Thermoluminescence in GdAl3(BO3)4 phosphors: Unusual heating rate dependencies, dose responses and kinetic parameters.

The current study focuses on the production of GdAl3(BO3)4 (GAB) phosphors using gel combustion. X-ray diffraction (XRD) and thermoluminescent (TL) methods were used to investigate the structural and thermoluminescence (TL) features of the samples. XRD results revealed that GAB phosphors were crystallized in a rhombohedral crystal system. TL experimental data exhibited an unusual heating rate behaviour, which was explained by the semi-localized transition model, and this provides valuable insight into the properties of the GAB sample. Beta-irradiated GAB hosts exhibit two primary peaks at 106 °C and 277 °C on their TL glow curves. We have employed a variety of heating rates (VHRs), TM-Tstop method, and computerized glow curve deconvolution (CGCD) techniques. By using a combination of these techniques, we can identify the kinetic parameters of the GAB samples more accurately, including peak numbers, activation energy, and frequency factors. Both Tm-Tstop and CGCD techniques produce similar results in terms of trap numbers and trap depths. In the trap centers, electrons were trapped at 1.05 eV, 0.84 eV, 1.12 eV, 1.20 eV, 1.42 eV, 1.63 eV and 1.42 eV. There was a linear behaviour of GAB samples over a dose range of 0.1 Gy-10 Gy. GAB phosphors did not show any significant changes in TL response with repeated irradiation cycles, suggesting that it is a reliable radiation dosimeter. GAB is therefore a potential candidate for radiotherapy dose measurement based on these findings.

Three-dimensional presentation of cell migration in the periodontal ligament of the rat incisor.

The progenitor compartments and cell migration were examined in the tooth-related periodontal ligament (t-PDL) of rat incisors. A pulse injection of 3H-Tdr was administered to 15 rats (200 gm each) and the animals were killed in groups of five, at 1 hr and at 1 and 2 weeks after injection. Three-dimensional analysis of cell counts and labeling index demonstrated the existence of two progenitor compartments (PC). The apical PC (responsible for 70% of synthesizing cells) was concentrated in the apical 5 mm of the t-PDL. The paracemental PC (30% of synthesizing cells) was located along and around the cementum, occupying 24 micron of the t-PDL. The cells from the apical PC migrated incisally at a rate of 6 mm/week, which is a rate similar to that of tooth eruption. The cells from the paracemental PC moved in a transverse direction toward either bone or cementum at the much slower rate of 16 micron/week.

The effect of load duration on long-term recovery of the eruptive function in the rat incisor.

The purpose of this study was to determine the long-term recovery of the normal rate of eruption of the rat incisor following application of loads of similar magnitude but of varying duration. The daily rate of eruption of the continuously growing tooth served as indicator of the functional recovery of its periodontium. The left mandibular incisor was shortened out of occlusion in 34 experimental and 16 control rats. The experimental animals were divided into groups A, B, and C, and continuous loads (19.47 g +/- 0.42 g) were applied to the shortened incisors by means of closed-coil springs for 5, 14, and 28 days, respectively. Following removal of the springs, the daily rate of eruption was measured and calculated in all 50 animals for a period of 10 weeks. The extended impairment of eruption in the experimental animals was directly proportional to the duration of loading: at 10 weeks postloading, it was present in 18%, 67%, and 100% of the rats in groups A, B, and C, respectively. The intragroup variations in the rate of eruption of individual teeth were more pronounced following short-term loading than after prolonged load application. Short-term loading proved to be least harmful regarding recovery of eruptive function.

Three-dimensional presentation of the fibroblast progenitor compartment in the periodontal ligament of the rat incisor.

The purpose of this study was to determine the shape, size, and spatial configuration of the fibroblast progenitor compartment (PC) of the tooth-related periodontal ligament (PDL). Five albino rats (weight 200 gm) were killed 1 hr following intraperitoneal injection of 3H-thymidine. The incisors were decalcified, embedded in glycol-methacrylate, and sectioned serially, perpendicularly to the long axis of the tooth. Ten 2-microns-thick sections along each tooth were selected, processed autoradiographically, and the distance from the apex measured. Labeled and unlabeled fibroblasts were counted in 8 x 80-microns consecutive layers. Cell density (CD) and labeling index (LI) were plotted on a three-dimensional system of coordinates depicting the directions: apex to incisal edge, cementum to bone, and cemento-enamel junction (CEJ) to lingual tooth surface. The CD along the tooth was constant, except at 2-6 mm distant from the apex, where it was significantly higher. The highest concentration of cells around the tooth was in the 20-microns region adjacent to the cementum. The PC on the mesial and lateral tooth sides extended 1-4 mm from the apex, with the LI peak (6.5%) occurring at 2 mm. The PC on the lingual tooth side was located at 2-6 mm from apex, peaking (14%) at 4 mm. On the cementum-bone coordinate, the PC extended to about 50 microns from the cementum on all sides, the LI peak appearing at a distance of 20-40 microns from the tooth. The LI was consistently higher on the lingual side than on the mesial and lateral aspects.