Growth in root length of the mandibular canine and premolars in a mixed-longitudinal orthodontic sample


  • Shelley L. Smith,

    Corresponding author
    1. Department of Sociology and Anthropology, University of Texas at Arlington, Arlington, Texas 76019
    • Department of Sociology and Anthropology, Box 19599, University of Texas at Arlington, Arlington, TX 76019, USA
    Search for more papers by this author
  • Peter H. Buschang

    1. Department of Orthodontics, Baylor College of Dentistry, Texas A&M University System Health Science Center, Dallas, Texas 75246
    Search for more papers by this author

  • This article was presented at the 2008 AAPA meetings in a symposium in honor of A. Roberto Frisancho, upon the occasion of his retirement from the Department of Anthropology of the University of Michigan.


Numerous studies of dental development focusing on eruption (clinical emergence) exist in the literature, but fewer studies examine dental development as a process extending across years or decades, and root development is commonly assessed using fractional root lengths. Here, we examine the growth of mandibular canine and premolar roots in a mixed-longitudinal sample of orthodontic patients (77 females and 74 males) from north central Texas. Multilevel models are generated for root lengths as a percentage of total tooth lengths (within films) as well as for absolute root lengths (across films). As a percentage of tooth length, roots grow with decreasing velocity through time between 7 and 14 years of age. More complex patterns appear for absolute growth in root length, with girls showing an earlier maximum growth rate for the canine than for the premolars. Substitution of dental age for chronological age reduces between-subject variation (assessed at age 11), especially for boys. A better understanding of dental maturation, including root length growth, should allow improved prediction models. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc.