2nd prelims

• The important decisions concerning a surgical procedure should be made well before the administration of anesthesia commences.

  Developing a Surgical Diagnosis
• Basic Necessities for Surgery

  The two principal requirements: 

  1. adequate visibility : (1) adequate access, (2) adequate light, and (3) a surgical field free of excess blood and other fluids and debris.
  2. assistance
• Aseptic technique is used to minimize wound contamination by pathogenic microbes.
• Principles of Incisions:

  1. Sharp blade of the proper size and shape should be used.
  2. Firm, continuous stroke should be used when incising.
  3. Surgeon should carefully avoid accidentally cutting important structures when incising. Each patient’s microanatomy is unique.
  4. Incisions through epithelial surfaces that the surgeon plans to reapproximate should be made with the blade held perpendicular to the epithelial surface.
  5. Incisions in the oral cavity should be properly placed.
• Surgical flaps are made to gain surgical access to an area or to move tissue from one place to another. Several basic principles of flap design must be followed to prevent the primary complications of flap surgery: necrosis, dehiscence, and tearing.
• Flap Design


  Flap necrosis can be prevented if the surgeon attends to four basic

  flap design principles:The height of a flap should never be

  greater than the base, unless a major artery is present in the base.
• Flap necrosis can be prevented if the surgeon attends to four basic

  flap design principles:

  1. The height of a flap should never be greater than the base, unless a major artery is present in the base.
  2. Height of a flap should be no more than twice the width of the base.
  3. When possible, an axial blood supply should be included in the base of the flap.
  4. The base of flaps should not be excessively twisted, stretched, or grasped with anything that might damage vessels
• Flap margin dehiscence (separation leading to opening of a sutured

  incision) is prevented by approximating the edges of the flap over healthy bone, by gently handling the edges of the flap, and by not placing the edges of the flap under tension.
• Prevention of Flap Tearing

  • referable to create a flap at the onset of surgery that is large enough for the surgeon to avoid tearing it or interrupting surgery to lengthen.
  • Envelope flaps are those created by incisions that produce a one-sided flap.
  • However, if an envelope flap does not provide sufficient access, it should be lengthened or another (a releasing) incision should be made to prevent it from tearing . Vertical (oblique) releasing incisions should generally be placed one full tooth anterior to the area of any anticipated bone removal.
• Hemostasis: Prevention of excessive blood loss during surgery is important for

  preserving a patient’s oxygen-carrying capacity.

  Another problem bleeding causes is the formation of hematomas (collections of blood under soft tissue).
• Wound hemostasis can be obtained in four ways

  1. Assisting natural hemostatic mechanisms. This is usually accomplished by using a gauze sponge to place pressure on bleeding vessels or placing a hemostat on a vessel.
  2. Use of heat to cause the ends of cut vessels to fuse (thermal coagulation).
  3. Providing surgical hemostasis is by suture ligation.
  4. Placing vasoconstrictive substances such as epinephrine in the wound or by applying procoagulants such as commercial thrombin or collagen on the wound.
• Dead space in a wound is any area that remains devoid of tissue after closure of the wound. Dead space can be eliminated in four ways:

  1. Suturing tissue planes together to minimize the postoperative void.
  2. Place a pressure dressing over the sutured wound.
  3. Place packing into the void until bleeding has stopped and then to remove the packing.
  4. Use of drains, by themselves or in addition to pressure dressings. S
• Decontamination and Debridement

  Wound debridement is the careful removal of necrotic and severely ischemic tissue and foreign material from injured tissue that would impede wound healing.
• Inflammation Control

  Edema is an accumulation of fluid in the interstitial space because of fluid

  transudation from damaged vessels and lymphatic obstruction by fibrin.
• Traumatic injuries can be caused by physical or chemical insults.


  Physical: incision, crushing, extremes of temperature or irradiation

  
  

  Chemical: cause injury include those with unphysiologic pH or tonicity, those that disrupt protein integrity, and those that cause ischemia by producing vascular constriction or thrombosis.
• contact inhibition: genetically programmed regenerative ability that allows it to reestablish its integrity through proliferation, migration, and a process
• wound healing: stereotypical process is initiated and, if able to proceed unimpeded, works to restore tissue integrity. 


  These three basic stages are (1) inflammatory, (2) fibroplastic, and (3) remodeling.
• Inflammatory stage:  sometimes referred to as the lag phase

  Has two phases: (1) vascular and (2) cellular .
• Vascular phase: vasoconstriction slows blood flow into the area of injury, promoting blood coagulation. Within minutes, histamine and prostaglandins E1 and E2, elaborated by white blood cells, cause vasodilation and open small spaces between endothelial cells, which allows plasma to leak and leukocytes to migrate into interstitial tissues. Fibrin from the transudated plasma causes lymphatic obstruction, and the transudated plasma— aided by obstructed lymphatic vessels—accumulates in the area of injury, functioning to dilute contaminants. This fluid collection is called edema. 
• The cardinal signs of inflammation:

  1. Redness (rubor)
  2. Swelling (tumor)
  3. Loss of function (functio laesa)

  Vasodilation = warmth and erythema

  Transudation of fluid =swelling

  Histamine/kinins/prostaglandins released by leukocytes: loss of function
• Cellular phase: triggered by the activation of serum complement by tissue trauma. Complement-split products, particularly C3a and C5a, act as chemotactic factors and cause polymorphonuclear leukocytes (neutrophils) to stick to the side of blood vessels (margination) and then migrate through the vessel walls (diapedesis).
• Remodeling Stage ( wound maturation)

  Many of the previous randomly laid collagen fibers are removed as they are replaced by new collagen fibers, which are oriented to better resist tensile forces on the wound. In addition, wound strength increases slowly but not with the same magnitude of increase seen during the fibroplastic stage. Wound strength never reaches more than 80% to 85% of the strength of uninjured tissue. 
• A final process, which begins near the end of fibroplasia and continues during the early portion of remodeling, is wound contraction.
• • Factors That Impair Wound Healing

  (1) foreign material, (2) necrotic tissue, (3)ischemia, and (4) wound tension.
• Healing by Primary, Secondary, and Tertiary Intention

  primary intention: edges of a wound in which there is no tissue loss are placed and stabilized in essentially the same anatomic position they held before injury and are allowed to heal.

  secondary intention: healing occurs more rapidly, with a lower risk of infection, and with less scar formation than in wounds allowed to heal

  tertiary intention: refer to the healing of wounds through the use of tissue grafts to cover large wounds and bridge the gap between wound edges.
• Healing of Extraction Sockets

  • During the first week of healing: White blood cells enter the socket to remove contaminating bacteria from the area and begin to break down any debris such as bone fragments that are left in the socket.
  • Finally, during the first week of healing, osteoclasts accumulate along the crestal bone. The second week is marked by the large amount of granulation tissue that fills the socket.
  • The processes begun during the second week continue during the third and fourth weeks of healing, with epithelialization of most sockets complete at this time.
• Bone healing:

  • Osteogenic cells (osteoblasts) important to bone healing are derived from the following three sources: (1) periosteum, (2) endosteum, and (3) circulating pluripotential mesenchymal cells. 


  • Osteoclasts, derived from monocyte precursor cells, function to resorb necrotic bone and bone that needs to be remodeled. Osteoblasts then lay down osteoid, which, if immobile during healing, usually goes on to calcify.
• Implant Osseointegration

  Wound healing around dental implants involves the two basic factors: (1) healing of bone to the implant and (2) healing of alveolar soft tissue to the implant.

  Maximizing the likelihood of bone winning this race with soft tissue to cover the implant requires the following four factors: (1) a short distance between bone and the implant, (2) viable bone at or near the surface of bone along the implant, (3) no movement of the implant while bone is attaching to its surface, and (4) an implant surface reasonably free of contamination by organic or inorganic materials.
• Nerve Healing has two phases: (1) degeneration and (2) regeneration. 2 types of degeneration:

  1. segmental demyelination:which the myelin sheath is dissolved in isolated segments. causes a slowing of conduction velocity and may prevent the transmission of some nerve impulses. 


  Symptoms include paresthesia= patient does not find painful, dysesthesia = patient finds uncomfortable, hyperesthesia= excessive sensitivity of a nerve to stimulation, and hypoesthesia=decreased sensitivity of a nerve to stimulation.
• Nerve Healing has two phases: (1) degeneration and (2) regeneration. 2 types of degeneration:

  2. Wallerian degeneration: (away from the central nervous system [CNS]) undergo disintegration in their entirety.

  Wallerian degeneration stops all nerve conduction distal to the proximal axonal stump. This type of degeneration follows nerve transsection and other destructive processes that affect peripheral nerves and is likely to undergo spontaneous regeneration.
• The three types of nerve injuries are (1) neurapraxia, (2) axonotmesis, and (3) neurotmesis

  Neurapraxia: the least severe form of peripheral nerve injury, is a contusion of a nerve in which continuity of the epineural sheath and the axons is maintained.

  Axonotmesis: has occurred when the continuity of the axons, but not the epineural sheath, is disrupted.

  Neurotmesis: the most severe type of nerve injury, involves a complete loss of nerve continuity.
• • Nerve Repair

  When there is a lack of spontaneous neurosensory regeneration due to neuroma formation, microneurosurgery may be required to achieve functional sensory recovery
• Communicable Pathogenic Organisms: Bacteria of Upper Respiratory Tract Flora

  1. Oral cavity: Aerobic, gram-positive organisms, primarily Streptocci, Actinomyces, Anaerobic bacteria, Candida spp.
  2. Nasal cavity: Aerobic gram-positive organisms, primarily Streptococcus spp. Children: Haemophilus influenzae. Adults: Staphylococcus aureus
  3. Facial skin: S. epidermidis, occasionally, Corynebacterium diphtheriae, Propionibacterium acnes in pores and hair follicles.
  4. Nonmaxillofacial Flora: aerobic gram-negative and anaerobic enteric organisms
• Viral Organisms

  The viral organisms that cause the most difficulty are the hepatitis

  B and C viruses and human immunodeficiency virus (HIV).