ODONTOBLAST DIFFERENTIATION - A RESPONSE TO ENVIRONMENTAL CALCIUM

The response of the dental pulp to calcium hydroxide has been well des cribed but the process of pulpal repair leading to dentinal bridge for mation appears complex and the mechanisms remain incompletely understo od. Through the precise regulation of the free calcium ion in the cyto sol, cells have been able to utilize anions such as phosphates for a w ide range of activities such as energy production (oxidative phosphory lation). As anions are abundant in the cytosol, intracellular levels o f calcium ions are kept low, several orders of magnitude less than tha t of the surrounding extracellular matrix. Consequently, cells are abl e to use calcium ions for the regulation of many cellular events. The binding of extracellular molecules such as cytokines, hormones or anti bodies, with receptors on the plasma membrane may result in short- or long-term modifications to cellular metabolism, including the mechanis ms of intracellular calcium homeostasis. Cell survival depends upon th e ability to adapt to changes in the cell's micro-environment. Adaptat ion in turn results in altered cellular activity that may be interpret ed as showing that the cell has become more or less specialised. In so me instances this may include the resumption of mitotic activity. If t he rate or magnitude of change exceeds a cell's adaptive capacity, the cell dies. Responses of cells to alterations in their environment are reviewed as they may provide an explanation for the success of calciu m hydroxide in facilitating pulpal repair and the differentiation of o dontoblasts.