A Finite Element Analysis of the Fatigue Behavior and Risk of Failure of Immediate Provisional Implants

This article belongs to the Special Issue Titanium in Medical and Dental ApplicationsBackground: Temporary dental implants are used to support provisional prostheses. The goal of this study was to obtain the stress&-number (S&-N) curves of cycles of five temporary dental implants employing finite element methods. Additionally, a probabilistic analysis was carried out to obtain the failure probability of each dental implant. Methods: To obtain these curves, first the maximum value of the fracture load was obtained by simulation of a compression test. Subsequently, the fatigue life was simulated by varying each of the loads from the maximum value to a minimum value (10% of the maximum value), and the minimum number of cycles that it should support was calculated. Results: The fatigue limit of titanium in these implants was around 200 MPa with the maximum number of cycles between 64,976 and 256,830. The maximum compression load was between 100 and 80 N. Regarding the probability of failure, all implants were expected to behave similarly. Conclusions: This study of finite elements provided the values of maximum load supported by each of the implants, and the relationship between the stress in the implant and the number of cycles that it could support with a probability of failure. An international standard on how to perform fatigue studies in temporary dental implants was deemed necessary

Chronic fluoxetine treatment in middle-aged rats induces changes in the expression of plasticity-related molecules and in neurogenesis

<p>Abstract</p> <p>Background</p> <p>Antidepressants promote neuronal structural plasticity in young-adult rodents, but little is known of their effects on older animals. The polysialylated form of the neural cell adhesion molecule (PSA-NCAM) may mediate these structural changes through its anti-adhesive properties. PSA-NCAM is expressed in immature neurons and in a subpopulation of mature interneurons and its expression is modulated by antidepressants in the telencephalon of young-adult rodents.</p> <p>Results</p> <p>We have analyzed the effects of 14 days of fluoxetine treatment on the density of puncta expressing PSA-NCAM and different presynaptic markers in the medial prefrontal cortex, hippocampus and amygdala of middle-aged (8 months old) rats. The density of puncta expressing PSA-NCAM increased in the dorsal cingulate cortex, as well as in different hippocampal and amygdaloid regions. In these later regions there were also increases in the density of puncta expressing glutamic acid decarboxylase 65/67 (GAD6), synaptophysin (SYN), PSA-NCAM/SYN and PSA-NCAM/GAD6, but a decrease of those expressing vesicular glutamate transporter 1 (VGluT1). Since there is controversy on the effects of antidepressants on neurogenesis during aging, we analyzed the number of proliferating cells expressing Ki67 and that of immature neurons expressing doublecortin or PSA-NCAM. No significant changes were found in the subgranular zone, but the number of proliferating cells decreased in the subventricular zone.</p> <p>Conclusions</p> <p>These results indicate that the effects of fluoxetine in middle-aged rats are different to those previously described in young-adult animals, being more restricted in the mPFC and even following an opposite direction in the amygdala or the subventricular zone.</p

Long-term fatigue and its probability of failure applied to dental implants

It is well known that dental implants have a high success rate but even so, there are a lot of factors that can cause dental implants failure. Fatigue is very sensitive to many variables involved in this phenomenon. This paper takes a close look at fatigue analysis and explains a new method to study fatigue from a probabilistic point of view, based on a cumulative damage model and probabilistic finite elements, with the goal of obtaining the expected life and the probability of failure. Two different dental implants were analysed. The model simulated a load of 178¿N applied with an angle of 0°, 15°, and 20° and a force of 489¿N with the same angles. Von Mises stress distribution was evaluated and once the methodology proposed here was used, the statistic of the fatigue life and the probability cumulative function were obtained. This function allows us to relate each cycle life with its probability of failure. Cylindrical implant has a worst behaviour under the same loading force compared to the conical implant analysed here. Methodology employed in the present study provides very accuracy results because all possible uncertainties have been taken in mind from the beginning

Long-Term Fatigue and Its Probability of Failure Applied to Dental Implants

It is well known that dental implants have a high success rate but even so, there are a lot of factors that can cause dental implants failure. Fatigue is very sensitive to many variables involved in this phenomenon. This paper takes a close look at fatigue analysis and explains a new method to study fatigue from a probabilistic point of view, based on a cumulative damage model and probabilistic finite elements, with the goal of obtaining the expected life and the probability of failure. Two different dental implants were analysed. The model simulated a load of 178 N applied with an angle of 0°, 15°, and 20° and a force of 489 N with the same angles. Von Mises stress distribution was evaluated and once the methodology proposed here was used, the statistic of the fatigue life and the probability cumulative function were obtained. This function allows us to relate each cycle life with its probability of failure. Cylindrical implant has a worst behaviour under the same loading force compared to the conical implant analysed here. Methodology employed in the present study provides very accuracy results because all possible uncertainties have been taken in mind from the beginning

Evaluation of the insertion torque, implant stability quotient and drilled hole quality for different drill design: an in vitro Investigation

This is the peer reviewed version of the following article: Gehrke SA, Guirado JLC, Bettach R, Fabbro MD, Martınez CP-A, Shibli JA. Evaluation of the insertion torque, implant stability quotient and drilled hole quality for different drill design: an in vitro Investigation. Clin. Oral Impl. Res. 00, 2016, 1–7], which has been published in final form at 10.1111/clr.12808. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Objective: The purpose of the present study was to compare the insertion torque and implant stability quotient between different drill design for implant site preparation. Materials and Methods: Synthetic blocks of bone (type I density) were used for drilling procedures. Three groups were evaluated: Group G1 - drilling with a single bur for a 4.2 mm conical implant; Group G2 and Group G3 - drilling with three consecutive burs for a 4.1 mm cylindrical implant and for a 4.3 mm conical implant respectively. For each group, 15 drilling procedures were performed without irrigation for 10-mm in-depth. The drilled hole quality (HQ) after the osteotomy for implant site preparation was measured in the five-first holes through a fully automated roundness/cylindricity instrument at three levels (top, middle, and bottom of the site). The insertion torque value (ITV) was achieved with a computed torquimeter and the implant stability quotient (ISQ) values were measured using a resonance frequency apparatus. Results: Thesingledrill(group1)achievedasignificantlyhigherITVandISQthanthemultipledrills for osteotomy (groups 2 and 3). Group 1 and 3 displayed significantly better HQ than group 2. Conclusions: Within the limitations of the study, the results suggest that the hole quality, in addition to the insertion torque, may significantly affect implant primary stability.Odontologí

Influence of Implant Neck Design on Peri-Implant Tissue Dimensions: A Comparative Study in Dogs

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Abstract: This in vivo study assessed (hard and soft) peri-implant tissue remodeling around implants with micro-ring and open-thread neck designs placed in a dog model. Twenty histological sections corresponding to four different implant designs that were placed in America Foxhound dogs were obtained from previous studies. All the implants had been placed under identical conditions and were divided into four groups: Group A, micro-rings on implant neck plus 0.5 mm refined surface; Group B, micro-rings on implant neck; Group C, open-thread neck; and, Group D, double-spiral neck. Eight weeks after surgery, the integrated implants were removed and processed for histological examination. Crestal bone loss and bone-to-implant contact was greater for micro-ring necks than open-thread necks. Soft tissues showed significant differences on both buccal and lingual aspects, so that the distance from peri-implant mucosa to the apical portion of the barrier epithelium was smaller in the micro-ring groups. So, in spite of generating greater bone-to-implant contact, implants with micro rings produced more bone loss than open-thread implants. Moreover, the outcomes that were obtained IPX implants smooth neck design produced less bone loss in the cervical area, following by Facility implants when compared with the other open thread and microthreaded implant designs. Implant thread design can influence on bone remodeling in the cervical area, related to bundle bone preservation.Odontologí

Evaluation of a New Dental Implant Cervical Design in Comparison with a Conventional Design in an Experimental American Foxhound Model

This is the peer reviewed versión of the following article: "Evaluation of a New Dental Implant Cervical Design in Comparison with a Conventional Design in an Experimental American Foxhound Model ", which has been published in final form at [doi:10.3390/ma11040462],. This article May be used for non-comercial pipotes in accordance with Wiley Terms an Conditions for Use of Self-Archived Versions.Odontologí

SEM-EDX Study of the Degradation Process of Two Xenograft Materials Used in Sinus Lift Procedures

Some studies have demonstrated that in vivo degradation processes are influenced by the material’s physico-chemical properties. The present study compares two hydroxyapatites manufactured on an industrial scale, deproteinized at low and high temperatures, and how physico-chemical properties can influence the mineral degradation process of material performance in bone biopsies retrieved six months after maxillary sinus augmentation. Residual biomaterial particles were examined by field scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) to determine the composition and degree of degradation of the bone graft substitute material. According to the EDX analysis, the Ca/P ratio significantly lowered in the residual biomaterial (1.08 ± 0.32) compared to the initial composition (2.22 ± 0.08) for the low-temperature sintered group, which also presented high porosity, low crystallinity, low density, a large surface area, poor stability, and a high resorption rate compared to the high-temperature sintered material. This demonstrates that variations in the physico-chemical properties of bone substitute material clearly influence the degradation process. Further studies are needed to determine whether the resorption of deproteinized bone particles proceeds slowly enough to allow sufficient time for bone maturation to occur.Odontologí

Use of Bone Marrow Aspirate Concentrate (BMAC) Associated with Hyperbaric Oxygenation Therapy in Maxillary Appositional Bone Reconstruction. A Randomized Clinical Trial

Objectives: The objective of this study was to evaluate bone reconstruction using xenograft alone and associated with bone marrow aspirate concentrate (BMAC) and hyperbaric oxygen therapy. Material and Methods: Twenty-four maxillary edentulous patients were randomly assigned into three groups: Control group (CG)—xenograft bone alone (n = 8); Group 1 (G1)—xenogeneic bone block combined with BMAC (n = 8), and Group 2 (G2)—xenogeneic bone block combined with BMAC and hyperbaric oxygenation (n = 8). Bone biopsies were harvested 6 months after grafting. Vital Mineralized Tissue (VMT), Non-vital Mineralized Tissue (NVMT), and Non-Mineralized Tissue (NMT) were measured. Computed tomography was also performed on three occasions T0 (preoperative), T4 (4 months postoperative), and T8 (8 months postoperative). The difference between T4 and T8 values with respect to T0 was used to determine the thickness level gain after 4 and 8 months, respectively. Results: The tomographic evaluation did not show significant differences between the groups either at 4 or at the 8 months postoperatively. Regarding the histomorphometric analysis, CG had the lowest percentages of VMT (36.58 ± 9.56%), whereas G1 and G2 had similar results (55.64 ± 2.83% and 55.30 ± 1.41%, respectively). Concerning NMT and NVMT levels, the opposite was observed, with CG levels of 51.21 ± 11.54% and 11.16 ± 2.37%, G1 of 39.76 ± 11.48% and 3.65 ± 0.87%, and G2 of 40.3 ± 11.48% and 4.10 ± 0.87%, respectively. Conclusions: The use of bone block xenograft associated with BMAC resulted in a significant increase of bone neoformation when compared to the xenograft alone, though hyperbaric oxygenation did not enhance the results.Odontologí

Lab-on-a-chip for the easy and visual detection of SARS-CoV-2 in saliva based on sensory polymers

The initial stages of the pandemic caused by SARS-CoV-2 showed that early detection of the virus in a simple way is the best tool until the development of vaccines. Many different tests are invasive or need the patient to cough up or even drag a sample of mucus from the throat area. Besides, the manufacturing time has proven insufficient in pandemic conditions since they were out of stock in many countries. Here we show a new method of manufacturing virus sensors and a proof of concept with SARS-CoV-2. We found that a fluorogenic peptide substrate of the main protease of the virus (Mpro) can be covalently immobilized in a polymer, with which a cellulose-based material can be coated. These sensory labels fluoresce with a single saliva sample of a positive COVID-19 patient. The results matched with that of the antigen tests in 22 of 26 studied cases (85% success rate).We gratefully acknowledge the financial support provided by all funders. Author Saul Vallejos coordinates the project leading to these results, which has received funding from "La Caixa" Foundation, under agreement LCF/PR/PR18/51130007. This work was supported by the Regional Government of Castilla y León (Junta de Castilla y León) and by the Ministry of Science and Innovation MICIN and the European Union NextGenerationEU PRTR. Author Jose Miguel García received grant PID2020–113264RB-I00 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”. Ana Arnaiz received funding from Ministerio de Universidades-European Union in the frame of NextGenerationEU RD 289/2021 (Universidad Politécnica de Madrid). Finally, all the authors want to thank the support provided by City Hall of Villadiego “Ayuntamiento de Villadiego” when looking for participants for the proof of concept