无托槽隐形矫治器配合微种植钉远移磨牙的三维有限元研究

目的 应用三维有限元模型研究无托槽隐形矫治器配合不同植入位置微种植钉远移磨牙时的初始上颌前牙位移及尖牙区应力分布情况。方法 选取于2021-02-16在大连市口腔医院正畸科就诊的需采用无托槽隐形矫治器行远移磨牙非减数正畸治疗的1例女性患者作为建模对象。构建三维有限元模型,模拟微种植钉位于第二前磨牙与第一磨牙之间、第一磨牙与第二磨牙之间,分别距离牙槽嵴顶4、6、8、10 mm的8种工况,并在微种植钉与尖牙唇面的舌侧扣之间加载1.47 N正畸力。分析加力1 s后8种工况的上颌前牙位移及尖牙牙周膜应力分布情况。结果 8种工况中,上颌中切牙均呈现牙冠唇向、牙根腭向的位移趋势;上颌中切牙牙冠唇向位移量随微种植钉高度的增加而减小,且微种植钉位于相对近中（上颌第二前磨牙与第一磨牙之间）时产生的位移量更小。8种工况中,上颌尖牙均呈现牙冠唇向、牙根腭向的位移趋势,且牙冠呈现唇倾趋势;上颌尖牙牙周膜最小主应力绝对值随微种植钉高度的增加而增大,且微种植钉位于相对近中时产生的最小主应力更大。结论 无托槽隐形矫治器配合微种植钉远移上颌磨牙时,配合本实验8种工况中相对近中的更高位微种植钉利于切牙转矩控制,配合相对...     

材料厚度对无托槽隐形矫治器固位力影响的实验研究

目的研究材料厚度对无托槽隐形矫治器在不同牙位脱位时固位力大小的影响,为临床设计附件及指导患者摘戴矫治器提供理论参考。方法制作标准下颌牙列阳模四副及相应的无托槽隐形矫治器四副。研究分为4组：1．00mm厚度无附件组,0．75mm厚度无附件组,1．00mm厚度有附件组,0．75mm厚度有附件组。采用万能材料试验机测试在不同牙位脱位时矫治器固位力的大小。结果不同材料厚度及附件设计影响下四组间矫治器固位力有统计学差异（F=10．10,P〈0．01）。附件能明显增加隐形矫治器固位力,1．00mm有附件组、0．75mm有附件组与其他无附件组比较,平均脱位力值大（P〈0．05）;1．00mm厚度有附件组比0．75mm厚度有附件组平均脱位力值大（P〈0．05）;脱位部位不同对固位力影响有统计学差异（F=12．03,P〈0．01）,在第二磨牙颊侧及第一磨牙舌侧测试时平均脱位力值较小。结论附件能够显著增加隐形矫治器固位力;1．00mm厚度有附件隐形矫治器固位力较大。     

北京地区黄种人数字化三维正常(牙合)模型牙冠角度和凸距的测量

目的采用层析法重建30副北京地区黄种人未经正畸治疗的数字化正常(牙合)模型,并测量牙冠倾角、转矩和凸距,为我国直丝弓托槽的研发提供基础.方法利用北京口腔医院正畸科与清华大学共同开发的牙(牙合)模型三维重建系统及测量软件进行重建和测量.结果北京地区黄种人正常(牙合)牙列的特点有:①牙冠倾角:上、下颌切牙、尖牙及上颌第二磨牙的牙冠近中倾斜度较美国人小,尤其以上、下尖牙显著.②牙冠转矩:上颌中、侧切牙的唇向倾斜度较美国人大,而上、下尖牙的舌向倾斜度较小.③牙冠凸距:下颌第一磨牙的牙冠凸距较美国人大.结论我国北京地区黄种人正常(牙合)牙冠倾角、转矩和凸距有显著的自身特点,应当积极地研制和开发基于我国正常(牙合)特点的直丝弓矫治器.     

不同前牙唇倾度及内收压低步距下隐形矫治器作用的比较：三维有限元研究

目的:应用有限元分析法探究使用隐形矫治器治疗不同前牙唇倾度以及不同内收压低移动步距下,以分步法内收前牙的牙齿移动特点。方法:建立使用隐形矫治器分步法内收上颌前牙的有限元模型,依据中切牙及侧切牙的唇倾度分为工况1:U1-SN=105°、工况2:U1-SN=115°、工况3:U1-SN=125°,牙齿移动总步距为0.2 mm,包括沿牙合平面的内收以及沿牙体长轴方向的压低,每组工况以内收量a:0.18 mm、b:0.14 mm、c:0.10 mm进行分组,分析上述不同情况下的牙齿移动特点。结果:在不同前牙唇倾度以及内收模式下,中切牙、侧切牙均表现为牙冠向舌侧、牙根向唇侧的倾斜移动,第二前磨牙至第二磨牙表现为牙冠向近中的倾斜移动。内收步距越大,前牙冠舌向位移量越大,前牙转矩改变量越大,第二前磨牙至第二磨牙牙冠近中移动量越大。结论:无托槽隐形矫治器在内收前牙时引起前牙的舌倾及伸长、后牙的近中倾斜,其移动量与内收步距呈正比,预设计的前牙绝对压低量无法抵消由牙齿内收引起的相对伸长量。     

北京地区黄种人数字化三维正常he模型牙冠角度和凸距的测量

目的 采用层析法重建30副北京地区黄种人未经正畸治疗的数字化正常he模型，并测量牙冠倾角、转矩和凸距，为我国直丝弓托槽的研发提供基础。方法 利用北京口腔医院正畸科与清华大学共同开发的牙he模型三维重建系统及测量软件进行重建和测量。结果 北京地区黄种人正常he牙列的特点有：①牙冠倾角：上、下颌切牙、尖牙及上颌第二磨牙的牙冠近中倾斜度较美国人小，尤其以上、下尖牙显著。②牙冠转矩：上颌中、侧切牙的唇向倾斜度较美国人大，而上、下尖牙的舌向倾斜度较小。③牙冠凸距：下颌第一磨牙的牙冠凸距较美国人大。结论 我国北京地区黄种人正常he牙冠倾角、转矩和凸距有显著的自身特点，应当积极地研制和开发基于我国正常胎特点的直丝弓矫治器。     

离体上颌第一、二磨牙在釉牙骨质界截面的牙体硬组织厚度测量

目的观察上颌第一、二磨牙在釉牙骨质界(cemento-enamel junction,CEJ)的截面几个方向的牙体厚度。方法25个离体的上颌第一磨牙,22个上颌第二磨牙。从CEJ横断牙冠,将截面图象输入计算机中,用photoshop6.0软件测量牙面到髓腔的距离,方向分别是颊、腭、近中、远中、近中颊、远中颊、近中腭、远中腭。结果在CEJ平面厚度最小处是上颌第二磨牙的近中(平均2.55mm),最厚处是上颌第一磨牙近中舌(平均3.34mm),总体看以近中颊、远中颊、进中舌、远中舌部位相对较厚。结论本研究强调了在釉牙骨质界平面测量牙体厚度对于牙体预备的价值。     

不同厚度热压膜材料的力学性能研究

目的 测量并比较不同厚度的热压膜材料在不同处理方式下的拉伸力学性能,为临床选用适宜厚度的热压膜材料制作无托槽隐形矫治器提供一定的参考.方法 选用厚度为1mm、0.75mm、0.5mm的Biolon膜片,应用万能材料试验机测量并比较三种厚度的热压膜材料在未处理、热成形后以及人工唾液浸泡两周后的最大应力和弹性模量.结果 三种厚度的膜片在不同的处理方式下,Biolon 1.0mm膜片的弹性模量和最大应力最大,Biolon 0.5mm膜片最小.结论 不同厚度的同一种膜片具有不同的力学性能,厚度对材料的力学性能有一定影响.厚度越厚,材料的弹性模量和最大应力越大.     

67名正常青年人上前牙区唇、腭侧骨厚度测量分析

目的:对汉族正常青年人上前牙区不同位点的唇、腭侧牙槽骨厚度进行测量,为术前评估、治疗方案制定及预后评估提供参考。方法:通过锥形束CT(CBCT)对67名符合条件的汉族青年志愿者进行上颌骨扫描。三维重建后,对前牙区唇、腭侧骨厚度进行测量。利用SPSS17.0软件包对测量数据进行配对t检验、独立样本t检验、方差分析及χ2检验。结果:1唇侧骨板除所有前牙L5处及上颌尖牙L1处厚度均数>1.00 mm外,其余测量位点唇侧骨板厚度均数均<1.00mm,而腭侧骨板厚度均数均>1.00 mm;2唇侧骨板厚度均小于腭侧骨板厚度(P<0.001);33种前牙唇侧骨板厚度在参考线L3与L4处厚度最小(P<0.001),腭侧骨板厚度自L1至L5逐渐增大(P<0.05);4仅在上颌尖牙L2处及所有前牙L5处唇侧骨板厚度<1.00 mm的频率<50%,男性上颌侧切牙L3、L4处及上颌尖牙L4处唇侧骨板缺如所占频率>50%;5男性切牙区唇侧骨板凹陷角度较尖牙小(P<0.05),唇侧骨板最凹点与根尖点之间的距离在男性上颌中切牙最大(P<0.05),女性牙位间无显著差异。结论:正常青年人上前牙牙槽骨骨板菲薄甚至缺如,且唇、腭侧骨厚度和形态存在差异。     

不同厚度热压膜材料厚度稳定性的研究

目的测量并比较不同厚度的热压膜材料在不同处理方式下厚度变化的趋势,为临床选用适宜厚度的热压膜材料制作无托槽隐形矫治器提供一定的参考。方法选用厚度为1.0、0.75、0.5 mm的Biolon膜片,应用电子游标卡尺测量并比较3种厚度的热压膜材料在未处理时,热成形后以及人工唾液浸泡2周后的厚度。所得数据应用SPSS 10.0软件包进行两个独立样本的秩和检验。比较不同处理方式对材料厚度变化的影响以及处理方式对材料厚度的影响与材料初始厚度的关系。结果3种厚度的材料经过热成形处理后,厚度变薄。其中Biolon 0.75 mm的膜片厚度平均减少了0.14 mm、Biolon 1.0 mm的膜片厚度平均减少了0.22 mm、Biolon 0.5 mm的膜片厚度平均减少了0.14 mm。经过人工唾液浸泡2周后,厚度与热成形后相比变厚。其中Biolon 0.75 mm的膜片厚度平均增加了0.02 mm、Biolon 1.0 mm的膜片厚度平均增加了0.03 mm、Biolon 0.5 mm的膜片厚度平均增加了0.02 mm。结论不同的处理方式对材料厚度的影响不同,其影响的效果与材料最初的厚度有关系。通过以上研究可以看出,Biolon 0.75 mm膜片在厚度的稳定性上似乎比同种品牌中其他厚度的膜片具有一定的优势。     

节段正轴辅弓远移尖牙的疗效观察

目的:探讨重度拥挤伴尖牙近中唇移过低位病人拔除4个第一前磨牙后,早期用节段正轴辅弓远中、牙合向移动尖牙,结合直丝弓矫治器的矫治疗效,为临床应用提供依据。方法:对12例(共24个尖牙)前牙拥挤和伴有尖牙近中唇移过低位的病例,在拔除第一前磨牙1周后应用自行弯制的节段正轴辅弓牵引尖牙远中、牙合向移动,同时观察尖牙、磨牙的移动情况和临床效果。结果:经过早期使用节段正轴辅弓,尖牙5个月平均向远中移动5.2 mm(速率1.04 mm/月),牙合向移动5个月平均3.8 mm(速率0.76 mm/月)。通过后期的MBT直丝弓矫治器,12例病人覆牙合、覆盖正常,尖牙和第一磨牙达到理想的中性咬合关系,上下颌牙齿尖窝交错,咬合关系良好,尖牙轴倾度正常,支抗磨牙无明显移动。结论:早期应用节段正轴辅弓和后期直丝弓矫治器,进行拥挤伴尖牙近中唇移过低位的拔牙矫治,不失为一种有效的治疗新方法。     

中国汉族成人后牙区硬腭黏膜厚度测量及各组织学层次分布规律研究

目的 本文测量中国汉族人群中后牙区硬腭黏膜的厚度,分析其变化规律及相关因素,观察硬腭黏膜固有层结缔组织各组织学层次的厚度、特点及分布规律。方法 36例患者根据牙龈生物型（gingiva biotype）分为三组,使用骨探测法（bone sounding）测量由尖牙至第二磨牙腭侧共45个位点硬腭黏膜的厚度,采集牙周软组织增量手术中移植软组织修剪下来的剩余组织,筛选具有硬腭黏膜全层的样本,采用免疫组化技术,镜下观察结缔组织的组织学特点及分布规律。结果 硬腭黏膜平均厚度(3.52±1.02）mm、尖牙区为(3.26±0.81）mm、第一前磨牙区为(3.57±1.05）mm、第二前磨牙区为(3.72±1.04）mm、第一磨牙区为(3.33±0.96）mm、第二磨牙区为(3.73±1.11）mm;硬腭黏膜的厚度与性别、年龄无显著相关性,与牙龈生物型之间存在统计学差异;HE染色显示硬腭黏膜结缔组织层具有致密的胶原纤维,由第二前磨牙区域开始出现明显的黏膜下层,在第一磨牙区域多见疏松结缔组织,内含大量脂肪组织、血管、腺体等。结论 在中国汉族人群中硬腭黏膜厚度由尖牙向后逐渐增厚,在第一磨牙区变薄,向第二磨牙区再次变厚;在尖牙、第一前磨牙和第二磨牙区可见由龈缘向腭中缝处黏膜厚度逐渐变厚;硬腭黏膜固有层含有致密的结缔组织,由第二前磨牙区开始出现黏膜下层,含大量脂肪组织、血管、腺体等。     

A new method to assess and measure palatal masticatory mucosa by cone-beam computerized tomography

Aim: The aim of this study was to apply a novel method to obtain high-quality images by cone-beam computerized tomography (CBCT) that consistently allowed the determination of the dimensions of the palatal mucosa.
Materials and Methods: Thirty-one patients participated in this study. At the time of the CBCT scanning, the patients wore a plastic lip retractor and wooden spatulas to retract soft tissues away from the teeth and gingiva. The thickness of the palatal mucosa was obtained at forty different locations on each patient.
Results: Retraction of the lips and cheek allowed a clear observation and measurements of the thickness of the palatal masticatory mucosa. The average thickness of the palatal mucosa was 2.92 mm in the canine area, 3.11 mm at the first pre-molar, 3.28 mm at the second pre-molar, 2.89 mm at the first molar and 3.15 mm at the second molar. Statistical differences were observed at different ages and heights of measurements.
Conclusions: A new non-invasive method to consistently obtain high-quality images of the palatal masticatory mucosa is described. Measurements of this mucosa could be obtained at different locations on the palate.     

Thickness of posterior palatal masticatory mucosa: the use of computerized tomography

BACKGROUND: Periodontal plastic surgery is used to fulfill the esthetic and functional demands of patients. The palatal masticatory mucosa is the main donor site for connective tissue, and the thickness of the graft tissue obtained is an important factor for the success of this technique. The aim of this study was to measure the thickness of masticatory mucosa in the posterior palatal area using computerized tomography (CT). METHODS: The thickness measurements were performed on the images of 100 adult subjects who underwent CT on the maxilla for implant surgery. Twenty-four standard measurement points were defined in the hard palate according to the gingival margin and the middle palatal suture. The radiographic measurements were used after calibration. The data were analyzed to determine the differences in the mucosal thickness according to gender, age, tooth position, and depth of the palatal vault. RESULTS: The overall mean thickness of the palatal masticatory mucosa was 3.83 +/- 0.58 mm (range: 2.29 to 6.25 mm). Females had significantly thinner mean masticatory mucosa (3.66 +/- 0.52 mm) than males (3.95 +/- 0.60 mm) (P <0.0001). The thickness of the palatal masticatory mucosa increased with age. The mean thickness according to tooth site was 3.46 mm (maxillary canine), 3.66 mm (first premolar), 3.81 mm (second premolar), 3.13 mm (first molar), 3.31 mm (the base of the interproximal papilla of the first and second molars), and 3.39 mm (second molar). There was an overall increase in the thickness of the palatal masticatory mucosa as the distance from the gingival margin to the middle palatine suture increased, with the exception of the Ca-d (a point at 12 mm from the gingival margin of the canine) region. There was no significant difference in the thickness of the palatal masticatory mucosa between the groups with high or low palatal vaults. CONCLUSIONS: The palatal masticatory mucosa thickness increased from the canine to premolar region but decreased at the first molar region and increased again in the second molar region, with the thinnest area at the first molar region and the thickest at the second premolar region. The canine to premolar region seems to be the most appropriate donor site that contains a uniformly thick mucosa. CT can be considered an alternative method for the measurement of palatal soft tissue thickness.     

A long-term study of transverse stability of maxillary teeth in patients with unilateral complete cleft lip and palate

summary The aim of this study was to investigate the long term post-treatment transverse stability of the maxillary dental arch in subjects with unilateral complete cleft lip and palate (UCLP) treated by the Harvold/Bøhn method of orthodontic expansion and prosthodontic retention. The treatment of 22 consecutive patients, primarily operated on during the period 1957–60, was completed at a mean age of 18.1 years by the provision of a fixed partial retention prosthesis across the cleft using the cleft side central incisor and canine only as abutment teeth. The cleft side lateral incisor was missing in each case. Dental casts were made at the time of abutment preparation and at six subsequent times with the final observation 13·5 years after treatment completion. Measurements of any shift in the transverse position of cleft side and non-cleft side canines, premolars and first molars were made on standardized photographs of the casts. A constructed antero-posterior palatal line served as 'midline' reference. A mean reduction of width at the final observation, as recorded from the palatal surface to the reference line, was for the cleft side canine: −0·4 mm, the premolar immediately distal to the prosthesis and the first molar: both −1·2 mm. The corresponding mean width reductions on the noncleft side were: canine −0·9 mm, premolar −1·2 mm, first molar −1·6 mm. The rate of movement towards the midline decreased linearly with in(time) for all variables (P < 0·02) but for the cleft side canine.     

隐形矫治磨牙远移的三维有限元分析

目的　构建隐形矫治器上颌磨牙远移的生物力学研究模型,分析矫治体系的初始位移及应力分布特点,为该技术的临床应用提供指导。方法 建立隐形矫治上颌磨牙远移的三维有限元模型,在ANSYS软件中采用非线性有限元法通过数值仿真分析求得受力瞬间牙齿在牙周膜及周围牙槽骨等约束下的移动方式、牙套形变、牙周膜应力分布,并探索适宜的Ⅱ类牵引增强前牙支抗的必要性及适宜力值。结果 第二磨牙远移的同时伴有其牙冠远中倾斜、伸长及舌侧倾斜;其余牙表现为唇/颊倾、压低且位移量与距支抗牙距离成反比。牙周膜等效应力越靠近颈缘越大,距离第二磨牙越远越小,均小于牙周组织可承受最大应力。矫治器在第二磨牙处出现应力集中现象,位移峰值小于材料的弹性极限和拉伸极限强度。100 g Ⅱ类牵引可以有效抵抗前牙唇倾,300 g牵引力作用于牙列后超过牙周膜最大承受力值。结论 使用无托槽矫治技术远移磨牙不能实现单纯的整体移动且支抗牙有一定的支抗丧失,需要进行必要的支抗控制。100 g Ⅱ类牵引即可有效抵抗推磨牙带来的前牙支抗丧失,300 g牵引力作用下牙周膜受力过大,尽量避免使用。     

上颌后牙区腭侧微种植体支抗近远中向植入安全位置的锥形束CT研究

目的    应用锥形束CT（CBCT）研究微种植体支抗在上颌后牙区腭侧植入时,其在上颌第二前磨牙、第一磨牙间以及上颌第一、第二磨牙间近远中向的植入位置,为临床选择微种植体支抗安全的植入位置提供参考。方法    根据纳入标准,从北部战区总医院口腔科选取60例曾于2020年1—12月期间因口腔疾病前来就诊的成人患者的CBCT影像资料作为研究对象。在上颌第二前磨牙、第一磨牙间腭侧以及上颌第一、第二磨牙间腭侧,分别测量距腭尖水平连线12、14、16、18 mm位置时,相邻两牙的腭根距过相邻两牙牙冠接触点与腭尖水平连线垂直的参考线的距离,以及相邻两牙腭根之间的中点分别距此参考线的距离。结果    上颌后牙区腭侧,相邻两牙腭根之间的中点均位于参考线的远中。距腭尖水平连线越高,相邻两牙腭根间中点与参考线的距离越大（P < 0.05）。距腭尖水平连线高度相同的情况下,上颌第二前磨牙、第一磨牙腭根间中点到参考线的距离大于上颌第一、第二磨牙腭根间中点到参考线的距离（P < 0.05）。结论    在上颌后牙区腭侧植入微种植体支抗时,应选择在参考线偏远中位置植入,此时近远中向植入位置接近相邻两牙腭根间的中点,是较为安全的植入位置。     

汉族青年牙周健康人群上颌磨牙腭侧牙槽嵴骨突的CBCT研究

目的:研究汉族青年牙周健康人群中上颌腭侧牙槽嵴骨突的分布、位置及表面黏膜厚度.方法:采用CBCT观察245名受试者上颌第一磨牙至第三磨牙腭侧牙槽嵴骨突的分布,并测量骨突顶点距对应磨牙CEJ的距离和表面最薄处黏膜厚度.结果:245名受试者中在上颌第一、第二和第三磨牙腭侧牙槽嵴骨突的发现率分别为2.45％、31.22％和2...     

Locating the center of resistance of maxillary anterior teeth retracted by Double J Retractor with palatal miniscrews

Objective:To locate the center of resistance of six maxillary anterior teeth retracted by the Double J Retractor (DJR) and to find the optimal position of palatal miniscrews.Materials and Methods:The three-dimensional (3D) finite element model included 12 teeth with two first premolars extracted. The DJR was modeled as a 3D beam element. The miniscrew was sagittally placed between the second premolar and the first molar, and the vertical position of the miniscrew was established at five conditions: 6, 7, 8, 9, and 10 mm apically from the cervical line of the first molar. The length of the retraction lever arm was determined according to the position of the miniscrew, for the direction of retraction force to be parallel to the maxillary occlusal plane. The 3D finite element method was used to determine the location of the center of resistance of the maxillary anterior teeth by visualizing the tooth displacement and stress distribution.Results:As the miniscrew was located apically, the stress spread out to the root apex and the adjacent alveolar bone. At the 8-mm level of miniscrews, a bodily-like parallel retraction could be obtained with DJR.Conclusion:In this study, the center of resistance of the six maxillary anterior teeth retracted by DJR with palatal miniscrews was estimated to be 12.2 mm apically from the incisal edge of the central incisor.