Dental Students' Experiences during the COVID-19 Pandemic-A Cross-Sectional Study from Norway.

The purpose of this cross-sectional study was to map dental students' experience of the study situation throughout the pandemic. All clinical dental students (year 3 to 5) at the Faculty of Medicine, Department of Clinical Dentistry (IKO), University of Bergen (UiB), Norway, were invited. Participation was anonymous and voluntary, and the response rate was 63%. Questions regarding stress-related factors were divided into three categories. In the category «Stressors/learning¼, a statistically significant difference was observed between both the genders (p = 0.001) and years of study (p = 0.028). Statistically significant differences between the genders were also observed in the category «Stressors/infection¼ (p = 0.008). Women were significantly more stressed due to lack of clinical skills (p = 0.048), not receiving as good theoretical teaching as before the pandemic (p = 0.016), and uncertain issues around the exams (p = 0.000). Fourth year students were significantly more stressed due to lack of clinical skills (p = 0.012), for not passing the clinic/skills courses due to lack of study progression (p = 0.005), and worries about not being a good enough dentist after graduation (p = 0.002). In conclusion, the pandemic had a major impact on dental students. The most prominent stressors in relation to the study situation were experienced by students from the fourth year and female students. Clinical and theoretical learning outcomes among students were regarded as worse than before the pandemic. The students preferred in presence lectures, but experienced digital asynchronous video lectures as a good alternative. The pandemic negatively affected the students' social life. Dental schools should be aware that students have been exposed to increased distress and burden through the pandemic and should provide support for those in need.

Effect of saliva contamination on the bond strength of single-step and three-step adhesive systems.

The aim of this study was to evaluate the effect of saliva contamination on bond strength to dentin with an etch-and-rinse and a self-etch adhesive system. For each of these adhesive systems, the dentin surface of 24 human molars were allocated to one of four groups representing different saliva contamination scenarios. Saliva was applied at different stages in the bonding process, and was investigated to be remedied by water rinsing and/or air drying. Uncontaminated tooth surfaces were used as controls. Bonding procedures were performed according to the manufacturer's instructions, and a polymer-based composite was placed. The bond strength was measured by a micro-tensile test. Except for the etch-and-rinse approach having contamination with saliva after etching, followed by air drying, all salivary contamination regimens resulted in a substantial number of specimens not surviving the test, and the bond strength value of these was therefore set to 0 MPa for the purposes of the statistical analysis. Water rinsing after etching and salivary contamination did significantly reduce the bond strength. Contamination after priming showed the lowest bond strength. For the self-etch approach, saliva contamination before the adhesive procedure, followed by air drying, significantly reduced the bond strength, while contamination followed by water rinsing or air drying did not statistically significantly reduce the strength.

Influence of the coronal restoration on the outcome of endodontically treated teeth.

Objective: The tooth weakens due to removal of hard tissue during an endodontic procedure. Many dentists find it difficult to choose between different coronal restorations after root canal treatment (RCT). Studies show that the coronal restoration may affect the endodontic prognosis. This student-based study had three aims. (1) Examine the choice of coronal restoration of endodontically treated teeth at a Scandinavian dental school, (2) examine the survival of these restorations and (3) evaluate the influence of the coronal restoration on the outcome of the RCT. Material and methods: Radiographic and clinical examination was performed on 127 posterior teeth. The quality of the root canal treatment and the periapical status (PAI-index) were evaluated. Results: 43.8% of the teeth were restored with an indirect coronal restoration and 47.2% with a direct coronal restoration. The period from finished root canal treatment until placement of a permanent coronal restoration was significantly longer for an indirect restoration than a direct restoration. The teeth treated with a PAI score of 1 and 2 following pulpectomy, necrotic pulp treatment and endodontic retreatment was 93.8%, 82.6% and 69.4%, respectively.Conclusion: There was no significant association between choice of coronal restoration and PAI-score.

Extensive composite molar restorations: 3 years clinical evaluation.

Abstract Objective. To evaluate the clinical performance of extensive direct composite restorations in molars after 1 and 3 years and to find out the importance of extent of the restorations and other factors related to their performance. Materials and methods. Seventy-four patients with a molar tooth in need of a restoration covering at least three surfaces and one cusp were selected. Patient-related factors were registered and the tooth was prepared and restored by using a nano-filled composite. A topographic system for classification of extensive posterior restorations was developed. At baseline, the operator recorded a clinical evaluation, using modified USPHS-criteria. After 1 and 3 years, an independent observer evaluated the restorations. Post-operative problems arising during the observation period were registered. Results. A change in clinical score from baseline to the 1 and 3 year recall was recorded for all clinical criteria. A total of nine restorations were graded as unacceptable after 3 years (3-year survival rate of 87.7% and a mean annual failure rate of 4.2%). Except for gender (p = 0.022), none of the patient-related factors investigated (age, caries risk, extension of the restoration and presence of cervical enamel) had a significant influence on the survival of the restorations. Conclusions. Extensive direct posterior composite restorations showed an acceptable clinical performance after 3 years. Men had a significantly greater restoration failure rate than women.

Class II composite restorations: importance of cervical enamel in vitro.

OBJECTIVE: This study evaluated the importance of enamel at the cervical margin for support and retention of a class II composite restoration in relation to fracture strength, fracture mode, and leakage. METHODS: Sixty-five newly extracted teeth were randomly divided into five groups. Within each group, standardized class II preparations were made at the mesial surface of the tooth with four different preparation designs. Group D (n=15) had the cervical margin placed below the cemento-enamel junction (the dentin group), and in the other three groups (the enamel groups: E1, E2, and E3), the cervical margin was within the enamel (n=15 each). Group E3 had restorations with cuspal coverage, while groups E1 and E2 differed in vertical dimension. Intact teeth without preparation or restoration were tested as controls (n=5). The area of the horizontal part of enamel at the cervical margin of the preparation (available cervical enamel) was calculated. The teeth were restored with a nanofilled composite material and an etch-and-rinse adhesive system. The teeth were subjected to artificial aging consisting of thermocycling and mechanical cyclical loading. The restorations were subsequently loaded until fracture. The teeth were examined microscopically to assess fracture mode and leakage at the interface between the restoration and the tooth substance. RESULTS: The fracture strength in group D (without cervical enamel) and E3 (with cuspal coverage and cervical enamel) was lower (p<0.01) than in the other two groups (with cervical enamel). There was a correlation between the area of available cervical enamel and fracture strength (p<0.01). The median fracture strength for the control teeth was not significantly different from groups E1 and E2. Group D exhibited a predominance of adhesive fractures, while the other groups revealed more cohesive fractures. CONCLUSION: The results from this study indicate that available cervical enamel has an impact on the performance of class II composite restorations.

Mercury in human brain, blood, muscle and toenails in relation to exposure: an autopsy study.

BACKGROUND: The main forms of mercury (Hg) exposure in the general population are methylmercury (MeHg) from seafood, inorganic mercury (I-Hg) from food, and mercury vapor (Hg0) from dental amalgam restorations. While the distribution of MeHg in the body is described by a one compartment model, the distribution of I-Hg after exposure to elemental mercury is more complex, and there is no biomarker for I-Hg in the brain. The aim of this study was to elucidate the relationships between on the one hand MeHg and I-Hg in human brain and other tissues, including blood, and on the other Hg exposure via dental amalgam in a fish-eating population. In addition, the use of blood and toenails as biological indicator media for inorganic and organic mercury (MeHg) in the tissues was evaluated. METHODS: Samples of blood, brain (occipital lobe cortex), pituitary, thyroid, abdominal muscle and toenails were collected at autopsy of 30 deceased individuals, age from 47 to 91 years of age. Concentrations of total-Hg and I-Hg in blood and brain cortex were determined by cold vapor atomic fluorescence spectrometry and total-Hg in other tissues by sector field inductively coupled plasma-mass spectrometry (ICP-SFMS). RESULTS: The median concentrations of MeHg (total-Hg minus I-Hg) and I-Hg in blood were 2.2 and 1.0 microg/L, and in occipital lobe cortex 4 and 5 microg/kg, respectively. There was a significant correlation between MeHg in blood and occipital cortex. Also, total-Hg in toenails correlated with MeHg in both blood and occipital lobe. I-Hg in both blood and occipital cortex, as well as total-Hg in pituitary and thyroid were strongly associated with the number of dental amalgam surfaces at the time of death. CONCLUSION: In a fish-eating population, intake of MeHg via the diet has a marked impact on the MeHg concentration in the brain, while exposure to dental amalgam restorations increases the I-Hg concentrations in the brain. Discrimination between mercury species is necessary to evaluate the impact on Hg in the brain of various sources of exposure, in particular, dental amalgam exposure.