Anatomsko 3D modeliranje specifičnih bioloških struktura

Mechanical behavior of biological structures is a common subject of scientific research. The results of such investigations offer the precise insight into the biomechanical properties of biological structures and are usefull for predicting their behavior when subjected to loading. Although, such biomechanical investigations were conducted on experimental animals nowadays are very popular investigations concerning mathematical experimental models. The most common is the finite element method analysis. A digital model of a structure of interest has to be created for an investigation with the finite element method. Once the digital model is created with the use of computer technology numerous changes of elements and structures are possible, with different applications of the simulated load. The aim of this paper was to to present the development of our own three-dimensional tooth model created for finite element analyses of intact tooth behavior under functional loading. Also, the idea was to evaluate the possibility for using finite element analysis in veterinary biomechanical research. Our own 3D model was created using computer software according to available literature data, and facts gained from freshly extracted intact teeth and plaster models. It is necessary to emphasize that FEM is an effective tool that has been adapted from the engineering arena to biomechanic research and has the potential to contribute to the growing scientific basis of knowledge in veterinary dentistry.Mehaničko ponašanje bioloških struktura je vrlo čest predmet naučnih istraživanja. Rezultati takvih istraživanja pružaju precizne podatke o biomehaničkim karakteristikama bioloških struktura i kao takvi su korisni za predviđanje ponašanja struktura kada su izložene opterećenjima. Iako su za sprovođenje takvih istraživanja često korišćene ekesperimentalne životinje, u novije vreme sve su češća takva istraživanja na matematičkim modelima. Pri tome primat ima metoda konačnih elemenata. Da bi se sprovelo istraživanje metodom konačnih elemenata potrebno je napraviti digitalni model strukture koja je predmet istraživanja. Jednom napravljen matematički digitalni model omogućuje primenom računara beskonačan broj promena oblika pojedinih elemenata i struktura, ali takođe i bezbroj simulacija aplikacija sila. Cilj ovog rada bio je prikazati način dobijanja trodimezionalnog modela zuba potrebnog za sprovođenje analiza ponašanja zuba nakon okluzalnog opterećenja metodom konačnih elemenata kao i proceniti mogućnost primene ove metode u biomehaničkim istraživanjima u veterinarskoj nauci. Na osnovu podataka iz literature, analizom morfologije ekstrahovanih zuba i plastičnih zuba u odgovarajućim kompjuterskim programima izvršeno je kreiranje sopstvenog modela intaktnog zuba. Posebno treba istaći da je MKE vrlo efikasan istraživački alat koji je preuzet iz inžinjerskih oblasti i ima potencijala za širu primenu u veterinarskoj nauci, posebno stomatologiji.

Unravelling the functional biomechanics of dental features and tooth wear

Most of the morphological features recognized in hominin teeth, particularly the topography of the occlusal surface, are generally interpreted as an evolutionary functional adaptation for mechanical food processing. In this respect, we can also expect that the general architecture of a tooth reflects a response to withstand the high stresses produced during masticatory loadings. Here we use an engineering approach, finite element analysis (FEA), with an advanced loading concept derived from individual occlusal wear information to evaluate whether some dental traits usually found in hominin and extant great ape molars, such as the trigonid crest, the entoconid-hypoconulid crest and the protostylid have important biomechanical implications. For this purpose, FEA was applied to 3D digital models of three Gorilla gorilla lower second molars (M2) differing in wear stages. Our results show that in unworn and slightly worn M2s tensile stresses concentrate in the grooves of the occlusal surface. In such condition, the trigonid and the entoconid-hypoconulid crests act to reinforce the crown locally against stresses produced along the mesiodistal groove. Similarly, the protostylid is shaped like a buttress to suffer the high tensile stresses concentrated in the deep buccal groove. These dental traits are less functional in the worn M2, because tensile stresses decrease physiologically in the crown with progressing wear due to the enlargement of antagonistic contact areas and changes in loading direction from oblique to nearly parallel direction to the dental axis. This suggests that the wear process might have a crucial influence in the evolution and structural adaptation of molars enabling to endure bite stresses and reduce tooth failure throughout the lifetime of an individual

Computer Aided Design Modelling and Finite Element Analysis of Premolar Proximal Cavities Restored with Resin Composites

This study evaluated the stress distribution in five different class II cavities of premolar models restored with conventional or bulk-fill flowable composite by means of finite element analysis (FEA) under shrinkage and occlusal loading. An upper validated premolar model was imported in the software, and five class II cavities with different occlusal extensions and dimensions were prepared: horizontal cavity on the mesial surface (horizontal slot), mesio-occlusal cavity, mesial cavity (vertical slot), tunnel type cavity and direct access cavity. The models were restored with conventional or bulk-fill flowable resin composite. The tested materials were considered as homogeneous, linear, and isotropic. The Maximum Principal Stress criteria was chosen to evaluate the tensile stress results. The lowest shrinkage stress value was observed in the direct access cavity restored with bulk-fill flowable resin composite (36.12 MPa). The same cavity, restored with conventional composite showed a score of 36.14 MPa. The horizontal slot cavity with bulk-fill flowable showed a score of 46.71 MPa. The mesio-occlusal cavity with bulk-fill flowable had a score of 53.10 MPa, while with conventional composite this was 55.35 MPa. Higher shrinkage stress was found in the vertical slot cavity with conventional resin 56.14 MPa, followed by the same cavity with bulk-fill flowable 56.08 MPa. Results indicated that the use of bulk-fill flowable composite resin more significantly decreased the polymerization shrinkage stress magnitude. The larger the cavity and the volume of material necessary to restore the tooth, the greater the residual stress on enamel and dentin tissue

An inhomogeneous and anisotropic constitutive model of human dentin

Dentin constitutes the major part of human tooth. It is composed of a large number of tubules with both variational radii and radially parallel pattern. In addition, peritubular dentin surrounds each tubule lumen and has a higher elastic modulus than the matrix of dentin, i.e. intertubular dentin. Considering the above microstructural characteristics, a micromechanics model is used in this paper to evaluate the overall elastic properties of dentin. Five independent effective elastic parameters in transverse isotropic elasticity matrix can be expressed analytically by the material parameters of peri- and intertubular dentin and the volume fraction of tubules. To determine the effectivity of this theoretical model, a finite element (FE) model simulating a longitudinal tooth slice in moir!e fringe testing of Wang and Weiner (J. Biomech. 31 (1998) 135) was performed. Furthermore, the FE model was developed incorporate modeling of variation of tubule’s diameter and softer characteristic of intertubular dentin near the dentin–enamel junction and around the pulp chamber. It turned out that the isoline figure of longitudinal displacement by FE calculation has very similar patterns to the moir!e fringe results. However, the FE results of displacement by traditional stress–strain models which regard dentin as a homogeneous and isotropic material show an obviously different strain distributions as compared to published moir!e fringes results. Thus the inhomogeneous and anisotropic model developed in this paper more accurately reflects the true physical nature of human dentin

A literature review on the linear elastic material properties assigned in finite element analyses in dental research

Introduction: Finite element analysis (FEA) is a numerical procedure utilised in the engineering analysis of structures and is one of the most common numerical methods utilised in many research activities in dentistry such as implantology, prosthodontics and restoration. FEA can be considered a useful tool in order to describe the deformation aspects of dental components that cannot be measured easily by in vivo models. The geometry, material properties, finite element model (mesh structure) and boundary conditions defined for a particular FEA setup are the factors affecting the accuracy of the results of a FEA. Most especially, material models employed in FEA play a critical role, however, the literature cannot provide standard material models and data in agreement to be defined in the FEA studies handled specifically for human teeth. The aim of this study is reviewing the most utilised data related to material properties (limited to linear homogeneous isotropic material model) of the tooth components, evaluate the sources and reasons for the different values defined in dental research and provide filtered material data which can be utilised in related FEA studies. Material and methods: Electronic databases (PubMed and Web of Science) were reviewed for publications on FEA utilised in dentistry research. 155 research publications in total were considered in this paper. The search keywords of “finite element analysis”, “finite element study”, “mechanical properties” and “teeth” were combined through Boolean operators. The primary question under review was: “How were the material properties of the tooth components and numerical ranges, which are assigned in a FEA utilised in dental research, obtained and verified?”. Results: It was possible to determine sixteen different elastic modulus (EM) and seven Poisson’ ratio (PR) values for enamel, eighteen EM and five PR values for dentin, sixteen EM and four PR values for periodontal ligament, eight EM and one PR values for pulp, ten EM and five PR values for cementum, twelve EM and four PR values for cortical bone, and eleven EM and four PR values for cancellous bone. As a result, it was seen that various EM, PR, density and strength values were considered and these were obtained from a limited number of FEA studies. Conclusion: Average ranges for the core material properties such as EM, PR, density and strength values to be utilised in a FEA set up were presented. Further studies, specifically on determination of the mechanical properties of tooth components are still needed in order to successfully utilise them and confirm the accuracy of the FEA studies related to dental research

Effect of fiber posts on stress distribution of endodontically treated upper premolars : finite element analysis

By means of a finite element method (FEM), the present study evaluated the effect of fiber post (FP) placement on the stress distribution occurring in endodontically treated upper first premolars (UFPs) with mesial–occlusal–distal (MOD) nanohybrid composite restorations under subcritical static load. FEM models were created to simulate four different clinical situations involving endodontically treated UFPs with MOD cavities restored with one of the following: composite resin; composite and one FP in the palatal root; composite and one FP in the buccal root; or composite and two FPs. As control, the model of an intact UFP was included. A simulated load of 150 N was applied. Stress distribution was observed on each model surface, on the mid buccal–palatal plane, and on two horizontal planes (at cervical and root-furcation levels); the maximum Von Mises stress values were calculated. All analyses were replicated three times, using the mechanical parameters from three different nanohybrid resin composite restorative materials. In the presence of FPs, the maximum stress values recorded on dentin (in cervical and root-furcation areas) appeared slightly reduced, compared to the endodontically treated tooth restored with no post; in the same areas, the overall Von Mises maps revealed more favorable stress distributions. FPs in maxillary premolars with MOD cavities can lead to a positive redistribution of potentially dangerous stress concentrations away from the cervical and the root-furcation dentin

FEM and Von Mises analysis on prosthetic crowns structural elements: evaluation of different applied materials

The aim of this paper is to underline the mechanical properties of dental single crown prosthodontics materials in order to differentiate the possibility of using each material for typical clinical condition and masticatory load. Objective of the investigation is to highlight the stress distribution over different common dental crowns by using computer-aided design software and a three-dimensional virtual model. By using engineering systems of analyses like FEM and Von Mises investigations it has been highlighted the strength over simulated lower first premolar crowns made by chrome cobalt alloy, golden alloy, dental resin, and zirconia. The prosthodontics crown models have been created and put on simulated chewing stresses. The three-dimensional models were subjected to axial and oblique forces and both guaranteed expected results over simulated masticatory cycle. Dental resin presented the low value of fracture while high values have been recorded for the metal alloy and zirconia. Clinicians should choose the better prosthetic solution for the teeth they want to restore and replace. Both prosthetic dental crowns offer long-term success if applied following the manufacture guide limitations and suggestions