Cone-beam computed tomography classification of the mandibular second molar root morphology and its relationship to panoramic radiographic appearance.

OBJECTIVES: This study aimed to clarify the relationship between the panoramic radiographic appearance and the longitudinal cone-beam computed tomography (CBCT) classification of root configurations of the mandibular second molar. METHODS: Panoramic radiographs of 1058 mandibular second molars were classified into five types according to the number and configuration of the roots. These molars were also examined with CBCT at four levels between the pulp chamber and the root apex, and axial images perpendicular to the root axis were categorized into three patterns: single (fused root with small grooves on both buccal and lingual sides or a round root with one canal); double (two separate roots with a trabecular appearance between them); and C-shaped (root with a deep groove opening only on the lingual or buccal side relative to the opposite side). Based on these patterns and their scan levels, the CBCT root morphology appearance in each tooth unit was classified into seven groups. Relationships were investigated between these seven CBCT groups and the five panoramic root types. RESULTS: In panoramic types 1 and 2 (with separate roots), 85% had roots with a double pattern (groups II and III) on the CBCT images. In panoramic types 3 and 4 (with fused roots), 85% had C-shaped CBCT patterns at the lower scan levels. CONCLUSIONS: When panoramic images show fused root types, CBCT examinations should be planned to clarify the root canal configuration.

Non-invasive imaging of radiocesium dynamics in a living animal using a positron-emitting 127Cs tracer.

Visualizing the dynamics of cesium (Cs) is desirable to understand the impact of radiocesium when accidentally ingested or inhaled by humans. However, visualization of radiocesium in vivo is currently limited to plants. Herein, we describe a method for the production and purification of 127Cs and its use in visualizing Cs dynamics in a living animal. The positron-emitting nuclide 127Cs was produced using the 127I (α, 4n) 127Cs reaction, which was induced by irradiation of sodium iodide with a 4He2+ beam from a cyclotron. We excluded sodium ions by using a material that specifically adsorbs Cs as a purification column and successfully eluted 127Cs by flowing a solution of ammonium sulfate into the column. We injected the purified 127Cs tracer solution into living rats and the dynamics of Cs were visualized using positron emission tomography; the distributional images showed the same tendency as the results of previous studies using disruptive methods. Thus, this method is useful for the non-invasive investigation of radiocesium in a living animal.

Stereogradient polymers by ruthenium-catalyzed stereospecific living radical copolymerization of two monomers with different stereospecificities and reactivities.

Stereogradient polymers, a fundamentally new type of polymers, were prepared by the stereospecific living radical copolymerization of two monomers that have different stereospecificities and reactivities. The ruthenium-catalyzed living radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) and the silyl-capped HEMA [(tert-butyldimethylsilyl)-HEMA] (SiHEMA) in (CF3)2C(Ph)OH afforded stereogradient poly(HEMA), in which the rr content gradually increased from 62 to 77% at 0 degrees C, due to the lower reactivity and the higher syndiospecificity of SiHEMA.