Papers by Konstantinos Michalakis
Journal of Clinical and Experimental Dentistry, 2019
Journal of Clinical and Experimental Dentistry, 2019
Materials Science and Engineering: C, 2014
BioMed Research International, 2021
Osteosarcoma is considered to be a highly malignant tumor affecting primarily long bones. It meta... more Osteosarcoma is considered to be a highly malignant tumor affecting primarily long bones. It metastasizes widely, primarily to the lungs, resulting in poor survival rates of between 19 and 30%. Standard treatment consists of surgical removal of the affected site, with neoadjuvant and adjuvant chemotherapy commonly used, with the usual side effects and complications. There is a need for new treatments in this area, and silver nanoparticles (AgNPs) are one potential avenue for exploration. AgNPs have been found to possess antitumor and cytotoxic activity in vitro, by demonstrating decreased viability of cancer cells through cell cycle arrest and subsequent apoptosis. Integral to these pathways is tumor protein p53, a tumor suppressor which plays a critical role in maintaining genome stability by regulating cell division, after DNA damage. The purpose of this study was to determine if p53 mediates any difference in the response of the osteosarcoma cells in vitro when different sizes an...
Material and methods. Four polyethyl methacrylate and 1 polymethyl methacrylate autopolymerizing ... more Material and methods. Four polyethyl methacrylate and 1 polymethyl methacrylate autopolymerizing reline resin products of 3 different thicknesses were tested. A cobalt-chromium edentulous maxillary cast was used to obtain 150 stone casts, 50 for each thickness of 1, 2, and 3 mm (n1⁄410). Polystyrene record bases were filled with the autopolymerizing reline resin mixture and placed on the cobalt-chromium cast, which was mounted on a reline index, to serve as denture substitutes. Two thermal probes were used to monitor the temperature rise, which was recorded at 30-second intervals until no further increase was noted. Collected data were subjected to a 2-way ANOVA and the Tukey honestly significant difference test (a1⁄4.05).
Biophysical Reviews, 2021
During metastasis, tumor cells need to adapt to their dynamic microenvironment and modify their m... more During metastasis, tumor cells need to adapt to their dynamic microenvironment and modify their mechanical properties in response to both chemical and mechanical stimulation. Physical interactions occur between cancer cells and the surrounding matrix including cell movements and cell shape alterations through the process of mechanotransduction. The latter describes the translation of external mechanical cues into intracellular biochemical signaling. Reorganization of both the cytoskeleton and the extracellular matrix (ECM) plays a critical role in these spreading steps. Migrating tumor cells show increased motility in order to cross the tumor microenvironment, migrate through ECM and reach the bloodstream to the metastatic site. There are specific factors affecting these processes, as well as the survival of circulating tumor cells (CTC) in the blood flow until they finally invade the secondary tissue to form metastasis. This review aims to study the mechanisms of metastasis from a ...
Journal of Prosthodontics, 2019
The International journal of prosthodontics
Oculo-dento-digital dysplasia (ODDD) is a congenital disorder manifesting with multiple phenotypi... more Oculo-dento-digital dysplasia (ODDD) is a congenital disorder manifesting with multiple phenotypic abnormalities involving the face, eyes, teeth, and limbs in addition to neurologic symptomatology. This report aims to present a female patient with ODDD who was referred due to extensive oral restorative needs. The presence of hypoplastic enamel triggered further evaluation. Characteristic facies with hypoplastic alae nasi and syndactyly offered greater insight into the phenotype of the syndrome. Clinical suspicion was confirmed by genetic sequencing revealing heterozygous mutation in GJA1. It is important to be aware of genetic disorders associated with characteristic dental malformations to offer appropriate counseling and treatment.
Objective: Finite element (FE) analysis can be used to quantitatively assess the mechanical behav... more Objective: Finite element (FE) analysis can be used to quantitatively assess the mechanical behavior of oral mucosa. In order to perform FE computations it is necessary to input the material parameters of each constituent into the model. Additionally, a mathematical model expressing the dynamic behavior is needed. In the past, many models –including linear ones- have been used. The objective of this study was to establish a mathematical model based on experimental data resulting from an in vitro mechanical loading test. Method: Eight palatal oral mucosa specimens were harvested from a frozen elderly human cadaver obtained through the anatomy laboratory of the Aristotle University of Thessaloniki, Greece. The specimens had a dimension of 12×8×8mm, also containing the underlying bone which had a 4mm thickness. A low-speed rotary 0.2mm diamond disc with saline irrigation was used for preparation of the specimens. Samples were tested with the use of a Scanning Probe Microscope SOLVER (N...
Medical Engineering & Physics
Encouraged by recent advances of biophysical and biochemical assays we introduce a 3D finite elem... more Encouraged by recent advances of biophysical and biochemical assays we introduce a 3D finite element model of an osteoblast, seeking an analogue between exogenous forces and intracellularly activated sensory mechanisms. The cell was reverse engineered and the dimensions of the internal cellular structures were based on literature data. The model was verified and validated against atomic force microscopy experiments and four loading scenarios were considered. The stress distributions developing on the main cellular components were calculated along with their corresponding strain values. The nucleus and mitochondria exhibited similar loading trends, with the mitochondria being stressed by an order of magnitude higher than the nucleus (e.g. 1.4 vs. 0.16 MPa). Equivalent stiffness was determined to increase by almost 50%, from the apex to the cell's periphery, as was the cell's elasticity, which was lowest when the load was exerted directly above the nucleus. The assessment of how extrinsic loads are propagated to a cell's internal structures is inherently a problem of high complexity. The findings presented in this study can provide important insight into biophysical and biochemical responses elicited in cells through mechanical stimulus. This was evident in both the nuclear and mitochondrial loading and would stipulate the important contribution of even more accurate models in the interpretation of cellular events. One Sentence Summary: The results of this numerical biomechanical study demonstrated that even minor extrinsic loads irrespective of the application site, are transduced by a fraction of the cytoskeleton to its internal structure (primarily to its mitochondria and secondary to the cell's nucleus), indicating mechanical stimulus as the dominant pathway to cell expression.
Journal of Prosthodontics
The Journal of Prosthetic Dentistry
Journal of Oral Rehabilitation
BioMed Research International
The purpose of this research project was to investigate whether or not clenching and occlusal ins... more The purpose of this research project was to investigate whether or not clenching and occlusal instability of Angle’s Class I malocclusion have an effect on body weight distribution in healthy adult subjects. Twenty adults (fourteen males and six females, ages 27-40, mean age 31.7 years, SD 3.32) were included in this study. The MatScan (Tekscan Inc., Boston, MA) system was used to measure the body weight distribution changes of the subjects. Four body weight distribution measurements were taken for each subject while (1) the mandible was in the rest position (no tooth contact) (RES), (2) subject was clenching (maximum intercuspation of the teeth with heavy occlusal forces) (CL), (3) subject was clenching on the right side (with 1 mm disocclusion on the left side) (CLR), and (4) subject was clenching on the left side (with 1 mm disocclusion on the right side) (CLL). The lateral and the anteroposterior body weight distribution changes during the different clenching conditions (both si...
The Journal of Prosthetic Dentistry
Journal of prosthodontics : official journal of the American College of Prosthodontists, Jan 16, 2017
To investigate in vitro the retention and the resistance form, as well as the failure modes of ma... more To investigate in vitro the retention and the resistance form, as well as the failure modes of maxillary premolars restored with cast metal crowns and different core materials. Sixty human extracted maxillary premolars were selected according to their size and were embedded in PMMA resin blocks. After removing a part of their clinical crowns, the teeth were randomly divided into 3 groups of 20 teeth and were either left unrestored, or they were restored with amalgam or composite resin. All teeth were prepared for a cast metal complete coverage restoration. The restorations were cemented on the prepared teeth with a resin-modified glass ionomer luting agent (GC Fuji Plus). All specimens were subjected to static loading at 1 mm/min by a universal testing machine, until failure. Half the specimens of each group were subjected to tensile loading along the long axis of the teeth. The other half were subjected to compressive loading at a 30° angle. Failure loads and failure modes for each...
Journal of Prosthodontics
To assess whether an increased concavity of maxillary labial alveolar bone is related to labial t... more To assess whether an increased concavity of maxillary labial alveolar bone is related to labial thickness of cortical bone in that area and to the presence of extraoral manifestations in the philtrum. Cone beam computed tomography images along with intra- and extraoral photographic images of 50 Caucasian female patients, age range 18 to 65 years (mean: 37 years), previously evaluated for implant treatment were assessed by three experienced prosthodontists. Patients were divided into two groups (A and B), according to the presence or absence of a horizontal groove at the philtrum area. Mann-Whitney U test (α = 0.05) was performed to reveal any statistical differences regarding the angle of the maxillary labial concavity and the labial thickness of the alveolar cortical bone between the two groups. The mean angle of the maxillary concavity in group A was 127.76° while in group B it was 137.12°. The mean thickness of the labial cortical wall of the dental, interdental, and edentulous areas of the 8 anterior teeth for group A were: 0.41 mm, 0.61 mm, and 0.46 mm, respectively; and for group B were: 0.52 mm, 0.72 mm, and 0.56 mm, respectively. The Mann-Whitney U test (α = 0.05) revealed a statistically significant difference for both the angle (p = 0.008) but not for the thickness of the bone (p = 0.062). According to the results of this study an increased maxillary labial concavity was associated with reduced thickness of the labial cortical wall and the presence of a horizontal groove at the philtrum area.
The Journal of Prosthetic Dentistry, 2016
Parallel labiolingual walls and the preservation of the cingulum in anterior tooth preparations h... more Parallel labiolingual walls and the preservation of the cingulum in anterior tooth preparations have been advocated. However, their contribution to retention and resistance form has not been evaluated. The purpose of this in vitro study was to evaluate the retention and resistance failure loads of 2 preparation designs for maxillary anterior teeth. Forty metal restorations were fabricated and paired with 40 cobalt-chromium prepared tooth analogs. Twenty of the specimens had parallel buccolingual walls at the cervical part (group PBLW; the control group), whereas the remaining 20 had converging buccolingual walls (group CBLW; the experimental group). The restorations were cemented to the tooth analogs with a resin-modified glass ionomer luting agent. Ten specimens from each group were subjected to tensile loading with a universal testing machine; the rest were subjected to compression loading until failure. Descriptive statistics and the independent t test (α=.05) were used to determine the effect of failure loads in the tested groups. The independent t test revealed statistically significant differences between the tested groups in tensile loading (P<.001) and in compressive loading (P<.001). The PBLW group presented a higher tensile failure load than the CBLW. On the contrary, the PBLW group presented a smaller compression failure load than the CBLW. Parallelism of the buccolingual axial walls in anterior maxillary teeth increased the retention form but decreased the resistance form.
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Papers by Konstantinos Michalakis