Paul F. van der Stelt

Accuracy of three-dimensional measurements obtained from cone beam computed tomography surface-rendered images for cephalometric analysis: influence of patient scanning position.

The aims of this study were to assess the accuracy of linear measurements on three-dimensional (3D) surface-rendered images generated from cone beam computed tomography (CBCT) in comparison with two-dimensional (2D) slices and 2D lateral and postero-anterior (PA) cephalometric projections, and to investigate the influence of patient head position in the scanner on measurement accuracy. Eight dry human skulls were scanned twice using NewTom 3G CBCT in an ideal and a rotated position and the resulting datasets were used to create 3D surface-rendered images, 2D tomographic slices, and 2D lateral and PA projections. Ten linear distances were defined for cephalometric measurements. The physical and radiographic measurements were repeated twice by three independent observers and were compared using repeated measures analysis of variance (P=0.05). The radiographic measurements were also compared between the ideal and the rotated scan positions. The radiographic measurements of the 3D images were closer to the physical measurements than the 2D slices and 2D projection images. No statistically significant difference was found between the ideal and the rotated scan measurements for the 3D images and the 2D tomographic slices. A statistically significant difference (P<0.001) was observed between the ideal and rotated scan positions for the 2D projection images. The findings indicate that measurements based on 3D CBCT surface images are accurate and that small variations in the patients head position do not influence measurement accuracy.

Accelerated vertebral bone loss in relation to the menopause: a cross-sectional study on lumbar bone density in 286 women of 46 to 55 years of age

Bone mineral density (BMD) of the lumbar spine was measured in 286 women (46-55 years of age) using dual photon absorptiometry. The women were classified in three categories: premenopausal, perimenopausal and postmenopausal. The postmenopausal group was subdivided according to the number of years since the last uterine bleeding. With multiple linear regression analysis of lumbar BMD on age and menopausal status, an acceleration of bone loss was observed during the perimenopausal period and the following first two postmenopausal years. No significant bone loss was detected in relation to age or during the later postmenopausal years. Applying both an additive and a multiplicative model of bone loss, the mean perimenopausal bone loss was 0.061 gram-equivalents hydroxyapatite (geqHA)/cm2 and 6.4%, respectively. In the first 2 postmenopausal years the mean bone loss was 0.044 geqHA/cm2 and 5.1% per year. These results suggest a substantial menopause related acceleration of lumbar bone loss in a relatively short time span with its onset in the perimenopausal period.

Comparison of Five Cone Beam Computed Tomography Systems for the Detection of Vertical Root Fractures

INTRODUCTION This study compared the accuracy of cone beam computed tomography (CBCT) scans made by five different systems in detecting vertical root fractures (VRFs). It also assessed the influence of the presence of root canal filling (RCF), CBCT slice orientation selection, and the type of tooth (premolar/molar) on detection accuracy. METHODS Eighty endodontically prepared teeth were divided into four groups and placed in dry mandibles. The teeth in groups Fr-F and Fr-NF were artificially fractured; those in groups control-F and control-NF were not. Groups Fr-F and control-F were root filled. CBCT scans were made using five different commercial CBCT systems. Two observers evaluated images in axial, coronal, and sagittal reconstruction planes. RESULTS There was a significant difference in detection accuracy among the five systems (p = 0.00001). The presence of RCF did not influence sensitivity (p = 0.16), but it reduced specificity (p = 0.003). Axial slices were significantly more accurate than sagittal and coronal slices (p = 0.0001) in detecting VRF in all systems. Significantly more VRFs were detected among molars than premolars (p = 0.0001). CONCLUSIONS RCF presence reduced specificity in all systems (p = 0.003) but did not influence accuracy (p = 0.79) except in one system (p = 0.012). Axial slices were the most accurate in detecting VRFs (p = 0.0001).

Tooth loss and osteoporosis: the OSTEODENT Study

AIM To determine the cross-sectional association of the osteoporotic status of patients with the number of their teeth, with and without taking into account age and/or smoking. MATERIAL & METHODS At four centres, the study recruited 665 females aged 45-70 years and the number of teeth was counted for 651 subjects. Bone density was measured at the total hip, femoral neck and lumbar spine. RESULTS The mean number of teeth in the osteoporotic subjects was 3.3 fewer than normal subjects and 2.1 fewer if those with no teeth were excluded. The association between osteoporosis and having <6 or having <28 teeth remained significant after adjusting for age, smoking and centre with p-values of 0.016 and 0.011, respectively. A single regression model for tooth count with normal errors would not fit all the data. By fitting mixture regression models to subjects with tooth count >0, three clusters were identified corresponding to different degrees of tooth loss. The overall effect of osteoporosis was as follows: -1.8 teeth before and after adjusting for smoking, -1.2 teeth after adjusting for age, and -1.1 teeth after adjusting for both age and smoking. CONCLUSIONS We have established a significant association between osteoporosis and tooth loss after adjusting the effect for age and smoking.

Influence of scanning and reconstruction parameters on quality of three-dimensional surface models of the dental arches from cone beam computed tomography

The study aim is to investigate the influence of scan field, mouth opening, voxel size, and segmentation threshold selections on the quality of the three-dimensional (3D) surface models of the dental arches from cone beam computed tomography (CBCT). 3D models of 25 patients scanned with one image intensifier CBCT system (NewTom 3G, QR SLR, Verona, Italy) using three field sizes in open- and closed-mouth positions were created at different voxel size resolutions. Two observers assessed the quality of the models independently on a five-point scale using specified criteria. The results indicate that large-field selection reduced the visibility of the teeth and the interproximal space. Also, large voxel size reduced the visibility of the occlusal surfaces and bone in the anterior region in both maxilla and mandible. Segmentation threshold was more variable in the maxilla than in the mandible. Closed-mouth scan complicated separating the jaws and reduced teeth surfaces visibility. The preliminary results from this image-intensifier system indicate that the use of medium or small scan fields in an open-mouth position with a small voxel is recommended to optimize quality of the 3D surface model reconstructions of the dental arches from CBCT. More research is needed to validate the results with other flat-panel detector-based CBCT systems.

Perimenopausal bone mass and risk factors

We studied the effect of menopausal status and risk factors on lumbar bone mineral density (BMD) and metacarpal cortical thickness (MCT) in 286 women of 46-55 years of age. Body mass index (height/weight) was measured and the family history of osteoporosis, reproductive history, menopausal status, calcium intake, amount of physical activity and the consumption of tobacco and alcohol were assessed. Lumbar BMD and MCT decreased substantially in the perimenopausal and postmenopausal period. In the premenopausal women a significant (P = 0.03) lower lumbar BMD was observed in the lowest tertile of calcium intake (less than or equal to 900 mg/day) compared to the highest tertile (greater than or equal to 1200 mg/day). This difference was not apparent in the peri- and postmenopausal women. This suggests that dietary calcium intake is more important in the development and/or maintenance of peak bone mass, than in the modulation of postmenopausal bone loss. Apart from menopausal status and low calcium intake, no other significant determinant of bone mass could be identified. We conclude, therefore, that the assessment of risk factor status is not an efficient tool for the identification of perimenopausal women with low bone mass.

Evaluation of the visibility and the course of the mandibular incisive canal and the lingual foramen using cone‐beam computed tomography

OBJECTIVES To assess the visibility and the course of the incisive canal and the visibility and the location of the lingual foramen using cone-beam computed tomography (CBCT). METHODS In total, 100 CBCT examinations of patients for preoperative planning were used for this study. The examinations were taken using the NewTom 3G CBCT unit, applying a standardized exposure protocol. Image reconstruction from the raw data was performed using the NewTom software. Three experts were asked to assess the visibility of the incisive canal using a four-point rating scale. The position of the incisive canal was recorded in relation to the lower, buccal and lingual border of the mandible using the application provided by the CBCT software. RESULTS The incisive canal was definitely visible in 83.5% of the scans and the mean endpoint was approximately 15 mm anterior to the mental foramen. The mean distance from the lower border of the mandible was 11.5 mm and its course was closer to the buccal border of the mandible in 87% of the scans. The lingual foramen was definitely visible in 81% of the scans. CONCLUSIONS The high detection rate of the incisive canal and the lingual foramen in the anterior region of the mandible using CBCT indicates the potential high preoperative value of CBCT scan for surgical procedures in the anterior mandible.

Dose reduction of two digital sensor systems measuring file lengths

OBJECTIVE The aim of this study was to determine the effect of dose reduction on the image quality of two sensor systems with automatic greyscale adjustment. STUDY DESIGN Two digital sensor systems, Sidexis (Siemens, Bensheim, Germany) and Digora (Soredex, Helsinki, Finland), were tested. The image quality of the systems was determined by comparing lengths of endodontic files (025, 020, 015, and 010 files) and a premolar root in the digital images with lengths on conventional radiographic films. For the experiments the exposure was changed to 100%, 50%, 25%, 12.5%, 6.25%, and 3.125% of that for Ektaspeed films. RESULTS The lengths of 025 and 020 files and the premolar root in the digital images were comparable with the lengths on films even if the exposure was reduced to 6% of that used for Ektaspeed films. The lengths of 015 files reduced as the exposure was reduced. The lengths of 010 files were significantly shorter than the lengths on films. CONCLUSIONS With the systems tested, a dose reduction of approximately 95% compared with Ektaspeed films is possible to determine the lengths of a premolar root and 025 and 020 files. For thinner objects a dose reduction is questionable.

Bone quality evaluation at dental implant site using multislice CT, micro-CT, and cone beam CT

OBJECTIVES The first purpose of this study was to analyze the correlation between bone volume fraction (BV/TV) and calibrated radiographic bone density Hounsfield units (HU) in human jaws, derived from micro-CT and multislice computed tomography (MSCT), respectively. The second aim was to assess the accuracy of cone beam computed tomography (CBCT) in evaluating trabecular bone density and microstructure using MSCT and micro-CT, respectively, as reference gold standards. MATERIAL AND METHODS Twenty partially edentulous human mandibular cadavers were scanned by three types of CT modalities: MSCT (Philips, Best, the Netherlands), CBCT (3D Accuitomo 170, J Morita, Kyoto, Japan), and micro-CT (SkyScan 1173, Kontich, Belgium). Image analysis was performed using Amira (v4.1, Visage Imaging Inc., Carlsbad, CA, USA), 3Diagnosis (v5.3.1, 3diemme, Cantu, Italy), Geomagic (studio(®) 2012, Morrisville, NC, USA), and CTAn (v1.11, SkyScan). MSCT, CBCT, and micro-CT scans of each mandible were matched to select the exact region of interest (ROI). MSCT HU, micro-CT BV/TV, and CBCT gray value and bone volume fraction of each ROI were derived. Statistical analysis was performed to assess the correlations between corresponding measurement parameters. RESULTS Strong correlations were observed between CBCT and MSCT density (r = 0.89) and between CBCT and micro-CT BV/TV measurements (r = 0.82). Excellent correlation was observed between MSCT HU and micro-CT BV/TV (r = 0.91). However, significant differences were found between all comparisons pairs (P < 0.001) except for mean measurement between CBCT BV/TV and micro-CT BV/TV (P = 0.147). CONCLUSIONS An excellent correlation exists between bone volume fraction and bone density as assessed on micro-CT and MSCT, respectively. This suggests that bone density measurements could be used to estimate bone microstructural parameters. A strong correlation also was found between CBCT gray values and BV/TV and their gold standards, suggesting the potential of this modality in bone quality assessment at implant site.

The use of visual assessment of dental radiographs for identifying women at risk of having osteoporosis: the OSTEODENT project

OBJECTIVE The objective of this study was to investigate the diagnostic accuracy of visual assessment of the trabecular pattern in intraoral periapical radiographs to identify female subjects at risk of having osteoporosis. STUDY DESIGN Six hundred female subjects underwent intraoral periapical radiography of the maxillary and mandibular premolar region. Five observers assessed the trabecular pattern as dense, heterogeneous, or sparse, with the aid of reference images. All patients received a central dual energy x-ray absorptiometry (DXA) examination of the hip and lumbar spine. RESULTS With sparse trabecular pattern as indicative of osteoporosis, mean specificity was high (91.6 for the upper jaw and 90.8 for the lower jaw) while the sensitivity was low (28.2 for the upper and lower jaw). The mean intraobserver agreement was comparable for radiographs of the upper and lower jaw (median kappa(w) 0.53 and 0.57, respectively). CONCLUSION Visual assessment of the trabecular pattern in intraoral periapical radiographs of premolar regions is a potential method to identify women at risk of having osteoporosis.