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BACKGROUND: Due to dentition defect, dentition loss, periodontal disease, trauma and tumor, many patients have to face insufficient buccal-lingual mandibular width. At present, there is no consistent conclusion in suitable peri-implant buccal-lingual mandibular width. OBJECTIVE: To investigate the stress of implant-bone interface with three-dimensional finite element method, in order to evaluate buccal-lingual mandibular width suitable for implants. METHODS: Classes Ⅰ and Ⅲ mandible implant models (the buccal-lingual width of implant neck region was 1, 1.5, 2, 2.5, 3 and 3.5 mm) were loaded with 200 N forces vertical y and at 60° oblique. Then, the stress and strain in the implant-bone interfacial were analyzed. RESULTS AND CONCLUSION: Almost 2 mm or more than 2 mm of mandible bone width could result in good stress distribution in implant-bone interface. The stress distribution of oblique loading was much greater than that of vertical loading. Proper quantity of peri-implant mandibular width is good for stress distribution in implant-bone interface. In the clinical treatment, the oblique loading should be avoided or reduced.
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BACKGROUND: Icari n as one of the main components of Epimedium has an inhibitory effect on osteoclasts.. OBJECTIVE: To further investigate the influence of icariin on the root absorption of the maxil ary first molar at mesial part during orthodontic treatment in rats. METHODS: Orthodontic root resorption models were established in the left maxil a of rats. Local injection of 200 mg/kg icari n (icari n group) or normal saline (positive control group) was administrated into the left first molar buccal periosteum. The right maxil a of rats served as negative control group that was treated with neither appliance nor drug injection. The mesial distance between bilateral first molars and the contralateral maxil ary incisor was measured before and after the appliance was placed. Mesial surface of the mesial root of bilateral maxil ary first molars was observed using scanning electron microscope. RESULTS AND CONCLUSION: Mesial movement of the maxil ary molars in the icari n group was significantly less than that in the positive control group (P < 0.05). Under the scanning electron microscope, smal absorption lacunae were scattered in the icari n group, while the positive control group showed a large amount of absorption lacunae and they were interconnected into a sheet, showing a stark contrast with the smooth root surface of the negative control group. It is indicated that icari n can inhibit root resorption caused by orthodontic treatment, while reducing the amount of mesial movement of the molar under corrective force.
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BACKGROUND: Rapid expansion of the dental arch is an effective way to rapidly expanse the jaw. Compared with rapid expansion, the slow expansion has higher stability and less recurrence, but the reports on the long-term stability of quad helix expansion are rare. OBJECTIVE: To retrospectively analyze the clinical effect of quad helix expansion in orthodontics. METHODS: Twenty-two subjects with dental arch stenosis in mixed dentition and early permanent dentition who experienced an expansion of at least 3 mm with quad helix appliance were selected for this study. Plaster dental casts and posteroanterior radiographs were evaluated at the beginning of the treatment (T1), at the completion of phase I quad helix expansion or ful treatment (T2), and approximately 2 years fol owing the completion of treatment (T3). The distance between two first molars was measured on the model. J point was drawn on the posteroanterior radiograph in order to measure the distance between the bilateral base bones and the molar inclination, as wel as to evaluate the corrective and orthopedic effects of dental arch expansion. RESULTS AND CONCLUSION: Compared with that before expansion, the first permanent molar inclination and the distance between base bones on two sides were significant increased after quad helix expansion; there were no significant differences in the distance between two first permanent molars, first permanent molar inclination and the distance between bilateral base bones on two sides when compared after quad helix expansion and after 2-year fol ow-up (P > 0.05). The results indicate that the long-term effect of quad helix expansion is stable with orthopedic effect.
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BACKGROUND: Dlx gene family is highly expressed in the cranial neural crest cells, and regulates the cranial neural crest cel migration and differentiation. OBJECTIVE: To review the mechanism that the highly-expressed Dlx genes mediate the cranial neural crest cel migration and differentiation. METHODS: An online search of CNKI and Medline databases was performed for articles published before 2013 using keywords of “cranial neural crest cells, migration of cranial neural crest cells, Dlx, Dlx overexpression, Fgf, chodrogenesis, osteogenesis” in Chinese and English, respectively. Relevant articles were summarized from three aspects: the migration of cranial neural crest cells, Dlx over-expression’s impact on the migration of cranial neural crest cells, interaction between the environment and Dlx genes. A total of 63 articles were included. According to inclusion criteria, 43 articles were retained at last. RESULTS AND CONCLUSION: Dlx abnormal-expression wil lead to cel -cel adhesion. Dlx over-expression wil induce most of the cranial neural crest cells aggregate and migrate to a wrong place, and result in skeletal dysmorphology. Dlx over-expression wil also lead to ectopic chondrogenesis, and the interaction between cel factors can be the possible reason for this.
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10.3969/j.issn.2095-4344.2013.24.011
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BACKGROUND:With the development of modern orthodontics, to invent an efficient appliance is the focus in recent studies. Transmission straight wire appliance was born on this background. This appliance can accelerate occlusion and shorten treatment duration. The relationship between distal width and angulation of gable bends of main arch wire needs to study in depth. OBJECTIVE:To establish three-dimensional finite element model of transmission straight wire appliance with better biological and mechanical similarity, and to obtain the relationship between distal width and angulation of gable bend of main arch wire. METHODS:By using scanning of spiral CT with 64 rows, the sectional image data in DICOM format of maxil ary dentition and maxil ae of the volunteers (Class Ⅱ, division 1) were obtained. With the help of Ansys workbench 13.0, Mimics 10.01, Unigraphics NX and Geomagic Studio 8.0 softwares, the three-dimensional finite element model including transmission straight wire appliance, bend, Australian Orthodontic Wire, maxil ae, maxil ary tooth and periodontal ligament was established in Windows XP Service Pack 3 system. RESULTS AND CONCLUSION:A three-dimensional finite element model of transmission straight wire appliance was established, which consisted of 250 929 elements and 657 766 nodes. Furthermore, three-dimensional finite element model had higher geometric similarity and mechanical similarity, as wel as the advantages of adding or subtracting components according to the requirement of the research. The model was conductive to analyze the mechanical system of transmission straight wire appliance and guide the clinical application and appliance modification.
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BACKGROUND:The stress distribution in the periodontal ligament of bending root can provide reference for the size and manner of force in orthodontic treatment. On this account, it can optimize the design of orthodontic force. OBJECTIVE:To analyze the stress distribution of root and periodontal ligament in the bending roots of the maxil ary first molar under different orthodontic forces. METHODS:The maxil ary first molars with normal roots and bending roots were selected, and then the finite element models of maxil ary first molars and periodontal ligaments were established through CT scan and Workbench 11.0 finite element analysis software. The models were loaded with six different methods to analyze the stress distribution. RESULTS AND CONCLUSION:The stress distribution of bending root was mainly concentrated in the tooth neck, fol owed by the apex. During the overal tooth movement, the stress was smal est on the root, periodontal ligament and alveolar bone. Correction of bending roots needs more accurate positioning and traction.
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BACKGROUND:Bone mass deficiency is common during implantation in the maxil ary posterior region. Some patients do not want to accept extra surgery for increasing bone because of surgical trauma or medical expenses. Technology of the tilted implant has been proposed, but it has not been recognized and has a lack of relevant evidence. OBJECTIVE:To investigate the stress distribution of per-implant bone which is subjected to different loading conditions when the different abutment angulations are applied, and to analyze the safety factor of different implants to verify the feasibility of the tilted implant in the maxil ary posterior region. METHODS:The finite element models of the different angulate abutments were established in commercial software packages. The safety factor of implant in the same power load was observed, and stress and strain condition of the implant and the surrounding bone was also observed. RESULTS AND CONCLUSION:With the increased abutment angulation, the maximum strain of pre-implant bone was significantly increased, and the safety factor of implant decreased gradual y. Thus, the tilted implant is not recommended in the maxil ary posterior region.
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BACKGROUND:Individuals with different vertical facial types have different chin morphologies. For the individuals with different vertical facial types, what is the most beautiful chin morphology? OBJECTIVE:To evaluate the effects of vertical facial types and chin morphology on facial profile attractiveness. METHODS:Three beautiful females were selected, including one with high mandibular angle, one with average angle and one with low angle. Their facial profile photographs were taken. A series of new pictures were generated by the smal scale (2 mm per unit) modification of soft tissue chin in the sagittal direction and vertical direction. Raters consisting of 17 orthodontists and 35 laypersons were selected for aesthetic ratings, in order to evaluate the facial profile attractiveness of the individuals with different vertical facial types. RESULTS AND CONCLUSION:There was no esthetic difference of vertical change in female with high angle;while slightly protrude chin was perceived to be more beautiful than retruded chin. For the female with average angle, lower chin was more attractive than higher chin;slightly protruded chin was beautiful than excessive protruded chin and retruded chin. For the individual with low angle, higher chin was preferred by raters;slightly protruded chin was more beautiful than excessive protruded chin and retruded chin.The results indicate that the effects of vertical facial types and chin morphology to facial profile attractiveness are different. In clinical orthodontic, vertical facial types should be taking into consideration to change the chin morphology of the patents, in order to obtain better profile attractiveness.
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BACKGROUND:Posterior arch length deficiency is closely related to the formation and development of malocclusion. OBJECTIVE:To measure the posterior arch length in individual normal occlusions of adults in Lanzhou. METHODS:A total of 102 current col ege students with individual normal occlusions, with a mean age of (19.33±2.67) years (range 18-24 years), including 47 males and 55 females from Gansu Province, were chosen to take lateral cephalograms. Al research objects were divided into three groups according to mandibular plane angle:high angle group (Frankfort mandibular-plane angle>32°), low angle group (Frankfort mandibular-plane angleRESULTS AND CONCLUSION:Posterior arch length of maxil ary arch was slightly longer in male group than that in female group, and the difference was not significant (P>0.05). The posterior arch length of mandibular arch was slightly longer in male group than that in female group, but the difference was no significant (P>0.05). Comparison between groups revealed that the posterior arch length of low angle mandibular arch was significantly longer than that of high angle mandibular arch in male group, and the difference was significant (P<0.05). The results indicate that the gender wil not influence the development of posterior arch length. Different vertical facial types and different genders have different posterior arch length in individual normal occlusions of adults