Knowledge about COVID-19 and pandemic impact on Madrid dental students (Spain).

BACKGROUND: COVID-19 has had a major impact on dental activity, with implications on dental education. The aim of this study was to assess the knowledge about it and the pandemic impact on Spanish dental students. MATERIAL AND METHODS: An observational and cross-sectional study with a 17-items questionnaire was conducted. It was divided into three sections, sociodemographic data, self-perception and knowledge about the COVID-19 protective measures and repercussions on dental students. This survey was carried out in May 2020, and the response rate was 46.16%. The statistical analysis was performed by the Pearson chi-square test and Fisher's exact test. RESULTS: A total of 235 students responded to the questionnaire, with an average age of 22.3 years. Attendance at COVID-19 training courses, knowledge about the Personal Protective Equipment (PPE) management and the incubation period had the worst results, compared to the knowledge about hand washing, wearing gloves and masks and symptomatology who got higher percentages. 31.1% of participants reported presenting symptomatology related to SARS-CoV-2, although only 8.2% were diagnosed and 46.6% suffered quarantine. 62.5% were afraid to catch the disease. CONCLUSIONS: The results of this study show that there are deficiencies in the knowledge of important aspects of COVID-19 in dental students, which implies a commitment of the university in its training, as well as the realization of diagnostic controls for the disease. Key words:Dental students, SARS-CoV-2, COVID-19, survey, knowledge.

The role of cortical perforations in allogeneic block grafting for lateral augmentation in maxilla: A randomized clinical trial.

BACKGROUND: The need of decortication on the recipient site remains unclear for bone regeneration. To our knowledge, there are no human clinical trials that studied the influence of decortication on cancellous allogeneic block grafting. PURPOSE: The aim of the present study is to evaluate the influence of perforating the cortex of the recipient site on cancellous allogeneic block graft integration and revascularization in the maxilla. MATERIAL AND METHODS: Twenty-six patients referred for lateral bone augmentation were included in this clinical trial. Patients received freeze-dried bone allograft cancellous blocks obtained from the iliac crest; cortical perforations of the recipient bed were performed in the test group while in the control group it was left intact. After a 4-month healing period another surgery was performed to place dental implants, and a bone biopsy was collected using a trephine. All samples underwent micro-CT scans, and were processed for histomorphometric and immunohistochemical analysis. Implant survival comparisons were made using a repeated measures analysis of variance (ANOVA) while all other variables were compared using the analysis of covariance (ANCOVA). RESULTS: One hundred and nineteen implants were placed into 110 augmented sites. One hundred percent implant survival rate was reported during 24 months follow-up period. No differences were reported in bleeding on probing at 1 (5.6 vs 9%) and 2 years (13.2 vs 12.1%), probing pocket depth at 1 (3.4 ± 0.95 vs 3.6 ± 1.12 mm) and 2 years (3.8 ± 1.02 vs 4.1 ± 1.46 mm), and marginal bone loss at 1 (0.2 ± 0.52 vs 0.3 ± 0.57 mm) and 2 years (0.6 ± 0.91 vs 0.5 ± 0.87 mm). No statistically significant differences were found in the micro-CT and histomorphometric analysis in terms of newly formed bone (25.7 ± 11.2% vs 22.3 ± 9.7%), soft tissue (33.0 ± 14.7% vs 36.5 ± 15.7%), remnant allograft (39.3 ± 20.4% vs 41.2 ± 22.7%), and bone mineralization (57.2 ± 10.6% vs 53.8 ± 8.7%). Perforating the cortex of the recipient site had no significant effect on angiogenesis as shown by immunohistochemical analysis of CD34 positive blood vessels (39.21 ± 10.53/mm2 vs 34.16 ± 12.67/mm2 ). CONCLUSION: Cancellous allogeneic bone block grafts are a clinically acceptable alternative for horizontal bone augmentation. Cortical perforations of the recipient site in the maxilla did not improve angiogenesis nor bone formation within the block graft.

Split bone block technique: 4-month results of a randomised clinical trial comparing clinical and radiographic outcomes between autogenous and xenogeneic cortical plates.

PURPOSE: To evaluate short-term clinical and radiographic outcomes of bone regeneration procedures using thin cortical porcine xenogeneic bone plates in combination with autogenous bone chips compared with thin autogenous cortical plates and autogenous bone chips. MATERIALS AND METHODS: A total of 19 patients (12 women and 7 men, mean age 58.24 ± 3.09 years) were randomly allocated to two different groups regarding surgical procedure: autogenous cortical plates (ACP group) and xenogeneic cortical plates (XCP group). Preoperative CBCT scans were performed for each patient. Surgical time and postoperative pain were recorded, as well as tissue healing and graft resorption after 4 months, then another surgical procedure was performed to place dental implants. Data were analysed using an analysis of covariance. RESULTS: Twenty-one surgical procedures were performed on 19 patients (10 from the XCP group and 9 from the ACP group). The operative time was significantly lower in the XCP group (25.45 ± 3.88 minutes) than in the ACP group (44.10 ± 3.60 minutes). The XCP group also showed less pain, but not significantly less, than the ACP group. The graft resorption rate in the ACP and XCP groups was 2.03 ± 1.58% and 3.49 ± 2.38% respectively, showing no statistically significant difference. CONCLUSIONS: Despite the limited sample size and non-uniform distribution between the maxilla and mandible as surgical sites, the results suggest that XCP and ACP grafts are similar in terms of bone volume gain and graft resorption rate, with no significant differences in wound healing or complication rate. Nevertheless, the XCP group recorded lower pain levels and required significantly less operative time compared to the ACP group.

Growth Hormone As Antiaging Factor in Old Bones.

Aging induces changes in bone. Growth hormone (GH) is reduced by aging, and age-related changes observed in old bones might be due to a decrease in the GH/insulin-like growth factor-I (IGF-I) axis. GH administration on aged individuals is controversial. This study aimed to assess the effect of systemic GH treatment on bone properties, bone metabolism, and bone mineral density (BMD) in long bone of old rats. Aged Wistar rats were treated with GH at a dose of 2 mg/kg/day during 10 weeks. Plasma osteocalcin, IGF-I, and carboxy-terminal telopeptide of type I collagen levels were measured. Cross-sectional bone areas and BMD were measured by morphometric and densitometric analysis, respectively. Femora were analyzed by three point-bending testing. t-Test was used for statistical evaluation. p < 0.05 was considered to be significant. Significantly enhanced bone area, at the expense of the cortical area, was found in treated rats. The densitometric analysis showed 11% higher BMD in the experimental group. Significantly higher bone flexural modulus, stiffness, and ultimate load were observed in the treated rats. Plasma osteocalcin and IGF-I levels were significantly increased in the treated group, while the resorption marker concentration remained unchanged. Within the limitations of this experimental study, systemic GH administration has shown to enhance biomechanical properties, BMD, cortical mass, and plasma IGF-I and osteocalcin in old treated rats, compared to the control group; consequently, GH could be considered as an alternative therapy against age-related changes in the bone.

Local Application of Growth Hormone to Enhance Osseointegration in Osteoporotic Bones: A Morphometric and Densitometric Study.

PURPOSE: The aim of this study was to assess the effect of local application of growth hormone on osseointegration of dental implants inserted in osteoporotic bones. MATERIALS AND METHODS: Twenty female New Zealand rabbits were used in this study. Ten were ovariectomized and fed a low-calcium diet for 6 weeks, and the others remained intact. A titanium implant was inserted into each tibia, in both groups. In half of the rabbits, 2 IU of growth hormone was placed into the ostectomy prior to the implant insertion. Two weeks after implant surgery, all animals were sacrificed. Tibiae were dissected from soft tissues, and included in methacrylate to be studied under light microscopy. Bone-to-implant contact (BIC) and bone mineral density (BMD) were measured by morphometric and densitometric analysis, respectively. Multifactorial analysis of variance (ANOVA) was used for statistical evaluation. P < .05 was considered to be significant. RESULTS: Ovariectomy induced less BIC and BMD in regions closer to the implant compared with the control group. Local application of growth hormone was able to increase the BIC in the ovariectomized group, with statistically significant differences with respect to the control group (P < .01). Regarding the BMD, no statistically significant differences were found. CONCLUSION: Within the limitations of this experimental study, local application of 2 IU of recombinant human growth hormone at the moment of titanium implant insertion in rabbit tibiae significantly enhanced the BIC around titanium implants 15 days after the implantation in this experimental osteoporotic animal model, without affecting the BMD.

Resveratrol as anti-aging therapy for age-related bone loss.

INTRODUCTION: Previous studies have indicated that resveratrol, a natural phytoestrogen, can act as an anti-aging therapy to resist age-related changes of several body tissues. However, the anti-aging effects of resveratrol on bone have been poorly investigated in this natural aging population. Accordingly, this study was design to evaluate the effects of resveratrol on bone mass and biomechanical properties in old rat femora. METHODS: Twenty 22-month-old male Wistar rats were divided into two randomly assigned groups (n=10). The first group was treated for 10 weeks with resveratrol (10 mg/kg per day) and the second group was left untreated (control). Rat femora were collected. Bone mass and bone microestructure were investigated by microcomputed tomography and histomorphometry. Biomechanical properties were determined by a three-point bending test. Plasma levels of CTX (carboxy-terminal telopeptide of type I collagen) and osteocalcin were also determined. Statistical analyses were performed by a Student two-tailed unpaired t-test. In all experiments, a value of p<0.05 was considered significant. RESULTS: Microcomputed tomography analyses demonstrated that resveratrol-treated rats had significant higher bone volume, bone trabecular number, and cortical thickness and lower spacing between trabeculae in comparison to the control group. Histomorphometric analyses confirmed the increase of bone volume in resveratrol-treated rats compared to controls. Resveratrol-treated rats had significant higher bone flexural modulus, stiffness, and ultimate load compared to control group. Treatment was not associated with changes in plasma CTX or osteocalcin. CONCLUSION: These findings demonstrate that resveratrol increases bone microstructure and bone mechanical properties in old male rats, suggesting that resveratrol might be used as anti-aging therapy to resist age-induced bone loss.

Melatonin dietary supplement as an anti-aging therapy for age-related bone loss.

INTRODUCTION: Previous studies have shown that melatonin, an anti-oxidant molecule secreted from the pineal gland, is a positive regulator of bone mass. However, the potential effects of melatonin on bone mass have never been investigated in an old population. The aim of this study was to assess the effects of dietary melatonin supplementation on mass accrual and biomechanical properties of old rat femora. METHODS: Twenty 22-month-old male Wistar rats were divided into two randomly assigned groups. The first group was treated for 10 weeks with melatonin, whereas the second group was untreated (control). Rat femurs were collected, and their phenotypes and biomechanical properties were investigated by micro-computed tomography, histomorphometry, and a three-point-bending test. Statistical analyses were performed by the Student two-tailed unpaired t-test. In all experiments, a value of p<0.05 was considered significant. RESULTS: Rats treated with melatonin had higher bone volume, bone trabecular number, trabecular thickness, and cortical thickness in comparison to the control group. Histomorphometric analyses confirmed the increase of bone volume in melatonin-treated rats. In agreement with these findings, melatonin-treated rats showed higher bone stiffness, flexural modulus, and ultimate load compared to controls. CONCLUSION: These compelling results are the first evidence indicating that dietary melatonin supplementation is able to exert beneficial effects against age-related bone loss in old rats, improving the microstructure and biomechanical properties of aged bones.

Effects of local melatonin application on implant osseointegration.

PURPOSE: The aim of this study was to assess the effect of local melatonin administration on bone osseointegration around implants in rabbit tibiae. MATERIAL AND METHODS: Ten female, 6-month-old New Zealand rabbits were randomly divided into two groups: the experimental group, where five rabbits were treated with local application of melatonin (3 mg) to implant sites when placed into the rabbit tibia, and the control group, those who where without additive materials. Four weeks later, animals were sacrificed; tibiae were dissected from soft tissues and fixed in buffered formaldehyde, and then included in methacrylate. Histological sections were performed to be studied under light microscopy and analyzed morphometrically to evaluate the amount of bone to implant contact (BIC), trabecular area density, and cortical area density. One-way analysis of variance test was used for statistical evaluation. p < .05 was considered to be significant. RESULTS: Histological evaluation showed more trabecular reaction in the melatonin group. Morphometrical analysis showed a statistically significant increase in trabecular BIC in the melatonin group when compared with the control group (24.61% ± 2.87 vs 13.62% ± 1.44; p < .01). Cortical BIC was decreased in the melatonin group, without statistical significance (71.08 ± 3.63 vs 76.28 ± 2.57; p = 0.31). Trabecular area density was increased significantly in the melatonin group (8.68 ± 1.61 vs 4.02 ± 0.36; p < .05). Cortical area density was decreased significantly in the melatonin group (91.31 ± 1.6 vs 95.7 ± 0.5; p < .05). CONCLUSION: Within the limitation of this animal study, local melatonin application at the time of implant placement might induce more trabecular bone at implant contact and higher trabecular area density.

Validation of an osteoporotic animal model for dental implant analyses: an in vivo densitometric study in rabbits.

PURPOSE: The achievement of primary stability in porous and soft bone, where implants are more likely to fail, is one of the unresolved challenges of implant dentistry. Therefore, the aim of the study was to validate an osteoporotic animal model for analysis of poor-quality bone. MATERIALS AND METHODS: Sixteen female New Zealand rabbits, each 6 months old and weighing 4 to 5 kg, were used in this study. The animals were anesthetized, and an in vivo densitometric analysis was performed by dual-energy x-ray absorptiometry (DEXA) to measure bone mineral density (BMD) in the calvaria, cervical spine, and tibia. Ovariectomy was then performed, and animals were fed a low-calcium diet that featured 0.07% calcium, rather than the 0.45% calcium of a standard diet, for 6 weeks. After this period, new densitometric measurements were carried out. Two-way analysis of variance was used for statistical evaluation. A P value of less than .05 was considered to be significant. RESULTS: Together, ovariectomy and a low-calcium diet were able to induce a quick decrease in BMD, as measured at 6 weeks by DEXA. This decrease was statistically significant in the calvaria (P < .001) and the cervical spine (P < .05) but not in the tibia. CONCLUSION: Based upon this study, ovariectomy and a low-calcium diet are able to induce experimental osteoporosis in rabbits in a short period of time.

Actions of melatonin mixed with collagenized porcine bone versus porcine bone only on osteointegration of dental implants.

This study evaluated the effect of the topical application of melatonin mixed with collagenized porcine bone on the osteointegration on the rough discrete calcium deposit (DCD) surface implants in Beagle dogs 3 months after their insertion. In preparation for subsequent insertion of dental implants, lower molars were extracted from 12 Beagle dogs. Each mandible received two parallel wall expanded platform implants with a DCD surface of 4 mm in diameter and 10 mm in length. The implants were randomly assigned to the distal sites on each mandible in the molar area and the gaps were filled with 5 mg lyophilized powdered melatonin and porcine bone and collagenized porcine bone alone. Ten histological sections per implant were obtained for histomorphometric studies. After a 4-wk treatment period, melatonin plus porcine bone significantly increased the perimeter of bone that was in direct contact with the treated implants (P < 0.0001), bone density (P < 0.0001), and new bone formation (P < 0.0001) in comparison with porcine bone alone around the implants. Melatonin plus collagenized porcine bone on DCD surface may act as a biomimetic agent in the placement of endo-osseous dental implants and enhance the osteointegration. Melatonin combined with porcine bone on DCD implants reveals more bone in implant contact at 12 wk (84.5 +/- 1.5%) compared with porcine bone alone treated area (67.17 +/- 1.2%).

Effect of combining platelet-rich plasma with anorganic bovine bone on vertical bone regeneration: early healing assessment in rabbit calvariae.

PURPOSE: The purpose of this study was to evaluate the combination of anorganic bovine bone allograft (ABB) with platelet-rich plasma (PRP) when used in vertical bone augmentation. MATERIALS AND METHODS: Sixteen healthy 6-month-old female New Zealand rabbits were used in this study. Rabbits were randomly divided into two groups of eight animals each. Created calvarial defects were grafted with ABB or PRP in the first group whereas, in the second group, one cylinder was filled with PRP+ABB and the contralateral cylinder was left ungrafted to be filled by autologous blood (control cylinder). Six weeks after intervention, animals were sacrificed and biopsies were taken. Densitometric, histologic, and histomorphometric analyses were performed to evaluate bone mineral density, vertical bone augmentation, and remaining graft volume, respectively. Statistical analyses were performed with the Mann-Whitney test, using a significance level of P < .05. RESULTS: Six weeks after rabbit calvariae were augmented, data analysis revealed that the mixture of PRP and ABB produced twice the vertical bone volume of ABB alone (P < .0001). CONCLUSION: Based upon this study of 16 rabbits, it appears that the combination of ABB with PRP resulted in increased vertical bone augmentation when compared with autologous blood in similarly sized created defects.

Effect of solely applied platelet-rich plasma on osseous regeneration compared to Bio-Oss: a morphometric and densitometric study on rabbit calvaria.

BACKGROUND: The use of platelet-rich plasma (PRP) in bone augmentation procedures is well documented; however, the exact benefit of this material is not yet established. PURPOSE: This study aimed to evaluate the benefits of using PRP, when only used, and compare it to Bio-Oss (Geistlich Biomaterials, Wolhusen, Switzerland) in vertical bone augmentation capacity. MATERIALS AND METHODS: The study was performed in calvaria of eight adult female New Zealand rabbits using titanium bone conduction cylinder. Two titanium cylinders were fixed into perforated slits made on the parietal bone of each rabbit. On each rabbit, one chamber was grafted with Bio-Oss, and the contralateral was filled with PRP. Animals were sacrificed 4 weeks after intervention and biopsies were taken. Densitometric, histological, and histomorphometric analyses were performed to evaluate bone mineral density, vertical bone augmentation, and remaining graft volume, respectively. Statistical analyses were performed with Mann-Whitney test, using a significance level of p < .05. RESULTS: Densitometric and histomorphometric data analysis revealed that mean bone mineral densities and bone augmentation were significantly lower in the cylinders treated with PRP (p < .0001) 4 weeks after implantation. CONCLUSION: This study showed no beneficial effect of using PRP on osseous regeneration. In addition, it was emphasized that Bio-Oss presents good osteoconductive properties by achieving suitable bone volume values.

Influence of titanium surface charge on fibroblast adhesion.

BACKGROUND: Although dental implants have a high success rate, failure owing to the absence of adhesion between the gingival connective tissue and the implant surface is still being reported. PURPOSE: This study was designed to evaluate the effect of a titanium surface charge on fibroblast adhesion. MATERIAL AND METHODS: An electrical chamber was custom-made to generate negative and positive surface charges on commercially pure titanium cylinders with a potential difference of 4.5 V. Twenty-seven titanium cylinders were divided into three experimental groups. In each group, cell attachment to a positively charged titanium cylinder, a negatively charged titanium cylinder, and a titanium cylinder (control) was studied at three time intervals of 15, 30, and 60 minutes. NCTC clone 929 fibroblasts were used in these experiments. The effect of the potential difference in the pH of Dulbecco's Modified Eagle Medium (DMEM) was also evaluated using two new specimens at time intervals of 15, 30, 60, and 80 minutes. RESULTS: The fibroblast cell attachment was more statistically significant to the positively charged titanium cylinder than the negatively charged titanium cylinder (p =.002) and the control (p=.000), whereas the cell adhesion difference between the control and the negatively charged titanium cylinder was not statistically significant (p=.808). The range of pH difference of the DMEM in the negative and positive parts of the electrical chamber was 0.46 and 0.30, respectively. CONCLUSION: Within the limitations of this in vitro study, the positive surface charge of the titanium cylinder results in significantly favorable cell adhesion.

Histologic, morphometric, and densitometric study of peri-implant bone in rabbits with local administration of growth hormone.

PURPOSE: The objective of this study was to evaluate whether the local administration of growth hormone (GH) would influence the formation of peri-implant bone around titanium sheets placed in the tibiae of young rabbits. MATERIALS AND METHODS: Thirty-two New Zealand rabbits were randomly placed in 1 of 2 groups: the experimental group, in which 4 IU (1.2 mg) of lyophilized powder (GH) was added to a surgically created defect at implant placement, or the control group, in which an implant sheet was placed without hormonal treatment. Animals were sacrificed at 1, 2, 3, and 6 weeks after surgery, and histologic sections were stained with Masson, Alcian blue, picrosirius, and hematoxylin-eosin and observed under light microscopy. The sections were analyzed morphometrically and densitometrically to calculate the amount of newly formed bone. RESULTS: At week 2, GH-group sections showed enhanced growth of the trabeculae from the periosteal tissue, with thicker and more irregular trabeculae than those observed in control group specimens. A tendency toward greater bone area and lesser density was observed in the GH group, although the groups did not differ significantly. Nevertheless, bone-to-implant contact in weeks 2 and 6 was significantly greater in the GH group (P < .05). DISCUSSION: An increase in the cortical response from periosteal and endosteal reactions was observed with the high local administration of GH, in disagreement with most authors. In the first phases of bone repair, the osteons were more disorganized; they were more organized by the sixth week. CONCLUSION: Local administration of GH could stimulate the first phases of the bone remodeling process in this experimental model.

Effects of local administration of growth hormone in peri-implant bone: an experimental study with implants in rabbit tibiae.

PURPOSE: The objective of this study was to evaluate the qualitative and quantitative differences that could appear in newly formed peri-implant bone around Screw-Vent implants placed in rabbit tibiae when treated with local administration of growth hormone (GH). MATERIALS AND METHODS: Eight New Zealand rabbits were randomly divided into 2 groups: the experimental group, which received 4 IU of GH in the form of lyophilized powder added to the ostectomy site before implant placement, and the control group, which did not receive GH before implant placement. Animals were sacrificed 2 weeks later, and histologic sections were obtained for histomorphometry and observation under light microscopy. RESULTS: The sections in the GH-treated group presented enhanced growth of new trabeculae from the periosteal tissue, and the bone-to-implant contact in the experimental group was significantly greater (P < .05). DISCUSSION: Local administration of GH stimulated a more dramatic effect than that seen previously with systemic GH administration, prompting growth from both the periosteum and endosteum. CONCLUSIONS: Local administration of GH at the time of implant placement could enhance peri-implant bone reaction.

Local administration of growth hormone enhances periimplant bone reaction in an osteoporotic rabbit model.

OBJECTIVE: The purpose of this study was to determine whether rhGH administered locally during the surgical placement of an implant, in the tibia of an osteoporotic rabbit model, would induce qualitative and quantitative differences in peri-implant bone reaction. MATERIALS AND METHODS: Eight New Zealand rabbits were ovariectomized and fed with a low-calcium diet (with 0.07% of calcium) to induce osteoporosis. After 6 weeks, an experimental titanium sheet was inserted into the rabbit tibiae. The rabbits were randomly divided into two groups. The experimental group was treated with 4 IU of rhGH added locally into the ostectomy as a lyophilized powder and the control group was left without any treatment. After 2 weeks, animals were sacrificed, tibial sections were prepared and bone-titanium interface was examined at light microscopy, using Masson, hematoxylin-eosin and Pichrosirius stains. Light microscopic morphometry and densitometry were used to comparatively quantitate bone reaction. RESULTS/CONCLUSION: Local administration of rhGH during the surgical placement of titanium sheets on the tibiae of an osteoporotic rabbit model enhances periosteal and transcortical reaction and mineralization of osteoid 14 days later around titanium sheets, without increasing bone resorption.