[Radiation Protection in Orthodontics: relevant data]. / La radioprotection en orthodontie : données utiles.

For the past 30 years X-Ray images have effected a veritable revolution in medical practice. Using them practitioners cannot only make reliable and precise diagnoses when they begin a course of treatment but also accurately follow the progress of therapy. Orthodontics is one of the specialties that has benefited from the innovations in medical radiography. At the same time we have learned more about the risks that the use of ionizing radiation entails and are, accordingly, basing our radiological practice on the ALARA principle ("As Low As Reasonably Achievable"). Even though this concept is embodied in much national and European legislation, practitioners will enhance their daily use of radiology by acquiring an understanding of the scientific basis for ALARA.

[Useful radiological techniques in orthodontics]. / Techniques radiographiques utiles en orthodontie.

Specialists in dento-facial orthopedics have a large range of dental radiological techniques at their disposal to help them in their diagnostic and therapeutic procedures. Peri-apical, occlusal, panoramic, and cephalometric X-Rays are two-dimensional techniques that orthodontists can complement, if necessary, with Multi slices CT scan or Cone Beam Computed Tomography. Orthodontists must apply and respect quality criteria for each type of film in order to derive the best information from every image and to avoid producing artifacts or false images that will reduce their diagnostic value and, accordingly, the service that they render to patients. Practitioners must be willing to spend the few moments it takes to position patients correctly in the radiological apparatus instead of taking multiple views to compensate for failing to scrupulously follow protocols of radiology.

[Measurement errors in 2D cephalometrics]. / Les erreurs de mesure en céphalométrie 2D.

The objective of this study is to analyze the influence that two parameters, the source-subject distance and the type of receptor, have on the precision of localization of the 19 most frequently employed cephalometric landmark points and then to analyze the repercussions of localization errors on cephalometric measurements. The correct use of profile cephalograms (norma lateralis) for clinical purposes depends essentially on the precision of the identification and localization of the different landmark points that are required for the elaboration of the various cephalometric analyses. For this study we asked 53 orthodontists, selected at random, to identify 19 cephalometric points on standard profile or digitized films taken at distances of 1 m 50 or of 4 m. The results we obtained show no statistically significant differences in relation to the source-subject distance or to the type of receptor. Each cephalometric landmark presented a characteristic dispersion cloud; the most reliable points were primarily located on the median sagittal plane. The cephalometric measurements that demonstrated the greatest variability were associated with positions of the incisor apices, which makes their value doubtful in the establishment of treatment plans and in ongoing evaluations of treatment progress. For similar reasons, the worth of the Frankfort plane can be questioned when it is compared to other, much more reliable cranial reference planes especially S-Na.

[Indications for radiography in orthodontics and dentofacial orthopedics]. / Indications des examens radiologiques en orthopédie dento-faciale.

The risks associated with the use of ionizing radiation are a constant concern not only for practitioners but also for legislators who have included this ethical rule in the Code of public safety. It proposes reduction of risks by insisting that all X-Rays be taken only when they accord with one of the fundamental principles of X-Ray protection: they must be justified by clear diagnostic need. In direct application of this principle the French government in 2006 published a guide for the management of radiological and dental and stomatological examinations. However, this document dealt only slightly with orthodontics, a field in which the flourishing and burgeoning of radiological techniques made it urgent that regulations for use of X-Rays in orthodontics be brought up to date on an ongoing and permanent basis. The objective of this article is, accordingly, after presentation of a systematic and critical analysis of the lit erature, to propose up-to-date recommendations for proper taking of orthodontic X-Ray films.

[Imaging of temporo-mandibular disorders]. / Imagerie des désordres temporo-mandibulaires.

Dominated for years by standard films (tomographic mouth open and mouth closed X-rays, MRI) radiographs of the TMJ have progressively lost their usefulness to diagnosticians who have progressively increased their reliance on well codified clinical examinations, which suffice in a great majority of cases.The indications for and diagnostic worth of radiological studies and the impact they have on the management of TMJ disorders are today quite low especially when the high cost of procedures like MRI, computerized tomography, and CBCT is taken into account. In this article we discuss the various maladies that dentists might encounter and the situations in which radiological examinations are still indicated.

Experimental evaluation of bone quality measuring speed of sound in cadaver mandibles.

OBJECTIVES: To demonstrate in vitro the feasibility of speed of sound (SOS) measurements through the mandible and to investigate the relationships between mandibular SOS, local bone mineral density (BMD), and the ratio between trabecular and cortical thicknesses (Tb.Th/Cort.Th). The long-term goal is to find a safe, simple test for bone quality in sites for dental implant placement. METHODS: Excised human mandibles (N = 23) were used for the measurement of sound transmission with two 1.6 MHz transducers. Three regions of interest (ROIs) were selected in each of the specimens, namely incisor, premolar, and molar regions. To determine short-term precision, 10 measurements (with repositioning between measures) were performed for each ROI. Local BMD and mandibular cross-sectional morphological characteristics were determined by dual x-ray absorptiometry (DXA) and computed tomography (CT). RESULTS: The coefficient of variation for SOS was found to be 1%. SOS measurements at different sites were significantly different. A significant linear relationship was found between SOS and BMD (r2 = 0.62; P < .0001), whereas a nonlinear relationship was found between SOS and Tb.Th/Cort.Th (r2 = 0.53; P < .0001). CONCLUSION: This in vitro study demonstrated the feasibility of SOS measurement through the mandible. Mandibular SOS reflects local BMD and Tb.Th/Cort.Th. In vivo studies are now required to confirm the predictive power of SOS measurement for bone quality assessment and its potential usefulness as a clinical diagnostic technique.