Preservation of the negative image of tooth enamel with dental impression material enhances morphometric measurements of gingival overgrowth

Gingival overgrowth is a common health problem caused by genetic and environmental risk factors. Animal models for quantitative histological studies are needed to uncover genetic predisposition and dose-response data that might put individuals at increased risk for gingival disease. Gingival height, thickness, inflammation, and the degree of encroachment of gingiva over the tooth, are clinical measures of overgrowth; most of these parameters can be measured histologically, but in order to quantify gingival coverage of the tooth, the image of the crown must be present. Tooth and bone typically require decalcification for histology; thus, the tooth crown, a critical landmark, is lost. We describe a method for imaging the crown histologically, using impression materials applied to dissected mouse mandibles. Four dental alginates, three polyvinyl siloxanes, and one polyether and gelatin were used. The impression-material/mandibular tissue blocks were processed routinely. Polyvinyl siloxanes were incompatible with embedding resin; alginates, polyether and gelatin could be fixed, decalcified, embedded, and sectioned. Alginates and gelatin could be stained. Success in imaging the tooth crown varied with the preparation, but the alginates, polyether, and gelatin permitted a useful degree of measurement of exposed crown and enamel thickness, along with other morphometric parameters such as thickness of the dentin, lateral mandibular ramus, rete pegs, height of the gingiva, and volume density of vessels and inflammatory cells in the lamina propria. In conclusion, this new application for impression materials allows gingival coverage of tooth crown, as well as numerous other parameters to be measured for comparison with clinical data.     

X‐ray microdiffraction,TEM characterization and texture analysis of human dentin and enamel

Human tooth is a complex bioceramic composite, which consists of enamel, dentin and the interface, the dentin–enamel junction (DEJ). The crystal properties and ultrastructure of the inorganic phase through the thickness of healthy human molar teeth were investigated using X‐ray microdiffraction (μXRD), electron diffraction and transmission electron microscopy (TEM) techniques. The XRD data were analysed using the Le Bail profile fitting approach. The size and the texture of the crystallites forming enamel and dentin in the crown part of teeth were measured using both techniques and then compared. Results showed that the thickness of dentin crystallites was found to decrease towards the DEJ, whereas the thickness of the enamel crystallites increased from the DEJ towards the outer layers. It was demonstrated that enamel exhibited an increase of texture in 002 lattice planes from the DEJ towards the outer layers. Texture was also detected in 102 lattice planes. The texture effect in 002 planes at the scale of less than 1 μm was also demonstrated in dentin. The variation of lattice parameters as a function of the position within the thickness of dentin and enamel was also observed. The values of the nonuniform microstrain in the dentin and enamel crystallites were from 1.40 × 10^?6% to 4.44 × 10^?5%. The good correlation between XRD and TEM indicated that μXRD is a useful technique to study crystallography and microstructure of heterogeneous enamel and dentin. The observed gradient characteristics of texture and crystallite size in enamel and dentin maybe an evolutionary outcome to resist wear and fracture, thereby contributing to the excellent mechanical properties of teeth.     

Resin-tooth interfacial morphology and sealing ability of one-step self-etch adhesives: microleakage and SEM study

OBJECTIVES: To compare microleakage of three self‐etch adhesives and to analyze enamel surface morphology and interfacial morphology of resin–enamel and resin–dentin interface under scanning electron microscope (SEM). EXPERIMENTAL DESIGN: Study was conducted in 65 extracted human premolars. Class V cavities were prepared in 45 teeth and assigned to three groups (n = 15) according to three self‐etch adhesives (OptiBond All‐in‐One, iBond, and Adper Prompt L‐Pop). After restoration, 10 samples from each group were used to assess microleakage at enamel and dentin margin. Five samples from each group were used for analysis of interfacial morphology at resin–enamel and resin–dentin interface under SEM. Remaining 20 teeth were used to prepare flat enamel buccal surfaces to analyze the difference in surface morphology after treatment with three adhesives (n = 5 each) and 36% phosphoric acid treatment (n = 5). PRINCIPAL OBSERVATIONS: At enamel margin, Prompt L‐Pop depicted least leakage of all the three adhesives and also showed best interfacial adaptation under SEM. At dentin margin, OptiBond All‐in‐One showed significant less leakage than iBond and Prompt L‐Pop. On flat enamel surface, phosphoric acid produced the most retentive etching pattern when compared with the three adhesives. CONCLUSION: Prompt L‐Pop showed the best bonding effectiveness in enamel, whereas OptiBond All‐in‐One performed significantly better in dentin. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

The use of Er:YAG laser for cavity preparation: an SEM evaluation

OBJECTIVE: The purpose of this study was to evaluate morphological changes in cavities prepared by the Er:YAG laser (2.94 mum) at different parameters of irradiation and by a diamond bur. EXPERIMENTAL DESIGN: Cavities were prepared on 27 human molars (n = 3): G1, 15 Hz/160 mJ enamel/6 Hz/200 mJ dentin; G2, 15 Hz/180 mJ enamel/6 Hz/200 mJ dentin; G3, 15 Hz/160 mJ enamel/6 Hz/250 mJ dentin; G4, 15 Hz/180 mJ enamel/6 Hz/250 mJ dentin; G5, 15 Hz/180 mJ enamel/10 Hz/180 mJ dentin; G6, 15 Hz/160 mJ enamel/10 Hz/180 mJ dentin; G7, 15 Hz/160 mJ enamel/10 Hz/160 mJ dentin; G8, 15 Hz/180 mJ enamel/10 Hz/160 mJ dentin; G9, diamond bur. For SEM analysis, samples were fixed (2.5% glutaraldheyde, 12 h, 4 degrees C), dehydrated (25-100% ethanol), dried, and sputter-coated with gold. RESULTS: Despite the changes on energy and repetition-rate settings, all laser-treated samples showed no evidence of thermal damage or signs of burning and melting. Er:YAG laser ablated dental hard tissues showed exposed enamel prisms, dentin surface without smear layer, and opened dentinal tubules. CONCLUSION: Different Er:YAG laser parameters were effective for ablation of hard tissues, creating an irregular and microretentive morphological pattern without hard tissue damage.     

Effect of laser preparation on adhesion of a self‐adhesive flowable composite resin to primary teeth

The aim of the study was to evaluate the adhesion of a self‐adhering flowable composite resin to primary tooth enamel and dentin after silicon carbide paper (SiC) and laser pretreatment. Adhesive properties were evaluated as shear bond strength (SBS) and scanning electron microscopic (SEM) characteristics. A total 120 primary canine teeth were randomly divided into two groups to study enamel and dentin. Each group was divided into 6 subgroups (n = 10) according to type of surface preparation (SiC or Er:YAG laser) of enamel or dentin. Three methods were used to build cylinders of restoration on tooth surface: OptiBond All‐In‐One + Premise Flowable composite, OptiBond All‐In‐One + Vertise Flow and Vertise flow. After restoration, samples were tested for SBS and failure mode. Twenty eight samples were examined by SEM. The results of the study showed SBS of Vertise Flow was lower than others in enamel and dentin samples pretreated with SiC and in dentin samples pretreated with laser (P < 0.001). Compared to SiC pretreatment, laser pretreatment led to a significantly higher SBS with Vertise Flow on enamel (P < 0.001). Vertise Flow associated with the adhesive led to a higher SBS in enamel and dentin compared to Vertise Flow alone. Adhesive and mixed failure modes were observed more frequently in Vertise Flow groups. SEM images showed that Vertise Flow led to more irregularities on enamel and more open dentinal tubules after laser ablation compared SiC pretreatment. Microsc. Res. Tech. 79:334–341, 2016. © 2016 Wiley Periodicals, Inc.     

Chemical and morphological evaluation of enamel and dentin near cavities restored with conventional and zirconia modified glass ionomer subjected to erosion‐abrasion

Microenergy dispersive X‐ray fluorescence (μ‐EDXRF) spectroscopy and scanning electron microscopy (SEM) were used to test the hypothesis that zirconia modified glass ionomer cement (GIC) could improve resistance to erosion‐abrasion to a greater extent than conventional cement. Bovine enamel (n = 40) and dentin (n = 40) samples were prepared with cavities, filled with one of the two restorative materials (GIC: glass‐ionomer cement or ZrGIC: zirconia‐modified GIC). Furthermore, the samples were treated with abrasion‐saliva (AS) or abrasion‐erosion cycles (AE). Erosive cycles (immersion in orange juice, three times/day for a duration of 1 min over a 5 day period) and/or abrasive challenges (electric toothbrush, three times/day for a duration of 1 min over a 5 day period) were performed. Positive mineral variation (MV%) on the enamel after erosion‐abrasion was observed for both materials (p < 0.05), whereas a negative MV% on the dentin was observed for both materials and treatments (p < 0.05). The SEM images showed clear enamel loss after erosion‐abrasion treatment and material degradation was greater in GIC_AE compared to those of the other groups. Toothbrush abrasion showed a synergistic effect with erosion on substance loss of bovine enamel, dentin, GIC, and ZrGIC restorations. Zirconia addition to the GIC powder improved the resistance to abrasive‐erosive processes. The ZrGIC materials may find application as a restorative material due to improved resistance as well as in temporary restorations and fissure sealants.     

Comparison of methods for quantifying dental wear caused by erosion and abrasion

Various methods have been applied to evaluate the effect of erosion and abrasion. So, the aim of this study was to check the applicability of stylus profilometry (SP), surface hardness (SH) and focus‐variation 3D microscopy (FVM) to the analysis of human enamel and dentin subjected to erosion/abrasion. The samples were randomly allocated into four groups (n = 10): G1‐enamel/erosion, G2‐enamel/erosion plus abrasion, G3‐dentin/erosion, and G4‐dentin/erosion plus abrasion. The specimens were selected by their surface hardness, and they were subjected to cycles of demineralization (Coca‐Cola®‐60 s) and remineralization (artificial saliva‐60 min). For groups G2 and G4, the remineralization procedures were followed by toothbrushing (150 strokes). The above cycle was repeated 3×/day during 5 days. The samples were assessed using SH, SP, and FVM. For each substrate, the groups were compared using an unpaired t‐test, and Pearson correlation coefficients were calculated (α = 5%). For enamel, both profilometry technique showed greater surface loss when the erosion and abrasion processes were combined (P <0.05). The correlation analysis did not reveal any relationships among SH, SP, and FVM to G2 and G4. There were significant correlation coefficients (–0.70 and –0.67) for the comparisons between the FVM and SH methods in enamel and dentin, respectively, in G1 and G3. Choosing the ideal technique for the analysis of erosion depends on the type of dental substrate. SP was not sufficiently sensitive to measure the effects on dentin of erosion or erosion/abrasion. However, SP, FVM and SH were adequate for the detection of tissue loss and demineralization in enamel. Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.     

旋流泵内液固两相流场的CFD-PBM耦合计算

为获得旋流泵内更为符合物理真实的液固两相流动特征,在传统欧拉(Euler)双流体模型基础上加载群体平衡模型(PBM),以考虑实际存在的颗粒聚并、破碎等动力学行为,与CFD耦合计算了不同流量、颗粒粒径及浓度下的液固两相流场,分析了颗粒存在对泵外特性的影响规律。计算结果表明:从进口到出口,叶片背面附近颗粒粒径明显增大;在叶轮出口位置,同一半径上,从叶片工作面到背面附近存在粒径梯度;在外缘部,沿轴向形成粒径梯度。与Euler模型计算结果对比发现:加载PBM模型后,颗粒总体浓度分布特征存在差异;同一轴截面上,颗粒浓度在中心部的分布基本相同,而在中间和外缘部位置出现差异。PBM模型计算得到的泵扬程、效率曲线更接近于实验值,证明基于CFD-PBM耦合计算的预测精度更符合实际。     

High resolution SE-I SEM study of enamel crystal morphology

Until recently high resolution TEM was the only imaging mode capable of probing the atomic lattice structure of crystals composing tooth enamel. Studies designed to determine the polyhedral shape of normal enamel crystals and initiation of carious lesions in enamel crystals were hampered and limited by interpretation of two-dimensional TEM images from thin section and freeze fracture replica specimens lacking depth of field. The newly developed SE-I signal mode for SEM (SE-I/SE-II ratio) can produce images of enamel crystals approaching beam diameter dimensions (0.7–2.0 nm), rivaling the resolution of the TEM technique and generating topographic contrasts for three dimensional imaging at very high magnification (≈?1,000,000 X). Ultrathin chromium (Cr) films generate enriched high resolution SE-I contrasts of enamel crystal surfaces and when imaged using an immersion lens field emission SEM operated at high voltage (20–30 KeV) produce unsurpassed topographic contrasts. Since the grain size of Cr is below the resolution of any SEM and is ultrathin (≈?1 nm), then SE-I images can provide a more accurate representation of enamel crystal structure than TEM methodologies. Our SE-I SEM observations of normal human enamel crystals reveal fractured spicules which contain angled flat surfaces delineated by a prominent 2 nm wide SE-I edge brightness contrast. Although microscopic observations often show crystals which are hexagonal in cross-section, in both SEM and TEM many other growth habits, including rectangular or irregular crystals (30–40 nm in width) which contain “notches,” are also observed. More detailed morphological studies are therefore required to determine the most likely habit planes and their relevance to the function of the enamel crystals. The granular appearing fine structural contrast imposed onto <100> lattice planes of sectioned enamel in TEM micrographs is also resolved with topographic contrasts in SE-I micrographs. These granules probably represent one or both of the enamel protein classes.     

Marginal adaptation of composite resins under two adhesive techniques

In the present research, different adhesive techniques were used to set up fillings with composite resins. After the application of etch and rinse or self etch adhesive technique, marginal adaptation of composite fillings was estimated by the length of margins without gaps, and by the microretention of resin in enamel and dentin. The study material consisted of 40 extracted teeth. Twenty Class V cavities were treated with 35% phosphorous acid and restored after rinsing by Adper Single Bond 2 and Filtek Ultimate‐ASB/FU 3M ESPE composite system. The remaining 20 cavities were restored by Adper Easy One‐AEO/FU 3M ESPE composite system. Marginal adaptation of composite fillings was examined using a scanning electron microscope (SEM). The etch and rinse adhesive technique showed a significantly higher percentage of margin length without gaps (in enamel: 92.5%, in dentin: 57.3%), compared with the self‐etch technique with lower percentage of margin length without gaps, in enamel 70.4% (p < .001), and in dentin‐22.6% (p < .05). In the first technique, microretention was composed of adhesive and hybrid layers as well as resin tugs in interprismatic spaces of enamel, while the dentin microretention was composed of adhesive and hybrid layers with resin tugs in dentin canals. In the second technique, resin tugs were rarely seen and a microgap was dominant along the border of restoration margins. The SEM analysis showed a better marginal adaptation of composite resin to enamel and dentin with better microretention when the etch and rinse adhesive procedure was applied.     

Vacancy island creation and coalescence using automated scanning tunneling microscopy

We demonstrate that scanning tunneling microscope tip-surface crash events can be utilized as an efficient means for the creation of predefined island configurations for diffusion studies. Using this method, islands of varying size can be created and placed in close proximity, increasing the probability of initiating and observing coalescence events. Data obtained from crash initiated events on a Ag(111) surface are presented. Relaxation time exponents extracted from these data confirm that our method gives results consistent with previous, sputter-obtained island coalescence studies. We also describe an instrument-control routine developed for these measurements that utilizes commercial imaging and off-the-shelf automation software to automate the tracking of islands or other features by the microscope.     

螺旋面截形尖点矢量离散法及其在双圆弧滚刀过渡曲面最小化中的应用

在具有尖点廓形的螺旋曲面成形加工中,计算出的刀具截形常常产生曲线自交叉现象,导致刀具加工出的螺旋曲面在尖点处生成较大的过渡曲面.为此,提出尖点矢量离散法,将点及其法向矢量定义为一个点矢量,对两相交曲线在尖点处形成的首尾两个点矢量进行离散,使尖点处更多的几何信息带入到廓形计算中,提高了计算精度.给出过渡曲面最小化算法,用...     

Cutting Fluid Aerosol from Splash in Turning: Analysis for Environmentally Conscious Machining

The generation of airborne particulates from cutting fluids in machining operations poses a potential threat to machine operators. The primary mechanisms through which cutting fluid atomises to form liquid aerosol are splashing upon impingement on a solid workpiece, spin-off away from a rotating workpiece or tool, and evaporation due to high cutting temperature. This paper presents a quantitative model to describe the concentration and size distribution of aerosol resulting from the splash atomisation of cutting fluids in a lathe turning operation. In this analysis, the main parameters that govern the aerosol formation are the workpiece diameter, nozzle height, cutting fluid properties, and cutting fluid flow rate. The model first examines the fraction of splashed mass in relation to the total flow rate of cutting fluid based on the calibration of the splash parameter. The model further determines the statistical variation of the liquid droplet size due to unaccounted disturbances. The aerosol concentration is then expressed in terms of the product of the splash parameter and the fraction of total droplet volume of a specified size. The validity of the model is experimentally established based on light-scattering aerosol measurement carried out on a horizontal lathe with various jet heights, part diameters, and fluid flow rates. The results of this study can be used to estimate the amount of aerosol from a machining process, and to provide a quantitative basis for process optimisation, fluid planning, and machine design in achieving given environmental standards.     

Stress and strain distribution in demineralized enamel: A micro‐CT based finite element study

Physiological oral mechanical forces may play a role on the progression of enamel carious lesions to cavitation. Thus, the aim of this study was to describe, by 3D finite element analysis, stress, and strain patterns in sound and carious enamel after a simulated occlusal load. Micro‐CT based models were created and meshed with tetrahedral elements (based on an extracted third molar), namely: a sound (ST) and a carious tooth (CT). For the CT, enamel material properties were assigned according to the micro‐CT gray values. Below the threshold corresponding to the enamel lesion (2.5 g/cm³) lower and isotropic elastic modulus was assigned (E = 18 GPa against E₁ = 80 GPa, E₂ = E₃ = 20 GPa for sound enamel). Both models were imported into a FE solver where boundary conditions were assigned and a pressure load (500 MPa) was applied at the occlusal surface. A linear static analysis was performed, considering anisotropy in sound enamel. ST showed a more efficient transfer of maximum principal stress from enamel to the dentin layer, while for the CT, enamel layer was subjected to higher and concentrated loads. Maximum principal strain distributions were seen at the carious enamel surface, especially at the central fossa, correlating to the enamel cavity seen at the original micro‐CT model. It is possible to conclude that demineralized enamel compromises appropriate stress transfer from enamel to dentin, contributing to the odds of fracture and cavitation. Enamel fracture over a dentin lesion may happen as one of the normal pathways to caries progression and may act as a confounding factor during clinical diagnostic decisions. Microsc. Res. Tech. 78:865–872, 2015. © 2015 Wiley Periodicals, Inc.     

Three‐dimensional cellular distribution in polymeric scaffolds for bone regeneration: a microCT analysis compared to SEM,CLSM and DNA content

In orthopaedic surgery the tissues damaged by injury or disease could be replaced using constructs based on biocompatible materials, cells and growth factors. Scaffold design, porosity and early colonization are key components for the implant success. From biological point of view, attention may be also given to the number, type and size of seeded cells, as well as the seeding technique and cell morphological and volumetric alterations. This paper describes the use of the microCT approach (to date used principally for mineralized matrix quantification) to observe construct colonization in terms of cell localization, and make a direct comparison of the microtomographic sections with scanning electron microscopy images and confocal laser scanning microscope analysis. Briefly, polycaprolactone scaffolds were seeded at different cell densities with MG63 osteoblastic‐like cells. Two different endpoints, 1 and 2 weeks, were selected for the three‐dimensional colonization and proliferation analysis of the cells. By observing all images obtained, in addition to a more extensive distribution of cells on scaffolds surfaces than in the deeper layers, cell volume increased at 2 weeks compared to 1 week after seeding. Combining the cell number quantification by deoxyribonucleic acid analysis and the single cell volume changes by confocal laser scanning microscope, we validated the microCT segmentation method by finding no statistical differences in the evaluation of the cell volume fraction of the scaffold. Furthermore, the morphological results of this study suggest that an effective scaffold colonization requires a precise balance between different factors, such as number, type and size of seeded cells in addition to scaffold porosity.     

Analysis of transmittance and degree of conversion of composite resins

The objective of this study was to evaluate and correlate light transmittance (T), initial degree of conversion (IDC), and degree of conversion after 24 hr (DC24) for 22 composite resins (CR) for enamel and dentin use. The transmittance (n = 10) was measured with a spectrometer at a wavelength of 468.14 nm. The degree of conversion (DC; n = 5) was measured with Fourier Transform Near‐Infrared Spectroscopy before polymerization, immediately after photoactivation, and 24 hr after photoactivation. Both sets of values are provided as percentages. ANOVA and Games‐Howell (α = 5%) tests showed that Filtek Supreme Ultra gave the highest T values of all enamel CRs, while Esthet‐X HD presented the lowest. Meanwhile, Venus diamond gave the highest values of all dentin CRs, while Esthet‐X HD gave the lowest. For IDC and DC24, ANOVA showed differences between individual CRs and the two CR types (p < .0001). Despite the limitations of this study, it can be concluded that there was no correlation between T and either IDC or DC24 (p > .05); however, IDC and DC24 were strongly correlated (p < .05) by Pearson's correlation. That being said, as a higher DC reflects better mechanical properties, certain conclusions can be drawn about overall performance. The best IDC values were observed for the Opallis enamel resin and the Opallis and Premise dentin resins. Meanwhile, the best DC24 values were observed for the Opallis, Charisma, and Premise enamel resins and the Opallis and Premise dentin resins. Degree of conversion and light transmittance showed differences between composite resin types (enamel and dentin) and brands. It is important to know at the moment of composite choice taking into account mechanical and optical properties.     

Wear characteristics of porcelain denture teeth

Surface wear and frictional behavior of porcelain denture teeth were examined with a single-pass sliding technique. The influence of environment, type of surface (enamel or dentin) and repeated passes on the wear characteristics of the teeth were investigated. The enamel surface of the teeth was more resistant to penetration and to surface damage than the dentin surface was. Damage was more severe for double-pass than for single-pass sliding. The wear characteristics were affected similarly by the liquid environments of water and of human saliva. Quantitative differences in the wear parameters investigated were found between the two brands of porcelain denture teeth.     

Fine structure of tooth enamel in the yellowing human teeth: SEM and HRTEM studies

Objective : The aim of this study was to clarify an influence of the fine structure of human tooth enamel to the yellowing teeth. Materials and methods : Sound maxillary first premolars of 15–50‐year‐old females that were extracted for the orthodontic treatment were used as the test samples. The tooth enamel sections of these teeth that prepared by ion polishing were observed by scanning electron microscopy (SEM). Furthermore, the fine structure of substance filling the inter‐rod spaces was analyzed by high resolution transmission electron microscopy (HRTEM). Results : In white tooth, the inter‐rod spaces were observed at the width of about 0.1 μm, while in yellow tooth, the inter‐rod spaces were not clearly observed by SEM. HRTEM observations revealed for the first time that the inter‐rod spaces were filled with fine particles of poorly crystallized hydroxyapatite in the yellow tooth. In yellow tooth, it was considered that the color of the inner dentin was recognized due to the decrease of light scattering by filling the tooth enamel inter‐rod spaces. The generation of particles in the tooth enamel inter‐rod spaces was considered to be caused by the long‐time progression of calcification. Conclusions : These results suggested that the change in fine structure, filling in inter‐rod spaces of tooth enamel, was related to progression of calcification in the inter‐rod spaces with advancing age and one of the factors of yellowness of human tooth. Microsc. Res. Tech. 79:14–22, 2016. © 2015 Wiley Periodicals, Inc.     

基于五坐标数控圆柱形刀具线接触加工自由曲面的几何学原理

从微分几何学的角度,探讨了在五坐标数控机床上采用圆柱形刀具线接触加工自由曲面的几何学原理,分析了刀具面与被加工曲面二阶密切的条件。通过对二次型半正定的判别,求得了刀具轴线的位置,给出了点邻域内三阶离差的计算公式,证明了圆柱形刀具与被加工曲面的密切条件等价于刀具轴线与被加工曲面的等距面的密切条件,通过实例验证了所提方法的正确性。     

Fretting fatigue crack initiation behavior using process volume approach and finite element analysis

This study investigates crack initiation behavior by incorporating fretting fatigue process volume. Three critical plane based fretting fatigue crack initiation parameters are characterized by computing their averaged values over the process volume and then comparing with their counterparts obtained from the localized approach. Two approaches are used: first one involves the computation of parameter at several points over a rectangular region and then its average, and second approach computes the average state of stress/strain over a radial region from which the averaged parameter is calculated. Both approaches require pre-determination of a critical location at or around which the process volume needs to be placed. Effects of size and location of process volume on the averaged value of parameters are studied in detail. Two radii of cylindrical pad are analyzed to investigate the effect of severity of stress gradient on process volume approach. Effects of finite element mesh refinement are also investigated. Averaged value of parameter decreases with the increase of process volume size. This decrease is higher when the process volume is located in the region that is away from the contact zone. Further, a parameter based on normal stress on the critical plane shows more dependence on the size of process volume than that based on shear stress or on a combination of both shear and normal stresses. Orientation of crack initiation changes within a range that is well within the scatter band of experimental observations as the process volume size increases. Averaged value of parameter for a pad with higher stress gradient has a larger reduction with the increase of process volume size than that with a lower stress gradient. Process volume size has less effect on the averaged value of parameter with coarser finite element mesh. Finally, the localized approach provides a conservative value of fretting fatigue crack initiation parameter compared to its counterpart based on the process volume.