Radiation Chemical Yields of 7-Hydroxy-Coumarin-3-Carboxylic Acid for Proton- and Carbon-Ion Beams at Ultra-High Dose Rates: Potential Roles in FLASH Effects.

It has been observed that healthy tissues are spared at ultra-high dose rate (UHDR: >40 Gy/s), so called FLASH effect. To elucidate the mechanism of FLASH effect, we evaluate changes in radiation chemical yield (G value) of 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA), which is formed by the reaction of hydroxyl radicals with coumarin-3-carboxylic acid (C3CA), under carbon ions (140 MeV/u) and protons (27.5 and 55 MeV) in a wide-dose-rate range up to 100 Gy/s.

DNA strand break induction of aqueous plasmid DNA exposed to 30 MeV protons at ultra-high dose rate.

Radiation cancer therapy with ultra-high dose rate exposure, so called FLASH radiotherapy, appears to reduce normal tissue damage without compromising tumor response. The aim of this study was to clarify whether FLASH exposure of proton beam would be effective in reducing the DNA strand break induction. We applied a simple model system, pBR322 plasmid DNA in aqueous 1 × TE solution, where DNA single strand breaks (SSBs) and double strand breaks (DSBs) can be precisely quantified by gel electrophoresis.

Significant changes in yields of 7-hydroxy-coumarin-3-carboxylic acid produced under FLASH radiotherapy conditions.

FLASH radiotherapy appears to kill off tumor cells while sparing healthy tissues, by irradiation at ultra high dose rate (>40 Gy s). The present study aims to clarify the mechanism of the sparing effect by proton irradiation under the FLASH conditions from a viewpoint of radiation chemistry. To do so, we evaluate radiation chemical yields ( values) of 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA), which is produced by water radiolysis using coumarin-3-carboxylic acid (C3CA) solution as a radical scavenger of hydroxyl radicals.

A simple algorithm for beam profile diagnostics using a thermographic camera.

A new algorithm for digital image processing apparatuses is developed to evaluate profiles of high-intensity DC beams from temperature images of irradiated thin foils. Numerical analyses are performed to examine the reliability of the algorithm. To simulate the temperature images acquired by a thermographic camera, temperature distributions are numerically calculated for 20 MeV proton beams with different parameters.

(11)CH4 molecule production using a NaBH4 target for (11)C ion acceleration.

Solid-state materials suitable for use as proton irradiation targets were investigated for producing high-purity (11)CH4 molecules for heavy-ion cancer therapy. The radioactivity of gas produced by proton irradiation was measured for several target materials. Also, the radioactive molecular species of the produced gas were analyzed by radio gas chromatography.

Impact of facial form on the relationship between conventional or implant-assisted mandibular dentures and masticatory function.

Statement Of Problem: It is not clear if the interaction of craniofacial form with type of prosthetic restoration (conventional or implant-assisted) is related to masticatory function in complete denture patients.

Purpose: The purpose of this study was to investigate the relationships among facial form, skeletal class, alveolar residual ridge heights and masticatory function in subjects treated with implant-assisted or conventional mandibular dentures with lateral cephalometric evaluation.

Material And Methods: Data from a previously reported randomized controlled clinical trial were accessed to compare treatment success rates, functional and perceptual outcomes, dietary intake, and craniofacial relationships between mandibular complete dentures and implant overdentures in edentulous diabetic subjects.

Bone quality of mandibles reconstructed with particulate cellular bone and marrow, and platelet-rich plasma.

The purpose of this study was to evaluate the bone quality of mandibles reconstructed with particulate cellular bone and marrow (PCBM) and platelet-rich plasma (PRP). We compared the bone mineral density (BMD) and microstructure of PCBM and PRP-reconstructed bone and normal bone in patients. Bone biopsies were taken of 11 samples of PCBM and PRP reconstructed bone and 16 samples of normal bone using a trephine bur.

Polishing of dental porcelain by polycrystalline diamond.

Polycrystalline diamond (PCD) exhibits excellent abrasive characteristics and is commonly used as loose grains for precision machining of hard ceramics and other materials that are difficult to grind and polish. In the present study, we investigated using bonded PCD for polishing dental porcelain, for which a lustrous surface is difficult to obtain by polishing. We compared the surface texture and characteristics of dental porcelain after polishing with bonded PCD with that obtained using bonded monocrystalline diamond (MCD), which is commonly used for this purpose.

The effect of surface roughness on the Weibull distribution of porcelain strength.

The purpose of the present study was to test the hypothesis that glazing will affect the Weibull modulus or the mean flexural strength of dental porcelain. Four groups (n = 30) of specimens were prepared from feldspathic body porcelain (Vita VMK 68). The specimens were tested in groups: original glazed condition (control), and after grinding separately with 1,000-grit, 600-grit, and 100-grit silicon carbide abrasive.

Effects of thermal cycling and surface roughness on the Weibull distribution of porcelain strength.

The objective of this study was to test the hypothesis that thermal cycling weakens the flexural strength of porcelain. Specimens of Deguceram Gold and Vita Omega 900 were tested in four groups of 30 specimens each: in the original glazed condition versus being ground with 1000-grit, 600-grit, and 100-grit silicon carbide abrasives. Corresponding to these four types of surface treatments, four groups of 30 specimens per group received 5,000 times of thermal cycling.

Bonding strength of autopolymerizing resin to nylon denture base polymer.

This study aimed to investigate the shear bond strength of an autopolymerizing resin to a nylon denture base polymer (Lucitone FRS: LT) subjected to different surface treatments, and the results thereof compared with a heat-polymerizing resin and a polycarbonate polymer. Specimens were divided into five groups according to the surface treatment method: polishing (#600), sandblasting, adhesive primer application (resin primer), sandblasting + adhesive primer application, and tribochemical coating (Rocatec system). Following which, specimens were subjected to a shear bond strength test and Si concentrations were measured using an electron probe microanalyzer (EPMA).

Usefulness of noninjectable anesthetic gel for intraperiodontal gingival retraction.

This study aimed to determine the efficacy of local anesthesia using Oraqix for gingival retraction in 35 healthy adult patients. The median visual analogue scale value was 20.5 +/- 24.

Influence of simplified silica coating method on the bonding strength of resin cement to dental alloy.

This study evaluated the effectiveness of a simplified silica coating method (CoJet System) on the bonding strength of resin cements to dental alloy. Bonding strength of the specimens treated with metal primer after alumina sandblasting was compared with those treated with silica coating and silane coupling agent after alumina sandblasting. Furthermore, the influence of silane coupling agent on bonding strength was compared between one-liquid and two-liquid silane coupling agents.

A study of the effects of irradiation on the polymerization of dual-cured self-etching bonding system using electron spin resonance (ESR) spectroscopy.

The purpose of this study was to investigate the effect of irradiation on the polymerization behavior of a bonding agent of a dual-cured self-etching bonding system. By means of electron spin resonance spectroscopy, it was shown that the concentration of polymer radicals in samples cured chemically without irradiation was closely similar to that in samples dual-cured under irradiation. There was no significant difference in the time required to reach the maximum spin concentration between these two sample groups, thereby showing that the radical generation rates were similar.

Photoelastic analysis of the effect of palatal support on various implant-supported overdenture designs.

Statement Of Problem: The effect of palatal support on various types of implant-supported maxillary overdenture designs has not been sufficiently assessed.

Purpose: The purpose of this study was to photoelastically evaluate the palatal support of 3 designs of maxillary implant-supported overdentures.

Material And Methods: A photoelastic model of an edentulous maxilla was fabricated with four 3.