External invasive resorption: Case report of a rapidly progressive process in an impacted maxillary canine during orthodontic treatment.

External invasive resorption (EIR) is a type of external resorption that can involve the coronal, middle and apical parts of the root in its advanced stages and results in progressive loss of tooth structure. Common potential predisposing factors for EIR are orthodontic treatment and trauma. The EIR progression rate has not been described previously. This case report describes rapidly progressive EIR in an impacted maxillary canine after surgical exposure and application of directional orthodontic traction over 8 months. The article discusses the etiologies of EIR, the possible reasons for EIR and its rapid progression in the presented case and proposes a new theory of the connection between EIR and tooth impaction.

Effect of orthodontic treatment and comorbidity risk factors on interdental alveolar crest level: A radiographic evaluation.

INTRODUCTION: Alveolar bone loss is regarded as a potential adverse event during orthodontic treatment, especially in adults. The purposes of this study were to evaluate the prevalence and severity of interdental alveolar crest height loss in adult orthodontic patients compared with an untreated control group and to identify comorbidity risk factors for such bone loss (high BMI score, high blood pressure, high cholesterol levels, and smoking). METHODS: Standardized bitewing radiographs of patients' buccal segments were taken before and after treatment of 34 consecutive adults treated in an orthodontic clinic. The control group included 29 patients from the operative dental clinic matched according to age and sex. Mean ages of the participants before treatment were 35.7 ± 6.7 and 35.6 ± 7.3 years for the control and treatment groups, respectively. Before orthodontic treatment, the patients were evaluated, treated as needed, and approved by a periodontist. They were periodontically healthy before treatment. Interdental alveolar crest height loss was calculated by subtracting the distance on a bitewing x-ray from the cementoenamel junction to the interdental alveolar crest at each interproximal tooth surface from the mesial aspect of the first premolar to the distal aspect of the second molar (8 sites per quadrant). Changes in interdental alveolar crest height were calculated by subtracting the cementoenamel junction-interdental alveolar crest distance before treatment from the corresponding distance after treatment. RESULTS: The mean individual bone losses of all interproximal surfaces were 0.130 ± 0.192 and 0.072 ± 0.280 mm in the treatment and control groups, respectively. These differences did not reach statistical significance (P = 0.353). Twenty-two patients (65%) from the treatment group and 10 patients (34%) from the control group had an increase in the cementoenamel junction-interdental alveolar crest distance of more than 1 mm in at least 1 site, with borderline significance between the groups (P = 0.079). Notably, no association was observed between bone loss with any comorbidity factor. CONCLUSIONS: The results of this study correspond to the conventional understanding in the orthodontic and periodontal literature that orthodontic tooth movement per se does not cause attachment loss. However, orthodontists should always be aware of the possibility of periodontal deterioration during orthodontic treatment. Therefore, comprehensive periodontal examination is necessary during orthodontic treatment, especially in adults.