Bone stress and strain after use of a miniplate for molar protraction and uprighting: a 3-dimensional finite element analysis

The aim of this study was to use the finite element method to evaluate the distribution of stresses and strains on the local bone tissue adjacent to the miniplate used for anchorage of orthodontic forces. Methods: A 3-dimensional model composed of a hemimandible and teeth was constructed using dental computed tomographic images, in which we assembled a miniplate with fixation screws. The uprighting and mesial movements of the mandibular second molar that was anchored with the miniplate were simulated. The miniplate was loaded with horizontal forces of 2, 5, and 15 N. A moment of 11.77 N.mm was also applied. The stress and strain distributions were analyzed, and their correlations with the bone remodeling criteria and miniplate stability were assessed. Results: When orthodontic loads were applied, peak bone strain remained within the range of bone homeostasis (100-1500 mu m strain) with a balance between bone formation and resorption. The maximum deformation was found to be 1035 mu m strain with a force of 5 N. At a force of 15 N, bone resorption was observed in the region of the screws. Conclusions: We observed more stress concentration around the screws than in the cancellous bone. The levels of stress and strain increased when the force was increased but remained within physiologic levels. The anchorage system of miniplate and screws could withstand the orthodontic forces, which did not affect the stability of the miniplate.

The performance of conventional and fluorescence-based methods for occlusal caries detection: an in vivo study with histological validation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Effect of post-polymerization heat treatment on a denture base acrylic resin: histopathological analysis in rats

This work examined the histological effects, on the rat palatal mucosa, of a denture base acrylic resin, submitted or not to a post-polymerization heat-treatment. Methods: Fifteen adult female Wistar rats, with sixty days old, weighting 150 g – 250 g were divided in G1: animals being maintained under the same conditions as the experimental groups following described, but without the use acrylic palatal plates (control group); G2: use of heat-polymerized acrylic resin palatal plates made of Lucitone 550; G3: use of palatal plates identical to G2, but subjected to a post-polymerization treatment in a water bath at 55°C for 60 min. The plates covered all the palate and were fixed in the molar region with light-cured resin, thus being kept there for 14 days. After the sacrifice, the palate was removed, fixed in formaldehyde 10% and decalcified with EDTA. Sections were stained using haematoxylin and eosin. Images in duplicate were made from the central region of the cuts, to measure the thickness (μm) of the keratin layers (TKC), epithelium total (TET) and connective tissue (TCC). Statistical analyses were carried out by one-way ANOVA and Tukey post-tests (α=0.05). Results: According to the results there was significant difference in the thickness of keratin between G2 and G3, with G1 having the intermediate value and similar to the other groups. There was a significant difference in the connective tissue with G3

Classification of histological images based on the stationary wavelet transform

Non-Hodgkin lymphomas are of many distinct types, and different classification systems make it difficult to diagnose them correctly. Many of these systems classify lymphomas only based on what they look like under a microscope. In 2008 the World Health Organisation (WHO) introduced the most recent system, which also considers the chromosome features of the lymphoma cells and the presence of certain proteins on their surface. The WHO system is the one that we apply in this work. Herewith we present an automatic method to classify histological images of three types of non-Hodgkin lymphoma. Our method is based on the Stationary Wavelet Transform (SWT), and it consists of three steps: 1) extracting sub-bands from the histological image through SWT, 2) applying Analysis of Variance (ANOVA) to clean noise and select the most relevant information, 3) classifying it by the Support Vector Machine (SVM) algorithm. The kernel types Linear, RBF and Polynomial were evaluated with our method applied to 210 images of lymphoma from the National Institute on Aging. We concluded that the following combination led to the most relevant results: detail sub-band, ANOVA and SVM with Linear and RBF kernels.

The Fresh Frozen Bone Allograft (FFBA) to reconstruc the atrophic maxilla: evaluation of the clinical and histological viability at six and nine months in the maxillary sinus

This work aimed to analyze clinically and histologically the allogen bone graft behavior at 6 and 9 months. A leukoderm, female, 55 years old patient sought dental care for oral rehabilitation with dental implants and implant supported fixed prosthesis in the maxilla. Bilateral sinus lifting procedure were performed in a same patient, the analysis were made after 6 and 9 months, respectively. At 6 months, there was lack of a better bone remodeling in the region, associated to the presence of fibrous connective tissue within the collected tissue, showing us that this is not the best stage of tissue maturation to place dental implants. The 9 months period showed an improvement, with a more organized bone tissue surrounding particles of homogenous bone, what possibly had increased implant stability at the time of surgery. There is no doubt about the increase of clinical applications of FFBA, but there are no studies available regarding the standardization of time to load implants inserted in allografts. So papers with long-term monitoring are necessary to eliminate questions that still remain to be answered.

Immunohistochemical, tomographic, and histological study on onlay bone graft remodeling. Part III: allografts

Objective In the last decades aroused the interest for bone tissue bank as an alternative to autogenous grafting, avoiding donor sites morbidity, surgical time, and costs reduction. The purpose of the study was to compare allografts (ALg) with autografts (AUg) using histology, immunochemistry, and tomographic analysis. Material and methods Fifty-six New Zealand White rabbits were submitted to surgical procedures. Twenty animals were donors and 36 were actually submitted to onlay grafting with ALg (experimental group) and AUg (control group) randomly placed bilaterally in the mandible. Six animals of each group were sacrificed at 3, 5, 7, 10, 20, and 60 postoperative days. Immunolabeling was accomplished with osteoprotegerin (OPG); receptor activator of nuclear factor-k ligand (RANKL); alkaline phosphatase (ALP); osteopontin (OPN); vascular endothelial growth factor (VEGF); tartrate-resistant acid phosphatase (TRAP); collagen type I (COL I); and osteocalcin (OC). Density and volume of the grafts was evaluated on tomography obtained at the surgery and sacrifice. Results The ALg and AUg exhibited similar patterns of density and volume throughout the experiments. The intra-group data showed statistical differences at days 7 and 60 in comparison with other time points (P = 0.001), in both groups. A slight graft expansion from fixation until day 20 (P = 0.532) was observed in the AUg group and then resorbed significantly at the day 60 (P = 0.015). ALg volume remained stable until day 7 and decreased at day 10 (P = 0.045). The light microscopy analysis showed more efficient incorporation of AUg onto the recipient bed if compared with the ALg group. The immunohistochemical labeling picked: at days 10 and 20 with OPG in the AUg group and at day 7 with TRAP in the ALg group (P = 0.001 and P = 0.002, respectively). Conclusions ALg and AUg were not differing in patterns of volume and density during entire experiment. Histological data exhibit more efficient AUg incorporation into recipient bed compared with the ALg group. Immunohistochemistry outcomes demonstrated similar pattern for both ALg and AUg groups, except for an increasing resorption activity in the ALg group mediated by TRAP and in the AUg group by higher OPG labeling. However, this latter observation does not seem to influence clinical outcomes.