Marginal adaptation and performance of bioactive dental restorative materials in deciduous and young permanent teeth.

The aim of this study was to investigate the adaptation of different types of restorations towards deciduous and young permanent teeth. Class V cavities were prepared in deciduous and young permanent teeth and filled with different materials (a conventional glass-ionomer, a resin-modified glass-ionomer, a poly-acid-modified composite resin and a conventional composite resin). Specimens were aged in artificial saliva for 1, 6, 12 and 18 months, then examined by SEM. The composite resin and the polyacid-modified composite had better marginal adaptation than the glass-ionomers, though microcracks developed in the enamel of the tooth. The glass-ionomers showed inferior marginal quality and durability, but no microcracking of the enamel. The margins of the resin-modified glass-ionomer were slightly superior to the conventional glass-ionomer. Conditioning improved the adaptation of the composite resin, but the type of tooth made little or no difference to the performance of the restorative material. All materials were associated with the formation of crystals in the gaps between the filling and the tooth; the quantity and shape of these crystals varied with the material. Resin-based materials are generally better at forming sound, durable margins in deciduous and young permanent teeth than cements, but are associated with microcracks in the enamel. All fluoride-releasing materials give rise to crystalline deposits

Development and optimization of ketoconazole oral strips by means of continuous hot-melt extrusion processing

Objectives The aim of this study was to develop mucoadhesive oral strips using hot-melt extrusion as a continuous manufacturing process. Methods Powder blends of ketoconazole, a water-insoluble drug – either hydroxypropyl methylcellulose (HPMC) or soluplus (SOL), sorbitol (SRB) and magnesium aluminometasilicate (MAS) were extruded to manufacture thin strips with 0.5-mm thickness. The presence of the inorganic metasilicate facilitated smooth processing of the extruded strips as it worked as an absorbent directly impacting on the extensive mixing of the drug/excipients inside the extruder barrel. Key findings The use of MAS also favoured the rapid hydration, swelling and eventual disintegration of the strips. Differential scanning calorimetry and transmission X-ray diffraction analysis revealed the existence of the amorphous drug within the extruded strips. Scanning electron microscopy and energy dispersive X-ray undertaken on the formulations showed a homogeneous drug distribution within the extruded strips. Conclusion The strips produced via continuous hot-melt extrusion processing showed significantly faster release of ketoconazole compared to the bulk drug substance

Bone healing following different types of osteotomy: Scanning electron microscopy (SEM) and three-dimensional SEM analyses

The aim of the present study was to compare dynamics of the bone healing process after different types of osteotomies. In total, 24 Wistar rats were subjected to different types of osteotomy performed with standard steel bur, piezosurgery, contact, and non-contact Erbium:yttrium-aluminum-garnet (Er:YAG) laser ablation. The animals were randomly divided into four groups, to be euthanized immediately after the procedure, or at 1, 2, or 3 weeks after surgery. The obtained bone samples were analyzed by scanning electron microscopy (SEM). Immediately after surgery, there were significant differences in the appearance of the bone defects, with presence of bone fragments and debris after standard steel bur preparation, compared with the clean smooth walls and relatively sharp edges in all other groups. The initial bone formation in defects prepared by piezosurgery was observed to be the most rapid. After 3 weeks, all bone defects were completely restored; although, differences in the healing pattern were noted, with a modest initial delay in healing after laser preparation. The first stage of the bone healing process was delayed when contact and non-contact Er:YAG laser modes were used and accelerated by piezosurgery; however, the results after 3 weeks demonstrated similar restitution of defects in all tested groups

Ostracod diversity and sea-level changes in the Late Cretaceous of southern England

The available data of ostracod ranges for the Cenomanian, Campanian and Maastrichtian stages of the Late Cretaceous of the northern part of the Anglo-Paris Basin were examined and combined with new data from the Turonian, Santonian and Coniacian stages. A new cumulative species diversity curve is presented for the Ostracoda of the Late Cretaceous of Britain. The results obtained challenge the method of chronoecologic charts to determine sea-level from diversity. When a more complete data set is applied, and compared with published sea-level curves, the result is the inverse of that previously predicted by employing chronoecologic charts. A model is presented of changing sea-levels in S.E. England from the Cenomanian through to the Santonian, which integrates the new diversity data with published sea-level changes and curves of stable isotopes of oxygen and carbon. In the earliest Cenomanian, low diversity is associated with a deeper water depositional environment and warmer temperatures. The mid-Cenomanian diversity maximum corresponds to a regressive trough and cooler water. Over the Cenomanian– Turonian boundary interval the diversity minimum is correlated with global sea-level and temperature maxima. The proportion of ostracods possessing eye tubercles falls to a minimum over this period. After the diversity crash, the Cenomanian fauna was replaced by the new Turonian fauna; east–west migrations into the Anglo-Paris Basin were facilitated by the sea-level rise overcoming marginal basin highs. The pattern seen in the mid-Cenomanian is also present at the Turonian–Coniacian boundary interval; that of high diversity corresponding with a regressive trough on a long-term regressive trend with cooling conditions. The model for this northern part of the Anglo-Paris Basin then associates high diversity with regressive cooler conditions, and low diversity with deeper and warmer water

Letters to the editor: "Milankovitch cycles and microfossils: Principals and practice of palaeocological illustrated by Cenomanian chalk-marl Rhythms" by C.R. Paul - a comment

</jats:p

Interactions of aqueous Cu, Zn and Pb ions with crushed concrete fines

The crushing of reclaimed concrete-based demolition waste to produce recycled aggregate gives rise to a large volume of cement-rich fine material for which market development would be beneficial. It was envisaged that this fine fraction may prove to be an effective sorbent for aqueous heavy metal species by virtue of its ion exchangeable phases and high pH. A batch sorption study confirmed that crushed concrete, in the particle size range 1–2 mm, successfully excluded Cu2+ (35 mg g−1), Zn2+ (33 mg g−1) and Pb2+ (37 mg g−1) from aqueous media. Subsequent distilled water leaching of the metal-laden concrete particles indicated that 1.9, 0.9 and 0.2% of the bound metals, Cu2+, Zn2+ and Pb2+, respectively, were readily soluble. Scanning electron microscopy revealed that the removal of Cu2+ and Zn2+ arose from surface precipitation reactions, whereas, the principal mechanism of uptake of Pb2+ was found to be by diffusion into the cement matrix. The metal ion removal efficiency of crushed concrete fines is compared with those of other low cost sorbents and potential applications which may exploit this sorptive property are also discussed

The Platycopid Signal deciphered: Responses of ostracod taxa to environmental change during the Cenomanian-Turonian Boundary Event (Late Cretaceous) in SE England

A multi-proxy investigation of the Cenomanian–Turonian Boundary Event (CTBE) near Dover in southern England previously demonstrated that, coincident with a major global positive carbon stable-isotope excursion during Oceanic Anoxic Event 2 (OAE 2), the diversity of nanoplankton, dinoflagellates, planktonic and benthonic foraminifera and ostracods was severely reduced. This was attributed to decreasing levels of dissolved oxygen, consequent on an intensification and expansion of the oceanic Oxygen Minimum Zone (OMZ) into shelf seas. In the case of the ostracods, it was noted that as podocopid taxa became locally extinct, platycopids became the dominant component of the fauna. Subsequently the “Platycopid Signal” Hypothesis (PSH) claimed that dominance of platycopids in ostracod assemblages could be regarded as a signal of dysaerobic conditions on the sea floor, based on the premise that the filter-feeding platycopids, able to pass more water over their respiratory surface, were better-equipped than other benthonic ostracods to survive in water of reduced oxygen concentration. The PSH has been widely accepted and applied in palaeoenvironmental reconstructions of stratigraphic intervals ranging from the Palaeozoic to the Quaternary. However, the modern biological and ecological support claimed for the Platycopid Signal has been challenged; platycopids are occasionally dominant in modern OMZs, but often they are not, and in any case the same can be said about some podocopids. Apparently precise calibration scales published by some authors are not justified by available data; furthermore, Platycopid Signal indications of dysaerobic intervals in the English Chalk succession often conflict with the evidence of macrofossils and trace fossils. Here we review old and new data from two CTBE sites in SE England, Dover and Eastbourne, and advance an alternative interpretation of the Platycopid Signal, based on the concept of the spread of oceanic oligotrophic conditions into the European Chalk Sea during OAE2. We propose that ostracod assemblages overwhelmingly dominated by platycopids signify oligotrophy, because living platycopids appear to be adapted to filter-feed on nano- and picoplankton which are predominant in oligotrophic conditions

A Preliminary Study of the Water Movement Across Dentin Bonded to Glass-Ionomer Cements

Svrha ovog istraživanja bila je ispitati kako djeluje pomicanje vode po površini dentina vezanog za konvencionalne stakleno-ionomerne cemente. Materijal i postupci: Na ekstrahiranim trećim molarima bili su pripremljeni kaviteti petog razreda ispunjeni konvencionalnim stakleno-ionomernim cementom Fuji IX. Zatim je dio uzoraka bio jedan mjesec uronjen u umjetnu slinu, a dio 18 mjeseci. Nakon toga roka razrezani su longitudinalno i analizirani SEM-om (sekundarnim i „backscattered“ načinom) te EDAX-om. Rezultati: Nakon 18 mjeseci u materijalu su bile uočene sferične strukture kod spoja tvrdog dentina. Prazni prostori u blizini spoja tradicionalnih stakleno-ionomera i dentina uglavnom su bili u obliku „ljuske jajeta“ (iako je bilo i čvrstih). To je najvjerojatnije rezultat daljnjeg stvrdnjavanja u praznim prostorima originalnog polialkenoatnog matriksa, a događa se zbog difuzije vode iz vlažnog dentina. EDAX-ovom analizom potvrđeno je da su te formacije sastavljene od velike količine stroncija, silikata i aluminijia. Zaključak: Opisane sferične formacije mogle bi poboljšati kompresivne snage uočene kod starijih ispuna s konvencionalnim stakleno-ionomernim cementom.Objectives: The purpose of this study was to examine the effects of the water movement across dentin bonded to conventional glass-ionomer cements. Material and method: Class V cavities were prepared on extracted permanent third molar teeth, filled with conventional glass-ionomer cement Fuji IX and stored in artificial saliva for one and 18 months. After the storage time interval, the teeth were sectioned longitudinally and examined by SEM (in secondary and backscattered electron mode) and EDAX. Results: Spherical structures were noted in the material adjacent to the interface with the hard dental substances after 18 months. The air voids found next to the interface between the traditional glass-ionomer cements and dentin are mainly “egg-shell-like” (although, solid ones were also found). They are probably a result of the continuation of the setting reaction in the air voids of the original polyalkenoate matrix, which appears because of water diffusion from the humid dentin. The EDAX analysis proved that these formations consist of high quantity of strontium, silica and aluminium. Conclusions: The described spherical formations may lead to improvement of the compressive strength, which is found in old restorations with conventional glass-ionomer cements

The geology and geomorphology of the Beacon Cottage Farm Outlier, St Agnes, Cornwall

The mid-Oligocene sediments forming the Beacon Cottage Farm Outlier at St Agnes, Cornwall, have a stratigraphical and geomorphological importance which is out of all proportion to their modest residual bulk (some 300000 m3). During 1986-8 61 holes were sunk into the area surrounding Beacon Cottage Farm; many penetrated the Palaeozoic floor beneath the outlier. Collectively, these show that the outlier mostly covers rotten granite and Killas. The sub-Oligocene unconformity is uneven and varies in altitude by at least 20 m. The local Bovey Formation succession comprises two members: Basal Sand, which is often pebbly, and sandy silts, known commercially as Candle Clay, the whole totalling a maximum of 8.9 m. There is indirect evidence either that slopes on the rotted Palaeozoic floor locally exceed 45° or that several post-mid-Oligocene faults affect the outlier. We conclude that the Beacon Cottage Farm sediments probably represent aeolian, colluvially and fluvially redistributed rotten rock residues, formed locally during a break in the long period of late-Palaeogene subtropical weathering and pediplanation. The outlier is considered in relation to the geomorphological evolution of the Cornubian Massif