the three groups. Chi-square tests assessed associations between caries status and categorical risk factors. Multivariate binary logistic regression (outcome: caries-positive vs. caries-negative) identified independent predictors while adjusting for age, sex, and household income; results are reported as odds ratios (OR) with 95% confidence intervals (CI). The Hosmer–Lemeshow test evaluated model calibration. Statistical significance was set at p < 0.05 throughout.

All 150 enrolled students completed both the clinical examination and the questionnaire (response rate 100%). The Dentistry cohort comprised 50 students (mean age 21.2 ± 1.5 years; 29 female, 21 male). The Anaesthesia cohort comprised 50 students (mean age 21.7 ± 1.8 years; 25 female, 25 male). The Law cohort comprised 50 students (mean age 22.0 ± 2.1 years; 22 female, 28 male). No statistically significant differences in age (p = 0.18) or sex distribution (p = 0.41) were detected across groups. Household income was broadly comparable, with 73% of the total sample reporting monthly income between 500,000 and 1,000,000 IQD. Full demographic data are presented in Table 1.

Characteristic	Dentistry (n = 50)	Anaesthesia (n = 50)	Law (n = 50)
Mean age ± SD (years)	21.2 ± 1.5	21.7 ± 1.8	22.0 ± 2.1
Female, n (%)	29 (58%)	25 (50%)	22 (44%)
Male, n (%)	21 (42%)	25 (50%)	28 (56%)
Income < 500k IQD, n (%)	7 (14%)	13 (26%)	18 (36%)
Income 500k–1M IQD, n (%)	37 (74%)	32 (64%)	26 (52%)
Income > 1M IQD, n (%)	6 (12%)	5 (10%)	6 (12%)

 

Class I caries was detected in at least one first permanent molar in 106 of 150 participants, giving an overall prevalence of 70.7%. Faculty-specific figures were 48.0% (Dentistry; n = 24), 72.0% (Anaesthesia; n = 36), and 92.0% (Law; n = 46). Chi-square analysis confirmed a highly significant association between faculty affiliation and caries presence (χ² = 28.9, df = 2, p < 0.001). Table 2 shows the tooth-level distribution of affected first molars across the three groups.

Tooth (FDI)	Dentistry (%)	Anaesthesia (%)	Law (%)	Overall (%)
UR 1st Molar – 16	34%	54%	74%	54%
UL 1st Molar – 26	32%	58%	76%	55%
LR 1st Molar – 36	40%	64%	84%	63%
LL 1st Molar – 46	38%	62%	80%	60%
≥ 1 molar affected	48%	72%	92%	70.7%

 

One-way ANOVA revealed highly significant intergroup differences in mean DMFT (F(2,147) = 41.7, p < 0.001). Dentistry students recorded the lowest mean DMFT (2.38 ± 1.18), Anaesthesia students an intermediate value (3.94 ± 1.52), and Law students the highest (5.12 ± 1.71). Tukey’s HSD post-hoc test confirmed that all three pairwise differences were statistically significant: Dentistry vs. Anaesthesia (p = 0.001), Dentistry vs. Law (p < 0.001), and Anaesthesia vs. Law (p = 0.002). The Decayed component accounted for the largest fraction of the DMFT in all groups, reflecting low rates of restorative treatment uptake. Full DMFT component data are presented in Table 3.

Faculty Group	D (mean ± SD)	M (mean ± SD)	F (mean ± SD)	DMFT (mean ± SD)	p-value (vs. Dentistry)*
Dentistry (n = 50)	1.74 ± 0.94	0.20 ± 0.41	0.44 ± 0.67	2.38 ± 1.18	Reference
Anaesthesia (n = 50)	2.98 ± 1.28	0.46 ± 0.64	0.50 ± 0.73	3.94 ± 1.52	0.001
Law (n = 50)	4.12 ± 1.58	0.64 ± 0.82	0.36 ± 0.61	5.12 ± 1.71	< 0.001
Overall (n = 150)	2.95 ± 1.48	0.43 ± 0.65	0.43 ± 0.67	3.81 ± 1.77	—

Chi-square analysis identified statistically significant intergroup differences in all major behavioural risk factors examined (Table 4). Infrequent toothbrushing (once daily or less) was reported by 16% of Dentistry, 44% of Anaesthesia, and 66% of Law students (p < 0.001). Consumption of two or more portions of sugar-sweetened beverages per day was reported by 20%, 50%, and 68% respectively (p < 0.001). The proportion of students who had never received a fissure sealant was 36% in Dentistry, 74% in Anaesthesia, and 92% in Law (p < 0.001). Dental visits occurring less than once per year were reported by 18%, 54%, and 74% across the three faculties (p < 0.001).

Risk Factor	Dentistry n (%)	Anaesthesia n (%)	Law n (%)	χ² (p-value)
Brushing ≤ once daily	8 (16%)	22 (44%)	33 (66%)	28.4 (< 0.001)
SSB intake ≥ 2 portions/day	10 (20%)	25 (50%)	34 (68%)	24.8 (< 0.001)
No fissure sealant ever	18 (36%)	37 (74%)	46 (92%)	38.2 (< 0.001)
Dental visit < once/year	9 (18%)	27 (54%)	37 (74%)	36.1 (< 0.001)
No fluoride toothpaste	3 (6%)	11 (22%)	18 (36%)	17.9 (< 0.001)
Current smoker	4 (8%)	9 (18%)	15 (30%)	10.6 (0.005)
Poor self-rated oral health	5 (10%)	18 (36%)	29 (58%)	30.3 (< 0.001)

After adjusting for age, sex, and household income, three behavioural variables emerged as significant independent predictors of Class I caries presence (Table 5): dental attendance less than once per year (OR 3.3; 95% CI 2.0–5.5; p < 0.001), daily consumption of two or more portions of sugar-sweetened beverages (OR 2.9; 95% CI 1.7–5.1; p = 0.001), and absence of any prior fissure sealant (OR 2.4; 95% CI 1.4–4.2; p = 0.002). Faculty affiliation, entered as a categorical variable with Dentistry as the reference, retained independent significance for both the Anaesthesia group (OR 2.7; 95% CI 1.4–5.4; p = 0.004) and the Law group (OR 5.8; 95% CI 2.7–12.4; p < 0.001). The final model demonstrated satisfactory calibration (Hosmer–Lemeshow χ² = 5.8; p = 0.67) and explained 53% of the variance in caries status (Nagelkerke R² = 0.53).

Predictor Variable	β	OR	95% CI	p-value
Dental visit < once/year	1.19	3.30	2.0–5.5	< 0.001
SSB ≥ 2 portions/day	1.06	2.90	1.7–5.1	0.001
No fissure sealant ever	0.88	2.40	1.4–4.2	0.002
Faculty: Anaesthesia (ref = Dentistry)	0.99	2.70	1.4–5.4	0.004
Faculty: Law (ref = Dentistry)	1.76	5.80	2.7–12.4	< 0.001
Constant	−1.54	0.21	—	—

The principal finding of this investigation is a near-doubling of Class I caries prevalence from Dentistry students (48%) to Law students (92%), with Anaesthesia students occupying a statistically distinct intermediate position (72%). This three-step gradient, sustained after multivariate adjustment for age, sex, and income, supports the interpretation that academic exposure to health-science content confers a tangible protective effect against caries in the first permanent molar — an effect that operates partly through the behavioural pathways captured in this study (brushing frequency, dietary habits, sealant uptake, dental attendance) and partly through unmeasured channels such as professional identity, peer-group norms, and access to in-faculty clinical services.

The overall mean DMFT of 3.81 recorded in this sample is consistent with the Iraqi institutional literature. Al-Nakash and colleagues reported a mean DMFT of 3.2 among first-year Baghdad dental students in 2021,? while a contemporaneous survey of non-health students at Al-Mustansiriyah University yielded a value of 4.8 — close to the 5.12 observed here in Law students.¹¹ The Dentistry group’s mean DMFT of 2.38 falls within the range of 2.1–2.9 reported for Iraqi dental students in studies published since 2018, suggesting that dental training environments at different Baghdad institutions produce broadly comparable oral health outcomes.² The persistence of mean DMFT values above 3.0 across all groups in this study, however, underscores that even health-science students fall well short of the WHO’s DMFT ≤ 1 target for the 12-year cohort — a target that, though technically defined for a younger population, implicitly frames the aspiration for caries-free young adulthood.

At the tooth level, mandibular molars (teeth 36 and 46) were more frequently affected than their maxillary counterparts (16 and 26) across all three faculties, a finding reported consistently in the Iraqi and regional literature.¹³ Two mechanisms are most commonly invoked: the lower first molars erupt earlier on average, extending their period of cariogenic exposure, and they receive less salivary buffering from the parotid flow that washes the upper posterior quadrants.¹? The slightly higher prevalence in tooth 36 compared with 46 — observed in the Dentistry and Anaesthesia groups — may additionally reflect a laterality effect, whereby right-handed individuals tend to brush the lower-left quadrant less effectively.¹?

Multivariate logistic regression identified dental attendance frequency as the strongest single behavioural predictor of caries status (OR 3.3). This finding resonates with the service-utilisation literature, which consistently shows that preventive interventions delivered during dental visits — fissure sealing, fluoride varnish application, dietary counselling — reduce caries incidence more powerfully than any equivalent self-care behaviour change in isolation.¹? In the Iraqi private university context, barriers to regular attendance include cost of treatment, absence of subsidised student dental health schemes, perception that treatment is only warranted for symptomatic disease, and competing academic time pressures. Addressing these barriers at institutional level — for instance through subsidised student dental clinics or mandatory annual check-up programmes — may yield larger population-level benefits than communication campaigns focused on dietary or hygiene behaviour alone.¹?

The absence of prior fissure sealant application was an independent predictor of caries (OR 2.4), and the intergroup difference in sealant experience was striking: 92% of Law students reported never having received a sealant, compared with only 36% of Dentistry students. This disparity is unlikely to reflect only parental dental literacy or childhood healthcare access; it also reflects the self-application of skills within the dental faculty, where students routinely perform preventive procedures on one another as part of clinical training. The implication is that a fissure sealant outreach programme — in which preclinical dental students provide sealant application to students from non-health faculties as a supervised skills exercise — could simultaneously address the sealant access gap and provide a meaningful training opportunity. Such programmes have been trialled with favourable outcomes in university settings in Jordan and Egypt and deserve evaluation in the Iraqi private university context.¹?

Several limitations should be acknowledged. The cross-sectional design precludes causal inference: the observed intergroup differences may partly reflect pre-enrolment selection, whereby students with higher health consciousness disproportionately choose health-related programmes. The absence of bitewing radiographs means proximal and incipient enamel lesions were not captured, leading to systematic underestimation of total caries burden — though this applies equally to all three groups and therefore does not compromise intergroup comparisons. The single-campus, single-institution design limits generalisability to other Iraqi private or public universities where socioeconomic profiles, academic cultures, and clinical facility access may differ. Finally, the questionnaire relied on self-report for dietary and behavioural variables, introducing the possibility of social desirability bias.

Future research should incorporate radiographic assessment and a longitudinal component to establish caries incidence rates and to evaluate the effect of targeted interventions. Multi-site replication across public and private Baghdad institutions, as well as in other Iraqi governorates, would permit more confident generalisations. Qualitative work exploring the mechanisms through which academic discipline shapes oral health behaviour — whether through knowledge, professional identity, peer norms, or structural factors — would further inform intervention design.

At Al-Turath University College, Class I caries of the first permanent molar was detected in 70.7% of the combined student sample, with prevalence rising progressively and significantly from Dentistry (48%) to Anaesthesia (72%) to Law (92%) students. Mean DMFT values followed the same gradient (2.38, 3.94, and 5.12 respectively), with all pairwise differences reaching statistical significance. Faculty affiliation remained an independent predictor of caries after controlling for sociodemographic confounders, suggesting that curriculum-mediated health literacy confers a meaningful protective effect. The most modifiable risk factors identified — infrequent dental attendance, high sugar-sweetened beverage intake, and absence of fissure sealants — point toward three concrete intervention priorities: establishing a subsidised student dental clinic at Al-Turath, integrating structured oral health modules into the Anaesthesia and Law curricula, and implementing a fissure sealant outreach programme through which dental students provide preventive care to their non-health peers.

Funding: This study received no external funding. All costs were covered by the research team.

Conflicts of interest: The authors declare no conflicts of interest.

Ethical approval: Approved by the Al-Turath University College Research Ethics Committee (Ref: ATUC-REC-2024-088).

Data availability: Anonymised data are available from the corresponding author upon reasonable request.

Author contributions: All eight authors contributed equally to study conception, data collection, analysis, manuscript drafting, and critical revision.

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