Hounsfield unit change in root and alveolar bone during canine retraction

Jiang, Feifei; Liu, Sean S.-Y.; Xia, Zeyang; Li, Shuning; Chen, Jie; Kula, Katherine; Eckert, George J.

doi:10.1016/j.ajodo.2014.11.027

Cited by 9 publications

(10 citation statements)

References 22 publications

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“…It had been reported previously that no significant difference of BMD change patterns had been detected in the surrounding alveolar bone under the two treatment strategies . This is in agreement with our stress analysis.…”

Section: Discussionsupporting

confidence: 93%

“…Thus, it is helpful to see whether the initial ME change in terms of each of the stress invariants is related to the BMD reduction, which may indicate whether certain ME change triggers the bone activities. In this discussion, the BMD were expressed in terms of HU as was reported previously .…”

Section: Discussionmentioning

confidence: 99%

“…These are the changes in the stresses due to the initial orthodontic load. The divisions were made and labeled the same way as were reported in the BMD study . This would allow us to compare the stress to the BMD changes.…”

Section: Methodsmentioning

confidence: 99%

“…Compressive stress in PDL is reported to be related to the root resorption in an animal study . Clinical studies had shown the correlation between movement direction and BMD loss . However, to understand the root cause, it is important to understand how the cells sense the ME changes in different tissues.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical environment change in root, periodontal ligament, and alveolar bone in response to two canine retraction treatment strategies

Jiang

Xia

et al. 2015

Orthod Craniofacial Res

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Objective To investigate the initial mechanical environment (ME) changes in root surface, periodontal ligament (PDL), and alveolar bone due to two treatment strategies, low or high moment-to-force ratio (M/F). Setting and Sample Population Indiana University-Purdue University Indianapolis. Eighteen patients who underwent maxillary bilateral canine retraction. Material and method Finite element models of the maxillary canines from the patients were built based on their cone beam computed tomography scans. For each patient, the canine on one side had a specially designed T-loop spring with the M/F higher than the other side. Four stress invariants (1st principal/dilatational/3rd principal/von Mises stress) in the tissues were calculated. The stresses were compared with the bone mineral density (BMD) changes reported previously for linking the ME change to bone modeling/remodeling activities. The correlation was tested by the mixed-model anova. Results The alveolar bone in the direction of tooth movement is primarily in tension, while the PDL is in compression; the stresses in the opposite direction have a reversed pattern. The M/F primarily affects the stress in root. Three stress invariants (1st principal/3rd principal/dilatational stress) in the tooth movement direction have moderate correlations with BMD loss. Conclusions The stress invariants may be used to characterize what the osteocytes sense when ME changes. Their distributions in the tissues are significantly different, meaning the cells experience different stimuli. The higher bone activities along the direction of tooth movement may be related to the initial volumetric increase and decrease in the alveolar bone.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanical environment change in root, periodontal ligament, and alveolar bone in response to two canine retraction treatment strategies

Jiang

Xia

et al. 2015

Orthod Craniofacial Res

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“…1 We are fully aware of the limitation of using Hounsfield units (HU) to predict bone mineral density (BMD) from cone-beam computed tomography (CBCT) images; this was the reason that we designed this longitudinal study and only reported the relative HUs or HU changes. We chose HUs because they are commonly associated with BMD.…”

mentioning

confidence: 99%

Use of Hounsfield units in cone-beam computed tomography

Vitral¹,

Fraga²,

Campos³

2015

American Journal of Orthodontics and Dentofacial Orthopedics

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Use of Hounsfield units in cone-beam computed tomography T he article "Hounsfield unit change in root and alveolar bone during canine retraction" 1 focused on HU changes in the alveolar bone and root surface as the canines were moved by 2 treatment strategiestranslation and controlled tipping-that were evaluated with cone-beam computed tomography (CBCT). The authors stated that although the use of HUs from CBCT images has not been considered a reliable way to quantify absolute bone mineral density, it is still the best method available to monitor changes of bone mineral density in terms of HUs through longitudinal studies as long as the same CBCT machine and the same scan settings are used.Although the absolute values were not described in this study, the alterations found for root and bone mineral densities do not correspond to the variations of HUs and, therefore, should not be referred to as such.The gray values obtained with CBCT show a linear relationship with the attenuation coefficients of the materials, and the HUs obtained with medical computed tomography and density values from dual energy x-ray absorptiometry. Errors are expected when CBCT images are used to define the quality of the scanned structures because these images show inconsistencies and arbitrariness in the gray values, particularly when related to abrupt changes in the density of the object, x-ray beam hardening effects, scattered radiation, projection data discontinuity-related effect, differences between CBCT devices, changes in the volume of the field of view (FOV), and changes in the relationships of size and position between the FOV and the object evaluated. According to the studies available to date, CBCT should not be considered the examination of choice for the determination of mineral density of osseous and soft tissues, especially when the values obtained are compared with predetermined standard values. 2 In the methodology used in the study, the standardization of the equipment, the image-acquisition setting, the patient's head posture, and the FOV during image acquisition allowed the standardization of errors for image acquisition, minimizing the problems associated with the technique. However, the values obtained from the images were not from HUs, but of gray values. Our intention is not to criticize the methodology in the article, but to call attention to the appropriate nomenclature to be used. unit change in root and alveolar bone during canine retraction. Am J Orthod Dentofacial Orthop 2015;147:445-53. 2. Campos MJ, de Souza TS, Mota J unior SL, Fraga MR, Vitral RW. Bone mineral density in cone beam computed tomography: only a few shades of gray. World J Radiol 2014;6:607-12.Authors' response W e want to thank the authors of this letter to the editor for their comments regarding our article. 1 We are fully aware of the limitation of using Hounsfield units (HU) to predict bone mineral density (BMD) from cone-beam computed tomography (CBCT) images; this was the reason that we designed this longitudinal study and only reported...

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Limitation of a cross-sectional study

Solem¹

2015

American Journal of Orthodontics and Dentofacial Orthopedics

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Gray values and HUs are linearly related. We chose HUs because previous studies linked HUs to BMD, which was the physical parameter we were investigating. We used a custom-designed phantom with standard BMD rods to check whether the zeros of the HUs and BMD agreed. The zeros were very close; this was the basis for calculating the percentages of HU changes and using them to investigate BMD changes. Therefore, we used HUs instead of gray values in this study.

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Hounsfield unit change in root and alveolar bone during canine retraction

Cited by 9 publications

References 22 publications

Mechanical environment change in root, periodontal ligament, and alveolar bone in response to two canine retraction treatment strategies

Mechanical environment change in root, periodontal ligament, and alveolar bone in response to two canine retraction treatment strategies

Use of Hounsfield units in cone-beam computed tomography

Limitation of a cross-sectional study

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