Chewing Loads Research Articles

Fabrication Technique of Dental Restoration Using Hybrid Ceramic With Cad Cam Method

Background : Ceramic is superior in aesthetic but fragile and breakable under bite pressure . Lack of understanding of material requirements for resistance in the oral cavity and minimal ceramic processing techniques is the initial cause of the failure. Hybrid ceramic dental restoration is a material that combines the good properties of ceramics and composites that have elasticity and ensures high strength and minimize the wall thickness of the restoration. Mechanical manufacture of dental restorations currently growing, CAD CAM systems are becoming popular in the field of dentistry. CAD CAM provides the advantage that the effectiveness of the time, does not require a lot of human resources, and produce a restoration with good quality. Purpose: To explain hybrid ceramic material and techniques of making hybrid ceramic dental restorations with CAD CAM system. Review: Hybrid ceramic is a material that combines the advantages of ceramics and composite elasticity. This material contains a hybrid structure with two networks, ceramic and polymer are linked to each other, known as double hybrid network. It added that the structure of the ceramic feldspathic network (86% wt) is reinforced by a polymer network (14% wt) are integrated as a polymer network filling cavities that exist in the network and make its structure ceramic hybrid ceramic material becomes denser. Conclusion: Hybrid ceramic having chewing load capacity and high elasticity, flexural strength 150-160 Mpa and fracture toughness 1.5 Mpa, higher than conventional ceramics. Mechanical manufacture of dental restorations using ceramic hybrid materials with CAD CAM method begins with scanning, selection of materials and tooth shade, designing, milling, followed by finishing, polishing, ends with staining and glazing.

Computer Assisted Design and Analysis of Customized Porous Plate for Mandibular Reconstruction

BackgroundThe reconstruction of large mandibular defects using commercial available reconstruction plates often leads to complications. The application of computer aided design technologies together with advanced medical imaging (CT/MRI) is gaining increased attention in reconstructive surgeries. Studies have proved that implants with porous structures can effectively enhances the biological fixation of the bone. However, no study has been reported on the design and analysis of the customized porous mandibular reconstruction. ObjectiveThe objective of this study is to present an integrated framework model for the design and analysis of customized porous reconstruction plate based on the selection of implant design techniques. MethodIn this study two customized implant design techniques (mirroring/anatomical) are compared and the best design is selected based on the surface deviation. A 3D finite element analysis was performed on the selected implant design model to evaluate its biomechanical response under chewing conditions. ResultsThe finite element simulated results reveal that the designed porous plate can withstand the chewing load conditions and provides good stability. The maximum stresses developed on the reconstruction plate (360 MPa) and screws (122.90 MPa) are significantly less and within the failure limit of implant material. ConclusionBased on the results, it is recommended to use mirror design reconstruction technique in repair of mandibular bone which can effectively improve the stability and flexibility of mandibular reconstruction under chewing conditions.

Optimal selection of dental implant for different bone conditions based on the mechanical response.

Bone quality varies from one patient to another extensively. Young's modulus may deviate up to 40% of normal bone quality, which results into alteration of bone stiffness immensely. The prime goal of this study is to design the optimum dental implant considering the mechanical response at bone implant interfaces for a patient with specific bone quality. 3D models of mandible and natural molar tooth were prepared from CT scan data, while dental implants were modelled using different diameter, length and porosity and FE analysis was carried out. Based on the variation in bone density, five different bone qualities were considered. First, failure analysis of implants, under maximum biting force of 250 N had been performed. Next, the implants that remained were selected for observation of mechanical response at bone implant interfaces under common chewing load of 120 N. Maximum Von Mises stress did not surpass the yield strength of the implant material (TiAl4V). However, factor of safety of 1.5 was considered and all but two dental implants survived the design stress or allowable stress. Under 120 N load, distribution of Von Mises stress and strain at the boneimplant interface corresponding to the rest of the implants for five bone conditions were obtained and enlisted. Implants exhibiting interface strain within 1500-3000 microstrain range show the best bone remodelling and osseointegration. So, implant models having this range of interface strains were selected corresponding to the particular bone quality. A set of optimum dental implants for each of the bone qualities were predicted.

Simulations of cast and selective laser melted dental bridges with chewing load

The aim of the present paper is to evaluate and compare the strength properties and deformation characteristics of cast and Selective Laser Melted (SLM) Co-Cr dental alloys by using CAD/CAE software. The Solid Works Simulation software is used for simulation of chewing loading of the virtual 3D model of four-part dental bridge. Two Co-Cr dental alloys, cast and SLM were used in this study. During simulation process by means of linear static analysis the displacements, strains, stresses, and reaction forces under the effect of the applied load were calculated. As a result, the equivalent von Mises stresses, Factor Of Safety (FOS) and displacements were evaluated in this study. It was established that the highest values of the equivalent von Mises stresses of cast and SLM bridges are situated in the connectors between the teeth, i.e. the zones with the lowest areas of the cross sections. They are in the range 95-162 MPa, which is lower than the stress limits for the both materials. The minimum FOS of the both materials is higher than 1. In the cast bridges it is 1.32-2.64 in the zones with the highest loading, while in the SLM samples it is 2.61-5.68. As FOS shows the reserve strength of the material for the applied load, it is obvious that the SLM bridge possesses twice higher reserve strength. This allows optimization of the construction, economy of material and possibility for manufacturing of objects with porous structures.

Importance of the variable periodontal ligament geometry for whole tooth mechanical function: A validated numerical study

When mammalian teeth breakdown food, several juxtaposed dental tissues work mechanically together, while balancing requirements of food comminution and avoiding damage to the oral tissues. One important way to achieve this is by channeling mastication forces into the surrounding jaw bone through a thin and compliant soft tissue, the periodontal ligament (PDL). As a result, during a typical chewing stroke, each tooth moves quite substantially in its anchor-site. Here we report a series of experiments, where we study the reaction of three-rooted teeth to a single chewing event by finite element (FE) modelling. The nonlinear behaviour of the PDL is simulated by a hyperelastic material model and the in silico results are validated by our own in vitro experiments. We examine the displacement response of the complete tooth-PDL-bone complex to increasing chewing loads. We observe that small spatially-varying geometric adjustments to the thickness of the PDL lead to strong changes in observed tooth reaction movement, as well as PDL strain and bone stress. When reproducing the regionally varying thickness of the PDL observed in vivo, FE simulations reveal subtle but significant tooth motion that leads to an even distribution of the stresses in the jaw bone, and to lower strains in the PDL. Our in silico experiments also reproduce the results of experiments performed by others on different animal models and are therefore useful for overcoming the difficulties of obtaining tooth-PDL-bone loading estimates in vivo. This data thus enhances our understanding of the role the variable PDL geometry plays in the tooth-PDL-bone complex during mastication.

유한요소법을 이용한 치과 임플란트 고정체의 직경과 길이에 따른 지지골의 응력 분석

Purpose: The dental implant should be enough to endure chewing load and it's required to have efficient design and use of implant to disperse the stress into bones properly. This study was to evaluate the stress distribution on a supporting bone by lengths and diameters of the implant fixture. Methods: The modeling and analysis of stress distribution was used for the simple molar porcelain crown model by Solidworks as FEM program. It was designed on applying with tightening torque of 20 Ncm of a abutment screw between a cement retained crown abutment and a fixture. The fixtures of experimental model used 10, 13mm by length and 4, 5mm by diameter. A external vertical loading on the two buccal cusps of crown and performed finite element analysis by 100 N. Results: The maximum von Mises stress(VMS) of all supporting bone models by fixture length and diameter were concentrated on the upper side of supporting compact bone. The maximum stress of each model under vertical load were 164.9 MPa of M410 model, and 141.2 MPa of M413 model, 54.3 MPa of M510 model, 53.6 MPa of M513 model. Conclusion: The stress reduction was increase of fixture's diameter than it's length. So it's effective to use the wider fixture as possible to the conditions of supporting bone.

The interplay between increased tooth crown-height and chewing efficiency, and implications for Cervidae evolution

Mammals of numerous lineages have evolved high-crowned (hypsodont) teeth particularly during the last 20 million years. This major phenotypic change is one of the most widely studied evolutionary phenomena in a broad range of disciplines, though the mechanisms underlying its transformation remain unresolved. Here, we present the first Finite Element Analysis (FEA) to investigate the alternative hypothesis that there is a biomechanical link between increased hypsodonty and a more effective mastication in deer. Our FE experiments compared patterns of stress and strain within and between different fossil and living species under different loading conditions, and found that more hypsodont teeth are suited for restricting stresses to those areas where chewing loading occurs. This mechanical improvement is consequence of specific and pronounced variations in tooth geometry and morphology of the occlusal surface that are strongly related to crown growth in the vertical plane. We demonstrate that hypsodonty enables selenodont-teeth to adopt a mechanically improved design that increases the pressure whilst shearing foods. As ruminants are physiologically limited by both the quantity of food consumed and the time spent in the mastication and digestion, hypsodonty is highly advantageous when feeding on mechanically resistant, tough and fibrous foods. Consequently, it allows grass-eaters to spend less time chewing, thereby increasing the volume of food ingested and/or providing more time for digestion. This study provides a promising line of evidences in support of biomechanical effectiveness, in addition to or instead of increased wear resistance, as a factor in explaining the evolutionary origins of the hypsodont phenotype.

A comparative study on the customized design of mandibular reconstruction plates using finite element method

Mandible defects and its deformities are serious complications and its precise reconstruction is one of the most challenging tasks in oral maxillofacial surgery. The commercially available standard mandible implants are manually bended before surgery to custom fit the patient’s jaw. A slight mismatch in the plate and bone alignment may result in the implant failure. However, with the integration of computer-aided design, rapid prototyping, and advanced imaging systems (computed tomography or magnetic resonance imaging), it is possible to produce a customized mandible implant that can precisely fit the patient’s jaw. The aim of this article is to compare a new design of customized mandible implant (sinewave plate) and compare it with the commonly used straight implant design. The finite element–simulated results reveal that the commonly used straight reconstruction plates are more prone to loosening of the screws due to its higher strain concentration on the screw hole when compared to newly designed sinewave reconstruction plate. Moreover, the straight plate is more sensitive to the chewing load variations and develops almost 20% increase in the stresses when compared to sinewave plate. The study reveals that the sinewave reconstruction plate can significantly enhance the stability and safety of the mandible implant.

Mechanical properties of resin glass fiber-reinforced abutment in comparison to titanium abutment.

Purpose:So far, definitive implant abutments have been performed with high elastic modulus materials, which prevented any type of shock absorption of the chewing loads and as a consequence, the protection of the bone-fixture interface. This is particularly the case when the esthetic restorative material chosen is ceramic rather than composite resin. The adoption of an anisotropic abutment, characterized by an elastic deformability, could allow decreasing the impulse of chewing forces transmitted to the crestal bone.Materials and Methods:According to research protocol, the mechanical resistance to cyclical load was evaluated in a tooth-colored fiber-reinforced abutment (TCFRA) prototype and compared to that of a titanium abutment (TA), thus eight TCFRAs and eight TAs were adhesively cemented on as many titanium implants. The swinging that the two types of abutments showed during the application of sinusoidal load was also analyzed.Results:In the TA group, both fracture and deformation occurred in 12.5% of samples while debonding 62.5%. In the TCFRA group, only debonding was present in 37.5% of samples. In comparison to the TAs, the TCFRAs exhibited a greater swinging during the application of sinusoidal load. In the TA group, the extrusion prevailed, whereas in the TCFRA group, the intrusion was more frequent.Conclusion:The greater elasticity of TCFRA to the flexural load allows absorbing part of the transversal load applied on the fixture during the chewing function, thus reducing the stress on the bone-implant interface.

UNIFORM DESIGN AND DYNAMIC FINITE ELEMENT ANALYSIS FOR MICROMOTION IMPROVEMENT OF SEMADOS DENTAL IMPLANT SYSTEM UNDER DYNAMIC CHEWING LOADS

This study aimed to improve the micromotion of a Semados dental implant system subjected to dynamic chewing loads. Micromotion of the Semados dental implant system with basic dimensions was obtained using dynamic finite element analysis, and five parameters of the implant were selected as the control factors to be improved. A uniform design method was employed to construct a set of experimental simulations. Next, for each experimental simulation, the dynamic finite analysis package ANSYS/LS-DYNA was employed to simulate the behavior of the Semados dental implant model subjected to dynamic chewing loads and then determine the maximum micromotion of the cortical and cancellous bones. Finally, the best design of the experimental simulations that caused the smallest amount of micromotion was selected as the improved design version. Compared to the original design, which experienced micromotion of 74.53 μm, the improved version experienced micromotion of 45.41 μm. The rate of improvement was 39.1%.

Application of Uniform Design and Kriging Interpolation in Optimization of ITI Dental Implant with Dynamic Chewing Loads

The aim of this paper is to present an integrated procedure for the optimization of dimensions of the ITI dental implant with dynamic chewing loads. The procedure is composed of uniform design of experiments, explicit dynamics finite element analysis, Kriging interpolation, and Nelder-Mead simplex local search optimization method. Firstly, uniform design method is employed to create a set of experiments. Then, explicit dynamics finite element analysis software ANSYS/LS-DYNA is used to analyze the micromotion of cortical and cancellous bones while the dynamic chewing loads acts on the implant. Next, Kriging interpolation is applied to construct the surrogate model of micromotion based on the input and output data of experiments. Finally, Nelder-Mead simplex local search method is applied to find the optimal solution of dimensions of dental implant under the goal of minimizing the micromotion. After performing the optimization procedure presented in this paper, the micromotion of the ITI dental implant system model can successfully be reduced by a rate of 29.7 %.

A three - dimensional finite element study on the stress distribution pattern of two prosthetic abutments for external hexagon implants

Objective:The purpose of this study was to evaluate the mechanical behavior of two different straight prosthetic abutments (one- and two-piece) for external hex butt-joint connection implants using three-dimensional finite element analysis (3D-FEA).Materials and Methods:Two 3D-FEA models were designed, one for the two-piece prosthetic abutment (2 mm in height, two-piece mini-conical abutment, Neodent) and another one for the one-piece abutment (2 mm in height, Slim Fit one-piece mini-conical abutment, Neodent), with their corresponding screws and implants (Titamax Ti, 3.75 diameter by 13 mm in length, Neodent). The model simulated the single restoration of a lower premolar using data from a computerized tomography of a mandible. The preload (20 N) after torque application for installation of the abutment and an occlusal loading were simulated. The occlusal load was simulated using average physiological bite force and direction (114.6 N in the axial direction, 17.1 N in the lingual direction and 23.4 N toward the mesial at an angle of 75° to the occlusal plan).Results:The regions with the highest von Mises stress results were at the bottom of the initial two threads of both prosthetic abutments that were tested. The one-piece prosthetic abutment presented a more homogeneous behavior of stress distribution when compared with the two-piece abutment.Conclusions:Under the simulated chewing loads, the von Mises stresses for both tested prosthetic-abutments were within the tensile strength values of the materials analyzed which thus supports the clinical use of both prosthetic abutments.

Finite element analysis of multi-piece post-crown restoration using different types of adhesives

The multi-piece post-crown technique is more effective in restoring residual root than other restoration techniques. Various types of adhesives have different material properties that affect restoration. Therefore, the choice of adhesive is particularly important for patients. However, the effect of different kinds of adhesives was not too precise by experimental methods when concerning about individual differences of teeth. One tooth root can only be restored with one type of adhesive in experiment. After the mechanical test, this tooth root cannot be restored with other adhesives. With the help of medical imaging technology, reverse engineering and finite element analysis, a molar model can be reconstructed precisely and restored using different types of adhesives. The same occlusal and chewing loads were exerted on the same restored residual root models with different types of adhesives separately. Results of von Mises stress analysis showed that the adhesives with low Young's modulus can protect the root canal effectively. However, a root canal concentration is apparently produced around the root canal orifice when chewing. Adhesives with large Young's modulus can buffer the stress concentration of the root canal orifice. However, the root canal tissue may be destroyed because the adhesive is too hard to buffer the load.

Increased sternocleidomastoid, but not trapezius, muscle activity in response to increased chewing load

Previous findings, during chewing, that boluses of larger size and harder texture result in larger amplitudes of both mandibular and head-neck movements suggest a relationship between increased chewing load and incremental recruitment of jaw and neck muscles. The present report evaluated jaw (masseter and digastric) and neck [sternocleidomastoid (SCM) and trapezius] muscle activity during the chewing of test foods of different sizes and textures by 10 healthy subjects. Muscle activity was recorded by surface electromyography and simultaneous mandibular and head movements were recorded using an optoelectronic technique. Each subject performed continuous jaw-opening/jaw-closing movements whilst chewing small and large boluses of chewing gum and rubber silicone (Optosil). For jaw opening/jaw closing without a bolus, SCM activity was recorded for jaw opening concomitantly with digastric activity. During chewing, SCM activity was recorded for jaw closing concomitantly with masseter activity. Trapezius activity was present in some, but not all, cycles. For the masseter and SCM muscles, higher activity was seen with larger test foods, suggesting increased demand and recruitment of these muscles in response to an increased chewing load. This result reinforces the previous notion of a close functional connection between the jaw and the neck motor systems in jaw actions and has scientific and clinical significance for studying jaw function and dysfunction.

Effect of preloading on lower jaw implant

The procedure of mandible resection is basically unavoidable in case of cancer in the field of oral surgery. The reinforcement and the reconstruction of the jaw closest to its original condition is very challenging. Considering the load properties the examination of the plates used in the reconstruction is highly important. The cadaver examination procedure however is very difficult to execute, therefore the use of the Finite Element Analysis proves rather supportive. Fast recovery can be achieved by applying the implants correctly. Furthermore brakeage resulting from high loads in the plates can be avoided. The goal is to examine and understand the Non-locking screwing technique used with plate implants in different mandible resections and reconstructions, focusing on the preloaded force. Furthermore the study and comparison of different stress that arise in different cases. A toothless mandible was used for the creation of the Finite Element Analysis model. The data was provided for the model by CBCT. During the creation of the model we separated four different resection areas to which we used the plates with the Non-Locking screwing technique, also used in clinical reconstructions. For the preload of the plates we used different preloaded forces on the screws. We considered and used boundary conditions complying with the anatomical structure. The muscles required for chewing were transferred to the model and used as main loads. The bone structure is heterogenic and the bone density is based on CBCT. The preloaded forces have a major role in the stresses arising in the bone during the use of Non-locking technique. The comparison of the resection techniques can provide valuable information regarding the preloaded condition and the following chewing load condition connected to the main loads in the bone. Those measurements that are important from biomechanical point of view and would prove difficult or impossible with in vivo or in vitro load measurements to be examined can be compared with the Finite Element Analysis method. DOI: 10.17489/biohun/2013/1/03

RESTORASI PASAK FIBER DAN PORCELAIN FUSED TO METAL PADA FRAKTUR GIGI INSISIF RAHANG ATAS PASCA PERAWATAN ENDODONTIK

Teeth with is treated with endodontic treatment has own problems, tends to be weaker because of dentin removal and reduced moisture content, so, requires post and crown restoration treatment. The principle of making restoration should be to restore function, esthetic, and to distribute chewing load, so, both teeth and its crown can be used in a long time in oral cavity. This case report described about 23-year-old female patient with a history of truma motor vehicle accident. Tooth 11,12,21 was fractured 2/3 crown with pulp exposed. The diagnosis which estabilished for this case is irreversible pulpitis and the treatment planning are one visit root canal treatment, post and fiber insertion and porcelain fused to metal restoration. On the first visit, acces preparation with crown down technique was done and rootcanals filled with gutta percha and sealer AH 26 with lateral condensation technique. Fiber post was insertion in next visit and cementation with dual-cured resin. Core was made in resin composite and porcelain fused to metal was inserted after control of patient condition in 1 week. One of those methods that used in this case is prefabricated glass fiber post, because of its biocompatibility, more aesthetic, has a modulus of elasticity which is resemble with dentine. Pressure that its transmitted by post to dentin is low, so, this is minimize a root fractured. The result of this treatment and the restoration was good, there were no patient complaints, and normal gingival seemed around the teeth. Restoration post endodontic treatment can be done with several techniques, one is post and porcelain fused to metal to produce a good restoration.

Luting of ceramic crowns with a self-adhesive cement: Effect of contamination on marginal adaptation and fracture strength

Objectives: This study evaluated the percentages of continuous margins (%CM) and fracture strength (FS) of crowns made out from blocs of leucite-reinforced ceramic (IPS Empress CAD) and luted with a representative self-adhesive cement (RelyX Unicem) under four contaminating agents: saliva, water, blood, a haemostatic solution containing aluminium chloride (pH= 0.8) and a control group with no contamination. Study Design: %CM at both tooth-cement (TC) and cement-crown (CC) interfaces were determined before and after a fatigue test consisting of 600’000 chewing loads and 1’500 temperature cycles changing from 5º C to 50º C. Load to fracture was recorded on fatigued specimens. Kruskal-Wallis test was used to compare %CM and FS between the five groups with a level of confidence of 95%. Results: At the TC interface, no significant differences in marginal adaptation before loading could be detected between groups. After loading, a significant marginal degradation was observed in the group contaminated with aluminium chloride (52 ± 22 %CM) in respect to the other groups. No significant differences in %CM could be detected between the groups contaminated with saliva, water, blood and the control. At the CC interface, no significant differences in marginal adaptation were observed between the groups. The FS on loaded specimens was around 1637N, with no significant differences between groups as well. Conclusions: An adverse interaction of the highly acidic haemostatic agent with either dentin or the self-adhesive cement could explain the specimens’ marginal degradation. The self-adhesive cement tested in this study was no sensitive to moisture contamination either with saliva, water or blood. Key words:Marginal adaptation, RelyX Unicem, contamination, all-ceramic crowns.

Finite element analysis of an ultra-fine grained Titanium dental implant covered by different thicknesses of hydroxyapatite layer

Background/AimsCoating dental implants with hydroxyapatite (HA) layer has been widely used in last decades due to its numerous advantages. Stress concentration in the implant is an essential factor as it can cause the fracture of the implant. MethodsWe compared the effect of different thicknesses of hydroxyapatite layer on stress concentration in a nano-Titanium dental implant with finite element method (FEM) software under 200 N axial chewing load applied on the top of the implant in order to see which one has the lowest stress concentration and is best for dental applications. Results and conclusionThe results show that the best thickness of the hydroxyapatite layer is 180 μm which minimizes the stress concentration in bone and maximizes the life of the implant.

Alveolar bone changes in autogenous tooth transplantation

To assess the alveolar bone formation after autogenous tooth transplantation by conventional radiographic method and digital subtraction radiography. This retrospective study was done in 54 of 136 patients who received the third molar tooth transplantation and attended the first week, as well as the 1-, 3-, 6-, 9-, and 12-month follow-up. Postoperative periapical radiographs were subsequently evaluated by direct visual interpretation and digital subtraction radiography. The data were analyzed by using McNemar test and 1-way repeated-measure analysis of variance as well as Bonferroni multiple comparison. Fifty-four cases of transplantation were studied. Most of them had normal wound healing. The direct radiographic interpretation and digital subtraction radiography found significant alveolar bone formation in the first-and the third-month follow-ups (P < .05). Lamina dura appeared in the third month and kept increasing until the sixth month. Postoperative radiographs revealed the distinctive bone formation up to the third month. The clinical and radiographic assessment found that the third molar transplants could bear a normal chewing load within 3 months.

The use of a masticatory robot to analyze the shock absorption capacity of different restorative materials for implant prosthesis

The aim of the present research was to measure in vitro the chewing load forces transmitted through crowns made of different prosthetic restorative materials onto the dental implant. A masticatory robot that is able to reproduce the mandibular movements and the forces exerted during mastication was used. The forces transmitted to the simulated periimplant bone during the robot mastication were analysis of variance (ANOVA) was used. The zirconia and the ceramic crowns transmitted significantly greater forces (p-value &lt; 0.0001) than the other crowns tested. Dental materials with lower elastic modulus were better able to ansorb shock from acclusal forces than more rigid materials.