1. Division of Operative Dentistry, Department of Restorative Dentistry, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78284
2. Department of Operative Dentistry, College of Dentistry, The University of Iowa, Iowa City, lowa 52242
3. Department of Orthodontics, College of Dentistry, The University of Iowa, Iowa City, lowa 52242