Effect of repeated orthodontic treatment on the dental and periodontal tissues of the rat incisor

Invasive cervical resorption of central incisor during orthodontic treatment

Introduction:

Invasive cervical resorption (ICR) is a relatively rare type of ERR (External Root Resorption), in which a localized resorption begins in the cervical area of the tooth, below the epithelial junction and above the ridge crest.

Objective:

Describe the clinical case of an 11-year-old boy with no dental trauma history, presenting moderate crowding and ectopic eruption of the maxillary right central incisor. He had been undergoing orthodontic treatment elsewhere, and his family was dissatisfied with the results.

Description:

A new treatment was indicated, which included rapid maxillary expansion followed by extraction of four premolars. During routine panoramic evaluation, a radiolucid image was detected and a periapical radiograph was requested. At this point, an ICR of the maxillary right central incisor was found. The treatment was cautiously finalized and despite the use of light forces, central incisor was severally compromised by ICR and was therefore extracted.

Conclusion:

This clinical example discusses the importance of routine radiographs for the early diagnoses of ICR.

Association of orthodontic force system and root resorption: A systematic review

INTRODUCTION

In this systematic review, we assessed the literature to determine which evidence level supports the association of orthodontic force system and root resorption.

METHODS

PubMed, Cochrane, and Embase databases were searched with no restrictions on year, publication status, or language. Selection criteria included human studies conducted with fixed orthodontic appliances or aligners, with at least 10 patients and the force system well described.

RESULTS

A total of 259 articles were retrieved in the initial search. After the review process, 21 full-text articles met the inclusion criteria. Sample sizes ranged from 10 to 73 patients. Most articles were classified as having high evidence levels and low risks of bias.

CONCLUSIONS

Although a meta-analysis was not performed, from the available literature, it seems that positive correlations exist between increased force levels and increased root resorption, as well as between increased treatment time and increased root resorption. Moreover, a pause in tooth movement seems to be beneficial in reducing root resorption because it allows the resorbed cementum to heal. The absence of a control group, selection criteria of patients, and adequate examinations before and after treatment are the most common methodology flaws.

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

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.