儿童下颌骨骨密度的定量CT测量研究

目的 对71名10～16岁儿童的下颌骨骨密度进行定量CT(QCT)测量,探讨骨密度的变化情况.方法 对每名儿童的左侧下颌角、颏中部和右侧下颌角分别进行QCT扫描测量,并按照年龄和性别进行分析.结果 10～12岁儿童左侧下颌角、颏中部、右侧下颌角骨密度平均值分别为44.29、89.70、54.31 mg/dL;13～16岁儿童左侧下颌角、颏中部、右侧下颌角骨密度平均值分别为63.85、122.47、70.23 mg/dL.结论 男性儿童10～12岁组与13～16岁组下颌骨骨密度值随年龄的增加而明显增高,但左右两侧下颌角及颏中部骨密度值有较大差异,男女之间骨密度值也有很大的差异.     

儿童下颌骨骨密度的定量CT测量研究

目的对71名10～16岁儿童的下颌骨骨密度进行定量CT（QCT）测量，探讨骨密度的变化情况。方法对每名儿童的左侧下颌角、颏中部和右侧下颌角分别进行QCT扫描测量，并按照年龄和性别进行分析。结果10～12岁儿童左侧下颌角、颏中部、右侧下颌角骨密度平均值分别为44.29、89.70、54.31 mg/dL；13～16岁儿童左侧下颌角、颏中部、右侧下颌角骨密度平均值分别为63.85、122.47、70.23 mg/dL。结论男性儿童10～12岁组与13～16岁组下颌骨骨密度值随年龄的增加而明显增高，但左右两侧下颌角及颏中部骨密度值有较大差异，男女之间骨密度值也有很大的差异。     

Bone density in human dentate and edentulous mandibles using computed tomography

Mandibular bone density, vertebral density and resorption of the edentulous ridge were correlated in a group of 17 partially edentulous subjects. Bone density was quantified by Quantitative Computerized Tomography; resorption was evaluated on panoramic radiographs. Mean bone density in dentate areas was significantly higher than that in edentulous areas; mandibular bone density was not found to relate significantly to vertebral bone density, nor to ridge resorption. In programming osseointegrated implants in the partially edentulous mandible, CT may give a more accurate evaluation of trabecular bone. However, further studies are necessary to clarify its clinical utility.     

Quantitative computed tomography bone mineral density measurements in irradiated and non-irradiated minipig alveolar bone: an experimental study

Objective: The objective of this study was to analyse the effect of irradiation on bone mineral density (BMD). Materials and methods: All maxillary and mandibular pre‐molars and molars of six minipigs were extracted. After a 3‐month healing period, the maxilla and mandibles of three minipigs received three irradiation exposures at a total dose of 24 Gy. At 3 months after irradiation, quantitative computed tomography (QCT) was performed. As a reference, a calibration bone phantom with pre‐determined BMD was attached to the head of the minipigs. The QCT data were imported into a software program to calculate the BMD of the alveolar bone and the calibration bone phantom. In order to compare BMD values of individual minipigs, the so‐called bone mineral density quotient (BMDQ) was created, dividing the BMD value of the alveolar bone by the BMD value of the calibration bone phantom. Results: Mean BMDQ values appeared to be higher in irradiated than in non‐irradiated minipigs. However, the difference was not significant. In both irradiated and non‐irradiated minipigs, the average mandibular BMDQ values were statistically significantly higher than the average maxillary BMDQ values (P=0.003). The P‐values of the Student t‐test, determining the irradiation effect, were 0.11 for maxillary, 0.14 for mandibular, and 0.07 for overall peri‐implant BMDQ. P‐values of the non‐parametric Mann–Whitney test were all 0.05. Conclusion: It could be concluded that, 3 months after irradiation, the BMD of irradiated alveolar minipig bone was increased, when compared with non‐irradiated alveolar minipig bone. However, the increase was not statistically significant.     

Study of mandible bone mineral density of Chinese adults by dual-energy X-ray absorptiometry

The objective of this study was to measure the bone mineral density (BMD) of mandible and study the correlation between the BMD of the mandible and the lumbar vertebrae. 224 healthy volunteers were recruited in China and divided into 6 age groups: 20-29, 30-39, 40-49, 50-59, 60-69, and over 70 years. Dual-energy X-ray absorptiometry (DXA) was used to measure the BMD of the lumbar vertebrae and the mandible of each volunteer. The BMD of mandibular chin, mandibular angle and the lumbar vertebrae (L1-L4) was 1.3013 ± 0.2576 g/cm², 1.0484 ± 0.1087 g/cm² and 1.1195 ± 0.1373 g/cm², respectively. The BMD of mandibular angle and lumbar vertebrae decreased significantly beyond the age of 50 years. There was a significant difference between males and females in the BMD of the mandibular angle and lumbar vertebrae in the 50-59, 60-69 and over 70 year age groups. The authors found that the BMD of mandibular angles correlates with that of lumbar vertebrae. This study suggests that measurement of mandible BMD could be used to predict osteoporosis.     

牙周炎患者拔牙创骨密度变化的测量分析

目的 探讨因牙周炎拔牙后牙槽骨骨密度的变化。方法 采用双能X线吸收法测量不同原因拔牙后牙槽骨骨密度有腰椎椎体骨密度。结果 牙周炎组牙槽骨骨密度变化值低于非牙周炎组；牙周炎患者腰椎椎体骨密度与非牙周炎患者腰椎椎体骨密度无显著性差异。结论 牙周炎患者拔牙后牙槽骨整合速度低于非牙周炎者的愈合速度，这是由于局部炎症的持续作用造成的，全身骨密度状况并不是影响牙周炎的主要因素。     

Prospective study to estimate mandibular cancellous bone density using large‐volume cone‐beam computed tomography

Objective: Because pixel or voxel values obtained from cone‐beam computed tomography (CBCT) images are not absolute values, the bone density cannot be evaluated. Hence, the regression line between voxel values of CBCT and the bone mineral density (BMDs) of multislice CT (MSCT) was prospectively evaluated to investigate the mandibular cancellous bone density. Also, the usefulness of a reference bone block was evaluated on assessing a low mandibular bone density. Materials and methods: A total of 15 (two males and 13 females) patients who had undergone postoperative imaging for mandibular dental implant treatment with a bone graft using CBCT and MSCT were enrolled in this investigation. Voxel values of region of interests in CBCT were transformed to BMDs using a regression line from a previous study, and differences between BMDs obtained using CBCT and MSCT were calculated. Also, the voxel values of CBCT at the selected sites, in which the bone density was measured between 100 and 300 mg/cm³ of hydroxyapatite (HA) in MSCT, were assessed regarding whether they were higher or lower than the BMD of the reference bone block. Results: The mean overall difference was 38 mg/cm³ of HA. Thirty‐eight of the 45 sites (84%) were accurately assessed using the reference bone block. Conclusion: The usefulness of a regression line for BMD estimation in CBCT was prospectively confirmed in mandibular cancellous bone. Also, the reference bone block was useful to assess the low bone density of mandibular cancellous bone on CBCT with a large volume. To cite this article:
Naitoh M, Hirukawa A, Katsumata A, Ariji E. Prospective study to estimate mandibular cancellous bone density using large‐volume cone‐beam computed tomography.
Clin. Oral Impl. Res. xx , 2010; 1309–1313.
doi: 10.1111/j.1600‐0501.2010.01950.x     

Relationship between bone mineral density and 2D and 3D structural parameters of bone trabeculae

Objectives We analyzed the two- (2D) and three-dimensional (3D) structure of trabecular bone using bone mineral density (BMD) values as the standard. Correlations between the 2D and 3D structural parameters and BMD in the same samples of trabecular bone were determined to assess the reliability of 2D radiological morphometric analysis of bone as a method for evaluating BMD. Methods The first phalanxes of racehorses were used. A region of interest (ROI) was specified on computed radiography images of the phalanx. The 2D structural parameters for the ROI were determined by morphometric analysis. Then, a block of trabecular bone corresponding to the ROI was excised from the phalanx, and the 3D structural parameters of this bone sample were determined using microfocus X-ray computed tomography. The BMD of each bone sample was measured using peripheral quantitative computed tomography. Results Most, but not all, of the 3D parameters were correlated with BMD (r = 0.82–0.98), and several 2D parameters (skeletal perimeter, skeletal number, skeletal separation, skeletal spacing, fractal dimension, and skeletal pattern factor) were relatively closely correlated with BMD (r = 0.57–0.65). Conclusions These results suggest that the 2D morphometric analysis of bone is a useful, noninvasive method for assessing bone strength.     

Trabecular bone mineral density of mandible and alveolar height in postmenopausal women

Mineral density of the trabecular bone of the mandible was determined by single-energy QCT (quantitative computed tomography) for 74 totally or nearly edentulous menopausal women. These results were compared with the bone mineral densities (BMD) of their lumbar area (L2–L4) and femoral collum, measured by dual-energy x-ray transmission, Lunar DPX. The remaining height of the residual ridge at the symphysis of the mandible was measured on computed tomography (CT) lateral projection view, and an index of the residual ridge status was introduced. To determine whether general osteoporosis status affects the remaining height of the residual ridges, we compared these values with all results for bone mineral density. The BMD of the lumbar area and that of the femoral collum correlated well with each other, but the BMD of the trabecular bone of the mandible did not correlate with either of the other two BMD measurements. Measurements of residual ridge height did not correlate with any BMD values. The effect of possible bone loss earlier in life is no longer apparent in mandibular height or trabecular BMD over 20 yr after tooth extractions.     

Cortical bone mineral density in the mandible and osteoporosis status in postmenopausal women

Mineral density of the cortical bone of the mandible was determined by single-energy QCT (quantitative computed tomography) for 77 menopausal women. Bone mineral densities (BMD) were measured in the buccal and lingual layers of the cortex, distally from the foramen mentale, on both sides of the mandible. All the women were edentulous in that region, and the alveolar processes were far resorbed. These results were compared with the BMD values of the femoral neck, lumbar spine, and trabecular portion of the mandible between the detected layers of cortex. The BMD of the buccal cortex correlated remarkably well with all values, except those of the trabecular portion. Of the women tested, the correlations were lowest in the least osteoporotic group. The values for the lingual cortex did not correlate with other variables as well as did those for the buccal cortex, but in the most osteoporotic part of the sample the lingual cortex values correlated significantly with the BMD of the trabecular portion. The BMD values for the buccal cortex were significantly higher than those for the lingual cortex.     

Evaluation of voxel values in mandibular cancellous bone: relationship between cone-beam computed tomography and multislice helical computed tomography

Objective: Measurements of bone density in designed sites are important in presurgical imaging for dental implant treatment. However, the pixel or voxel values obtained from cone-beam computed tomography (CT) images are not absolute values. Hence, the relationship between voxel values obtained from cone-beam CT with a limited-volume exposure field and a flat panel detector and bone mineral densities (BMDs) obtained from multislice CT was evaluated in the mandible.
Material and methods: A total of 16 (four males and 12 females) patients who had undergone imaging for mandibular dental implant treatment using cone-beam CT with Alphard VEGA and multislice CT were enrolled in this investigation.
Cross-sectional images of cone-beam and multislice CT were reconstructed, and values of regions of interest (ROIs) in images were calculated.
Results: A high-level correlation between voxel values of cone-beam CT and BMDs of multislice CT was observed ( r =0.965).
Conclusion: It was suggested that voxel values of mandibular cancellous bone in cone-beam CT could be used to estimate bone density.     

Correlation of insertion torques with bone mineral density from dental quantitative CT in the mandible

Abstract: Objective: The aim of this study was to establish a correlation between bone mineral density measured preoperatively with dental computed tomography (CT), and insertion torque of screw‐shaped dental implants. Material and methods: In eight human mandibles obtained postmortem, bone mineral density (BMD) was measured with dental quantitative CT (DQCT) and correlated with insertion torque values at 45 implant sites during insertion of screw‐shaped dental implants (Brånemark System MKIII, Nobel Biocare, AB, Göteborg, Sweden). Results: A significant correlation (r=0.86, P<0.001) between BMD and torque values was observed, indicating that local BMD at a specific implant position is related to the supportive capacity of the jawbone. BMD exhibited no correlation with bone height or position. Conclusion: The noninvasive assessment of BMD using a DQCT scan employing a low‐dose protocol may be used to estimate expected primary stability depending on BMD, implant type and preparation procedure. These data may therefore help the surgeon to select the optimum implant position, implant type and operation technique.     

Bone mineral density: Methods of measurement and its influence on primary stability of miniscrews

Objective:To verify whether bone mineral density (BMD) of cortical bone, trabecular bone, and total bone influence the primary stability of orthodontic miniscrews and to verify whether there is a correlation between the measurement of BMD by cone-beam computed tomography (CBCT) and central dual-energy x-ray absorptiometry (DEXA).Materials and Methods:Twenty bovine bone sections were extracted from the pubic and iliac bones from regions with cortical thicknesses of approximately 1 mm. The BMD of the total bone block was evaluated using two methods: CBCT and DEXA. The BMD of cortical, trabecular, and total bone in the region of interest (ROI) were also evaluated by CBCT. After scanning the bone blocks, 20 self-drilling miniscrews (INP®) 1.4 mm in diameter and 6 mm long were inserted into them. The peak implant insertion torque (IT) was registered. After this, the pull-out test (PS) was performed and the maximum force registered. The Pearson correlation test was applied to verify the correlations between variables.Results:The BMD of the total bone block verified by CBCT and DEXA showed a positive and strong correlation (r  =  0.866, P  =  .000). The BMD of the ROI for cortical bone influenced the IT (r  =  0.518, P  =  .40) and the PS of miniscrews (r  =  0.713, P  =  .001, Table 2). However, the total bone BMD (verified by CBCT and DEXA) and trabecular bone BMD presented weak and not statistically significant correlations with primary stability.Conclusions:There was a positive correlation between total bone block BMD measured by DEXA and CBCT. The cortical BMD influenced the IT and PS.     

Reliability of voxel values from cone‐beam computed tomography for dental use in evaluating bone mineral density

Objectives: The aim of this study was to investigate whether it was possible to evaluate bone mineral density (BMD) using voxel values from cone‐beam CT (CBCT) for dental use. Materials and methods: A water phantom with an aluminum rod and sample tubes containing iodine solutions of various concentration was imaged by CBCT and multi‐slice CT (MSCT). Voxel values and CT numbers, respectively, of the samples were measured and their correlation was investigated. In addition, based on the CT numbers of a hydroxyapatite (HA) reference phantom, a conversion formula from voxel value to BMD was obtained. Results: There was a positive correlation between the voxel values of CBCT and the iodine concentration of the solutions, regardless of the X‐ray dose or the mean energy, although the voxel values had a slight tendency to be saturated at higher iodine concentrations. An excellent correlation between the voxel values and CT numbers was also observed. A regression analysis showed that nonlinear (linear‐quadratic model) regression was more appropriate than linear regression fitting for plotting these two values, although the latter might be usable for clinical applications. The conversion formula from the voxel value of CBCT to the equivalent BMD was as follows: y=?0.03669x²+3.602x?350.3 (x: voxel value, y: BMD mg/cm³ HA). Conclusions: This study revealed that there was a high correlation between the voxel values of CBCT and the CT numbers of MSCT. Although this was an in vitro study with assumed ideal conditions for measuring voxel values, there was a clear possibility for estimating CT numbers and BMD using the voxel values from the CBCT images, but the relationship was not entirely linear and should be examined further. To cite this article:
Nomura Y, Watanabe H, Honda E, Kurabayashi T. Reliability of voxel values from cone‐beam computed tomography for dental use in evaluating bone mineral density.
Clin Oral Impl Res. 21 , 2010; 558–562.
doi: 10.1111/j.1600‐0501.2009.01896.x     

稳定性牙合板治疗颞下颌关节紊乱病患者后髁突骨密度变化的CBCT研究

目的 利用CBCT测量颞下颌关节紊乱病(TMD)患者稳定性牙合板治疗前后髁突骨密度变化,分析稳定性牙合板对髁突改建的影响.方法 纳入40例稳定性牙合板治疗的TMD患者,治疗前后拍摄CBCT.运用MIMICS 21.0软件中Density功能测量髁突皮质骨密度,对髁突前斜面、顶部、后斜面骨密度进行统计学分析.结果 治疗前...     

放疗后狗下颌种植体周围骨密度变化初探

目的：了解放疗后,狗下颌种植体周围骨密度的变化情况。材料和方法：8只成年雄性杂种狗,体重20～22kg,拔除双侧下颌第3、4前磨牙和第1磨牙,3个月后,给予左侧下颌无牙区,单一剂量15Gy的放射线照射,隔3个月后将狗分成两组,一组在纯钛种植体植入前后,接受高压氧治疗;一组不接受高压氧治疗。种植术后1个半月和3个月,分别以麻醉过量致死方式取材,用双能X-线骨密度仪,测量放疗后狗下颌种植体周围骨密度的变化情况。结果：同一只狗放疗侧骨密度低于非放疗侧;放疗后6个月狗左右侧骨密度差别,大于放疗后4个半月;高压氧治疗组这种差别则不明显。结论：放疗干扰了狗下颌骨的正常新陈代谢,降低了骨密度,而高压氧的辅助治疗,可减轻这种影响。     

A preliminary study of the use of peripheral quantitative computed tomography for investigating root canal anatomy

Aim  To evaluate the use of peripheral quantitative computed tomography (pQCT) for qualitative and quantitative analysis of root canal anatomy and for assessing the extent of canal enlargement during root canal instrumentation.
Summary  The volume variation achieved by S1 ProTaper instruments in the coronal third of the root canals was analysed using peripheral computed tomography. The tooth was scanned in the horizontal plane producing 36 consecutive cross-sectional images. All images were the result of 360 projections with a section thickness of 250 μm, a distance between slices of 0.5 mm and an in-plane pixel size of 70 × 70 μm. The evaluation was completed before and after S1 ProTaper instrumentation (with or without circumferential filing) of one root canal of a freshly extracted maxillary first premolar tooth. The acquired images were realigned geometrically and processed using a 3D visualization software. pQCT scanning allowed 3D reconstruction of the root canal anatomy and the assessment of the extent of canal enlargement during root canal instrumentation with lateral displacement of canal walls and hence volume change being greater than the coefficient of variation. The densitometry evaluation showed uniform density along the root canal wall.
Key learning points • pQCT scanning allowed 3D reconstruction of the root canal anatomy and the assessment of the extent of canal enlargement during root canal instrumentation.
• pQCT shows promise for allowing qualitative and quantitative analysis of endodontic procedures.     

Bone classification: an objective scale of bone density using the computerized tomography scan

Dental implants are subject to masticatory loads of varying magnitude. Implant performance is closely related to load transmission at the bone-to-implant interface where bone quality will be highly variable. The type and architecture of bone is known to influence its load bearing capacity and it has been demonstrated that poorer quality bone is associated with higher failure rates. To date, bone classifications have only provided rough subjective methods for pre-operative assessment, which can prove unreliable. The results of an extensive analysis of computerized tomography scans using Simplant software (Columbia Scientific Inc., Columbia, MD, USA) demonstrate that an objective scale of bone density based on the Houndsfield scale, can be established and that there is a strong correlation between bone density value and subjective quality score (P = 0.002) as well as between the bone density score and the region of the mouth (P < 0.001).     

一氟磷酸谷酰胺及αD3对去势大鼠下颌骨骨密度的影响

目的探讨一氟磷酸谷酰胺及αD3对去势大鼠下颌骨骨密度的影响。方法将3月龄SD雌性大鼠39只随机分成4组：假手术组（SHAM组），去卵巢不处理组（OVX组），去卵巢单用一氟磷酸谷酰胺组（MFP组），去卵巢一氟磷酸谷酰胺与αD3联合用药组（MFP+αD3组）。在大鼠去势后6周，MFP组将一氟磷酸谷酰胺溶于蒸馏水后灌胃，MFP+αD3组将一氟磷酸谷酰胺和αD3溶于蒸馏水后灌胃。每天1次，每周6次，连续12周。采用HPIAS10000型图像分析系统进行下颌骨组织形态测量，采用双能X线测量股骨和下颌骨的骨密度。结果OVX组与SHAM组、MFP组、MFP+αD3组相比，下颌骨骨小梁面积、骨小梁宽度和松质骨面积明显减少，骨小梁间隔增大，股骨骨密度减小，而SHAM组、MFP组、MFP+αD3组三者之间无明显差异；OVX组、MFP+αD3组的下颌骨骨密度较SHAM组升高, 差异有显著性, 而MFP组与SHAM组间无显著性差异。结论一氟磷酸谷酰胺及αD3能促进去势大鼠下颌骨骨量的增加，下颌骨骨密度的改变与四肢骨不一致。