种植体钛基台和全瓷冠间粘接界面的三维有限元应力分析

目的：观察钛基台支持时四种粘接剂和3种全瓷冠间不同粘接界面的应力分布情况。方法：建立下颌第一磨牙种植体局部结构的三维有限元模型,模拟最大咬力在冠咬面加载水平和垂直力。结果：磷酸锌粘接界面的应力最大;铸瓷冠可以降低粘接界面的应力大小;粘接界面的应力受粘接剂的影响最大;水平加载最大应力远大于垂直加载;弹性应变主要集中在基台与种植体和冠颈部连接处。结论：粘接界面应力过大应首先考虑更换粘接剂,其次考虑面侧向力过大或不平衡,最后考虑修复冠材料。基台与种植体和冠颈部连接处最可能发生折断。三维有限元法应力分析可以为种植修复提供较准确的理论依据,对临床工作准备和预期都具有重要的指导意义。     

自酸蚀粘接技术在外伤牙固定中的应用

为了提高外伤牙的治疗有效率, 作者采用自酸蚀粘接剂-扁钢丝-树脂共同构成粘接性夹板,用于固定外伤后松动或脱位的患牙,取得了良好的效果.     

Dopamine and Oxytocin Interactions Underlying Behaviors: Potential Contributions to Behavioral Disorders

Dopamine is an important neuromodulator that exerts widespread effects on the central nervous system (CNS) function. Disruption in dopaminergic neurotransmission can have profound effects on mood and behavior and as such is known to be implicated in various neuropsychiatric behavioral disorders including autism and depression. The subsequent effects on other neurocircuitries due to dysregulated dopamine function have yet to be fully explored. Due to the marked social deficits observed in psychiatric patients, the neuropeptide, oxytocin is emerging as one particular neural substrate that may be influenced by the altered dopamine levels subserving neuropathologic‐related behavioral diseases. Oxytocin has a substantial role in social attachment, affiliation and sexual behavior. More recently, it has emerged that disturbances in peripheral and central oxytocin levels have been detected in some patients with dopamine‐dependent disorders. Thus, oxytocin is proposed to be a key neural substrate that interacts with central dopamine systems. In addition to psychosocial improvement, oxytocin has recently been implicated in mediating mesolimbic dopamine pathways during drug addiction and withdrawal. This bi‐directional role of dopamine has also been implicated during some components of sexual behavior. This review will discuss evidence for the existence dopamine/oxytocin positive interaction in social behavioral paradigms and associated disorders such as sexual dysfunction, autism, addiction, anorexia/bulimia, and depression. Preliminary findings suggest that whilst further rigorous testing has to be conducted to establish a dopamine/oxytocin link in human disorders, animal models seem to indicate the existence of broad and integrated brain circuits where dopamine and oxytocin interactions at least in part mediate socio‐affiliative behaviors. A profound disruption to these pathways is likely to underpin associated behavioral disorders. Central oxytocin pathways may serve as a potential therapeutic target to improve mood and socio‐affiliative behaviors in patients with profound social deficits and/or drug addiction.     

Effect of time on tensile bond strength of resin cement bonded to dentine and low-viscosity composite

OBJECTIVES: The purpose of this study was to evaluate the tensile bond strength (TBS) of Panavia F resin cement (PF) applied on dentine pre-treated with ED Primer (ED) and Clearfil Liner Bond 2V (CLB) coated with a layer of low-viscosity composite Protect Liner F (PLF) at 10 min, 24 h and 12 months after curing. METHODS: The labial surfaces of 60 bovine lower incisors were ground to obtain a flat dentine surface, allowing a demarcation of a 4.0 mm-diameter area with adhesive tape. The teeth were randomly divided in six groups; ED was applied in groups A I, A II and A III and CLB was applied, followed by PLF, in groups B I, B II and B III. A resin composite rod with a wire loop was luted directly to the prepared surface of each group with PF. The specimens of groups A I and B I were submitted to TBS test after 10 min. Groups A II and B II were submitted to TBS test after 24 h storage and groups A III and B III were submitted to TBS test after 12 months storage. Each specimen was inspected by SEM and classified according to the failure mode. Additionally, two representative specimens of each failure mode were sectioned for a composite/dentine interface SEM evaluation. RESULTS: No significant statistical differences were observed among the groups at 10 min and 24 h. Groups A III and B III presented the lowest TBS values (p<0.05) after 12 months storage. PF on resin-coated dentin (PLF) showed the highest TBS values and was statistically different to PF on dentine for all the groups. The fracture pattern was generally cohesive on the adhesive/hybrid layer for groups A I, A II and A III and cohesive on composite resin for B I, B II and B III. SIGNIFICANCE: The use of a less hydrophilic self-etching system to pre-treat dentine, coating with a low-viscosity composite layer prior luting with resin cement, may provide a protection of the hybridised complex, allowing a dentine seal during the 12 months storage period.     

Maternal bond and mother–child interaction in severe postpartum psychiatric disorders: Is there a link?

Summary Mothers in the puerperium are vulnerable to a wide spectrum of postpartum psychiatric disorders. One of the central psychological processes of the puerperium is the development of an emotional relationship with the baby. The bond to the infant as well as the interaction with the baby are two aspects of the mother–infant relationship that can be disturbed by mothers with postpartum psychiatric disorders. Dysfunctional maternal cognitions may also influence the development of an emotional bonding and the establishment of a positive interaction with the child. The aim of this study is to investigate differences in the self-perceived experience of bonding and the observed mother–child interaction of severely ill postpartum depressive and psychotic mothers. In addition the association between subjective experience of bonding and objective measurement of mother–child interaction will be described. Results show that depressive mothers perceived their bonding to the baby more negatively than psychotic mothers. No differences could be found in the objective interactional behaviour of the mothers in both groups, with the exception that the infants of psychotic mothers showed more eye contact avoidance towards their mothers. The subjective experience of motherhood clearly influences the maternal interactional behaviour with depressive mothers as well as with psychotic mothers.     

Influence of Natural Bovine Enamel Roughness on Bond Strength after Etching

Objective:To determine and compare the longitudinal and transverse roughness parameters of the enamel surface of bovine teeth and evaluate the influence of these parameters on bond strength.Materials and Methods:Ninety bovine incisors were used. The surface roughness of enamel was measured with a profilometer. For each tooth, five readings were taken in the longitudinal plane and five were taken in the transverse plane of the long axis of the tooth in an area equal to the size of the bracket base. The metal brackets were bonded with Transbond XT, and bond strength was evaluated in a universal test machine.Results:There was a statistical correlation (P < .01) between the longitudinal and transverse roughness measurements. There was no correlation between roughness measurements (longitudinal and transverse) and bond strength (P > .05), nor was there a correlation between total roughness (longitudinal Ra and transverse Ra) and bond strength. The Student''s t-test showed that there was a statistically significant difference (P < .05) between longitudinal and transverse roughness.Conclusion:The transverse roughness is greater than the longitudinal roughness, there is a strong correlation between longitudinal and transverse roughness, and there is no correlation between enamel roughness and bond strength.     

Grape seed proanthocyanidins increase collagen biodegradation resistance in the dentin/adhesive interface when included in an adhesive

Objectives

Contemporary methods of dentin bonding could create hybrid layers (HLs) containing voids and exposed, demineralised collagen fibres. Proanthocyanidins (PA) have been shown to cross-link and strengthen demineralised dentin collagen, but their effects on collagen degradation within the HL have not been widely studied. The purpose of this study was to compare the morphological differences of HLs created by BisGMA/HEMA model adhesives with and without the addition of grape seed extract PA under conditions of enzymatic collagen degradation.

Methods

Model adhesives formulated with and without 5% PA were bonded to the acid etched dentin. 5-μm-thick sections cut from the bonded specimens were stained with Goldner's trichrome. The specimens were then exposed to 0.1% collagenase solution for 0, 1, or 6 days. Following collagenase treatment, the specimens were analysed with SEM/TEM.

Results

Staining did not reveal a difference in the HLs created with the two adhesives. SEM showed the presence of intact collagen fibrils in all collagenase treatment conditions for specimens bonded with adhesive containing PA. These integral collagen fibrils were not observed in the specimens bonded with adhesive without PA after the same collagenase treatment. TEM confirmed that the specimens containing PA still showed normal collagen fibril organisation and dimensions after treatment with collagenase solution. In contrast, disorganised collagen fibrils in the interfacial zone lacked the typical cross-banding of normal collagen after collagenase treatment for specimens without PA.

Conclusions

The presence of grape seed extract PA in dental adhesives may inhibit the biodegradation of unprotected collagen fibrils within the HL.     

Bonding and bridging neighborliness: An individual-level study in the context of health

Although previous research provides a compelling picture of social capital's role in predicting health outcomes, only a modicum of research has tested the more detailed roles of the dimensions of bonding and bridging social capital, with no research focusing exclusively on bonding and bridging neighborliness or ethnicity. To help fill this gap in the literature, the current study measures individual-level bonding and bridging neighborliness for four U.S. ethnic groups—and then, with cross-sectional data from a 2007 national telephone survey of U.S. adults, employs ordinal logistic regression and OLS regression to test the individual-level predictors of self-rated health and stress, when controlling for BMI and demographics. Bonding neighborliness was associated with self-rated health and inversely associated with stress, whereas bridging neighborliness was not significantly linked to either health outcome. When also controlling for neighborhood composition, the bonding neighborliness findings remained generally consistent, while the association between bridging neighborliness and self-rated health gained significance. These results indicate the protective effects that bonding neighborliness can have on health outcomes, as well as the more modest protective effects of bridging neighborliness. These findings have implications for future research and practice, highlighting the potential of health interventions and policies that target the development of bonding social capital.     

Effect of Surface Preparation on the Failure Load of a Highly Filled Composite Resin Bonded to a Denture Base Resin

Purpose: The purpose of this study was to evaluate the effect of the surface preparation on the maximum fracture load value of a highly filled gingival shade composite resin bonded to a denture base resin. Materials and Methods: Block specimens were prepared from a heat‐processed denture base resin and divided into five groups. The flat surfaces of the specimens were abraded with 400‐grit silicon carbide paper, then prepared in one of the following ways: (1) without preparation (group 1); (2) application of silane coupling agent (group 2); (3) application of dichloromethane (group 3); (4) application of dichloromethane following the silane coupling agent (group 4); or (5) tribochemical silica coating (group 5). A highly filled gingival shade composite resin was applied (area Ø= 5 mm) and polymerized with a light polymerizing unit. Specimens made entirely of heat‐processed denture base resin were also fabricated as references (group 6). The halves of the specimens of groups 4, 5, and 6 were thermocycled up to 10,000 times in water between 5°C and 55°C with a 1‐minute dwell time at each temperature. Shear testing was performed in a universal testing machine at a crosshead speed of 1 mm/min, and the maximum fracture load values were determined (n = 10). Results: The maximum fracture load values of the highly filled gingival shade composite resin bonded to the denture base resin for all preparation groups were significantly enhanced before thermocycling (p < 0.05). Group 5 exhibited the greatest fracture load value, followed by group 4, compared to the other groups (p < 0.05), however, the fracture load values significantly decreased for these groups after thermocycling (p < 0.05), whereas the fracture load value of group 6 did not decrease (p > 0.05). Conclusions: Tribochemical silica coating and the application of dichloromethane after the silane coupling agent were effective surface preparations for the bonding of a highly filled gingival shade composite resin to a denture base resin, however, the bond durability of these treatments may be insufficient.     

A Comparative Micro-topographic Study of the Buccal Enamel of Different Tooth Types

Abstract

The aim of this study was to perform an in vitro examination of the etch pattern achieved on the orthodontic bonding area (OBA) of different tooth types, and to compare the extent and definition of etch achieved. Six examples of each permanent human tooth type were studied. These were collected from adolescents. A standardized etch regime was employed on the OBA and the etch pattern examined under the scanning electron microscope. The degree of definition of etch achieved on every third enamel prism was evaluated. Results showed that the extent of etch achieved decreased toward the distal end of each arch and was significantly less on the first molars (covering <2% OBA) than on the incisors (covering >90% OBA). It was also noted that the degree of definition became poorer towards the distal end of the arches and was worst on the mandibular molars.

It is suggested that the etched enamel morphology of different tooth types could affect composite resin bond strengths. Consequently, this feature could effect the clinical survival of orthodontic brackets and contribute to the higher failure rate of brackets on posterior teeth.