GENETIC FACTORS IN EXTERNAL APICAL ROOT RESORPTION AND ORTHODONTIC TREATMENT

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GENETIC FACTORS IN EXTERNAL APICAL ROOT RESORPTION AND ORTHODONTIC TREATMENT
2004
J.K. Hartsfield, Jr.1,2,*
E.T. Everett1,2
R.A. Al-Qawasmi1
Critical Reviews in Oral Biology & Medicine

© 2004 International and American Associations for Dental Research

1 Department of Oral Facial Development, Indiana University School of Dentistry, 1121 West Michigan Street, Indianapolis, IN 46202-5186, USA; and 2 Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA;

* corresponding author, jhartsfi@iupui.edu

Abstract

External apical root resorption (EARR) is a common sequela of orthodontic treatment, although it may also occur in the absence of orthodontic treatment. The degree and severity of EARR associated with orthodontic treatment are multifactorial, involving host and environmental factors. Genetic factors account for at least 50% of the variation in EARR. Variation in the Interleukin 1 beta gene in orthodontically treated individuals accounts for 15% of the variation in EARR. Historical and contemporary evidence implicates injury to the periodontal ligament and supporting structures at the site of root compression following the application of orthodontic force as the earliest event leading to EARR. Decreased IL-1? production in the case of IL-1B (+3953) allele 1 may result in relatively less catabolic bone modeling (resorption) at the cortical bone interface with the PDL, which may result in prolonged stress concentrated in the root of the tooth, triggering a cascade of fatigue-related events leading to root resorption. One mechanism of action for EARR may be mediated through impairment of alveolar resorption, resulting in prolonged stress and strain of the adjacent tooth root due to dynamic functional loads. Future estimation of susceptibility to EARR will likely require the analysis of a suite of genes, root morphology, skeleto-dental values, and the treatment method to be usedÛor essentially the amount of tooth movement planned for treatment.

Key words. Root resorption, EARR, orthodontics, genetics, heritability

(I) Introduction

Basic descriptors of root resorption are based on the anatomical region of occurrenceÛi.e., internal root resorption and external root resorption (cervical root resorption and external apical root resorption). Additional classification may involve two types of internal resorption: root canal (internal) replacement resorption and internal inflammatory resorption. External resorption can be classified into four categories according to its clinical and histologic manifestations: external surface resorption, external inflammatory root resorption, replacement resorption, and ankylosis. External inflammatory root resorption has been further categorized into cervical resorption with or without a vital pulp (invasive cervical root resorption) and external apical root resorption (EARR) (Ne et al., 1999).

This paper reviews EARR and its association with orthodontic treatment, and examines a new paradigm for its multifactorial etiology. EARR is a frequent iatrogenic outcome associated with orthodontic treatment, especially in the maxillary incisors, and may also occur in the absence of orthodontic treatment (Harris and Butler, 1992; Harris et al., 1993). Depending on the methodology, the incidence of EARR without orthodontic treatment has been reported to range from zero to 90.5% (Brezniak and Wasserstein, 1993). From 7% to 13% of individuals who have not had orthodontic treatment show some EARR on radiographs (Rudolph, 1936; Harris et al., 1993), presumably as a function of occlusal forces. There is an association of EARR in those who have not received orthodontic treatment with missing teeth, increased periodontal probing depths, and reduced crestal bone heights (Harris et al., 1993). Individuals with bruxism, chronic nail biting, and anterior open bites with concomitant tongue thrust may also show an increased extent of EARR before orthodontic treatment (Harris and Butler, 1992). Dental trauma, especially with re-implantation of an avulsed tooth, is also associated with increased EARR (Donaldson and Kinirons, 2001). For the most part, EARR is asymptomatic unless substantial tooth structure is affected, so early detection is unlikely unless radiographs are used (Brezniak and Wasserstein, 1993, 2002b).

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