(Vancouver, WA)  --  The Washington State Department of Health says it will soon decide whether to launch an investigation into the death of a four-year-old boy at a Vancouver dentist's office.  The mother of Mykel Peterson says her son died last Friday during a routine procedure at Must Love Kids Pediatric Dentistry in Vancouver.  A health department spokesman says the agency will make a decision on whether to investigate.  The Clark County Medical Examiner says it will likely be weeks before the cause of the boy's death is confirmed.