烤瓷冠基牙折断后的再修复

目的　探讨烤瓷冠基牙折断后的再修复方法。方法　采用红膏取根管模型铸造法制作。结果　本组 8例基牙再修复后 ,经 3年随访 ,未出现松动、脱落现象 ,固位良好。结论　用铸造法制作桩冠桩核强度高 ,与根管壁密合 ,粘固手不易脱落与原烤瓷牙冠密合 ,不需要重新制作 ,节约了时间和费用 ,延长了烤瓷冠的使用寿命。     

Failure modes of Y-TZP crowns at different cusp inclines

Objectives

To compare the reliability of the disto-facial (DF) and mesio-lingual (ML) cusps of an anatomically correct zirconia (Y-TZP) crown system. The research hypotheses tested were: (1) fatigue reliability and failure mode are similar for the ML and DF cusps; (2) failure mode of one cusp does not affect the failure of the other.

Methods

The average dimensions of a mandibular first molar crown were imported into CAD software; a tooth preparation was modelled by 1.5 mm marginal high reduction of proximal walls and occlusal surface by 2.0 mm. The CAD-based tooth preparation was milled and used as a die to fabricate crowns (n = 14) with porcelain veneer on a 0.5 mm Y-TZP core. Crowns were cemented on composite reproductions of the tooth preparation. The crowns were step-stress mouth motion fatigued with sliding (0.7 mm) a tungsten-carbide indenter of 6.25 mm diameter down on the inclines of either the DF or ML cusps. Use level probability Weibull curve with use stress of 200 N and the reliability for completion of a mission of 50,000 cycles at 200 N load were calculated.

Results

Reliability for a 200 N at 50,000 cycles mission was not different between tested cusps. SEM imaging showed large cohesive failures within the veneer for the ML and smaller for the DF. Fractures originated from the contact area regardless of the cusp loaded.

Conclusion

No significant difference on fatigue reliability was observed between the DF compared to the ML cusp. Fracture of one cusp did not affect the other.     

ALL-CERAMIC AND PORCELAIN-FUSED-TO-METAL FIXED PARTIAL DENTURES: A COMPARATIVE STUDY BY 2D FINITE ELEMENT ANALYSES

All-ceramic fixed partial dentures (FPDs) have an esthetic approach for oral rehabilitation. However, metal-ceramic FPDs are best indicated in the posterior area where the follow-up studies found a lower failure rate. This 2D finite element study compared the stress distribution on 3-unit all-ceramic and metal-ceramic FPDs and identified the areas of major risk of failure. Three FPD models were designed: (1) metal-ceramic FPD; (2) All-ceramic FPD with the veneering porcelain on the occlusal and cervical surface of the abutment tooth; (3) All-ceramic FPD with the veneering porcelain only on the occlusal surface. A 100 N load was applied in an area of 0.5 mm² on the working cusps, following these simulations: (1) on the abutment teeth and the pontic; (2) only on the abutment teeth; and (3) only on the pontic. Relative to the maximum stress values found for the physiological load, all-ceramic FPD with only occlusal veneering porcelain produced the lowest stress value (220 MPa), followed by all-ceramic FPD with cervical veneering porcelain (322 MPa) and metal-ceramic FPD (387 MPa). The stress distribution of the load applied on the abutments was significantly better compared to the other two load simulations. The highest principal stress values were low and limited in a small area for the three types of models under this load. When the load was applied on the pontic, the highest stress values appeared on the connector areas between the abutments and pontic. In conclusion, the best stress values and distribution were found for the all-ceramic FPD with the veneering porcelain only on the occlusal surface. However, in under clinical conditions, fatigue conditions and restoration defects must be considered.     

磨牙纵折保留修复的临床观察

目的:探讨利用桩核烤瓷冠辅以牙龈切除术或牙冠延长术修复纵折至龈下的磨牙,以提高纵折磨牙保存成功率的方法。方法:对56例劈裂至龈下的第一磨牙去除牙折片后采用镍铬合金桩核加3种不同种类烤瓷冠(镍铬合金烤瓷冠、金铂合金烤瓷冠、IPS EmpressⅡ铸瓷冠)进行修复,部分配合牙冠延长术或牙龈切除术,随访观察1年,比较直接修复和配合牙周手术对修复效果的影响,以及不同种类烤瓷冠对修复效果的影响。结果:纵折磨牙拔除牙折片后采用桩核烤瓷冠直接修复和配合牙冠延长术修复,随诊观察1年后的修复有效率分别为80%和94.4%,后者治疗效果好于前者,差异有统计学意义。两种修复方法中,失败者均出现在镍铬合金烤瓷冠修复中。结论:修复劈裂至龈下的纵折磨牙采用桩核烤瓷冠配合牙冠延长术或牙龈切除术是一种有效的治疗方法,贵金属烤瓷冠和全瓷冠的应用会进一步提高修复效果。     

磨牙残根的修复治疗

目的:探讨利用铸造桩核加金属烤瓷冠桥修复磨牙残根的方法。方法:15颗磨牙残根,经完善的根管治疗后,采用桩核加烤瓷冠桥修复。结果:经1a～3a临床观察,修复体稳固,边缘密合,牙周、根周无明显炎症。结论:经完善根管治疗的磨牙残根,应用桩核加烤瓷冠、桥修复效果良好。     

IPS Empress 2铸瓷技术在前牙美容修复中的应用

目的：对IPS Empress 2新型铸瓷系统在前牙美容修复中的临床应用情况进行评价。方法：使用IPS Empress 2铸瓷系统相关设备及材料对要求前牙美容修复的患者进行全瓷冠桥的设计修复。计21例患者，118颗前牙，其中双端基牙的全瓷桥3例，其余为单冠修复。临床病例选择、设计、牙体预备、技工加工等均依铸瓷冠桥适应症及设备、材料的基本要求，使用配套粘结剂粘结固定。1周内常规复诊。结果：经3～8个月临床观察，除1颗牙冠因牙体预备不足咬黯力大，舌侧冠薄导致崩瓷以外，其余修复牙边缘密合无龈炎出现，冠桥稳定，未出现不良牙髓反应，尤其光学通透性佳，自然逼真，美学效果良好。结论：IPS Empress 2铸瓷系统比第一代产品提高了强度，生物相容性好，刺激性小，修复体自然美观。     

Capillary pore rheology of erythrocytes: IV. Effect of pore diameter and haematocrit

In preceding work (Lingard, P. S., 1974, Microvasc. Res.8, 53–63; Lingard, P. S., 1977, Microvasc. Res.13, 29–58), erythrocyte suspensions were found to exhibit nonlinear hydrodynamic resistance behaviour in the narrow capillary pores of a new rheometer, which embodies a Nuclepore filter. For pores of diameter 4–7 μm, constant, relatively high resistances were found at low velocities, giving way to falling resistances with increasing velocity beyond a well-defined transition point The resistances are consistent with virtual occlusion of the lumen by the cells, and the resistance changes with changing clearance due to distortion of the cells. This paper shows that resistance within a population of donors is greater in narrower pores and increases with suspension concentration. Representative parameters (viz., lubricating film width, pressure drop per cell) depend strongly on the pore diameter. Resistance-concentration relations are not linear and differ from expectation of hydrodynamic theory. The differences are explained by a shunting mechanism, based on a hypothesis of random cell distribution among the pores. This reduces resistance measured in multipore filters compared with baseline data for long-bore tubes, reinforcing earlier conclusions that cells are tight-fitting in capillary pores and that resistance changes by elastic deformation of the cells.     

牙根改形结合少量去骨:一种改良的牙冠延长术

目的:提出一种改良的牙冠延长手术方法来形成修复所需要的的生物学宽度.方法:采用一种牙根改形结合少量去骨的方法来恢复丧失的生物学宽度.7颗要求修复的患牙,均因折断面位于牙槽嵴顶以下过多而属常规牙冠延长术的禁忌证.采用上述手术方法后2个月进行了修复,定期检查牙齿松动度、菌斑指数、牙龈指数和探诊深度,并追踪观察10个月以上.结果:7例患者追踪观察平均17个月(10～31个月)后术牙牙龈健康、美观、稳定.结论:牙根改形结合少量去骨的方法作为传统牙冠延长术的一种改良,扩大了牙冠延长术的适应证,保存了更多的残根、残冠.     

牙冠轴面突度的变化对牙周组织健康的影响

目的　研究不同程度增加牙冠轴面突度对牙周龈沟液量 (GCF)、龈沟液中天冬氨酸转氨酶 (GCF AST)、碱性磷酸酶 (GCF ALP)水平及软垢堆积水平的影响。方法　将牙冠颊面分别增加0 2mm、0 5mm和 0 8mm ,于 1、4和 8周时测量龈沟液量 ,检测GCF AST、GCF ALP水平 ,记录软垢堆积水平。结果　牙冠轴面突度增加 0 2mm ,各指标没有明显变化 ;增加 0 5mm ,GCF AST水平明显增加 ;增加 0 8mm ,GCF AST、GCF ALP水平增加显著。结论　牙冠轴面突度增加不利牙周健康 ,增加越大 ,牙周健康受到的损害越大     

后牙纵折保存治疗的临床观察

目的探讨后牙冠根纵折保存修复治疗的方法与疗效。方法采用复位环扎固定,经降牙合、备洞及完善根管治疗后全冠修复。结果56例折裂牙治疗成功48例(85.71%);6例因牙周感染或急性根尖周炎而拔除(10.71%);2例未能全程随访。结论对纵折病例经完善的根管治疗进行全冠修复,是一种行之有效的治疗方法。