Immediate versus water-storage performance of Class V flowable composite restoratives

Objectives The aims of this investigation were to clarify the effects of 24 h water-storage and finishing time on mechanical properties and marginal adaptation to a Class V cavity of eight modern flowable resin-composites. Methods Eight flowable composites, plus two controls (one microfilled and one hybrid composite), were investigated with specimen sub-groups (n = 10) for each property measured. The principal series of experiments was conducted in model Class V cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, each tooth was sectioned in a buccolingual direction through the center of the restoration, and the presence or absence of marginal-gaps was measured (and then summed for each cavity) at 14 points (each 0.5 mm apart) along the cavity restoration interface (n = 10 per group; total points measured = 140). The shear bond-strengths to enamel and to dentin, and flexural strengths and moduli data were also measured at 3 min and after 24 h water-storage. Results For all flowable composites, polished immediately after setting, 14–30 summed gaps were observed (controls: 64 and 42). For specimens polished after 24 h, a significantly (p &#60; 0.05) reduced number of 8–17 summed gaps occurred for only 3 flowable composites; whereas for 5 flowable composites there were non-significantly-different (p &#62; 0.05) numbers (11–17) of summed gaps (controls: 28 and 22). After 24 h storage, shear bond-strengths to enamel and to dentin, flexural strengths and moduli increased highly significantly (p &#60; 0.001) for all materials, except Silux Plus. Significance A post-cure interval of 24 h resulted in enhanced mechanical and adhesive properties of flowable dental composites. In a minority of cases there was also a reduced incidence of marginal-gap formation. However the latter effect may be partly attributed to 24 h delayed polishing, even though such a delay is not usual clinical practice.</p

Evolutionary descent of prion genes from a ZIP metal ion transport ancestor

In the more than 20 years since its discovery, both the phylogenetic origin and cellular function of the prion protein (PrP) have remained enigmatic. Insights into the function of PrP may be obtained through a characterization of its molecular neighborhood. Quantitative interactome data revealed the spatial proximity of a subset of metal ion transporters of the ZIP family to mammalian prion proteins. A subsequent bioinformatic analysis revealed the presence of a prion-like protein sequence within the N-terminal, extracellular domain of a phylogenetic branch of ZIPs. Additional structural threading and ortholog sequence alignment analyses consolidated the conclusion that the prion protein gene family is phylogenetically derived from a ZIP-like ancestor molecule. Our data explain structural and functional features found within mammalian prion proteins as elements of an ancient involvement in the transmembrane transport of divalent cations. The connection to ZIP proteins is expected to open new avenues to elucidate the biology of the prion protein in health and disease

Marginal and flexural integrity of three classes of luting cement, with early finishing and water storage

Objectives. The aims of this investigation were to clarify the effects of finishing-time and 24 h water-storage on mechanical properties and marginal adaptation to dentin of seven modern luting cements, representing three chemical types. Methods. Bistite II, Chemiace II, Compolute, XenoCem, PermaCem, Fuji Cem and Fuji Plus were investigated with specimen sub-groups (N=10) for each property measured. The principal series of experiments was conducted in dentin cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, the maximum marginal gap width and the opposing width (if any) per cavity were measured microscopically, and summed. Then the overall sum of gap-widths (per group; N=10) was calculated. Marginal gaps were similarly measured in Teflon cavities, together with shear-bond-strengths to dentin and early flexural strengths, moduli and swelling data. Results. For specimen-sets polished immediately after setting, summed marginal gaps of 23–121 &#956;m were observed, for all luting cements except Compolute. A significantly different (p&#60;0.05) result of either no gap or 6–28 &#956;m summed gap-widths occurred in specimens polished after 24 h. For all materials, their shear-bond-strengths, flexural strength and moduli significantly increased after 24 h storage. Significance. The marginal behavior can be interpreted in terms of the contributions of bonding, shrinkage, swelling and compliance of components, along with compositional features of the cements. With these types of cement it is generally inadvisable to polish the interfacial luting surface immediately after cementing. The polishing procedures should be carried out not less than 24 h later. One resin-cement was able to withstand immediate finishing.</p

Root-surface gap-formation with RMGIC restorations minimized by reduced P/L ratio of the first increment and delayed polishing

Objectives This in vitro study evaluated the effect on interfacial gap-formation around resin-modified glass–ionomer (RMGIC) root surface restorations with (a) variations in powder/liquid ratio (P/L) of the first increment of an incremental procedure, compared with a bulk restoration technique, and (b) delayed versus immediate polishing, to permit maturation. Methods Cavity preparations were placed in premolar teeth on upper facial root surfaces. Two RMGICs were studied (Fuji II LC and Vitremer), with their associated conditioner or primer, applied with an incremental technique. The P/L ratio of the first increment was reduced to fractional (normalized) values between 0.2 and 1.0 of the manufacturers' recommended P/L, and the manufacturers' P/L was used for the second increment. Control groups were bulk filled. After polishing, either: (i) immediately after light-activation or (ii) after 24 h storage, the restored teeth were sectioned in a buccolingual direction through the center of the restoration and the presence or absence of marginal gaps was measured at ×1000 magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface; (n=10; total points measured per group=140). Results For both RMGICs, significant differences (p Significance To minimize gap formation, more fluid mixes could be used especially with Fuji II LC to give improved adaptation to the dentin. Secondly, whenever possible, polishing should be delayed on the final increment to permit maturation and minimize mechanical disruption of both increments.</p

Grenville Foreland Deformation and Sedimentation in Southwest Ohio Indicated by Reprocessed Seismic Reflection Profiles near Middletown, Ohio, USA

The late Mesoproterozoic to early Neoproterozoic Middle Run Formation contains vital information about the crustal evolution of the North American Craton. Four reprocessed seismic reflection lines in the vicinity of the AK Steel facility in Middletown, Ohio, provide new insights into the structural and depositional setting of the Middle Run Formation in this region. A residual statics solution improved the resolution and coherency of reflections in these profiles that underlie the Cambrian Mount Simon Sandstone. Reprocessing revealed gently inclined, west-southwest-dipping reflectors and the occurrence of an angular unconformity between the Middle Run Formation and the overlying Paleozoic strata. The weak and discontinuous seismic reflection character of the Middle Run Formation in these seismic lines overlies a sequence of stronger parallel reflections that are like those observed on the eastward ODNR-1-88 seismic line located near core hole DGS 2627, the stratotype of the Middle Run Formation. This inferred thickness indicates that the basin in which the Middle Run Formation was deposited ranges from at least 670 to 1,128 m (2,200 to 3,700 ft) deep at the AK Steel area and dips gently west-southwest, which is in contrast with the moderate easterly dip observed on the ODNR-1-88 seismic line to the northeast. Correlation of these features across the 10 km (approximately 6 mi) cross-strike gap between the AK Steel lines and the ODNR-1-88 seismic line suggests the presence of a reverse fault with approximately 792 m (2,600 ft) of estimated vertical displacement. A regional cross section—including the WSU 1990 seismic line eastward of the ODNR-1-88 line—exhibits a faulted west-verging asymmetric syncline in near proximity to the Grenville Front. This cross section also shows that deformation of the Middle Run Formation and the underlying layered sequence exhibits a consistent tectonic style of reverse faulting and folding that developed in response to Grenville Front tectonism