三种抛光套装对氧化锆全瓷冠抛光效果比较研究

目的　比较临床常用的3种抛光套装对氧化锆全瓷冠的抛光效果。方法　使用绿色砂石打磨大小相同的圆柱状氧化锆试件45块,随机均分为5组,分别命名如下。SHOFU组：采用Procelain Adjustment Kit PN0301抛光试件;EVE组：采用Rotary Grinding and Polishing Instruments HP321抛光试件;Kerr组：采用Occlubrush抛光刷抛光试件;上釉组：试件表面进行上釉处理;对照组：试件不做处理。测量各组试件表面粗糙度Ra值,在扫描电子显微镜（scanning electron microscope,SEM）下观察试件表面形貌。将牙龈卟啉单胞菌与上述试件混合培养,测定其表面细菌黏附量,并在SEM下观察细菌的黏附情况。结果　各组试件表面粗糙度Ra值及细菌黏附量总的比较,差异具有统计学意义（均P < 0.05）。SHOFU组、EVE组、Kerr组试件表面粗糙度Ra值和细菌黏附量均依次增大,且组间比较差异均有统计学意义（均P < 0.05）。SEM观察显示,SHOFU组、EVE组试件表面见浅细划痕;Kerr组、对照组试件表面见深划痕和密集的凹坑缺陷;上釉组试件表面光滑。细菌在SHOFU组、EVE组、Kerr组、对照组试件表面主要分布在划痕及缺陷周围,其中SHOFU组和EVE组细菌数量较少,Kerr组和对照组数量最多;细菌在上釉组试件表面散在分布,数量最少。结论　3种抛光套装中,Procelain Adjustment Kit PN0301的抛光效果最好。     

稀土氧化物着色牙色四方多晶氧化锆陶瓷的机械性能研究

目的探讨添加微量稀土氧化物对牙色四方多晶氧化锆（Y-TZP）陶瓷的机械性能的影响。方法以稀土氧化物（Pr6O11、CeO2、Er2O3）和过渡元素氧化物（MnO2）为着色剂,采用粉体掺杂方法在Y-TZP粉体中添加不同质量分数的着色剂,制备出6组牙色Y-TZP,测试其机械性能（包括弯曲强度、维氏硬度、断裂韧性）,并通过扫描电子显微镜观察各组陶瓷烧结体断裂面的显微结构,分析其断裂模式。结果6组牙色Y-TZP的弯曲强度为（792±20）～（960±17）MPa,断裂韧性为（4.72±0.31）～（5.64±0.38）MPam1/2,维氏硬度为（1 332±19）～（1 380±17）MPa;显微结构显示6组陶瓷均呈致密的多晶结构,断裂模式为混合型断裂。结论以稀土氧化物作为着色剂制备的Y-TZP具有较好的断裂韧性和维氏硬度,可满足口腔临床的应用要求。     

凝胶注模氧化锆陶瓷浆料颗粒级配研究

目的:配制凝胶注模法成型氧化锆陶瓷浆料,研究颗粒级配的混合氧化锆颗粒粉末配制凝胶注模氧化锆浆料后素坯的收缩和预烧结后的尺寸变化。方法:采用不同的颗粒粒径,制作氧化锆浆料,分为纳米组H1(26 nm);亚微米组H2(300 nm);混合组H3(1μm+300 nm+26 nm)。测试浆料的固含量与收缩率。结果:H1,H2,H3组的固含量分别为60.11 wt%,81.58 wt%,82.36 wt%;素坯的收缩率分别为0.87%,0.26%,0.29%,致密化收缩率分别为26.1%,23.1%,22.4%。结论:采用颗粒级配的混合组H3(1μm+300 nm+26 nm)的氧化锆浆料具有最高的固含量及最低收缩率。并获得最适合玻璃渗透的预烧结程序。     

Eruption of the central incisor,the intermaxillary suture,and maxillary growth in patients with a single median maxillary central incisor

The occurrence of a single median maxillary central incisor (SMMCI) is a very rare condition and might be a sign of a more severe midline defect, which could be a mild degree of holoprosencephaly. Absence of the internasal and partial absence of the intermaxillary suture has been observed in a fetus with holoprosencephaly. The purpose of this study was to evaluate the intermaxillary suture, the eruption pattern of the single central incisor in the SMMCI condition, and the growth of the maxilla in a group of patients with SMMCI. A similar study was not found in the scientific literature. The material included orthopantomographs, dental radiographs, and lateral cephalometric radiographs from 11 patients with an SMMCI. The orthopantomographs and dental radiographs showed that the intermaxillary suture was abnormal anterior to the incisive foramen; however, the SMMCI erupted within the expected time interval. Superimposition on stable structures on lateral cephalometric radiographs from two untreated patients, in which growth analysis was possible, showed that the horizontal and vertical growth of the maxilla was normal. Due to the sutural midline defect it is suggested that a transversal growth analysis is included in all treatment planning of SMMCI patients.     

Durability of bond between an indirect composite veneering material and zirconium dioxide ceramics

Abstract

Objective. The purpose of the present study was to evaluate the durability of bond strength between an indirect composite material and zirconia ceramics after thermocycling (100 000 cycles) and to assess the effect of various priming agents for zirconia surface treatments. Materials and methods. A CAD/CAM system (Katana, Noritake Dental Supply) was used to fabricate 96 zirconia disks as a bonding substrate. The specimens were randomly divided into six groups (n = 16) and treated with one of the following acidic priming agents: Alloy Primer (ALP, Kuraray), Clearfil Ceramic Primer (CCP, Kuraray), Clearfil Photo Bond (CPB, Kuraray), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB + Activator, Kuraray), Estenia Opaque Primer (EOP, Kuraray) and Porcelain Liner M Liquid A (PLA, Sun Medical). The specimens were bonded with an indirect composite material (Estenia C&B Dentin, Kuraray). Shear bond strengths were tested before and after 100 000 thermocycles and the data were analyzed by using the Steel-Dwass test and Mann-Whitney U-test. Results. After 100 000 thermocycles, the PLA group showed the lowest bond strength (p = 0.010), whereas the CPB + Activator (23.9 MPa; p < 0.014) and CPB (22.7 MPa; p < 0.028) groups had significantly higher bond strengths than the other groups. The Mann-Whitney U-test revealed that bond strengths did not significantly decrease after thermocycling, except for specimens in the PLA (p = 0.038) and CCP (p = 0.028) groups. Conclusions. Application of a combination of hydrophobic phosphate monomer (MDP) and initiator results in a durable long-term bond between Katana zirconia and Estenia C&B composite material.     

Implant-supported full-arch zirconia-based mandibular fixed dental prostheses. Eight-year results from a clinical pilot study

Abstract

Objective. The purpose of this pilot study was to evaluate the long-term clinical performance of implant-supported full-arch zirconia-based fixed dental prostheses (FDPs). Materials and methods. Ten patients received full-arch zirconia-based (Cercon) mandibular FDPs supported by four implants (Astra Tech). Nine patients received 10-unit FDPs and one patient received a 9-unit FDP. The FDPs were cemented onto individually prepared titanium abutments and were evaluated at baseline and after 12, 24, 36 and 96 months. Results. Nine patients attended the 8-year follow-up. None of the restorations showed bulk fracture, all FDPs were in use. Fractures of the veneering porcelain were, however, observed in eight patients. A total of 36 out of 89 units (40%) showed such fractures. Patient satisfaction was excellent despite the veneering material fractures. Conclusion. Results from this 8-year pilot study suggest that implant-supported full-arch zirconia-based FDPs can be an acceptable treatment alternative.     

Acceptance of dental care following early extractions under rectal sedation with diazepam in preschool children

The aim of the study was to evaluate the effect of amnesia in preschool children on their later acceptance of dental care. Forty-six 4-6-year-old children, who between 2 and 4 years previously had had primary incisors extracted because of trauma, were reexamined for dental health and acceptance of dental care. The extractions had been performed under rectal sedation with diazepam (0.7 mg/kg body weight). Information about dental treatment and degree of cooperation during the intervening period was obtained from records at the referring clinic. The parents were interviewed about their child's experience of amnesia concerning the extractions, background variables, and experiences of dental care before the follow-up examination. Amnesia concerning the extractions was reported in 85% of the children. Twenty-nine percent had on some occasion exhibited behavior management problems (BMP) during the intervening period. Lack of amnesia was significantly associated with BMP (P &lt; 0.002). Children without amnesia concerning the extractions tended to accept dental care less well at the reexamination. Parents were able to predict their child's acceptance of dental care at the follow-up with a significant degree of success (P = 0.02). In conclusion, amnesia in preschool children concerning extractions seems to be essential to facilitate positive acceptance of future dental care.     

IPS-Empress II inlay-retained fixed partial denture reinforced with zirconia bar: Three-dimensional finite element and in-vitro studies

Abstract

Objective. This study evaluated von Mises stress distribution, flexural strength and interface micrographs of IPS-Empress II (IPS) inlay-retained fixed partial dentures (IRFPD) reinforced with Zirconia bars (Zb). Materials and methods: In the Finite element analysis, six three-dimensional models of IRFPD were designed using Solid Works 2006. Five models were reinforced with different Zb and a model without Zb was considered as a control. The bridges were loaded by 200 and 500 N forces at the middle of the pontic on the occlusal surface. Subsequently, von Mises stress and displacement of the models were evaluated along a defined path. In the experimental part, 21 bar shape specimens were fabricated from lithium disilicate and zirconia ceramic in three different designs. The zirconia-IPS interfaces and the fractured surfaces of flexural test were observed using SEM. Results. In the connector area, von Mises stress and displacement of the models with Zb under a load of 500 N were decreased compared to the model without the Zb; however, this difference was not considerable at a load of 200 N. In the mesial connector, Von Mises stress and displacement was decreased from 12.5 Mpa for the control model tested at 500 N to 7.0 Mpa for the model with Zb and from 0.0050–0.0041 mm, respectively. SEM analyses showed that, before fracture, interfacial gaps were not observed along the interfaces, but initiated cracks propagated along the interfaces after flexural loading. Conclusion: IPS IRFPD reinforced by Zb can tolerate higher stresses while still functioning effectively and the interfaces may have desirable adaption.     

微波二次烧结牙科纳米氧化锆全瓷材料的实验研究

目的：研究微波二次烧结工艺对牙科纳米氧化锆陶瓷材料的烧结密度,维氏硬度以及显微结构的影响,探索微波二次烧结牙科纳米氧化锆的烧结工艺。方法：将制作的30片氧化锆圆片试件随机分为实验组和对照组,每组15片。对照组按厂家推荐烧结程序进行常规二次烧结,实验组采用微波二次烧结。烧结后每组试件内6片用于测量氧化锆的烧结密度,6片用于测量氧化锆的维氏硬度,3片用于氧化锆的电镜扫描,实验组和对照组测试结果分别进行对比。结果：微波二次烧结的牙科纳米氧化锆材料的密度,维氏硬度均高于常规二次烧结的氧化锆,结果具有统计学意义（P〈0．05）,扫描电镜（SEM）下观察到微波二次烧结的牙科纳米氧化锆材料晶粒排列更紧密,晶体颗粒更小。结论：微波二次烧结工艺能够应用于牙科氧化锆陶瓷的二次烧结,缩短了牙科氧化锆陶瓷烧结时间,优化了牙科纳米氧化锆陶瓷材料的部分机械性能。