磁性附着体焊接式衔铁在下颌全口覆盖义齿中的应用

目的 以铸接式衔铁为对照,探讨焊接式衔铁对下颌全口覆盖义齿口内磁性固位力的影响。方法 以Magfit磁性附着体作为固位装置,对9名采用焊接式衔铁和铸接式衔铁的患者分别进行下颌磁性附着体全口覆盖义齿修复。测定同一患者粘固磁体前、后义齿前部垂直向固位力。结果 两组在粘固磁体后义齿固位力均有明显增加。两组在义齿前部固位力增加值分别为414.7±218.09 g,322.2±318.30 g。结论 在下颌全口覆盖义齿中焊接式衔铁对于提高义齿的固位力具有重要的应用前景。     

激光焊接式衔铁与铸接式衔铁的性能比较

目的 :比较不同处理方式对衔铁性能的影响 ,为临床应用磁性附着体提供参考。方法 :Z 3型磁性附着体 18只随机分为 3组。以钴铬合金作为覆盖牙根的支撑板根帽合金高温铸接衔铁 1组 ,Nd :YAG激光焊接衔铁 1组 ,另 1组衔铁不作处理。利用万能拉伸试验机测试 3组磁性附着体的固位力 ,采用粗糙度仪测量 3组衔铁表面光洁度 ,并分别进行比较。结果 :应用激光焊接式衔铁与应用铸接式衔铁的磁性附着体固位力无差别 ,但比衔铁未作处理的磁性附着体的固位力略小。铸接式衔铁表面在粗糙度仪下可见点状缺陷 ,表面光洁度低于激光焊接式衔铁表面光洁度。结论 :采用激光焊接与铸接方式制作钉帽衔铁能够满足临床应用磁性附着体要求     

Magfit磁性附着体铸接式和焊接式衔铁显微结构及热影响区的研究

目的　比较铸接式和焊接式衔铁的表面及内部显微结构,为临床应用提供可靠的实验依据。方法　采用激光焊接技术制作焊接式磁性附着体衔铁试件6个,采用铸造技术制作铸接式衔铁试件5个,比较焊接式、铸接式衔铁试件和成品衔铁试件的表面形貌、金相结构及化学元素组成。结果　焊接式衔铁基本保持成品衔铁的表面光洁度和内部结构,热影响区极小,熔焊区有明显的元素扩散;铸接式衔铁表面粗糙,氧化层形成,内部结构改变,基体金属与衔铁间存在熔合带但元素扩散有限。结论　焊接较铸接对衔铁表面及内部结构影响小。     

磁性覆盖义齿根面结构常用制作方法及比较

衔铁与根面结构的选择及制作直接关系到磁性附着体义齿的修复效果。该文总结了目前衔铁根面结构的类型,包括预成桩核型、铸接式、激光焊接式及铸造式衔铁等,并比较了各类衔铁的制作方法和特点。     

表面磨耗对磁性附着体固位力的影响

目的:探讨磁性附着体表面磨耗与其磁性固位力之间的关系。方法:将MagfitDX400型磁性附着体衔铁及磁体分别固定于0.9×0.9×1.5cm的长方体自凝树脂试件中,共制作10对试件。将试件固定于滑动摩擦仪上,使磁体和衔铁做相对滑动运动,滑动距离为5mm,垂直加载5kg,滑动速度为60次/min。分别于以下阶段测试磁性附着体的垂直向固位力:1)摩擦运动前;2)滑动摩擦30,000次后;3)滑动摩擦50,000次后;4)滑动摩擦90,000次后。用显微镜观察滑动摩擦90,000次后的附着体表面形态。结果:10对附着体在滑动摩擦30,000次、50,000次和90,000次后的固位力降低的平均值分别为0.016N,0.003N和-0.008N,统计学分析显示,摩擦运动前后的固位力差异无统计学意义。显微镜下,滑动摩擦90,000次后的附着体表面可见明显磨耗。结论:表面磨耗对MagfitDX400型磁性附着体的垂直向固位力无显著性影响。     

衔铁可卸式磁性附着体的研制及对MRI影响的对比研究

目的：解决磁性附着体应用对MRI的影响。方法：开发衔铁可卸式磁性附着体，比较几种形式衔铁对MRI的影响程度及不同MRI扫描地钛片所造成的伪影大小。结果：（1）几种表式衔铁对MRI的影响由大到小依次为：预成钉帽状衔铁、钴铬合金铸接的衔铁，贵金属合金铸接的衔铁，钛 桩可卸式衔铁，钛桩（拆卸盘状衔铁及中心螺丝后）。（2）可卸式衔铁拆下盘状衔铁及中心螺丝后，钛桩对MRI影像几乎没有影响。（3）标准SE序列拍摄钛片时所造伪影最小。结论：衔铁可卸式磁性附着体解决了MRI的伪影问题。尤其适用于头颅及颜面部肿瘤切除后需要长期追踪观察的患者。     

激光焊接技术改进对衔铁焊接质量影响的实验研究

目的:探讨激光焊接技术的改进对磁性附着体衔铁与基桩焊接质量的影响,为临床应用提供实验依据.方法:采用Nd:YAC激光点焊机,以牙科高熔钴铬合金为基体金属对W600型磁性附着体成品衔铁进行焊接.试件分3组,分别作焊接面坡口和无坡口的设计以及不同焊接参数的设置.对焊接后3组试件的表面、显微结构、纵剖面等进行观察,比较焊接质量.结果:坡口组焊接深达全层,焊接缺陷较少;无坡口组焊接深度较浅.3组试件均未发现明显的热影响区以及过高显微硬度的淬硬组织.结论:焊接面的坡口设计,增加了焊接深度,提高了焊接质量.本实验条件下所增加的激光强度有利于焊接质量的提高.     

3种不同金属铸接式衔铁磁力差异的比较

目的:分别对金合金、镍铬合金及纯钛3种金属铸接式衔铁,进行磁力测试,比较3种金属衔铁磁力的差异。方法:采用金合金、镍铬合金、纯钛3种金属为材料,分为3组,每组4件样本,与Magdisc500成品衔铁包埋铸造,制作根面结构。通过拉伸实验测试附着体磁引力大小并进行方差分析。结果:金合金组磁引力均值为4.84N,镍铬合金组均值为4.61N,纯钛组均值为4.12N。方差分析显示:3组两两间均存在显著差异(P<0.01)。结论:采用3种金属,通过铸接法制作的衔铁,其磁力均有一定程度下降,金合金组磁力下降最小。     

Magfit磁性附着体下颌全口覆盖义齿的固位力测定

目的　评价Magfit磁性附着体下颌全口覆盖义齿的口内固位力及附着体分布与义齿固位力间的关系。方法　以Magfit EX600、MD800磁性附着体作为固位装置,选择5名患者制作下颌全口覆盖义齿,采用电阻应变式修复体固位力测试仪测试粘固磁体前后义齿前、中、后3点垂直向及前斜上方60°的固位力。结果　粘固磁体后义齿固位力显著大于粘固磁体前(P<0·05),义齿不同部位固位力间无显著性差异(P>0·05),垂直向固位力大于前斜上方60°的固位力(P<0·025)。结论　磁性附着体可显著改善下颌全口覆盖义齿的固位,附着体位置分布影响义齿的固位力。     

Magfit磁性附着体在全口义齿修复中的应用

评价以Magfit磁性附着体改善全口覆盖义齿固位的远期效果。方法：采用铸接法设置报面伤铁,并对应用Magfit磁性附着体的长期效果,如义齿的固位、稳定状态,以及义齿应用后出现的问题进行16～38月的随访观察。结果：①设置2只以上MagfitEX600或设置3只以上MagfitEX400磁性附着体即可使全口覆盖义齿获得保证行使各种口腔功能所需的长期稳定的固位力;②铸接式衔铁较粘接式衔铁有更好的密合性,可有效地防止继发龋;③Co－Cr合金可以被用于待接式衔铁的制作;④应用MagfitEX系列磁性附着体的全口覆盖义齿戴用后并发症发生率较低。结论：Magfit磁性附着体,能有效改善全口覆盖义齿的固位,并发症少,具有良好的远期效果。     

Comparative study of the surface characteristics, microstructure, and magnetic retentive forces of laser-welded dowel-keepers and cast dowel-keepers for use with magnetic attachments

STATEMENT OF PROBLEM: Information regarding the merits and problems associated with connecting a keeper to a dowel and coping using a laser welding technique has not been explored extensively in the dental literature. PURPOSE: This in vitro study compared the surface characteristics, microstructure, and magnetic retentive forces for a dowel and coping-keeper mechanism fabricated using a laser welding process and a cast-to casting technique. MATERIAL AND METHODS: Five cast-to and 6 laser-welded dowel and coping-keeper specimens were tested. Using 5 freestanding keepers as the control group, the surface characteristics and microstructures of the specimens were examined by means of stereomicroscopy, metallographic microscopy, and scanning electron microscopy (SEM). Energy-dispersive spectroscopic (EDS) microanalysis with SEM provided elemental concentration information for the test specimens. The vertical magnetic retentive forces (N) of the 3 groups were measured using a universal testing machine. The results were statistically compared using 1-way analysis of variance and the Newman-Keuls multiple range test (alpha =.05). RESULTS: The laser-welded dowel-keeper generally maintained its original surface smoothness as well as the original microstructure. Elements diffused readily through the fusion zone. The surface of the cast dowel-keeper became rough with the formation of an oxide layer, the microstructure changed, and there was only limited elemental diffusion in the fusion zone. The average vertical magnetic retentive force of the laser-welded group, the cast group, and the control group were 4.2 +/- 0.2 N, 3.8 +/- 0.3 N, and 5.6 +/- 0.3 N, respectively. Statistically significant differences in vertical magnetic retentive force were found between the control group and both the laser-welded and cast groups (P <.01). Compared with the cast dowel-keepers, the average vertical magnetic retentive force of the laser-welded dowel-keepers was significantly higher (P <.05). CONCLUSION: The laser welding technique had less influence on the surface characteristics, the microstructure, and the magnetic retentive forces of keepers relative to techniques that incorporate a keeper at the time of cast dowel and coping fabrication.     

Mechanical Properties of Magnetic Attachments for Removable Prostheses on Teeth and Implants

Purpose: Magnetic attachments on teeth and implants may be used to improve stability, support, and retention of removable prostheses. Various forms of magnetic attachments are available, divided according to the design, the mechanical properties of the attachments, and the clinical indication. Recently developed attachment systems are small and promise improved retentive capacity, while existing magnetic attachments continue to be technologically modified and improved. This investigation reviewed and compared maximum retentive forces and characteristic curves for magnetic attachments indicated for use as root anchors and on implants. Materials and Methods: Twenty‐four samarium‐cobalt (SmCo) and neodym‐iron‐boron (NeFeB) magnetic attachments (12 tooth‐ and 12 implant‐borne) were evaluated. Specimens were delivered by the manufacturers or fabricated according to their instructions. Five magnet pairs of each product and each combination were tested 10 times in a calibrated universal testing machine using a nonmagnetic test device (s = 40 mm, v = 20 mm/min). Results were recorded electronically and compared to manufacturers' details. Results: Maximum retentive forces for root keepers ranged from 1.4 to 6.6 N. Maximum retentive forces for magnetic attachments on implants ranged from 0.7 to 5.8 N. After a distance of 0.1 mm, a complete reversed distribution of the different systems became obvious. The retentive force provided by the manufacturer was achieved in one implant abutment, with retentive force (as compared to those provided by the manufacturers) for root keepers ranging between 42.5% and 92.9% and for implant abutments between 43.0% and 99.4%. Conclusion: There were differences between magnetic attachments for both the initial retentive capabilities and the characteristic curves. Recently introduced products provided relatively high initial retentive forces despite their small size. The measured retentive forces and the manufacturer's information differed in the majority of magnetic systems evaluated.     

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目的对比研究3种不同形状附着体固位力衰减趋势的差异。方法2007年1月至7月,于佳木斯大学口腔医学院制作5组附着体试件。A组:栓体栓道式附着体(配备黄色塑料帽套);B组:垂直球帽式附着体(配备黄色塑料帽套);C组:按扣式附着体(配备黄色塑料帽套);D组:垂直球帽式附着体(配备白色塑料帽套);E组:按扣式附着体(配备白色塑料帽套)。每组包含5个样本。对所有试件并进行固位力测试,进行1000次就位与脱位循环实验,每进行100次就位与脱位循环后,在电阻应变式力学测试机上重复10次测定其固位力,并观察固位力的衰减趋势。结果经1000次就位与脱位循环后A组固位力衰减(5.16±0.48)N,B组:(4.65±0.04)N,C组:(5.98±0.10)N,D组:(4.01±0.05)N,E组(5.24±0.67)N。A组与E组比较差异无统计学意义(P>0.05),其余各组间比较差异均有统计学意义(P<0.05),其中D组固位力衰减趋势最小,C组固位力衰减趋势最大。结论(1)3种附着体的固位力均随摘戴次数的增加而逐渐降低。(2)配备白色塑料帽套的垂直球帽式附着体固位性能最佳。     

Influence of attachment wear on retention of mandibular overdenture

The aims of this study were: (i) to evaluate and compare retention of two-teeth (implant) supported mandibular overdenture with either stud or magnetic attachments during linear (axial) and rotational (paraxial) dislodgements; (ii) to compare retentive properties before and after wear simulation. The test group consisted of five magnetic and four stud overdenture attachments (n = 12 specimens for each attachment type). Retention in axial direction was evaluated on one-tooth (implant) model by measuring maximum retentive force (N) and range of retention (mm) during the linear dislodgement. Retention in the paraxial direction was evaluated on mandibular-overdenture model by measuring the maximum retentive force (N) during three types of rotational dislodgements - anterior, lateral and posterior. The minimum number of cycles required to simulate wear was determined by special wear test. Afterwards, the wear was simulated in the test group, and retention in axial and paraxial directions was measured again. Statistical analysis: one-way anova, Scheffe post hoc and paired-samples t-tests (P < 0.05). Initially, studs had higher retention (4-11 N) than magnets (4.5-6 N) in axial direction. After the wear simulation, it had decreased from 76% to 48% for some of the studs and had become similar to the retention of magnetic attachments. Magnets had lower retention range (0.2-0.3 mm) than studs (0.5-1.1 mm). Studs provided similar or higher retention in paraxial directions than magnetic attachments both before and after wear simulation. Retentive properties of magnets decreased mostly with posterior rotational dislodgement. Retentive properties of stud overdenture attachments were less constant.     

Comparison of Retention and Strain Energies of Stud Attachments for Implant Overdentures

Purpose: The retentive forces and the strain energies absorbed during dislodging of implant overdenture stud attachments are useful parameters to consider in the selection of attachments. The purpose of this study was to compare the retentive forces and strain energies of the Nobel Biocare standard ball, Nobel Biocare newer generation ball (Yorba Linda, CA), Zest Anchor, Zest Anchor Advanced Generation (Escondido, CA), Sterngold‐Implamed ERA white, and Sterngold‐Implamed orange attachments (Attleboro, MA) on an implant‐retained in vitro overdenture model. Materials and Methods: The attachments were tested using two permanently placed Brånemark system implants on a test model attached to an Instron machine. Each attachment had one part embedded in a denture‐like housing, and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in two directions simulating function: vertical and oblique. Eight tests were done in two directions with six specimens of each attachment. Retentive forces generated and strain energies absorbed during displacement were determined. A 1‐way ANOVA followed by the Tukey studentized range test was used to determine groups that were significantly different at the p < 0.05 level. Results: The Zest Anchor Advanced Generation attachment had significantly the highest retentive vertical and oblique forces [37.2 (5.5) N and 25.9 (3.2) N, respectively]. The Zest Anchor had the lowest vertical force [10.8 (4.2) N], and Nobel Biocare Standard had the lowest oblique retentive force [10.6 (3.0) N]. The Nobel Biocare Standard Ball attachment had the highest strain energies [29.7 × 10^?3 (11.9 × 10^?3) J, 30.3 × 10^?3(14.3 × 10^?3) J, respectively, in the vertical and oblique directions]. The Sterngold‐Implamed ERA White and Zest Anchor had the lowest strain energies [5.3 × 10^?3 (3.2 × 10^?3) J and 4.5 × 10^?3 (1.1 × 10^?3) J, respectively, in the vertical and oblique directions]. Conclusion: The retentive forces and strain energies of implant overdenture stud attachments are different and should be considered during prosthesis selection.     

Maximum dislodging forces of implant overdenture stud attachments

PURPOSE: The aim of this study was to compare the retention and stability of the Nobel Biocare standard ball (NBS), Nobel Biocare 2.25-mm-diameter ball (NB2), Zest Anchor (ZA), Zest Anchor Advanced Generation (ZAAG), Sterngold ERA orange (SEO), and Sterngold ERA white (SEW) attachments on an implant-retained overdenture model. MATERIALS AND METHODS: The attachments were tested using 2 permanently placed Br?nemark System implants on a test model that was attached to an Instron machine (crosshead speed 50.8 mm/minute). Each attachment had one part embedded in a denture-like housing and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in 3 directions simulating function: vertical, oblique, and anterior-posterior. Eight tests were done in 3 directions with 6 samples of each attachment. The dislodging forces generated measurements of the peak load (maximum dislodging force). A 1-way analysis of variance followed by the Tukey studentized range test was used to determine groups that were significantly different. All tests for significance were carried out at the .05 level of significance. RESULTS: Results showed the ZAAG attachment to be the most retentive for the peak load measurement when subjected to vertically directed forces, with mean values and standard deviations of 37.2 +/- 5.5 N. The next most retentive attachment was the NBS, followed by the SEO, NB2, SEW, and ZA. For obliquely directed forces, the ZAAG attachment was the most retentive, with mean values and standard deviations of 27.2 +/- 4.2 N. The next most retentive was the NBS, followed by the NB2, SEO, ZA, and SEW. For anterior-posteriorly directed forces, results showed the NBS had the highest measured retentive force, with mean values and standard deviations of 34.6 +/- 18.8 N, but this was not statistically different from the NB2 and ZAAG; this was followed by the SEO, SEW, and ZA. DISCUSSION: There has been a marked resurgence in the treatment of patients with overdentures using implant attachments as retentive devices. The maximum force developed (a measure of retention) as the implant stud attachments were resisting removal from the implant abutments was determined. CONCLUSIONS: Based on the present study, the clinician may be able to make empirical decisions on attachment selection, depending on the amount of retention desired and the specific clinical situation.     

Comparison of the retentive characteristics of cobalt-chromium and commercially pure titanium clasps using a novel method

This study aimed to compare the retentive forces of cast cobalt-chromium (Co-Cr) and commercially pure titanium (cpTi) clasps. A clasp assembly comprising a pair of symmetrical clasps was made to fit the opposite halves of a hardened stainless-steel sphere. This twin clasp was designed to counterbalance the tipping forces when the clasp assembly was drawn from the sphere. A total of 120 clasp assemblies were fabricated in cast Co-Cr and cpTi and placed at undercut depths of 0.25 mm, 0.50 mm, and 0.75 mm (n = 20 for each). For Co-Cr clasps, the retentive forces at these undercuts depths were 2.34 +/- 0.23 N, 4.65 +/- 0.35 N, and 7.56 +/- 0.50 N, respectively. The corresponding retentive forces for cpTi clasps were 1.24 +/- 0.13 N, 2.34 +/- 0.23 N, and 3.70 +/- 0.27 N. The retentive force of cpTi clasps was approximately half that of Co-Cr clasps for the same undercut depth.     

The change in retentive force of magnetic attachment by abrasion

Magnets are frequently applied to removable dentures as retentive attachments. A magnet-retained removable overdenture might be slightly shifted from side to side by eccentric movement in the mouth, and the surface of magnetic attachment may be worn as a result. However, the relationship between the retentive force of magnetic attachment and its surface abrasion has not been reported. The purpose of this research is to investigate this relationship. Ten Mgfit DX 400 magnetic attachments for natural tooth roots were used for this experiment. The magnetic attachments were embedded in autopolymerizing acrylic resin, and ten pairs of specimens were fabricated. A 5-mm repeated gliding motion was applied on each pair of specimens until 30 000, 50 000, or 90 000 cycles had been achieved. The abrasion machine was under 5 kg loading, and the slide speed was 60 times/min. The retentive force of magnetic attachment was measured with a tension gauge at (1) before gliding; (2) after 30 000 gliding cycles; (3)after 50 000 gliding cycles; or (4) after 90 000 gliding cycles. The average change of retentive force of ten magnetic attachments after 30 000, 50 000, and 90 000 gliding cycles was 0.016 N, 0.003 N, and -0.008 N, respectively. The change was statistically analyzed using a paired-sample t test, which showed that the number of gliding cycles did not affect the retentive force of magnetic attachment significantly. The surface of magnetic attachment after gliding was observed by a microscope, and the abrasion of this attachment surface is clearly seen.