The waits to see Boston dermatologists, obstetrician-gynecologists, and orthopedic surgeons for routine care have grown longer—to as much as a year for the busiest doctors. A study of five specialties shows that the wait for a nonurgent appointment in the Boston area has increased in the past five years, and now averages 50 days. Patients in Boston and other areas of Massachusetts for years have faced notoriously long delays, according to earlier surveys of physicians' offices. A number of factors contribute, doctors said, but the 2006 health insurance law which has required hundreds of thousands of state residents to obtain coverage probably has worsened the waits.