An investigation of temperature and stress distribution on a restored maxillary second premolar tooth using a three-dimensional finite element method

Evaluation and Comparison of Stress Distribution in Restored Cervical Lesions of Mandibular Premolars: Three-dimensional Finite Element Analysis

Objectives:

Restorative materials are used in the treatment of cervical lesions and restoration of the dental tooth. The objective of this study was to assess the suitability of the three commonly used restorative materials by dentists and the evaluation of stress distribution and deformation using Von Mises stress in cervical lesions of mandibular premolars under varying loading condition.

Materials and Methods:

A computerized model of restored class V cavity of mandibular premolar tooth was created using three dimensional modeling software SpaceClaim. It was subjected to occlusal pressure load of 100, 150, 200 and 250MPa at right angle to buccal cusp and was analyzed for stress distribution and deformation in different restorative materials using Finite Element analysis, ANSYS Workbench.

Results:

The analysis carried on the class V restored tooth from biomechanical point of view indicates that restorative material glass–ionomer cement exhibited better bonding with the tooth structure using ionic bonds with the calcium ion present in the tooth structure. The variation of 8%–9% of stress concentration is observed in cavity region across varied pressure loads with glass–ionomer cement to Cention N.

Conclusion:

Glass–ionomer cement had showed better results than amalgam in terms of biomechanical property which is in agreement with the clinical findings. The stress values of Cention N were comparable to that of glass–ionomer cement.

Comparative Evaluation of Various Temperature Changes on Stress Distribution in Class II Mesial-occlusal-distal Preparation restored with Different Restorative Materials: A Finite Element Analysis

Introduction

The principal goal of dentistry is to maintain and improve the quality of life of the dental patients. As many of these objectives require the replacement or alterations of the existing tooth structure, the main challenge for centuries has been the development and selection of biocompatible materials that can withstand the unique conditions of the oral environment.

Finite element analysis (FEA) is a modern technique of numerical stress analysis that has become a solution to the task of predicting failure due to unknown stresses by showing problem areas in a material and allowing designers to see all of theoretical stresses within.

Aims and objectives

To evaluate and compare the effect of various temperature changes on the stress distribution, in class II mesial-occlusal-distal (MOD) cavity when restored with different restorative materials, using the finite element method (FEM).

Materials and methods

Using FEA, various thermal stresses generated in class II MOD lesion using different restorative materials were studied.

Results

The computer-generated models of intact tooth and teeth restored with the different restorative materials were designed, and thermal stress at different temperatures was observed when subjected to the thermal loads of 5°C, 20°C, 36°C, and 55°C. From the results of the study, it can be concluded that glass ionomer cement (GIC) performed best, followed by intact tooth, composite resin, silver amalgam, and zinc oxide eugenol cement.

Conclusion

Restoration of class II MOD lesions with materials of lower modulus of elasticity and lower coefficient of thermal expansion will enable better stress distribution.

How to cite this article: Srivastava B, Devi NN, Gupta N, Singh R. Comparative Evaluation of Various Temperature Changes on Stress Distribution in Class II Mesial-occlusal-distal Preparation restored with Different Restorative Materials: A Finite Element Analysis. Int J Clin Pediatr Dent 2018;11(3):167-170.

Thermal-stress analysis of ceramic laminate veneer restorations with different incisal preparations using micro-computed tomography-based 3D finite element models

Main objective of this study is to investigate the thermal behavior of ceramic laminate veneer restorations of the maxillary central incisor with different incisal preparations such as butt joint and palatinal chamfer using finite element method. In addition, it is also aimed to understand the effect of different thermal loads which simulates hot and cold liquid imbibing in the mouth. Three-dimensional solid models of the sound tooth and prepared veneer restorations were obtained using micro-computed tomography images. Each ceramic veneer restoration was made up of ceramic, luting resin cement and adhesive layer which were generated based on the scanned images using computer-aided design software. Our solid model also included the remaining dental tissues such as periodontal ligament and surrounding cortical and spongy bones. Time-dependent linear thermal analyses were carried out to compare temperature changes and stress distributions of the sound and restored tooth models. The liquid is firstly in contact with the crown area where the maximum stresses were obtained. For the restorations, stresses on palatinal surfaces were found larger than buccal surfaces. Through interior tissues, the effect of thermal load diminished and smaller stress distributions were obtained near pulp and root-dentin regions. We found that the palatinal chamfer restoration presents comparatively larger stresses than the butt joint preparation. In addition, cold thermal loading showed larger temperature changes and stress distributions than those of hot thermal loading independent from the restoration technique.

The Effects of Different Adhesive Agents on the Shear Bond Strength of a Self-Adhesive Resin Cement

Purpose

To compare the clinical success of a self-adhesive resin cement used in combination with different adhesive bonding systems with that of a conventional dual-cure resin cement.

Methods

The study was performed with 136 freshly extracted molars embedded in acrylic resin blocks and 136 IPS e.max Press discs. Teeth and discs were randomly divided into four equal groups and cemented together using either RelyX ARC (ARC), RelyX Unicem (Unicem), RelyX Unicem+Adper-Prompt L-pop (L-pop), or RelyX and Unicem+Total-etch (Total-etch). Shear bond strength measurements were obtained before and after thermocycling. Following bond testing, the surfaces of one sample per subgroup (thermocycled and non-thermocycled), were assessed using scanning electron microscopy (SEM).

Results

Among the non-thermocylced subgroups, ARC exhibited the highest bond strength values, followed by Total Etch, Unicem and L-pop. ARC also exhibited the highest bond strength values among the thermocycled subgroups, followed by Unicem, Total-etch, and L-pop. SEM analysis clearly revealed the negative effects of thermo-cycling on the mechanical properties of adhesive agents.

Conclusions

RelyX Unicem may be preferable in many cases because of its simplified application and reduced technique-sensitivity.

Finite element method--an effective research tool for dentistry

Stress analysis of dental structures has been a topic of interest in recent years with the objective of determination of stresses in the tooth and it's supporting structures and improvement of the mechanical strength of these structures. The purpose of this article is to give an insight of the finite element analysis which has totally overtaken other experimental analysis due to its ability to model even the most complex of geometries with is immensely flexible and adaptable nature. Finite Element Analysis (FEA) is a computer-based numerical technique for calculating the strength and behavior of structures. It can be used to analyze either small or large-scale deflection under loading or applied displacement. However it is extremely expensive and can be used only with the help of an expert engineer who has mastered this technique. Still this methodology of stress analysis has become extremely popular in dentistry as various properties of dental tissues and materials can be just fed into it and with the ease and accuracy the analysis is done is just remarkable.

Three-dimensional finite element thermal analysis of dental tissues irradiated with Er,Cr:YSGG laser

In the present study, a finite element model of a half-sectioned molar tooth was developed in order to understand the thermal behavior of dental hard tissues (both enamel and dentin) under laser irradiation. The model was validated by comparing it with an in vitro experiment where a sound molar tooth was irradiated by an Er,Cr:YSGG pulsed laser. The numerical tooth model was conceived to simulate the in vitro experiment, reproducing the dimensions and physical conditions of the typical molar sound tooth, considering laser energy absorption and calculating the heat transfer through the dental tissues in three dimensions. The numerical assay considered the same three laser energy densities at the same wavelength (2.79 microm) used in the experiment. A thermographic camera was used to perform the in vitro experiment, in which an Er,Cr:YSGG laser (2.79 microm) was used to irradiate tooth samples and the infrared images obtained were stored and analyzed. The temperature increments in both the finite element model and the in vitro experiment were compared. The distribution of temperature inside the tooth versus time plotted for two critical points showed a relatively good agreement between the results of the experiment and model. The three dimensional model allows one to understand how the heat propagates through the dentin and enamel and to relate the amount of energy applied, width of the laser pulses, and temperature inside the tooth.

Temperature excursions at the pulp-dentin junction during the curing of light-activated dental restorations

OBJECTIVES

Excessive heat produced during the curing of light-activated dental restorations may injure the dental pulp. The maximum temperature excursion at the pulp-dentin junction provides a means to assess the risk of thermal injury. In this investigation we develop and evaluate a model to simulate temperature increases during light-curing of dental restorations and use it to investigate the influence of several factors on the maximum temperature excursion along the pulp-dentin junction.

METHODS

Finite element method modeling, using COMSOL 3.3a, was employed to simulate temperature distributions in a 2D, axisymmetric model tooth. The necessary parameters were determined from a combination of literature reports and our measurements of enthalpy of polymerization, heat capacity, density, thermal conductivity and reflectance for several dental composites. Results of the model were validated using in vitro experiments.

RESULTS

Comparisons with in vitro experiments indicate that the model provides a good approximation of the actual temperature increases. The intensity of the curing light, the curing time and the enthalpy of polymerization of the resin composite were the most important factors. The composite is a good insulator and the greatest risk occurs when using the light to cure the thin layer of bonding resin or in deep restorations that do not have a liner to act as a thermal barrier.

SIGNIFICANCE

The results show the importance of considering temperature increases when developing curing protocols. Furthermore, we suggest methods to minimize the temperature increase and hence the risk of thermal injury. The physical properties measured for several commercial composites may be useful in other studies.

On the design of dental resin-based composites: a micromechanical approach

Adhesive resin-based restorative materials have the potential to considerably strengthen teeth and offer more economically viable alternatives to traditional materials such as gold, amalgam or ceramics. Other advantages are direct and immediate placement and the elimination of the use of mercury. However, polymerization shrinkage during curing of an adhesive restoration and mismatch in mechanical properties can lead to the initiation and development of interfacial defects. These defects could have a detrimental effect on the longevity of the restored tooth. The current study is focused on some design issues of resin-based composites affecting the longevity of the tooth-restoration interface. The theoretical approach is based on self-consistent micromechanical modelling that takes into account the effect of the material properties, volume concentration of the dispersed particle phase as well as the shape of these particles on the overall thermomechanical properties of the composite. Results obtained for resin-based composites reinforced with spherical, disc and short fibre particles highlight the advantages of disc shaped and short fibre particles.

Effect of material properties of composite restoration on the strength of the restoration-dentine interface due to polymerization shrinkage, thermal and occlusal loading

The purpose of this investigation was to adopt an analytical approach to analyse stresses at the restoration-dentine interface caused by polymerization shrinkage, occlusal and thermal loading with the primary focus on evaluating the effect of the material properties of the composite restoration on the strength of the interface. Some essential simplifications were employed to derive an explicit analytical solution. The results confirm previous findings that interfacial stresses due to polymerization shrinkage are increased with the higher modulus of elasticity of the restoration, while Poisson's ratio of the restorative material has a very small influence on these stresses. Occlusal loading resulted in much lower interfacial stresses when compared to shrinkage and thermal loads. The obtained results were in a good agreement with other numerical and clinical studies. From the modelling analysis it was found that the majority of commercially available composite restorative materials are expected to create significant interfacial stresses when subjected to cold temperatures. In addition, it was shown that there is a considerable potential for interfacial stresses to be minimised by an appropriate selection of thermo-mechanical properties of the restorative material especially with the new finding on the negative temperature variation effect.

Bond strength of a new universal self-adhesive resin luting cement to dentin and enamel

The objective of this study was to assess the bonding performance of a new universal self-adhesive cement RelyX Unicem (RXU) to dentin and enamel compared to four currently used luting systems, using a shear bond strength test with and without thermocycling. Median bond strengths were determined after 24 h storage, and after thermocycling (6,000 cycles, 5-55 degrees C) for RXU and compared to Syntac/Variolink II (SynC/V) as a standard for luting conventional ceramics, ED-Primer II/Panavia F2.0 (EDII/PF2), Prime and Bond NT/Dyract Cem Plus (PBNT/DyCP), and a glass ionomer cement, Ketac Cem (KetC), as a standard for luting high-strength ceramic and metal-based restorations. Data (n=10 per group) were statistically analyzed using the Mann-Whitney-Wilcoxon test at the 0.05 level of significance. The bond strength (MPa) of RXU to dentin (10.8) was not statistically different from those of SynC/V (15.1), EDII/PF2 (10.5) or PBNT/DyCP (10.1), and statistically higher than KetC (4.1). The bond strength of RXU to enamel (14.5) was significantly lower than those of SynC/V (32.8), EDII/PF2 (23.6), and PBNT/DyCP (17.8), but higher than KetC (6.1). After thermocycling, the bond strength of RXU to enamel significantly decreased, but was still significantly higher than that of KetC. RelyX Unicem may be considered an alternative to Ketac Cem for high-strength ceramic or metal-based restorations, and may be used for luting conventional ceramic crowns with little or no enamel left.

Finite element analysis of the temperature and thermal stress in a postrestored tooth

The finite element method was used to calculate temperature and thermal stress distribution as a result of hot/cold liquid in the mouth. This numerical study was carried out using axisymmetric finite element models and the tooth model was endodontically treated restored with cast post and cores. The two tooth models evaluated were Ti-Ti alloy and NiCr-AuPd alloy as post material and crown material with porcelain. First, temperature changes on the restored tooth as a result of hot/cold liquid in the mouth were calculated and then the thermal stress as a result of temperature changes were carried out. A fortran computer program was developed for this study. The tooth was assumed isotropic, homogenous, elastic and symmetrical. The distribution of temperature and thermal stress versus time were plotted for four critical points.

Temperature and thermal stress analysis of a crowned maxillary second premolar tooth using three-dimensional finite element method

The purpose of this study was to calculate the temperature and thermal stress distribution as a result of hot/cold liquid in the mouth. This numerical study was carried out using three-dimensional finite element models and the tooth model was crowned with Au-Pd alloy, Ni-Cr alloy and porcelain. In the first part of the study, temperature changes as a result of hot/cold liquid in the mouth were calculated. In the second part, the thermal stresses caused by temperature changes were obtained. The tooth was assumed isotropic, homogenous, elastic and unsymmetrical. The authors using fortran 77 prepared all calculation programs. The distribution of temperature and thermal stress were plotted for some critical points.