Seguridad industrial

Vivek Shetty, DDS, Dr.Med.Dent.

Charles N. Bertolami, DDS, D.Med.Sc.

The healing wound is an overt expression of an intricate and tightly choreographed sequence of cellular and biochemical responses directed toward restoring tissue integrity and functional capacity following injury. Although healing culminates uneventfully in most instances, a variety ofintrinsic and extrinsic factors canimpede or facilitate the process. Understanding wound healing at multiple levels—bio- chemical, physiologic, cellular, and molecular—provides the surgeon with a frame- work for basing clinical decisions aimed at optimizing the healing response. Equally important it allows the surgeon to critical- ly appraise and selectively use the growing array of biologic approaches that seek to assist healingby favorably modulating the wound microenvironment.

The Healing Process The restoration of tissue integrity, whether initiated by trauma or surgery, is a phylo- genetically primitive but essential defense response. Injured organisms survive only if they can repair themselves quickly and effectively. The healing response depends primarily on the type of tissue involved and the nature of thetissue disruption. When restitution occurs by means of tis-sue that is structurally and functionally indistinguishable from native tissue, regeneration has taken place. However, if tissue integrity is reestablished primarily through the formation of fibrotic scar tissue, then repair has occurred. Repair by scarring is the body’s version of a spot weld and the replacement tissue is coarse and has alower cellular content tan native tissue. With the exception of bone and liver, tissue disruption invariably results in repair rather than regeneration. At the cellular level the rate and quali- ty of tissue healing depends on whether the constitutive cells are labile, stable, or permanent. Labile cells, including the keratinocytes of the epidermis and epitelial cells of the oral mucosa, dividethroughout their life span. Stable cells such as fibroblasts exhibit a low rate of duplication but can undergo rapid proliferation in response to injury. For example, bone injury causes pluripotential mesenchymal cells to speedily differentiate into osteoblasts and osteoclasts. On the other hand permanent cells such as specialized nerve and cardiac muscle cells do not divide in postnatal life. Thesurgeon’s expectation of “normal healing” should be correspondingly realistic and based on the inherent capabilities of the injured tissue. Whereas a fibrous scar is normal for skin wounds, it is suboptimal in the context of bone healing.

At a more macro level the quality of the healing response is influenced by the nature of the tissue disruption and the circumstances surrounding wound closure.Healing by first intention occurs when a clean laceration or surgical incision is closed primarily with sutures or other means and healing proceeds rapidly with no dehiscence and minimal scar formation. If conditions are less favorable, wound healing is more complicated and occurs through a protracted filling of the tissue defect with granulation and connec- tive tissue. This process is calledhealing by second intention and is commonly associated with avulsive injury, local infection, or inadequate closure of the wound. For more complex wounds, the surgeon may attempt healing by third intention through a staged procedure that combines secondary healing with delayed primary closure. The avulsive or contaminated wound is débrided and allowed to granulate and heal by second intention for 5to 7 days. Once adequate granulation tissue has formed and the risk of infection appears minimal, the wound is sutured close to heal by first intention. Wound Healing Response Injury of any kind sets into motion a complex series of closely orchestrated and temporally overlapping processes directed toward restoring the integrity of the involved tissue. The reparative processes are most commonly...