Studies consistently report that pitch volume is still a major risk factor for shoulder and elbow injuries. Some things have changed in the last few decades that might help you prevent such injuries.
For example, overuse of the throwing arm is accomplished by keeping a log of number of pitches thrown for each practice, game, season, and year. There are recommended guidelines and standards for maximum number of pitches allowed.
Video and computer analysis of pitching mechanics have also contributed helpful information about the effect of different types of pitches. For example, a recent study comparing curve balls with fastballs and change-up pitches showed that curve balls aren't more dangerous than fastballs for youth pitchers.
Just as you recall from your previous coaching experience, it's the overuse of the throwing arm that's the problem. Other risk factors include physical condition of the athlete and pitching mechanics. Differences in stride length and forearm and wrist action can affect ball release. It's wise to pay attention to all of these factors during practice and preparation of the athlete.