[Application of surgical locating guides on impacted supernumerary teeth extraction].

OBJECTIVE: To study the application of surgical locating guides based on cone beam computed tomography (CBCT) and computer-aided design/computer-aided manufacturing (CAD/CAM) technique on extraction of impacted supernumerary teeth. METHODS: This study included 15 patients with impacted supernumerary teeth in anterior maxillary. Surgical approach was determined by CBCT. Surgical locating guides of labial approach or palatal approach were designed and fabricated by CAD/CAM technique. Impacted supernumerary teeth were extracted under the location of surgical locating guides. RESULTS: Surgical locating guides were well attached in the operation. The impacted supernumerary teeth were located and exposed rapidly, and the adjacent important anatomical structures were avoided. CONCLUSIONS: Surgical locating guides benefit the accurate detection and reduction of trauma in extraction of impacted supernumerary teeth.

[Emissions of greenhouse gas and ammonia from the full process of sewage sludge composting and land application of compost].

There is a great uncertainty of greenhouse gas (GHG) reduction and nitrogen conservation from the full process of sludge composting and land application of compost in China due to the lack of emission data of GHG such as N2O and CH4 and ammonia (NH3). The purpose of this study is to get emission characteristics of GHGs and NH3 from the full process with on-site observation. Results showed that the total GHG emission factor from full process of the turning windrow (TW) system (eCO2/dry sludge, 196.21 kg x t(-1)) was 1.61 times higher of that from the ATP system. Among the full process, N2O was mostly from the land application of compost, whereas CH4 mainly resulted from the sludge composting. In the sludge composting of ATP, the GHG emission equivalence of the ATP (eCO2/dry sludge, 12.47 kg x t(-1) was much lower than that of the TW (eCO2/dry sludge, 86.84 kg x t(-1)). The total NH3 emission factor of the TW (NH3/dry sludge, 6.86 kg x t(-1)) was slightly higher than that of the ATP (NH3/dry sludge, 6.63 kg x t(-1)). NH3 was the major contributor of nitrogen loss in the full process. During the composting, the nitrogen loss as NH3 from both TW and ATP was nearly the same as 30% of TN loss from raw materials, and the N and C loss caused by N2O and CH4 were negligible. These results clearly showed that the ATP was a kind of environmentally friendly composting technology.