上颌牙槽突颊舌向生理倾斜角的锥形束CT研究

目的    采用锥形束CT（CBCT）影像测量上颌牙槽突颊舌向生理倾斜角,为种植体植入位置和方向的确定提供参考。方法    按照事先制定的纳入与排除标准,从中国人民解放军总医院口腔医学中心影像数据库中随机抽取2014年11月至2015年11月初次就诊患者拍摄的CBCT影像51份（均由NewTom 5G设备拍摄）。采用NewTom 5G自带软件进行重建,重建区域上下边界与上颌牙牙合平面平行,采用0.5 mm层厚、5 mm层间距,在牙列弧形线上对牙槽突进行垂直切割,获得上颌牙槽突的24个等间距的颊舌向断面。使用NNT 5.6软件测量每个颊舌向切面的牙槽突倾角。结果    按从右上颌最后一个层面（第2层）到左上颌最后一个层面（第23层）的顺序,上颌各层面牙槽突倾角平均值或中位值分别为：0°、0°、0°、0°、10.2°、17.4°、23.9°、31.9°、40.7°、42.3°、31.8°、32.6°、41.7°、40.7°、31.8°、22.9°、16.1°、8.2°、0°、0°、0°、0°。左右对称层面牙槽突倾角差异无统计学意义（P > 0.05）。男女之间的牙槽突倾角差异无统计学意义（P > 0.05）。第2～5层和第20～23层（对应于磨牙区）中,牙槽突倾角为0°的牙槽突比例高于颊侧倾斜牙槽突（P < 0.05）。结论    前牙区牙槽突倾角最大,前磨牙区倾角次之,磨牙区倾角逐渐递减为0。前牙区和前磨牙区牙槽突向唇、颊侧倾斜,磨牙区牙槽突在多数情况下呈垂直向,其次为向颊侧倾斜。了解牙槽突倾角有助于种植体植入位置和方向的确定,在不具备种植手术导板的情况下,其参考作用尤其明显。     

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??Objective    To measure the anatomic buccolingual angulation values of the mandibular alveolar process based on CBCT images in order to help determine the implant angulation at the implant treatment-planning phase. Methods    A random sample of 51 CBCT images were selected and analyzed. The NewTom 5G CBCT data sets were reformatted at a 5-mm spacing??with the inferior border of the region of interest parallel to the base of the mandible. Twenty-four buccolingual cross-sectional images of the mandibular alveolar process of each CBCT scan were obtained for angulation measurements by NNT5.6 software. Results    The mean or median values of the buccolingual angulation of the mandibular alveolar process??ranging from 1.8 degrees to 28.5 degrees??were obtained. There were no statistically significant differences on the angulation values of the alveolar process between the right side and left side or between male and female patients??P??0.05??. The number of buccally-inclined alveolar process cross-sections increased from cross-section NO.8 to NO.11??and decreased from cross-section NO.14 to NO.17??which were statistically significant??P??0.05??. Conclusion    The mean or median values of the buccolingual angulation of mandibular alveolar process increase gradually from the anterior tooth region via the premolar region to the second molar region. Most of the mandibular alveolar process cross-sections at the anterior teeth region incline buccally??while most of those at the premolar region and all of those at the molar region incline lingually. Knowing buccolingual angulation values of the mandibular alveolar process before dental implantation may help the clinician plan the orientation of implants.     

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??Objective    To measure the anatomic buccolingual angulation values of the maxillary alveolar process based on CBCT images in order to form a basis for the implant treatment planning?? including the design of implant position and angulation. Methods    A random sample of 51 CBCT images were selected and analyzed. The NewTom 5G CBCT data sets were reformatted at a 0.5-mm spacing?? with the inferior border of the region of interest parallel to the occlusion plane of maxillary teeth. Twenty-four buccolingual cross-sectional images of the maxillary alveolar process were obtained for buccolingual angulation measurements. Results    Mean or median values of the buccolingual angulation of maxillary alveolar process ranged from about 0 degree to more than 40 degrees. Cross-sections distal to the premolar region showed a statistically higher proportion of vertical process ??angulation equals to 0 degree???? compared to cross-sections corresponding to maxillary premolars and anterior teeth region ??P < 0.05??. There were no statistical differences between the angulation of alveolar process both from the right side and left side and from males and females patients ??P > 0.05??. Conclusion    The buccolingual angulation of maxillary alveolar process decreases from anterior teeth region through the premolars region to the molars region?? with the lateral incisor and canine region being the most inclined bucally and a high proportion of the molars region being nearly vertical. Knowing average values of buccolingual angulation of maxillary alveolar process before dental implantation may help the clinician plan the position and orientation of implants?? especially when an implant surgical template is not available.     

下颌牙槽突颊舌向生理倾斜角锥形束CT影像研究

目的    采用锥形束CT（CBCT）影像测量整个下颌骨牙槽突颊舌向生理倾斜角,为种植手术提供参考。方法      按照事先制定的纳入与排除标准,从中国人民解放军总医院口腔医学中心影像数据库中随机抽取2014年11月至2015年11月初次就诊患者拍摄的CBCT影像51例。采用NewTom 5G自带软件进行重建,重建区域上下边界与下颌骨下缘平行,采用0.5 mm层厚、5 mm层间距,在牙列弧形线上对牙槽突进行垂直切割,获得下颌牙槽突的24个等间距的颊舌向切面。使用NNT 5.6软件测量每个颊舌向切面的牙槽突倾角。结果    从右下颌磨牙区（第2层）到左下颌磨牙区（第23层）,牙槽突倾角均值或中位值分别为-27.6°、-28.5°、-26.2°、-21.7°、-17.7°、-12.9°、-7.4°、-2.8°、2.2°、3.7°、4.8°、5.8°、3.5°、1.8°、-2.5°、-6.9°、-12.0°、-15.7°、-20.0°、-24.9°、-27.0°和-28.2°,负值表示向舌侧倾斜。左右对称层面间和男女之间的牙槽突倾角差异均无统计学意义（均P＞0.05）。第2 ~ 7层、第17 ~ 23层绝大多数牙槽突向舌侧倾斜（P＜0.05）;第8 ~ 11层偏向颊侧牙槽突逐渐增多,第14 ~ 17层偏向颊侧牙槽突逐渐减少（P＜0.05）;第10 ~ 15层偏向颊侧牙槽突数目多于偏向舌侧牙槽突数目,偏向舌侧牙槽突比例为7.8%（4/51） ~ 37.3%（19/51）。结论    下前牙区牙槽突倾角值最小,从前磨牙区至第二磨牙区牙槽突倾角值逐渐增大。前牙区主要向颊侧倾斜,前磨牙区主要向舌侧倾斜,磨牙区均向舌侧倾斜。了解牙槽突倾斜方向和倾角大小有助于种植体植入方向的确定,可为种植手术提供参考作用。     

Influence of X-ray beam angulation in the detection of proximal caries: Interobserver agreement in the CCD system

The aim of this study was to assess the influence of changes in horizontal and vertical X-ray beam angulation on interobserver agreement in the diagnosis of approximal caries using a charge coupled device-based digital dental imaging system (digital system) in comparison with a conventional film-based radiography (film system). A total of 40 teeth were radiographed. Projection angles were varied within a range of±20° in the horizontal and vertical direction using both systems. The resulting radiographs of approximal surfaces were observed by six radiologists, and the presence and absence of caries and the depth of any caries they found were evaluated. Results were analyzed by comparing Cohen's kappa values. The overall kappa values in both systems belonged to the same category of agreement strength for any horizontal or vertical beam angle. The deviation of the horizontal angulation, if anything, reduced the kappa values in the digital system, except for score 2 based on rating score for caries depth. On the other hand, the influence of vertical angulation was smaller than that of horizontal angulation at scores 0, 1 and overall. The results of the presentin vitro study, in which there was no apparent discrepancy in the influence of beam angulation on interobserver agreement of the diagnostic abilities, suggest that the digital system plays a useful role in clinical caries diagnosis.     

Influence of adjacent teeth on impacted third molars in the upper and lower jaws

Panoramic radiographs of 1834 patients older than 21 years were evaluated for the prevalence of impacted teeth at different ages. The frequency of impacted teeth by age was constant, that is, the presence of completely impacted teeth could not be related to age.
The interrelationship between the angulation of impacted teeth and the existence of adjacent teeth was studied in individuals older than 61 years. The angulation of most of the completely impacted teeth in the upper-third molar region was horizontal when adjacent teeth were not present, whereas impacted teeth in the upper-third molar region showed vertical angulation when adjacent teeth were present, suggesting that vertically impacted teeth may become exposed by bone resorption or infection and should be removed. The angulation of impacted lower third molars was horizontal irrespective of the presence of adjacent teeth. It appears that the interrelationship between the angulation of completely impacted teeth and the presence of adjacent teeth is different between the upper and lower third molar regions. The angulation of completely impacted teeth and the presence of adjacent teeth should be included in those criteria which determine whether or not completely impacted teeth should be removed.     

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目的    研究不同正畸治疗方法对阻生下颌第三磨牙的影响。方法    选择2005年1月至2008年5月青岛大学医学院附属医院口腔正畸科治疗的第三磨牙阻生青少年患者79例（154颗患牙）,按治疗前下颌第三磨牙倾斜角及矫治是否拔牙分为4组：未拔牙A组（非拔牙矫治且倾斜角≤30°）,未拔牙B组（非拔牙矫治且倾斜角＞30°）,拔牙A组（拔牙矫治且倾斜角≤30°）,拔牙B组（拔牙矫治且倾斜角＞30°）。拍摄正畸治疗前后口腔曲面断层片,测量并计算矫治前后下颌第三磨牙倾斜角及萌出间隙的变化。结果    矫治后拔牙A组第三磨牙倾斜角比矫治前平均减小3.36°,且差异有统计学意义（P < 0. 05）;其余各组矫治前后差异均无统计学意义。矫治后各组下颌第三磨牙的萌出间隙均高于矫治前,且差异有统计学意义（P < 0. 05）,其中拔牙组矫治前后萌出间隙变化尤为明显。结论    对于原倾斜角较小的下颌第三磨牙,拔牙有利于改善第三磨牙的萌出角度;与非拔牙矫治相比,拔牙矫治更多地增加了下颌第三磨牙的萌出间隙,有利于下颌第三磨牙的萌出。     

中国人与白种人、日本人正常（牙合）牙齿形态的比较研究

目的：比较中国人与白种人、日本人正常He数据，为临床应用直丝弓矫治器提供参考。方法：选择中国人正常He数据中的轴倾度、转矩和冠凸矩分别与白种人、日本人正常糌数据进行比较分析。结果：中国人正常糌牙齿形态与白种人有显著的差异，而与日本人大致相似，但也有一定差别。结论：临床使用无论是基于白种人或日本人正常He数据的直丝弓矫治器时，都应做一定的修改。     

牙齿近远中倾斜度的影像学评价方法进展

牙齿近远中倾斜度是指牙体长轴与牙合平面垂线所成的角度，作为评价正畸治疗的指标之一，正畸医生需要对其在治疗前后密切关注。临床上现有评价牙齿近远中倾斜度的影像学方法主要包括曲面断层测量与锥形束CT(cone beam computed tomography, CBCT)测量，两者各有其特点。本文就近年来曲面断层与CBCT测量牙齿近远中倾斜度的方法及其各自准确性进行综述。     

Controlled force measurements of gingival attachment level made with the Toronto automated probe using electronic guidance

Precise reproduction of probe placement, probing force and probing angulation may influence the reliability of replicate gingival attachment level measurements (GAL). Reproducibility of GAL measurements was determined with the Toronto automated periodontal probe (TAPP) in which a novel electronic guidance system was incorporated to improve the precision of probing angulation. Bench testing of forces produced at the probe tip was performed with an electronic balance. Reproducibility and precision of force generation were tested in a variety of instrument configurations using laboratory models. The data indicated that highly precise and reproducible probing forces can be generated with the TAPP over a large (10 to 90 g) probing range. Instrument precision was +/- 0.27 mm when probing forces of 40-60 g were used. The guidance system provided accurate and reproducible measurements of the probe handle in both roll and pitch axes when compared with precisely machined wedges (R = 0.99, roll; R = 0.98, pitch). Deviation of probing angulation greater than 5 degrees on replicate measurements of GAL was associated with significant alterations in the location of circumferential probe placement and in the size of the difference between GAL measurements (delta GAL). Clinical assessment of probing angulation in 6 patients demonstrated that delta GAL was 0.40 +/- 0.05 mm when probing angulation deviation was less than 5 degrees but increased to 0.96 +/- 0.11 mm when deviations exceeded 5 degrees. Taken together, these data indicate that the regulation of probing angulation in clinical measurement of GAL with the TAPP is an important determinant of the reproducibility of periodontal probing.     

Does angulation of osteotome during pterygomaxillary dysjunction for a Le Fort I osteotomy influence stress transmission to the orbit? A finite element simulation in normal and cleft maxillae

Pterygomaxillary (PTM) dysjunction is a technique-sensitive step in Le Fort I osteotomy. Various studies implicate improper osteotomy techniques and anatomical variations of the midface in ophthalmic/orbital complications. The aim of this study was to assess the stress distribution and its transmission to the orbit during PTM dysjunction while using different angulations of the osteotome. The study involved the generation of two virtual models from the computed tomographic images of a non-cleft and cleft patient. Nonlinear, three-dimensional finite element analysis (3D-FEA) of the models was performed for mapping the equivalent stress (in megapascals [MPa]) and maximum principal stress (in MPa) at the PTM junction, optic canal, and superior orbital fissures. The results of our study showed that there was no significant change in the transmission of stress to the bony orbit in a normal maxilla, with variations in the angulation of the osteotome. However, the equivalent stress generated for the cleft maxilla showed an increase that could potentiate indirect globe injury. The study shows that a judicious technique for PTM dysjunction and a cautious approach in cleft maxillae could reduce incidence of ophthalmic complications in clinical practice.     

正畸患者对上颌牙列中线轴向倾斜的审美评价

目的:探讨正畸患者对不同程度上颌牙列中线轴向倾斜的审美评价。方法:采用上颌牙列中线不同程度轴向倾斜的图片模型,制作电子问卷软件,对203位符合条件的正畸患者(男79人,女124人)分理想值、觉察值和容忍值3个层次进行问卷调查。结果:受试对象对女性图片上颌牙列中线轴向向左、右倾斜的平均觉察值分别是4.7°、4.9°,容忍值是9.7°、9.5°;男性图片则为4.1°、5.1°和9.0°、9.7°。其中除了男性图片左、右侧的觉察值之间有统计学差异之外(P<0.05),其余评价值左、右侧之间无统计学差异(P>0.05)。觉察值的中位数和四分位数间距均为4.0°,2.0°;容忍值则均为10.0°,6.0°。女性和男性图片平均理想值分别为0.1°和0.4°,且与总体均数μ=0间无统计学差异(P>0.05)。女性受试者对男性图片牙列中线右侧轴向倾斜的觉察值要明显低于男性受试者。结论:该审美评价的3个层次是合理的,其研究结果对口腔科医生具有临床指导意义。     

Possible problems of moulding the regenerate in mandibular distraction osteogenesis – Experimental aspects in a canine model

INTRODUCTION: Moulding of the regenerate created by distraction osteogenesis has been shown clinically to be efficient and good enough so that for complex three-dimensional deformities, final adjustments by moulding the regenerate may be part of the treatment plan. This study assessed possible drawbacks of moulding a regenerate, taking into consideration compressive and tensile forces acting simultaneously on the fresh callus. METHOD: Distraction osteogenesis in 15 Beagle mandibles was performed using custom made devices which allowed for lengthening as well as for angulation. After linear distraction of 10 mm, a defined 20 degrees angulation was performed in one step. The position of the fulcrum of the device allowed simultaneously compression and stretching of the regenerated bone. Effects on bone healing were assessed after 6 and 13 weeks of consolidation respectively and compared with a control group where only linear distraction was performed. RESULTS: Radiological and histological investigations demonstrated that no significant differences between the biological behaviour of the compressed and the stretched zones of the regenerate could be found. However, there were signs showing the more critical character of the stretched area. After 6 weeks of consolidation some specimens revealed delayed ossification of the stretched zone. Under stable conditions, this delay was compensated for after 13 weeks of consolidation and complete osseous healing occurred. CONCLUSION: Under stable conditions, a fresh regenerate can be moulded to a considerable extent without permanently endangering osseous healing. Nevertheless tensile forces acting on the regenerate should be minimized to prevent damage to the new bone. This can be achieved by overdistraction prior to callus moulding or by gradually changing the vector of distraction during the lengthening process.     

Relationship of maxillary molar root angulation and palatal vault height

If the vertical angulation of maxillary molar roots could be reliably predicted, this might affect the choice of roots resection procedures. In an attempt to develop this prediction, angulation of palatal roots was compared to palatal vault height. Human cadaveric maxillae with molars were sectioned faciopalatally through each tooth root to the palatal midline and photographed. Root angles and palatal height were measured on the photographs in relation to a reference line connecting buccal and palatal cementoenamel junctions (CEJ). Palatal vault heights were classified as low, medium, or high according to the perpendicular distance from the midpalatal suture to the reference line. Root angles were subtended by a line following the length of pulp canals and perpendicular to the CEJ reference. Analysis by Spearman's Rank Correlation Coefficient demonstrated a weak nonsignificant relationship between palatal vault height and the angulation of the various maxillary molar roots. Thus, palatal vault height would not be a reliable predictor of root angulation if this were to be used as a basis for root retention.     

Assessment of mesiodistal tooth angulation on the panoramic radiograph

Tilting of the head has been suggested as a potential source of error when the clinician assesses the angulation of teeth in the panoramic radiograph. If a reference line that could be stable in variations of head positioning during the radiographic exposure could be found, then the examination of the radiograph would be more accurate. We examined the effects of three different head positions on the panoramic image in ten volunteer patients. Our findings suggest that the upper and lower margins of the film are useful reference lines in estimating the mesiodistal angulation of six anteriors, and the mandibular plane is more useful in assessing the angulations of posterior teeth and canines.     

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正畸治疗的目的是通过改变牙齿整体的三维位置从而获得相对正常的咬合关系,因而正常是诊断和治疗错畸形的基础与标准。牙齿近远中倾斜度是正常重要组成因素之一,目前测量牙齿近远中倾斜度的方法各有千秋。本文就各种测量牙齿近远中倾斜度的方法做一综述。     

The effect of working tip angulation on root substance removal using Er:YAG laser radiation: an in vitro study

OBJECTIVES: The present investigation attempted to determine the amount of cementum and/or dentin removal with Er:YAG laser radiation, dependent on the angulation of a specially-developed application tip. MATERIAL AND METHODS: Subject of the study were 150 extracted incisors, canines, premolars, and molars. Source of laser radiation was an Er:YAG laser device emitting pulsed infrared radiation at a wavelength of 2.94 microm with a pulse duration of 250 micros and a pulse repetition rate of 10 pps. The samples of the 3 study groups were irradiated with 380 laser pulses at radiation energies of 60 mJ (group A), 100 mJ (group B), or 180 mJ (group C). In each group, 10 samples were treated at working tip angulations of 15 degrees , 30 degrees , 45 degrees , 60 degrees , and 90 degrees. The substance removal was determined 3-dimensionally using a newly developed laser scanning system (100,000 surface points per sample, accuracy 5 microm) and a special image-analysing software (Match 3D). Statistical analysis was completed with ANOVA followed by multiple comparisons using the Scheffé-test and with linear regression analysis according to Pearson-Bravais (p < 0.05). RESULTS: Strong dependence of substance removal, both determined as maximum depth of the defects (0.5% quantil) as well as defect volume, on the angulation of the working tip was shown. At 60 mJ, the depth of the defects was 41.39 (+/- 32.55) microm at an angulation of 15 degrees and that at 90 degrees was 181.39 (+/- 74.42) microm (R2= 0.921). For the radiation energy at 100 mJ, the depth of the defects ranged from 51.96 (+/- 26.86) microm at 15 degrees to 306.64 (+/- 62.44) microm at 90 degrees (R2 = 0.983). Choosing radiation energies at 180 mJ, the depth of the defects ranged from 64.73 (+/- 27.73) microm at 15 degrees to 639.89 (+/- 47.28) microm at 90 degrees , on average (R2 = 0.853). CONCLUSIONS: The results of the present study provide clear evidence that besides the physical radiation parameters, also the parameters of clinical handling, in particular the angulation of the application tip, has a strong influence on the amount of root substance removal using Er:YAG laser radiation.     

Evaluation of off-axis projection geometry in dental panoramic radiography

New electronic imaging capabilities afforded by the use of linear charged-couple device arrays allow acquisition of three-dimensional information through simultaneous recordings from multiple sensors situated at different fixed angles. In theory, the resulting data can be processed to yield images tailored to specific diagnostic tasks that can be produced and manipulated on demand after exposure. The first step to determine the practical potential of such a system in panoramic radiography is to demonstrate the degree to which specific changes in projection geometry can be used to improve performance of selected diagnostic tasks of clinical interest in dentistry. Hence, the purpose of this investigation was to explore the potential to reduce proximal overlap that exist in current panoramic radiographs and also to displace the blurred image of the spine from areas of diagnostic interest through the use of off-axis projection geometry of the slit beam of radiation. As the off-axis angulation increased, more embrasures in the different areas of the dental arches of skull specimens were opened; the effects of beam angulation in the number of open embrasures was statistically significant (ANOVA, p < 0.05). A hypothetical multibeam system significantly improved the projection geometry toward the creation of images that contain little, if any, proximal overlap when compared with the conventional bilaterally symmetrical projection geometry system (t test, p < 0.001). At 6 degrees off-axis projection angle, the system was able to clear completely the anterior area from the superimposing shadow of the spinal column. The results show that multibeam alternatives to the single beam projection can significantly improve diagnostic quality in panoramic radiographs.     

牙齿近远中倾斜度测量方法研究进展

正畸治疗的目的是通过改变牙齿整体的三维位置从而获得相对正常的咬合关系,因而正常牙合是诊断和治疗错牙合畸形的基础与标准。牙齿近远中倾斜度是正常牙合重要组成因素之一,目前测量牙齿近远中倾斜度的方法各有千秋。本文就各种测量牙齿近远中倾斜度的方法做一综述。     

基于锥形束CT的不同垂直骨面型重度骨性Ⅲ类错牙合成人患者上下前牙冠根成角分析

目的    应用锥形束CT分析不同垂直骨面型重度骨性Ⅲ类错牙合成人患者上下前牙牙冠与牙根所成的角度（冠根成角）,为正畸治疗过程中上下前牙更安全而有效地移动提供参考依据。方法    选取2012年1月至2021年1月于大连市口腔医院正畸科就诊的重度骨性Ⅲ类错牙合成人患者152例,根据下颌平面角分为高角组（53例）、均角组（52例）、低角组（47例）,应用Invivo dental 5.0软件将所有患者的锥形束CT影像进行三维重建,测量并比较各组上下前牙的冠根角（CRA）和面轴角（SSA）。结果    各组上下中切牙冠根成角总的比较,差异均有统计学意义（均P < 0.05）。组间两两比较结果显示,上中切牙CRA和下中切牙SSA由大至小均依次为低角组、均角组和高角组,而下中切牙CRA和上中切牙SSA由大至小均依次为高角组、均角组和低角组,差异均有统计学意义（均P < 0.05）;其中,低角组上中切牙CRA > 180°且SSA为负值。结论    重度骨性Ⅲ类错牙合患者上下中切牙冠根成角在不同垂直骨面型之间有显著差异,其中高角和均角患者上中切牙冠相对牙根向舌侧倾斜,且高角患者更加明显;低角患者上中切牙与之相反,表现为牙冠相对牙根向唇向倾斜。3种骨面型患者的下中切牙牙冠相对牙根均向舌侧倾斜,且下颌平面角越小,其牙冠舌向倾斜越明显。