A temporary filling material used for coronal sealing during endodontic treatment may cause tooth fractures in large Class II cavities in vitro.

AIM: To investigate the use of a zinc oxide/zinc sulphate-based cement (Coltosol(®) F, Coltène Whaledent, Cuyahoga Falls, OH, USA) as a temporary filling material during multiple-visit root canal treatments and the occurrence of cracks within the filling material or the tooth. METHODOLOGY: Root canals of one hundred and twenty-two extracted human molars were prepared using ProTaper instruments up to size F2. After root canal preparation, standardized mesial-occlusal-distal cavities were prepared. The buccal-lingual/palatal width of the cavities was 4.5 mm), so that the remaining cavity walls had a mean thickness of 3.5 mm. Teeth were checked for cracks and fracture lines using a stereomicroscope with 10× magnification. A calcium hydroxide slurry was used as an intracanal dressing. The teeth were divided into three groups. In the Coltosol group, the cavity was filled with Coltosol(®) F. In the Coltosol-Clearfil group, a 2-mm layer of Coltosol(®) F was placed into the coronal pulp chamber, the remaining cavity was filled with Clearfil(™) . In the Clearfil group, a foam pellet was placed onto the orifices of the root canals, the remaining cavity was filled with Clearfil(™) . In the control group, the cavities were left without any filling material. The teeth were stored in water at 37 °C for 14 days and examined every 24 h under a stereomicroscope for fracture lines occurring on the tooth surface or in the filling material. RESULTS: In the Coltosol group, fractures within the filling material were observed in 28 (85%) of 33 teeth. 13 (39%) teeth had tooth fractures. Amongst these teeth, 8 (61%) had root fractures, 1 (8%) had a crown fracture and 4 (31%) had a root-crown fracture. CONCLUSION: Coltosol(®) F, when used alone as a restorative material, led to tooth fractures in Class II cavities in teeth undergoing root canal treatment. Tooth fractures may occur 4 days after placement of the filling.

[S]-AR-R 15896AR-A novel anticonvulsant: acute safety, pharmacokinetic and pharmacodynamic properties.

A rational, chemical, synthetic effort to identify promising low-affinity uncompetitive N-methyl-D-aspartic acid receptor antagonists for use as antiepileptic drugs led to the discovery of AR-R 15035AR, or [RS]-alpha-phenyl-2-pyridine-ethanamine.2HCl. Chiral separation followed by intensive in vivo screening resulted in the selection of the [S] enantiomer, AR-R 15896AR, as the best compound for further preclinical development. AR-R 15896AR prevented tonic seizures in rodents for up to 6 to 8 h in response to maximal electroshock (MES), 4-aminopyridine, bicuculline, or strychnine, as well as characteristic seizures following injections of N-methyl-DL-aspartic or kainic acids. AR-R 15896AR was ineffective in two kindling models of epilepsy, did not produce tolerance to MES, and was devoid of proconvulsant and phencyclidine-like properties in mice and rats, respectively. Therapeutic indices for AR-R 15896AR were comparable to or exceeded those for standard anticonvulsants. Orally administered AR-R 15896AR rapidly entered the rat brain and was eliminated in parallel from the plasma and plasma-free compartment. A dose-response relationship between plasma and brain levels after p.o. or i.v. administration of AR-R 15896AR and protection against MES was highly correlative. The time course for loss of protection against MES mirrored the elimination of the compound from brain and plasma. The total brain concentration (25 microM) of drug at the ED50 value (approximately 3 mg/kg) for protection against MES seizures was consistent with the reported affinity of AR-R 15896AR at the N-methyl-D- aspartic acid binding site (IC50 value = 1.3 microM). The present findings demonstrated the attractiveness of AR-R 15896AR as a candidate for further development to treat epilepsy.

Iterative design of a holographic beamformer.

A design method is presented for computing the phase functions of an energy efficient system using two holographic elements for converting a Gaussian beam into a uniform beam with rectangular support in the far field of the source. The method is based on a modification of the Gerchberg-Saxton algorithm which includes an x-y separability constraint on the phase of one of the holographic elements. A beamforming system was fabricated using this method, and experimental results were obtained which support the design approach.

Holographic polar formatting and realtime optical processing of synthetic aperture radar data.

A two holographic optical element (HOE) system for polar formatting of spotlight mode synthetic aperture radar (SAR) data was designed, fabricated, and successfully tested. With the addition of a spatial light modulator, a third phase-compensating HOE, and a Fourier transform lens, the real-time polar formatting of SAR data and SAR image formation was experimentally demonstrated.