Fractal dimension and lacunarity analysis of dental radiographs

Comparison of quantitative radiomorphometric predictors of healthy and MRONJ-affected bone using panoramic radiography and cone-beam CT

OBJECTIVES

To determine the most distinctive quantitative radiomorphometric parameter(s) for the detection of MRONJ-affected bone changes in panoramic radiography (PR) and cone-beam CT (CBCT).

METHODS

PR and sagittal CBCT slices of 24 MRONJ patients and 22 healthy controls were used for the measurements of mandibular cortical thickness (MCT), fractal dimension (FD), lacunarity, mean gray value (MGV), bone area fraction (BA/TA), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number (Tb.N). MCT was measured in the mental foramen region. While FD and lacunarity were measured on mandibular trabecular and cortical regions-of-interest (ROIs), the remaining parameters were measured on trabecular ROIs. The independent samples t-test was used to compare the measurements between the MRONJ and control groups for both imaging modalities (P = .05).

RESULTS

MCT was the only parameter that differentiated MRONJ-affected bone in both PR and CBCT (P < .05). None of the remaining parameters revealed any difference for MRONJ-affected bone in CBCT (P > .05). FD, lacunarity, MGV, BA/TA, and Tb.Sp could distinguish MRONJ-affected trabecular bone in PR (P < .05). The correspondent ROI for both imaging methods that was reliable for detecting MRONJ-affected bone was the trabecular bone distal to the mental foramen above the inferior alveolar canal (ROI-3).

CONCLUSIONS

MCT is a reliable parameter for the discrimination of MRONJ-affected bone in both PR and CBCT images. PR may be used to detect MRONJ-affected trabecular bone using FD, lacunarity, MGV, BA/TA, and Tb.Sp measurements as well.

Evaluation of mandibular trabecular bone structure in growing children with Class I, II, and III malocclusions using fractal analysis: A retrospective study

OBJECTIVE

The present study aimed to evaluate the mandibular bone structure of patients with different malocclusions by using fractal dimension (FD) analysis on dental panoramic radiographic images.

MATERIAL AND METHODS

Pre-treatment panoramic radiographic images of 103 patients were included in the study and divided into 3 groups as Class I (group 1: 0

RESULTS

FD values were lower in Class I sagittal skeletal pattern than Class II and III groups in anterior ROI FD, premolar ROI FD, angulus ROI FD, and mean FD values. There were differences between Class I and Class III skeletal patterns (P=0.023 for anterior ROI FD, P=0.016 for premolar ROI FD, P=0.034 for angulus ROI FD, and P=0.014 for mean FD). Class I and II malocclusions differed in anterior ROI FD (P=0.029) and also Classes II and III showed differences in angulus ROI FD (P=0.029).

CONCLUSION

Sagittal skeletal patterns may result in differences in the structure of the mandibular trabecular bone.

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Key Words

• Fractal dimension analysis
• Orthodontics
• Panoramic radiography
• Sagittal skeletal malocclusions

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MESH Headings

• Humans
• Child
• Mandible/diagnostic imaging
• Male
• Female
• Fractals
• Retrospective Studies
• Radiography, Panoramic
• Malocclusion, Angle Class III/diagnostic imaging
• Malocclusion, Angle Class II/diagnostic imaging
• Cancellous Bone/diagnostic imaging
• Malocclusion, Angle Class I/diagnostic imaging
• Malocclusion/diagnostic imaging
• Adolescent
• Cephalometry/methods

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Affiliation(s)

Hümeyra Tercanlı Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Akdeniz University, 07058 Antalya, Turkey
Esra Bolat Gümüş Department of Orthodontics, Faculty of Dentistry, Akdeniz University, 07058 Antalya, Turkey.

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Evaluation of mandibular trabecular bone by fractal analysis in pediatric patients with hypodontia of the mandibular second premolar tooth

BACKGROUND

It is still unclear whether the trabecular structure of the jaw is different in individuals with hypodontia than in those without hypodontia; this is important for clinicians. The aim was to determine whether the mandibular trabecular bone structure of children and adolescents with hypodontia differs from the control group by using the fractal analysis (FA) method in this study.

METHODS

A total of 138 panoramic radiographs of 69 cases and 69 control subjects (mean age 13.2 ± 10.1) were evaluated. The age and gender of subjects in the case and control groups were matched. Three regions of interest (ROIs) were selected from the panoramic radiographs. ROI1 refers to the center of the ramus rising above the mandibular foramen. ROI2 refers to the area between the apical level of the mandibular molar and the upper border of the mandibular canal. ROI3, the missing tooth region, refers to the apical third of the mesial side of the erupting or fully erupted permanent mandibular first molar. Mann-Whitney U and Wilcoxon tests were used. p < 0.05 was accepted for the significance value.

RESULTS

The mean fractal dimension (FD) values of ROI1, ROI2, and ROI3 were 1,25, 1,20, and 1,13, respectively. The means FD values obtained from the ramus region were higher than the other regions (p < 0.05). The FD values did not differ significantly according to gender and age (p > 0.05). The FD values of the case group were lower than the control group for ROI3 (p < 0.05).

CONCLUSION

The results of this study showed that the mandibular trabecular bone quality of pediatric patients with one missing tooth was different from the healthy group. The difference in the mean FD values from the ROIs indicates that the ramus has a denser structure than the mandibular corpus. Clinicians should factor this into their dental treatment planning process.

Mechanical Properties and Failure Mode of Proximal Screw Fixation Technique Using Locking Compression Plate for Proximal Interphalangeal Arthrodesis in Horses: An Ex Vivo Study

OBJECTIVE

 The aim of this study was to measure the mechanical properties and failure mode of an ex vivo model of proximal interphalangeal arthrodesis in horses with different methods of proximal screw fixation using a locking compression plate.

STUDY DESIGN

 Pastern joint arthrodesis with a 3-hole 4.5-mm narrow locking compression plate was performed on 20 forelimbs of equine cadavers, randomized into four groups based on the fixation method and type of proximal screw used: unicortical cortex, bicortical cortex, unicortical locking, bicortical locking. Single-cycle axial compression testing was conducted until failure. The frequency of implant plastic deformation was recorded. Bone failure analysis was performed through computed tomography examinations and fractal analysis.

RESULTS

 There were no differences in the analysed mechanical variables and fractal dimension among the groups. Transarticular screws showed a higher frequency of deformation (75%) regardless of the group. Both unicortical locking and bicortical locking groups deformed the plate more frequently.

CONCLUSION

 The type of screw used in the proximal hole of the locking compression plate and its method of anchoring in the proximal phalanx do not affect the mechanical properties of pastern arthrodesis in equine cadavers subjected to single-cycle axial compression tests until failure.

Evaluation of Jaw Bone Change in Children and Adolescents with Rheumatic Heart Disease by Fractal Analysis

BACKGROUND

Recognizing the oral needs of people living with rheumatic heart disease (RHD), particularly in relation to their jaws, is of paramount importance.

AIMS

This study aimed to evaluate potential jaw bone changes in children and adolescents diagnosed with RHD and compare them with a group of healthy children and adolescents.

METHODS AND MATERIAL

The dental panoramic radiographs (DPRs) of 32 children and adolescents diagnosed with RHD comprised the case group. In contrast, the control group consisted of DPRs from 32 children and adolescents without any known diseases. Two regions of interest (ROI1 and ROI2) of trabecular bone and a separate region of interest (ROI3) of cortical bone were selected for fractal analysis. The mandibular cortical index (MCI) was evaluated.

RESULTS

The ROI1 fractal dimension (FD) value of the individuals in the case group was statistically higher in the right jaw than in the left jaw (P < 0.01). Significant differences were determined between the case and control groups regarding the left ROI1, and the left and the right ROI2 (P < 0.05). No significant difference was found between the patient and control groups regarding the MCI value (P > 0.05).

CONCLUSIONS

The results of this study showed that bone metabolism was affected unilaterally in the condyle region and bilaterally in the gonial region of patients with RHD. It also revealed that the cortical layer was not affected.

A comprehensive study from the micro- to the nanometric scale: Evaluation of chilling injury in tomato fruit (Solanum lycopersicum)

Tomato fruit is susceptible to chilling injury (CI) during its postharvest handling at low temperature. The symptoms caused by this physiological disorder have been commonly evaluated by visual inspection at a macro-observation scale on fruit surface; however, the structure at deeper scales is also affected by CI. This work aimed to propose a descriptive model of the CI development in tomato tissue under the micro-scale, micro-nano-scale and nano-scale approaches using fractal analysis. For that, quality and fractal parameters were determined. In this sense, light microscopy, Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) were applied to analyse micro-, micro-nano- and nano-scales, respectively. Results showed that the morphology of tomato tissue at the micro-scale level was properly described by the multifractal behaviour. Also, generalised fractal dimension (Dq=0) and texture fractal dimension (FD) of CI-damaged pericarp and cuticle were higher (1.659, 1.601 and 1.746, respectively) in comparison to non-chilled samples (1.606, 1.578 and 1.644, respectively); however, FD was unsuitable to detect morphological changes at the nano-scale. On the other hand, lacunarity represented an appropriate fractal parameter to detect CI symptoms at the nano-scale due to differences observed between damaged and regular ripe tissue (0.044 and 0.025, respectively). The proposed multi-scale approach could improve the understanding of CI as a complex disorder to the development of novel techniques to avoid this postharvest issue at different observation scales.

Evaluation of cortical and trabecular bone structure of the mandible in patients using L-Thyroxine

BACKGROUND

Long-term use of L-Thyroxine (LT4), the synthetic thyroxine hormone used for thyroid hormone replacement therapy, is an important risk factor for osteoporosis. The aim of this study was to investigate the differences between mandibular cortical index (MCI) and trabecular bone fractal dimension (FD) values on panoramic radiographs of patients using LT4 and control subjects.

METHODS

A total of 142 female patients, 71 cases and 71 controls, were analyzed in the study. Ages were matched in case and control groups and the mean age was 36.6 ± 8.2 (18 to 50) years. MCI consisting of C1 (Normal Mandibular Cortex), C2 (Moderately Resorbed Mandibular Cortex) and, C3 (Severely Resorbed Cortex) scores was determined for case and control groups. Fractal analysis was performed using ImageJ on selected regions of interest from the gonial and interdental regions. The box-count method was used to calculate FD values. Wilcoxon signed-rank test, Mann-Whitney U test, and Spearman correlation analysis were applied to compare the measurements. Statistical significance of differences was established at P < 0.05 level.

RESULTS

FD values did not show statistically significant differences between case and control groups (p > 0.05). The mean FD in the right gonial region was 1.38 ± 0.07 in the case group and 1.38 ± 0.08 in the control group (p = 0.715). The mean FD in the right interdental region was 1.37 ± 0.06 in the cases and 1.36 ± 0.06 in the control group (p = 0.373). The mean FD in the left gonial region was 1.39 ± 0.07 in the cases and 1.39 ± 0.07 in the control group (p = 0.865). The mean FD in the left interdental region is 1.37 ± 0.06 in the cases and 1.38 ± 0.05 in the control group (p = 0.369). The most common MCI score was C1, with 62% in the cases and 83.1% in the control group. MCI scores showed a statistically significant difference between cases and controls (p = 0.016, p < 0.05). While the C2 score was higher in the cases, the C1 score was higher in the controls.

CONCLUSIONS

LT4 use was not associated with the FD of mandibular trabecular bone, but was associated with MCI values of cortical bone. Further studies on larger samples with different imaging modalities and image processing methods are needed.

Fractal analysis of the mandible cortical bone: correlation among fractal dimension values obtained by two processing methods from periapical radiograph and micro-computed tomography with cone-beam computed tomography

The objectives of the present study were to assess Fractal Dimension (FD) values in the mandible cortical bone obtained from digital periapical radiographs (DPR), high-resolution microtomography (µCT), and cone-beam computed tomography (CBCT), by two processing methods: binarization (FD.b) and grayscale-based method (FD.f) and, finally, to identify the correlation among these values with other micro-architectural parameters. For this, a prospective study was conducted on 18 healthy individuals (mean age 23 ± 2.4 years old) who underwent third molar extraction. Pre-operative CBCT scans were conducted, bone fragments were removed from the retro-molar region, and DPR and µCT were performed on those bone samples. FD.b and FD.f values were calculated using three parasagittal sections for CBCT, one image for DPR, and three sections for µCT. The 3D bone microarchitecture was analyzed in µCT (voxel size: 19 µm). As a result, FD.b mean values of 1.55 ± 0.02 and 1.80 ± 0.01 were obtained for CBCT and µCT, respectively. Furthermore, FD.f mean values of 1.22 ± 0.12 for DPR, 0.99 ± 0.04 for CBCT, and 1.30 ± 0.07 for µCT were obtained. Both FD.b and FD.f values showed a good agreement. FD.f was negatively correlated with the standard deviation of the mean gray value (p = 0.003) for DPR and intra-cortical bone surface (p = 0.02) for µCT. In conclusion, image processing with or without binarization revealed different values for FD, although showing agreement. The grayscale-based method retrieved FD values correlated with the gray levels and the cortical porous network, which means that FD can be a valuable index for mandibular cortical bone evaluation. FD is associated with mineralization and microarchitecture. Nevertheless, there was no correlation between FD values obtained from low- (DPR) and high-resolution (µCT) X-ray modalities with FD obtained from the in vivo CBCT.

Evaluation of mandibular osseous structure in patients with mandibular asymmetry: a fractal analysis study

OBJECTIVE

We evaluated the effect of mandibular asymmetry on the trabecular structure of the mandible as measured through fractal analysis (FA).

STUDY DESIGN

We divided a sample of 105 patients with skeletal class I occlusion, cervical vertebral maturation CS6, and skeletal vertical dimension ratios within normal limits into right asymmetric, left asymmetric, and symmetric groups. We performed FA on 6 bilateral regions of interest on panoramic radiographs of the patients and calculated the mean fractal dimension (FD) for each region. We performed the Wilcoxon signed-rank and paired t tests to compare the significance of differences in FD between sides within each group and between groups for all regions. Statistical significance was established at P < .05.

RESULTS

We found statistically significant differences in mean FD values between the right and left condyles of the 2 asymmetric patient groups. The FD was greater in the left condyle of patients with right asymmetry and in the right condyle of patients with left asymmetry. The right condyle had a significantly greater FD in left asymmetric patients than in right asymmetric patients.

CONCLUSIONS

The results of FA indicate that asymmetry is characterized by an increase in the mean FD of the condyle that is responsible for the asymmetry. Fractal analysis can be a valuable diagnostic technique in distinguishing trabecular differences in the condylar areas of asymmetric individuals.

Effects of functional orthopedic treatment on mandibular trabecular bone in class II patients using fractal analysis

PURPOSE

The aim of this retrospective study was to evaluate the effects of functional orthopedic treatment on mandibular bone structure using fractal dimension (FD) analysis of panoramic radiographs.

METHODS

The study material consisted of the pre- and posttreatment digital panoramic radiographs of 80 patients (mean age 10.1 ± 2.01 years; 45 girls, 35 boys) with class II malocclusion who were treated with the monoblock or twin block appliances. The following regions of interest (ROI) were selected: ROI1, condylar process; ROI2, angulus mandibulae; ROI3, corpus mandibulae; and ROI4, mental foramen. Pre- and posttreatment FD values were compared for each ROI.

RESULTS

FD values of the mandibular condyle did not change with the functional orthodontic treatment. FD values of the mandibular corpus region had the highest pretreatment values and significantly decreased with treatment (p < 0.05).

CONCLUSION

Functional orthopedic treatment altered the trabeculation of the mandibular bone, but it is speculated that the changes in the occlusal forces seemed to be of primary significance for this effect.

Evaluation of mandibular trabecular and cortical bone by fractal analysis and radiomorphometric indices in bruxist and non-bruxist patients

BACKGROUND

The aim of this study was to evaluate the effect of bruxism on the cortical and trabecular bone of the mandible using the radiomorphometric indexes and fractal analysis (FA) additionally to examine the efficiency of FA as diagnostic test for bruxism.

METHODS

Evaluation was performed on panoramic radiographs of 94 bruxists and 94 non-bruxist individuals with the ImageJ program. Cortical bone was assessed with mandibular cortical index, mental index, and panoramic mental index. Trabecular bone in the condyle, gonial, and corpus region was evaluated by FA. An independent sample t and Mann-Whitney-U tests and Pearson and Spearman rank correlations were conducted for statistical analysis.

RESULTS

A total of 188 participants, 112 female, and 76 male, were included in the study. The sample age ranged from 18 to 43, with a mean of 27.55 (± 7.022) years. FA values of the angulus were significantly higher than those of the condyle and corpus, and the mean of the sample for the angulus, condyle, and corpus, respectively, were; 1.36 (± 10), 1.10 (± 0.9), 1.13 (± 0.8). There was a positive correlation between FA of the mandibular corpus and age (r = .163, p = .025). Females' values were smaller than males' in the FAs of three regions, and significant differences were found in FA of the condyle and angulus of the mandible, MCI, and PMI according to gender. There was no statistically significant difference between bruxist and non-bruxist patients in term of FAs of three regions, MCI, MI, and PMI values (p > .05).

CONCLUSIONS

FA of the condyle and angulus of the mandible, MCI, and PMI are significantly affected by gender. However bruxism doesn't cause a significant change in the fractal dimensions of the bone in the mandible and doesn't change substantially MCI, MI, and PMI.

Mechanical Properties, Fractal Dimension, and Texture Analysis of Selected 3D-Printed Resins Used in Dentistry That Underwent the Compression Test

Three-dimensional printing is finding increasing applications in today’s world. Due to the accuracy and the possibility of rapid production, the CAD/CAM (computer-aided design/computer-aided manufacturing) technology has become the most desired approach in the preparation of elements, especially in medicine and dentistry. This study aimed to compare the biomechanical properties, fractal dimension (FD), and texture of three selected materials used for 3D printing in dentistry. Three biomaterials used in 3D printing were evaluated. The materials were subjected to the compression test. Then, their mechanical features, FD, and texture were analyzed. All the tested materials showed different values for the studied properties. The only statistically insignificant difference was observed for the force used in the compression test. All three materials showed differences in width and height measurements. The difference in the decrease between the compression plates was also significant. For Dental LT Clear, the mean value was 0.098 mm (SD = 0.010), while for BioMed Amber it was 0.059 mm (SD = 0.019), and for IBT it was 0.356 mm (SD = 0.015). The nominal strain also differed between the materials. IBT had the highest mean value (7.98), while BioMed Amber had the smallest (1.31). FD analysis revealed that Dental LT Clear did not show differences in the structure of the material. The other two materials showed significant changes after the compression test. Texture analysis (TA) revealed similar results: BioMed Amber resin showed significantly less pronounced texture changes compared to the other two materials. BioMed Amber also showed the most stable mechanical properties, whereas those of IBT changed the most. Fractal analysis revealed that IBT showed significant differences from the other two materials, whereas TA showed that only Dental LT Clear did not show changes in its texture after the compression test. Before the compression, however, BioMed Amber differed the most when bone index was taken into account.

Fractal analysis of dental periapical radiographs: A revised image processing method

OBJECTIVE

To assess trabecular bone structure as calculated with fractal analysis by 2 binarization processes: White and Rudolph's original method (WR.o) and a revised version (WR.r). Fractal dimension (FD) values calculated with WR.r (FD.r) and a gray-scale-based method (FD.f) were also compared. FD, histogram parameters, and lacunarity were compared by dentate status, jaw location, and sex.

STUDY DESIGN

Regions of interest from digital periapical radiographs were defined below the teeth roots and in the edentulous sites of 37 patients. Histograms were assessed for pixel values. Binarization was performed with WR.o and then with WR.r, in which the outliers were removed. FD was assessed using WR.r (FD.r) and (FD.f). Histograms were assessed to obtain pixel values. Lacunarity was calculated.

RESULTS

WR.r revealed fewer trabeculae, branches, and junctions than WR.o (P < .0001). The majority of the mean differences between FD.r and FD.f were within the 95% CI. Dentate areas had greater mean gray levels than partially edentulous areas (P = .0027). FD.f was higher in the mandible (P = .01), but gray-level SD (P < .0001) and lacunarity (P = .02) were greater in the maxilla. FD.f and lacunarity were higher (P = .0005) and lower (P = .0014) in males, respectively.

CONCLUSION

WR.r was effective in revealing skeletonized bone trabeculae by removing non-trabecular noise. FD.r and FD.f revealed good agreement. FD.f, histogram parameters, and lacunarity differed based on dentate status, jaw location, and sex.

Evaluation of the effects of prolotherapy on condyles in temporomandibular joint hypermobility using fractal dimension analysis

Objectives

Prolotherapy is a method that has gained popularity in recent years and has been reported to have positive short-term and long-term clinical results in maxillofacial surgery, especially temporomandibular joint (TMJ) hypermobility. This study aimed to evaluate the changes in the trabecular structure of mandibular condyles in patients who underwent prolotherapy due to TMJ hypermobility using the fractal analysis method.

Materials and Methods

Forty-five patients who received dextrose prolotherapy at a concentration of 20% and fifteen control patients were included in the study. All patients had panoramic radiographs just before (T0) and six months after treatment (T1). The patients who received treatment were divided into three groups according to the number of prolotherapy injections. The regions of interest were selected from bone areas close to the articular surfaces of the condyles. The fractal dimension (FD) values were calculated.

Results

The main effect of time on the FD value was significant [F (1, 56)=86.176, P<0.001]. This effect was qualified by a significant time×group interaction effect [F (3, 56)=9.023, P<0.001]. The decreases in FD values in all treatment groups between T0 and T1 times were significant (P=0.004). However, changes in FD values were not significant in the control group (P=0.728).

Conclusion

Dextrose prolotherapy without the effect of the number of injections caused a decrease in FD values in the mandibular condyles over time.

Comparison of cone-beam computed tomography and digital panoramic radiography for detecting peri-implant alveolar bone changes using trabecular micro-structure analysis

Objectives

We compared changes in fractal dimension (FD) and grayscale value (GSV) of peri-implant alveolar bone on digital panoramic radiography (DPR) and cone-beam computed tomography (CBCT) immediately after implant surgery and 12 months postoperative.

Materials and Methods

In this retrospective study, 16 patients who received posterior mandibular area dental implants with CBCT scans taken about 2 weeks after implantation and one year after implantation were analyzed. A region of interest was selected for each patient. FDs and GSVs were evaluated immediately after implant surgery and at 12-month follow-up to examine the functional loading of the implants.

Results

There were no significant differences between DPR and CBCT measurements of FD values (P>0.05). No significant differences were observed between FD values and GSVs calculated after implant surgery and at the 12-month follow-up (P>0.05). GSVs were not correlated with FD values (P>0.05).

Conclusion

The DPR and reconstructed panoramic CBCT images exhibit similar image quality for the assessment of FD. There were no changes in FD values or GSVs of the peri-implant trabecular bone structure at the 12-month postoperative evaluation of the functional loading of the implant in comparison to values immediately after implantation. GSVs representing bone mass do not align with FD values that predict bone microstructural parameters. Therefore, GSVs and FDs should be considered different parameters for assessing bone quality.

Digital panoramic radiography as a tool for analyzing the quality of trabecular bone microarchitecture

Abstract Introduction Osteoporosis is a metabolic disease characterized by reduced bone mineral density, often accompanied by loss of quality of trabecular bone microarchitecture. Objective To assess the quality or degradation of trabecular bone microarchitecture in digital panoramic radiography to better predict the risk of fragility fractures. Material and method The sample included 68 female patients, age-matched, and divided into three groups according to densitometric results. Trabecular Bone Score values were measured and digital panoramic radiographs were taken. Fractal analysis with box counting was conducted in the region of premolars and angle of the mandible, with regions of interest measuring 64×64 and 80×120 pixels. In the statistical analysis, Pearson’s correlation was applied between the Trabecular Bone Score and fractal analysis results obtained in each group, using age as a control variable and assigning individualized age ranges within groups. Result A moderate correlation was identified in the regions of interest of 64×64 and 80×120 pixels at the angle of the mandible in the osteoporosis group and in the normal group. A moderate correlation was also obtained using age as a control variable in the 64x64 pixel regions of interest in the premolar region. Considering age range, the within-group analysis presented a strong correlation in the osteoporosis group and moderate correlation in the osteopenia and normal groups. Conclusion Fractal analysis in digital panoramic radiographs was shown to be a promising predictive instrument of bone microarchitecture quality.

Evaluation of trabecular bone healing using fractal dimension analysis after augmentation of alveolar crests with autogenous bone grafts: a preliminary study

OBJECTIVE

The aim of this study is to evaluate bone remodeling after alveolar crest augmentation with autogenous bone grafts.

METHODS

50 patients who were applied augmentation due to alveolar deficiency were included in this study. Fractal dimensions were measured on the radiographs in the preoperative, postoperative, follow-up periods. The ROI was selected specific to each patient, but repeated in a standardized manner on subsequent radiographs.

RESULTS

A total of 50 patients were included in the study; There were 31 females and 19 males. Implants were placed in all patients without any complications. The mean fractal dimensions on the graft recipient side were statistically higher in the postoperative 5th month compared to the postoperative 1st week (p = 0.002). The mean fractal dimensions on the donor side were statistically higher in the preoperative and postoperative 5th month compared to the postoperative 1st week (p < 0.001).

CONCLUSION

Any clinical imaging method cannot fully reflect the histological microstructures of the bone. Evaluating the fractal analysis together with the clinical results can demonstrate adequate bone healing and quality prior to implant placement. Fractal analysis is a non-invasive, reproducible, method but further, prospective, randomized, controlled clinical studies are needed to estimate bone quality prior to implant placement.

Fractal dimension and lacunarity analysis of mandibular bone on digital panoramic radiographs of tobacco users

Background. This study aimed to evaluate and compare changes in the mandibular trabecular bone pattern using the fractal dimension (FD) and lacunarity analysis in tobacco users with healthy controls.

Methods. This study was carried out on digital panoramic radiographs of 225 subjects divided into three groups: smokeless tobacco users (SLTs), smokers, and control (n=75). ImageJ program with FracLac plugin was used to assess the FD and lacunarity of mandibular trabecular bone on the digital panoramic radiographs.

Results. The differences in the mean FD values of the study and control groups were statistically significant (P < 0.001). Mean FD was lower in the case groups than the control group, with SLTs having the least FD value. A significant difference in lacunarity was noted between SLTs and controls (P < 0.001). On the contrary, there was no significant difference in lacunarity between smokers and controls.

Conclusions. FD values were lower in tobacco users, suggesting that tobacco users have a less complex trabecular bone pattern than healthy controls. Higher lacunarity values in SLTs indicated a more heterogeneous bone pattern. These findings signify that FD and lacunarity analysis on digital panoramic radiographs can serve as promising predictive tools to assess bone quality for osteoporotic changes in tobacco users, thereby facilitating prompt referral for further management.

Validity of fractal analysis of implants in individuals with healthy and diseased peri-implant mucosa

OBJECTIVE

The purpose of this study was to determine whether fractal analysis could discriminate the peri-implant trabecular bone between individuals with healthy peri-implant mucosa and peri-implant disease using digital periapical radiographs.

MATERIAL AND METHODS

The electronic health records of patients with a dental implant were reviewed to determine their eligibility. One hundred four patients (aged 27-89 years) were included and divided into three groups. Group 1) Individuals with healthy peri-implant mucosa; Group 2) Individuals with peri-implant mucositis; or Group 3) Individuals with peri-implantitis. The following clinical measurements for each dental implant were extracted: probing depth (PD), clinical attachment level (CAL), and the presence or absence of bleeding on probing (BOP). Digital periapical images of the implant were used to calculate the fractal dimension (FD) for each implant at two regions of interest (ROI). Summary statistics were calculated for mean PD, mean CAL, mean percent BOP, and mean FD by group. Differences among groups were tested using one-way analysis of variance (ANOVA). Spearman nonparametric correlations were tabulated for mean PD, mean CAL, mean percent BOP, and mean FD.

RESULTS

The only measure that did not demonstrate significant differences among groups was FD (p = .559) with all other measures demonstrating a significant difference (p < .001).

CONCLUSIONS

Based on this study, FD of the peri-implant bone calculated from a periapical radiograph does not appear to be a valid method to distinguish between healthy and diseased implants, while clinical measures of PD, CAL, and BOP are useful for the diagnosis of peri-implant health, peri-implant mucositis, and peri-implantitis.

Mandibular radiomorphometric parameters of women with cemento-osseous dysplasia

OBJECTIVE

To compare the radiomorphometric parameters of mandibular trabecular and cortical bone of females with and without cemento-osseous dysplasia (COD).

METHODS

A retrospective cross-sectional paired study was conducted. Digital panoramic radiographs were obtained from females diagnosed in a public service of Oral Medicine. The participants were divided into two groups of 50 subjects each: females with a diagnosis of COD (COD group) and females without a diagnosis of COD (non-COD group), randomly chosen from the image database and paired for age. The radiomorphometric parameters analyzed were: mandibular cortical width (MCW), fractal dimension (FD) and mandibular cortical index (MCI). The paired t-test and Wilcoxon test were used to compare MCW and FD values and the McNemar-Bowker test compared the MCI.

RESULTS

The mean age of both groups was 46.84 ± 11.38 years. The median MCW index was 3.12 mm (2.15-4.55) for the COD group and 3.52 mm (1.90-4.70) for the non-COD group (p = 0.034). The mean FD value of the COD group (1.2039 ± 0.0926) was lower than that of the non-COD group (1.2472 ± 0.0894) in the anatomical region of the interest of mandibular cortical bone (p = 0.031), while no difference was detected in alveolar trabecular bone. The C3 degree of MCI was more frequent in the COD group (p = 0.009).

CONCLUSION

Females with COD had lower values of radiomorphometric parameters in mandibular cortical bone than females of the same age without COD. These results suggest that, in addition to the dental care recommended in the literature, COD females also require more attention and screening for low bone mineral density.

Evaluation of the mandibular trabecular bone in patients with bruxism using fractal analysis

OBJECTIVE

The aims of this study were (1) to investigate the effect of bruxism on the fractal dimension (FD) of the mandibular trabecular bone through digital panoramic radiographs, and (2) to evaluate the effectiveness of fractal analysis as a diagnostic test for bruxism.

METHODS

One hundred and six bruxer and 106 non-bruxer patients were included in the study. Three bilateral regions of interest (ROI) were selected: ROI-1, the mandibular condyle; ROI-2, the mandibular angle; ROI-3, the-area between the apical regions of the mandibular second premolar and the first molar teeth. FD values for the bruxer and non-bruxer groups were compared for each ROI.

RESULTS

Only the FD measurements for the right mandibular condyle (ROI-1) showed a statistically significant difference (p = 0.041) between the bruxer and non-bruxer individuals. FD values measured in the bruxers (1.40 ± 0.09) were lower than in the non-bruxers (1.42 ± 0.08).

CONCLUSION

Fractal analysis may be a useful method for discerning trabecular differences in the condylar areas of bruxer individuals. In future studies, the unilateral mastication habits, the characteristics of dental wear, and the occlusal bite forces of individuals should be documented.

Evaluation of bone texture imaging parameters on panoramic radiographs of patients with Sheehan's syndrome: a STROBE-compliant case-control study

Sheehan's syndrome (SHS) is a rare condition related to the risk of osteoporosis and evaluation of bone texture imaging features on panoramic radiographs would be suitable for this condition, which was the aim of the present study. Fractal dimension, lacunarity, and trabecular morphologic aspects were significantly altered in these patients.

INTRODUCTION

SHS is an important public health problem particularly in developing countries. It is characterized as postpartum hypopituitarism secondary to obstetric complications-related ischemic pituitary necrosis that shows significant systemic metabolic repercussions. Thus, this study aimed to evaluate bone texture parameters in digital panoramic radiographs of patients with SHS.

METHODS

A case-control study was conducted with 30 SHS patients from an Endocrinology and Diabetology Service of reference in Brazil, and 30 age- and sex-matched healthy controls. A custom computer program measured fractal dimension, lacunarity, and some morphologic features in the following mandibular regions of interest (50 × 50 pixels): below the mental foramen (F1), between the first and second molars (M1), and at the center of the mandibular ramus (R1).

RESULTS

The fractal analysis showed a statistically significant difference between the studied groups in all regions of interest. The fractal dimension in F1 (p = 0.016), M1 (p = 0.043), and R1 (p = 0.028) was significantly lower in SHS group, as well as lacunarity in R1 (p = 0.008). Additionally, several morphologic features were statistically significant in the SHS group (p < 0.05).

CONCLUSION

Therefore, individuals with SHS showed altered imaging texture parameters on panoramic radiographs, which reflect a smaller spatial organization of the bone trabeculae and, possibly, a state of reduced mineral bone density.

Use of fractal analysis in dental images: a systematic review

OBJECTIVES

This study reviewed the use of fractal analysis (FA) in dental images.

METHODS

A search was performed using PubMed, MEDLINE, LILACS, Web of Science and SCOPUS databases. The inclusion criteria were human studies in the English language, with no date restriction.

RESULTS

78 articles were found in which FA was applied to panoramic radiographs (34), periapical radiographs (21), bitewing radiographs (4), cephalometric radiograph (1), cone beam CT (15), micro-CT (3), sialography (2), and ultrasound (2). Low bone mineral density (21) and systemic or local diseases (22) around the bone of dental implants were the main subjects of the study of FA. Various sizes and sites of the regions of interest were used to evaluate the bone structure. Different ways were used to treat the image and to calculate FA. FA of 43 articles showed significant differences in the comparison of groups, mainly between healthy and sick patients.

CONCLUSIONS

FA in Dentistry has been widely applied to the study of images. Panoramic and periapical radiographs were those most frequently used. The Image J software and the box-counting method were extensively adopted in the studies reviewed herein. Further studies are encouraged to improve clarification of the parameters that directly influence FA.

A "best fit" approach for synergistic surface parameters to guide the design of candidate implant surfaces

Human bone resorption surfaces can provide a template for endosseous implant surface design. We characterized the topography of such sites using four synergistic parameters (fractal dimension, lacunarity, porosity, and surface roughness) and compared the generated values with those obtained from two groups of candidate titanium implant surfaces. For the first group (n = 5/group): grit-blasted acid etched (BAE), BAE with either discrete calcium phosphate crystal deposition or nanotube formation, machined titanium with nanotubes, or a nanofiber surface; each measured synergistic parameter was statistically compared with that of the resorbed bone surface and scored for inclusion in a "best fit" analysis. The analysis informed changes that could be made to a candidate implant surface to render it a closer "best fit" to that of the resorbed bone surface. In a second group of either titanium or titanium alloy implants their micro-topography, created by dual acid etching, was the same for each material substrate; but their nanotopographic complexity was changed by varying the degree of calcium phosphate crystalline deposits. These implants were also used in vivo where bone anchorage was tested using a tensile disruption test; and the "best fit" of synergistic parameters coincided with the best biological outcome for both titanium and titanium alloy implants. In conclusion, the four chosen synergistic parameters can be used to guide the sub-micron surface design of candidate implants, and our "best fit" approach is capable of identifying the surfaces with the best biological outcomes. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2165-2177, 2019.

Alternative cone-beam computed tomography method for the analysis of bone density around impacted maxillary canines

INTRODUCTION

Genetic and environmental etiologic factors have been described for maxillary canine impaction, except for the trabecular bone characteristics in the impacted area. The aim of this study was to evaluate the surface area and fractal dimension of the alveolar bone on cone-beam computed tomography (CBCT) images of patients with maxillary impacted canines.

METHODS

The sample comprised preorthodontic treatment CBCT images of 49 participants with maxillary impacted canines (31 unilateral and 18 bilateral). CBCT images were acquired in portrait mode (17 × 23 cm high field of view) at 120 kV, 5 mA, 8.9-seconds exposure time, and 0.3-mm voxel size. Coronal slices (0.3 mm) were obtained from the right and left alveolar processes between the first and second maxillary premolars. We collected 64 × 64-pixel regions of interest between the premolars to assess maxillary bone area and fractal dimension using ImageJ software (National Institutes of Health, Bethesda, Md). Comparisons were made using paired t tests and linear regression. Repeated measurements were obtained randomly from about 20% of the sample.

RESULTS

In subjects with unilateral impactions, the maxillary bone area (P = 0.0227) was higher in the impacted side, with a mean difference of 245.5 pixels (SD, 569.2), but the fractal dimension (P = 0.9822) was not, -0.0003 pixels (SD, 0.082). Comparisons of unilateral and bilateral subjects using a general linear mixed model test confirmed the increased bone area in the impacted side (P = 0.1062). The repeated measurements showed similar results.

CONCLUSIONS

The maxillary alveolar bone area is increased in the impacted side compared with the nonimpacted side.

Evaluation of trabecular pattern of mandible using fractal dimension, bone area fraction, and gray scale value: comparison of cone-beam computed tomography and panoramic radiography

OBJECTIVE

This study was performed to compare the fractal dimension (FD), bone area fraction (BAF), and gray scale value (GSV) on digital panoramic radiography (DPR) and cross-sectional cone-beam computed tomography (CBCT) using image analysis and to determine whether a relationship exists among parameters associated with bone quality.

METHODS

Thirty edentulous human hemimandibles were scanned by DPR and CBCT. Ninety regions of interest (ROIs) were evaluated on DPR and CBCT images to calculate the FD and BAF. The GSV of the ROI on CBCT was also calculated.

RESULTS

Statistically significant differences were observed in the FD values of the ROIs between DPR and CBCT (p = 0.002) and in the BAF values of ROIs between DPR and CBCT (p = 0.017). The Spearman's correlation test revealed a statistically significant high correlation between the FD and BAF values of the ROIs on DPR and between the FD and BAF values of the ROIs on CBCT (p < 0.01). No significant correlations were observed between the GSVs of ROIs on CBCT and the FD values of ROIs on DPR, the BAF values of ROIs on DPR, the FD values of ROIs on CBCT, and the BAF values of ROIs on CBCT (p > 0.05).

CONCLUSIONS

The GSV did not support the FD and BAF. Additionally, DPR and CBCT did not have similar image quality for assessing the FD, BAF, and GSV. In evaluating the trabecular structure, the use of panoramic radiographs should be continued because the image resolution of CBCT is lower and its generalized dose is higher than that of panoramic radiography. These results may serve as a reference for clinical practitioners using dental CBCT to analyze the trabecular structures of alveolar bones.

Inclusion of periodontal ligament fibres in mandibular finite element models leads to an increase in alveolar bone strains

Alveolar bone remodelling is vital for the success of dental implants and orthodontic treatments. However, the underlying biomechanical mechanisms, in particular the function of the periodontal ligament (PDL) in bone loading and remodelling, are not well understood. The PDL is a soft fibrous connective tissue that joins the tooth root to the alveolar bone and plays a critical role in the transmission of loads from the tooth to the surrounding bone. However, due to its complex structure, small size and location within the tooth socket it is difficult to study in vivo. Finite element analysis (FEA) is an ideal tool with which to investigate the role of the PDL, however inclusion of the PDL in FE models is complex and time consuming, therefore consideration must be given to how it is included. The aim of this study was to investigate the effects of including the PDL and its fibrous structure in mandibular finite element models. A high-resolution model of a human molar region was created from micro-computed tomography scans. This is the first time that the fibrous structure of the PDL has been included in a model with realistic tooth and bone geometry. The results show that omission of the PDL creates a more rigid model, reducing the strains observed in the mandibular corpus which are of interest when considering mandibular functional morphology. How the PDL is modelled also affects the strains. The inclusion of PDL fibres alters the strains in the mandibular bone, increasing the strains in the tooth socket compared to PDL modelled without fibres. As strains in the alveolar bone are thought to play a key role in bone remodelling during orthodontic tooth movement, future FE analyses aimed at improving our understanding and management of orthodontic treatment should include the fibrous structure of the PDL.

Relationship between necrotic patterns in glioblastoma and patient survival: fractal dimension and lacunarity analyses using magnetic resonance imaging

Necrosis is a hallmark feature of glioblastoma (GBM). This study investigated the prognostic role of necrotic patterns in GBM using fractal dimension (FD) and lacunarity analyses of magnetic resonance imaging (MRI) data and evaluated the role of lacunarity in the biological processes leading to necrosis. We retrospectively reviewed clinical and MRI data of 95 patients with GBM. FD and lacunarity of the necrosis on MRI were calculated by fractal analysis and subjected to survival analysis. We also performed gene ontology analysis in 32 patients with available RNA-seq data. Univariate analysis revealed that FD < 1.56 and lacunarity > 0.46 significantly correlated with poor progression-free survival (p = 0.006 and p = 0.012, respectively) and overall survival (p = 0.008 and p = 0.005, respectively). Multivariate analysis revealed that both parameters were independent factors for unfavorable progression-free survival (p = 0.001 and p = 0.015, respectively) and overall survival (p = 0.002 and p = 0.007, respectively). Gene ontology analysis revealed that genes positively correlated with lacunarity were involved in the suppression of apoptosis and necrosis-associated biological processes. We demonstrate that the fractal parameters of necrosis in GBM can predict patient survival and are associated with the biological processes of tumor necrosis.

Feasibility of cone beam computed tomography radiomorphometric analysis and fractal dimension in assessment of postmenopausal osteoporosis in correlation with dual X-ray absorptiometry

OBJECTIVES

The aim of the present study was to assess the feasibility of using mandibular CBCT radiomorphometric indices and box-counting fractal dimension (FD) to detect osteoporosis in post-menopausal females, compare them with the healthy control group and to correlate the findings with the bone mineral density measured by dual X-ray absorptiometry (DXA).

METHODS

This study consisted of 50 post-menopausal females, with age ranging from 55 to 70 years. Based on their DXA results, they were classified into osteoporotic and control groups. Mandibular CBCT radiomorphomertic indices and FD analysis were measured.

RESULTS

Significant differences were found for the CT cortical index scores (CTCI), CT mental index (CTMI) and CT mandibular index (CTI) between the control and osteoporotic groups. The control group showed higher mean values than the osteoporotic group. For FD values, no significant differences were found between the two groups.

CONCLUSIONS

CBCT radiomorphometric indices could be used as an adjuvant tool to refer patients at risk of osteoporosis for further assessment.

Using Fractal and Local Binary Pattern Features for Classification of ECOG Motor Imagery Tasks Obtained from the Right Brain Hemisphere

The feature extraction and classification of brain signal is very significant in brain–computer interface (BCI). In this study, we describe an algorithm for motor imagery (MI) classification of electrocorticogram (ECoG)-based BCI. The proposed approach employs multi-resolution fractal measures and local binary pattern (LBP) operators to form a combined feature for characterizing an ECoG epoch recording from the right hemisphere of the brain. A classifier is trained by using the gradient boosting in conjunction with ordinary least squares (OLS) method. The fractal intercept, lacunarity and LBP features are extracted to classify imagined movements of either the left small finger or the tongue. Experimental results on dataset I of BCI competition III demonstrate the superior performance of our method. The cross-validation accuracy and accuracy is 90.6% and 95%, respectively. Furthermore, the low computational burden of this method makes it a promising candidate for real-time BCI systems.

Feasibility of cone beam computed tomography radiomorphometric analysis and fractal dimension in assessment of postmenopausal osteoporosis in correlation with dual X-ray absorptiometry

OBJECTIVES

The aim of the present study was to assess the feasibility of using mandibular CBCT radiomorphometric indices and box-counting fractal dimension (FD) to detect osteoporosis in post-menopausal females, compare them with the healthy control group and to correlate the findings with the bone mineral density measured by dual X-ray absorptiometry (DXA).

METHODS

This study consisted of 50 post-menopausal females, with age ranging from 55 to 70 years. Based on their DXA results, they were classified into osteoporotic and control groups. Mandibular CBCT radiomorphomertic indices and FD analysis were measured.

RESULTS

Significant differences were found for the CT cortical index scores (CTCI), CT mental index (CTMI) and CT mandibular index (CTI) between the control and osteoporotic groups. The control group showed higher mean values than the osteoporotic group. For FD values, no significant differences were found between the two groups.

CONCLUSIONS

CBCT radiomorphometric indices could be used as an adjuvant tool to refer patients at risk of osteoporosis for further assessment.

Fractal and Lacunarity Analyses: Quantitative Characterization of Hierarchical Surface Topographies

Biomimetic hierarchical surface structures that exhibit features having multiple length scales have been used in many technological and engineering applications. Their surface topographies are most commonly analyzed using scanning electron microscopy (SEM), which only allows for qualitative visual assessments. Here we introduce fractal and lacunarity analyses as a method of characterizing the SEM images of hierarchical surface structures in a quantitative manner. Taking femtosecond laser-irradiated metals as an example, our results illustrate that, while the fractal dimension is a poor descriptor of surface complexity, lacunarity analysis can successfully quantify the spatial texture of an SEM image; this, in turn, provides a convenient means of reporting changes in surface topography with respect to changes in processing parameters. Furthermore, lacunarity plots are shown to be sensitive to the different length scales present within a hierarchical structure due to the reversal of lacunarity trends at specific magnifications where new features become resolvable. Finally, we have established a consistent method of detecting pattern sizes in an image from the oscillation of lacunarity plots. Therefore, we promote the adoption of lacunarity analysis as a powerful tool for quantitative characterization of, but not limited to, multi-scale hierarchical surface topographies.

Directional fractal signature methods for trabecular bone texture in hand radiographs: data from the Osteoarthritis Initiative

PURPOSE

To develop directional fractal signature methods for the analysis of trabecular bone (TB) texture in hand radiographs. Problems associated with the small size of hand bones and the orientation of fingers were addressed.

METHODS

An augmented variance orientation transform (AVOT) and a quadrant rotating grid (QRG) methods were developed. The methods calculate fractal signatures (FSs) in different directions. Unlike other methods they have the search region adjusted according to the size of bone region of interest (ROI) to be analyzed and they produce FSs defined with respect to any chosen reference direction, i.e., they work for arbitrary orientation of fingers. Five parameters at scales ranging from 2 to 14 pixels (depending on image size and method) were derived from rose plots of Hurst coefficients, i.e., FS in dominating roughness (FSSta), vertical (FSV) and horizontal (FSH) directions, aspect ratio (StrS), and direction signatures (StdS), respectively. The accuracy in measuring surface roughness and isotropy/anisotropy was evaluated using 3600 isotropic and 800 anisotropic fractal surface images of sizes between 20 × 20 and 64 × 64 pixels. The isotropic surfaces had FDs ranging from 2.1 to 2.9 in steps of 0.1, and the anisotropic surfaces had two dominating directions of 30° and 120°. The methods were used to find differences in hand TB textures between 20 matched pairs of subjects with (cases: approximate Kellgren-Lawrence (KL) grade ≥ 2) and without (controls: approximate KL grade <2) radiographic hand osteoarthritis (OA). The OA Initiative public database was used and 20 × 20 pixel bone ROIs were selected on 5th distal and middle phalanges. The performance of the AVOT and QRG methods was compared against a variance orientation transform (VOT) method developed earlier [M. Wolski, P. Podsiadlo, and G. W. Stachowiak, "Directional fractal signature analysis of trabecular bone: evaluation of different methods to detect early osteoarthritis in knee radiographs," Proc. Inst. Mech. Eng., Part H 223, 211-236 (2009)].

RESULTS

The AVOT method correctly quantified the isotropic and anisotropic surfaces for all image sizes and scales. Values of FSSta were significantly different (P < 0.05) between the isotropic surfaces. Using the VOT and QRG methods no differences were found at large scales for the isotropic surfaces that are smaller than 64 × 64 and 48 × 48 pixels, respectively, and at some scales for the anisotropic surfaces with size 48 × 48 pixels. Compared to controls, using the AVOT and QRG methods the authors found that OA TB textures were less rough (P < 0.05) in the dominating and horizontal directions (i.e., lower FSSta and FSH), rougher in the vertical direction (i.e., higher FSV) and less anisotropic (i.e., higher StrS) than controls. No differences were found using the VOT method.

CONCLUSIONS

The AVOT method is well suited for the analysis of bone texture in hand radiographs and it could be potentially useful for early detection and prediction of hand OA.

Fractal analysis for the assessment of trabecular peri-implant alveolar bone using panoramic radiographs

OBJECTIVES

There is no consensus on the relationship between fractal dimension and trabecular bone complexity. Our aims were to examine the changes in fractal dimension (FD) from peri-implant alveolar bone on digital panoramic radiographs 6 and 12 months after prosthodontic loading and to compare these with baseline values calculated just after loading.

MATERIAL AND METHODS

Three panoramic radiographs taken from 76 implant patients taken (1) after prosthodontic loading (3 months ± 2 weeks after insertion = baseline), (2) 6 months ± 2 weeks after loading, and (3) 12 months ±2 weeks after loading were considered for the study. Panoramic images were obtained using storage phosphor plates of the Digora PCT system and saved into a computer. Three regions of interest from mesial, distal, and apical areas were selected for each implant on three consecutive panoramic images. Statistical analysis of the data was performed using two-way repeated measures ANOVA, independent t test and paired t test, and pairwise comparisons (P < 0.05).

RESULTS

Mean FD values at baseline were 1.202, 1.224, and 1.199 for apical, mesial, and distal areas. The FD values were calculated as 1.121, 1.113, and 1.128 at the 6th month. The differences between values calculated at baseline and the 6th month were statistically significant for all aspects, indicating a significant decrease in FD 6 months after prosthodontic loading (P < 0.05). FD values calculated at the 12th month were 1.121, 1.110, and 1.121 for apical, mesial, and distal aspects, respectively, with no significant differences from corresponding values obtained at the 6th month (P > 0.05).

CONCLUSIONS

FD values of trabecular bone around implants 6 months after prosthodontic loading are significantly lower than the baseline values. However, no significant decrease or increase was observed at 12 months, which revealed comparable results with peri-implant alveolar bone at 6 months.

CLINICAL RELEVANCE

Trabecular bone around successful dental implants exhibits lower fractal dimension values 6 months after prosthodontic loading and displays stable bony microstructure at 12 months of follow-up.

Effects of ghrelin on the structural complexity of exocrine pancreas tissue architecture

Recent studies have shown that ghrelin increases pancreatic exocrine secretion. However, the potential effects of ghrelin on the morphology of exocrine pancreas (EP) remain unknown. In this work, using fractal analysis, we demonstrate that centrally administered ghrelin increases structural complexity and tissue disorder in rat EP. The study was carried out on a total of 40 male Wistar rats divided into four groups (n = 10): ghrelin-treated animals (average age, 1.5 months), ghrelin-treated animals (8.5 months), and controls (1.5 and 8.5 months). The pancreas tissue sections were stained with hematoxylin/eosin and visualized by light microscopy. For each animal, the average values of tissue fractal dimension, lacunarity, as well as parameters of co-occurrence matrix texture, were determined using tissue digital micrographs. The results indicate that ghrelin administration increases EP fractal dimension and textural entropy, and decreases lacunarity, regardless of the age. To our knowledge, this is the first study to investigate the effects of ghrelin on the morphological properties of pancreatic tissue, and also the first to apply fractal and textural analysis methods in quantification of EP tissue architecture.

Pixel intensity and fractal dimension of periapical lesions visually indiscernible in radiographs

INTRODUCTION

The purpose of the study was to analyze pixel intensity (PI) and fractal dimension (FD) values in radiographs of chemically created but visually undetectable periapical lesions.

METHODS

Artificial lesions were created by applying 70% perchloric acid to the sockets of left and right first premolars in 12 cadaver mandibles. For preparation of relatively small lesions, the acid was applied for 30 and 60 minutes. Before and after each acid application, radiographs were taken (60 kVp, 7 mA, and 1.5 mm Al equivalent filtration for 0.12 second) with storage phosphor plates. An optical bench was used to standardize projection geometry. Image plates were scanned immediately after exposure, and the acquired images were saved uncompressed in TIF format. Six observers evaluated the images by using a 5-grade scale, and the images scored as "definitely absent" by all observers were used for the calculations of PI and FD. Box-counting FDs and differences in mean PI were computed for regions of interest at the apical areas of each premolar. Repeated-measures analysis of variance, Tukey test, and Pearson correlation coefficient test were used for statistical analysis.

RESULTS

A significant difference was found in FD values after both acid application periods (P < .05), whereas a difference in PI was detected only in images obtained after 60-minute acid application (P < .05). There was a negative correlation between FD and PI values (-0.754, P < .05).

CONCLUSIONS

Calculation of FD can be a tool for the early detection of periapical lesions given the presence of baseline radiographs.

Anatomical variations of trabecular bone structure in intraoral radiographs using fractal and particles count analyses

PURPOSE

This study was performed to evaluate possible variations in maxillary and mandibular bone texture of normal population using the fractal analysis, particles count, and area fraction in intraoral radiographs.

MATERIALS AND METHODS

Periapical radiographs of patients who had full mouth intraoral radiographs were collected. Regions of interest (100×100 pixels) were located between the teeth of the maxillary anterior, premolar, and molar area, as well as the mandibular anterior, premolar, and molar areas. The fractal dimension (FD) was calculated by using the box counting method. The particle count (PC) and area fraction (AF) analyses were also performed.

RESULTS

There was no significant difference in the FD values among the different groups of age, gender, upper, and lower jaws. The mean FD value was 1.49±0.01. The mean PC ranged from 44 to 54, and the mean AF ranged from 10.92 to 11.85. The values of FD, PC, and AF were significantly correlated with each other except for the upper molar area.

CONCLUSION

According to the results, patients with normal trabecular pattern showed a FD of approximately 1.5. Based on these results, further investigation would be recommended if the FD value of patient significantly differenct from this number, since the alteration of this value indicates microstructural modification of trabecular pattern of the jaws. Additionally, with periapical radiographs, simple and cost-effective, PC and AF could be used to assess the deviation from the normal.

Trabecular bone texture detected by plain radiography and variance orientation transform method is different between knees with and without cartilage defects

The objective of this work is to evaluate differences in trabecular bone (TB) texture between subjects with and without tibiofemoral cartilage defects using a variance orientation transform (VOT) method. A case-control study was performed in subjects without radiographic knee osteoarthritis (OA) (K&L grade <2) matched on sex, BMI, age, knee compartment, and meniscectomy where cases (n = 28) had cartilage defects (grade ≥2) and controls (n = 28) had no cartilage defects (grade <2). Cartilage defects were assessed from MRI using validated methods. The VOT was applied to TB regions selected on medial and lateral compartments in knee X-rays and fractal signatures (FS) in the horizontal (FS(H) ) and vertical (FS(V) ) directions, and along the roughest part of TB (FS(Sta) ) and texture aspect ratio signatures (StrS), at different trabecular image sizes (0.30-0.70 mm) were calculated. Compared with controls, FS(V) for cases were higher (p < 0.011) at image sizes 0.30-0.40 mm and 0.45-0.55 mm in the medial compartment. In the lateral compartment, FS(H) and FS(Sta) for cases were higher (p < 0.028) than those for controls at 0.30-0.40 mm and 0.45-0.55 mm, while FS(V) was higher (p < 0.02) at 0.30-0.40 mm. TB texture roughness was greater in subjects with cartilage defects than in subjects without, suggesting thinning and fenestration of TB occur early in OA and that the VOT identifies changes in TB in knees with early cartilage damage. No differences in StrS (p > 0.05) were found.