SALISBURY, Md. — Two hours before sunrise, Dee Matello joined the line outside the Wicomico Civic Center, where hundreds of people in hoodies, heavy coats and wool blankets braced against a bitter wind.Inside, reclining dental chairs were arrayed in neat rows across the arena’s vast floor. Days later, the venue would host Disney on Ice. On this Friday morning, dentists arriving from five states were getting ready to fix the teeth of the first 1,000 people in line.