Ordering behaviors and age-hardening in experimental AuCu-Zn pseudobinary alloys for dental applications

Age-hardening mechanisms and related ordering behaviors of the experimental (AuCu)_1−xZn_x alloys with x0.2 were investigated for dental applications. The addition of Zn to equiatomic AuCu greatly increased the age-hardening rate and delayed overaging. It was suggested that the quenched-in excess vacancies were greatly related to the age-hardening rate in the AuCu–Zn pseudobinary alloys. In these alloys, the hardness became maximum during the very initial stage of ordering, and with the development of ordered phase, the hardness began to decrease. Transmission electron microscopy revealed that the age-hardening of AuCu–Zn pseudobinary alloys is caused by lattice distortion that occurred during the very early stage of atomic ordering. The addition of Zn to AuCu effectively increased the density of antiphase boundaries per unit volume of the AuCu II superstructure. This is suggested to be the main cause for the retardation of the overaging in the alloys containing Zn of 5 at% or more. This pronounced effect of Zn addition to AuCu alloy on its age-hardening characteristics may be advantageous for obtaining stable mechanical properties of dental casting gold alloys.     

Quantification of dentine shape in anthropoid primates

The external shape and thickness of the enamel component of primate molars have been employed extensively in phylogenetic studies of primate relationships. The dentine component of the molar crown also has been suggested to be indicative of phylogenetic relationships, but few studies have quantified dentine morphology in order to evaluate this possibility. To explore the utility of dentine shape as an indicator of phylogenetic affinity, a two-dimensional geometric morphometric analysis (EDMA-II) was performed using nine homologous land-marks on a sample of sectioned maxillary molars of extant ceboid, cercopithecoid, and hominoid primates. Results indicate that dentine shape (the configuration of the enamel-dentine junction, or EDJ) can distinguish taxa at every taxonomic level examined, including superfamilies, subfamilies, and closely related genera and species. This supports the idea that dentine morphology may be useful for phylogenetic studies. It is further suggested that the morphology of the EDJ may be more conservative than enamel morphology, and perhaps better-suited to phylogenetic studies. Among the samples studied, cercopithecoid primates have a unique dentine shape, and it is suggested that the development of bilophodont molars may be related to the distinctive EDJ configuration in cercopithecoids.     

Die Magnetresonanztomographie in der Dentalradiologie (Dental-MRT)

Zusammenfassung Ziel dieses Beitrags ist die Vorstellung der Untersuchungsm?glichkeiten des Ober- und Unterkiefers mittels Magnetresonanztomographie (Dental-MRT) und ihre Anwendung bei der Diagnose zahnmedizinischer Erkrankungen. Sieben gesunde Probanden, 5 Patienten mit Pulpitis, 9 Patienten mit dentogenen Zysten, 5 Patienten nach Zahntransplantationen und 12 Patienten mit atrophem Unterkiefer wurden untersucht. Axiale T1- und T2-gewichtete Gradientenecho- und Spinecho-Sequenzen in 2D und 3D-Technik wurden durchgeführt. Nach der Untersuchung wurden zus?tzliche Panoramaschnitte und orhoradiale Rekonstruktionen des Ober- und Unterkiefers, unter Verwendung einer gebr?uchlichen Dental-Software, angefertigt. Der gesamte Ober- oder Unterkiefer, Z?hne, Pulpa und der Inhalt des Mandibularkanals k?nnen gut dargestellt werden. Patienten mit einer Entzündung der Zahnwurzel k?nnen ein deutliches Knochenmarks?dem in der Periapikalregion zeigen. Bei Patienten mit odontogenen Zysten ist die Beziehungen zu den umgebenden Kieferstrukturen gut darstellbar. Nach Kontrastmittelgabe zeigt sich ein Enhancement in der Zahnpulpa. Die Dental-MRT ist ein nützliches Verfahren zur anatomischen Darstellung des Kieferbereichs und zahnmedizinischer Erkrankungen.      

Immunocytochemical localization of aromaticl-amino acid decarboxylase and catechol-O-methyltransferase in blood vessel wall of the human dental pulp

Relatively large amounts of DOPA as compared with the concentration of norepinephrine are found in human dental pulp. AADC and COMT are localized in blood vessel walls of human dental pulp. This localization suggests a functional relationship between COMT and AADC with regard to the metabolism of DOPA.     

错畸形牙弓形态的模拟及比较

目的 :比较不同类型错牙合畸形的牙弓形态。方法 :采用三维测量仪精密测量正常牙合及 4组不同类型错牙合(ClassⅠ双颌前突、ClassⅡ1、ClassⅡ2 、ClassⅢ )的原始模型 ,圆锥曲线模拟其牙弓形态。结果 :不同类型错牙合牙弓形态的差异有显著性 ,甚至某些分组的上下颌之间牙弓形态的差异也有显著性。结论 :临床上弯制弓丝时采用单一的标准牙弓形态是不完全科学的 ,应考虑错牙合的不同类型及其矫治前不同的牙弓形态以防止畸形复发。     

妊娠期大鼠摄入氟化物对子代鼠血液和骨氟浓度的影响

目的:观察孕期大鼠摄入不同剂量的氟之后,对子代鼠血液和骨氟浓度及软骨细胞和骨关节结构的影响,以探索通过妊娠期母体给氟预防乳牙龋齿的新途径。方法:给妊娠SD大鼠分别用N aF按1 m g/kg体重、10 m g/kg体重和50 m g/kg体重灌胃至分娩,并用0.9%N aC l灌胃作为对照组。结果:①实验组各组子鼠血清中的氟化物含量均较对照组高(P<0.01);并且与母鼠摄入的氟剂量呈正相关。②在中、高剂量组子鼠上肢骨骨氟的含量明显高于对照组。③在高剂量组子鼠的上肢骨切片中可见软骨细胞和关节结构的破坏。结论:①妊娠期母体摄入的氟化物可进入其子体体内。②当母鼠摄入的氟化物剂量过高时,可引起骨组织的毒性损害。     

不同表面处理的种植入早期表面沉积物的分析研究

目的：比较两种不同表面处理的种植体在植入早期表面沉积物的差异及其骨组织反应。方法：将表面经双重酸-双氧水热处理和双重酸处理的种植体分别植入兔子胫骨内，然后，采用带能谱分析的扫描电镜观测2、4、8周带种植体的骨组织。结果：植入2周后在两组种植体表面均沉积富含钙磷层；4周时这层结构大部分消失，但双重酸-双氧水-热处理组可见较多的骨生成细胞附着在种植体表面并形成新骨。8周时两组种植体表面均附着一些新骨，但以双重酸-双氧水-热处理组相对较多。结论：两组种植体在植入早期表面均可形成富含钙磷层。     

Effects of Different Over – the - Counter Whitening Products on the Microhardness,Surface Roughness,Color and Shear Bond Strength of Enamel

ObjectiveThe purpose of this in vitro study was to evaluate the effects of four over-the-counter (OTC) whitening products on the microhardness, surface roughness, color, shear bond strength (SBS) and surface charecteristics of human enamel compared with a product used for dentist-supervised home whitening.Materials and methodsSeventy eight enamel specimens allocated into 6 groups (n=13): 1-Opalescence PF 10% (OP) dentist prescribed home whitening product, 2-Opalescence Go prefilled tray (PT), 3-Opalescence Whitening Toothpaste (WT), 4-Listerine Healthy White whitening mouth rinse (WMR), 5-Cavex Bite&White whitening pen (WP) and 6- no treatment (Con). The microhardness (VHN), surface roughness (Ra) and color of the specimens were measured (T₀). The specimens were then subjected to whitening protocols for 14 days (T₁.) followed by artificial saliva storage for 14 days (T₂). The measurements were repeated at T₁ and T₂. The SBS test was done after the application of 35% phosphoric acid (Scotchbond Universal Etchant), followed by a universal adhesive (G-Premio Bond) and a micro hybrid/universal resin composite (Essentia) into a Teflon tube attached to the enamel surface (p<0.05). Surface morphologies of the enamel surfaces were examined by SEM. p value was set at 0.05ResultsApplication of OP, PT and WP decrased the microhardness of enamel specimens (p<0.05) whereas, no significant changes were seen in the microhardness of enamel specimens treated with WT and WMR (p>0.05). Ra values of enamel specimens increased with the application of OP, PT and WT (p<0.05); whereas no changes were observed after the applications of WMR and WP (p>0.05). OP, PT, WMR, and WP changed the color of the enamel(p<0.05). There were not any significant differences among the SBSs groups, apart from OP applied enamel specimens. OP showed the least SBS values (p=0.001). SEM observations revealed smooth enamel surfaces.ConclusionsThe whitening products affected the microhardness, surface roughness, color of enamel differently. Only OP decreased the SBS of the enamel.     

添加＂正圆形标记＂后对印模形变规律的影响

目的 探索添加＂正圆形标记＂后对印模固有形变规律的影响.方法 按美国牙科协会ADA标准,制作两个金属母模,并在其中1个上安置6根横断面为正圆形的钢针.分别对两个金属母模制取印模,获得A、B两组印模样本.用测量显微镜观察、测量标记线,比较两组印模的形变程度及规律.所获数据采用SAS 6.12软件的成组t检验比较.结果 A、B两组印模的形变范围分别为,藻酸盐0.38%～0.58%和0.43%～0.66%;硅橡胶0.38%～0.42%和0.33%～0.49%,两组之间差异无统计学意义（P〉0.05）.结论 在口腔印模上添加正圆形标记点,不会影响印模本身固有的形变规律,该标记方法是可行的.