Maxillary expansion treatment using bone anchors: development and validation of a 3D finite element model

Objective: Develop a finite element (FE) model of a skull to perform biomechanical studies of maxillary expansion using bone anchors (BA).

Materials and methods: A skull model was developed and assigned material properties based on Hounsfield unit (HU) values of cone-beam computerized tomography (CBCT) images. A 3 mm diameter cylindrical BA was modelled and inserted in the palatal bone. A 4 mm transverse displacement was applied on the anchor. An evaluation on the effect on local stresses of BA implantation inclination angle was performed.

Results: Proper displacement results and strain–stress trends for the expansion process were present. Stress distribution patterns were similar as reported in the literature. No significant difference between BA inclination angles was found.

Conclusion: This work leads to a better understanding and prediction of craniofacial and maxillary bone remodelling during ME with BA treatments and is a first step towards the development of patient specific treatments.     

Stress distribution and displacement analysis during an intermaxillary disjunction--a three-dimensional FEM study of a human skull

The goal of this study was to contribute to an understanding of how much expansion force is needed during a maxillary expansion (ME) and where bony reaction takes place. A finite element (FE) model of a dry human male skull was generated from CT scans. The FE model, which consists of cortical and cancellous bone and teeth, was loaded with the same force magnitudes, directions and working points as in rapid maxillary expansion (RME). A three-dimensional finite element stress analysis (FESA) of the forces and displacement was performed. The highest stress was observed in the maxilla in the region where the forces were applied, and spreads more or less throughout almost the whole frontal skull structures. The displacement distribution which causes stress in the skull is highly dependant on the thickness of the bone and its structure. All areas with high compressive and tensile stress are exactly the regions which determine the maximal amount of force to be used during the maxillary expansion and should be examined in case of any complication during a patient's treatment. Regions with significant compressive and tensile stress are the regions observed to have an increase in cellular activity. Further simulations with a given displacement (0.5mm) showed that displacement simulations need extra caution otherwise they will lead to very high forces which are not realistic in an orthodontic treatment.     

In-vitro results of rapid maxillary expansion on adults compared with finite element simulations

This study was mainly performed to investigate the effects of high maxillary expansion forces on the skull with fresh and thiel-fixed human skulls. The maxillary suture was not weakened except in one experiment. This study compares the strain measured on the zygomatic process of the skull with the results of a finite element model generated for this purpose. An increasing transversal force was applied on the alveolar process (teeth) until rupture. Strain on the zygomatic process, maxilla displacement and the expanding forces were registered.The results of this study show linear material behaviour of the skull before rupture. The highest stress during the experiments and FE simulation was observed on the alveolar process.Conclusions of this study are the necessity of the existence of appropriate models and that female specimens seem to rupture at a lower force than male ones. Both male and female specimens show a similar linear behaviour in the force/strain curve within each gender group. The probability of maxillary suture opening in adults during ultra-rapid maxillary expansion with tooth anchorage is very low. Complications and unwanted rupture could occur.     

Osseous expansion of the cranial vault by craniotasis.

A study of cranial vault lengthening using a custom expandable fixation-distraction (craniotatic) appliance was performed in the young-adult rabbit model. Ten 24-week-old rabbits underwent circumferential suturectomy plus expansion (expanded group), 10 underwent circumferential suturectomy without expansion (sham control group), and 10 served as normal controls. The appliance was lengthened at a rate of 2.5 mm per week for 5 weeks. Serial lateral cephalometry, comparative dry-skull anthropometric measurements, and histologic examinations were performed. The expanded group demonstrated a significantly longer skull, cranial vault, anterior cranial base, posterior face, and orbit as compared with the control groups (p less than 0.05). Callus bone filled the distracted suturectomy and united the frontofacial complex to the posterior cranium. In conclusion, skull lengthening by distraction osteogenesis is possible in the rabbit model and offers a new technique for future investigation in the treatment of coronal synostosis.     

中国穿山甲和马来穿山甲头骨量度的测定及比较

全球共有7种穿山甲。本文报道的是中国穿山甲和马来穿山甲的头骨形态学资料,涉及头骨特征描述和一些形态学指标测定。被测定的指标主要有颅全长、基底长、腭长、眶间宽、后头宽、鼻骨长、鼻骨宽、脑颅高、听泡长和下颌长,并且在这两个物种之间进行了比较。结果表明,(1)这两个物种头骨形态十分相似,但马来穿山甲头骨细长,听泡长小于10mm(n=12),鼻骨狭长,前后部宽窄相似,两鼻骨外侧缘内凹或平行,鼻骨宽长之比值小于0 3000(0 2025～0 2811,n=12);而中国穿山甲头骨较粗短,听泡长大于11mm(n=46),鼻骨宽短,后部较前端宽,外侧缘外凸,鼻骨宽长之比值大于0 3000(0 3154～0 5325,n=33)。这些异同之处,可以作为区分这两个物种的依据。(2)中国穿山甲华南亚种与海南亚种头骨各变量之间的差异不显著(P>0 05),用颅全长是否大于83mm来区分这两个亚种不能成立,但海南亚种头骨上颌骨的颧突和鳞骨的颧突通常越过眶颞窝完全相接触,如果不是这样,则在它们之间有一个小的骨质棒状结构将它们连接起来。     

The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation

doi: 10.1111/j.1741‐2358.2011.00587.x The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation Objective: This study evaluated the influence of the bimaxillary flask (BMF) and two different investing materials on first molar inclination in dentures processed by microwave irradiation. Background: The BMF may minimise tooth displacement, saving time and improving occlusion. Methods and materials: Forty pairs of dentures were randomised into four groups: stone wall in monomaxillary flask; silicone wall in BMF; stone wall in BMF; acrylic resin retentions and silicone in BMF. Dentures were processed by microwave irradiation. Two referential points were established on tooth surface. A microscope and a digital pachymeter were used to measure the distance between these points, and the angles α (right maxillary molar), β (left maxillary molar), α′ (right mandibular molar) and β′ (left mandibular molar) were calculated by the law of cosines. Data were submitted to Kruskal–Wallis (5% significance). Results: No difference was observed among the groups (p > 0.05). In the intra‐group analysis, α was significantly different for groups I, II and III; α′, for groups II and IV; β, for all groups; β′, for groups III and IV. Conclusion: First molar inclination was similar for monomaxillary and BMFs. The use of stone or silicone as investing materials presented the same effect on tooth inclination.     

The effect of total maxillary advancement on facial growth.

The effect of total maxillary advancement on the growing skull was examined in 25 pigs, subjected to facial operations of varied severity at the age of 5 weeks (elevation of periosteum, simple osteotomy, and osteotomy immobilized by wire fixation, with or without bone grafts) and in controls. When the animals were killed 8 months later, the body weight had increased tenfold and the skull size had doubled. In 5 pigs whose maxillae were advanced 10 mm by bone grafts, the relative increase in length was not maintained. The overall skull length showed no difference from the control measurements. The extent of the growth in the area adjacent to the osteotomy was less than in the controls, but the same as in pigs subjected to periosteal elevation only. Scattered areas of bone damage were seen with no consistent pattern. Incision of the periosteum over the frontal bone decreased the local blood supply, increased the adherence of the periosteum to the bone, and affected bone growth locally.     

新生儿唇腭裂术前矫治方法与技术的临床探讨

目的:评价新生儿唇腭裂术前进行鼻-牙槽突-腭畸形矫治方法的疗效。方法:对28例单双侧唇腭裂新生儿进行术前鼻-牙槽突-腭畸形矫治治疗,在面部确定基点,利用数码相机拍射照片,通过image-Pro Plus5.1软件测量相关距离及角度,测量治疗前后的鼻小柱倾斜度、鼻小柱长度、鼻孔宽度和鼻孔高度。治疗前后取上颌石膏模型进行牙槽骨裂隙宽度的测量,比较矫治治疗前后腭部裂隙最大处及牙槽突裂隙的变化。结果:鼻小柱倾斜度平均减小27.11°,鼻孔宽度平均减小4.39 mm(单)或5.29 mm(双),鼻孔高度平均增加2.56 mm(单)或3.57 mm(双),牙槽突裂隙平均减少3.18 mm,腭部裂隙最大处平均减少5.77 mm。治疗前后的各项差异均有统计学意义(P0.05),鼻塌陷畸形程度也得到显著改善。结论:术前进行鼻-牙槽突-腭畸形矫治治疗可为唇腭裂患者手术治疗创造有利条件,提高其整复效果。     

Some dental traits of Diaguitas Indian skulls

Dental characteristics were studied on 60 skulls that belong to a population of Diaguitas Indians of approximately the Tenth Century. Mesiodistal crown diameters of permanent teeth were as follows: central incisors (8.77 mm), lateral incisors (7.23 mm), canines (8.40 mm), first maxillary molars (10.77 mm), second maxillary molars (10.71 mm), first mandibular molars (11.13 mm), and second mandibular molars (10.17 mm). Also determined was the frequency of shovel shaped incisors (80.30%), groove and cusp patterns of mandibular molars (Y5 73.40%), groove and cusp patterns of maxillary molars (H4 87.25%), and mesiopalatal version of maxillary incisors (66.20%). No skull showed Carabelli's cusp. The findings were compared with those for different populations past and living. The results suggest that the affiliation of the population analyzed was mongoloid.     

Sutural expansion osteogenesis for management of the bony-tissue defect in cleft palate repair: experimental studies in dogs

A series of experimental studies on sutural expansion osteogenesis for management of the bony-tissue defect in cleft palate repair was performed between 1995 and 1997. Forty-five young dogs in weaning were used in four experiments that were divided into two parts. Part I probed the possibility of closing the surgically constructed hard palate cleft not only with mucoperiosteum but also with bony tissue by the technique of sutural expansion of lateral palatine sutures. Part II explored the possibility of pushing the palatine bone posteriorly and advancing the maxillary segment anteriorly by transverse palatine suture expansion. In Part I, a ring-shaped suture expander made of nickel-titanium shape memory alloy was used to expand the lateral suture of palatine bones. Expansion forces of 200 G, 360 G, and 480 G were used for the first experiment. A force of 360 G was chosen for two other experiments; this force is equivalent to the distraction rate of 0.5 mm per day of a jackscrew device. The ring-shaped suture expander was opened and its two feet were fixed in the medial sides of residual horizontal plates of the palatine bones immediately after a hard palate cleft was constructed surgically under endotracheal general anesthesia. At the eighth postoperative day, under the traction of 360 G, the two sides of the 8-mm-wide hard palate cleft were brought into contact with each other, and 8 or 9 days later the closed palatal cleft had healed completely with mucosal tissue. This experiment was repeated twice and yielded the same results. Sutural expansion osteogenesis was evaluated physically, fluorescently, histologically, and ultrastructurally to examine the deposition of the regenerated bone in the suture areas. Additionally, the influence of sutural expansion osteogenesis of the palatal bones on other facial bones was also studied cephalometrically. In Part II, a bow-shaped suture expander made of nickel-titanium shape memory alloy was applied to expand either the left or the right side of the transverse palatal suture of each of the experimental dogs. At the postoperative week 4 to 6, the maxillary segment was moved forward 5 to 6 mm on the expanded side, and the palatal bone was pushed backward 5 mm. The changes of bone position were assessed radiographically and cephalometrically. Tissue response of circum-maxillary sutures was examined histologically. These experiments led to the following conclusions: (1) Bony closure of the surgically constructed hard palate cleft with a ring-shaped suture expander made of nickel-titanium shape memory alloy is possible. (2) Anterior advancement of the maxillary segment and posterior lengthening of the hard palate using a bow-shaped suture expander made of nickel-titanium shape memory alloy applied at the palatomaxillary suture (transverse palatal suture) of the hard palate are also possible. Thus, in humans, a new approach for cleft palate repair may be a worthwhile investigation.     

河南一尤因他兽头骨化石

大型尤因他兽类在北美曾发现过许多头骨和头后骨骼化石。但在亚洲,以往虽有这类动物化石的报道,因材料零星且不完整,而不能确定。河南尤因他兽头骨的发现可以肯定大型尤因他兽类在亚洲的分布,同时进一步证实了在中始新世亚洲与北美大陆的哺乳类也有交往。从这里记述的意外尤因他兽来看,卢氏组下部的时代可认为是中始新世。     

Humidity as a source of measurement error in osteometrics

A simple experiment was conducted to test the hypothesis that variation in humidity causes expansion of bone and, thereby, affects measurements of dried, preserved skulls. The experiment consisted of subjecting ten macaque skulls to increased humidity for 24 hours. Measurements of nine skull dimensions taken immediately before and after humidification revealed a statistically significant treatment effect of increased skull size with increased humidity. The length of the molar tooth row increased by about 0.1 mm (0.50%) while the greatest length of the skull increased by about 0.9 mm (0.57%). The specimens returned to their original dimensions within 1-2 days after being removed from the humidity chamber. These results confirm the impression gained by the practical experience of measuring museum specimens in different locations and environments. It appears that bony changes associated with humidity differences represent a real, though minor, source of measurement error in osteometrics.     

Three-dimensional model of the human craniofacial skeleton: method and preliminary results using finite element analysis

The purpose of this study was to develop a three-dimensional finite element model of the craniofacial skeleton using a dry human skull. The model consisted of 2918 nodes and 1776 solid elements, and was used to investigate the biomechanical effect of a distally directed orthopaedic force on the craniofacial complex. The force was applied at the level of the maxillary first molar. The results indicated that in response to the force system applied: the nasomaxillary complex displaces in a backward and downward direction and rotates in clockwise sense; the nasomaxillary complex, including the zygomatic bone, experiences high stress levels in comparison with those at the remaining bones; the stress distribution in the maxillary basal bone area is relatively uniform; and the stress distribution across the opposing surface of the bony margins of the sutures is non-uniform.     

Skeletal stability after Le Fort I maxillary advancement in patients with unilateral cleft lip and palate

Outcomes in 30 adults and adolescents judged skeletally mature who had unilateral cleft lip and palate and underwent Le Fort I advancement were investigated to determine amount and timing of relapse, correlation between advancement and relapse, effect of performing multiple jaw procedures, effect of different types of bone grafts, effect of pharyngoplasty in place at the time of osteotomy, and effectiveness of various methods of internal fixation. Tracings of preoperative and serial postoperative lateral cephalograms were digitized to calculate horizontal and vertical maxillary changes. No significant differences in outcome was seen between patients who had maxillary surgery alone and those who had operations on both jaws, nor did the outcome vary significantly with the type of autogenous bone graft used or the segmentalization of the Le Fort osteotomy. Mean "effective" advancement was greater immediately and 2 years after surgery in those patients who did not have a pharyngoplasty in place before the operation. Advancement also was greater immediately and after 2 years in the miniplate fixation group than in patients with direct-wire fixation. Mean downward (vertical) displacement was 2.6 mm with a relapse of 1.4 mm after 2 years. Amounts of relapse and of advancement or displacement did not correlate significantly.     

Compressive strains and displacement in a partially dentate lower jaw rehabilitated with two different treatment modalities

doi: 10.1111/j.1741‐2358.2011.00572.x Compressive strains and displacement in a partially dentate lower jaw rehabilitated with two different treatment modalities Background: Understanding of the biomechanical consequences of the stresses generated to the supporting bone during occlusal loading is significant for improving the design and clinical planning process in partial edentulism therapy. Objective: The aim of this study was to analyse the distribution of strain and displacement on the partially dentate lower jaw rehabilitated with an partial denture (RPD) and to compare it to the strain and displacement distribution on a partially dentate lower jaw rehabilitated with a cantilever fixed partial denture (FPD). Material and methods: The experimental models were a partially dentate mandible with full‐arch PFM crowns and RPD and a partially dentate mandible rehabilitated with a full‐arch cantilever FPD. Strains and displacement were measured using the Digital Image Correlation Method. Results: Displacement values of the first experimental model ranged from 0.31 to 0.54 mm with strains from 1.35 to 2.34%. Analysis of the second experimental model results showed displacement values from 0 to 0.34 mm, while strains were in the range of 0–1.40%. Conclusion: Higher displacements and strains of bone tissue were observed below the RPD, especially in the region of the distal abutment and distal portion of the free‐end saddle. Strains within bone and the bone‐denture contact area were mostly influenced by the teeth and denture vertical displacement.     

Treatment of craniomaxillofacial fibrous dysplasia: how early and how extensive?

Twenty-eight craniomaxillofacial fibrous dysplasia patients were treated as early as the symptoms occurred. The principles of surgical treatment were based on the zones of involvement: total excision of dysplastic bone of fronto-orbital, zygoma, and upper maxillary origin (zone 1) and bone reconstruction primarily; conservative excision on hair-bearing skull (zone 2), central cranial base (zone 3), and tooth-bearing bones (zone 4); and optic canal decompression on patients with orbital dysplasia and decreasing visual acuity. Patients were followed for 1 to 11 years (average 5.3 years). No recurrence or invasion of the fibrous dysplasia into the grafted bone was seen. One patient had orthognathic maxillary osteotomy on the reconstructed maxilla 6 years after initial reconstruction. Five of 19 patients with alveolar dysplasia had a recurrence and were reshaped. One patient had mandibular sagittal osteotomies to set back the prognathic, fibrous dysplasic mandible after three attempts at conservative shaving. Another patient with mandibular fibrous dysplasia had recurrence with pain and a hemimandibulectomy with successful immediate free vascularized iliac bone graft reconstruction.     

A sexually dimorphic basal anal-fin ray expansion in the weakly discharging electric fish Gnathonemus petersii

Male Gnathonemus petersii (Mormyridae) exhibit two structural, sexually dimorphic characters: anal-fin ray bone expansion and an indentation of the posterior ventral body wall (formerly described as anal-fin indentation). Females lack this bone expansion, but may show a slight indentation. Morphometric data on both characters were obtained from radiographs of 414 fish (males and females) ranging in size from 60 to 276 mm L_s. Both body wall indentation and bone expansion began to develop in males of about 120 mm L_s. At 160–180 mm, the sex ratio of fish with expansion to fish without expansion was 50 : 50. Androgens seem to affect the expression of both these sexual dimorphisms. Bone expansion may provide increased bone surface for muscle attachment and thus facilitate the anal-fin reflex during courtship behaviour.     

扁颅鼩鼱 (Sorex roboratus) 在中国分布的证实

正扁颅鼩鼱(Sorex roboratus)隶属于食虫目(INSECTIVORA)鼩鼱科(Soricidae)鼩鼱属(Sorex),又称阿尔泰鼩鼱或西伯利亚鼩鼱,从前称S.vir,但是S.roboratus有优先权(Hoffmann,1985)。Wilson和Reeder(2005)认为其分布区域从俄罗斯东部的鄂毕河到乌苏里江,南部到阿尔泰山脉、蒙古北部和krai滨海边疆区。Hoffmann(1987)把扁颅鼩鼱作为可能分布于中国的两个鼩鼱类物种之一列于文中,王应祥(2003)在《中     

贵州省发现翼手目动物——高颅鼠耳蝠

2015年7~9月在贵州省兴仁县、平坝县和兴义市的五屯镇及敬南镇捕获鼠耳蝠33只,鉴定为高颅鼠耳蝠(Myotis siligorensis),为贵州省新纪录物种。标本保存于贵州师范大学生命科学学院生态实验室。主要特征:体型较小,前臂长(36.03±1.50)mm(32.66~38.98 mm,n=33);耳狭长;耳屏直而细长;第Ⅲ掌骨最长,第Ⅴ掌骨最短;阴茎长(4.52±0.84)mm(2.85~5.75 mm,n=21);头骨狭长,颅骨凸显;颅全长(13.87±0.74)mm(13.00~14.88 mm,n=8),颅高(6.36±0.24)mm(6.03~6.74 mm,n=8);听泡较小;矢状脊细弱;上颌第1、2门齿向中央倾斜,上颌第1门齿有1个主尖和1个附尖;上颌第2门齿较第1门齿小,且与犬齿分离;上颌第2前臼齿(P3)位于齿列中。基于Cyt b基因(1 141 bp)序列进行的分子系统学分析显示,此次捕获鼠耳蝠物种与高颅鼠耳蝠聚在一起,二者遗传距离最近(仅为0.03),进一步确认所采集物种为高颅鼠耳蝠。