Dental practice closure during the first wave of COVID-19 and associated professional, practice and structural determinants: a multi-country survey.

BACKGROUND: The coronavirus outbreak (COVID-19) in China has influenced every aspect of life worldwide. Given the unique characteristics of the dental setting, the risk of cross-infection between dental practitioners and patients is high in the absence of adequate protective measures, and dentists may develop severe anxiety in relation to the current pandemic. The limited provision of services and widespread closure of dental practices have raised concerns among dental professionals about the financial impact. The present study assessed the frequency of dental practice closure during the pandemic's first wave in several countries and whether closures and their associated factors differ between the private and non-private sectors. METHODS: An electronic cross-sectional survey questionnaire was sent to dentists in several countries, from April to May 2020. The survey assessed professional, practice related and country-level structural factors elucidating the reason for practice closure. Multilevel logistic regression was used to assess the association between practice closure and these factors, and differences were evaluated by sector type. RESULTS: Dentists from 29 countries (n = 3243) participated in this study. Most of the participants (75.9%) reported practice closure with significantly higher percentage in the private sector than the non-private sector. Greater pandemic-related fears were associated with a significantly higher likelihood of practice closure in the private (odds ratio [OR] = 1.54, 95% confidence interval [CI] 1.24, 1.92) and non-private (OR = 1.38, 95% CI 1.04, 1.82) sectors. Dentists in non-private rural areas (OR = 0.58, 95% CI 0.42, 0.81), and those in hospitals (overall OR = 0.60, 95% CI 0.36, 0.99) reported a low likelihood of closure. A high likelihood of closure was reported by dentists in the academia (OR = 2.13, 95% CI 1.23, 3.71). More hospital beds at the country-level were associated with a lower likelihood of closure in the non-private sector (OR = 0.65, 95% CI 0.46, 0.91). Private- sector dentists in high- income countries (HICs) reported fewer closures than those in non-HICs (OR = 0.55, 95% CI 0.15, 1.93). CONCLUSIONS: Most dentists reported practice closure because of COVID-19, and greater impacts were reported in the private sector than in the non-private sector. Closure was associated with professional, practice, and country-levels factors.

Perceived Preparedness of Dental Academic Institutions to Cope with the COVID-19 Pandemic: A Multi-Country Survey.

Dental academic institutions are affected by COVID-19. We assessed the perceived COVID-19 preparedness of these institutions and the characteristics of institutions with greater perceived preparedness. An international cross-sectional survey of dental academics was conducted from March to August 2020 to assess academics' and institutional attributes, perceived preparedness, and availability of infection prevention and control (IPC) equipment. Principal component analysis (PCA) identified perceived preparedness components. Multilevel linear regression analysis assessed the association between perceived preparedness and fixed effect factors (academics' and institutions' attributes) with countries as random effect variable. Of the 1820 dental academics from 28 countries, 78.4% worked in public institutions and 75.2% reported temporary closure. PCA showed five components: clinic apparel, measures before and after patient care, institutional policies, and availability of IPC equipment. Significantly less perceived preparedness was reported in lower-middle income (LMICs) (B = -1.31, p = 0.006) and upper-middle income (UMICs) (B = -0.98, p = 0.02) countries than in high-income countries (HICs), in teaching only (B = -0.55, p < 0.0001) and in research only (B = -1.22, p = 0.003) than teaching and research institutions and in institutions receiving ≤100 patients daily than those receiving >100 patients (B = -0.38, p < 0.0001). More perceived preparedness was reported by academics with administrative roles (B = 0.59, p < 0.0001). Academics from low-income countries (LICs) and LMICs reported less availability of clinic apparel, IPC equipment, measures before patient care, and institutional policies but more measures during patient care. There was greater perceived preparedness in HICs and institutions with greater involvement in teaching, research, and patient care.

Knowledge of dental academics about the COVID-19 pandemic: a multi-country online survey.

BACKGROUND: COVID-19 is a global pandemic affecting all aspects of life in all countries. We assessed COVID-19 knowledge and associated factors among dental academics in 26 countries. METHODS: We invited dental academics to participate in a cross-sectional, multi-country, online survey from March to April 2020. The survey collected data on knowledge of COVID-19 regarding the mode of transmission, symptoms, diagnosis, treatment, protection, and dental treatment precautions as well as participants' background variables. Multilevel linear models were used to assess the association between dental academics' knowledge of COVID-19 and individual level (personal and professional) and country-level (number of COVID-19 cases/ million population) factors accounting for random variation among countries. RESULTS: Two thousand forty-five academics participated in the survey (response rate 14.3%, with 54.7% female and 67% younger than 46 years of age). The mean (SD) knowledge percent score was 73.2 (11.2) %, and the score of knowledge of symptoms was significantly lower than the score of knowledge of diagnostic methods (53.1 and 85.4%, P <  0.0001). Knowledge score was significantly higher among those living with a partner/spouse than among those living alone (regression coefficient (B) = 0.48); higher among those with PhD degrees than among those with Bachelor of Dental Science degrees (B = 0.48); higher among those seeing 21 to 30 patients daily than among those seeing no patients (B = 0.65); and higher among those from countries with a higher number of COVID-19 cases/million population (B = 0.0007). CONCLUSIONS: Dental academics had poorer knowledge of COVID-19 symptoms than of COVID-19 diagnostic methods. Living arrangements, academic degrees, patient load, and magnitude of the epidemic in the country were associated with COVD-19 knowledge among dental academics. Training of dental academics on COVID-19 can be designed using these findings to recruit those with the greatest need.

Behavior change due to COVID-19 among dental academics-The theory of planned behavior: Stresses, worries, training, and pandemic severity.

OBJECTIVE: COVID-19 pandemic led to major life changes. We assessed the psychological impact of COVID-19 on dental academics globally and on changes in their behaviors. METHODS: We invited dental academics to complete a cross-sectional, online survey from March to May 2020. The survey was based on the Theory of Planned Behavior (TPB). The survey collected data on participants' stress levels (using the Impact of Event Scale), attitude (fears, and worries because of COVID-19 extracted by Principal Component Analysis (PCA), perceived control (resulting from training on public health emergencies), norms (country-level COVID-19 fatality rate), and personal and professional backgrounds. We used multilevel regression models to assess the association between the study outcome variables (frequent handwashing and avoidance of crowded places) and explanatory variables (stress, attitude, perceived control and norms). RESULTS: 1862 academics from 28 countries participated in the survey (response rate = 11.3%). Of those, 53.4% were female, 32.9% were <46 years old and 9.9% had severe stress. PCA extracted three main factors: fear of infection, worries because of professional responsibilities, and worries because of restricted mobility. These factors had significant dose-dependent association with stress and were significantly associated with more frequent handwashing by dental academics (B = 0.56, 0.33, and 0.34) and avoiding crowded places (B = 0.55, 0.30, and 0.28). Low country fatality rates were significantly associated with more handwashing (B = -2.82) and avoiding crowded places (B = -6.61). Training on public health emergencies was not significantly associated with behavior change (B = -0.01 and -0.11). CONCLUSIONS: COVID-19 had a considerable psychological impact on dental academics. There was a direct, dose-dependent association between change in behaviors and worries but no association between these changes and training on public health emergencies. More change in behaviors was associated with lower country COVID-19 fatality rates. Fears and stresses were associated with greater adoption of preventive measures against the pandemic.

Use of a gelatin hydrogel membrane containing ß-tricalcium phosphate for guided bone regeneration enhances rapid bone formation.

The purpose of this study was to evaluate a thin gelatin hydrogel membrane containing ß-tricalcium phosphate (G-TCP) for use in guided bone regeneration, a technique that we developed. G-TCP membranes were fabricated from gelatin and ß-TCP powder, freezedried, and cross-linked by heating. The resulting G-TCP membranes were as thin as collagen membranes, with high mechanical integrity. Proliferation and differentiation of rat bone marrow stromal cells (BMSCs) on G-TCP and collagen membranes were examined. On both membranes, BMSCs proliferated well and expressed alkaline phosphatase. However, more bone-like mineralized tissue formed on G-TCP membranes than on collagen membranes at 4 weeks. The effects of G-TCP and collagen membranes on bone regeneration in rat parietal bone defects were histologically examined. Bone bridges with mature uniform bone were observed under G-TCP membranes as early as 2 weeks. These results indicate that G-TCP is a GBR membrane that is comparable or superior to collagen membrane.

Accelerated and enhanced bone formation on novel simvastatin-loaded porous titanium oxide surfaces.

BACKGROUND: With increasing application of dental implants in poor-quality bones, the need for implant surfaces ensuring accelerated osseointegration and enhanced peri-implant bone regeneration is increased. PURPOSE: A study was performed to evaluate the osseointegration and bone formation on novel simvastatin-loaded porous titanium oxide surface. MATERIALS AND METHODS: Titanium screws were treated by micro-arc oxidation to form porous oxide surface and 25 or 50 µg of simvastatin was loaded. The nontreated control, micro-arc oxidized, and simvastatin-loaded titanium screws were surgically implanted into the proximal tibia of 16-week-old male Wistar rats (n = 36). Peri-implant bone volume, bone-implant contact, and mineral apposition rates were measured at 2 and 4 weeks. Data were analyzed by one-way analysis of variance followed by Tukey's post hoc test. RESULTS: New bone was formed directly on the implant surface in the bone marrow cavity in simvastatin-loaded groups since 2 weeks. Bone-implant contact values were significantly higher in simvastatin-loaded groups than control and micro-arc oxidized groups at both time points (p < .05). Peri-implant bone volume and mineral apposition rate of simvastatin-loaded groups were significantly higher than control and micro-arc oxidized groups at 2 weeks (p < .05). CONCLUSIONS: These data suggested that simvastatin-loaded porous titanium oxide surface provides faster osseointegration and peri-implant bone formation and it would be potentially applicable in poor-quality bones.

Feasibility of alpha tricalcium phosphate for vertical bone augmentation.

AIM: Inadequate vertical bone compromises dental implant positioning and subsequent restoration. This study was carried out to investigate the feasibility of alpha tricalcium phosphate (α-TCP) for vertical bone augmentation. METHODS: Nine cortical perforations were made on each side of the parietal bone of rat calvaria under continuous saline coolant. Polytetrafluoroethylene cylinders were placed under the periosteum and α-TCP particles were applied in the cylinders in the TCP group while the cylinders were left empty in the control group. The animals were sacrificed at 4 and 8 weeks after surgery and analyzed radiologically and histologically. RESULTS: The augmented bone volumes in the control and TCP groups were 91.5 ± 25.6% and 76.5 ± 49.8% (mean ± SD) of the original bone at 4 weeks, and 136.3 ± 59.7% and 139 ± 62.4% at 8 weeks respectively. There was no significant difference between control and test groups. At 4 weeks the bone height was augmented by 168.8 ± 26.7% and 128.8 ± 62% in the control and TCP groups respectively (not significant), whereas significantly higher vertical bone was achieved in the TCP group than in the control group at 8 weeks (251 ± 32% vs 179.2 ± 30.3%, P < 0.05). CONCLUSION: After 8 weeks α-TCP is effective in maintaining space under periosteum and potentially would be applicable in vertical bone augmentation.

Exploitation of a novel polysaccharide nanogel cross-linking membrane for guided bone regeneration (GBR).

Cholesterol-bearing pullulan (CHP) nanogel is a synthetic degradable biomaterial for drug delivery with high biocompatibility. Guided bone regeneration (GBR) is a bone augmentation technique in which a membrane is used to create and keep a secluded regenerative space. The purpose of the present study was to evaluate the effects of the novel CHP nanogel membrane in GBR. Thirty-six adult Wistar rats were used and bilaterally symmetrical full-thickness parietal bone defects of 5 mm diameter were created with a bone trephine burr. Each defect was covered with the collagen membrane or the CHP nanogel membrane or untreated without any membrane. The animals were sacrificed at 2, 4 and 8 weeks and analysed radiologically and histologically. Furthermore, after incubating human serum with CHP nanogel or collagen, the amount of PDGF in the serum was measured using ELISA. New bone formation in terms of bone volume was higher in the nanogel group than in the control or collagen groups at 2 and 4 weeks. At 8 weeks, both membrane groups showed higher bone volumes than the control group. Notably, the newly-formed bone in the bone defect in the nanogel group was uniform and histologically indistinguishable from the original bone, whereas in the collagen group the new bone showed an irregular structure that was completely different from the original bone. After incubating with CHP nanogel, the amount of PDGF in the serum decreased significantly. CHP nanogel GBR membrane favourably stimulated bone regeneration, in which a unique characteristic of CHP nanogel, the storage of endogenous growth factors, was likely implicated.

Synthesis of novel oxide layers on titanium by combination of sputter deposition and micro-arc oxidation techniques.

A novel coating technique of thin ceramic layer resembling teeth color on titanium (Ti) surface was developed by combination of sputter deposition of metal zirconium (Zr) and subsequent micro-arc oxidation (MAO) treatment. The oxide layer grown by MAO treatment had a porous structure with a thickness of approximately 6 micrometers and was mainly composed of zirconium dioxide (ZrO(2)) with both tetragonal and monoclinic crystal structures. The surface of the specimen was hardened by this technique, and the hardness of the specimen was significantly larger than that of untreated Ti and MAO-treated Ti without Zr layer. The bonding strength test revealed that fracture occurred inside the oxide layer, indicating that adhesion between the oxide layer and the Ti substrate was sufficiently strong. From these results, this technique has an advantage for the development of novel dental materials with excellent mechanical and aesthetic properties.

Evaluation of the osteoconductivity of α-tricalcium phosphate, ß-tricalcium phosphate, and hydroxyapatite combined with or without simvastatin in rat calvarial defect.

The purpose of this study is to evaluate the osteoconductivity of three different bone substitute materials: α-tricalcium phosphate (α-TCP), (ß-TCP), and hydroxyapatite (HA), combined with or without simvastatin, which is a cholesterol synthesis inhibitor stimulating BMP-2 expression in osteoblasts. We used 72 Wistar rats and prepared two calvarial bone defects of 5 mm diameter in each rat. Defects were filled with the particles of 500-750 µm diameter combined with or without simvastatin at 0.1 mg dose for each defect. In the control group, defects were left empty. Animals were divided into seven groups: α-TCP, ß-TCP, HA, α-TCP with simvastatin, ß-TCP with simvastatin, HA with simvastatin, and control. The animals were sacrificed at 6 and 8 weeks. The calvariae were dissected out and analyzed with micro CT. The specimens were evaluated histologically and histomorphometrically. In α-TCP group, the amount of newly formed bone was significantly more than both HA and control groups but not significantly yet more than ß-TCP group. Degradation of α-TCP was prominent and ß-TCP showed slower rate while HA showed the least degradation. Combining the materials with Simvastatin led to increasing in the amount of newly formed bone. These results confirmed that α-TCP, ß-TCP, and HA are osteoconductive materials acting as space maintainer for bone formation and that combining these materials with simvastatin stimulates bone regeneration and it also affects degradability of α-TCP and ß-TCP. Conclusively, α-TCP has the advantage of higher rate of degradation allowing the more bone formation and combining α-TCP with simvastatin enhances this property.

Implantation of green tea catechin α-tricalcium phosphate combination enhances bone repair in rat skull defects.

UNLABELLED: The purpose of the present study is to investigate effects of the combination of epigallocatechin-3-gallate (EGCG) and α-tricalcium phosphate (α-TCP) on bone regenerative capacity in a bilateral rat calvarial bone defect model. MATERIALS AND METHODS: Bilateral 5-mm-diameter calvarial defects were created in adult male Wistar rats and filled with preparations of EGCG (0, 0.1, 0.2, 0.4 mg) combined with α-TCP particles. This was done by dissolving EGCG in 100% ethanol (50 µL/14 mg) and dropping under sterile condition. The control group was left unfilled (n = 8). The animals were sacrificed at 2 and 4 weeks. Radiological images were taken, and histological analysis was done. Six animals from control (0 mg EGCG + α-TCP) group and (0.2 mg EGCG+ α-TCP) group were labeled with fluorescent dyes and histomorphometrically analyzed (n = 6) at 2 and 4 weeks. RESULTS: Histomorphometric analysis revealed that the combination of EGCG and α-TCP at doses of 0.1 and 0.2 mg yielded significantly more new bone formation than untreated control group at 2 and 4 weeks (p > 0.05). Mineral apposition rate at 0.2-TCP group was enhanced compared with the one of the positive control α-TCP group at 4 weeks (p > 0.05). CONCLUSION: The combination of α-TCP particles and 0.2 mg EGCG stimulates maximum bone regeneration in rat calvarial defects, and this combination would be potentially effective as bone graft material.

Molecular and tissue responses in the healing of rat calvarial defects after local application of simvastatin combined with alpha tricalcium phosphate.

We have previously reported that healing of rat calvarial defects was enhanced by application of alpha tricalcium phosphate (alphaTCP) combined with simvastatin, a cholesterol synthesis inhibitor. The purpose of the present study was to investigate the cellular and molecular mechanisms in this phenomenon. Rat calvarial defects were grafted with alphaTCP with or without simvastatin or left untreated. Animals were sacrificed on 3, 7, 10, 14, and 21 days postoperatively and histological changes in the defect region were assessed. Gene expression patterns were examined by RT-PCR. Proliferation and migration of osteoprogenitor cells from the dura mater were increased in simvastatin group from day 3 to day 10 (p < 0.01). New bone formation was significantly increased in simvastatin group on day 14 and day 21 (p < 0.01). BMP-2 expression was significantly higher in simvastatin group on day 3 and day 14 (p < 0.05) and maintained until day 21. Increased upregulation of TGF-beta1 was also observed in the simvastatin group on day 7 (p < 0.05) which was maintained until day 14. These findings suggest that the proliferation and recruitment of osteoprogenitor cells were critical steps in early stage of bone healing and that these steps were enhanced by TGF-beta1 and BMP-2, which were stimulated by simvastatin.

Effects of the combination with alpha-tricalcium phosphate and simvastatin on bone regeneration.

BACKGROUND: Although local application of statins stimulates bone formation, high dose of simvastatin induces inflammation. OBJECTIVE: A study was conducted to test the hypothesis that maximum bone regeneration with less inflammation would be achieved by combining an optimal dose of simvastatin with alpha-tricalcium phosphate (alpha-TCP), which is an osteoconductive biomaterial capable of releasing the drug gradually. MATERIAL AND METHODS: Bilateral 5-mm-diameter calvarial defects were created in adult Wistar rats and filled with preparations of different doses of simvastatin (0, 0.01, 0.1, 0.25 and 0.5 mg) combined with alpha-TCP particles or left empty. The animals were sacrificed at 2, 4 and 8 weeks and analyzed radiologically and histologically. Half of the animals of 4 and 8 weeks were labeled with fluorescence dyes and histomorphometrically analyzed. RESULTS: Simvastatin doses of 0.25 and 0.5 mg caused inflammation of the soft tissue at the graft site whereas control and other doses did not. The micro-CT analysis revealed that the alpha-TCP with 0.1 mg simvastatin (TCP-0.1) group yielded significantly higher bone volumes than untreated control group at all three time points (249%, 227% and 266% at 2, 4 and 8 weeks, respectively). The percentage of defect closure, bone mineral content and bone mineral density were also higher in the TCP-0.1 group than in the other groups. CONCLUSION: When combined with alpha-TCP particles, 0.1 mg simvastatin is the optimal dose for stimulation of the maximum bone regeneration in rat calvarial defects without inducing inflammation and it could be applied as an effective bone graft material.

Bone formation with the combination of simvastatin and calcium sulfate in critical-sized rat calvarial defect.

Simvastatin, a cholesterol synthesis inhibitor, enhances BMP2 expression in osteoblasts. The purpose of the present study was to examine whether simvastatin stimulates bone regeneration when combined with calcium sulfate as a carrier. Critical-sized bone defects in rat calvaria were treated with calcium sulfate or with combination of 1 mg simvastatin and calcium sulfate. In the combination group, although the least amount of bone formation with intense soft tissue inflammation was observed at 2 and 4 weeks, remarkable bone formation was evident at 8 weeks. Conclusively, the combination of simvastatin and calcium sulfate stimulated bone regeneration in spite of the inflammatory response.