Simulated superficial and deep tissue doses using niobium filtration for cephalometric radiography

The effect of added niobum filtration 30 μm and 50μm on constant potential and conventional full-wave rectified cephalometric units was explored in terms of radiation dose. Water was used to simulate soft tissues to attenuate the X-ray beam. The addition of niobium 30μm and 50μm for each unit caused a reduction in the surface dose, but resulted in an increase in the dose deep to 8 cm of water. The more heavily filtered beam reduced the surface dose most for each operating potential, while, providing the highest deep dose through 8cm of water in each case. There was a comparatively strong linear association between half-value layer (HVL) and relative dose at both the zero and the 8cm thicknesses of water. The coefficients of determination (r²) and the significant probabilities of correlation coefficient (p) were 0.82 (p<0.0001) at the surface and 0.89 (p<0.0001) with 8cm of water.     

An investigation of the composite resin/porcelain interface.

Failures at composite resin/porcelain interfaces under shear-like loading were examined. Porcelain surfaces were treated with hydrofluoric acid and/or one of two silane coupling agents, using two different composite resin cements. The results showed that after seven days storage, bond strengths of specimens which had undergone porcelain surface treatment were greater than the cohesive strength of the porcelain itself, resulting in brittle fracture of the porcelain. The diluted restorative composite resin performed as well as the commercial composite resin cement. Silane pretreatment of porcelain was important as the bond strength of etched/silane primed specimens was significantly higher than the etched only specimens. However, one primer appeared to be more efficient than the other in bond promotion. Some explanations for the differences in bond strengths are offered.     

A laboratory study to investigate the differentiation of pulp vitality in human teeth by temperature measurement

Under laboratory conditions it was found that in human teeth, pulpal circulation was more efficient than supporting tissue circulation in maintaining the temperature of the crown with respect to its local atmosphere. The findings present a scientific basis for the clinical diagnosis of tooth vitality by the temperature-measurement method.     

Acute necrotizing ulcerative gingivitis in a case of systemic lupus erythematosus

Presented is an unusually severe case of acute necrotizing ulcerative gingivitis (ANUG) in association with systemic lupus erythematosus (SLE), in which the patient was observed to slough a considerable amount of attached gingival tissues and eventually to lose a number of teeth and supporting bone. The usual limited and treatable nature of ANUG is reviewed, and attention is directed to the mechanisms by which SLE and therapeutic amounts of steroids can contribute to the increased severity of the oral disease.     

Augmentation of rat mandibular ridge with demineralized bone implants

Demineralized bone implants were placed as onlays in submucosal pockets on the edentulous segment of the rat mandible, between the incisor and posterior teeth. These implants, predictably, induced osteogenesis. The mass of induced bone and implant was united to the ridge by two weeks, and there was little or no resorption over a six-month follow-up period. This study suggests that demineralized bone implants may be useful for mandibular ridge augmentation.     

Removal of overhanging amalgam: A comparative study of three instruments

This study compared the effects on tooth surface of three power-driven instruments commonly used to remove overhanging amalgam. Comparisons of methods of instrumentation were made on enamel, cementum, and amalgam. Cavitron, Roto Pro, and EVA system instruments were used. Findings showed significantly more abrasion on all surfaces in EVA groups compared with other groups. All surfaces in Roto Pro groups appeared to be smoother than in other groups. There appeared to be little difference between treated surfaces and control surfaces in the Cavitron group.