Alveolar bone reconstruction

Inicialmente a Reconstrução Alveolar Proteticamente Guiada (RAPG)  foi aplicada para reconstrução óssea de alvéolos na maxila. Com a previsibilidade dos resultados, a técnica passou a ser usada também na mandíbula. Este trabalho mostra um caso clínico executado na mandíbula.
Figura 1-Corte transaxial inicial do elemento 46, com extensa perda óssea associada à fr atura radicular. Altura óssea = 16,62 mm; espessura óssea = 2,32 mm. Figura 2-Aspecto clínico inicial mostra ausência de acentuada retração gengival, que é indispensável para a técnica da RAPG. Figura 3-Visão panorâmica da área mostrando outro pré-requisito da técnica da RAPG, a presença das cristas ósseas proximais de altura normal. Figura 4-Modelo para ser preparado para a técnica da RAPG. A restauração do elemento 47 foi removida para ser incluída na prótese.

Context: Alveolar bone remodeling is important to achieve an optimal Orthodontic Tooth Movement (OTM). Runt-related transcription factor 2 (RUNX2) and Osterix (OSX) expression are important for bone remodeling. Green tea (Camelia sinensis) can enhancing bone remodeling. Aims: To investigate the effect of a methanolic extract of green tea (MEGT) on the OSX and RUNX2 expression during OTM in Wistar rats. Methods: The experiment with post-test only and simple random sampling was conducted. The samples consisted of twenty-eight Wistar rats, which were then divided into 4 groups (n=7), negative control (CN) group, positive control (CP) group with OTM but without MEGT administration, group with OTM for 14 days and MEGT administration from day 7 to day 14 (T1), group with OTM with MEGT administration for 14 days (T2). Nickle-titanium coil spring with 10 g/mm 2 force was placed between the incisors and the maxillary molars. MEGT was collected from East Java and identified its principal metabolite by HPLC analysis. RUNX2 and OSX expression were analyzed by utilizing Immunohistochemical analysis. Analysis of Variance (ANOVA) was performed and then continued with least significant difference (p<0.05). Results: The highest RUNX2 and OSX expression were found in the tension side of group T2 with significant difference between groups (p<0.05). The principal metabolite of the extract was identified as epigallocatechin-3-gallate (EGCG). Conclusions: Post administration of a MEGT could increase RUNX2 and OSX expression in alveolar bone of OTM Wistar rats. Part of this action could be attributed to the presence of EGCG in the extract.

Alveolar bone provides structural supports to teeth. The outer and inner compact bone are formed by osteons, the basic structure of cortical bone, with a central vertical Haversian canal and rings forming a lamellar bone (bundle or alveolar bone). The central cancellous bone is the spongiosa (spongy bone). Bundles of collagen fibers (Sharpey’s fibers) provide attachment of the root to bone. Perforating Volkmann’s canals, limiting the inner bone are forming “the cribliform plate”. Oriented horizontally, the plate contains blood vessels and nerves issued from the periosteum. Alveolar bone associates intramembranous and endochondral bones. Mesenchymal stem cells (osteoprogenitor cells) initiate bone mineralization including a differentiation cascade. Alveolar bone includes pre-osteoblasts, osteoblasts, osteocytes, and bone lining cells, all these cells being derived from hematopoietic stem cells. The alveolar bone extracellular matrix (ECM) includes collagens, elastins, glycosaminoglycans and proteoglycans, small leucine-rich proteoglycans, small integrin-binding ligand N-linked glycoprotein (phosphorylated SIBLINGs) (DSPP [fragmented after cleavage into dentin sialoprotein, dentin glycoprotein, and dentin phosphoprotein], phosphorylated proteins such as bone sialoprotein, matrix extracellular phosphorylated protein (MEPE), and osteopontin], non-collagenous non-phosphorylated proteins (osteonectin), serum derived proteins (α2-HS-glycoprotein, and albumin), specific and non-specific alkaline phosphatase, metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs -1 to -4) and enzymes that regulate components of the alveolar bone. Osteoclasts are stimulating osteoclastogenesis, and consequently bone remodeling. ECM molecules are involved in bone mineralization or acting as mineralization inhibitors. The major functions of the alveolar bone are the following

Providing structural support to teeth (Sharpey’s fibers)
Act as mechanosensor
Supply vascular nutrition and innervation, releasing neuromediators to the periodontal ligament
Communicate with cells on the bone surface and with marrow cells
Regulate blood-calcium and phosphate metabolism. Interactions between integrins-dependent extracellular molecules and bone cells are essential for bone formation and resorption. Studies have addressed the importance of the lacunocanalicular system and the pericellular fluid for the adaptation of bone to mechanical forces.