Root resorption associated with orthodontic force in inbred mice: genetic contributions

Abstract

Root resorption (RR) is an unwanted sequela of orthodontic treatment. Despite rigorous investigation, no single factor or group of factors that directly causes RR has been identified. The purpose of this study was to examine the effect of the genotype on susceptibility or resistance to develop RR secondary to orthodontic force. Nine-week-old male mice from eight inbred strains were used and randomly distributed into control (C) or treatment (T) groups as follows: A/J (C = 9,T = 9), C57BL/6J (C = 7,T = 8), C3H/HeJ (C = 8,T = 6), BALB/cJ (C = 8,T = 6), 129P3/J (C = 6,T = 8), DBA/2J (C = 8,T = 9), SJL/J (C = 8,T = 10), and AKR/J (C = 9,T = 8). Each of the treated mice received an orthodontic appliance to tip the maxillary left first molar mesially for 9 days. Histological sections of the tooth were used to determine RR and tartrate resistant acid phosphatase (TRAP) activity. The Wilcoxon ranked-sum non-parametric test was used to evaluate differences between the groups. The results showed that the DBA/2J, BALB/cJ, and 129P3/J inbred mouse strains are highly susceptible to RR, whereas A/J, C57BL/6J and SJL/J mice are much more resistant. The variation in the severity of RR associated with orthodontic force among different inbred strains of mice when age, gender, food, housing, and orthodontic force magnitude/duration are controlled support the hypothesis that susceptibility or resistance to RR associated with orthodontic force is a genetically influenced trait.

Orthodontic mechanotransduction and the role of the P2X7 receptor

“…Measuring by counting cavities per area in histological sections, for instance, is a common approach Al-Qawasmi et al, 2006). In contrast to volumetric measurements, this method does not necessarily give a result of net root resorption, because it could also reflect a change in the turnover of cementum on the surface of the root.…”

“…Although numerous investigators have suggested associations between genetic factors and root resorption Al-Qawasmi et al, 2003a;AlQawasmi et al, 2003b;Al-Qawasmi et al, 2006;Harris et al, 1997;Ngan et al, 2004) the mechanical environment was an inadequately controlled variable. The current study is the first to appropriately control the mechanical environment and select histological sectioning planes with FEM.…”

“…Inbred strains of mice (Thyagarajan et al, 2003), where individual variability is practically eliminated, have recently been explored in orthodontic studies Al-Qawasmi et al, 2006;Ignelzi et al, 1995;Oshiro et al, 2002). With the development of genetic engineering, it has become possible to analyze the effects of a single biological variable (encoded by a gene) in orthodontic responses.…”

Risk variables of external apical root resorption during orthodontic treatment

“…Although several studies have investigated this topic, no single or associated factor has been identified as responsible for EARR due to orthodontic treatment. 3 Previous studies focused on the magnitude of the force applied, 1,25 duration, 15,21 and the type of orthodontic treatment 1,6,7 have not established a causal relation between these factors and EARR.…”

“…3 The etiology of EARR associated with orthodontic treatment is multifactorial and involves environmental and host factors. Several variables have been described in the literature as possible risk factors for EARR: Tooth anomalies and the shape of root and alveolar bone crest, 13,14,20,27 type and severity of malocclusion, 5 2,3,14 This study investigated the association of age, gender, orthodontic extractions and Angle classification with external apical root resorptions resulting from orthodontic treatment.…”