Effects of orthodontic appliances on the diagnostic quality of magnetic resonance images of the head.

INTRODUCTION: The influence of 4 commonly used fixed orthodontic appliances on artifact formation and diagnostic quality of magnetic resonance (MR) images of the head produced by a 3-T MR scanner was studied. METHODS: Stainless steel brackets, ceramic brackets, combination of ceramic brackets and steel molar tubes, and multistranded steel mandibular lingual retainers were embedded into custom-made trays for each of 10 adult subjects. Head MR scans of 9 regions were acquired for each subject wearing these trays. Sagittal T1-weighted, axial T2-weighted, axial gradient-recalled, axial diffusion-weighted, noncontrast axial MR angiography, and axial fluid-attenuated inversion recovery MR sequences were included. Two neuroradiologists evaluated image distortions and diagnostic qualities of the 1314 acquired images (13860 image slices). RESULTS: The images were affected by appliance, head region, and MR sequence. Stainless steel brackets and molar tubes affected the images the most, and ceramic brackets caused minimal image distortion. CONCLUSIONS: Head MR images are differentially affected by orthodontic appliances. The appliance, region imaged, and MR sequence should be considered before imaging patients wearing fixed orthodontic appliances.

Mandibular incisor extraction: a systematic review of an uncommon extraction choice in orthodontic treatment.

OBJECTIVES: To review the published literature in order to address clinical questions regarding the indications, effects and outcomes of mandibular incisor extraction in orthodontics. DATA SOURCES: Three electronic databases were searched: PubMed (1950-January 2011), Ovid Embase+Ovid Embase Classic (1947-January 2011) and Cochrane library (6 Cochrane databases, 1996-January 2011). The following journals were additionally searched: American Journal of Orthodontics and Dentofacial Orthopedics (1960-January 2011), Angle Orthodontist (1960-January 2011), European Journal of Orthodontics (1970-January 2011) and Journal of Orthodontics (1974-January 2011). Grey literature was searched using Google Scholar and System for Information on Grey Literature in Europe. Secondary search of the references cited in the relevant articles was also conducted. DATA SELECTION: Articles in vivo, in Humans, in English, concerning treatment of malocclusion with mandibular incisor extractions or missing mandibular incisors. Fifty-four publications met these inclusion criteria and were reviewed. DATA EXTRACTION: Data were extracted independently by two reviewers with regard to: (1) indications; (2) contraindications; (3) effects; (4) outcomes; and (5) factors associated with successful outcomes. DATA SYNTHESIS: Considering the descriptive nature of the studies found, a narrative synthesis was undertaken. CONCLUSIONS: The descriptive nature of published articles precludes making strong evidence-based recommendations regarding this extraction choice, but it is clear that mandibular incisor extraction can be effectively used in the resolution of crowding, as well as intermaxillary malocclusion in carefully selected cases. Several factors that could lead to good outcomes of orthodontic treatment following mandibular incisor extraction were identified. Mild-to-moderate class III malocclusion, an edge-to-edge anterior occlusion or anterior crossbite, with mild anterior mandibular tooth size excess, and minimal open bite tendencies were the clinical situations most frequently treated with this unique extraction choice. On the other hand, clinicians should be careful to avoid poor outcomes such as gingival recession, open interproximal gingival embrasures, increased overjet and overbite.