This study showed that dental students, in general, have inadequate knowledge about syphilis. Moleri et al. [5] reported that although many universities present their curricula aimed at general knowledge, they often have not adequately prepared students to recognize and diagnose complex clinical conditions, such as those presented by syphilis.
In this perspective, few students know the oral manifestations of syphilis. In agreement with our research, Wu et al. [6] investigated the knowledge about occupational blood-borne pathogen among Chinese dental students and found that less than half of participants were able to answer which are the main oral manifestations of syphilis.
The main oral manifestations are hard chancre, mucous plaques and gumma. Oral chancre in primary syphilis is characterized as a painless ulcer, measuring 1 to 2 centimeters, with firm and rolled border [7]. It manifests as a single ulcer, usually on the lip or, more rarely, on the tongue [8]. Secondary syphilis presents multiple and generally symptomatic ulceration [9]. In these cases, lesions are maculopapular, affecting the hard palate and, sometimes, the soft palate8. Gumma, associated with tertiary syphilis, initially manifests as one or more painless swelling, especially on the hard palate [10].
Recognizing the oral manifestations of syphilis is a crucial role of the dentist, because as oral lesions are highly contagious, the reliability of the correct diagnosis helps in the adequate management, reduces the infection chain and reduces the risk of transmission to health professional [11]. It is worth mentioning that the form of transmission least reported by participants was through the dental practice. This occurs when correct professional practice is not established [3, 4].
In addition, a small percentage of students reported knowledge about the differential diagnoses of oral manifestations of the disease. Indeed, studies have shown that the diagnosis of oral manifestations of syphilis represents a challenge for professionals because they have a variety of clinical appearances [12, 13]. The fact that some characteristics may be similar to other conditions is of concern, and if diagnosis is not performed in the primary and secondary stages, the patient is exposed to the risk of complications related to the tertiary stage [12].
Our study also showed that students enrolled in the early years of the Dentistry course had better knowledge about etiologic agents, clinical manifestations, disease stages, oral manifestations and drugs than students enrolled in the last two years. The only association that was not statistically significant was in relation to differential diagnosis, where knowledge was low for both groups.
Unlike this research, studies that investigated the knowledge of dental students about HIV / AIDS [14–16] and occupational of blood-borne pathogens [17, 18] showed that knowledge about some aspects was greater among students with higher educational level. Keser et al. [14] justified this finding by the fact that the older group may have gained more experience over the years and was exposed to larger number of patients compared to the younger group. Brailo et al. [18] reported that this finding can be explained by the fact that in the clinical phase, at the beginning of the clinical practice in each department, students are introduced to this content again.
Usually, in the fist years of the Dentistry course, students have the Stomatology discipline, which addresses the content about syphilis and it’ s oral manifestations. However, we consider it essential that this content is addressed in other moments and disciplines throughout the undergraduate course, so that students are aware of all aspects that involve the disease, regardless of the educational level they are attending.
A fact that attracted attention was that studies on knowledge about the transmission of blood-borne pathogens among dental students conducted by Myers et al.[17] and Brailo et al.[18], published in 2012 and 2011, respectively, did not address syphilis. The study by Wu et al. [6], published in 2016, included the disease, probably due to its increasing prevalence worldwide. Syphilis started to become evident again a few years ago, so many clinicians do not consider syphilis in their differential diagnosis of oral lesions [19]. In Brazil, the disease has shown significant increase in incidence since 2010.
The number of participants who recognized penicillin as the drug of choice for treatment was less than expected. Penicillin became universal as an effective way of treating syphilis and was responsible for the significant decrease in the epidemiological numbers of the disease. This positive result in coping with the disease left a significant gap in medical and dental education [5].
The study has limitations due to its cross-sectional design. Another limitation was the limited number of articles published on the topic with dental students, which makes our research original. Our findings, together with the increased number of new cases of the disease in the world, reinforce the need for training dental professional with knowledge about early diagnosis, effective treatment and follow-up of syphilis cases. As the main form of infection transmission is sexual, its diagnosis and treatment must consider socio-cultural and ethical scope. The disease has repercussions on the affected people's way of life, and this issue should also be addressed during the undergraduate courses [20].
It is necessary to raise the student's interest not only in the clinical aspect of the disease, but also in care issues. Improving students' knowledge can be an effective way to increase the willingness to treat patients [6]. However, it is necessary to seek educational methods that can improve student's experience and learning skills.