Elastic Modulus Of Dentin Research Articles

High Performance Composites Based on Highly Filled Glass Fiber-Reinforced Polybenzoxazine for Post Application

Glass fiber post based on the new polymeric material, polybenzoxazine, is prepared and the effects of glass fiber contents on mechanical and thermal properties are evaluated. The mechanical response to externally applied loads of tooth restored with glass fiber-reinforced polybenzoxazine composite posts is also simulated by finite element analysis of a tridimensional model and compared with the response to that of a natural tooth. The reinforcing of glass fiber can help improve the mechanical and thermal properties of the polybenzoxazine influenced by the interfacial adhesion between the glass fiber and polybenzoxazine matrix, except for the relatively high mechanical property of the glass fiber. The mechanical data, i.e., elastic modulus under flexure load or flexural modulus by three-point bending test of the glass fiber-reinforced polybenzoxazine composites are agreed with the elastic modulus of dentin and then used in the finite element model. The restoration using the glass fiber-reinforced polybenzoxazine composite post provided the maximum von Mises equivalent stress at the cervical third area of the endodontically treated tooth model as similarly observed in the natural tooth. In addition, the maximum von Mises equivalent stress of the tooth restored with the glass fiber-reinforced polybenzoxazine composite post is also quietly like that of the natural tooth. The finding of this work provided the essential properties of the glass fiber-reinforced polybenzoxazine composite for dental restorations and appliances.

The effect of different irrigation protocols on elastic modulus of dentine and biomechanics of single-rooted premolar tooth: A nano-indentation and finite element analysis study.

This study evaluated the effect of different irrigation protocols on elastic modulus and biomechanics of single-rooted premolar tooth using with nano-indentation and finite element analysis (FEA). Root canals of single-rooted human teeth were prepared, divided into eight groups, and irrigated with (1) 2.5% NaOCl + 17% EDTA; (2) 2.5% NaOCl + 17% EDTA + 2.5% NaOCl; (3) 2.5% NaOCl + SmearClear; (4) 2.5% NaOCl + 2% chlorhexidine; (5) 1.3% NaOCl + MTAD; (6) 5.25% NaOCl; (7) 17% EDTA; and (8) saline. The roots were vertically sectioned, and elastic modulus of the root dentine was measured using nano-indenter device at coronal, middle, and apical third. Data were recorded as megapascal and statistically analyzed (one-way analysis of variance, Tukey tests). Three-dimensional FEA model of a premolar tooth was created, and the inner root dentine was modified to simulate the effect of irrigation protocols on root dentine. The elastic properties of inner root dentine layer in the FEA models were modified for each group according to the data obtained with nano-indentation. A 300-N load was applied at the buccal cusp and central fossa of the models with a 45° angle. The stresses were calculated using von Mises stress criteria. All irrigation protocols affected the elastic modulus of root dentine. Groups 2 and 3 showed similar elastic modulus values (P > 0.05), whereas the lowest values were obtained in group 7 (P < 0.05). No statistically significant differences were found between groups 4, 5, and 8 (P > 0.05). Despite the effect of different clinically used irrigation protocols on elastic modulus of the inner dentine, this does not affect the biomechanics of the roots.

A comparative study of stress distribution between glass fiber post and cast post in an endodontically treated central incisor – A finite element analysis

Background: Endodontically treated teeth with severe loss of tooth structure require post and core restorations for retention purposes. The post system includes components of different rigidity because the rigid component is able to withstand forces without distortion and the stress is transferred to less rigid substrate. The difference between the elastic modulus of dentin and the post material may be a source of stress for root structures. The use of post systems that have an elastic modulus similar to that of dentin result in the creation of a mechanically homogenous unit with better biomechanical performance. Thus the post and core material affects stress distribution in endodontically treated teeth.Aims and Objectives: In this study, FEA is used to evaluate the fracture resistance in an endodontically treated maxillary central incisor that was restored with two different post systems – 1) prefabricated glass fiber post and 2) custom made cast post. The qualitative stress distribution analyses were recorded by von Mises criteria. Results: von Mises stress in an intact tooth was concentrated in the crown near the cingulum under oblique load and on the incisal edge with vertical load. With horizontal load- In the crown region, maximum von Mises stress was observed in both the cast post and fiber post. Within the post region, maximum von Mises stress was observed in cast post when compared to fiber post. In the root dentin, more von Mises stress was observed in fiber post when compared to cast post. Conclusion: 1)Stress distribution is similar between cast post and fiber post during vertical load. 2)Cast metal post dissipates less stress to the dentin and gives better fracture resistance to the tooth when compared to glass fiber post during oblique loading. When considering the stress pattern, maximum stress was observed in the cervical region of the crown and in the area of load application during oblique and vertical loading.

Effect of radiotherapy on resin composite adaptation to the cavity wall and elastic modulus of dentin

Effect of radiotherapy on resin composite adaptation to the cavity wall and elastic modulus of dentin

Effect of polar solvents on the elastic modulus of dentin

Effect of polar solvents on the elastic modulus of dentin

Bonding of Adhesive Luting Agents to Caries-affected Dentin Induced by a Microcosm Biofilm Model.

To evaluate the bond strength of adhesive luting agents applied to caries-affected dentin (CAD). Thirty-six noncarious human third molars were abraded to expose an occlusal dentin surface. Caries lesions were induced in half of the samples using a microcosm biofilm model. Biofilm was cultivated under an anaerobic atmosphere for 14 days in a medium enriched with mucin. The same medium containing 1% sucrose was alternated for 4 hours per day. Cylinders of resin cement (RelyX ARC, RelyX U200, or BisCem) were built up over the dentin substrate and submitted to shear bond load. The samples were then longitudinally sectioned. The hardness and elastic modulus of dentin were measured at different depths from the occlusal surface. A three-dimensional finite element simulation was performed to analyze the residual stress distribution during the shear bond strength test. Bond strength data were analyzed by two-way analysis of variance (ANOVA) and hardness and elastic modulus by split-plot ANOVA. Multiple comparisons were performed with the SNK test (α=0.05). For all cements, the highest bond strengths were observed in sound dentin. Relyx ARC bond strength was similar to that of RelyX U200 for both substrates; BisCem had the lowest values. CAD had lower hardness (above a depth of 100 μm) and elastic modulus (above a depth of 150 μm) values than sound dentin. Stress distribution during the bond strength test was similar under all experimental conditions. Impairment of the mechanical properties of dentin promoted by carious lesions reduced the bond strength of adhesive luting agents.

Bonding of adhesive luting agents to caries-affected dentin

Purpose: This study evaluated the bond strength of adhesive luting agents applied to caries-affected dentin (CAD). Methods and materials: Thirty-six non-carious human third molars were abraded to expose an occlusal dentin surface. Caries lesions were induced in half of the samples using a microcosm biofilm model. Biofilm was cultivated under an anaerobic atmosphere for 14 days in a medium enriched with mucin. The same medium containing 1% sucrose was alternated for 4h per day. Cylinders of resin cement (RelyX ARC, RelyX U200 or BisCem) were built up over the dentin substrate and submitted to shear bond load. The samples were then longitudinally sectioned. The hardness and elastic modulus of dentin was measured at depths of 10, 20, 30, 40, 50, 100, 150 and 200 m from the occlusal surface. A three-dimensional finite element simulation was performed to analyze the residual stress distribution for each experimental condition during the shear bond strength test. Bond strength data were analyzed by two-way ANOVA and hardness and elastic modulus by split-plot ANOVA. Multiple comparisons were performed with the Student–Newman–Keuls test (a=0.05). Results: Independent of the type of cement, the highest bond strengths were observed in sound dentin. Relyx ARC bond strength was similar to that of RelyX U200 for both substrates; BisCem had the lowest values. CAD had lower hardness values than sound dentin above a depth of 100 m. Elasticmodulus exhibited a similar trend, but above a depth of 150 m. Stress distribution during the bond strength test was similar under all experimental conditions. Conclusion: Impairment of the mechanical properties of dentin promoted by carious lesions reduced the bond strength of adhesive luting agents.

Alteration of dentin–enamel mechanical properties due to dental whitening treatments

The mechanical properties of dentin and enamel affect the reliability and wear properties of a tooth. This study investigated the influence of clinical dental treatments and procedures, such as whitening treatments or etching prior to restorative procedures. Both autoclaved and non-autoclaved teeth were studied in order to allow for both comparison with published values and improved clinical relevance. Nanoindentation analysis with the Oliver–Pharr model provided elastic modulus and hardness across the dentin–enamel junction (DEJ). Large increases were observed in the elastic modulus of enamel in teeth that had been autoclaved (52.0 GPa versus 113.4 GPa), while smaller increases were observed in the dentin (17.9 GPa versus 27.9 GPa). Likewise, there was an increase in the hardness of enamel (2.0 GPa versus 4.3 GPa) and dentin (0.5 GPa versus 0.7 GPa) with autoclaving. These changes suggested that the range of elastic modulus and hardness values previously reported in the literature may be partially due to the sterilization procedures. Treatment of the exterior of non-autoclaved teeth with Crest Whitestrips™, Opalescence™ or UltraEtch™ caused changes in the mechanical properties of both the enamel and dentin. Those treated with Crest Whitestrips™ showed a reduction in the elastic modulus of enamel (55.3 GPa to 32.7 GPa) and increase in the elastic modulus of dentin (17.2 GPa to 24.3 GPa). Opalescence™ treatments did not significantly affect the enamel properties, but did result in a decrease in the modulus of dentin (18.5 GPa to 15.1 GPa). Additionally, as expected, UltraEtch™ treatment decreased the modulus and hardness of enamel (48.7 GPa to 38.0 GPa and 1.9 GPa to 1.5 GPa, respectively) and dentin (21.4 GPa to 15.0 GPa and 1.9 GPa to 1.5 GPa, respectively). Changes in the mechanical properties were linked to altered protein concentration within the tooth, as evidenced by fluorescence microscopy and Fourier transform infrared spectroscopy.

An Evaluation of the Effect of Non-Setting Calcium Hydroxide on Human Dentine: A pilot Study

To evaluate the effect of non-setting calcium hydroxide (NSCH) on the hardness and elastic modulus of dentine from extracted permanent premolar human teeth. 30 freshly extracted single rooted human premolar teeth were decoronated and the roots then sectioned longitudinally into equal halves. In the experimental group a thin layer of NSCH was applied whilst the control group had no medicament. After 1, 3 and 6 months, nanoindentation was used to assess dentine hardness and the modulus of elasticity. Scanning Electron Microscopy (SEM) was used to visualize the depth of penetration of NSCH into the dentinal tubules. SEM images showed that there were no structural changes in the dentine slabs that had NSCH application after 1, 3 or even 6 months. However, penetration of NSCH into the dentine tubules was seen at both 3 and 6 months with a significant reduction in the hardness of dentine observed at 3 (p<0.02) and 6 months (p<0.01). The modulus of elasticity was significantly lower (p<0.01) at 6 months. It appears that there is a significant reduction in the hardness of dentine with increasing periods of calcium hydroxide application. Prolonged application of NSCH could have a detrimental effect on dentine, making the dentine more prone to fracture.

Changes in stiffness of demineralized dentin following application of collagen crosslinkers

It is thought that increasing the strength of the dentin matrix using crosslinking agents may improve both the strength and the durability of resin-dentin bonds. The purpose of this study was to evaluate the effect of two collagen crosslinking agents (glutaraldehyde, GD and grape seed extract, GSE) on the modulus of elasticity of demineralized dentin. Sound molar fragments were fully demineralized and divided into five groups according to the type and concentration of crosslinking agents: 2.5% GD; 5% GD, 25% GD; 0.65% GSE; 6.5% GSE. Specimens were immersed in their respective solution and tested at baseline, 10 min, 30 min, 1 h, 2 h, 4 h. The elastic modulus of dentin was significantly affected by the treatment (p < 0.01) and exposure time (p < 0.01). There was a statistically significant interaction between the two factors evaluated (treatment vs. time p < 0.01). Mean baselines values varied between 4.8 and 6.2 MPa in water; after 4 h of treatment the values increased between 34.9 and 242.5 MPa, that were treatment time and agent dependent. The use of these collagen crosslinkers to increase the stiffness of demineralized dentin, was both concentration and time dependent.

Determination of elastic modulus of demineralized resin‐infiltrated dentin by self‐etch adhesives

The purpose of this study was to determine ultrasonically the changes in elastic modulus of demineralized adhesive-infiltrated dentin. Dentin disks were obtained from bovine incisors and shaped into a rectangular form. The specimens were immersed in single-step self-etch adhesives, then stored in distilled water and run through thermal cycles between 5 and 60 degrees C. The longitudinal and shear wave sound velocities and the elastic modulus were determined using ultrasonic equipment composed of a pulser-receiver, transducers, and an oscilloscope. After 24 h of storage, the elastic modulus of mineralized dentin was 16.9 GPa and that of demineralized dentin was 2.1 GPa. The immersion of demineralized dentin in adhesives significantly increased the elastic modulus to 3.3-5.9 GPa. After 30,000 thermal cycles, the elastic modulus of dentin was 32.4 GPa, whereas that of demineralized adhesive infiltrated dentin was 3.1-4.1 GPa. Thermal stresses did not cause adhesive-infiltrated demineralized dentin to deteriorate, as measured by elastic modulus.

AFM-Based Nanomechanical Properties and Storage of Dentin and Enamel

ABSTRACTThis study evaluated the affects of 2 different solutions, e. g. deionized water and Hanks' Balanced Salt Solution (HBSS), on nanohardness and elastic modulus of dentin and enamel from human third molars at storage times of 0, 1, 7, 14 and 28 days using a modified AFM (Triboscope). The pH values of the solutions were monitored throughout the test periods. Storing the specimens in deionized water resulted in a large decrease of mechanical properties, e.g. the reduced elastic modulus of dentin decreased from 24.0 ±1.5 GPa to 21.0 ±1.6, 8.6 ±1.1 and 5.2 ±1.1 GPa for storage times of 1, 7 and 14 days, respectively. Mechanical properties of dentin and enamel dropped by more than 12% after one day and more than 50% after a week when stored in deionized water. The observed changes in mechanical response were attributed to a superficial demineralization process during storage. In contrast, storing teeth in HBSS did not significantly alter the mechanical properties of dentin or enamel over the time studied.