We collected 368 questionnaires from students in five different academic levels. The response rate of the questionnaire was 68% (368/540) and the effective rate of the questionnaire was 89% (328/368; Table 1). The reliability of the questionnaire was 0.852 (Cronbach's α index) and the validity of the questionnaire was 0.889 (KMO test).
Most students (264/328, 80%) had heard of MIH, and we found no significant difference between undergraduate and postgraduate students (λ2=5.513, p>0.01; Table 3). Moreover, most students had heard about MIH in more than one way. The most common source was classroom teaching (188/264, 71%), followed by clinical practice (111/264, 42%), lectures (56/264, 21%), journal articles (37/264, 14%), and other sources (15/264, 6%; Table 3). Some students (104/264, 39%) had observed MIH clinically (Table 2). The proportions of students that had observed MIH clinically was significantly different among the different academic levels in (λ2=62.928, p<0.01; Table 2). However, only 66 students (66/264, 25%) were confident in identifying MIH (Table 2), and the ability to identify MIH was significantly different among the different academic levels (λ2=65.267, p<0.01; Table 2). Few students (43/264, 16%) knew the diagnostic principles of MIH (Table 2). The proportions of students that knew the diagnostic principles of MIH were significantly different between academic levels (λ2=64.793, p<0.01; Table 2). All the aetiologies of MIH (i.e., genetic factors, pregnant and postnatal factors, drug factors, environment factors) were known by 93 students (93/264, 35%; Table 2). Most students (156/264,59%) believed that the incidence of MIH was less than 15%. However, the incidence rate was estimated at 15-30% by 100 students (100/264, 38%), 30-60% by 8 students (8/264, 3%), but no students estimated an incidence above 60% (Table 2).
Only 3% (9/264) of respondents had performed an MIH treatment (Table 2). Among these students, most were more inclined to use a pit and fissure seal, instead of fluoride varnish, for teeth mildly damaged by MIH. However, for teeth affected by MIH with moderate to severe dentin sensitivity, but no pulp symptoms, no one treatment was favored significantly more than the other choices (Table 2).
Among the respondents that had observed MIH clinically, most (66/104, 63%) were confident in distinguishing MIH from dental fluorosis, dentin hypoplasia, and other developmental dental diseases (Table 2). The probability of observing MIH clinically was 13% (13/104). The probabilities that students would encounter MIH clinically at frequencies of once per week, once per month, once per 6 months, once per year, and once per >1 year were 13% (13/104), 34% (35/104), 38% (39/104), 7% (7/104), and 10% (10/104), respectively (Table 2).
The vast majority of students (296/328, 90%) thought it was necessary to add MIH to the curriculum for future systematic teaching (Table 3). They felt that the most desirable parts to learn were the clinical manifestations, differential diagnosis, and treatment methods (Table 2). The most important ways to learn this knowledge were from textbooks (268/328, 82%), the literature (212/328, 65%), the internet (212/328, 65%), and lectures (169/328, 52%; Table 2).