Trabecular structural changes in the mandibular condyle caused by degenerative osteoarthritis: a comparative study by cone-beam computed tomography imaging

Oral Radiology - Temporomandibular osteoarthritis causes pain and loss of function. In advanced cases, it may also result in destruction of joint cartilage surfaces and bone structure. This study...     

Assessment of simulated mandibular condyle bone lesions by cone beam computed tomography

There are many limitations to image acquisition, using conventional radiography, of the temporomandibular joint (TMJ) region. The Computed Tomography (CT) scan is a better option, due to its higher accuracy, for purposes of diagnosis, surgical planning and treatment of bone injuries. The aim of the present study was to analyze two protocols of cone beam computed tomography for the evaluation of simulated mandibular condyle bone lesions. Spherical lesions were simulated in 30 dry mandibular condyles, using dentist drills and drill bits sizes 1, 3 and 6. Each of the mandibular condyles was submitted to cone beam computed tomography (CBCT) using two protocols: 1) axial, coronal and sagittal multiplanar reconstruction (MPR); and 2) sagittal plus coronal slices throughout the longitudinal axis of the mandibular condyles. For these protocols, 2 observers analyzed the CBCT images independently, regarding the presence or not of injuries. Only one of the observers, however, performed on 2 different occasions. The results were compared to the gold standard, evaluating the percentage of agreement, degree of accuracy of CBCT protocols and observers' examination. The z test was used for the statistical analysis. The results showed there were no statistically significant differences between the 2 protocols. There was greater difficulty in the assessment of small-size simulated lesions (drill # 1). From the results of this study, it can be concluded that CBCT is an accurate tool for analyzing mandibular condyle bone lesions, with the MPR protocol showing slightly better results than the sagittal plus coronal slices throughout the longitudinal axis.     

Branching of mandibular canal on cone beam computed tomography images

BackgroundMandibular neurovascular canal contents may be vulnerable to damage during mandibular surgical procedures. Greater knowledge of the location and configuration of the mandibular canal can help in the safe performance of these procedures in the dental clinic. Cross-sectional CBCT imaging is a good modality for studying the course, location, configuration and accessory branches of the mandibular canal. The aim of this study was to observe the branching of the mandibular canal at different segments of the mandible and mandibular tooth groups.MethodsCBCT images of 116 mandibular halves were included in this study. The presence of secondary branching of the mandibular canal in the ramus, retromolar area, molar and premolar teeth as well as the length, diameter and angle of these branches were observed.Resultssixty nine mandibular halves (59.5%), had a main canal with no branching, There were 36 IAC (31%) with one, 8 (6.9%) with two, 2 (1.7%) with three and 1(0.9%) with 5 accessory branches. Of these secondary branches, 16 (25.4%) were in the ramus, 16(25.4%) in the retromolar, and 31(49.2%) in the molar regions.ConclusionAdvanced cross-sectional imaging modalities especially CBCT is a suitable tool for observing anatomic characteristics of mandibular canal to preserve this vital structure in surgical procedures.     

下颌管分支的锥形束CT影像学分析

目的 运用锥形束CT（CBCT）分析下颌管分支发生的概率及其类型。方法 选取拍摄CBCT影像的216例（女104 例,男112例）患者为研究对象,对CBCT的下颌管分支影像进行观测并进行分类。结果 216例（432侧）患者中,39例（18.06%）50侧（11.57%）观测到下颌管分支,其中女18例（17.31%）,男21例（18.75%）。下颌管分支分为4类,第Ⅰ类17侧（3.94%）,第Ⅱ类11侧（2.55%）,第Ⅲ类20侧（4.63%）,第Ⅳ类2侧（0.46%）。结论 CBCT对下颌管分支的检出率较高,口腔颌面外科医生在进行下颌手术时应注意下颌管分支这一解剖变异。     

Evaluation of two-dimensional lateral cephalogram and three-dimensional cone beam computed tomography superimpositions: a comparative study

Superimposition of radiographic imaging is used to evaluate patient growth and the effects of surgical and/or orthodontic treatment. The purpose of this study was to compare the outcomes of superimposition between two-dimensional (2D) and three-dimensional (3D) superimpositions. 2D lateral cephalograms were generated from the initial and final cone beam computed tomography scans (CBCT) of 18 patients and superimposed. Both 3D CBCT and 2D CBCT generated lateral cephalograms were oriented to the Frankfort horizontal plane and superimposed according to the American Board of Orthodontics recommendations. Changes in landmark position were quantified from the resulting superimposition outcomes via linear measurements made with Dolphin software. Differences between the two methods were analyzed using paired t-tests. Measurements were repeated twice for 10 randomly selected scans to assess reliability by intra-class correlation coefficient (ICC) analysis. Intra-examiner reliability was high for all measurements (ICC > 0.84). Agreement between 2D and 3D superimposition outcomes, as measured by P-values, was low for ANS (P = 0.026), B-point (P < 0.001), ST Upper lip (P = 0.019), U1 tip (P = 0.010), and U1 apex (P = 0.026). 2D measurements were significantly higher than 3D measurements for ANS, B-point, ST Upper lip, U1 tip, and U1 apex. Findings indicated that both methods of superimposition (2D and 3D) are highly reliable. Statistical differences between 2D and 3D superimposition outcomes were below the threshold of clinical significance.     

Volumetric changes of the upper airway following maxillary and mandibular advancement using cone beam computed tomography

The objective of this project was to retrospectively evaluate changes in volume of different compartments of the upper airway in response to maxillary, mandibular, and bimaxillary advancement surgeries and to predict the extent of volumetric changes associated with these surgical movements. Pre- and post-surgical cone beam computed tomography scans of 36 patients were evaluated for changes in nasal cavity, nasopharyngeal, oropharyngeal, and hypopharyngeal compartments. The amount of movement for each surgery was measured from skeletal landmarks to reference planes and was correlated with volumetric changes. Maxillary advancement of 4.0 ± 2.2 mm increased the oropharyngeal volume significantly (41.40%), and mandibular advancement of 3.8 ± 1.6 mm also significantly increased the oropharyngeal volume (21.17%). Bimaxillary advancement of 5.1 ± 1.3 mm for the maxilla and 6.4 ± 3.1 mm for the mandible significantly increased nasopharyngeal (27.45%), oropharyngeal (66.39%), and hypopharyngeal (52.48%) volumes. Furthermore, for every millimeter anterior movement, oropharyngeal volume increased by 2319.2 ± 771.8 mm³. Bimaxillary advancement showed a greater increase than isolated maxillary and mandibular advancement in all pharyngeal compartments. Every millimeter of advancement in the bimaxillary group led to a significant increase in oropharyngeal volume, while every millimeter downward movement showed a significant increase in nasopharyngeal volume.     

锥形束CT与曲面断层在诊断下颌骨骨折中的比较研究

目的对比研究锥形束CT与曲面断层对下颌骨骨折的诊断特点及差异。方法收集2010年4月至2010年10月共27例因颌面部外伤行锥形束CT和曲面断层检查的患者的临床资料,比较两种方法对下颌骨不同部位骨折的诊断率。结果锥形束CT在下颌骨各部位的骨折诊断中均能明确观察骨折线及断端移位情况,而曲面断层存在漏诊现象,漏诊率为27.5%（11/40）,特别是髁突及颏部骨折,漏诊率分别为35.3%和27.3%。结论曲面断层检查存在漏诊的可能,特别是髁突或颏部骨折时,漏诊率更高。建议对下颌骨骨折应结合锥形束CT检查,以避免漏诊。同时,锥形束CT三维重建在帮助医生制定手术计划方面有很大优势和广泛应用前景。     

Bone quality assessment based on cone beam computed tomography imaging

Objectives: The aim of this in vitro study was to investigate the accuracy of fractal analysis and morphometry for bone quality assessment as measured with dual energy X-ray absorptiometry (DXA).
Material and methods: Nineteen mandibular bone samples were used for the creation of artificial bone lesions ( n =5) or decalcification ( n =12) to simulate osteoporosis; two samples were used as controls. Cone beam computed tomography (CBCT) and DXA scans were made before and after processing the samples. The image data obtained from the CBCT scans were used to calculate the mean fractal dimension (FD), bone area and density (morphometric analysis) of the samples. Bone mineral density (BMD) was obtained from the DXA scans and set as a reference value for bone quality. The correlation between BMD and FD and between BMD and morphometric results were calculated.
Results: A significant correlation between FD and BMD (ρ=+0.71 to +0.75; P <0.05) was observed. Bone area and BMD of the specimens (ρ=+0.69 to +0.85; P <0.05) were also significantly related, in contrast to the density analysis, for which no significant correlation to BMD was found.
Conclusions: The results of this study suggest that fractal analysis and bone area measurement have potential to evaluate bone quality on CBCT images, while density measurement does not seem to be valid.     

Application of cone beam computed tomography in facial imaging science

Facial imaging is used to study the facial shapeand its developmental changes over time.This isimportant to diagnose acquired malformations,to studynormal and abnormal growth and to differentiatebetween the results of treatment and normal growth,and to validate facial recognition.The two mainmethods to study and record facial imaging are bymeans of cephalometry and anthropometry[1].Cephalometrics is the scientific study of themeasurements of the head’s     

Assessment of variations of the mandibular canal through cone beam computed tomography

The neurovascular bundle may be vulnerable during surgical procedures involving the mandible, especially when anatomical variations are present. Increased demand of implant surgeries, wider availability of three-dimensional exams, and lack of clear definitions in the literature indicate that features of anatomical variations should be revisited. The objective of the study was to evaluate features of anatomical variations related to mandibular canal (MC), such as bifid canals, anterior loop of mental nerve, and corticalization of MC. Additionally, bone trabeculation at the submandibular gland fossa region (SGF) was assessed and related to visibility of MC. Cone beam computed tomography exams from 100 patients (200 hemimandibles) were analyzed and the following parameters were registered: diameter and corticalization of MC; trabeculation in SGF region; presence of bifid MC, position of bifurcations, diameter, and direction of bifid canals; and measurement of anterior loops by two methods. Corticalization of the MC was observed in 59% of hemimandibles. In 23%, MC could be identified despite absence of corticalization. Diameter of MC was between 2.1 and 4 mm for nearly three quarters of the sample. In 80% of the sample trabeculation at the SGF was either decreased or not visible, and such cases showed correlation with absence of MC corticalization. Bifid MC affected 19% of the patients, mostly associated with additional mental foramina. Clinically significant anterior loop (>2 mm of anterior extension) was observed in 22–28%, depending on the method. Our findings, together with previously reported limitations of conventional exams, draw attention to the unpredictability related to anatomical variations in neurovascularization, showing the contribution of individual assessment through different views of three-dimensional imaging prior to surgical procedures in the mandible.     

Cross-sectional analysis of the mandibular lingual concavity using cone beam computed tomography

Objectives: To study the prevalence and the degree of lingual concavity in the edentulous first molar region from cone beam computed tomography (CBCT) scans of the mandibles. Material and methods: Qualified cross‐sectional images in mandibular first molar edentulous region taken from CBCT were selected. The mandible morphology 2 mm above the inferior alveolar canal (IAC) was classified into the convex (C), parallel (P) and undercut (U) type, based on the presence of lingual concavity and the shape of alveolar ridge. The prevalence of each group was determined. Subsequently, the lingual concavity characters, including the depth, the angulation and the vertical location were determined by the measurements of selected anatomic landmarks. Results: One hundred and three subjects (mean age 51 with a range of 23.7–70.4 years) were studied. The U type was the most prevalent, accounting for 66% of the study population. The mean undercut depth and angulation at the level 2 mm above IAC were on average 2.4 mm and 57.7°. The mean vertical distances from the most prominent point (P) of the lingual concavity to the cemento‐enamel junction of second premolar and the inferior border of the mandible were 11.7 and 14.9 mm, respectively. Conclusions: The anatomic location and the degree of the lingual concavity presented in this article add more information in implant treatment planning in the mandibular first molar edentulous region. To cite this article:
Chan H‐L, Brooks SL, Fu J‐H, Yeh C‐Y, Rudek I, Wang H‐L. Cross‐sectional analysis of the mandibular lingual concavity using cone beam computed tomography.
Clin. Oral Impl. Res. 22 , 2011; 201–206.
doi: 10.1111/j.1600‐0501.2010.02018.x     

Postoperative changes after bilateral mandibular osteotomies: a computed tomography study

Twelve patients undergoing bilateral osteotomy of the ramus of the mandible were examined with CT preoperatively and postoperatively. The maximum area of the cheek and oropharynx was measured together with the thickness of the masseter muscle and the overlying subcutaneous tissue. The preoperative CT examinations showed wide anatomic variations. The postoperative examinations showed a diminished oropharynx lumen of approximately 43%. Swelling of the cheek averaged 61% and was associated with the well-vascularized masseter muscle. The TMJs were measured and a slight widening of the joint space was found postoperatively.     

Morphometric analysis of the mandibular fossa in dentate and edentulous patients: A cone beam computed tomography study

Statement of problemMandibular fossa roof thickness and lateral inclination could be associated with the presence of bone changes in the mandibular condyle in dentate and edentulous patients. However, literature regarding the relationship between the presence and absence of teeth and the morphologic features of the temporomandibular joint is lacking. This knowledge could provide a better understanding of changes affecting the correct functioning of the stomatognathic system.PurposeThe purpose of this clinical study was to assess the mandibular fossa roof thickness and lateral inclination in relation to sex, presence or absence of teeth, and bone changes in the mandibular condyle through cone beam computed tomography (CBCT).Material and methodsCBCT scans of 100 individuals (50 dentate and 50 edentulous) were evaluated in terms of mandibular fossa roof thickness and lateral inclination. Bone changes in the mandibular condyle were classified dichotomously in relation to osteophytes, erosion, sclerosis, and flattening. Differences were assessed with the Student t test, the chi-square test, and 2-way analysis of variance (ANOVA), with Tukey post hoc tests (α=.05).ResultsSex was not related to mandibular fossa measurements. Edentulous participants showed a higher mandibular fossa lateral inclination (P<.001) and lower roof thickness (P=.001) than dentate participants. When the association between bone changes in the mandibular condyle was evaluated in dentate and edentulous groups, only sclerosis showed a statistically significant association (P<.001). The 2-way ANOVA showed that the mandibular fossa roof thickness was lower in edentulous participants in the presence of flattening and erosion and that the mandibular fossa lateral inclination was higher in the presence of osteophytes, erosion, and sclerosis (P<.001). Among dentate participants, the mandibular fossa lateral inclination was higher in the presence of flattening (P=.024).ConclusionsMandibular fossa roof thickness and lateral inclination are not associated with sex. However, tooth absence and bone changes in the mandibular condyle are related to mandibular fossa measurements.     

The mandibular incisive canal and its anatomical relationships: A cone beam computed tomography study

Background

To avoid postoperative injuries in the interforaminal region, presence of the Mandibular Incisive Canal (MIC), its extension and canal positioning in relation to the cortical bone and alveolar process were investigated by cone beam computed tomography (CBCT).

Material and Methods

One hundred CBCT examinations obtained by means of the i-CAT CBCT imaging system were analyzed in multiple-plane views (axial, panoramic and cross-sectional) and three-dimensional representations were performed using iCAT CBCT software. The MIC was evaluated for its presence, measurement and proximity to the buccal and lingual plates, alveolar process and inferior border of the mandible.

Results

The MIC was visible in all (100%) CBCT images. The mean length of MIC was 9.8 ± 3.8 mm. The distances between the canal and buccal plate, as well as between the canal and lingual plate of the alveolar bone were 4.62 ± 1.41 mm and 6.25 ± 2.03 mm, respectively. The distances from the canal to the alveolar process, and to the inferior border of the mandible were 10.25 ± 2.27 mm and 7.06 ± 2.95 mm, respectively.

Conclusions

Due to the high prevalence of MIC, its variation in length and distance up to the cortical bone, suggested that preoperative radiographic evaluation of the MIC must be carried out case-by-case using CBCT, which could clearly show the three-dimensional structure and adjacent structure of the MIC. Key words:Diagnosis, anatomy, cross-sectional, tomography.     

健康青年人髁突松质骨结构锥形束CT分析

目的探讨锥形束CT测量下颌骨髁突松质骨结构的可行性，了解下颌骨髁突松质骨结构的分布特点。方法用锥形束CT对40名健康青年志愿者（20～32岁）的80侧下颌骨，获取髁突冠状位正中层面图像，用自行设计的图像分析软件对图像进行二值化处理，并分8区对松质骨结构参数进行分析，包括单位体积内的松质骨体积即骨小梁体积分数、测量范围内骨小梁的平均厚度即骨小梁厚度、单位毫米长度内骨小梁数目及骨小梁间的平均空间距离即小梁分离度。结果髁突上区与中、下区的所有松质骨结构参数值均不同，差异有统计学意义（P〈0．05）；髁突上区骨小梁体积分数最高（52．2％），骨小梁数目最多（1．33mm^-1），骨小梁厚度（393．48μm）和骨小梁分离度（361．59μm）最小；两侧髁突松质骨的结构参数值差异无统计学意义（P〉0．05）。结论下颌骨髁突内部的松质骨结构分布不均，但两侧的分布对称；用锥形束CT结合图像分析技术可以实现髁突松质骨结构的体内定量分析。     

Fundamentals of cone beam computed tomography for a prosthodontist

Cone beam computed tomography (CBCT, also referred to as C-arm computed tomography [CT], cone beam volume CT, or flat panel CT) is a medical imaging technique of X-ray CT where the X-rays are divergent, forming a cone.[1] CBCT systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimeter resolution in images of high diagnostic quality, with short scanning times (10–70 s) and radiation dosages reportedly up to 15–100 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a three-dimensional representation of the maxillofacial skeleton with minimal distortion. The aim of this article is to sensitize the Prosthodontist to CBCT technology, provide an overview of currently available maxillofacial CBCT systems and review the specific application of various CBCT display modes to clinical Prosthodontic practice. A MEDLINE search for relevant articles in this specific area of interest was conducted. The selected articles were critically reviewed and the data acquired were systematically compiled.Key Words: Artefact reduction, cone beam computed tomography, dose reduction, fundamentals, imaging accuracy, prosthodontics     

离体下颌前磨牙牙根和根管形态的锥形束CT研究

利用锥形束CT对190个离体下颌前磨牙进行扫描并选择不同方向的断层观察,按Vertucci’s分类法对根管系统进行记录。锥形束CT可以清晰显示其牙根和根管系统形态:下颌第一前磨牙根管系统变异较大,双根管率为22.8%。根管形态分别为Ⅰ型77.14%,Ⅱ型6.67%,Ⅳ型2.86%,Ⅴ型13.33%;下颌第一前磨牙的根面沟发生率较高(47/105),且此类型的下颌第一前磨牙常有双根管;下颌第二前磨牙的根管均为Ⅰ型单根管。