Micro-Computed Tomography Applications in Dentistry

Micro-computed tomography (MCT) encompasses two primary scanning options: ex-vivo and in-vivo imaging. Ex-vivo scanning involves the examination of extracted teeth or dental specimens, allowing for detailed analyses of the microarchitecture of mineralized tissue. By analyzing the microarchitecture of dental tissues, MCT can provide valuable information about bone density, porosity, and microstructural changes, contributing to a better understanding of disease progression and treatment outcomes. Moreover, MCT facilitates the quantification of dental parameters, such as bone volume, trabecular thickness, and connectivity density, which are crucial for evaluating the efficacy of dental interventions. This present study aims to comprehensively review and explore the applications of MCT in dentistry and highlight its potential in advancing research and clinical practice. The results depicted that the quantitative approach of MCT enhances the precision and reliability of dental research. Researchers and clinicians can make evidence-based decisions regarding treatment strategies and patient management, relying on quantifiable data provided by MCT. The applications of MCT in dentistry extend beyond research, with potential clinical implications in fields such as dental implantology and endodontics. MCT is expected to play an increasingly significant role in enhancing our understanding of dental pathologies, improving treatment outcomes, and ultimately, benefiting patient care in the field of dentistry.

Comparative study of chitosan/fibroin–hydroxyapatite and collagen membranes for guided bone regeneration in rat calvarial defects: micro-computed tomography analysis

This study aimed to utilize micro-computed tomography （micro-CT） analysis to compare new bone formation in rat calvarial defects using chitosan/fibroin-hydroxyapatite （CFB-HAP） or collagen （Bio-Gide） membranes. Fifty-four （54） rats were studied. A circular bony defect （8 mm diameter） was formed in the centre of the calvaria using a trephine bur. The CFB-HAP membrane was prepared by thermally induced phase separation. In the experimental group （n= 18）, the CFB-HAP membrane was used to cover the bony defect, and in the control group （n= 18）, a resorbable collagen membrane （Bio-Gide） was used. In the negative control group （n= 18）, no membrane was used. In each group, six animals were euthanized at 2, 4 and 8 weeks after surgery. The specimens were then analysed using micro-CT. There were significant differences in bone volume （BV） and bone mineral density （BMD） （P〈O.05） between the negative control group and the membrane groups. However, there were no significant differences between the CFB-HAP group and the collagen group. We concluded that the CFB-HAP membrane has significant potential as a guided bone regeneration （GBR） membrane.

Investigating microstructure of Longmaxi shale in Shizhu area,Sichuan Basin, by optical microscopy, scanning electron microscopy and micro-computed tomography

Microstructure of shale formation is the key to understanding its petrophysical and chemical properties.Optical microscopy, scanning electron microscopy and micro-computed tomography(μ-CT) have been combined for characterization of microstructure of Longmaxi(LMX)shale from Shizhu area, Sichan Basin. The results indicate that laminated LMX shale consists of mineral matrix-rich layers and organic matter(OM)-rich layers at micrometer scale in two and three dimensions. Mineral matrix layers,mainly consisting of interparticle pores and intraplatelet pores, are approximately parallel to the bedding plane.Pyrite-rich layer, mainly containing intercrystalline pores,shows a strong preferred orientation parallel to the bedding plane. OM-rich layer, mainly containing OM pores, seems to be discontinuous. In addition, intercrystalline pores are enriched in some layers, while OM pores are distributed irregularly in matrix layers. This vertical heterogeneity of pore microscopic structures in LMX shale is of great importance to understand its petrophysical and chemical properties.

Nondestructive Skeletal Imaging of Hyla suweonensis Using Micro-Computed Tomography

We successfully obtained 3D skeletal images of Hyla suweonensis, employing a nondestructive method by applying appropriate anesthesia and limiting the radiation dose. H. suweonensis is a tree frog endemic to Korea and is on the list of endangered species. Previous studies have employed caliper-based measurements and two-dimensional （2D） X-ray imaging for anatomical analyses of the skeletal system or bone types of H. suweonensis. In this work we reconstructed three-dimensional （3D） skeletal images of H. suweonensis, utilizing a nondestructive micro-computed tomography （micro-CT） with a short scan and low radiation dose （i.e. 4 min and 0.16 Gy）. Importantly, our approach can be applied to the imaging of 3D skeletal systems of other endangered frog species, allowing both versatile and high contrast images of anatomical structures without causing any significant damages to the living animal.

Contrast-enhanced micro-computed tomography using Exi Tron nano6000 for assessment of liver injury

AIM: To explore the potential of contrast-enhanced computed tomography(CECT) using Exi Tron nano6000 for assessment of liver lesions in mouse models.METHODS: Three mouse models of liver lesions were used: bile duct ligation(BDL),lipopolysaccharide(LPS)/D-galactosamine(D-Gal N),and alcohol.After injection with the contrast agent Exi Tron nano6000,the mice were scanned with micro-CT.Liver lesions were evaluated using CECT images,hematoxylin and eosin staining,and serum aminotransferase levels.Macrophage distribution in the injury models was shown by immunohistochemical staining of CD68.The in vitro studies measured the densities of RAW264.7 under different conditions by CECT.RESULTS: In the in vitro studies,CECT provided specific and strong contrast enhancement of liver in mice.CECT could present heterogeneous images anddensities of injured livers induced by BDL,LPS/D-Gal N,and alcohol.The liver histology and immunochemistry of CD68 demonstrated that both dilated biliary tracts and necrosis in the injured livers could lead to the heterogeneous distribution of macrophages.The in vitro study showed that the RAW264.7 cell masses had higher densities after LPS activation.CONCLUSION: Micro-CT with the contrast agent Exi Tron nano6000 is feasible for detecting various liver lesions by emphasizing the heterogeneous textures and densities of CECT images.

Microstructure Study of Normal Lunates with Micro-computed Tomography

In order to study the microstructure characteristics of normal lunate bones, eight fresh cadaver normal lunates were scanned with micro-computed tomography. High-resolution images of the micro-structure of normal lunates were obtained and we analyzed the nutrient foramina. Then nine regions of interest(ROI) were chosen in the central sagittal plane so that we could obtain the parameters of trabecular bones of ROIs. The distal lamellar-like compact structure had statistically significant differences when it was compared with the ROIs in the volar and dorsal ends of the distal cortex. The difference of diameter between the volar and dorsal foramina was significant(P<0.05). However, there was no significant difference regarding the number. The trabecular bones of the volar and dorsal distal ends had lower intensity than those of the distal central subchondral bone plate. The diameters of the nutrient foramina on the volar cortex were larger than those on the dorsal. This research provided more detailed information about microstructure of normal lunate and the nutrient foramina on cortex, and a reference for further study about diseased lunate.

Monitoring vascular changes induced by photodynamic therapy using contrast-enhanced micro-computed tomography

The aim of this study was to determine whether contrast-enhanced micro-computed tomography can be used for non-invasive imaging of the early-stage changes in the vasculature of tumours that have been treated with photodynamic therapy (PDT). The subjects used were C3H mice with an RIF-1 tumour implanted subcutaneously and allowed to grow for 3 weeks prior to treatment. The experimental groups were PDT-treated (150 J/cm2 and 50 J/cm2) and control (150 J/cm2 light-only and untreated). The laser light exposure was performed at 15 - 30 minutes after the administration of the photosensitizer (BPD-MA). The contrast-enhanced micro-computed tomography imaging procedure consisted of eight-second scans taking place before treatment and up to 24 hours after treatment. The 150 J/cm2 PDT group showed a significant increase in the ratio of blood volume to tumour volume at 2, 8 and 24 hours after treatment when compared to pre-treatment measurements (p 2 PDT group at 24 hours after treatment. This preliminary study indicates that micro-CT can detect compromised vasculature in tumours treated with high-fluence photodynamic therapy as early as 2 hours post treatment.

Micro-computed tomography assessment of human femoral trabecular bone for two disease groups(fragility fracture and coxarthrosis):Age and gender related effects on the microstructure

The aim of this study was to identify three-dimensional microstructural changes of trabecular bone with age and gender, using micro-computed tomography. Human trabecular bone from two disease groups, osteoporosis and osteoarthritis was analyzed. A prior analysis of the effects of some procedure variables on the micro-CT results was performed. Preliminary micro-CT scans were performed with three voxel resolutions and two acquisition conditions. On the reconstruction step, the image segmentation was performed with three different threshold values. Samples were collected from patients, with coxarthrosis (osteoarthritis) or fragility fracture (osteoporosis). The specimens of the coxarthrosis group include twenty females and fifteen males, while the fragility fracture group was composed by twenty three females and seven males. The mean age of the population was 69 ± 11 (females) and 67 ± 10 years (males), in the coxarthrosis group, while in the fragility fracture group was 81 ± 6 (females) and 78 ± 6 (males) years. The 30 μm voxel size provided lower percentage difference for the microarchitecture parameters. Acquisition conditions with 160 μA and 60 kV permit the evaluation of all the volume’s sample, with low average values of the coefficients of variation of the microstructural parameters. No statistically significant differences were found between the two diseases groups, neither between genders. However, with aging, there is a decrease of bone volume fraction, trabecular number and fractal dimension, and an increase of structural model index and trabecular separation, for both disease groups and genders. The parameters bone specific surface, trabecular thickness and degree of anisotropy have different behaviors with age, depending on the type of disease. While in coxarthrosis patients, trabecular thickness increases with age, in the fragility fracture group, there is a decrease of trabecular thickness with increasing age. Our findings indicate that disease, age and gender do not provide significant differences in trabecular microstructure. With aging, some parameters exhibit different trends which are possibly related to different mechanisms for different diseases.

Anti-catabolic effect of caffeic acid phenethyl ester, an active component of honeybee propolis on bone loss in ovariectomized mice： a micro-computed tomography study and histological analysis

Background Osteoporosis （OP） is a common bone disease,which adversely affects life quality.Effective treatments are necessary to combat both the loss and fracture of bone.Recent studies indicated that caffeic acid phenethyl ester （CAPE） is a natural chemical compound from honeybee propolis which is capable of attenuating osteoclastogenesis and bone resorption.Therefore,this study aimed to investigate the effect of CAPE on bone loss in OP mice using micro-computed tomography （CT） and histology.Methods Eighteen mice were prepared and evenly divided into three groups.The six mice in the sham＋PBS group did not undergo ovariectomy and were intraperitoneally injected with PBS during the curing period.Twelve mice were ovariectomized （OVX） to induce OP.Six of them in the OVX＋CAPE group were intraperitoneally injected with 0.5 mg/kg CAPE twice per week for 4 weeks after ovariectomy.The other six OVX mice in OVX＋PBS group were treated with PBS.All the mice were sacrificed 4 weeks after ovariectomy.The tibias were bilaterally excised for micro-CT scan and histological analysis.The Mann-Whitney U test was used to test the statistical differences among groups.Results Bone loss occurred in OVX mice.Compared with the sham＋PBS group,mice in the OVX＋PBS group exhibited a significant decrease in bone mineral density （BMD,P ＜0.05）,bone volume fraction （BV/TV,P ＜0.01）,trabecular thickness （Tb.Th,P ＜0.05）,and trabecular number （Tb.N,P ＜0.01）,as well as a non-insignificant increase in the number of osteoclasts （N.Oc/B.Pm）.With CAPE treatment,the microarchitecture of the tibial metaphyses was significantly improved with a reduction of osteoclast formation.Compared with the OVX＋PBS group,BV/TV in the OVX＋CAPE group was significantly increased by 33.9％ （P ＜0.05）.Conclusion CAPE therapy results in the protection of bone loss induced by OVX.

Structural analysis on cutting notch of tea stalk by X-ray micro-computed tomography

Quantitative analysis on cutting notch of tea stalk is one method to better understand shear resistance and mechanical properties of the stalk,which could improve cutting performance and efficiency for tea harvesting.Optimal design of the cutter might be achieved through structural analysis of cutting notch by X-ray micro-computed tomography(micro-CT).The third inter-node of the stalks were sampled and scanned by micro-CT after they were cut at different cutting depths(0.7,1.5,2.3 mm)and cutting edge angles of cutter(30,35,40).The structural change of the cutting notch and cutting force was observed.Grey-scale histogram analysis and bimodal segmentation method were used to extract the information about cutting notch from 2D slice images.A 3D model of the stalk was established with reconstruction and volume rendering.Besides,maximum crosssectional area ratio of cutting notch(MCSARCN)and volume ratio of cutting notch(VRCN)were calculated.The results show that MCSARCN and VRCN had a closely relationship with the cutting force,cutting depth and cutting edge angle according to 3D tomographic images and 2D slice images.Both MCSARCN and VRCN increased with cutting depth,despite of cutting edge angle.For cutting edge angle of 30,35and 40at different cutting depths,MCSARCN increased from 4.89%to 9.47%,from 8.51%to 22.83%and from 4.30%to 16.87%,respectively.Meanwhile,VRCN increased from 1.59%to 2.13%,from 2.98%to 5.76%and from 3.04%to 5.01%,respectively.When cutting depth was 1.5 mm,cutting force increased but VRCN present a decreased trend with cutting edge angle.X-ray micro-CT could be used to analyze the structure on cutting notch of tea stalks which is helpful in optimizing the structural parameters of the cutter.

Low-fat microwaved peanut snacks production:Effect of defatting treatment on structural characteristics,texture,color,and nutrition

This study develops low-fat microwaved peanut snacks(LMPS)using partially defatted peanuts(PDP)with different defatting ratios,catering to people’s pursuit of healthy,low-fat cuisine.The effects of defatting treatment on the structural characteristics,texture,color,and nutrient composition of LMPS were comprehensively explored.The structural characteristics of LMPS were characterized using X-ray micro-computed tomography(Micro-CT)and scanning electron microscope(SEM).The results demonstrated that the porosity,pore number,pore volume,brightness,brittleness,protein content,and total sugar content of LMPS all significantly increased(P<0.05)with the increase in the defatting ratio.At the micro level,porous structure,cell wall rupture,and loss of intracellular material could be observed in LMPS after defatting treatments.LMPS made from PDP with a defatting ratio of 64.44%had the highest internal pore structural parameters(porosity 59%,pore number 85.3×10^(5),pore volume 68.23 mm3),the brightest color(L^(*) 78.39±0.39),the best brittleness(3.64±0.21)mm^(–1)),and the best nutrition(high protein content,(34.02±0.38)%;high total sugar content,(17.45±0.59)%;low-fat content,(27.58±0.85)%).The study provides a theoretical basis for the quality improvement of LMPS.

In-situ Micro-CT analysis of deformation behavior in sandwich-structured meta-stable beta Ti−35Nb alloy

Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.

Phase behavior of gas condensate in porous media using real-time computed tomography scanning

The phase behavior of gas condensate in reservoir formations differs from that in pressure-volume-temperature(PVT)cells because it is influenced by porous media in the reservoir formations.Sandstone was used as a sample to investigate the influence of porous media on the phase behavior of the gas condensate.The pore structure was first analyzed using computed tomography(CT)scanning,digital core technology,and a pore network model.The sandstone core sample was then saturated with gas condensate for the pressure depletion experiment.After each pressure-depletion state was stable,realtime CT scanning was performed on the sample.The scanning results of the sample were reconstructed into three-dimensional grayscale images,and the gas condensate and condensate liquid were segmented based on gray value discrepancy to dynamically characterize the phase behavior of the gas condensate in porous media.Pore network models of the condensate liquid ganglia under different pressures were built to calculate the characteristic parameters,including the average radius,coordination number,and tortuosity,and to analyze the changing mechanism caused by the phase behavior change of the gas condensate.Four types of condensate liquid(clustered,branched,membranous,and droplet ganglia)were then classified by shape factor and Euler number to investigate their morphological changes dynamically and elaborately.The results show that the dew point pressure of the gas condensate in porous media is 12.7 MPa,which is 0.7 MPa higher than 12.0 MPa in PVT cells.The average radius,volume,and coordination number of the condensate liquid ganglia increased when the system pressure was between the dew point pressure(12.7 MPa)and the pressure for the maximum liquid dropout,Pmax(10.0 MPa),and decreased when it was below Pmax.The volume proportion of clustered ganglia was the highest,followed by branched,membranous,and droplet ganglia.This study provides crucial experimental evidence for the phase behavior changing process of gas condensate in porous media during the depletion production of gas condensate reservoirs.

Influence of inter-grain cementation stiffness on the effective elastic properties of porous Bentheim sandstone

Effective elastic properties of porous media are known to be significantly influenced by porosity.In this paper,we investigated the influence of another critical factor,the inter-grain cementation stiffness,on the effective elastic properties of a granular porous rock(Bentheim sandstone)using an advanced numerical workflow with realistic rock microstructure and a theoretical model.First,the disparity between the experimentally tested elastic properties of Bentheim sandstone and the effective elastic properties predicted by empirical equations was analysed.Then,a micro-computed tomography(CT)-scan based approach was implemented with digital imaging software AVIZO to construct the 3D(three-dimensional)realistic microstructure of Bentheim sandstone.The microstructural model was imported to a mechanics solver based on the 3D finite element model with inter-grain boundaries modelled by cohesive elements.Loading simulations were run to test the effective elastic properties for different shear and normal intergrain cementation stiffness.Finally,a relation between the macroscale Young’s modulus and inter-grain cementation stiffness was derived with a theoretical model which can also account for porosity explicitly.Both the numerical and theoretical results indicate the influence of the inter-grain cementation stiffness,on the effective elastic properties is significant for porous sandstone.The calibrated normal and shear stiffnesses at the inter-grain boundaries are 1.2×10^(5) and 4×10^(4) GPa/m,respectively.

Three-Point Bending Test and Crack Detection by Acoustic Emission on Different Spring Steel Wires with Different Crystallographic Textures

In the production of compression springs,high forming velocities and grades of deformation during winding and setting may induce cracks that can lead to failure causing risks of an accident and damage.The AE(acoustic emission)technology,a non-destructive monitoring method,can detect acoustic signals reflected from cracks.To establish this method in the production of technical springs,it was necessary,to find out whether the AE signal is influenced by material properties,phase fractions distribution from tempered martensite,retained austenite,and microstructure including crystallographic texture.In addition,it was investigated to what extent the detected AE signal can be useful to separate between an actual crack and other material responses.Within an in-situ three-point bending test with the AE technology,macro-and micro-crack-typical AE signals were detected for five different spring steel wires(SH,VDSiCr,and FDSiCr according to EN-10270-1 and EN-10270-2).The relative energy related to the initiation,propagation,and growth of cracks caused by mechanical stress was measured using a piezoelectric sensor.If a crack AE signal appeared for the first time,the bending tests were stopped immediately.The results show that the frequency spectrum combined with the intensity of the acoustic signals generated during crack growth depends on the material properties and the crystallographic texture.Furthermore,it could be shown that it is possible to differentiate between micro-crack-typical AE signals and other signals that result from different material responses.

EVALUATION OF SMALL ANIMAL IMAGING UNDER DIFFERENT SCAN CONDITIONS

To evaluae small animal imaging with individual different high voltage, filter thickness and tube current, an animal X-ray micro-computed tomography （micro-CT） system based on panel detector is developed and a rat is scanned by using the system with individual high voltage, tube current, filter thickness, and exposure time. A model is presented based on the Monte Carlo code PENELOPE for generating the X-ray spectra of X-ray tube used in the micro-CT system. A platform developed based on Matlab allows for calculating beam quality parameters, including the average energy of X-ray beam, the change of transmition rate and the input X-ray fluence. The factors affecting the signal difference to noise ratio （SDNR） of micro-CT are investigated and the relationship between SDNR and scan combinations is analyzed. A series of tools and methods are developed for small animal imaging and imaging performance evaluation in the field of small animal imaging.

Dental and periodontal phenotype in sclerostin knockout mice

Sclerostin is a Wnt signalling antagonist that controls bone metabolism. Sclerostin is expressed by osteocytes and cementocytes; however, its role in the formation of dental structures remains unclear. Here, we analysed the mandibles of sclerostin knockout mice to determine the influence of sclerostin on dental structures and dimensions using histomorphometry and micro-computed tomography （μCT） imaging, μCT and histomorphometric analyses were performed on the first lower molar and its surrounding structures in mice lacking a functional sclerostin gene and in wild-type controls, pCT on six animals in each group revealed that the dimension of the basal bone as well as the coronal and apical part of alveolar part increased in the sclerostin knockout mice. No significant differences were observed for the tooth and pulp chamber volume. Descriptive histomorphometric analyses of four wild-type and three sclerostin knockout mice demonstrated an increased width of the cementum and a concomitant moderate decrease in the periodontal space width. Taken together, these results suggest that the lack of sclerostin mainly alters the bone and cementum phenotypes rather than producing abnormalities in tooth structures such as dentin.

NEW APPROACH TO DETECT CARDIAC-PULMONARY MOTION FOR MICRO-CT SYSTEM

Non-invasive cardiac-pulmonary gating is proposed to improve the imaging resolution. It produces signals based on the cardiac-pulmonary motion of an animal in real-time. The system with the non-invasive gating consists of a digital signal processor （DSP）, an electrocardiography （ECG） detection circuit and a thermoeouple circuit. An enhanced R wave detection algorithm based on zero crossing counts is used to adjust the low sample frequency associated with the respiratory rate of an animal. The thermocouple recognizes the respiration phase by sensing the temperature changes of the nasal airflow of an animal. The proposed gating can accurately generate the gating signal for freely breathing mice （weight of around 0.03 kg）, and its respiratory signal is too weak to be detected. Apart from non-invasiveness, compared with other existing gating techniques, it occupies minimal space at lower cost. Actually, it can be used in micro-computed tomography （CT） and other systems needed to detect the cardiac-pulmonary motion. Several tests validate that the proposed cardiac-pulmonary gating can generate the gating signal as required. By using the gating technique, the image resolution is improved.

Optimization of taste-masking on ibuprofen microspheres with selected structure features

The microsphere was a primary particulate system for taste-masking with unique structural features defined by production process. In this article, ibuprofen lipid microspheres of octadecanol and glycerin monostearate were prepared to mask the undesirable taste of ibuprofen via three kinds of spray congealing processes, namely, air-cooling, water-cooling and citric acid solution-cooling. The stereoscopic and internal structures of ibuprofen microspheres were quantitatively analyzed by synchrotron radiation X-ray micro-computed tomography(SR-μCT) to establish the relationship between the preparation process and microsphere architectures. It was found that the microstructure and morphology of the microspheres were significantly influenced by preparation processes as the primary factors to determine the release profiles and taste-masking effects. The sphericity of ibuprofen microspheres congealed in citric acid solution was higher than that of other two and its morphology was more regular than that being congealed in air or distilled water, and the contact angles between congealing media and melted ibuprofen in octadecanol and glycerin monostearate well demonstrated the structure differences among microspheres of three processes which controlled the release characteristics of the microspheres. The structure parameters like porosity, sphericity, and radius ratio from quantitative analysis were correlated well with drug release behaviors. The results demonstrated that the exterior morphology and internal structure of microspheres had considerable influences on the drug release behaviors as well as taste-masking effects.

Three-dimensional analysis of the physiological foramen geometry of maxillary and mandibular molars by means of micro-CT

The aim of this study was to investigate the physiological foramen diameter, shape and distance between physiological and anatomical apex of maxillary and mandibular first and second molars. Accurate knowledge of the physiological foramina morphology; thus, inherent mechanical shaping technical hindrances, is decisive when taking the corresponding root canal final preparation decision. The morphological dimensions of a total of 1 727 physiological foramina were investigated by means of micro-computed tomography. Mean narrow and wide （to a high number, oval） diameters of the physiological foramen were 0.24, 0.22 and 0.33 mm and 0.33, 0.31 and 0.42 mm in mesiobuccal （MB）, distobuccal （DB） and palatal （P） roots in maxillary first molars; 0.24, 0.22 and 0.33 mm and 0.41, 0.33 and 0.44 in MB, DB, and P roots in maxillary second molars. Mandibular first molars showed mean narrow and wide diameters of 0.24 and 0.30 mm and of 0.39 and 0.46 mm in mesial （M） and distal （D） roots; second mandibular molars showed 0.25 and 0.31 mm and 0.47 mm in M and D roots. The mean distance between the physiological foramina and anatomical apex was 0.82, 0.81 and 1.02 mm and 0.54, 0.43 and 0.63 mm in MB, DB and P roots of the maxillary first and second molars, respectively. A mean distance of 0.95 mm （M） and 1.05 mm （D） in the first and 0.78 mm （M） and 0.81 mm （D） in the second mandibular molars was observed. Based on the results obtained, assumable recommendations for final preparation size of the physiological foramen were calculated. However, when taking into consideration, the resulting standard deviations of marginal errors must be cautiously considered when taking a final decision in clinical endodontic treatment.