María Prados

María es doctora (PhD) en Ingeniería Mecánica por la Universidad de Zaragoza,  Ingeniero Industrial e Ingeniero Técnico Industrial con especialidad en Mecánica por la Universidad Pontificia Comillas (ICAI).

En la actualidad trabaja en el departamento de Nuevas Tecnologías y Proyectos I+D de una de las principales empresas del sector sanitario en España, donde desarrolla proyectos relacionados con la ingeniería biomédica y de los materiales, así como las redes neuronales y la inteligencia artificial, siendo sus campos de interés.

Con anterioridad ha participado como investigadora en diferentes proyectos de investigación bajo el amparo del art. 83 LOU en la Universidad Rey Juan Carlos, donde desarrolló modelos de fatiga probabilista mediante elementos finitos y diferentes estudios numéricos relacionados con la biomecánica en el campo de la odontología.

Cuenta con una amplia experiencia en la investigación y la redacción científica. Este trabajo está avalado con la publicación de diversos artículos científicos en revistas Journal Citation Reports (JCR) en áreas como bioingeniería, materiales, odontología y redes neuronales entre otras.

Este trabajo científico le ha permitido participar en más de una decena de congresos internacionales, colaborando con profesionales del sector interesados en proporcionar respaldo científico a sus técnicas e ideas.

En la actualidad colabora como profesora asociada en la Universidad Carlos III de Madrid, la Universidad de Alcalá y como profesora en la Universidad Europea Miguel de Cervantes. Cuenta con acreditaciones ANECA a las figuras de Profesor Contratado Doctor, Profesor de Universidad Privada y Profesor Ayudante Doctor.

Datos de contacto

Áreas de trabajo en Sophia

Innovación

Investigación

Estudios con elementos finitos

Formación y docencia

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Redacción científica

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Publicaciones JCR

A Validation Employing Convolutional Neural Network for the Radiographic Detection of Absence or Presence of Teeth

Dental radiography plays an important role in clinical diagnosis, treatment and making decisions. In recent years, efforts have been made on developing techniques to detect objects in images. The aim of this study was to detect the absence or presence of teeth using an effective convolutional neural network, which reduces calculation times and has success rates greater than 95%. A total of 8000 dental panoramic images were collected. Each image and each tooth was categorized, independently and manually, by two experts with more than three years of experience in general dentistry. The neural network used consists of two main layers: object detection and classification, which is the support of the previous one. A Matterport Mask RCNN was employed in the object detection. A ResNet (Atrous Convolution) was employed in the classification layer. The neural model achieved a total loss of 0.76% (accuracy of 99.24%). The architecture used in the present study returned an almost perfect accuracy in detecting teeth on images from different devices and different pathologies and ages.

Enlace a la publicación: https://www.mdpi.com/2077-0383/10/6/1186

Dental Caries Diagnosis and Detection Using Neural Networks: A Systematic Review

Dental caries is the most prevalent dental disease worldwide, and neural networks and artificial intelligence are increasingly being used in the field of dentistry. This systematic review aims to identify the state of the art of neural networks in caries detection and diagnosis. A search was conducted in PubMed, Institute of Electrical and Electronics Engineers (IEEE) Xplore, and ScienceDirect. Data extraction was performed independently by two reviewers. The quality of the selected studies was assessed using the Cochrane Handbook tool. Thirteen studies were included. Most of the included studies employed periapical, near-infrared light transillumination, and bitewing radiography. The image databases ranged from 87 to 3000 images, with a mean of 669 images. Seven of the included studies labeled the dental caries in each image by experienced dentists. Not all of the studies detailed how caries was defined, and not all detailed the type of carious lesion detected. Each study included in this review used a different neural network and different outcome metrics. All this variability complicates the conclusions that can be made about the reliability or not of a neural network to detect and diagnose caries. A comparison between neural network and dentist results is also necessary.

Enlace a la publicación: https://www.mdpi.com/2077-0383/9/11/3579

Influence of Bone Definition and Finite Element Parameters in Bone and Dental Implants Stress: A Literature Review

Bone plays an important role in dental implant treatment success. The goal of this literature review is to analyze the influence of bone definition and finite element parameters on stress in dental implants and bone in numerical studies. A search was conducted of Pubmed, Science Direct and LILACS, and two independent reviewers performed the data extraction. The quality of the selected studies was assessed using the Cochrane Handbook tool for clinical trials. Seventeen studies were included. Titanium was the most commonly-used material in dental implants. The magnitude of the applied loads varied from 15 to 300 N with a mean of 182 N. Complete osseointegration was the most common boundary condition. Evidence from this review suggests that bone is commonly defined as an isotropic material, despite being an anisotropic tissue, and that it is analyzed as a ductile material, instead of as a fragile material. In addition, and in view of the data analyzed in this review, it can be concluded that there is no standardization for conducting finite element studies in the field of dentistry. Convergence criteria are only detailed in two of the studies included in this review, although they are a key factor in obtaining accurate results in numerical studies. It is therefore necessary to implement a methodology that indicates which parameters a numerical simulation must include, as well as how the results should be analyzed.

Enlace a la publicación: https://www.mdpi.com/2079-7737/9/8/224

Dental Images Recognition Technology and Applications: A Literature Review

Neural networks are increasingly being used in the field of dentistry. The aim of this literature review was to visualize the state of the art of artificial intelligence in dental applications, such as the detection of teeth, caries, filled teeth, crown, prosthesis, dental implants and endodontic treatment. A search was conducted in PubMed, the Institute of Electrical and Electronics Engineers (IEEE) Xplore and arXiv.org. Data extraction was performed independently by two reviewers. Eighteen studies were included. The variable teeth was the most analyzed (n = 9), followed by caries (n = 7). No studies detecting dental implants and filled teeth were found. Only two studies investigated endodontic applications. Panoramic radiographies were the most common image employed (n = 5), followed by periapical images (n = 3). Near-infrared light transillumination images were employed in two studies and bitewing and computed tomography (CT) were employed in one study. The included articles used a wide variety of neuronal networks to detect the described variables. In addition, the database used also had a great heterogeneity in the number of images. A standardized methodology should be used in order to increase the compatibility and robustness between studies because of the heterogeneity in the image database, type, neural architecture and results.

Enlace a la publicación: https://www.mdpi.com/2076-3417/10/8/2856

The Effect on Bone Stress in Oral Prosthetic Rehabilitation Supported by Different Number of Dental Implants: A Numerical Analysis

The aim of this study was to compare the mechanical behavior of two types of prosthesis as well as the stress distribution on the prostheses’ components and the bone. Two groups were analyzed: in the first group (M1), the prothesis was composed of two implants placed at a distance of 14 mm; in the second group (M2), the prothesis was composed of three implants installed at a distance of 9.7 mm from each other. An axial load of 100 N distributed on the cantilever throughout the region from the distal implant and a 30 N axial load on the implants in the inter-foramen region, were applied in both model 1 and model 2. In both models, the stress was concentrated in the region near the neck of the implant, resulting in a maximum value of 143 MPa in M1 and of 131MPa in M2. In M1, the stress along the bone varied from of -4.7 MPa to 13.57 MPa, whereas in M2, it varied from -10 to 12 MPa. According to the results obtained, the model corresponding to six implants presented a better distribution of bone stress around the implants.

Enlace a la publicación: https://www.mdpi.com/2076-3417/9/22/4920/htm

A Finite Element Analysis to Compare Stress Distribution on Extra-Short Implants with Two Different Internal Connections

Background: The goal of this study was to analyze the stress distribution on two types of extra-short dental implants with 5 mm of length: An internal hexagon (IH) and morse taper connection (MT). Methods: The three-dimensional model was composed of trabecular and cortical bone, a crown, an extra-short dental implant and their components. An axial load of 150 N was applied and another inclined 30° with the same magnitude. Results: Stress concentrations on the IH implant are observed in the region of the first threads for the screw. However, in the MT implant the highest stress occurs at the edges of the upper implant platform. Conclusions: In view of the results obtained in this study the two types of prosthetic fittings present a good stress distribution. The Morse taper connections presented better behavior than the internal in both loading configurations.

Enlace a la publicación: https://www.mdpi.com/2077-0383/8/8/1103

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

Background: 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.

Enlace a la publicación: https://www.mdpi.com/2075-4701/9/5/535

Biomechanical and Histological Analysis of Titanium (Machined and Treated Surface) Versus Zirconia Implant Materials: An In Vivo Animal Study

Objectives: The aim of this study was to performan in vivo histological comparative evaluation of bone formation around titanium (machined and treated surface) and zirconia implants. For the present study were used 50 commercially pure titanium implants grade IV, being that 25 implants with a machined surface (TiMgroup), 25 implants with a treated surface (TiT group) and, 25 implants were manufactured in pure zirconia (Zr group). The implants (n = 20 per group) were installed in the tibia of 10 rabbits. The implants distribution was randomized (n = 3 implants per tibia). Five implants of each group were analyzed by scanning electron microscopy and an optical laser profilometer for surface roughness characterization. Six weeks after the implantation, 10 implants for each group were removed in counter-torque for analysis of maximum torque value. The remaining samples were processed, included in historesin and cut to obtain non-decalcified slides for histomorphological analyses and histomorphometric measurement of the percentage of bone-implant contact (BIC%). Comparisons were made between the groups using a 5% level of significance (p < 0.05) to assess statistical differences. The results of removal torque values (mean ± standard deviation) showed for the TiM group 15.9 ± 4.18 N cm, for TiT group 27.9 ± 5.15 N cm and for Zr group 11.5 ± 2.92 N cm, with significant statistical difference between the groups (p < 0.0001). However, the BIC% presented similar values for all groups (35.4 ± 4.54 for TiMgroup, 37.8 ± 4.84 for TiT group and 34.0 ± 6.82 for Zr group), with no statistical differences (p = 0.2171). Within the limitations of the present study, the findings suggest that the quality of the new bone tissue formed around the titanium implants present a superior density (maturation) in comparison to the zirconia implants.

Enlace a la publicación: https://www.mdpi.com/1996-1944/12/6/856

Complete mechanical characterization of an external hexagonal implant connection: in vitro study, 3D FEM, and probabilistic fatigue

The aim of this study was to fully characterize the mechanical behavior of an external hexagonal implant connection (ø3.5 mm, 10-mm length) with an in vitro study, a three-dimensional finite element analysis, and a probabilistic fatigue study. Ten implant-abutment assemblies were randomly divided into two groups, five were subjected to a fracture test to obtain the maximum fracture load, and the remaining were exposed to a fatigue test with 360,000 cycles of 150 ± 10 N. After mechanical cycling, all samples were attached to the torque-testing machine and the removal torque was measured in Newton centimeters. A finite element analysis (FEA) was then executed in ANSYS® to verify all results obtained in the mechanical tests. Finally, due to the randomness of the fatigue phenomenon, a probabilistic fatigue model was computed to obtain the probability of failure associated with each cycle load. FEA demonstrated that the fracture corresponded with a maximum stress of 2454 MPa obtained in the in vitro fracture test. Mean life was verified by the three methods. Results obtained by the FEA, the in vitro test, and the probabilistic approaches were in accordance. Under these conditions, no mechanical etiology failure is expected to occur up to 100,000 cycles.

Enlace a la publicación: https://pubmed.ncbi.nlm.nih.gov/29949022/

Probability of Failure of Internal Hexagon and Morse Taper Implants with Different Bone Levels: A Mechanical Test and Probabilistic Fatigue

Purpose: The goal of this study was to foresee the fatigue life of two implant connections, evaluate the failure probability with several bone levels, and compare the in vitro test results with finite element results. Materials and Methods: Mechanical tests were done with 60 implants (Ø3.50 mm), and abutments were used. These implants were divided into two groups with 30 implants each: internal hexagon and Morse taper. Three bone levels and 10 implants for each level were analyzed. The first level was considered at the platform level, the second at 3 mm, and the last level at 5 mm above the platform resin. A quasi-static loading at 30 degrees was applied to the axis of the implant in a universal machine. Six models were created and assembled to reproduce the conditions used in the laboratory testing. All models had restricted all displacement at the bone (bottom and lateral). Loads employed in the numerical test were obtained experimentally. Loads and material properties were supposed to be random. Then, failure probability was calculated by the probabilistic methodology. Results: The internal hexagon group obtained the following mean fracture strengths: 2,092 N at the first level, 1,041 N at the second level, and 898 N at the third level. The mean fracture strengths for the Morse taper group were as follows: 1,687 N at the first level, 1,644 N at the second level, and 1,159 N at the third level. Results obtained by the finite element analysis are in accordance with the in vitro mechanical test results. The Morse taper group obtained a better behavior at bone levels 2 and 3 than the internal hexagon group. An important dependency between failure probability and bone level was found in the internal hexagon group. However, a similar behavior in levels 2 and 3 was obtained for the Morse taper group. Conclusion: In view of the mechanical results, the Morse taper group has a better behavior in bone levels 2 and 3 than the internal hexagon group. This is also in accordance with the probabilistic fatigue outcomes.

Enlace a la publicación: https://pubmed.ncbi.nlm.nih.gov/30427957

Finite element analysis comparing WaveOne, WaveOne Gold, Reciproc and Reciproc Blue responses with bending and torsion tests

To evaluate the bending and torsional properties of four nickel-titanium endodontic files, we simulated and compared WaveOne® primary size 25 with 0.07 taper, WaveOne Gold® primary size 25 with 0.07 taper, Reciproc® primary size 25 with 0.08 taper, and Reciproc Blue® primary size 25 with 0.08 taper. Three-dimensional models were created using computer-aided design software and numerically analyzed in ANSYS® Workbench. Boundary conditions for the numerical analyses were based on the ISO 3630–1 specifications. The highest stress levels were recorded for WaveOne® and Reciproc®. Numerical results of the bending test showed that WaveOne Gold® is 86% more flexible than WaveOne® with a deflection of 3 mm. Reciproc Blue® was 42.31% more flexible than Reciproc® file with a deflection of 3 mm. The WaveOne® instrument withstood the highest stress under the torsion test, followed by Reciproc®, then Reciproc Blue® files. The stress under torsion in the WaveOne® and WaveOne Gold® files is reduced in a 51%. Regarding Reciproc® and Reciproc Blue® files, the stress under torsional moments remains very similar. Our results exposed a considerable difference in terms of stress tolerance between WaveOne® and WaveOne Gold®. However, Reciproc® files demonstrated a similar stress distribution. The results obtained through finite element analysis suggest that thermal treatment of files might improve their flexibility, increasing resistance during the preparation of highly curved canals. Also, the values obtained regarding the improvement of flexibility were in accordance with the manufacturer claims.

Enlace a la publicación: https://pubmed.ncbi.nlm.nih.gov/30366307/

Implant Treatment in Atrophic Maxilla by Titanium Hybrid-Plates: A Finite Element Study to Evaluate the Biomechanical Behavior of Plates

A severely atrophied maxilla presents serious limitations for rehabilitation with osseointegrated implants. This study evaluated the biomechanical and long-term behavior of titanium hybrid-plates in atrophic maxilla rehabilitation with finite elements and probabilistic methodology. A three-dimensional finite element model based on a real clinical case was built to simulate an entirely edentulous maxilla with four plates. Each plate was deformed to become accustomed to the maxilla’s curvature. An axial force of 100 N was applied in the area where the prosthesis was adjusted in each plate. The von Mises stresses were obtained on the plates and principal stresses on maxilla. The difference in stress between the right and left HENGG-1 plates was 3%, while between the two HENGG-2 plates it was 2%, where HENGG means Highly Efficient No Graft Gear. A mean maximum value of 80 MPa in the plates’ region was obtained, which is a lower value than bone resorption stress. A probability cumulative function was computed. Mean fatigue life was 1,819,235 cycles. According to the results of this study, it was possible to conclude that this technique based on titanium hybrid-plates can be considered a viable alternative for atrophic maxilla rehabilitation, although more studies are necessary to corroborate the clinical results.

Enlace a la publicación: https://www.mdpi.com/2075-4701/8/8/573

Evaluation of Fatigue Behavior in Dental Implants from In Vitro Clinical Tests: A Systematic Review

In the area of dentistry, there is a wide variety of designs of dental implant and materials, especially titanium, which aims to avoid failures and increase their clinical durability. The purpose of this review was to evaluate fatigue behavior in different connections and implant materials, as well as their loading conditions and response to failure. In vitro tests under normal and dynamic loading conditions evaluating fatigue at implant and abutment connection were included. A search was conducted in PubMed, Scopus, and Science Direct. Data extraction was performed independently by two reviewers. The quality of selected studies was assessed using the Cochrane Handbook proposed by the tool for clinical trials. Nineteen studies were included. Fourteen studies had an unclear risk and five had high risk of bias. Due to the heterogeneity of the data and the evaluation of the quality of the studies, meta-analysis could not be performed. Evidence from this study suggests that both internal and morse taper connections presented a better behavior to failure. However, it is necessary to unify criteria in the methodological design of in vitro studies, following methodological guidelines and establishing conditions that allow the homogenization of designs in ISO (International Organization for Standardization) standards.

Enlace a la publicación: https://www.mdpi.com/2075-4701/8/5/313

Misfit of Three Different Implant-Abutment Connections Before and After Cyclic Load Application: An In Vitro Study

Purpose: This study aimed to evaluate the misfit of three different implant-abutment connections before and after cycling load. Materials and methods: One hundred twenty dental implants and correspondent prefabricated titanium abutments were used. Three different implant-abutment connections were evaluated: Morse taper (MT group), external hexagon (EH group), and internal hexagon (IH group). Forty implants and 40 abutments were used per group. The parameters for the mechanical evaluation were set as: 360,000 cycles, load of 150 N, and frequency of 4 Hz. Samples were sectioned in their longitudinal and transversal axes, and the misfit of the implant-abutment connection was evaluated by scanning electron microscopy analysis. One-way analyses of variance, Tukey post hoc analyses (α = .05), and t test (P < .05) were used to determine differences between groups. Results: At the longitudinal direction, all the groups showed the presence of microgaps before cycling load; after cycling load, microgaps were reduced in all groups (P > .05). Transversally, only the MT group showed full fitting after cycling load compared with the other groups (EH and IH) (P < .0001). Conclusion: The application of cycling load produces an accommodation of the implant-abutment connection in internal, external, and Morse taper connections. In the longitudinal direction, the accommodation decreases and/or eliminates the gap observed initially (before load). In the horizontal direction, Morse cone implant-abutment connections experience a complete accommodation with the elimination of the gap.

Enlace a la publicación: https://pubmed.ncbi.nlm.nih.gov/28708914/

New Model to Study Fatigue in Dental Implants Based on Probabilistic Finite Elements and Cumulative Damage Model

The aim of this study was to predict the fatigue life of two different connections of a dental implant as in load transfer to bone. Two three-dimensional models were created and assembled. All models were subjected to a natural masticatory force of 118N in the angle of 75º to the occlusal plane. All degrees of freedom in the inferior border of the cortical bone were restrained, and the mesial and distal borders of the end of the bone section were constrained. Fatigue material data and loads were assumed as random variables. Maximum principal stresses on bone were evaluated. Then, the probability of failure was obtained by the probabilistic approach. The maximum principal stress distribution predicted in the cortical and trabecular bone is 32 MPa for external connection and 39 MPa for internal connection. A mean life of 103 and 210 million cycles were obtained for external and internal connection, respectively. Probability cumulative function was also evaluated for both connection types. This stochastic model employs a cumulative damage model and probabilistic finite element method. This methodology allows the possibility of measured uncertainties and has a good precision on the results.

Enlace a la publicación: https://www.hindawi.com/journals/abb/2017/3726361/

A random fatigue of mechanize titanium abutment studied with Markoff chain and stochastic finite element formulation

To measure fatigue in dental implants and in its components, it is necessary to use a probabilistic analysis since the randomness in the output depends on a number of parameters (such as fatigue properties of titanium and applied loads, unknown beforehand as they depend on mastication habits). The purpose is to apply a probabilistic approximation in order to predict fatigue life, taking into account the randomness of variables. More accuracy on the results has been obtained by taking into account different load blocks with different amplitudes, as happens with bite forces during the day and allowing us to know how effects have different type of bruxism on the piece analysed.

Enlace a la publicación: https://pubmed.ncbi.nlm.nih.gov/27073012/

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 0º, 15º, and 20º and a force of 489N 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.

Enlace a la publicación: https://www.hindawi.com/journals/bmri/2016/8927156/

Lack of clinical evidence on low-level laser therapy (LLLT) on dental titanium implant: a systematic review

Low-level laser therapy (LLLT) has proved to have biostimulating effects on tissues over which they are applied, therefore accelerating the healing process. Most studies in implantology were focused on a reduction of the duration of osseointegration. There exist few articles analyzing the potential effects of these therapies on the osseointegration of titanium dental implants. The aim of this study was to assess the effect of LLLT on the interaction between the bone and the titanium dental implant and the methodological quality of the studies. We conducted an electronic search in PubMed, ISI Web, and Cochrane Library. From 37 references obtained, only 14 articles met the inclusion criteria. The analysis of the studies shows that most of the experiments were performed in animals, which have a high risk of bias from the methodological point of view. Only two studies were conducted in human bone under different conditions. Several protocols for the use of low-power laser and different types of laser for all studies analyzed were used. Although animal studies have shown a positive effect on osseointegration of titanium implants, it can be concluded that it is necessary to improve and define a unique protocol to offer a more conclusive result by meta-analysis.

Enlace a la publicación: https://pubmed.ncbi.nlm.nih.gov/26754180/

Dental Implants Fatigue as a Possible Failure of Implantologic Treatment: The Importance of Randomness in Fatigue Behaviour

Objective. To show how random variables concern fatigue behaviour by a probabilistic finite element method. Methods. Uncertainties on material properties due to the existence of defects that cause material elastic constant are not the same in the whole dental implant the dimensions of the structural element and load history have a decisive influence on the fatigue process and therefore on the life of a dental implant. In order to measure these uncertainties, we used a method based on Markoff chains, Bogdanoff and Kozin cumulative damage model, and probabilistic finite elements method. Results. The results have been obtained by conventional and probabilistic methods. Mathematical models obtained the same result regarding fatigue life; however, the probabilistic model obtained a greater mean life but with more information because of the cumulative probability function. Conclusions. The present paper introduces an improved procedure to study fatigue behaviour in order to know statistics of the fatigue life (mean and variance) and its probability of failure (fatigue life versus probability of failure).

Enlace a la publicación: https://www.hindawi.com/journals/bmri/2015/825402/

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