ObjectivesEven though several effective vaccines are available to combat the COVID-19 pandemic, wide disparities in vaccine distribution, and vaccine acceptance rates between high- and low-income countries appear to be major threats toward achieving population immunity. Our global descriptive study aims to inform policymakers on factors affecting COVID-19 vaccine acceptance among healthcare workers (HCWs) in 12 countries, based on income index. We also looked for possible predictors of vaccine acceptance among the study sample.MethodsA structured questionnaire prepared after consultation with experts in the field and guided by the “Report of the SAGE working group on vaccine hesitancy” was administered among 2,953 HCWs. Upon obtaining informed consent, apart from demographic information, we collected information on trust in vaccines and health authorities, and agreement to accept a COVID-19 vaccine.ResultsAlthough 69% of the participants agreed to accept a vaccine, there was high heterogeneity in agreement between HCWs in low and lower-middle income countries (L-LMICs) and upper-middle- and high-income countries (UM-HICs), with acceptance rates of 62 and 75%, respectively. Potential predictors of vaccine acceptance included being male, 50 years of age or older, resident of an UM-HIC, updating self about COVID-19 vaccines, greater disease severity perception, greater anxiety of contracting COVID-19 and concern about side effects of vaccines.ConclusionsCOVID-19 vaccine acceptance among HCWs in L-LMICs was considerably low as compared to those from UM-HICs. The lowest vaccine acceptance rates were among HCWs from the African continent. This underlines the need for the implementation of country-specific vaccine promotion strategies, with special focus on increasing vaccine supply in L-LMICs.

Objective The aim of this study was to investigate the effect of the hybrid abutment with different angles (0 and 15 degrees) on the stress distribution and deformation on maxillary implant-supported fixed prosthesis, using digital image correlation (DIC) and finite element analysis (FEA). Materials and Methods For DIC, two situations were considered: conventional straight implant placement and implant placement with 15 degrees inclination. Different zirconia mesostructures were milled, one straight and the other with a 15-degree angulation to correct the implant positioning. Then, the zirconia mesostructures were cemented to the titanium base (Ti base), and both groups received a lithium disilicate crown. The DIC technique was performed to measure the deformation generated on the simulated bone surface (150 N loading). For the FEA (in silico), three-dimensional numerical models based on the in vitro setup were modeled using computer-aided design software. All materials were considered elastic, isotropic, and homogeneous. Comparison of both methods showed coherence between the in vitro and in silico results. The von-Mises stress of the implants, Ti base and screw, and the maximum principal stress in the mesostructure and crown were calculated for both conditions. Results The overall surface deformation distributions determined by both techniques were considered similar allowing the model validation. The higher deformation was found in the cervical region with a higher magnitude for the angled hybrid abutment. The same pattern was observed in the stress fields regardless of the analyzed region and structure. Conclusion Based on this study, using an angled hybrid abutment to correct the implant positioning generated higher stress in the implant fixture, surrounding tissue, Ti base, screw, and crown. Therefore, the implant should be positioned axially, whenever possible, to reduce the mechanical complications.

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The objective of this study was to analyze the effect of cement thickness on the strain and stresses resulting from the polymerization of resin cement using photoelasticity and Finite Element Analysis (FEA). For this study, twenty upper first premolars with inlay cavity preparation were constructed from photoelastic resin and restored with composite resin inlay. The samples were divided into two groups (n = 10) according to the film thickness of resin cement material. For Group 1, the film thickness was 100 μm; for Group 2, the film thickness was 400 μm. After polymerization of the cement, photoelastic analysis and finite element analysis (FEA) were performed. In the photoelastic analysis, Group 2 showed higher strain with the presence of second-order fringe even after 24 h. In Group 1, the formation of first order fringes was not observed, even after 24 h. In the FEA analysis, the greatest cusp deflection and tensile stress occurred in Group 2 (0.00026 mm and 0.305 MPa, respectively) due to the polymerization shrinkage in the lingual cusp compared to Group 1 (0.000107 mm and 0.210 MPa, respectively). It can be concluded that the thickness of the resin cement influences the cusp deflection, with the greater thickness of the cement layer, the greater stresses and deformations in the tooth structure occur.

Purpose: This study sought to investigate the acceptance rate and associated factors of COVID-19 vaccines among dentists and dental students in seven countries. Material and Methods: A structured questionnaire prepared and guided by the report of the SAGE Working Group on Vaccine Hesitancy was distributed among groups of dentists and dental students in seven countries across four continents. Results: A total of 1527 subjects (850 dentists and 677 dental students) participated in this survey. Although 72.5% of the respondents reported their intention to accept COVID-19 vaccines (dentists: 74.4%, dental students: 70.2%), there was a significant difference in agreement between dentists/dental students across countries; generally, respondents in upper-middle-, and high-income countries (UM-HICs) showed significantly higher acceptance rates compared to those in low- and lower-middle income countries (L-LMICs). Potential predictors of higher vaccine acceptance included being a dentist, being free of comorbidity, being well-informed about COVID-19 vaccines, having better knowledge about COVID-19 complications, having anxiety about COVID-19 infection, having no concerns about the side effects of the produced vaccines and being a resident of an UM-HIC. Conclusion: The results of our survey indicate a relatively good acceptance rate of COVID-19 among the surveyed dentists and dental students. However, dentists and dental students in L-LMICs showed significantly lower vaccine acceptance rates and trust in COVID-19 vaccines compared to their counterparts in UM-HICs. Our results provide important information to policymakers, highlighting the need for implementation of country-specific vaccine promotion strategies, with special focus on L-LMICs.