Thermal and volumetric assessment of endodontic filling techniques using infrared thermography and micro-CT.

PURPOSE: To assess root temperature during filling techniques and quantify the volume of endodontic filling materials using infrared thermography (IT) and micro-computed tomography (micro-CT). METHODS: Ninety premolars were divided into three groups: lateral condensation (LC), single cone (SC) and thermomechanical compaction (TMC). For thermal analysis, 45 teeth were assessed using a FLIR T650sc IT camera during filling techniques and 45 teeth were scanned using a Nikon micro-CT to assess gutta-percha, cement, and void volumes. Descriptive and inferential statistical analyses were performed (non-parametric Mann-Whitney test, Kruskal-Wallis test, and Friedman test with Tukey's bidirectional analysis of variance). RESULTS: TMC showed the highest temperature increase at 15 s after the procedure and a significant temperature decrease at 45 s after its completion. TMC showed the largest volume of gutta-percha and LC the highest void volume. CONCLUSION: The temperature increase generated by gutta-percha endodontic filling techniques is within acceptable limits. A greater volume of endodontic cement was observed for the SL and LC filling techniques.

Nitrogen-mediated effects of elevated CO2 on intra-aggregate soil pore structure.

Soil pore structure has a strong influence on water retention, and is itself influenced by plant and microbial dynamics such as root proliferation and microbial exudation. Although increased nitrogen (N) availability and elevated atmospheric CO2 concentrations (eCO2 ) often have interacting effects on root and microbial dynamics, it is unclear whether these biotic effects can translate into altered soil pore structure and water retention. This study was based on a long-term experiment (7 yr at the time of sampling) in which a C4 pasture grass (Paspalum notatum) was grown on a sandy loam soil while provided factorial additions of N and CO2 . Through an analysis of soil aggregate fractal properties supported by 3D microtomographic imagery, we found that N fertilization induced an increase in intra-aggregate porosity and a simultaneous shift toward greater accumulation of pore space in larger aggregates. These effects were enhanced by eCO2 and yielded an increase in water retention at pressure potentials near the wilting point of plants. However, eCO2 alone induced changes in the opposite direction, with larger aggregates containing less pore space than under control conditions, and water retention decreasing accordingly. Results on biotic factors further suggested that organic matter gains or losses induced the observed structural changes. Based on our results, we postulate that the pore structure of many mineral soils could undergo N-dependent changes as atmospheric CO2 concentrations rise, having global-scale implications for water balance, carbon storage, and related rhizosphere functions.