热处理对磁性附着体固位力的影响

目的:研究热处理对磁性附着体固位力的影响。方法:磁性附着体Magfit EX 400W型、Magfit EX 600 W型和Magfit EX 800W型各10个试件,通过模具固定在万能力学试验机的测试台上,测试其固位力,然后将磁性附着体经过水浴热处理,再次进行固位力测试。采用SPSS11.0软件包对数据进行统计学分析。结果:磁性附着体Magfit EX400W型、Magfit EX 600W型和Magfit EX 800W型的初始固位力测量值分别为(1.64±0.11)N、(2.67±0.19)N和(3.02±0.25)N;经热处理后,其固位力测量值分别为(1.58±0.12)N、(2.65±0.14)N和(3.02±0.24)N。热处理前、后,其固位力无显著差异(P>0.05)。结论:磁性附着体的磁体部分可进行水浴热处理以减少单体,而其固位力无显著改变。     

Probing nano-scale adhesion force between AFM and acid demineralized intertubular dentin: Moist versus dry dentin

Objective

The aim of this study was to investigate the effect of dentin dryness on the variation in the probed nano-scale adhesion force between an AFM silicon nitride tip and demineralized intertubular dentin collagen fibrils network surface.

Methods

Dentin specimens were etched with 37% phosphoric acid for 15 s and then divided into three groups. Specimens of the first two groups were air-dried for 5 or 10 s (DH5s and DH10s), respectively, whereas specimens of the third group were left in the hydrated condition (H). For each group, Force curves were characterized by contact-mode AFM and the adhesion force (Fad) was calculated. The structure of the demineralized collagen fibrils network was characterized by tapping mode AFM. The tensile bond strength (TBS) to dentin was evaluated using one alcohol-based dentin self-priming adhesive. The dentin/resin interface was investigated by SEM.

Results

Dentin specimens in the wet-hydrated condition (H) showed significantly higher adhesion force and TBS values than dry-dehydrated specimens (DH5s and DH10s). AFM images showed open collagen fibrils network structure in wet-hydrated specimens (H), while the dry-dehydrated specimens (DH5s and DH10s) showed a collapsed appearance to varying degrees. SEM images revealed minimum resin infiltration in dry-dehydrated specimens.

Significance

The nano-scale adhesion force between the AFM probe and demineralized intertubular dentin surface was shown to be sensitive to surface air-drying. The decrease in the nano-scale adhesion force with the increase in the time of air-dryness is related to dehydration of the demineralized collagen fibrils network surface.     

Relationship between masticatory function, dental arch width, and bucco-lingual inclination of the first molars

The aim of this study was to clarify the influence of masticatory function on dental arch forms. We evaluated the relationship between the masticatory movement path and occlusal force (as masticatory function) and the dental arch width and first molar bucco-lingual inclination. The subjects were 60 healthy adult females (mean 23.4 years; S.D. 1.6 years) without previous orthodontic treatment or functional abnormalities in the temporomandibular joint. Furthermore, the subjects were divided into a wide group (W-group) and a narrow group (N-group) based on mean maxillary inter-molar width in Japanese females. The masticatory path was recorded using gnathohexagraph system. Maximum occlusal force was measured using a simple type occlusal force meter. And subjects’ arch width and bucco-lingual inclination of the first molars was measured. W-group showed larger arch width and the first molar was more upright on the buccal side compared with N-group. Furthermore, the lateral component of masticatory movement and maximum occlusal force was large in W-group compared with N-group. In the group which strong occlusal force and grinding type mastication had wide arch width and the mandibular first molars upright on the buccal side.     

附着体数量分布对固位力影响的测试

目的：对不同数量及分布的钉幅附着体固位力进行测试，为临床应用提供参考依据。方法：分别制作不同的附着体测试模型，用固位力测试仪进行测试。结果：附着体越多，固位力越大；3个附着体固位，受相互制约作用影响，平均每个附着体的固位力要大于单个附着体的固位力。附着体处加载所测的固位力明显大于单个附着体的固位力，显示其协同作用，附着体安置的距离影响固位力的大小，距离远固位力增加。结论：使用两个附着体的设计，其固位力一般都能满足临床需要，过多使用附着体可能导致脱位困难。     

平衡力法预备弯曲根管的临床评价

目的：评价用平衡力法预备弯曲根管的临床疗效。方法：选取有弯曲根管的牙髓炎和根尖周炎患牙48个，试验组用弹性K锉(Flexofile)，使用平衡力法预备根管；对照组用K挫，逐步后退技术预备根管，两组均用侧向加压充填法充填根管，根据治疗前、中、后的x线片评价根管预备和充填的效果。结果：两组在根管预备中无器械折断。试验组无根尖阻塞、台阶形成等并发症发生，发生根管偏移少，能较好地维持根管的弯曲度和走向。对照组1例有台阶形成，发生根管偏移的明显多于试验组(P＜0．05)。结论：平衡力法预备弯曲根管可以节约成本，缩短操作时间，较好地维持根管的定向和弯曲度，减少根管偏移。安全有效，实用性强，可作为临床上预备弯曲根管的有效方法。     

高性能固定矫治用磁体与橡皮圈组合力的评价

目的:分析与托槽大小相近的高性能固定矫治用磁体与橡皮圈形成的组合力的稳定性及有效工作距离。方法:将形状及体积与托槽相近的N48型钕铁硼,分别与1/8、3/16、1/4、3/8inch正畸弹力橡皮圈组合成超长距离移动牙齿的组合力,使用万能材料实验机对磁体磁力、橡皮圈弹力和组合力进行测试,并绘制力的变化曲线,分析组合力的特征、磁力与橡皮圈弹力的互补作用、不同拉伸距离的组合力中磁力及弹力的构成比,对组合力与橡皮圈弹力的差异进行t检验。结果:随着拉伸间距的加大,磁体磁力急剧下降,而橡皮圈弹力呈线性增大,组合后力的变化较为平缓,力较为恒定,4种组合力分别达到86、138、163、192g超长工作距离(1.25～20mm)稳恒矫治力。拉伸距离为3mm时,磁力占各组合力的百分比范围是34.94%～93.98%。拉伸距离为6mm时,占组合力的12.60%～37.89%。拉伸距离为12mm时,磁力降到仅占组合力的2.69%～5.98%。统计结果显示,拉伸距离为3mm(P<0.01)、6mm(P<0.01)、9mm(P<0.05)时,4种组合力与单独的橡皮圈弹力的差异有显著性。结论:磁体与橡皮圈形成的组合力是一种新型、理想、超长工作距离的稳恒矫治力。     

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。     

牙周炎患者的合力,肌功能及下颌运动轨迹描记

本研究对４０例牙周炎患者的合力、咀嚼肌肌电和下颌运动轨迹作了检查，结果表明，患者的超、覆合值异常且个体差异很大，但ＩＣＰ后移者仅２例。下颌从肌位到牙位发生偏斜者少，这与牙齿的松动有关，ＭＫＧ显示合间隙＜１ｍｍ者２０例。下颌姿势位肌电值明显升高。表明牙周炎患者的咀嚼肌处于较紧张状态。最大紧咬肌电值及平均每牙合力值明显减小，这与牙周组织的炎性破坏密切相关。     

微机化多功能力仪的研制及应用

介绍具有多功能、多通道及多参数测试特点的微机化力测试仪的研制方法，并用其进行了无牙颌患者戴全口义齿后咀嚼不同食物时的咀嚼力测试研究。测试表明，仪器性能稳定，灵敏度高，重复性好，数据可靠，测试结果满意     

A study on kinetic frictional properties in Begg/KB orthodontic appliances at posterior sites

In Begg and KB techniques, the kinetic frictional force generated between their characteristic orthodontic appliances at posterior sites and the orthodontic wire affects the efficiency of tooth movement. We compared the kinetic frictional force between the recent orthodontic appliances for posterior sites: the by-pass loop-KB buccal tube system (loop-KB tube system) and the conventional by-pass clamp-round buccal tube system (clamp-round tube system), and elucidated the frictional properties of the loop-KB tube system. We used 016"/018" round wires (016/018 round) and 022" × 016" ribbon wire (022 ribbon) with anchorage bend/curve applied. The results obtained were as follows: