Cement failure loads of 4 provisional luting agents used for the cementation of implant-supported fixed partial dentures

The major disadvantage of cement-retained implant-supported fixed partial dentures (FPDs) is difficulty in retrievability. The retentive strengths of the provisional luting agents usually employed in these cases are therefore an important consideration. This study evaluated the cement failure loads of 4 provisional luting agents used for the cementation of FPDs supported by 2 implants or 4 implants. Nogenol luting agent exhibited the lowest retentive values in both types of FPD. ImProv proved to be the most retentive cement of all tested. Temp Bond NE and Temp Bond presented significantly different values (P < .05) for the 2-implant FPD, but not for the 4-implant model. On the basis of the study results, it may be concluded that Nogenol appears to be more appropriate for cementation of both 2- and 4-implant-supported FPDs when removal of the provisionally cemented superstructure is anticipated.     

Sealing ability of a new polydimethylsiloxane-based root canal filling material

We tested the null hypothesis that there is no difference in the sealing ability of GuttaFlow, RoekoSeal, and AH26 in root canals. Sixty extracted mandibular premolars were filled with AH26 (lateral compaction), RoekoSeal, or GuttaFlow (modified single-cone). The sealing ability of the root canal fillings was measured weekly (4 weeks) by using a glucose penetration model. Kruskal-Wallis test revealed significant differences in glucose penetration between the experimental groups at weeks 1, 2, 3, and 4. Whereas GuttaFlow showed the highest amount of leakage at all times, AH26 showed the lowest. There was no significant difference between RoekoSeal-filled and AH26-filled root canals throughout the experimental period. AH26 showed better sealing ability in root canals than GuttaFlow.     

Simodont系统辅助照明条件对口腔临床技能训练的影响

目的探讨Simodont虚拟仿真系统中虚拟涡轮机机头的辅助光照对实际操作的影响，为口腔临床技能训练提供指导。 方法选取四川大学华西口腔医学院口腔医学专业本科生56人为研究对象，按随机数表法随机分为两组，实验组（虚拟仿真牙科训练机的涡轮机头的辅助灯处于打开状态）和对照组（虚拟仿真牙科训练机的涡轮机头的辅助灯处于关闭状态）的学生分别使用Simodont虚拟仿真系统在不同辅助光照情况下进行练习和考核，并在临床冷光灯条件下使用玻璃板模拟临床操作，采用t检验对比分析两组的得分。并通过问卷调查了解学生的使用体验。 结果不同辅助光照条件下，Simodont虚拟训练机操作总分（t = 1.342，P = 0.181）和临床冷光灯条件下玻璃板的操作结果（t = -0.585，P = 0.561）差异均无统计学意义；但Simodont总分构成项中"Leeway sides（洞缘偏差）"项有光组学生分数为5.38 ± 4.69，大于无光组分数（4.32 ± 2.92），差异有统计学意义（t = 2.252，P = 0.025）。 结论尚不能认为Simodont系统在有辅助灯的条件下可以影响医学生的培训效果，但在有辅助照明的情况下操作可能更容易误碰到规定区域边界的侧方。问卷结果显示，Simodont虚拟仿真系统是一种值得推广的教学模式。     

Gelatinase A (MMP-2) in developing tooth tissues and amelogenin hydrolysis

Matrix metalloproteinases (MMPs) are thought to play important roles during enamel and dentin biomineralization. Previously, membrane type-1 matrix metalloproteinase (MT1-MMP) was localized to the plasma membranes of ameloblasts and odontoblasts of the developing tooth. The best-characterized function of MT1-MMP is to initiate the activation of gelatinase A (MMP-2). Thus, we hypothesized that gelatinase A may also be expressed by developing tooth tissues. A full-length porcine gelatinase A mRNA was isolated by RT-PCR homology cloning of an enamel-organ-specific cDNA library. Northern blot and in situ hybridization analyses demonstrated gelatinase A expression in developing tooth tissues. Immunohistochemical analysis localized gelatinase A close to the plasma membrane of these tissues. Furthermore, recombinant gelatinase A was demonstrated to cleave recombinant amelogenin into several fragments of differing molecular masses. Thus, gelatinase A is expressed by developing tooth tissues along with its activator MT1-MMP and may, therefore, play an important role during tooth development.     

The distribution of nitric oxide synthetase in Vcx and its relation with the expression of FOS induced by teeth movement in rats]

It was studied the central role of nitric oxide(NO) during experimental teeth movement and the relation between nitric oxide synthetase (NOS) positive neurons and FOS like immunoreactivity (FLN) with the NADPH-diaphorase histochemistry and immunocytochemical reaction method. Results indicated that NOS positive neurons and FLN showed typical distribution in Vcx and there was some overlap between them. It suggests that NO is involved in the central modulation of the stimulating message of teeth movement, and which further explains the central modulation mechanism of experimental teeth movement in rats.     

唾液对体外培养NIH—3T3及MEC—1细胞粘附的影响

目的：探讨人唾液对正常及肿瘤细胞在体外粘附有无不同影响。方法：接种ＮＩＨ—３Ｔ３及ＭＥＣ－１细胞在预先涂有或未涂唾液的２４孔培养板上，用细胞计数法分别在接种后２、４、６和８ｈ计数贴壁细胞。结果：ＮＩＨ－３Ｔ３细胞及ＭＥＣ－１细胞在涂有唾液的塑料底物上在２、４、６、和８ｈ其贴壁抑制率分别为３５％、４１％、２６％、３４％和１０％、９％、８％、４％。结论：人全唾液能抑制体外培养的ＮＩＨ－３Ｔ３细胞的粘附，但对ＭＥＣ－１细胞的影响不大。     

A point mutation of the ED1 gene in a Japanese family with X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (EDA) is characterized by the hypoplasia or absence of hair, teeth and sweat glands. In this study, the authors investigated the ED1 gene in a Japanese family with X-linked hypohidrotic ectodermal dysplasia. The only affected male fulfils the diagnostic criteria for this disorder. His parents were not consanguineous and both of them were healthy. After informed consent, genomic DNA was isolated from the peripheral blood lymphocytes or oral buccal epithelial cells of all members of the family. A polymerase chain reaction fragment containing exon 9 of the ED1 gene was amplified using primers. The patient's amplified fragment, as well as those from his father, mother and sister, were directly sequenced. The sequence from the patient revealed a point mutation (G1149A) in exon 8 of the ED1 gene, which changes codon 291 from glycine to arginine. Heterozygosity was demonstrated in his mother and sister. This mutation has not been reported previously. The amino acid substitution is predicted to disrupt the transmembrane domain, which strongly implies that this is the disease-causing mutation in the family.     

Type II collagen and aggrecan mRNA expressions in rabbit condyle following disc displacement

The aim of this investigation was to study the remodelling of cartilage in the mandibular condyle following disc displacement (DD) of the temporomandibular joint (TMJ). Forty adult Japanese white rabbits were used in this study. The right joints of 28 of the 40 rabbits had their discs surgically displaced. Four of the 28 were killed at 4 days or 1, 2, 4, 6, 8 and 12 weeks after surgery. The messenger RNA (mRNA) expression levels of aggrecan and type II collagen in cartilages were measured using in situ hybridization techniques. Results showed that aggrecan mRNA expression reduced in the first week after DD. The expression began to recover after 4 weeks and reached a normal level after 6 weeks. Type II collagen mRNA expression reduced from 4 weeks and the expression recovered after 8 weeks. This suggests that the chondrocyte reacting to the displacement of the TMJ disc, alters its matrix gene expression patterns and it is may be the cause of the shape changes of TMJ after DD.