A 7-year-old still sucks their thumb and has an anterior open bite. What is the cause-effect lesson? Prolonged thumb sucking (beyond age 4–5) mechanically blocks front-teeth eruption and pushes upper incisors forward — the habit's duration, frequency and intensity determine the open bite's severity. Teaching: stop the habit early and the developing bite often self-corrects; persistent habits need habit-breaker appliances. Students learn habits as modifiable etiology — unlike genetics, they can be changed.