Effect of mandibular positioning on preimplant site measurement of the mandible in reformatted CT

The purpose of this study was to evaluate the effect of mandibular positioning on measurement of the reformatted cross-sectional image of the mandible in computed tomography (CT) according to the area on the mandible. Five dried mandibles, partially edentulous in the premolar and molar areas, were selected. The inferior border of the mandible was placed at 0-, 5-, 10-, 15-, and 20-degree angles to the CT scanning plane, and CTs were taken. The marked area of the reformatted cross-sectional image taken at each angle was found, and the distance from the most superior border of the mandibular canal to the alveolar crest was measured. As the angle between the CT scanning plane and mandibular plane increased, the distance from the most superior border of the mandibular canal to the alveolar crest also increased. The degree of increase was more pronounced in the posterior portion of the mandible than in the anterior portion of the mandible. As mandibular positional change in the CT gantry can affect the vertical measurement of the reformatted cross-sectional image, a correct guiding plane is necessary to accurately position the jaw to the CT scanning plane.     

The use of computed tomography to define zygomatic complex position.

PURPOSE: The purpose of this study was to analyze the use of midline references and landmarks to assess the position of the zygomatic complex relative to the cranial base, and to test the reliability of these measurements in assessing facial symmetry. METHODS: Direct skull measurements were compared with measurements made on computed tomography (CT) images. The effect of CT scanner error, technologist error, gantry angle error, error of skull inclination, and error due to the presence of titanium rigid fixation hardware were assessed. To test observer variation and the effect of each level of error, 4 blinded bilateral measurements were repeated 3 times by 5 observers on both dry skull and CT scans. A mixed effect analysis of variance model then assessed for effect of method of measurement (dry skull vs CT), observer, CT scanner, technologist, gantry angle, skull inclination, and rigid fixation. RESULTS: A total of 2,040 measurements were made. Measurements for zygomatic complex posterior and anterior width and height were reliable and had an interobserver variations of 0.02 +/- 0.03 mm, 0.5 +/- 0.4 mm, and 0.37 +/- 0.3 mm, respectively. The difference between dry skull and CT assessment for the 3 reliable measurements was 1.2 +/- 0.3 mm, 0.44 +/- 0.4 mm, and 1.1 +/- 0.5 mm, respectively. The errors produced by the CT scanner, technologist, and rigid internal fixation hardware were not clinically significant. The measurements were not sensitive to gantry angle and skull inclination changes of 10 degrees or less. A fourth measurement assessing zygomatic complex projection was found not to be accurate or reliable. CONCLUSIONS: These findings suggest that the 3 CT scan measurements describing the position of the zygomatic complex relative to the cranial base are clinically useful.     

Digital volume tomography in the diagnosis of periodontal defects: an in vitro study on native pig and human mandibles

BACKGROUND: The aim of this study of native pig and human mandibles was to investigate the accuracy and quality of the representation of periodontal defects by intraoral radiography (IR), panoramic radiography (PR), computed tomography (CT), and digital volume tomography (DVT) in comparison with histologic specimens. METHODS: Following the standardized preparation of periodontal defects (14 dehiscences, fenestrations, 2- to 3-walled intrabony defects, respectively; Class I, II, and III furcation involvement) in six pig and seven human mandibles, IR, PR, CT, and DVT were performed. The histologic specimens were produced by cutting blocks with the individual defects out of the mandibles, embedding them in acrylic, and producing sagittal and axial microsections. The intrabony defects were measured using appropriate software on the digitized IR and PR images programs. The histologic sections were measured by reflecting stereomicroscopy. The statistical comparison between the measurements of the radiographic images and those of the histologic specimens was performed with Pearson's correlation coefficient. The quality of the radiographic images was determined through the subjective perception and detectability of the intrabony defects by five independent observers. RESULTS: All intrabony defects could be measured in three planes in the CT and DVT scans. Comparison with the histologic specimens yielded a mean deviation of 0.16 +/- 0.10 mm for the CT scans and 0.19 +/- 0.11 mm for the DVT scans. On the IR and PR images, the defects could be detected only in the mesio-distal and craniocaudal planes. In comparison with the histologic specimens, the IR images revealed a mean deviation of 0.33 +/- 0.18 mm and the PR images a mean deviation of 1.07 +/- 0.62 mm. The quality rating of the radiographic images was highest for the DVT scans. CONCLUSIONS: Overall, the CT and DVT scans displayed only a slight deviation in the extent of the periodontal defects in comparison with the histologic specimens. Both radiographic imaging techniques permitted imaging of anatomic osseous structures in three planes, true to scale, and without overlay or distortion. The DVT scans showed the best imaging quality.     

A positioning device for computed tomography: a clinical report

This clinical report describes a device (Centrascan) used to assist in the correct alignment of the patient's head during computed tomography (CT) assessment of a proposed implant site. To obtain the desired anatomic detail, CT requires precise alignment of the axial images at right angles to the long axis of the proposed implant. This clinical report compared the anatomic morphology of a projected implant site derived from axial images provided by DentaScan software analysis of the CT scan acquisition. Images from a conventional scan, with the patient's head aligned along the frontal plane (perpendicular to the Frankfort plane) and along the sagittal plane (coinciding with either the cortical bone of the hard palate or the inferior border of the mandible), were compared with images acquired by use of the Centrascan device. The two scans differed substantially. In particular, the cross-sectional images obtained by the conventional procedure showed a distorted anatomy; conversely, the images obtained by the Centrascan procedure showed a better reproduction of the examined area. The Centrascan device seemed to help the radiologist achieve a more correct alignment of the patient's head during CT scan acquisition. Further studies are necessary to fully explore the relative technical merits of the Centrascan device.     

快速原型技术辅助复杂下颌骨重建术后颞下颌关节功能的评价

目的：研究快速原型技术对复杂下颌骨缺损重建术后患者髁突位置和颞下颌关节功能的影响。方法：对下颌骨良性肿瘤切除同时需保留髁突的复杂缺损重建术患者50例,其中20例用快速原型技术指导下颌骨重建（快速原型组）,30例用传统方法进行下颌骨重建（对照组）。所有患者手术前、后均行下颌骨及颞下颌关节三维螺旋CT扫描,测量髁突的三维空间位置,并用Fricton颞下颌关节功能量表进行术后颞下颌关节功能检查,计算颞下颌关节功能障碍指数（DI）、肌压痛指数（PI）及颞下颌关节紊乱指数（CMI）。采用SPSS11.5软件包,用配对t检验分析组内手术前、后差异,Mann-Whitney非参数检验分析组间差异。结果：所有肿瘤术后无复发,移植骨成活,关系良好。快速原型组外形对称,下颌运动功能正常,髁突位置正常。对照组6例面型不对称,8例CT显示患侧髁突有较明显的移位。快速原型组手术前、后的髁突前距离,内距离,上、下距离及长轴夹角数值无统计学差异。对照组手术前、后前距离有统计学差异（P〈0.05）,上、下距离及长轴夹角有显著性统计学差异（P〈0.01）,内距离无统计学差异（P〉0.05）。快速原型组及对照组组间术前髁突位置无统计学差异（P〉0.05）,而术后前距离及上、下距离有统计学差异（P〈0.05）,长轴夹角有显著性统计学差异（P〈0.01）,内距离无统计学差异（P〉0.05）。快速原型组及对照组间术后颞下颌关节各项功能指数中,DI及CMI差异有统计学意义（P〈0.05）,PI差异无统计学意义（P〉0.05）。结论：快速原型技术能通过保持髁突三维空间位置,改善术后颞下颌关节功能,提高下颌骨重建效果。     

Linear measurement accuracy of CBCT panoramic reconstructions: experimental study with dry human mandibles

Introduction

Studies on software accuracy of reformatted panoramic computed tomography (CT) images are scarce.

Objectives

The aim of this study was to evaluate the software accuracy of reformatted panoramic views from cone-beam computed tomography (CBCT).

Methods

Ten dry mandibles were scanned using CBCT with different voxel sizes. Following the reconstruction of panoramic views with three different software, horizontal and vertical linear measurements were performed using the electronic rules of each software. Measurements of the corresponding dry mandibles were taken with a digital caliper and defined as the gold standard.

Results

There were no statistically significant differences in linear distances among the dry mandibles and reformatted panoramic CT views. The relative error ranged from 1.3 to 8.0%, depending on the software and voxel size.

Conclusions

The linear measurements on reformatted panoramic views are reliable.

     

Three-dimensional analysis of condylar hyperplasia with computed tomography

Three-dimensional surface reconstruction imaging from CT scans was used to study the deformity of the mandible in six patients with mandibular asymmetry. High-resolution axial CT scans of the mandible were obtained using Somatom-DR3 (Siemens). COSMOZONE-2SA (Nikon) with PC-9801VX21 (NEC) was used to reconstruct the three-dimensional images. The six patients were divided into two groups. One group was classified as unilateral hybrid forms and the other group was classified hemimandibular elongation on the diagnostic criteria of Obwegeser and Makek (1986). In the three-dimensional surface reconstruction, exact location and the degree of the deformity in the region from the ascending ramus to the condylar head and the lingual aspect from the ascending ramus to the mandibular body were accurately represented. In addition, the three-dimensional images could be easily rotated arbitrarily, precise evaluation could be done at every part of the mandible. On diagnosis, the mandibular morphology classified into the unilateral hybrid forms was presumed to vary from case to case even in the same classification.     

Influence of maxillomandibular positioning in cone beam computed tomography for implant planning

The aim of this study was to evaluate the influence of changes in maxillomandibular positioning during cone beam computed tomography (CBCT) imaging on the planning of dental implants. Ten skulls were marked bilaterally with metal spheres in four regions: incisors, canine, premolars, and molars. CBCT scans were obtained in seven positions: standard position (SP), displacements of 10° and 20° above and below the SP, and lateral displacements of 10° and 20° from the SP. Subsequently, bilateral measurements of the height and width of the maxilla and mandible were performed on all images. The results showed that the position with a displacement of 20° above the SP presented the greatest differences in the measurements of bone height and width. In the bilateral comparisons, the maxillary bone width showed the greatest differences, especially for the regions of the premolars and molars. It is concluded that alterations of positioning during the acquisition of CBCT images can lead to alterations in the measurements of bone height and width, which may result in errors in implant planning and cause damage to anatomical structures.     

Presurgical evaluation for dental implants using a reformatting program of computed tomography: maxilla/mandible shape pattern analysis (MSPA)

A new analysis technique that provides a shape pattern of the maxilla or mandible is described. This technique uses a software program of computed tomography multiplanar reformation (CT/MPR). The successive cross-sectional images obtained by the CT/MPR are numbered, and the height and width of the maxilla and mandible at each of these cross-sectional images at specified levels are measured. The measured height and width are plotted against the number of the cross-section. This technique, termed maxilla/mandible shape pattern analysis (MSPA), creates an easy profile of the shape of the maxilla and mandible, and it enhances treatment planning for the placement of dental implants.     

Condylar and mandibular morphological criteria in the 2D and 3D MSCT imaging for patients with Class II division 1 subdivision malocclusion

The condyle has a special multidirectional capacity for the growth and adaptive remodeling of temporomandibular joint (TMJ). Being part of TMJ structure, it plays an important role in the stability of long-term treatment results for orthodontic and orthognatic patients with Class II division 1 subdivision malocclusions. Several computed tomography (CT) investigation modes have been used to evaluate the craniofacial morphology and particularly, for TMJ. Dimensional images, acquired using new generation multislice CT (MSCT) and cone beam CT scanning data, are becoming increasingly popular in the clinical work and research. The aim of the study was to develop a new CT investigation protocol for the quantification of morphological structures and skeletal landmarks of condyle, procesus condylaris and mandible. For this purpose we created two dimensional (2D) and three dimensional (3D) reconstruction images from primary axial MSCT scans using IAC review and Transparent bone programms and acquired accordant measurements of condylar and mandibular structures. This technic allowed to get truly volumetric reflexion of the joint components in its real anatomical size and avoided the bony superimpositions. Our material included 12 patients with skeletal Class II division 1 subdivision malocclusion who had indications for combined orthodontic and orthognatic treatment. CT examination was performed before the start of treatment. For statistical analysis paired Student t-tests were applied to test the diferences of mean values and correlation coefficients were calculated to assess possible interrelations between measurements. The preliminary results showed weak corrrelation between condylar and mandibular measurements. More significant correlation was observed between procesus condylaris and mandible. It was a significant difference between right and left side in the height of procesus condylaris in patients without clinicaly relevant facial asymetry which could be considered in the individual planning of orthognatic treatment. CONCLUSION: The developed combined 2D and 3D MSCT investigation protocol for condylar and mandibular measurements provides precise and demonstrative quantitative images of condylar and mandibular structures and its dimensional relationships., which could be qualified as informative criteria for the individual treatment planning for patients with Class II division 1 subdivision malocclusion.     

Digital volume tomography in the diagnosis of peri-implant defects: an in vitro study on native pig mandibles

BACKGROUND: The aim of this study of native pig mandibles was to investigate the accuracy and quality of the representation of peri-implant defects by intraoral radiography (IR), panoramic radiography (PR), computer tomography (CT), and digital volume tomography (DVT). METHODS: The examination was carried out on 19 native pig mandibles. In the toothless sections of the mandibles, one or two implants were inserted. Following the standardized preparation of peri-implant defects (11 each of dehiscences, fenestrations, and 2- to 3-walled intrabony defects), IR, PR, CT, and DVT were performed. The peri-implant defects were measured using appropriate software on the digitized IR and PR image programs. As a control method, the peri-implant bone defects were measured directly using a reflecting stereomicroscope with measuring ocular. The statistical comparison between the measurements of the radiographic scans and those of the direct readings of the peri-implant defects was performed with Pearson's correlation coefficient. The quality of the radiographic scans was determined through the subjective perception and detectability of the peri-implant defects by five independent observers. RESULTS: In the DVT and CT scans, it was possible to measure all the bone defects in three planes. Comparison with the direct peri-implant defect measurements yielded a mean deviation of 0.17+/-0.11 mm for the DVT scans and 0.18+/-0.12 mm for the CT scans. On the IR and PR images, the defects could be detected only in the mesio-distal and cranio-caudal planes. In comparison with the direct measurements of the peri-implant defects, the IR images revealed a mean deviation of 0.34+/-0.30 mm, and the PR images revealed a mean deviation of 0.41+/-0.35 mm. The quality rating of the radiographic images was highest for the DVT scans. CONCLUSIONS: Overall, the CT and DVT scans displayed only a slight deviation in the extent of the peri-implant defects. Both radiographic imaging techniques permitted imaging of peri-implant defects in three planes, true to scale, and without overlay or distortion. The DVT scans showed the best imaging quality.     

改良数字化导板技术在下颌骨缺损腓骨肌皮瓣修复中的应用评价

目的: 探讨改良数字化导板技术在下颌骨节段切除及腓骨肌皮瓣修复重建术中的临床应用效果。方法: 选择2016年1月—2020年1月在南京医科大学附属口腔医院及阜阳市人民医院口腔科行下颌骨节段性切除同期行血管化腓骨肌皮瓣修复的16例患者,均为良性病变,随机分为常规导板技术组（常规组）和改良数字化导板组（改良组）,每组各8例。常规组患者行术前常规检查,常规导板设计手术方案。改良组患者术前行下颌骨锥形束CT（CBCT）及双侧下肢CT血管造影（CTA）检查,数据导入数字化导板软件后模拟手术过程,打印预期重建的3D模型,制作术中准确定位的导板,以达到重建后腓骨骨段精确定位。2组患者术后2周复查CBCT,选取髁突位置及下颌骨形态变化为参考,对比分析患者手术前、后CT数据,比较2组患者髁突位置及下颌骨形态变化。根据临床表现,比较2组患者于术前、后开口度与开口型变化,以及下颌骨重建修复手术效果差异。采用患者满意度调查表,让患者在术后3个月左右、义齿修复治疗前,对余留牙咀嚼功能、语言功能及面部外形做出自主等级评价。采用SPSS 25.0软件包对数据进行t检验或秩和检验。结果: 2组患者手术均顺利完成。改良组患者髁突位置变化明显小于常规组。改良组患者下颌骨形态变化小于常规组。改良组患者术后开口度及开口型恢复更优,患者对咀嚼功能及面部外形满意度高于常规组,2组患者发音功能满意度无显著差异。结论: 改良数字化导板技术在血管化腓骨肌皮瓣精确修复下颌骨缺损的应用中有较高的临床指导价值,可简化手术过程,减少术后并发症,提升下颌骨的重建精度。     

Radiographic considerations for the regional anatomy in the posterior mandible

Background: Previous studies of the inferior alveolar nerve have used cadaveric specimens in small patient groups. The purpose of this study was to describe the anatomy in the posterior mandible with respect to the inferior alveolar nerve (IAN) using computed tomography (CT) images in a large patient population. We hypothesize that CT scans are an important component of a thorough treatment plan for minimizing risk to the IAN and optimizing surgical outcomes. Methods: CT scans of 195 patients (62 males and 133 females; age range: 22 to 88 years) were evaluated retrospectively. With the aid of computer software, cross‐sectional images were examined at 5‐mm increments distal to the mental foramen to the ascending ramus. Four measurements were made at each cross‐sectional image. The distances from the IAN to the: 1) alveolar crest (CN); 2) buccal cortical plate (BN); 3) lingual cortical plate (LN); and 4) inferior border (IN) were measured. Results: Most measurements for males and females were significantly different. Mean values were as follows (males/females): CN, 13.85 ± 0.43/11.98 ± 0.40 mm (P <0.01); BN, 4.98 ± 0.15/4.47 ± 0.11 mm (P <0.01); LN, 2.93 ± 0.12/3.19 ± 0.10 mm (P <0.10); and IN, 7.76 ± 0.16/7.00 ± 0.15 mm (P <0.01). The 95% confidence intervals indicated that many patients had limited bone volume in the buccal shelf or ascending ramus. Conclusion: Given the high degree of variability in mandibular bone volume surrounding the IAN and the position of the IAN, the use of CT scans should be considered for surgical procedures in the posterior mandible when there is risk of injury to the IAN.     

Pre-operative Assessment of Anatomical Position of Inferior Alveolar Nerve and Its Significance in Bilateral Sagittal Split Osteotomy

The aim of this study is to investigate the position and course of the mandibular canal through the ramus, angle and body of mandible using computed tomographic (CT) imaging pre-operatively and to relate these predetermined values intra-operatively to perform sagittal split ramus osteotomies. Pre-operative CT scans were taken and four points were marked at mandibular foramen, mandibular angle, mandibular body and midpoint and different dimensions of IAN were measured to localize the inferior alveolar nerve. With the obtained values, precise osteotomy cuts were made intra-operatively and intra-operative measurements for position of IAN were noted. Based on the preoperative CT measurements, the chance to encounter IAN bundle, during surgery was evaluated. The present study proved that pre-operative CT imaging prior to BSSO surgical procedure is an effective way to investigate the position and course of the IAN canal through the framework of the mandible and by interpolating these dimensions intra operatively, reduces the risk of direct injury to the IAN bundle.     

Imaging the neonatal mandible for accurate distraction osteogenesis

The position of mandibular teeth is difficult to document in the neonatal patient. Panorex images are difficult to obtain in an uncooperative pediatric patient. The new technique presented by the authors uses computed tomographic data to create a curved, reformatted image of the mandible, and generates an image similar to a panorex image. This curved, reformatted mandibular image provides accurate visualization of the mandible and mandibular teeth. This technique allows for precise pin placement and osteotomy in distraction osteogenesis.     

应用Mimics软件建立下颌无牙颌三维有限元模型

目的:快速准确建立患者下颌无牙颌三维有限元模型,为种植修复的生物力学分析打下基础.方法:CT扫描患者下颌骨,转换为DICOM数据后用Mimics软件重建三维图像,再用自编命令流导入Ansys软件进行分析处理.结果:快速准确地建立了活体下颌无牙颌三维有限元模型.结论:CT 技术,DICOM 标准的应用使有限元模型的建立更为精确,Mimics软件直接建立三维模型后直接导入Ansys软件极大的提高了建模效率.     

Diagnostic difficulties of complex root morphology: case study of a lower wisdom tooth

We did a panoramic radiographic examination of a symptomatic lower third molar for surgical planning and risk assessment. This showed a close association with the inferior dental canal, in addition to uncertain root morphology. A periapical radiograph showed evidence of additional smaller curved roots. Axial computed tomography (CT) with coronal reformats did not provide further information about the morphology of the root. After removal of the tooth, its root form was compared with the diagnostic images. The periapical radiograph provided the most information about the morphology of the additional roots. The axial and reformatted coronal CT showed accurately the position and tortuous course of the inferior dental canal.     

基于配准技术的微创牙种植导向模板的制作方法及应用

目的设计制作精确的微创牙种植导向模板,以指导医生准确地手术定位。方法对行种植手术的患者下颌骨进行CT扫描,依据CT数据构建三维牙颌模型,并利用Simplant专业种植软件在三维模型的基础上进行模拟种植,确定种植体的位置和深度。对牙颌石膏模型进行数字化扫描,通过曲率配准技术将石膏模型和CT三维模型进行对齐,确定种植体设计位置与牙颌扫描模型的关系,根据种植体位置,在牙颌石膏数字化模型上利用3-Matic软件完成导向模板的设计,最后利用快速成型技术制作导向模板。结果通过配准技术将CT数据与牙颌数字化数据相融合,设计出的微创导板定位精确,在无需切开口腔黏膜的情况下依然能够很好地为医生在实际种植时提供导向。结论将三维配准技术应用于种植领域,结合Simplant模拟种植和快速成型等技术制作的微创种植导向模板定位准确,实现了手术的微创性与精确性,值得临床推广使用。     

A rater agreement study on measurements in cross-sectional CBCT images exploring the association between alveolar bone morphology and craniofacial height

Objectives

To investigate rater agreement regarding measurements of height and width of the maxilla and mandible using cross-sectional images from CBCT examinations. Furthermore, to explore the association between vertical craniofacial height and alveolar bone morphology.

Methods

Pre-treatment CBCT scans from 450 patients referred for treatment to a private clinic for orthodontics and oral surgery in Scandinavia were available and of these, 180 were selected. Lateral head images were generated from the CBCT volumes to categorise subjects into three groups based on their craniofacial height. Cross-sectional images of the maxillary and mandibular bodies at three locations in the maxilla and mandible, respectively, were obtained and measured at one height and two width recordings by five raters. One-way analysis of variance with a Tukey post hoc test was performed. A significance level of 5% was used.

Results

Rater agreement was mostly excellent or good when measuring height and width of the maxilla and mandible in cross-sectional CBCT images. For height (of the alveolar bone/bodies), there were statistically significant differences between the low- and the high-angle groups for all the observers when measuring in the premolar and midline regions, both in the maxilla and in the mandible.

Conclusion

The high agreement found ensures a reliable measurement technique and confirms the relation between craniofacial height and alveolar bone height and width.

     

EVALUATION OF SIMULATED BONE LESION IN THE HEAD OF THE MANDIBLE BY USING MULTISLICE COMPUTED TOMOGRAPHY

Conventional radiography has shown limitation in acquiring image of the ATM region, thus, computed tomography (CT) scanning has been the best option to the present date for diagnosis, surgical planning and treatment of bone lesions, owing to its specific properties. Objective: The aim of the study was to evaluate images of simulated bone lesions at the head of the mandible by multislice CT. Material and methods: Spherical lesions were made with dental spherical drills (sizes 1, 3, and 6) and were evaluated by using multislice CT (64 rows), by two observers in two different occasions, deploying two protocols: axial, coronal, and sagittal images, and parasagittal images for pole visualization (anterior, lateral, posterior, medial and superior). Acquired images were then compared with those lesions in the dry mandible (gold standard) to evaluate the specificity and sensibility of both protocols. Statistical methods included: Kappa statistics, validity test and chi-square test. Results demonstrated the advantage of associating axial, coronal, and sagittal slices with parasagittal slices for lesion detection at the head of the mandible. Results: There was no statistically significant difference between the types of protocols regarding a particular localization of lesions at the poles. Conclusions: Protocols for the assessment of the head of the mandible were established to improve the visualization of alterations of each of the poles of the mandible''s head. The anterior and posterior poles were better visualized in lateral-medial planes while lateral, medial and superior poles were better visualized in the anterior-posterior plane.