After injuries and irritation (e.g.. restorative procedures or progressing rapidly caries), the main odontoblasts can die. Because these cells postmitotic cells, they are not capable of regeneration through cell division. New dentin however, could be formed. Such dentinal repair appears through the activities of the so-called repair odontoblasts or secondary odontoblasts. The predecessor of these cells is thought that the population of postnatal stem cells, which are present in the pulp and paper tissue is correct (22). After their recruitment and regulation, mineralizing matrix lay down on the dentinal wall. Repair of the secondary odontoblasts may also against the corresponding wound-healing agent used for the treatment of direct impact of the pulp (see Chapter 4). Consequently, the new generation odontoblast-like cells, capable of making new dentin locally, may develop in the flesh after injury.
Secondary odontoblasts produce dentin at a rate that depends on the degree and duration of the injury.
The development of this hard tissues leads to the increase of dentine thickness (Fig. 2.6 and 2.7).
It should be noted that dentin, educated middle odontoblasts more abrupt and amorphous and contains less dentinal tubules than primary dentin (11). These tubes will not necessarily be in direct line with the tubules of the primary dentin (Fig. 2.8). Therefore, complex of primary and reparative dentin becomes less permeable to external derivative of the matter. It also follows that such dentin is less sensitive to heat, and osmotic evaporative stimuli. The quality of the new solid tissues is not always as good as primary dentin. When it is formed quickly, for example. after ischemic damage to dental trauma, it can become extremely porous and contain fields, filled with a soft cloth.
Although the pulp of the tooth space in x-rays may appear to give scope for bacterial growth and multiplication in the case of subsequent exposure to infectious (Fig. 2.9). Similarly, hard tissue repair of tooth pulp scars can sometimes show gross defects, which makes it easily permeable for bacteria and bacterial elements. Thus, hard tissue deposition in the flesh, although adding to the defense potential of the tissues in certain cases, should be considered as scar tissue.