In 2006, a French national report revealed that university students neglected their health [1]. These young adults think they are healthy and feel invulnerable. In general, they had poor dietary and oral hygiene habits and often failed to seek dental care. The report also noted risk behaviors, particularly smoking, excessive alcohol consumption, and the daily use of certain drugs considered to be less dangerous than tobacco, particularly cannabis. Over the last 10 years, particular emphasis has been placed upon promoting a balanced diet and the prevention of risk behaviors in French universities.

In a review published in The Lancet by Selwitz et al. in 2007, caries risk assessment included physical, biological, environmental, behavioral, and lifestyle-related factors [2]. The individual caries risk can vary with time since many risk factors are changeable. Caries is related to one’s lifestyle, and behavioral factors under a person’s control are clearly implicated [3–6]. These factors include poor oral hygiene [7–9] and poor dietary habits [10–13]. Other factors related to caries risk include socio-economic status [3, 5, 6], the use of dental sealants [14, 15], and dental crowding, which promotes plaque retention and increases the difficulty of maintaining good oral hygiene [16]. Besides, the relative caries preventive effects of fluoride toothpastes of different concentrations increase with higher fluoride concentration [17]. Though, in France, toothpastes sold in pharmacies need a special authorization (AMM) because the amount of fluorides is high (1500 ppm and more), and they are therefore considered as medicines. Because they are less fluoridated (1450 ppm and less), toothpastes in supermarkets are considered as hygiene products.

Numerous studies performed among undergraduate students have concerned dental students [18] but have less often studied the general university student population. However, dental students constitute a selected minority that is clearly demarcated from students of other disciplines regarding a higher awareness of self-reliant oral hygiene [18]. The DMFT score of undergraduate students has been the object of studies in various universities worldwide. Studies in Europe, North America, Asia and the Middle East show that the DMFT score of undergraduate students range from 4.1 ± 3.1 at Sana’a University in Yemen [19] to 3.9 ± 3.9 at San Luis Potosí University in Mexico [20], 2.9 ± 3.3 at Helsinki University in Finland [21], 2.0 ± 2.9 at Okayama University in Japan [22], and 1.2 ± 2.0 at Nice Sophia Antipolis University in France [23].

Low sugar consumption and good oral hygiene are critical for the prevention of caries and the maintenance of good oral health [24]. In Lebanon, 65% of undergraduate students reported brushing their teeth at least twice per day [25], while that percentage was 68% in Turkey [26], 74% in the USA [27], 87% in Japan [28], and 92% in Italy [29] and France [23]. Of subjects in Turkey, 91% reported never flossing versus 87% in Japan, 80% in France, 72% in Lebanon, 35% in Italy and 20% in the USA. Of the students in France and Italy, 62% and 60%, respectively, reported visiting a dentist during the previous year, while these percentages were only 31% in Lebanon and 30% in Turkey. High sugar consumption has long been linked to dental caries [30]. A quarter of USA Midwestern university students reported eating sugary foods (including foods and drinks, such as candies, soft drinks, juices, doughnuts, jellies, etc.) more than once daily. Among the 89% of students who reported drinking pop, 69% selected regular pop as their favorite as opposed to diet pop [27].

Smoking habits may also be associated with a higher risk of dental caries [31]. Self-reported use of tobacco among adolescents was significantly associated with an increased incidence of dental caries over a 3-year period [32]. This association was also apparent with alcohol [33–35] and drug abuse [36–38].

No data are available in France concerning the specific caries risk factors among university students. However, in France, university students often leave their family for the first time to study at a university that occasionally is far from home [39]. This assertion of autonomy may be particularly risky for their oral health. A national survey was conducted in Finland, and based on the university health department registries, an electronic questionnaire was sent to first-year students on their general, emotional, and oral health [40]. This survey revealed an increased risk of deterioration of oral health and thus a need for treatment in relation to poor habits regarding oral health and diet.

In France, all university students in their first 3 years of study are required to attend a preventive medical consultation [41]. In the Côte d’Azur University, this consultation takes place during the first year of study. A preventive dental consultation conducted by final-year dental students has also been implemented for more than 10 years. The purpose of this study was to rank the risk factors for dental caries among first-year university students.

The multivariate analysis made it possible to rank the risk factors for dental caries among the first-year university students of Nice in the first half of 2015. These risk factors were failure to seek dental care due to financial reasons followed by poor oral hygiene revealed during the oral examination and poor self-reported oral health.

In 2014, the Student Life Observatory published the results of a national survey about the living conditions of students in France [45]. Among other findings, this survey revealed that 11% of the students were not satisfied with their current health status and that 13% confessed to having already failed to seek medical care due to financial reasons. Many social assistance programs exist, for example, universal supplementary health coverage (CMUc [couverture maladie complémentaire universelle]) (free supplementary health coverage meant to facilitate access to healthcare for the low-income population with a stable and regular residence in France) and payment assistance for the supplementary health aid system (ACS [aide au paiement d’une complémentaire santé]) (aid that offers discounts on the premiums for supplementary health coverage for low-income populations with incomes slightly higher than the limit set for the allocation of CMUc). These programs make it possible to provide 100% dental coverage in France [46]. In 2015, a French national report revealed that 19.1% of students lived below the poverty line, i.e., less than 987 euros per month. The advance of dental fees can be perceived as unaffordable in this context [47].

The presence of dental plaque and/or calculus revealed during the oral examination can likely be more strongly attributed to the inadequate behavior of some students. Nevertheless, the French Union for Oral Health (UFSBD [Union Française pour la Santé Bucco-Dentaire]) issues good practice guidelines for the general public to ensure adequate oral hygiene. More specifically, this organization focuses on adults under the age of 40 and recommends at least two brushings per day, the use of fluoride toothpastes, the use of floss in the evening, a preventive visit to the dentist at least once per year, and the use of sugar-free chewing gums after each food intake [48].

The univariate analysis also highlighted the possible role of periodontal disease, even mild cases. Yet, gingivitis is often correlated with the presence of plaque, which is the consequence of a lack of brushing. Both periodontal status and poor oral hygiene were included in the multivariate logistic regression model, and only poor oral hygiene remained a proven risk factor. The main advantage of the multivariate analysis was thus to avoid confounding effects that arise by analyzing the associations of all variables together. Good practice guidelines are not sufficient to enhance a good oral hygiene for students. Actually, in France, there is no dental hygienist to educate patients in regard to diet and oral hygiene habits. Nevertheless, the success of the dental hygienist in the dental health education of patients has long been recognized in terms of influencing behavior [49]. A Swedish study revealed that patients’ attitudes were less negative towards dental hygienists than towards dentists [50]. This difference was more pronounced among students than general patients and patients with periodontal disease. Therefore, this specific population could greatly benefit from the introduction of dental hygienists in France.

The highest-ranking caries protective factor among the study population was the use of dental sealants, followed by the use of an electric toothbrush and a preventive visit to the dentist. Sealants are used and have been recommended in France since the early 2000s, and their efficacy is well documented [51]. The role played by the presence of sealant remnants is thus not surprising. Our results also confirmed recent studies that tend to prove the superiority of the use of electric brushing over manual brushing [52]. Preventive dental consultations remain rare in France despite institutional incentives. Since 2007 the “M’T dents” (love your teeth!) program has been offering all children aged 6, 9, 12, 15 and 18 one free dental consultation and treatment, if necessary [53]. The purpose of this initiative was to develop the habit of preventively visiting the dentist. However, 41% of the students had not visited the dentist in the previous year. Moreover, the reason for the last dental appointment was preventive in only 69% of the cases.

The strengths of our study lie in supplying French data on a rarely studied population. The originality comes from the peer-led action among students. A study conducted in India focused primarily on dental students and revealed the positive attitude of this category of students towards their own oral health [54]. The authors mentioned the potential interest of a peer-driven prevention approach (dental students versus the students of other fields) to promote oral health on university campuses.

The limitations of our study arise from both the participation of only volunteer students and the cross-sectional design, which only provides a snapshot of our outcome at a specific point in time and provides no indication of the sequence of events. The oral examinations were performed in screening conditions, and an underestimation of the number of students affected by caries is possible. However, the use of recognized indices to estimate the dental caries status (i.e., the DMFT index), the oral hygiene (i.e., the plaque index and the calculus index) and the periodontal status (i.e., CPITN) likely limit these biases.

Students are known to neglect their oral hygiene and are particularly vulnerable to dental decay. The highest-ranking caries risk factor for the study population was the financial barrier.