Background The quarantine associated with the COVID-19 pandemic forced dental schools to suspend their clinical training and to shift to distant learning methods. The aim of this study is to investigate the impact of quarantine on the self-perceived preparedness of dental graduates and to explore the efficacy of online education from students’ perspectives. Methods The questionnaire distributed to dental students comprised of two main sections. The first part covered the online education experience, and the second part measured the level of self-perceived preparedness for a range of cognitive, communication and professional skills. Results The survey yielded a response rate of 72%. The majority of students (77%) agreed that they missed educational experiences as a result of the lockdown. More than half of them felt less motivated to follow-up with distant e-learning and believed that online assessment is not a good method for evaluation. A high percentage of the students (66%) thought that online group discussions had a positive value while 67% preferred online lectures compared to theatre lectures. Majority of students particularly 5th year (78.7%) (p < 0.001) stated that the quarantine increased their collaboration with their colleagues. According to 87% of students, the experience most negatively affected was their clinical training. In general, students showed satisfactory self-perceived preparedness related to a range of attributes and professional skills. Conclusions The data showed that students partially appreciated the online system, whereas they did not consider it a substitute for face to face clinical practice. The overall self-perceived preparedness level was promising; however students had reservations regarding independent practice following graduation.

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Five samples of powered enamel were each sequentially equilibrated 5 times at 37°C with either 4 or 17 mmol/l H₃PO₄, in contact with air, and the ionic activity product for hydroxyapatite (I_HA) estimated. There was evidence for preferential release of Mg and Na, especially in the first equilibrations. In two experiments, raised values of I_HA were observed in the first equilibration but otherwise I_HA was reasonable constant within experimental error and was much closer to the solubility product of hydroxyapatite than many previous estimates, mainly at 25°C, suggest. The mean value of I_HA for the majority fraction, averaged over all samples, was 1.7 ( ± 0.7) 10^-58. Non-apatitic solids formed in all systems but solubility appeared nevertheless to be controlled by an apatitic phase: either the enamel mineral itself or apatite reprecipitated during the course of equilibration. High values of I_HA reported previously may be due to use of conditions favouring dissolution only of more soluble factions or to metastability artifacts associated with control of solubility by non-apatitic phases.

The residues of 5 samples of powdered human enamel, each subjected to 5 sequential equilibrations at 37°C with either 17 or 4 mmol/l phosphoric acid, were examined microscopically. With 17 mmol/l acid, both brushite and monetite were found after 1 equilibration but, after further equilibrations, brushite was no longer present and the abundance of monetite crystals increased. Formation of monetite probably contributed to the lower metastability of this system compared to similar low-pH systems at 25 °C, where monetite does not form. Neither brushite nor monetite were present after equilibration with 4 mmol/l acid. Whitlockite was identified by transmission electron microscopy and electron diffraction in all residues. In the 4 mmol/l systems, the ionic activity product (IMwh) for magnesium whitlockite, Ca₉Mg(HPO₄)(PO₄)₆, became constant after 1–3 equilibrations, at a mean value of 3.6 ( ± 0.51 SE)·10^––105, which may reflect saturation with respect to this solid. For the 17 mmol/l systems, higher values of IMWH, and supersaturation with respect to monetite, were interpreted as evidence for persistent metastability due to slow crystal growth of whitlockite and monetite. It is concluded that neither brushite nor monetite are likely to form within carious lesions, but the results are consistent with the known association of whitlockite with caries.

The purpose of this study was to see if gender-based differences exist in the performance of dental students at the University of Jordan (UJ), Amman. The retrospective analysis included data from two groups of students: 413 fourth-year dental students (178 males and 275 females) from four consecutive years (2005 through 2008) and 357 fifth-year students (128 males and 229 females) who graduated in the years 2005 to 2008. The influence of gender on the results of the fourth-year students in six theoretical and six clinical courses and the cumulative GPAs of the fifth-year students were studied. In both theoretical and clinical fourth-year courses, multivariate analysis of variance (MANOVA) revealed significant main differences in raw scores between the two gender groups. Female students were significantly better in five theoretical courses. In clinical courses, female students outscored male students in pediatric dentistry and prosthodontics, male students outperformed female students in conservative dentistry and orthodontics, and no significant gender differences were seen in oral surgery and fixed prosthodontics. The cumulative GPAs of the female graduated students were significantly higher than those of the male students. The results showed a significant relationship between gender and academic performance of dental students for these classes.