Root resorption during maxillary molar intrusion with clear aligners: a randomized controlled trial.

OBJECTIVES: To compare changes in maxillary molar root resorption, intrusion amount, dentoskeletal measures, and maximum bite force (MBF) between clear aligners (CA) and fixed appliances with miniscrew (FM) during molar intrusion. MATERIALS AND METHODS: Forty adults with anterior open bite were randomized into either CA or FM groups. Lateral cephalograms, cone-beam computed tomography (CBCT), and MBF were collected at pretreatment (T0) and 6 months of treatment (T1). Maxillary molar intrusion in FM were intruded by nickel-titanium (NiTi) closed-coil spring delivered force (150 grams/side) while clear aligners combined with squeezing exercise were performed in CA. Parametric tests were used for statistical analysis. RESULTS: After 6 months of treatment, significant root resorption of 0.21-0.24 mm in CA and 0.38-0.47 mm in FM were found while maxillary molars were intruded 0.68 and 1.49 mm in CA and FM, respectively. CA showed significant less root resorption and intrusion than FM. Overbite, bite closing, and MBF increased significantly. CA showed significantly less overbite and SN-MP changes but more MBF increase than FM. MBF in CA was correlated with the amount of maxillary molar intrusion (r = 0.736, P < .05). CONCLUSIONS: Maxillary molar intrusion and root resorption in CA were half the amount in FM in 6 months. The amount of maxillary molar root resorption was one-third of the intrusion distance. CA displayed less overbite increase and bite closing but more MBF increase than FM. MBF in CA was positively correlated with the molar intrusion amount.

Characterization of Phase Evolution, Microstructure and Electrical Properties of Sol-Gel Auto-Combustion Derived BCZT Ceramics.

This work aims to study the effect of sintering temperature on properties of barium calcium zirconate titanate (BCZT) ceramics. The BCZT is a Pb-free material that shows excellent piezoelectric properties. In this study, BCZT ceramics were prepared from BCZT powders synthesized from barium nitrate, calcium nitrate, zirconium (IV) oxynitrate hydrate, titanium (IV) butoxide and citric acid precursors by the sol-gel auto-combustion method. The BCZT powder was calcined at the temperature ranging from 700 to 1000 °C. Green bodies were sintered at various temperatures (1200-1450 °C). The X-ray diffraction patterns showed only non-crystalline phase of as-burnt powder. For the calcined powders, XRD patterns showed that the amount of crystalline, perovskite phase increased with increasing calcination temperature. The crystalline particles have a spherical shape and the size in the range of 25-35 nm. For the BCZT ceramics sintered at 1200-1300 °C, the density tended to increase with increasing sintering temperature. Very high bulk densities of 5.62-5.63 g/cm3 (which were higher than those of the ceramics synthesized by the wet-chemical method) were achieved at the sintering temperature of 1400-1450 °C. Ceramics produced at these temperatures possessed fully-developed microstructures, very good dielectric properties as well as high response of polarization and strain to applied electric field.

Effects of ZnO nanoparticulate addition on the properties of PMNT ceramics.

This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics to form PMNT/xZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/xZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics.