cosmetic dentistry_ beauty & science

32 I I research _ science & practice _The human body contains over 200 different types of cells, which are organised into tissues and organs that perform all the tasks required to maintain the viability of the system, including re- production. In healthy adult tissues, the cell popu- lationsizeistheresultofafinebalancebetweencell proliferation, differentiation, and death. Following tissue injury, cell proliferation begins to repair the damage. In order to achieve this, quiescent cells (dormantcells)inthetissuebecomeproliferative,or stem cells are activated and differentiate into the appropriate cell type needed to repair the damaged tissue.Researchintostemcellsseekstounderstand tissue maintenance and repair in adulthood and thederivationofthesignificantnumberofcelltypes from human embryos. It has long been observed that tissues can dif- ferentiateintoawidevarietyofcells,andinthecase of blood, skin and the gastric lining the differenti- atedcellspossessashorthalf-lifeandareincapable of renewing themselves. This has led to the idea that some tissues may be maintained by stem cells, which are defined as cells with enormous renewal capacity (self-replication) and the ability to gen- erate daughter cells with the capacity of differen- tiation. Such cells, also known as adult stem cells, will only produce the appropriate cell lines for the tissues in which they reside (Fig. 1). cosmeticdentistry 4_2013 Fig. 1_A stem cell following either self-replication or a differentiation pathway. Fig. 2_Different tissues originated from mesenchymal stem cells. Fig. 3_The diversity of cell types present in the bone marrow. Fig. 4a_Point of needle puncture for access to the bone marrow space in the iliac bone. Fig. 4b_The needle inside the bone marrow. Fig. 5a_A bone graft being harvested from the chin (mentum). Fig. 5b_A bone graft being harvested from the angle of the mandible (ramus). Fig. 5c_A bone graft being harvested from the angle of the skull (calvaria). Fig. 5d_A bone graft being harvested from the angle of the leg (tibia or fibula). Fig. 5e_A bone graft from the pelvic bone (iliac). Fig. 6_A critical bony defect created in the skull (calvaria) of a rabbit. Fig. 7_A primary culture of adult mesenchymal stem cells from the bone marrow after 21 days of culture. Fig. 8a_A CT image of a rabbit’s skull after bone-sparing grafting without stem cells (blue arrow). Note that the bony defect remains. Fig. 8b_A CT image of a rabbit’s skull after bone-sparing grafting with stem cells. Note that the bony defect has almost been resolved. Fig. 9_A bone block from a musculoskeletal tissue bank Stem cells in implant dentistry Author_ Dr André Antonio Pelegrine, Brazil Fig. 1 Fig. 4bFig. 4a Fig. 3Fig. 2