Melissa Rodrigues de Araujo

Resistance and Stress Finite Element Analysis of Different Types of Fixation for Mandibular Orthognathic Surgery

The aim of this study was to evaluate the stress and dislodgement resistance by finite element analysis of different types of fixation in mandibular orthognathic surgery. A 3D solid finite element model of a hemi-mandible was obtained. A bilateral sagittal split osteotomy was simulated and the distal segment was advanced 5 mm forward. After the adjustment and superimposing of segments, 9 different types of osteosynthesis with 2.0 miniplates and screws were simulated: A, one 4-hole conventional straight miniplate; B, one 4-hole locking straight miniplate; C, one 4-hole conventional miniplate and one bicortical screw; D, one 4-hole locking miniplate and 1 bicortical screws; E, one 6-hole conventional straight miniplate; F, one 6-hole locking miniplate; G, two 4-hole conventional straight miniplates; H, two 4-hole locking straight miniplates; and I, 3 bicortical screws in an inverted-L pattern. In each model, forces simulating the masticatory muscles were applied. The values of stress in the plates and screws were checked. The dislodgement resistance was checked at the proximal segment since the distal segment was stable because of the screen at the occlusal tooth. The regions with the lowest and highest displacement were measured. The offset between the osteotomized segments was verified by millimeter intervals. Inverted-L with bicortical screws was the model that had the lowest dislodgment and the model with the lowest tension was the one with two conventional plates. The results suggest that the tension was better distributed in the locking miniplates, but the locking screws presented higher concentration of tension.

Primary mandibular xanthoma: case report

Xanthoma is a very rare bone tumor, especially in the mandible, that can be associated with metabolic diseases such as hyperlipidemia. A 14-year-old girl presented with a non-corticated unilocular radiolucent lesion observed on panoramic radiography. The lesion was located between the roots of the left first and second premolar teeth, extending from the cervical to the apical region, measuring approximately 1 cm in greatest dimension. An excisional biopsy revealed foam cells and occasional nonfoamy mononuclear macrophage-like cells spread among a discrete fibrous stroma. Immunohistochemically, the xanthomatous cells were CD68 and vimentin positive, focally positive for S100, CD1a, and CD3 and negative for AE1/AE3, CD20, CD117, and HMB45. Hematologic and biochemical investigations ruled out systemic disease.

Leukocyte-platelet-rich plasma diminishes bone matrix deposition in rat calvaria treated with autograft due to simultaneous increase in immunohistochemical expression of Indian Hedgehog, transforming growth factor-β, and parathyroid-1 receptor

PURPOSE This study evaluated the immunohistochemical presence of Indian Hedgehog (IHH), transforming growth factor-β (TGF-β), and parathyroid-1 receptor (PTH1R) in calvaria bone repair, and compared these results with the histological bone matrix features in defects treated with autograft in the presence or absence of L-PRP. MATERIAL AND METHODS An artificial bone defect measuring 5 × 1 mm was produced in the calvaria of 28 Wistar rats. Randomly the defects were treated with autograft and autograft mixed with L-PRP. The animals were euthanized at 15 and 40 days post-surgery. Data were analyzed by Student-Newman-Keuls test (p ≤ .05) for immunohistochemical interpretation. RESULTS The results revealed that the histological characteristic of bone matrix deposited in the defect was different in the defects treated with L-PRP. The group that received only the autograft demonstrated larger haversian bone matrix deposited, whereas the group that received autograft mixed with L-PRP revealed trabecular bone deposition. These results coincided with significantly higher immunopositivity for IHH, TGF-β1, and PTH1R in the L-PRP group. CONCLUSION These results suggest that L-PRP altered the biological characteristic of the autograft, increasing the bone cells IHH+ but inducing a trabecular bone associated with intense quantities of TGF-β and PTH1R.

Osteocalcin Immunohistochemical Expression During Repair of Critical-Sized Bone Defects Treated with Subcutaneous Adipose Tissue in Rat and Rabbit Animal Model

The aim of this study was to evaluate the osteocalcin immunoexpression during the bone repair treated with subcutaneous adipose tissue in rats and rabbits. Fourteen rats and 14 rabbits were used in the study. A critical-sized calvarial defect was created in each animal. The animals were divided into 4 experimental groups: RC (rat control), RbC (rabbit control), RAT (rat adipose tissue), RbAT (rabbit adipose tissue). In the groups RC and RbC the defect was filled with a blood clot. In groups RAT and RbAT, the defect was filled with macerated subcutaneous adipose tissue. The euthanasia was performed at 30 days (RC and RAT) and 40 days (RbC and RbAT). Histological analysis and immunohistochemical analysis of osteocalcin protein expression were performed. Data were submitted to descriptive statistical analysis (mode). Osteocalcin immunoexpression was detected in the experimental models. Notwithstanding, RbAT showed higher positivity, especially in the adipocytes, than the group RAT group. In groups RC and RbC, the surgical wound was filled by collagen fibers. In Group RAT, the defect was composed by collagen fibers and adipocytes in the reparative sites. Similarly, in RbAT, the defect also was partially filled by collagen fibers and presence of adipocytes dispersed among the fibers. Additionally, chronic inflammatory process and areas of bone matrix deposition were observed. It may be concluded that in both animal models the adipose tissue demonstrated low osteogenic capacity. However, the rabbit animal model exhibited a more evident osteocalcin immunoexpression and a greater amount of newly formed bone matrix.

Correlation Between Radiographic Area and Immunolocation of MMP-2 and MMP-9 in Unilocular Radiographic Lesions

Unilocular bone cysts are the most common entities affecting the maxillofacial region. The mechanism of proliferation and expansion remains unclear. Metalloproteinases (MMPs) are associated to diverse pathological conditions. The aim of the present study was to correlate the radiographic aspect (area) and the presence of MMP-2 and MMP-9 in dentigerous cysts, radicular cysts and keratocystic odontogenic tumors. The radiographic area of each lesion was calculated using the mathematical formula of the ellipse area. All specimens were subjected to immunohistochemical analysis for these enzymes. The average radiographic area was 284.17 mm2, 235.81 mm2 and 381.81 mm2, respectively. Statistical analyses revealed no association between the immunoreactivity of MMPs and radiographic area of the lesions in all pathologies studied, except for MMP-2 and radicular cysts, for which smaller lesions had increased immunostaining for this enzyme. The results demonstrate that quantities of MMP-2 and MMP-9 are especially involved with dentigerous and radicular cysts in expansion, whereas these enzymes seem to be related to the biological behavior of keratocystic odontogenic tumors, indicating invasion and cell proliferation. Moreover, there is an inverse association between MMP-2 and MMP-9 in keratocystic odontogenic tumors (p=0.03; rs=-0.660), indicating activity in different regions.