Cone beam computed tomography evaluation of distance from cementoenamel junction to alveolar crest before and after nonextraction orthodontic treatment

Objective:To evaluate the distance between the cementoenamel junction and the alveolar bone crest before and after orthodontic treatment using cone beam computed tomography (CBCT).Materials and Methods:The sample comprised 30 patients with Angle Class I malocclusion and mild to moderate crowding. The study database comprised dental CBCT scans obtained before and after orthodontic treatment. The distance between the cementoenamel junction to the bone crest of the buccal (n  =  720) and lingual (n  =  720) surfaces was measured in 24 teeth for each patient using a specific software tool (Xoran version 3.1.62). The Wilcoxon test was used for statistical analysis, and the level of significance was set at P < .05.Results:The distance between the cementoenamel junction and the bone crest increased in 822 (57%) of the 1440 surfaces after orthodontic treatment. The buccal surface of the lower central incisors had the greatest frequency of increased distance (75%), and the lingual surface of lateral incisors had the lowest (40%). The distance between the cementoenamel junction and the alveolar bone crest was greater than 2 mm (alveolar bone dehiscence) in 162 (11%) of the 1440 surfaces before orthodontic treatment and in 279 (19%) after treatment.Conclusions:The distance from the cementoenamel junction to the bone crest changed after orthodontic treatment; the distance was greater than 2 mm in 11% of the surfaces before treatment and in 19% after treatment.     

非拔牙正畸治疗牙槽嵴高度变化的CBCT研究

［摘要］目的 采用CBCT评估非拔牙正畸治疗前后釉牙骨质界到牙槽嵴顶的高度变化情况。方法 选择安氏Ⅰ类错〖HT5”,7”〗牙〖KG-*3〗合〖HT5”〗畸形的患者30例,存在轻中度拥挤。正畸前后进行CBCT扫描影像。分别对每个患者的24颗牙齿从釉牙骨质界与颊侧(n=720)和舌侧(n=720)牙槽嵴顶之间的距离进行测量和对比分析。 结果 在1 440处测量中,正畸治疗前有130（9.0%）例,治疗后有199例（13.8%）釉牙骨质界到牙槽骨嵴顶的距离超过2 mm（牙槽骨开裂）。 结论 骨开裂在正畸治疗前的牙齿中占9.0%。正畸治疗后,釉牙骨质界与骨嵴顶的距离发生变化。     

Alveolar bone thickness and height changes following incisor retraction treatment with microimplants:: A cone beam computed tomography study

ObjectivesTo evaluate alveolar bone remodeling following incisor retraction treatment with microimplants and to examine the relationship between crown/root distal movement and thickness/height changes of the alveolus.Materials and MethodsA total of 24 patients (mean age, 19.29 ± 4.64 years) with bialveolar protrusion treated by incisor retraction with microimplants were included. The distances of the crown and root tip movements as well as the thickness (alveolar bone thickness [ABT]; labial, lingual, and total) and vertical level (vertical bone level [VBL]; labial and lingual) of the alveolar bone were assessed using cone-beam computed tomography images obtained before treatment (T1) and after treatment (T2). All T1 and T2 variables were compared, and further comparisons of alveolar bone changes were conducted between the two groups based on the distance of the crown (low-crown-movement and high-crown-movement groups) and root movements (low-root-movement and high-root-movement groups). To determine the correlation of the crown or root movement with the variables of alveolar bone changes, Pearson correlation coefficients were calculated.ResultsSignificant differences were found in all VBL and ABT variables after treatment in both jaws but not in total ABT. Based on the crown and root movements, alveolar bone change significantly differed between the root-movement groups, whereas there was no significant difference between the crown-movement groups. In addition, root movement showed significant correlations with the variables.ConclusionsRemarkable changes in the height and thickness of alveolar bone were found after microimplant-aided incisor retraction treatment in all groups except for total ABT. Root movement was significantly correlated with the alveolar bone changes.     

Cone beam computed tomography evaluations of marginal alveolar bone before and after orthodontic treatment combined with premolar extractions

Using cone beam computed tomography (CBCT) we investigated the distance between the cemento-enamel junction (CEJ) and the marginal bone crest (MBC) at buccal, lingual, mesial, and distal surfaces of incisors to first molars in adolescents before (baseline) and after extractive orthodontic treatment (study end point). Patients with Class I malocclusion, crowding and an overjet of ≤ 5 mm were examined with a CBCT unit using a 60 × 60-mm field of view and a 0.125-mm voxel size. Large differences in marginal bone height were found at baseline, particularly between tooth surfaces. There was a slight correlation between age and CEJ-MBC distance. From baseline to the study end point, large bone-height changes among teeth and tooth surfaces could be seen. Lingual surfaces, followed by buccal surfaces, showed the largest changes. Eighty-four per cent of lingual surfaces of mandibular central incisors exhibited a bone-height decrease of > 2 mm. The bone-height decrease was larger at lingual surfaces in the mandible than in the maxilla, and larger in girls (mean=1.8 mm) than in boys (mean=1.5 mm). Fewer than 1% of proximal surfaces exhibited changes of > 2 mm. It is unknown whether the changes in marginal bone height are transitory. A high-quality CBCT technique may help to determine this by providing a deeper insight into the long-term side effects of orthodontic treatment.     

锥形束CT测量牙槽骨高度准确性和可靠性研究

目的评价在锥形束CT（cone beam compnted tomography,CBCT）图像上测量牙槽骨高度的准确性和可靠性。方法8个人类湿颅标本经CBCT扫描后测量图像上牙尖点到釉牙骨质界距离（T-CEJ）、牙尖点到牙槽嵴顶距离（T-BM）、釉牙骨质界到牙槽嵴顶距离（CEJ—BM）。在标本上实际测量以上项目。将两种测量值进行配对f检验。选择一定数量的位点重复测量,计算组内相关系数（ICC）,进行一致性检验。结果CBCT测量值均略小于标本实际测量值。其中对T-CEJ的测量两种方法无统计学差异,差值均值为-0．041mm;对T-BM和CEJ-BM的测量两种方法有统计学差异,差值均值分别为-0．268mm和-0．208mm。所有重复测量的ICC均大于0．96。结论CBCT测量牙槽骨高度与标本测量虽然存在统计学差异,但差异较小,在临床实际可接受范围之内。CBCT测量的可靠性较好。     

改良唇挡扩弓后牙齿及牙槽骨变化的 CBCT 研究

目的：研究改良唇挡单侧扩弓后牙齿及牙槽骨的变化。方法：20例单侧完全性唇腭裂患者应用改良唇挡进行单侧扩弓,扩弓前后分别进行CBCT扫描重建,测量裂隙侧牙齿及牙槽骨的变化并进行统计学分析。结果：①未经扩弓治疗的单侧完全性唇腭裂隙患者裂侧尖牙和前磨牙相对于健侧均表现为舌倾,其中尖牙舌倾最明显;②牙及牙槽骨均发生颊倾;颊侧牙槽骨倾斜度大于腭侧,变化量与牙齿的颊倾程度呈正相关性;③根尖基骨宽度增加。结论：唇挡扩弓后牙槽骨随牙齿的颊倾发生适应性改建,同时唇挡刺激牵引牙根尖基骨的改建,在适应症范围内唇挡扩弓是安全有效的。     

慢性牙周炎基础治疗前后牙槽骨锥形束CT评价

目的 应用锥形束CT(CBCT)评价慢性牙周炎牙周基础治疗前后牙槽骨的改变.方法 选择重度慢性牙周炎患者30例,对牙周基础治疗前、后上颌前磨牙牙槽骨进行临床疗效观察及拍摄CBCT片,利用CBCT随机软件测量牙槽骨高度和相对骨密度变化.结果 重度慢性牙周炎基础治疗后,患者牙周袋探诊深度、附着丧失明显好转,较治疗前差异均有统计学意义(P＜0.05).牙槽骨密度升高差异有统计学意义(P＜0.05),牙槽骨吸收程度变化差异无统计学意义(P＞0.05).不同阅片者之间对牙槽骨密度及牙槽骨吸收状况的测量,一致性检测结果显示组内相关系数大于0.9,差异无统计学意义.结论 CBCT可用于重度慢性牙周炎牙周基础治疗前、后牙槽骨状态的评价,定点方法具有可行性和可重复性.     

牙周病患者正畸前后牙槽骨密度变化的CBCT研究

目的 牙周病正畸治疗中,在严格控制炎症和正畸力的情况下,牙齿松动度仍然增加,本研究旨在从牙槽骨骨密度变化方面对其机制进行初步探讨.方法 选择牙周病正畸治疗者20例,牙周健康正畸者为对照组21例,应用锥束CT（cone beam computed tomography,CBCT）,在正畸治疗的第一期排齐阶段前后拍摄,使用头影测量方法原理,在CBCT图像的选定截面定点,对上下颌前牙区牙槽间隔骨密度进行测量,同时记录相关的临床牙周指标,采用SPSSl6.0软件包分析,以配对t检验和独立样本t检验比较两组内和组间的牙槽骨密度的差异,Pearson相关分析评价骨密度与临床指标间的相关性.结果 治疗前牙周病组和对照组骨密度无明显差别（P＞0.05）,治疗后牙槽骨密度降低量为牙周病组（-18.94±30.81）显著大于对照组（-11.35±31.55）（P＜0.05）,牙周病组牙松动度有明显增加（P＜0.05）.结论 静止期牙周病牙槽骨在正畸力刺激下,牙槽骨密度明显降低.牙槽骨密度降低与牙齿松动度增加有显著相关,推测松动度增加可能由于骨密度降低引起,这方面值得进一步研究.     

The usefulness of cone-beam computed tomography gray values for alveolar bone linear measurements

Objectives:To test a proof-of-concept that the accuracy and reliability of alveolar bone height measurements from orthodontic grade (large field-of-view [FOV], large voxel-size) cone-beam computed tomography (CBCT) images may be improved by using pixel gray values.Materials and Methods:Twenty fresh cadaver pig heads underwent CBCT scans (17 × 23 cm FOV, 0.4-mm voxel size). Buccal alveolar bone heights of maxillary first molars were measured using the conventional vision-based (VB) and the proposed gray value–assisted (GVA) methods. The GVA methods entailed localization of landmarks through observation of gray value pattern changes across tissue boundaries followed by mathematical calculation of distances between landmark pixels. Interrater reliability and accuracy of CBCT measurements made by all methods were statistically analyzed by comparing with physical measurements (gold standards).Results:The interrater reliability of CBCT measurements made by GVA methods was comparable to physical measurements but higher than those made by the VB method. The GVA (bend-down pattern) method yielded average measurements similar to physical measurements, while those obtained by the VB and the GVA (straight pattern) methods were significantly larger (repeated measures analysis of variance, P < .001). The GVA (bend-down pattern) method also produced significantly more measurements within one voxel size of physical measurements than did the VB and GVA (straight pattern) methods (Chi-square tests, P < .017).Conclusions:These data confirm a concept that local gray value change patterns may be used to improve the accuracy and reliability of alveolar bone height measurement from large FOV and large voxel-size CBCT images.     

Changes of anterior maxillary alveolar bone thickness following incisor proclination and extrusion

Objective:To investigate changes in maxillary alveolar bone thickness after maxillary incisor proclination and extrusion during anterior crossbite correction in a group of growing patients with Class III malocclusion.Materials and Methods:Maxillary incisors of 15 growing patients with anterior crossbite were proclined and extruded with 0.016″ beta-titanium advancing loops and Class III elastics. Lateral cephalograms were recorded before advancement (T₀) and 4 months after a normal overjet and overbite were achieved (T₁). Changes in alveolar bone thickness surrounding the maxillary incisors at the crestal (S1), midroot (S2), and apical (S3) levels were measured using cone-beam computed tomography (CBCT). Paired t-tests were used to determine the significance of the changes. A Spearman rank correlation analysis was performed to explore the relationship between thickness changes and the rate and amount of incisor movements.Results:Although statistically significant decreases were observed in palatal and total bone thickness at the S2 and S3 level (P < .05), the amounts of these changes were clinically insignificant, ranging from 0.34 to 0.59 mm. Changes in labial bone thickness at all levels were not significant. Changes in palatal bone thickness at S3 were negatively correlated with changes in incisor inclination. (r  =  −0.71; P < .05).Conclusion:In a group of growing patients with Class III malocclusion undergoing anterior crossbite correction, controlled tipping mechanics accompanied by extrusive force may produce successful tooth movement with minimal iatrogenic detriment to the alveolar bone.     

利用锥体束CT对少年期中切牙根尖周牙槽骨厚度的研究

目的　研究少年期中切牙根尖唇舌侧牙槽骨厚度,并探讨与其相关的硬组织测量指标。方法　对42例符合纳入标准的错牙合畸形患者的锥体束CT（CBCT）进行评估,应用MIMICS 10.0软件测量168颗中切牙根尖唇舌侧牙槽骨厚度,并对42例患者进行CBCT三维和头颅侧位片二维头影测量,应用SPSS 21.0统计软件对中切牙根尖周牙槽骨厚度值与8项常用的硬组织头影测量指标进行Spearman 相关性分析。结果　少年期上中切牙根尖唇侧的牙槽骨厚度与上中切牙唇倾度呈正相关,与SNA角呈负相关,腭侧厚度的相关性与唇侧相反;下中切牙根尖唇、舌侧的牙槽骨厚度均与SN-MP角呈负相关,唇侧厚度与ANB角、下中切牙唇倾度呈正相关,腭侧厚度的相关性与唇侧相反。结论　头影测量中部分硬组织测量指标与少年期中切牙根尖周牙槽骨的厚度有相关性,对临床具有参考价值。     

CBCT assessment of alveolar buccal bone level after RME

Objective:To evaluate the maxillary alveolar buccal bone levels after expansion with banded and bonded expanders, using cone-beam computed tomography (CBCT).Materials and Methods:The population sample consisted of 22 patients who required expansion during their comprehensive treatment; 10 patients (five males and five females) with a mean age of 13.5 years (CVMS 3) had bonded hygienic expanders, and 12 (six males and six females) with a mean age of 12.6 years (CVMS 3) had banded hyrax expanders. CBCT was taken both before (T1) and 6 months after last activation (T2). Measurements were made for buccal bone thickness (BT), buccal marginal bone level (MBL), and bone thickness level (BTL) at the right first molar (M_Rt), left first molar (M_Lft), right first premolar (PM_Rt), and left first premolar (PM_Lft). A mixed-design analysis of variance assessed differences between and within the groups. Post hoc t-tests were completed on significant analysis of variance results to determine where differences occurred.Results:Analysis of variance revealed no significant differences between or within the two groups. BT significantly decreased horizontally following rapid maxillary expansion. The amount of bone lost was −0.59 mm M_Rt, −0.72 mm PM_Rt, −0.50 mm M_Lft, and −0.57 mm PM_Lft (P < .003).Conclusions:There was no significant difference between or within the two groups. Buccal bone loss in the vertical dimension (MBL) only showed significance in the banded group for M_Rt (0.63 mm) and PM_LFt (0.37 mm) as evidenced by the paired t-test (P < .05).     

Impact of orthognathic surgery on the prevalence of dehiscence in Class II and Class III surgical-orthodontic patients:: A cone beam computed tomographic study

ObjectivesThe objectives were to evaluate and compare the presence of bone dehiscence before and after orthognathic surgery.Materials and MethodsIn this retrospective study, 90 cone-beam computed tomography (CBCT) scans from 45 patients were evaluated. Class II (n = 23) and Class III (n = 22) orthodontic patients who were being prepared for orthognathic surgery were measured. CBCT scans were obtained about 30 days prior to (T0) and 6 months after (T1) double jaw orthognathic surgery. The distance between the cemento-enamel junction (CEJ) and the alveolar bone crest was assessed at the buccal and lingual surfaces of all teeth, on both sides and arches, except for the second premolars and the second and third molars. A total of 1332 sites were measured for Class II (644) and Class III (688) patients. The software used was OsiriX (version 3.3 32-bit). Data were compared with Wilcoxon and McNemar tests at the 5% level.ResultsBone dehiscence before surgery was present in 26% and 15% of the Class II and III groups, respectively. The presence of dehiscence increased to 31% in the Class II and 20% in the Class III patients after surgery (P < .05).ConclusionsThe prevalence of dehiscence increased slightly in Class II and Class III surgical-orthodontic patients after orthognathic surgery. Temporary vascular supply reduction and oral hygiene difficulties may explain these results; however, more studies are needed.     

Horizontal alteration of anterior alveolar ridge after immediate implant placement: A retrospective cone beam computed tomography analysis

PURPOSEThe aim of this study was to evaluate the labio-lingual alterations of the alveolar bone where the implant was placed immediately after tooth extraction.MATERIALS AND METHODSImplants were placed immediately after tooth extraction on anterior alveolar ridges in the maxilla and mandible. The pin-guide system was used to help determine the location and path of implants during the surgical process. The horizontal distance from implants to the outer border of alveolar bone was measured at the rim and middle of the implants in the cone beam computed tomography images. The alteration of alveolar bone was evaluated comparing the horizontal distances measured immediately after surgery and 3 months after surgery.RESULTSThe results show that more resorption occurred towards the labial bone than the lingual bone in the maxilla. A similar amount of labial and lingual bone resorption was observed in the mandible.CONCLUSIONConsidering the horizontal alteration of alveolar bone, labio-lingual positioning of the implant towards the lingual bone in the maxilla and at the center of the alveolar ridge in the mandible is recommended when it is placed immediately after tooth extraction.     

Root proximity and cortical bone thickness effects on the success rate of orthodontic micro-implants using cone beam computed tomography

Objective:To evaluate factors (root proximity and cortical bone thickness) affecting the success rate of orthodontic micro-implants (OMIs) using cone-beam computed tomography (CBCT) images.Materials and Methods:We examined 172 OMIs (1.2–1.3 mm in diameter, 8 mm in length) implanted into the maxillary buccal alveolar bone of 94 patients (33 men, 61 women) with malocclusion. Root proximity and cortical bone thickness were measured, and the correlations between these measurements and OMI success rates were evaluated.Results:The overall success rate was 90.7% (156/172). The success rate increased as the distance between the root surface and OMI increased, showing a highly significant statistical correlation (P < .05). As the cortical bone thickness increased, the success rate increased, showing a slight, nonsignificant correlation (P > .05). Thus, the success rate of OMIs was affected more significantly by root proximity than cortical bone thickness.Conclusions:When inserting OMIs, increasing the distance from the OMI to the root surface will significantly improve success rates.     

Retrospective analysis of maxillary sinus septa – A cone beam computed tomography study

BackgroundSinus lift procedures have become a routine and reliable way to gain bone volume in the posterior maxilla for implant placement. The presence of an antral septum in the maxillary sinus increases the risk of complications and subsequent implant failure. This study was designed to estimate the prevalence of maxillary sinus septa and its correlation with age, sex, dentition status and the risk of perforating the Schneiderian membrane using cone beam computed tomography (CBCT).MethodsThis retrospective, cross-sectional study consisted of a total of 178 CBCT images (100 male, 78 female), 63.0% were dentate, 36.0% partially dentate and 1.1% edentate subjects with a mean age of 35 ± 45 years was analyzed to determine the prevalence, height, location, and orientation of maxillary sinus septa. The septa were classified according to the modified Al-Faraje’s classification into VII septal patterns, and the risk of perforation of the Schneiderian membrane was estimated. The chi-square test was used to compare categorical variables, and Student’s t-test and the Kruskal-Wallis test were used to compare continuous variables.ResultsSepta were present in 25.6% of the sinus segments (37.64% of the subjects). The mean septum height was 5.22 mm ± 2.06 in males and 6.27 mm ± 3.55 in females. The majority of septa were located in the middle 76.92%, while 4.40% were anterior, and 18.68% were posterior; 76.92% were in a buccopalatal direction, whereas 23.08% were in an anteroposterior direction. Class III was the most prevalent type. Overall, 60.4% had a moderate risk of membrane perforation, 30.8% had a low risk, and only 8.8% had a high risk.ConclusionThree-dimensional CBCT image analyses can be used as a diagnostic tool to provide accurate information that can help avoid unnecessary intra- and postoperative complications during sinus augmentation procedures by identifying the anatomic structures inherent to the maxillary sinus.     

Peridental bone changes after orthodontic tooth movement with fixed appliances: A cone-beam computed tomographic study

Objective:To quantify treatment-related changes in peridental bone height and thickness in orthodontic patients.Materials and Methods:Cone-beam computed tomographs (CBCTs) of 43 patients (24 female, 19 male; mean age: 25 years, 5 months) who underwent orthodontic treatment with multibracket appliances for at least 1 year were chosen for retrospective evaluation. Dehiscence depth and changes in bone width and tooth inclination were determined for 954 teeth.Results:There was a significant decrease in peridental bone height (dehiscence; −0.82 ± 1.47 mm) and bone thickness (−0.56 ± 0.7 and −0.69 ± 0.9 mm at 5 mm and 10 mm apical to the CEJ, respectively) during treatment (P < .001). A significantly greater dehiscence depth with increased vertical bone loss occurred in patients older than 30 years. In patients <30 years old, approximately 20% of the teeth showed defect depths >2 mm before treatment. In 90% of these patients, at least one tooth was affected. The maxillary canines and all mandibular teeth showed a higher risk for vestibular bone loss. Treatment changes in tooth inclination were correlated with horizontal bone loss.Conclusions:Based on these results, it seems reasonable to recommend that peridental bone in orthodontic patients older than 30 be evaluated on a routine basis due to the risk of increased vertical bone loss. Ninety percent of patients younger than 30 showed reduced bone height (dehiscence) of the periodontium of at least one tooth.     

锥形束CT对微螺钉前牙根间植入区骨量的分析

目的 通过对微螺钉种植支抗前牙根间植入区骨量进行三维测量分析,为前牙根间植入位点的选择提供参考.方法 对36名成人患者的上、下颌前牙区行锥形束CT扫描及三维重建,分别测量U/L11(上/下颌中切牙根间),U/L12(上/下颌中切牙和相邻侧切牙根间),U/L23(上/下颌侧切牙和相邻尖牙根间)距上、下前牙釉牙骨质界3mm、5 mm、7 mm及9mm水平的根间距(D1)和牙槽骨宽度(D2).采用SPSS 17.0软件进行单因素方差分析和Duncan法进行两两比较.结果 相邻两牙根间最小距离D1:从大到小依次为U11＞U23＞L23＞L11＞U12＞L12,所有牙位越往根尖方向D1越大,其中只有U11,U23分别距离釉牙骨质界5mm和7mm根间距大于3mm,相邻两牙根间唇舌向牙槽骨宽度D2为:U11＞L11,U12＞L12,L23＞U23,不同水平D2值在3.82～6.62mm之间.结论 上、下颌前牙区,上颌中切牙之间及上颌侧切牙和尖牙之间的根间区是植入微种植体较理想的部位.