Cystic Fibrosis  The  genetically altered protein affects exocrine gland function. The defective exocrine gland function leads to microobstruction of the pancreas, which results in cystic degeneration of the pancreas and, ultimately, a digestive enzyme deficiency producing malabsorption of nutrients.The defective gene products cause abnormal water and electrolyte transport across epithelial cells, which results in a chronic disease of the respiratory and gastrointestinal system, elevated levels of electrolytes in sweat, and impaired reproductive function.In the lungs, retention of mucus occurs. Children with cystic fibrosis have a high incidence of tooth discoloration when systemic tetracyclines are taken during tooth formation. With the advent of alternative antibiotics, the incidence of tooth discoloration is decreasing. The incidence of dental caries in children with cystic fibrosis is low secondary to long-term antibiotic therapy, buffering capacity of excess calcium in the saliva, and pancreatic enzyme replacement therapy. There is a high incidence of mouth  breathing  and  open-bite  malocclusion  associated with  chronic  nasal  and  sinus  obstruction. Patients  with cystic fibrosis may prefer to be treated in a more upright position to allow them to clear secretions more easily. The use of sedative agents that interfere with pulmonary function should be avoided, and the patient’s physician should be contacted before nitrous oxide–oxygen sedation is used in a patient exhibiting evidence of severe emphysema.