镍钛记忆合金在纵裂牙修复中的初探

后牙纵裂保留修复是牙体病治疗中的难题之一。一般均采用拔除患牙以减轻病人痛苦。为寻找有效安全的保留修复方法，口腔科医师虽做了不少探索但收效甚少。     

钛镍记忆合金牵张装置增高牙槽嵴对咀嚼肌的影响

目的:通过组织学观察,研究钛镍记忆合金牵张装置增高牙槽嵴对咀嚼肌的影响。方法:!重20～30kg健康成年杂种犬18只,3只为对照组,其余随机分为3组,每组5只。拔除所有犬双侧下颌前磨牙及第一磨牙,1个月后在实验组犬的一侧下颌骨植入钛镍记忆合金丝加工成的S形牵张装置。牵张器就位后骨块即开始牵张升起,术后一周增高量达7.5～11.5mm,其后无明显变化。分别在牵张后1、3、6个月处死5只实验犬和1只对照犬。取双侧嚼肌、颞肌、翼内肌、翼外肌进行组织学和超微结构分析。结果:!1个月时牵张侧各咀嚼肌纤维见少量淋巴细胞渗出。3个月组部分颞肌、嚼肌、翼内肌纤维扭曲、横纹消失,偶见肌纤维溶解,线粒体肿胀。6个月时各咀嚼肌肌纤维排列整齐,粗细均匀,肌节完整,肌横纹清晰,线粒体正常。结论:钛镍记忆合金牵张装置增高牙槽嵴是一种安全可靠的方法,对咀嚼肌的影响是轻微、可逆的。     

应用钛镍记忆合金牵张成骨增高下颌牙槽嵴的初步研究

目的 探讨应用钛镍记忆合金牵张成骨增高下颌牙槽嵴的可行性。方法 选用成年杂种犬10只，拔除两侧下颌全部前磨牙和第1磨牙，实验组1个月后用完全埋置的钛镍记忆合金牵张器完成牵张手术。在牵张手术前及术后1、5、13周测量术区颌骨高度，拍X线片，分别在牵张完成后1、3个月处死动物，进行组织学研究。结果 牵张器就位后骨块即开始牵张升起，术后1周达7．5～11．5mm，其后无明显变化。X线片可见牵张完成后1个月牵张区骨密度增高，有新骨生成；3个月骨密度与周围牙槽骨接近。组织学观察牵张区早期有胶原束形成，随后钙化成骨。结论 用钛镍记忆合金牵张器可成功牵张增高犬下颌后牙区牙槽嵴，新骨以膜内成骨方式生成。     

两种镍钛系统预备根管对牙根抗折强度的影响

目的比较ProTaper和K3镍钛预备系统预备根管对牙根抗折载荷的影响。方法 30颗完整的离体单根恒牙根管预备后随机分成三组,两个实验组分别采用ProTaper和K3镍钛预备系统预备根管,对照组采用不锈钢K锉逐步后退法预备根管,三组均采用冷牙胶侧压充填根管。将标本用万能试验机垂直加载直至标本发生纵裂,记录牙根纵裂时的最大抗压载荷和纵裂的类型。结果两个实验组的平均抗压载荷值分别是206.05±73.31N和210.04±64.57N,两个实验组之间无明显统计学差异。对照组平均抗压载荷值(269.10±56.64N)高于两实验组,但差异不具有统计学意义。83.3%的牙根纵裂线发生于颊舌方向。结论相比传统的逐步后退法,ProTaper和K3大锥度镍钛器械预备不会明显降低牙根的最大抗压载荷。以上两种镍钛预备技术对牙根抗压载荷的影响无区别。     

用于计算机辅助设计的镍钛记忆合金牵引器有限元模型的建立

目的探讨一种用于计算机辅助设计的镍钛记忆合金(NTMA)牵引器有限元模型的建立方法. 方法用Pro/E软件建立一个具有正弦波形、波长为60 mm,振幅为10 mm的镍钛记忆合金牵引器的几何模型,导入Marc软件,对其进行几何修复后生成实体单元,并按实际模拟边界条件,按镍钛合金定义初始条件和材料特性,最终得到镍钛记忆合金牵引器有限元模型.结果建立了用于计算机辅助设计的镍钛记忆合金牵引器有限元模型,可以预测一定形状的牵引器在变形过程中(各时段)其本身结构中各节点、单元的受力、位移情况.结论本研究率先运用镍钛记忆合金有限元模型进行计算机辅助设计,这一技术将有助于提高镍钛记忆合金器件的设计精度,并缩短其设计周期,节约设计成本.     

隐裂牙用不同材料充填后的抗裂强度与断裂功

将１４对同颌同名模拟隐裂的离体人后牙分成三组，分别用银汞合金和光敏复合树脂充填沿隐裂制备的窝洞，用材料试验机进行压缩试验。结果发现，光敏复合树脂充填制备洞缘小斜面的窝洞组抗裂强度较大，裂纹扩展所需外力明显大于银汞合金充填组，为临床选择早期隐裂牙的处理方法提供了科学依据。     

镍钛器械的抗折性能

与传统不锈钢器械相比，机用镍钛器械因其优异的机械性能而在临床得到广泛应用。镍钛器械在根管治疗过程中发挥着清理成形根管、控制感染的关键作用，已成为根管预备的主流器械。然而，深知其具备高效切削力的同时，如何防止并发症的发生也成为我们关注的重点，因此镍钛器械的抗折性能一直是临床研究的热点。文章就影响镍钛器械抗折性能的因素及预防措施做一介绍。     

4种镍钛正畸弓丝钛离子析出量的体外实验研究

目的:通过测试在人工唾液中4种品牌镍钛正畸弓丝钛离子的析出量,以了解其耐腐蚀性。方法:选择临床常用的4种品牌的镍钛正畸弓丝,分别为3M、SL、TP、SMT,调配人工唾液,并将人工唾液的pH值分别调节为4.0及6.75,减取的正畸弓丝两端较直的部分(每段2 cm)放入EP树脂管中,加入已调节好pH值的人工唾液1 mL,保存置37 ℃电子恒温箱,在1、7、28 d时分别取出弓丝样本后测试试管中钛离子的析出量,进行统计学分析。结果:第1天时4种品牌镍钛正畸弓丝钛离子的析出量最大,7、28 d时钛离子的析出量平均后,均要少于弓丝浸泡第1天时的析出量,不同品牌间钛离子的析出量的差别不具有统计学意义。结论:4种品牌的镍钛正畸弓丝具有良好的抗腐蚀性,但是酸性环境可以加速镍钛正畸弓丝中钛离子的析出量影响镍钛正畸弓丝的抗腐蚀性。     

多曲方丝弓与镍钛方丝在各牙位间的局部载荷挠曲率的对比研究

目的测量并比较多曲方丝弓与镍钛方丝分别在各牙位间的局部载荷挠曲率，分析多曲方丝弓的力学特性。方法用0．016×0．022英寸的不锈钢方丝按Kim标准弯制MEAW弓丝中独立的“L”形曲。用Instron 2343型电子万能材料力学试验机及Series Ⅸ软件在室温下对“L”形曲及0．016×0．022英寸NiTi平直方丝分别在上下颌各牙位间进行加载和卸载实验，测得各自的局部载荷挠曲率SPSS11．0软件包进行统计分析。结果“L”形曲与NiTi方丝在各牙位间加载和卸载时，在牙位1—2和2—3，各“L”形曲的局部载荷挠曲率比NiTi方丝的大，而在后牙区各牙位间的各“L”形曲的局部载荷挠曲率比NiTi方丝的小，其差异有显著性（P〈0．01）。结论MEAW的局部载荷挠曲率较之NiTi方丝，在前牙区更大，在后牙区更小，在牙位3—4和4—5下降得更多。     

钛镍记忆合金牵张器复合脱细胞真皮基质增高犬牙槽嵴的组织学研究

目的通过对牵张成骨增高牙槽嵴新生骨的组织学观察,研究钛镍记忆合金牵张器复合脱细胞真皮基质对成骨质量的影响。方法健康成年雄性杂种犬12只,建立牙槽嵴萎缩模型后1个月,一侧下颌后牙区行牵张手术并放入2个“S”形牵张器及异种脱细胞真皮基质（ADM）,另一侧为对照侧,仅行牵张术,不放置ADM。术后1个月、3个月各处死6只实验犬。将牵张区骨组织进行脱钙骨组织学观察,参照Parfit方法进行定量组织学测量。动物处死后取双侧下颌第3前磨牙区骨块,直接做骨切片,荧光显微镜下观察。结果1个月时,实验侧的平均骨小梁体积分数、平均骨小梁厚度、平均骨小梁数目均高于对照侧,平均骨小梁分隔距离低于对照侧;3个月时,实验侧平均骨小梁体积分数、平均骨小梁数目高于对照侧,平均骨小梁分隔距离低于对照侧。结论ADM阻力膜能改善牵张过程中力学的平衡,阻止周围软组织长入,改善成骨环境,提高成骨质量。     

Fatigue analysis of restored teeth longitudinally cracked under cyclic loading

ObjectiveTo investigate the fatigue behavior of restored teeth, in particular the mechanisms of longitudinal dentinal cracking under cyclic mechanical loading, using finite element analysis (FEA) and the stress-life (S-N) approach.MethodsTen root-filled premolars restored with resin composites were subjected to step-stress cyclic loading to produce longitudinal cracks. Fracture loads and number of cycles completed at each load level were recorded. FEA was used to predict the stress amplitude of each component under the global cyclic load. Both intact and debonded conditions were considered for the dentin-composite interface in the FEA. The predicted stress concentrations were compared with the fracture patterns to help elucidate the failure mechanisms. The S-N approach was further used to predict the lifetimes of the different components in the restored teeth. Cumulative fatigue damage was represented by the sum of the fractions of life spent under the different stress amplitudes.ResultsLongitudinal cracks were seen in ~50% of the samples with a mean fracture load of 770 ± 45 N and a mean number of cycles to failure of 32,297 ± 12,624. The longitudinal dentinal cracks seemed to start near the line angle of the cavity, and propagated longitudinally towards the root. The sum of fractions of life spent for the dentin-composite interface exceeded 1 after ~7000 cycles when that for dentin was much lower than 1, indicating that interfacial debonding would occur prior to dentin fracture. This was supported by micro-CT images showing widened interfacial space in the cracked samples. In the debonded tooth, FEA showed dentinal stress concentrations at the gingival wall of the cavity, which coincided with the longitudinal cracks found in the cyclic loading test. The sum of fractions of life spent for dentin was close to 1 at ~30,000 cycles, similar to the experimental value.SignificanceDebonding of the dentin-composite interface may occur prior to longitudinal cracking of dentin in root-filled teeth under cyclic loading. The approximate time of occurrence for these events could be estimated using fatigue analysis with stresses provided by FEA. This methodology can therefore be used to evaluate the longevity of restoration designs for root-filled teeth.     

A comparative study of root canal preparation with NiTi-TEE and K3 rotary Ni-Ti instruments

Aim To evaluate and compare several parameters of curved root canal preparation using two different Ni‐Ti systems: NiTi‐TEE (Sjöding Sendoline, Kista, Sweden) and K3 (Sybron Endo, Orange County, CA, USA). Methodology Fifty extracted mandibular molars with mesial root canal curvatures ranging from 20 to 40° were divided into two groups. In one group, 50 root canals were instrumented using NiTi‐TEE files to an apical size 30; 0.04 taper (the largest available size at the time of this study). In the other group, 50 root canals were prepared with K3 instruments to an apical size 45; 02 taper. Both systems were used in a crowndown manner, with copious NaOCl (3%) irrigation and a chelating agent (Calcinase Slide, lege artis, Dettenhausen, Germany), employing torque‐controlled motors. For assessment of shaping ability, pre‐ and postinstrumentation radiographs and cross‐sectional photographs of canals were taken and changes in canal curvature and root canal diameter documented. Cleaning ability was evaluated by investigating specimens of the apical, medial and coronal third of the root canal wall under a scanning electron microscope using 5‐score indices for debris and smear layer. Procedural errors (instrument separations, perforations, apical blockages, loss of working length) and working time were recorded. Nonparametric anova was used to compare straightening of canal curvatures, canal cross‐sections and canal wall cleanliness (P < 0.05), whereas working time was analysed using the parametric anova (P < 0.05). Results Both Ni‐Ti systems maintained curvature well: the mean degree of straightening was 0.2° for NiTi‐TEE and 0.4° for K3 with no statistical significance between the groups. Post‐instrumentation cross‐sections of the root canals revealed an acceptable contour (round or oval) in 50.6% of cases for the NiTi‐TEE group and in 65.3% of cases for the K3 group. The difference was not significant. The SEM investigation of canal walls showed equally good debris removal for both systems: NiTi‐TEE prepared canal walls in 74.7% of cases with scores I and II; K3 achieved these scores in 78.7% of cases. For smear layer, NiTi‐TEE and K3 only received good scores (I and II) in 38.7% and 40% of canal wall specimens, respectively. For both parameters, no significant differences were found between groups. File fractures did not occur, but loss of working length was observed in one case following the preparation with NiTi‐TEE and in three cases during K3 instrumentation. Mean working time was significantly shorter for NiTi‐TEE (170 s) than for K3 (208 s). Conclusions Both systems maintained original canal curvature well and were safe to use. Whilst debridement of canals was considered satisfactory, both systems failed to remove smear layer sufficiently.     

下颌第一磨牙隐裂模型裂纹变化的三维有限元分析

目的研究隐裂下颌第一磨牙受力后裂纹的变化情况,以及裂纹存在对牙齿受力后整体位移的影响。方法建立包含不同深度和长度裂纹的隐裂下颌第一磨牙的三维有限元模型以及无裂纹对照模型,模拟咬合过程,确定6种加载方式,通过有限元计算,求得不同裂纹的变化情况以及裂纹存在对牙齿整体位移的影响。结果随着裂纹深度和长度的增加,面裂纹的宽度亦变大,载荷4的影响最大。开裂时裂纹边缘不齐,相邻节点不在同一平面上。邻面裂纹在载荷6工况下开裂最大。裂纹存在时牙齿整体位移增加,但对牙齿整体位移的影响是有限的。结论裂纹的变化与初始裂纹形式和载荷工况密切相关。     

早期牙隐裂活髓保存的临床疗效观察

目的:探讨早期牙隐裂活髓保存的临床治疗方法.方法:对诊断为早期牙隐裂的56例患者的隐裂牙共计63颗,据病史及临床检查分别采用光固化树脂直接充填或MTA垫底后光固化树脂充填,然后以贵金属冠进行修复治疗,随访2年,观察其疗效.结果.63颗患牙经治疗后临床随访2年,成功57颗,失败6颗,治疗有效率达90.4％.结论:早期牙隐裂的治疗以光固化树脂充填或MTA垫底后以光固化树脂充填,然后以贵金属冠修复是保存活髓和防止牙齿折裂的有效方法.     

A histopathologic study of replanted teeth with superficially demineralized root surfaces in Java monkeys

abstract — Since unmineralized tissues are supposed to possess a resistance to resorption, and demineralized dentin implants induce bone formation and may be remineralized, it was thought worthwhile to study the effect of superficial demineralization of the root surface prior to replantation of the maxillary incisors in 14 Java monkeys. The investigation showed that this treatment caused an accentuated resorption and ankylosis of the tooth as well as other pathologic changes in the periodontium. The technique neither improves the healing of the replanted tooth nor prolongs the survival time.     

恒牙牙颈曲度的测量研究

目的：探讨国人恒牙牙颈曲度的变化规律及其意义。方法：用牙科专用测量尺测量１４００个离体恒牙牙颈曲度。结果：国人恒牙牙颈曲度从前牙至后牙逐渐减小，而同一牙近中面大于远中面；下颌前牙牙颈曲度小于上颌前牙；并且国人牙颈曲度从前牙至后牙的近中远中差异均较外国人小；另外，部分后牙出现反向牙颈曲度。结论：牙颈曲度的大小是与牙齿外形、邻接点的位置和牙周附着有关，在临床操作中应加以注意     

机用和手用镍钛器械对不同弯曲度根管预备后的碎屑及预备效率的研究

目的 研究比较机用镍钛锉ProTaper Gold和手用镍钛锉ProTaper对不同弯曲度根管预备后的根尖碎屑推出量及预备效率.方法 将纳入标准收集的离体牙根管按不同的弯曲度(小于15°、20°～35°)分为2组,每组再按不同类型的镍钛器械(PTG、PTH)将其随机分为2个亚组(n=15).PTG组采用ProTaper...     

A study of replanted permanent teeth in different age groups

Abstract— The purpose of this study was to evaluate the benefits of replanting avulsed permanent teeth in different age groups. Of the 112 replanted teeth, 103 could be examined after 2.5 years on average. The teeth were divided into three groups: immature teeth (group A), mature teeth in children and adolescents (group B), and mature teeth in adults (group C). Concomitant injuries did not differ statistically between the groups. Extra-alveolar time with un-physiologic storage was longer than 15 min in 81 teeth. The results were statistically different for pulpal healing (A>B>C), loss of marginal bone (C>A), amount of replacement resorption (A and B>C), alveolar growth inhibition (A>B>C), local gingivitis (B>A and C) and buccal gingival retraction (C>A and B). Only 3 of 23 extracted teeth were lost because of replacement resorption alone. Only 2 of the 23 extracted teeth showed revascularization of the pulp. The results suggested that replanting aculsed teeth should be considered a temporary solution in children and adolescents. In these patients, the benefit of tooth replantation is mainly the time gained to establish an optimal treatment plan. Mature teeth with a necrotic periodontal ligament replanted in children before the pubertal growth spurt seemed to have the poorest prognosis.     

铸造桩表面喷砂处理对牙根抗折性能影响的体外实验研究

目的：研究铸造桩表面喷砂处理对牙根抗折性能的影响。方法：20颗近期拔除的单根第一前磨牙,根管治疗后于釉牙骨质界冠方1.5mm截冠,随机分为2组,铸造桩核及金属全冠修复。实验组铸造桩粘固前表面喷砂处理,对照组不作处理。试件包埋于丙烯酸树脂块中,在电子万能实验机上进行测试。结果：对照组牙根折裂强度为2.773±0.357kN,实验组牙根折裂强度为3.113±0.357kN,2组间差异具有统计学意义（P〈0.05）。结论：对铸造金属桩表面进行喷砂处理,可以提高桩核冠修复后牙根的抗折强度。