The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks divided into three groups: Tetric N-Ceram Bulk Fill, Opus Bulk Fill APS, and Filtek Bulk Fill. Each resin composite group was further divided into two subgroups: with and without OIL control. Subsequently, surface roughness and microhardness were measured before and after polishing. A t-test was used to compare independent and related measures. For the intergroup comparison of variation before and after polishing, the Kruskal–Wallis test with Bonferroni post hoc was used considering a significance level of p < 0.05. When comparing surface roughness, significant differences were observed between Opus Bulk Fill resin composite with and without OIL control (p = 0.003) before polishing. The same occurred when comparing Tetric N-Ceram resin composite with and without OIL control (p = 0.039) after polishing. In addition, the surface roughness of Filtek Bulk Fill, Opus Bulk Fill, and Tetric N-Ceram Bulk Fill resin composites, with and without OIL control, decreased significantly after polishing (p < 0.001), while surface microhardness significantly increased (p < 0.05), with the exception of Opus Bulk Fill resin with OIL control (p = 0.413). In conclusion, OIL control and polishing significantly improved the surface roughness and surface microhardness of Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites. However, in the case of Opus Bulk Fill resin composite, only its surface roughness was significantly improved.

Background The contraction presented by resin composites causes an increase in stress at the tooth-resin interface, causing micro-gaps that allow microleakage. This study aims to evaluate the degree of in vitro marginal microleakage in class II restorations with two bulk fill resin composites compared to a conventional nanohybrid resin composite. Methods The present study was an in vitro experimental design. A total of 30 standardized class II cavities were prepared in 15 human molars (mesially and distally). These cavities were later distributed in 3 groups according to the type of resin. Groups A and B were restored with bulk fill resin composites (Filtek—3 M/ESPE and Tetric N-Ceram—Ivoclar/Vivadent respectively) in a single increment of 4 mm. Group C was restored with the Filtek Z350 XT – 3 M/ESPE resin composite and two increments of 2 mm. Later, the restorations were subjected to 10,000 thermocycles between 5 °C to 55 °C and immersed in a silver nitrate solution (1 M for 24 h). The crowns were then sectioned mesiodistally and observed under the stereomicroscope to determine the degree of marginal microleakage at the occlusal and cervical areas. The results were analyzed with the Kruskal–Wallis and the Mann–Whitney U statistical tests. Results There were no statistically significant differences regarding the degree of microleakage between the three types of resin composites in the occlusal and cervical areas (p > 0.05). Similarly, there were no significant differences after comparing each resin type in its occlusal and cervical area (p > 0.05). Conclusion Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites showed no statistically significant differences with the conventional nanohybrid resin composite Filtek Z350XT at both occlusal and cervical areas.

Background Metalloproteinases are proteolytic enzymes that degrade dentin and periodontal collagen; therefore, it is of special interest that dental students know its mechanism of action and how its effects can be inhibited. Therefore, the aim of this research was to evaluate the level of knowledge about metalloproteinases in dental students close to graduate from three universities in Peruvian capital city. Materials and methods In this analytical, observational, cross‐sectional and prospective study, 223 dental students close to graduate in three Peruvian universities were evaluated from September to November 2020. A questionnaire of 20 closed questions with three answers was validated and used to measure the level of general and dental knowledge about metalloproteinases. A logit model was used to evaluate the influence of the following variables: “gender” (X1), “type of university” (X2), “marital status” (X3) and “age group” (X4), in the knowledge levels of the students, considering a p‐value <.05. Results Of the 223 dentistry students, it was obtained that the level of knowledge about metalloproteinases was predominantly low with 82.1%, (95% confidence interval (CI): 77.1%–87.1%) of the total. According to multivariate logistic regression analysis, "type of university" was the only variable that proved to have a significant influence (p = .022) on the level of knowledge about metalloproteinases with an odds ratio of (OR = 0.44; CI: 0.21–0.89), whilst the other variables "age group" (p > .05), "gender" (p = .058) and "marital status" (p = .114) were not considered influential factors. Conclusion The majority of final year dental students in three Peruvian universities presented a low level of overall knowledge about metalloproteinases. In addition, private university students were 56% less likely to pass the subject knowledge test. On contrary, gender, age group and marital status did not significantly influence the level of knowledge of the students.

Peru was the country with the highest COVID-19 case fatality rate worldwide during second wave of infection, with dentists and pre-professional students being susceptible to infection due to clinical procedures they perform. This situation could have generated some kind of psychological disorder within this group. Therefore, the present study aimed to assess how COVID-19 pandemic affected this population group during second wave, in relation to depression, anxiety and stress. This observational and cross-sectional study in 368 Peruvian dentists (186 students and 182 professionals), was carried out during August to November 2021. The DASS-21 Scale was used to diagnose depression, anxiety and stress. For the statistical analysis, Pearson's chi-square test was used, in addition to a logit model using odds ratio (OR) to evaluate depression, anxiety and stress with the following factors: gender, age group, marital status, monthly family income, children, academic level, history of COVID-19, COVID-19 symptomatology, close relative with COVID-19, living with vulnerable people and work dedication. In addition, predictive models were constructed considering all possible significant causes. A significance level of p < 0.05 was considered. Dental students and professionals presented significant differences in levels of depression, anxiety and stress (p < 0.001, p = 0.022, p = 0.001; respectively). Male students were 56% less likely to develop stress (OR 0.44; CI 0.22–0.85) compared to females; while those unmarried were 81% less likely to develop stress (OR 0.19; CI 0.04–0.85). Likewise, those with children were 83% less likely to develop stress (OR 0.17; CI 0.06–0.52) and 65% less likely to develop depression (OR 0.35; CI 0.15–0.80). In addition, COVID-19 asymptomatics were 60% less likely to develop depression (OR 0.40; CI 0.17–0.92). However, having relatives with COVID-19 caused almost three times the probability of developing depression (OR 2.96; CI 1.29–6.79) and twice the probability of developing stress (OR 2.49; CI 1.07–5.78). As for dental professionals, it was noticed that those unmarried had almost three times the probability of developing stress (OR 2.93; CI 1.38–6.23); while those who only worked had twice the probability of developing stress (OR 2.37; CI 1.17–4.78). Dental students had a higher prevalence of depression, anxiety and stress. In addition, having children and being asymptomatic were protective predictors for depression, while being male, unmarried and having children were protective predictors for stress. However, having a relative with COVID-19 was a risk predictor for depression and stress. In professionals, only working and being unmarried were risk predictors for stress.