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Boron is reported to cause fertility disorders in birds. We investigated the potential adverse effects of boric acid administered during embryogenesis on testicular development and spermatogenesis after hatching and puberty. The fertilized eggs were divided into four groups. Three groups were injected with different concentrations of boric acid (1000, 1500, or 2000 ppm) dissolved in 9% NaCl into the egg yolk, and the control group received only a 9% NaCl injection. The evaluations were conducted at two time points: post-hatching day 1 and 26 weeks of age. Testes of oneday-old- and 26-week-old birds were subjected to morphological and stereological evaluations to assess the potential effects of boric acid on testicular development. Effects of boric acid on spermatogenesis and semen quality parameters were also investigated in 26-week-old birds. Finally, plasma FSH, LH, and testosterone levels were analyzed in all birds. No statistically significant differences were noted between one-day-old chicks and 26-week-old birds regarding stereological parameters. Likewise, no significant differences were detected among groups concerning Sertoli, germ, and Leydig cells. Semen quality parameters did not reveal statistically significant differences, and similarly, plasma LH and testosterone levels did not statistically differ between the study and the control groups. Comb height and plasma FSH levels were increased in experimental groups, compared to the control in 26-week-old birds. A single administration of different boric acid doses did not impact the testicular morphological features after hatching and puberty. In-ovo boric acid exposure quantitatively altered the numbers of the Sertoli, germ, and Leydig cells, respectively, but revealed no adverse effect on spermatogenesis. This study might contribute to further research targeting boric acid's multifaceted effects on the dynamics of spermatogenesis. [ABSTRACT FROM AUTHOR]

Large-scale epidemics of arboviruses, such as dengue, have heightened societal awareness regarding the necessity of combating the primary transmission vectors. Equally critical is the identification of environmental conditions and variables that influence vector population dynamics. Aedes aegypti , the primary vector of arboviruses such as dengue and Zika in Brazil, is closely associated with the climatic and geographical conditions of urban environments. This study examines the relationship between precipitation and confirmed dengue cases in Recife (Brazil), employing regression and quantile analyses to evaluate the influence of meteorological conditions on the disease's spread. The findings reveal a direct correlation between monthly averages of precipitation and confirmed cases, although this is apparent only when excluding years of epidemic peaks. The highest number of cases generally aligns with the rainy season, and the lowest with the dry season, with weak, moderate and strong precipitation events being closely linked to increased dengue incidence. However, notable discrepancies were identified: four out of six major outbreaks occurred in drier months, challenging the assumption of a straightforward relationship between rainfall and dengue incidence. These findings underscore the multifaceted nature of dengue dynamics, suggesting that while precipitation plays a significant role, other factors, including serotype circulation and broader climatic phenomena, are equally critical in driving outbreaks. This complexity highlights the need for a more comprehensive understanding of the mechanisms influencing dengue epidemics., Competing Interests: The authors have no relevant financial conflicts of interest. However, it should be noted that Tiago Massoni, Patty Kostkova, Tercio Ambrizzi, and Anwar Musah are members of the Editorial Board of Vector-Borne Diseases -- The Digital One Health Approach. Due to this affiliation, the manuscript has been managed by other editorial members. These author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Borges, Musah, Dutra, Tunali, Lima, Tunali, da Silva, Aldosery, Moreno, dos Santos, Massoni, Yenigün, Kostkova, da Rocha, Campos and Ambrizzi.)

Objectives: The aim of the study was to evaluate the effect of injectable platelet-rich fibrin (i-PRF) on gingival thickness and gingival recession in individuals with thin periodontal phenotypes., Method and Materials: In this prospective study, i-PRF was applied via a semisurgical method to augment 53 tooth regions with thin periodontal phenotypes. In order to ensure that sufficient blood clot formed on the side of the gingiva facing the bone and that i-PRF reached the area, a minimal incision was made with the help of a scalpel in the apical region of the relevant region, and the periosteum was elevated with a microsurgical instrument. To ensure sustained exposure to angiogenetic growth factors and enhance the histoconductive properties, i-PRF injection was applied to the relevant areas in four sessions at 10-day intervals., Results: An increase in gingival thickness was achieved in 92.5% of the areas treated with i-PRF, and the desired gingival thickness (0.8 mm) was achieved in 44.9% of these areas. In addition, significant reductions in the amount of recession were observed in 83.3% of the 12 gingival recession areas (P = .005). Moreover, complete coverage was achieved in 60% of these regions., Conclusion: With the new i-PRF semisurgical method, it was shown that gingival thickness can be increased in tooth regions with thin gingiva, and that areas of gingival recession can be covered. Further comprehensive studies are needed to fully understand the role of i-PRF in enhancing angiogenesis and the histoconductive properties of this fully autogenous blood concentrate.

Objectives: Titanium platelet-rich fibrin (T-PRF), a second-generation autogenous blood concentrate with tough and thick fibrin meshwork activated by a titanium tube, was used as a drug carrier for doxycycline (Doxy) by injection. The objective of this study is to evaluate the loading capacity of T-PRF, release kinetics of doxycycline-loaded T-PRF, and its antibacterial effects against S. aureus and P. aeruginosa., Materials and Methods: The T-PRF and collagen were loaded with Doxy as T-PRF/Doxy and Collagen/Doxy, and their release and antibacterial activities against S. aureus and P. aeruginosa were investigated. Chemical characterization and morphological analysis were performed., Results: In comparison with collagen, approximately sevenfold more Doxy, 281 mg/g, was loaded into T-PRF. It was found that 25% of the loaded Doxy was released from T-PRF compared to only 12% from collagen within 72 h. The largest inhibition zone diameter (IZD) was observed for T-PRF/Dox with 32 ± 6 mm and 37 ± 5 mm for P. aereginosa and S. aureus, respectively. However, only 10 ± 5 mm and 10 ± 6 mm IZD were observed for bare T-PRF, and no inhibition zone was observed for the Collagen/Doxy group. A dense fibrin structure was visualized on SEM images of the T-PRF/Doxy group compared to the T-PRF group., Conclusions: T-PRF has higher Doxy loading capacity and long-acting antibacterial effects compared to collagen. T-PRF was shown to have potential autogenous long-term drug-carrying capability for doxycycline. Also, the potential fibrinophilic properties of Doxy were observed to strengthen the structure of T-PRF., Clinical Relevance: T-PRF is an autogenous drug career with high loading capacity and extended antibacterial effects for doxycycline. Doxycycline molecules can be visible on T-PRF fibers. This study suggests that T-PRF/Dox could be used as a proper antibiotic delivery device in the treatments of periodontitis and peri-implantitis., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Arboviruses are a group of diseases that are transmitted by an arthropod vector. Since they are part of the Neglected Tropical Diseases that pose several public health challenges for countries around the world. The arboviruses' dynamics are governed by a combination of climatic, environmental, and human mobility factors. Arboviruses prediction models can be a support tool for decision-making by public health agents. In this study, we propose a systematic literature review to identify arboviruses prediction models, as well as models for their transmitter vector dynamics. To carry out this review, we searched reputable scientific bases such as IEE Xplore, PubMed, Science Direct, Springer Link, and Scopus. We search for studies published between the years 2015 and 2020, using a search string. A total of 429 articles were returned, however, after filtering by exclusion and inclusion criteria, 139 were included. Through this systematic review, it was possible to identify the challenges present in the construction of arboviruses prediction models, as well as the existing gap in the construction of spatiotemporal models., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lima, da Silva, Moreno, Cordeiro da Silva, Musah, Aldosery, Dutra, Ambrizzi, Borges, Tunali, Basibuyuk, Yenigün, Massoni, Browning, Jones, Campos, Kostkova, Silva Filho and dos Santos.)

Purpose: To investigate the effect of platelet-rich fibrin (PRF) on post-operative wound healing following strabismus surgery in a rabbit model., Methods: Nine New Zealand white rabbits were involved in the study. One of these nine rabbits was kept in control without having any operation. Both eyes of eight rabbits underwent superior rectus muscle (SRM) resection. After resection of SRM, PRF was applied to SRM of the right eyes. In the left eye, SRM was not wrapped with PRF and served as a control. The rabbits were sacrificed and enucleated 6 weeks after the surgery. Inflammation and vascular proliferation were assessed by staining with haematoxylin-eosin. Scar and fibrosis were examined by the Masson trichrome staining. Immunohistochemical staining was performed for a vascular endothelial growth factor (VEGF) and alpha-smooth muscle actin (α-SMA)., Results: There was no significant difference in terms of inflammation ( p  = 0.535), vascularization ( p  = 0.602), and fibrosis ( p  = 0.745) between the eyes. Immunohistochemical staining for VEGF demonstrated no significant difference ( p  = 0.745). However, significant staining for α-SMA was detected in PRF-treated eyes compared with control eyes ( p  = 0.037)., Conclusion: Consistent with the hypothesis that PRF facilitates wound healing as a biocatalyst, there was only a significant difference for α-SMA related to myofibroblast activity which is important for wound remodelling. Future comprehensive studies are needed to extend these results.

Objective: Our study compared the effects of injectable platelet-rich fibrin (i-PRF) with those of corticosteroids in the treatment of erosive oral lichen planus (EOLP)., Methodology: This split-mouth study included 24 individuals diagnosed histopathologically with bilateral EOLP. One bilateral lesion was injected with i-PRF, whereas the other was injected with methylprednisolone acetate in four sessions at 15-day intervals. Visual analog scale (VAS) for pain and satisfaction, oral health impact profile scale-14, and the lesion size were used., Results: The intragroup comparisons showed a significant decrease in VAS-pain and lesion size in both the i-PRF group (from 81.88±17.74 to 13.33±18.34, and from 4.79±0.41 to 1.88±1.08, respectively) and the corticosteroid group (from 80.21±17.35 to 23.33±26.81, and from 4.71±0.46 to 2.21±1.35, respectively) in the 6th month compared to baseline (p<0.001). Moreover, VAS-satisfaction increased significantly in both the i-PRF group (from 26.67±17.8 to 85.63±16.24) and the corticosteroid group (from 28.33±17.05 to 74.38±24.11) in the 6th month compared to baseline (p<0.001). However, no significant difference in any value occurred in the intergroup comparisons., Conclusion: In patients with EOLP, both methods decreased pain and lesion size similarly, and both increased satisfaction. Therefore, the use of i-PRF may be considered an option in cases refractory to topical corticosteroid therapy. Biochemical and histopathological studies are required to reveal the mechanism of i-PRF action in EOLP treatment.

This paper explores the main factors for mosquito-borne transmission of the Zika virus by focusing on environmental, anthropogenic, and social risks. A literature review was conducted bringing together related information from this genre of research from peer-reviewed publications. It was observed that environmental conditions, especially precipitation, humidity, and temperature, played a role in the transmission. Furthermore, anthropogenic factors including sanitation, urbanization, and environmental pollution promote the transmission by affecting the mosquito density. In addition, socioeconomic factors such as poverty as well as social inequality and low-quality housing have also an impact since these are social factors that limit access to certain facilities or infrastructure which, in turn, promote transmission when absent (e.g., piped water and screened windows). Finally, the paper presents short-, mid-, and long-term preventative solutions together with future perspectives. This is the first review exploring the effects of anthropogenic aspects on Zika transmission with a special emphasis in Brazil., (© 2021. The Author(s).)

Microplastic pollution has become a global problem and it is threatening soil and water bodies around the world. In this study, i) the sole effect of 0.5 μm sized polystyrene microplastics under different concentrations (1, 5, 50, 100, and 1000 mg/L) and ii) the combined effect of the microplastic-metal combination (Cu, Zn, Mn) were investigated on the growth and chlorophyll a content of the freshwater microalgae; Chlorella vulgaris. Results showed that lower concentrations of microplastics (1, 5 mg/L) had no impact while higher concentrations (50, 100, 1000 mg/L) significantly reduced growth and chlorophyll a content of Chlorella vulgaris. Highest inhibition ratios were found between 15.71 and 28.86% on growth and 9.2-21.3% on chlorophyll a concentration for 50-1000 mg/L of microplastic. Microplastic-metal combinations showed greater inhibition on growth and chlorophyll a concentration. It has been shown that single metal-microplastic combinations reduced growth by 47.83-49.57% and chlorophyll a concentration by 44.75-50.25%. However, a much higher impact was observed for the triple metal-microplastic combination by 70.43% and 64.09% on growth and chlorophyll a content, respectively. SEM images provided insight into the probable cause of the toxic effect as the microplastic particles were adsorbed and embedded on the algal cell. Negative effects were observed generally at the early stages of exposure and weakened over time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The aim of this study was to test the nano-hydroxyapatite powder decontamination method on intraorally contaminated titanium discs and to compare this method with current decontamination methods in the treatment of peri-implantitis. Contaminated discs were assigned to six treatment groups (n = 10 each): titanium hand curette; ultrasonic scaler with a plastic tip (appropriate for titanium); ultrasonic scaler with a plastic tip (appropriate for titanium) + H 2 O 2 ; short-term airflow system (nano-hydroxyapatite airborne-particle abrasion for 30 seconds); long-term airflow system (nano-hydroxyapatite airborne-particle abrasion for 120 seconds); Er:YAG laser (120 mJ/pulse at 10 Hz). There were also two control groups (n = 10 each): contaminated disc (negative control) and sterile disc (positive control). Scanning electron microscopy, energy-dispersive x-ray spectroscopy, and dynamic contact angle analysis were used to determine the most effective surface-treatment method. The highest percentage of carbon (C) atoms was observed in the negative control group, and the lowest percentage of C atoms was found in the long-term airflow group, followed by the short-term airflow, laser, ultrasonic + H 2 O 2 , ultrasonic, and mechanical groups. When the groups were examined for wettability, the lowest contact angle degree was observed in the long-term airflow, short-term airflow, and laser groups. Nano-hydroxyapatite and laser treatments for detoxifying and improving infected titanium surfaces may show the most suitable results for reosseointegration.

Aim: The aim of this present study was to evaluate the effect of gingival thickness (GT) and keratinized tissue width (KTW) using injectable platelet-rich fibrin (i-PRF) alone and with microneedling (MN) in individuals with thin periodontal phenotypes., Materials and Methods: In this split-mouth study, 33 systemically healthy patients with thin periodontal phenotypes were randomly treated with MN + i-PRF and i-PRF. I-PRF was injected on one side, and MN + i-PRF was performed on the other side of the same patient at 4 sessions with 10-day intervals. Clinical periodontal measurements, GT and KTW were assessed before the treatment and every month for six months after the final injection., Results: After the evaluation of GT between the groups, a statistically significant difference was found in MN + i-PRF group at the sixth month. In the intra-group comparisons, a statistically significant increase in GT was observed within both i-PRF [from 0.43 mm ± 0.14 to 0.62 mm ± 0.11 (p < .001)] and MN + i-PRF [from 0.4 mm ± 0.14 to 0.66 mm ± 0.12 (p < .001)] groups at the sixth month., Conclusions: In individuals with thin periodontal phenotypes, standalone i-PRF and i-PRF with MN may have an influence in increasing GT. The results suggest that application of i-PRF and MN may be a first step of non-surgical method for increasing gingival thickness., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Dental implant material has an impact on adhesion and spreading of oral mucosal cells on its surface. Platelet-rich fibrin (PRF), a second-generation platelet concentrate, can enhance cell proliferation and adhesion. The aim was to examine the regulatory effects of PRF and titanium surfaces on cellular adhesion, spread, and cytokine expressions of gingival keratinocytes. Human gingival keratinocytes were cultured on titanium grade 4, titanium grade 5 (Ti5), and HA discs at 37 °C in a CO2 incubator for 6 h and 24 h, using either elutes of titanium-PRF (T-PRF) or leukocyte and platelet-rich fibrin (L-PRF), or mammalian cell culture medium as growth media. Cell numbers were determined using a Cell Titer 96 assay. Interleukin (IL)-1β, IL-1Ra, IL-8, monocyte chemoattractant protein (MCP)-1, and vascular endothelial growth factor (VEGF) expression levels were measured using the Luminex ® xMAP™ technique, and cell adhesion and spread by scanning electron microscopy. Epithelial cell adhesion and spread was most prominent to Ti5 surfaces. L-PRF stimulated cell adhesion to HA surface. Both T-PRF and L-PRF activated the expressions of IL-1 β, IL-8, IL-1Ra, MCP-1, and VEGF, T-PRF being the strongest activator. Titanium surface type has a regulatory role in epithelial cell adhesion and spread, while PRF type determines the cytokine response.

Background and objective: The purpose of this randomized controlled clinical trial is to evaluate the efficiency of erbium-doped:yttrium-aluminum-garnet (Er:YAG) laser adjunct to nonsurgical periodontal debridement on clinical periodontal parameters and red complex periodontopathogens. Materials and methods: Thirty-eight systematically healthy, never-smoker patients with chronic periodontitis were randomly assigned to one of two groups in a parallel design: 1-scaling and root planing (SRP) and 2-SRP + Laser (SRP + L). SRP and SRP + L administration were completed within 24 h. Clinical attachment level (CAL), probing depth (PD), plaque index (PI), and bleeding on probing (BOP) were recorded at baseline and 3 and 6 months after treatment. Subgingival plaque samples were also measured 1 month after treatment. Microbiological evaluation was performed using real-time polymerase chain reaction. Results: All clinical parameters significantly improved 3 and 6 months after treatment in both groups. In the deep and moderately deep pockets, PD reduction and CAL gain between baseline and 6 months were significantly different between the groups ( p  < 0.05). There were no statistically significant differences regarding BOP and PI between the groups. There were no statistically significant differences in Pg , Tf , and Td levels between the SRP and SRP + L groups at any time point ( p  > 0.05). Conclusions: Within the limits of this randomized clinical trial, the adjunctive use of Er:YAG laser with SRP may be beneficial in moderately deep and deep pockets to improve CAL and PD. However, Er:YAG laser failed to demonstrate additional microbiological benefits in nonsurgical periodontal treatment. Clinicaltrials.gov #NCT03387371.

Objective: The aim of this study was to determine the effects of low-level laser therapy (LLLT) on wound healing at free gingival graft (FGG) donor sites., Materials and Methods: Forty patients requiring FGG were selected for this randomized, controlled, and double-blinded prospective clinical trial. The FGG donor sites were treated with LLLT and compared with an untreated control group. The Wound-Healing Index (WHI), tissue consistency, color match, and H 2 O 2 bubbling test for the evaluation of complete wound epithelialization were recorded on the 3rd, 7th, 14th and 21st days. The pain-burning level, number of analgesics, and bleeding were recorded for 7 days. Donor area soft tissue thickness (TT) was measured at baseline and at the first month., Results: The prevalence of Complete Wound Epithelization was higher in the LLLT group than in the control group on the 14th day (p < 0.001). The bleeding was lower in the test group than in the control group during the first 2 days (p ≤ 0.001). Higher WHI Scores were observed in the test group relative to the control group at all visits (p ≤ 0.001). Color match scores were higher in the test group than in the control group at the first 3 visits (p < 0.05). The TT changed from 4.62 ± 0.79 to 4.71 ± 0.82 mm in the LLLT group and from 4.23 ± 0.62 to 4.01 ± 0.68 mm in the control group., Conclusions: It can be concluded that LLLT enhances FGG donor site wound healing and preserves TT at palatinal donor sites.

Objective: We aimed to determine the clinical effects of titanium-prepared, platelet-rich fibrin (T-PRF) on human palatal mucosal wound healing (PMWH) and to identify its effect on time-dependent changes in palatal soft-tissue thickness (PSTT) in terms of histoconduction, which is a new concept., Materials and Methods: Free gingival graft (FGG) donor sites were treated with T-PRF and compared with an untreated control group. The results of colour match and H 2 O 2 -bubbling tests for complete wound epithelization (CWE) were recorded on days 3, 7, 14 and 21. Pain level, number of analgesics used and bleeding status were recorded for the first 7 days. PSTT was measured at baseline and after 1 and 6 months., Results: Colour match scores of the test group were significantly higher than those of the control group at 7 and 14 days. CWE was observed at a higher frequency in the test group than in the control group on day 14. Post-operative bleeding prevalence was lower in the test group than in the control group for the first 2 days. A time-dependent decrease in PSTT was observed at 1 and 6 months in the control group compared with baseline (baseline, 4.23 ± 0.62 mm; 1 month, 4.01 ± 0.68 mm; and 6 months, 3.93 ± 0.69 mm). However, no significant difference was found in the test group (baseline, 4.29 ± 0.64 mm; 1 month, 4.61 ± 0.51 mm; and 6 months, 4.51 ± 0.58 mm)., Conclusion: The T-PRF membrane exhibited positive effects on PMWH. T-PRF, which is a promising autogenous matrix for histoconduction, may also be preferred as an autogenous alternative to connective tissue grafts in the treatment of gingival recessions and peri-implant mucosal recessions.

Purpose: To evaluate the effect of platelet-rich fibrin (PRF) on the early bone healing process with bone scintigraphy based on technetium-99m methylene diphosphonate uptake in third molar extraction sockets., Patients and Methods: Fourteen patients with bilaterally soft tissue impacted third mandibular molars were included in the study. The right and left impacted third molars were surgically extracted in the same session. PRF was randomly administered into one of the extraction sockets, whereas the contralateral sockets were left without treatment. Four weeks after surgery, scintigrams were obtained to evaluate scintigraphic differences between PRF-treated and non-PRF-treated sockets. After completion of the clinical study, PRF samples were evaluated by light and scanning electron microscopy., Results: The average increase in technetium-99m methylene diphosphonate uptake as an indication of enhanced bone healing did not differ significantly between PRF-treated and non-PRF-treated sockets 4 weeks postoperatively (P > .05). Abundant fibrin and inflammatory cells were observed by light microscopic examination of PRF samples. Scanning electron microscopic analysis of PRF revealed the existence of platelet aggregates in a fibrin network and crystalline particles on the outer surface of PRF., Conclusions: PRF might not lead to enhanced bone healing in soft tissue impacted mandibular third molar extraction sockets 4 weeks after surgery. PRF exhibits the potential characteristics of an autologous fibrin matrix. However, whether the presence of crystal-like particles on the outer surface of PRF alters bone healing should be investigated further., (Copyright 2010 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

The purpose of this study was to evaluate microscopically the newly formed hard tissue after a consolidation period of mandibular symphyseal distraction osteogenesis (MSDO). Sixteen patients underwent MSDO treatment. After a latency period of seven days, the distraction device was activated by the patient once in the morning and once in the evening, for a total of one mm per day for a mean 10.1 +/- 2.8 days, and the mean opening of the device was 8.1 +/- 1.7 mm. The device was usually maintained in position approximately 90 days after surgery. After the completion of the distraction period, the lower anterior teeth were bonded and tooth movement into the distraction site was initiated. After a consolidation period, second surgery was performed to remove the distraction devices. During the second surgery, hard tissue biopsies were taken on the apical region of the two central incisors and the left canine. The samples were fixed in 10% buffered formalin and decalcified in 3% HNO(3) solutions. New bone formation was present within the distraction gap immediately after the consolidation period. The cellular construction was more irregular in the distraction sections than in the normal bone sections. The newly distracted area was not complete immediately after the consolidation period. Furthermore, the newly formed bone had a membranous structure, which indicates continual maturation. Bone exposed to stretching forces undergoes new bone formation, and the newly formed bone is of a membranous type also named as a woven type.

Background: Sacral bone fractures after direct traumas such as gunshot wounds and blunt sacral traumas are rarely, whereas those occurring after indirect traumas with vertical shear mechanisms ( car accidents or falls) are more frequently seen., Methods: A cadaver sacrum was modelled 3-dimensionally using finite element software. Left sacroiliac joint was modeled to simulate a 75- kg man falling on one leg from a height of 5 meters. An impact load of 10 kN was transferred to the sacrum via intervertebral disc surface and two facets. Von Mises equivalent stress distribution was estimated., Results: Von Mises stress distribution was calculated for sacral ala (430 MPa), S1 pedicle (225 MPa), and S1 lamina (35 MPa). Stress values were 200 Mpa, 130 Mpa, 105 Mpa, and 55 MPa on ventrolateral, dorsomedial, ventromedial and dorsolateral sides of S1 foramen respectively. Vertical shear injury caused stress distribution to concentrate at sacral ala and S1 pedicle (zone I). Local stress distribution around S1 foramen is concentrated ventrolaterally, Conclusion: High incidence of zone I sacral fractures and low incidence of neurological deficits could be explained by concentration of stress at sacral ala. Zone II fractures might be due to by transfer of triggered stresses from sacral ala and S1 pedicle to ventrolateral side of S1 foramen.