BackgroundRapid maxillary expansion (RME), indicated in the treatment of maxillary deficiency directs high forces to maxillary basal bone and to other adjacent skeletal bones. The aim of this study is to (i) evaluate stress distribution along craniofacial sutures and (ii) study the displacement of various craniofacial structures with rapid maxillary expansion therapy by using a Finite Element model.MethodsAn analytical model was developed from a dried human skull of a 12 year old male. CT scan images of the skull were taken in axial direction parallel to the F-H plane at 1 mm interval, processed using Mimics software, required portion of the skull was exported into stereo-lithography model. ANSYS software was used to solve the mathematical equation. Contour plots of the displacement and stresses were obtained from the results of the analysis performed.ResultsAt Node 47005, maximum X-displacement was 5.073 mm corresponding to the incisal edge of the upper central incisor. At Node 3971, maximum negative Y-displacement was -0.86 mm which corresponds to the anterior zygomatic arch, indicating posterior movement of craniofacial complex. At Node 32324, maximum negative Z-displacement was -0.92 mm representing the anterior and deepest convex portion of the nasal septum; indicating downward displacement of structures medial to the area of force application.ConclusionsPyramidal displacement of maxilla was evident. Apex of pyramid faced the nasal bone and base was located on the oral side. Posterosuperior part of nasal cavity moved minimally in lateral direction and width of nasal cavity at the floor of the nose increased, there was downward and forward movement of maxilla with a tendency toward posterior rotation. Maximum von Mises stresses were found along midpalatal, pterygomaxillary, nasomaxillary and frontomaxillary sutures.
During 2016-2017, carrots (Daucus carota) with severe soft rot symptoms on the tap root, associated with a foul odour, wilting and collapse of foliage ( Fig. 1), were collected from the rural districts of Kolar, Chikkaballapura and Bengaluru of Karnataka state, India. Disease incidence was 20-30% in affected fields. Samples of two or three roots were collected from each of ten different fields. Isolation was done using green pepper fruits as enrichment hosts (Fig. 2), followed by streaking on nutrient agar as described by Akbar et al. (2015). The resulting bacterial colonies were whitish to dull white, mucoid, raised and slimy on nutrient agar (Fig. 3). Ten isolates, one from each sample were identified as Gram-negative and anaerobic. In biochemical tests performed according to Brenner et al. (2004), all isolates were positive for catalase and nitrate reductase, and used citrate, glucose, lactose, maltose, malonate and celloboise, but were negative for oxidase, indole and acetoin tests. They produced mucoid growth on Luria Bertani medium, grew at 37°C and on 5% NaCl.To confirm pathogenicity, bacterial suspensions (100 µl, approx. 10 8 CFU/ml) were injected into whole roots and pipetted onto 5 mm thick carrot slices (Michalik et al., 1992) and incubated at 30°C and 90% relative humidity in a growth chamber. Sterile distilled water was used as a negative control. Water-soaked lesions developed on whole roots after three days, leading to soft rotting with a foul odour after four days (Fig. 4). Brown lesions were observed on carrot slices after three days and the degree of rotting varied between different isolates. Bacteria with identical colony characteristics were re-isolated from all inoculated rotted tissues.
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