Evaluation of anatomic variations of mandibular lingual concavities from cone beam computed tomography scans in a Malaysian population

Statement of problemLingual plate perforation can be life-threatening when vital structures are damaged during implant placement. Knowledge of the anatomy of lingual concavities is imperative for safe implant surgery.PurposeThe purpose of this clinical study was to determine the prevalence of type of posterior mandibular ridge morphology in a Malaysian population and to evaluate the buccolingual width of the alveolar ridge (Wb and Wc); alveolar ridge height (Vcb); and concavity angle, length, and depth for both left and right first and second molars in different age groups and sexes by using cone beam computed tomography (CBCT).Material and methodsBilateral posterior mandibular lingual concavities at the first and second molars were retrospectively studied in cross-sectional views of 150 CBCT scans (n=600 sites evaluated). The sample size was calculated at a power of 80%, confidence interval of 95%, and margin of error of .05. The buccolingual width from the base and crest of the ridge and the ridge height were measured to determine the type of ridge. For the U-shaped ridge, the concavity angle, length, and depth were assessed. The independent t test was used to compare mean values of CBCT measurements between sexes and tooth type, while the ANOVA and Pearson chi-squared test were used to determine the correlations with age groups and types of ridge morphology, respectively. To compare the left and right readings for first and second molars in the same patient, the paired t test was performed (α=.05 for all tests).ResultsThe Pearson correlation showed a strong agreement between the 2 examiners with an interobserver reliability of 87.3%. Significant difference was noted in all dimensional measurements when comparing right and left first and second molars (P<.001). The degree of concavity was significantly different (P<.05), except for the depth of the concavity at the left molars (P=.075). The type C ridge (51.7%) was the most prevalent ridge among a Malaysian population. Only dimensional measurements were significantly different when compared among age groups (P<.05). Ridge width and height were significantly greater in men (P<.05). Men exhibited greater concavity depth than women in the left second molar region (P=.03).ConclusionsLingual concavity was found in the mandible in 32.8% of a Malaysian population. Significant differences were found in dimensional measurements and degree of concavity between left and right first and second molars, with deeper concavity depth found in second molars. Significant age and sex-related variations were found in the dimensional measurements of the mandible between left and right sides with no significant difference in degree of concavity.     

无牙颌患者牙槽嵴粘膜疼痛阈及其相关因素的研究

目的 :分析无牙颌患者牙槽嵴粘膜疼痛阈的分布、影响规律以及与全口义齿满意度之间的关系。方法 :采用口腔粘膜压力测痛仪和全口义齿满意度问卷对 45名无牙颌患者进行测试调查。结果 :无牙颌患者同颌左右侧牙槽嵴粘膜测试点的疼痛阈之间无显著性差异。牙槽嵴粘膜疼痛阈上颌大于下颌 (P <0 .0 5 ) ,牙槽嵴顶大于颊腭 (舌 )侧 (P <0 .0 5 ) ,颊侧大于腭 (舌 )侧 (P <0 .0 5 )。全口义齿满意度构成因素中的固位稳定、咀嚼、舒适得分与牙槽嵴粘膜疼痛阈呈正相关。全口义齿满意度高的组较满意度低的组上下颌牙槽嵴顶、颊侧和腭 (舌 )侧牙槽嵴粘膜疼痛阈值均高 (P <0 .0 5 )。结论 :戴义齿前牙槽嵴粘膜疼痛阈值高的患者对新义齿容易适应     

下颌无牙颌牙槽嵴牙位划分方法的初步探讨

目的:初步探讨下颌无牙颌牙槽嵴牙位划分方法,为测量分析下颌牙槽嵴形态及其对义齿稳定影响提供定位依据.方法:收集符合标准的下颌无牙颌患者模型302例,从中随机选取50例,通过三维激光扫描获取石膏模型牙槽嵴表面数据,运用SolidWorks软件确定咬合平面、并在牙槽嵴顶线的投影上利用各天然牙中点至中切牙近中面长度占同侧天然牙列近远中长度(正中切牙近中面至第二磨牙远中面)的百分比值确定各牙位,标记并连接各测量点:牙槽嵴顶中央点投影(A),左侧磨牙后垫前缘投影(L),右侧磨牙后垫前缘投影(R),左右磨牙后垫前缘投影连线(LR)的中点(M),连接A、M并标记AM中点C;连接C到各牙位中点标记点,并连接M到后牙区各牙位中点标记点,测量各连线与AM的夹角;统计分析测量的数据.结果:在前牙区,C点到各个牙位中点连线近似位于同心圆上,连线与AM的夹角稳定性高(C.V＜5％);在后牙区,M点到各个牙位中点连线与AM的夹角较C点连接角度的方差和极差更小,稳定性更高(C.V＜5％);同时,利用AM与LR的比值作为定位角度参数建立预测方程,可有效较正各牙位定位偏差.结论:选择下颌牙槽嵴中央线上不同的牙位划分线原点,使用划分线与矢状线的夹角平均值,并通过咬合平面上牙槽嵴顶线投影的高宽比作为参数建立牙位划分角度预测方程,可在下颌牙槽嵴顶线上较稳定地划分各牙牙位.     

Safe zone in anterior mandible related to the genial tubercle for implant osteotomy in a Chinese-Malaysian population: A CBCT study

Statement of problem

The genial tubercle is a clinically palpable landmark in the mandible and can be identified in cone beam computed tomography (CBCT). Its location can be used to measure the safe zone in the interforaminal region of the mandible. These measurements may be helpful for implant treatment planning in patients with complete edentulism.

两侧非对称性下颌牙槽嵴形态对全口义齿稳定性影响的初步探讨

目的：初步探讨下颌两侧非对称性牙槽嵴形态对全口义齿稳定性的影响.方法：利用激光三维扫描仪取得下颌无牙颌标准模型牙槽嵴表面形态数据,通过计算机辅助工程（CAE）软件形成下颌全口义齿,标准形态牙槽嵴黏膜,以及4种左右形态非对称的牙槽嵴黏膜三维有限元模型：首先建立标准牙槽嵴（S）,其次按下颌牙槽骨不同部位吸收至S的1/4高度为条件,分别形成右侧磨牙区吸收（Rm）,右侧后牙区吸收（Rpm）,右侧牙槽骨吸收（Rapm）及左侧前牙区和右侧牙槽骨吸收（LaRapm）的黏膜模型.在S条件下义齿左右两侧咬合面的双尖牙区P,第一磨牙区M1及第二磨牙区M2等6个部位分别设定位于牙槽嵴顶及其颊侧的2个加载位置,共计12个加载点,单侧垂直加载9.8N的力,利用三维有限元分析各条件下义齿最大综合位移.结果：M1加载时各牙槽嵴条件下的义齿最大位移较P和M2加载时的小.各部位加载时LaRapm条件下义齿最大综合位移都较其他牙槽嵴条件下的大.左侧M2加载时的Rapm较Rm和Rpm的大,P加载及右侧M2加载时的Rm、Rpm、Rapm相近,且都大于S.结论：在单侧加载条件下,下颌两侧非对称性牙槽嵴前牙区高度影响全口义齿稳定性.     

基于CT影像的牙种植模板相关的颌骨解剖学研究

目的:通过观测成人颌骨形态结构及其周围骨突的情况,为临床口腔种植手术导板的设计、制作,模板导向孔的安置、深度和方向以及种植角度提供参考数据。方法:对临床上31例上颌骨及44例下颌骨的CT断层图像,应用3D-DOCTOR软件对其各个牙位上相应的牙槽嵴与对应牙的夹角进行观测与测量,并用统计分析软件SPSS13.0加以分析。结果:上颌骨牙长轴与牙槽突的唇腭侧偏移关系有71.92%在偏唇与偏腭20°以内,下颌骨牙长轴与牙槽突的唇腭侧偏移关系有98.68%在偏唇与偏舌20°以内。结论:颌骨牙长轴与牙槽嵴的相对偏斜度可为种植位点的选择和种植导向模板的制作提供理论依据。     

炎症对大鼠牙槽骨骨重建的影响

目的：了解拔牙窝残存炎性组织对拔牙后骨重建过程的影响。方法：健康成年SD大鼠56只,6只用于牙齿折裂炎症感染模型建立的预实验,X线片及病理确定8周为根周存在囊肿或肉芽肿炎症感染的时间点。50只大鼠建立下颌左右第一磨牙根周感染模型,8周后根据X线根尖片取36只根尖部炎症明显的大鼠,根据自身对照原则,左侧实验组牙齿拔除后不刮治,右侧对照组刮除感染组织。术后4周、8周、12周分别进行游标卡尺测量、X线影像学检查和组织学检查,评价拔牙后左右侧牙槽骨骨重建是否有差异。结果：术后4周、8周、12周两组牙槽嵴颊舌侧高度差存在差异,实验组颊舌侧高度差值较大,术后4周、8周实验组新骨形成明显少于对照组。结论：炎症组织使拔牙后颊侧牙槽嵴高度明显下降,拔牙窝的前期修复速度减慢。     

A transcranial radiographic examination of the temporal portion of the temporomandibular joint

The temporomandibular joints of 20 human cadaver heads were examined by means of photography (gross anatomic images) and radiography (lateral oblique transcranial images), using the angle created by a line parallel to the Frankfurt horizontal and a line coinciding with the posterior slope of the most lateral (outermost) portion of the articular tubercle. This lateral eminence angle, made visible through an attached metal wire and a straight stick pin and pertaining to the outermost (zygomatic) portion of the eminentia, was about 45 degrees on both enlarged photographs and enlarged radiographs. There were no significant differences between the photographic and radiographic lateral eminence angles on the right and left sides. A more medially placed angle, yet pertaining to the lateral - and supposedly functional (protrusion) - portion of the glenoid fossa, was about 56 degrees on the right side and 51 degrees on the left side of the radiographic images. There were significant differences between the ipsilateral radiographic lateral and medial eminence angles. A separate decision-making analysis concluded that lateral oblique transcranial radiography is an effective, reliable, and inexpensive method for detection of bony changes in the lateral portions of the temporomandibular joints.     

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...     

Symmetry of the nose after presurgical nasoalveolar molding in infants with unilateral cleft lip and palate: a preliminary study.

OBJECTIVE: To assess nostril symmetry and alveolar cleft width in infants with unilateral cleft lip and palate following presurgical nasoalveolar molding (NAM). SAMPLE AND METHODS: Fifty-seven newborn patients underwent presurgical nasoalveolar molding. Magnified basal view facial photos were taken at four different times: initial visit (T1), before cheiloplasty (T2), 1 month after cheiloplasty (T3), and 1 year of age (T4). Direct measurements from the photos included: (1) nostril width on the affected and nonaffected side; (2) nostril height on the affected and nonaffected side; (3) columella-nasal base angle; and (4) width of the alveolar cleft. Nostril width and height data were used to calculate a ratio of affected to nonaffected side. RESULTS: Effects of nasal symmetry after presurgical nasoalveolar molding were compared between the affected and nonaffected side. The nostril width ratio was 1.7, 1.2, 1.0, and 1.2 for T1 to T4. The nostril height ratio was 0.5, 0.8, 1.0, and 0.9 for T1 to T4. The angle of the columella was 53.3 degrees , 69.9 degrees , 91.2 degrees , and 86.9 degrees for T1 to T4. The average alveolar cleft width was 8.2 mm at T1 and closed down to 2.4 mm before cheiloplasty (T2) in cases with complete cleft. CONCLUSIONS: Infants with presurgical nasoalveolar molding improved symmetry of the nose in width, height, and columella angle, as compared to their presurgical status. There was some relapse of nostril shape in width (10%), height (20%), and angle of columella (4.7%) at 1 year of age.     

Anterior segmental distraction of the hypoplastic maxilla by a tooth borne device: a study on the movement of the segment

The aim of this study is to determine the relative movement of the teeth and bone after premaxillary distraction with a tooth-borne device constructed in the authors’ centre. To evaluate the effects of this device on the anterior segment and teeth, the space formed between the anterior and posterior segments of the maxilla was measured on computerized tomography images from 10 patients. The average differences were 3.5 mm at the apex level, 5.5 mm at alveolar ridge level and 7.4 mm at crown level on the right side. On the left side, the average differences were 3.2, 5.2 and 7.1 mm, respectively. There were statistically significant differences between all these measurements (p < 0.05), but the difference between right and left sides was not statistically significant (p > 0.05). The ratio between the movements at apex and crown levels was 46%. These results showed that the tooth-borne distractor was able to distract the anterior segment of the maxilla but it also caused anchorage loss of the maxillary incisors.     

Desmoplastic fibroma of the maxilla

A case of desmoplastic fibroma of the right maxilla is reported. The lesion presented as a painless mass in the right posterior alveolar ridge of a 22-year-old white man. Histologically, the lesion was composed of interlacing fascicles of benign-appearing fibroblasts in a varying ground substance of collagenous and myxoid tissue. The lesion was not encapsulated histologically and was invading between bone trabeculae resulting in resorption of the bone. A review of the literature reveals that a total of 30 cases of desmoplastic fibroma of the jaws have been reported. All of the mandibular lesions except two were reported to have occurred in the left side, with the molar-ramus region favored. The case reported here is, to the best of our knowledge, the first reported case of desmoplastic fibroma occurring in the maxillary alveolar process.     

Gonial angle distortion in lateral head films: a methodologic study.

The distortion of the gonial angle in lateral roentgenographic head films was studied in skull material. The left and the right gonial angles were determined craniometrically and roentgenocephalometrically, and the observations were compared. Mean difference of 8.48 degrees and 5.15 degrees between the roentgenocephalometric and the craniometric registrations were found for the side closer to the film and the side farther away from it, respectively. For the intermediate gonial angle, the difference was 6.65 degrees. The differences were all statistically significant. It was demonstrated that they were mainly attributable to a systematic method error in the roentgenocephalometric method, involving a magnification of the gonial angles. The magnification was significantly larger on the side closer to the film than on the side farther away from it. A pronounced individual variation in gonial angle distortion was observed. For intermediate gonial angle it ranged between magnifications of 1.17 degrees and 17.54 degrees. The distortion is closely associated with the form of the mandible. It is largest in mandibles with a pronounced divergence of the two halves of the corpus and a pronounced upward convergence of the rami. It is smallest in mandibles with a modest divergence of the two halves of the corpus and a pronounced upward divergence of the rami. By some very special combinations of corpus divergence and ramus inclination, a correct reproduction may be obtained. No such cases were found in the sample studied, but there can hardly be any doubt that they exist. There is an association between corpus divergence and ramus inclination. Maximum magnifying effect of the forward-extending leg tends to coincide with the maximum magnifying effect of the upward-extending leg. Conversely, minimum magnifying effect of the forward-extending leg tends to coincide with a dimishing effect of the upward-extending leg. This is the clue to an understanding of the great individual variation in gonial angle distortion. Generally speaking, lateral head films do not permit reliable registrations of the gonial angle. At present no method is available for an exact assessment of the distortion in head films of the single living person.     

Comparison of the intercondylar distance and the interfacial width as used with the electronic pantograph.

The electronic pantograph (Pantronic) records mandibular movements and computes the articulator settings. The Pantronic pantograph does not determine the intercondylar distance but approximates it from the interfacial width at the condyles. An average distance of 12.5 mm is subtracted from each side to determine the intercondylar distance. This study recorded 45 patients' articulator intercondylar distances that had been set from a mechanical pantograph and they were compared with the Pantronic's approximation. The difference between the interfacial width and the actual intercondylar distance was 15.1 mm on the right side and 14.9 mm on the left side. A numerical value of 15.0 mm was statistically superior to the Pantronic's 12.5 mm in estimating the average distance between the intercondylar distance and the surface of the skin at the condyle. No statistically significant difference was found between the differences of interfacial width and intercondylar distance values for men and women (p greater than 0.05). The mean intercondylar distance was 56.5 mm on the right side and 56.7 mm on the left side. A statistically significant difference was found between the mean intercondylar distances of men and women (p less than 0.05).     

Histological and histomorphometrical comparative study of β-tricalcium phosphate block grafts and periosteal expansion osteogenesis for alveolar bone augmentation

This study evaluated local tissue reaction around the β-tricalcium phosphate (β-TCP) block and compared results with β-TCP block grafting and periosteal expansion osteogenesis (PEO). The mandibular premolars were extracted from five dogs and buccal corticotomy was performed. Narrow alveolar ridge models were created at 4 weeks. The β-TCP block graft, such as veneer graft, was used on the right side and PEO using β-TCP block on the left side. Changes of alveolar width, histological findings and histomorphometrical analysis were evaluated. There were no problems with materials at any of the sites at any time. In both groups, the width increased after surgery and results were stable 8 weeks after surgery. Newly formed bone tissue was observed inside the β-TCP block in both sides. Histological findings differed especially at the division between mandibular bone and β-TCP block. Histomorphometric analyses revealed that β-TCP had been absorbed (mean decrease 28%) and new bone had formed (mean increase 43%) at 8 weeks postoperatively on both sides. The β-TCP block worked as a space-maker under the soft tissue, including the periosteum, and acted as a substitute for original bone. This bone substitute was effective material for bone augmentation in both methods.     

Effects of topical administration of clodronate on alveolar bone resorption in rats with experimental periodontitis

BACKGROUND: We examined whether topical administration of a bisphosphonate clodronate could prevent alveolar bone loss in rats with experimental periodontitis. METHODS: On day 0, elastic rings were placed around the cervix of the right and left maxillary first molars (M1) to induce inflammatory periodontitis. Fifty microl of clodronate solution at a concentration of either 0 (0.9% NaCl), 20, 40, or 60 mM was injected into the subperiosteal palatal area adjacent to the interdental area between M1 and M2 on either the left or right (experimental) side on days 0, 2, 4, and 6. The contralateral side served as a control and received 0.9% NaCl solution without clodronate. The animals were sacrificed on day 7. RESULTS: Histological examination and determination of bone mineral density in the interdental alveolar bone area between M1 and M2 revealed that placement of an elastic ring caused severe vertical and horizontal bone resorption on the control side, while the topical administration of clodronate significantly prevented such alveolar bone loss. The number of osteoclasts on the experimental side was decreased compared with the control side. Furthermore, many of the osteoclasts on the experimental side were detached from the surface of the alveolar bone and had degenerated appearances, such as rounded shapes and a loss of polarity. CONCLUSIONS: These results suggest that topical administration of clodronate may be effective in preventing osteoclastic bone resorption in periodontitis.     

大鼠下颌切牙拔出后剩余牙槽嵴吸收模型的建立

目的:建立大鼠切牙拔除后剩余牙槽嵴吸收的实验动物模型并探讨其发生机制。方法:选用健康雄性Wistar大鼠30只,局麻下齐龈缘磨除右下颌切牙牙冠,每3天磨除1次,共3次,最后磨除后3d拔除右下颌切牙,术后0、1、2、4、8、12周分别处死大鼠。用软X线摄片测量大鼠下颌剩余牙槽嵴的长度和保存率,组织学方法评价大鼠下颌切牙拔牙窝的愈合情况。对18只健康雄性Wistar大鼠通过HE染色观察磨除牙冠后的不同时期牙周组织形态学改变。结果:牙槽嵴长度:4、8、12周拔牙侧与非拔牙侧相比明显降低(P<0.05);拔牙4周后牙槽嵴保存率明显降低。组织形态学:拔牙后2周,拔牙窝内可见新生骨,残存的血凝块减少;拔牙后4周骨改建活跃;拔牙后8周,拔牙窝内充满新生骨;拔牙后12周,新生骨和周围牙槽骨界限不清。牙冠磨除后,牙周组织出现水肿,主纤维束断裂,丧失功能排列,血窦增加,随时间改变逐渐加重。结论:可以采用拔除大鼠切牙的方法建立剩余牙槽嵴吸收的动物模型。     

Gonial angles and condylar and ramus height of the mandible in complete denture wearers—a panoramic radiograph study

summary It has been accepted that the shape of the mandibular base, and especially the gonial angle of the mandible, correlates with the function of the jaw closing muscles. The gonial angles of the mandible and condylar and ramus heights of 30 complete denture wearers (18 women, 12 men, mean age 61 years, range 42–74 years) coming for renewal of their dentures were measured using panoramic radiographs. The mean period of edentulousness was 26 years (range 10–53 years). No statistically significant difference was observed between the sexes in the the sizes of gonial angles and condylar and ramus heights. The right gonial angle was statistically significantly smaller than the left one and correlated negatively with the ramus height in both sides but positively with the increased EMG activity in the right masseter muscle. The size of the gonial angle and the condylar and ramus heights did not correlate with the age of the patients, edentulous period or alveolar ridge resorption.     

上颌全口义齿的加强结构对基托下黏膜应力分布的影响

目的：分析上颌全口义齿加强前后及不同的加强设计，对基托下黏膜应力分布的影响。方法：采用三维有限元法，建立无加强（BS），铸造结构加强BA，BD和BDr等4种上颌全口义齿三维有限元模型。设定P1，M1，PMc和PMe等4种垂直加载条件，加载力合计98N。对全口义齿基托下黏膜的应力分布进行分析。结果：在相同加载条件下，黏膜应力峰值表示为按BS，BA，BD，BDr的顺序依次减小。BDr基托下黏膜应力峰值最小，应力分布更均匀和广泛。结论：使用覆盖牙槽嵴顶及后堤区的铸造加强结构的上颌全口义齿能够使基托下黏膜应力分布更均匀和广泛，有利于保护基托下黏膜组织。