Composite is a mixture of acrylic resin and
powdered glass-like particles that produce a 
tooth-colored flling. This type of material may be
self-hardening or may be hardened by exposure to
blue light. Composite is used for fllings, inlays and
veneers. Sometimes it is used to replace a portion 
of a broken or chipped tooth.
A DvAnTAges :
•   Color and shading can be matched to the 
existing tooth;
•   Composite is a relatively strong material,
providing good durability in small to mid sized
restorations that need to withstand moderate
chewing pressure;
•   Composite may generally be used on either 
front or back teeth;
•   Fillings are usually completed in a single 
visit (with exceptions noted below);
•   Moderately resistant to breakage;
•   Often permits preservation of as much of the 
tooth as possible;
•   Low risk of leakage if bonded only to enamel;
•   Does not corrode;
•   Generally holds up well to biting force (dependent
on the material used);
•   Moderately resistant to further decay, new 
decay is easy to fnd;
•   Frequency of repair or replacement is low to
moderate.
DI sA DvAnTAges :
•   This type of flling can break and wear out more
easily than metal fllings, especially in areas of
heavy biting force. Therefore, composite fllings
may need to be replaced more often than metal
fllings;
•   Compared to other fllings, composites are
sometimes diffcult and time-consuming to place.
They can not be used in all situations;
   Composite generally is more expensive than
amalgam;
•   May require more than one visit for inlays, 
veneers and crowns;
•   May wear faster than natural dental enamel;
•   May leak over time when bonded beneath the 
layer of enamel;
•   In rare cases, a localized, allergic reaction such 
as infammation or rash may occur.



Critical Care
 
The goals of critical care medicine are to save the lives of patients with life-threatening but reversible medical or surgical conditions and to offer the dying a peaceful and dignified death. Open discussions between physicians and patients and their family members ensure that critical care is provided in a manner that is most consistent with the patient's wishes.
Respiratory Failure
General Considerations
  • Hypercapnic respiratory failure occurs with acute carbon dioxide retention [arterial carbon dioxide tension (PaCO2) >45รข€"55 mm Hg], producing a respiratory acidosis (pH <7.35).
  • Hypoxic respiratory failure occurs when normal gas exchange is seriously impaired, resulting in hypoxemia [arterial oxygen tension (PaO2) <60 mm Hg or arterial oxygen saturation (SaO2) <90%]. Usually, this type of respiratory failure is associated with tachypnea and hypocapnia; however, its progression can lead to hypercapnia as well. Hypoxic respiratory failure can result from a variety of insults, as shown in Table 8-1.
    • The acute respiratory distress syndrome (ARDS) is a form of hypoxic respiratory failure caused by acute lung injury. The common end result is disruption of the alveolar capillary membrane, leading to increased vascular permeability and accumulation of inflammatory cells and protein-rich edema fluid within the alveolar space.
    • The American-European Consensus Conference has defined ARDS as follows: (a) acute bilateral pulmonary infiltrates, (b) ratio of PaO2 to inspired oxygen concentration (FIO2) <200, and (c) no evidence for heart failure or volume overload as the principal cause of the pulmonary infiltrates.1