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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin-dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives.
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PMID:A challenge to the conventional wisdom that simultaneous etching and resin infiltration always occurs in self-etch adhesives. 1536 92

The morphologic correlates of bond degradation in self-etching primers have not been fully elucidated. We hypothesized that there is no difference between the mechanism of degradation of self-etching primers in vivo and in vitro. Class I cavities prepared in vivo in 24 caries-free human molars were bonded with Clearfil SE Bond or Clearfil Protect Bond, and restored with resin composites. Eight teeth were extracted after 24 hrs, and the rest after 1 yr. The same protocol was repeated in vitro with extracted molars. Degradation of resin-dentin bonds was assessed by microtensile bond testing and TEM of interfaces after tracer immersion. Both in vivo and in vitro bond strengths decreased with time for SE Bond but not for Protect Bond, with more pronounced water treeing observed in the former adhesive under both aging conditions. There is no difference between the mechanism of degradation of self-etch adhesives in vivo or in vitro.
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PMID:Ultrastructural correlates of in vivo/in vitro bond degradation in self-etch adhesives. 2059 Sep 75

This study evaluated the microtensile bond strength and the interfacial morphology of newer adhesives. The occlusal surfaces of extracted teeth were ground flat for random allocation to four equal groups. Resin composite was bonded to each surface using either Clearfil SE Bond [SEB], Clearfil Protect Bond [PB], G-Bond [GB], or an experimental adhesive, SSB-200 [SSB]. After storage for 24 h in water at 37 degrees C, they were sectioned into beams (cross-sectional area 1 mm(2)) for microtensile bond strength testing (muTBS) at a crosshead speed of 1 mm/min. The load at failure of each was recorded; the data were analyzed by one-way ANOVA and Games Howell tests. The surfaces of the fractured specimens were observed using SEM. For the ultra-morphology of the interface, the occlusal surfaces of four more teeth were prepared as before and a thin layer of flowable resin composite was bonded to each surface using one of the four adhesives. The mean muTBS ranged from 39.68 MPa (GB) to 64.97 MPa (SEB). There were no statistical differences between SEB and SSB, or between PB and GB (p > 0.05). The muTBS of SEB and SSB were significantly greater than that of PB and GB (p < 0.05). SEMs of the fractured surfaces revealed a mixed (cohesive/interfacial) failure. TEM examination highlighted differences in the hybrid layer; SEB had a thicker layer than the others. In conclusion, the newer all-in-one adhesives produced a thin hybrid layer but varied in their bond strengths. The 2-step self-etching adhesives do not necessarily produce higher bond strengths than that of the all-in-one systems.
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PMID:Bonding characteristics of newly developed all-in-one adhesives. 1676 24

The aims of this study were to evaluate the ultimate tensile strength (UTS) and elastic modulus (E) of adhesives, and primer/adhesive mixtures after aging for 6 months in water or oil; and to compare silver uptake patterns under the TEM. A one-step self-etching adhesive (One-up Bond F: OB), two two-step self-etching primers (SE Bond: SE and Protect Bond: CP), and two etch-and-rinse systems (Single Bond: SB and Prime&Bond NT: PB) were used. Bonding and primer solutions of self-etching systems were also mixed (SE+P and CP+P). Most adhesives presented decreased UTS after water-storage. Similar or increased UTS was observed after oil storage. Except for SB, E values did not change after water-storage, but they increased after storage in oil. OB, CP+P and SE+P presented more silver uptake. The effects of water-storage were material-dependent, and significantly affected the mechanical properties and silver uptake patterns of adhesives.
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PMID:Effects of water-storage on the physical and ultramorphological features of adhesives and primer/adhesive mixtures. 2109 54