Adult teeth become crooked for a number of reasons, there can be the following: 1, jawbone atrophy: jawbone atrophy caused by the amount of bone is less than the amount of teeth, teeth alignment, angle changes, visible teeth crooked; 2, teeth wear: with age, the teeth between the gradual wear, the emergence of a gap, the teeth can be skewed; 3, missing teeth: with the age of the gradual growth of the teeth, the teeth in the tooth row in the presence of missing teeth. If the teeth are not set in time after the teeth are missing, the surrounding teeth can be tilted to the gap.