A systematic review of methods for tissue analysis in animal studies on orthodontic mini-implants.

Anchorage devices are increasingly used in orthodontics, and their clinical performance is directly dependent on the tissue response to these devices. This study aims to identify assessment parameters for evaluating tissue reactions around orthodontically loaded implants and to propose parameters to be included in a standardized method. Several electronic databases (PubMed, ScienceDirect, the Cochrane database) were explored for papers from January 1999 to December 2009. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement was used as a guideline for the methodology of systematic reviews. Twenty-five publications were selected from 123 potentially relevant abstracts. The selected studies mainly aimed to answer a clinical question and particularly the ability of immediate loading in orthodontics. Very few studies aimed to understand the healing mechanism around the devices leading to a lack of information on this topic. The most frequent combination of assessment methods was clinical evaluation, histology/histomorphometry and intravital bone labeling. Although the dog model is mainly used, pigs represent an interesting animal model, especially when studying devices in growing bone. Despite the extensive use of miniscrews in growing individuals, only few studies have included young subjects in their protocol. Moreover, in such studies, an oral hygiene program is absolutely necessary to avoid complications. Finite element analysis could improve the knowledge of the relationship between design and bone reaction; unfortunately, this elaborated method is complex and impossible to perform routinely. For standardization, the authors recommend to include specific criteria in study protocols when assessing tissue response to orthodontically loaded devices.

In vitro orthodontic bracket bonding to porcelain.

This in vitro study investigated the influence of using different combinations of bracket, adhesive, and light-curing source on the tensile bond strength to porcelain and on failure patterns at debonding. Tensile tests were performed using: one ceramic bracket versus one metal bracket, two orthodontic composites; type bisphenol A-glycidyldimethacrylate and urethane dimethacrylate (UDMA), and four light-curing units with the same range of emission spectrum but various light intensities: three light-emitting diode (LED) units and one halogen-based unit. One hundred and sixty porcelain samples were randomly divided into 16 equal groups. The porcelain surface was conditioned with 9 per cent hydrofluoric acid before silane application. The composite was photo-polymerized for 40 seconds. After storage in water at 37°C for 24 hours, the samples were subjected to tensile force until bond failure. Bond strength and bond failure mode were recorded; results were analysed (α = 0.05) using R language; linear model with constant variance for the bond strength and multinomial distribution for the failure mode. The bond strength in all groups was sufficient to withstand orthodontic treatment (>6 MPa). There was no statistical difference between the adhesives, but comparing bracket × light interaction, it was significantly higher with the ceramic bracket. No significant differences were seen between the metal bracket groups, but for the ceramic bracket, the results were significantly higher with the LED light. No fracture was observed in porcelain with the metal bracket but it occurred in 35 per cent of the ceramic bracket samples and the risk was higher when using UDMA composite and lower with LED high intensity light.

Three-dimensional modeling system for unilateral mandibular bone distraction: a clinical case.

Facial hemiatrophies are anomalies of the first branchial arch and affect one in 4000-5000 newborns. Bone distraction is the technique of choice for the treatment of these dysmorphoses. Mandibular osteodistraction requires prior determination of the characteristics of the distraction vector whose three components will serve to activate the distractor. The patient, aged 5 years, presented with a right facial hemiatrophy, Grade IB according to the classification of Pruzansky. Tomodensitometric acquisition was obtained with a CT scanner. Software specifically designed for this application allows segmentation of the anatomical elements by a region-growing algorithm. The 3D representation of each element is added to a 3D scene, in which are placed the built-up landmarks necessary for the surgical simulation after 3D cephalometric analysis. The surgical cleavage plane is oriented according to the surgeon's requirements while preserving the predominant anatomical elements. The software allows performance of rotations and translations of the bone segments rendered independently from the cleavage plane. The distances and angles covered during the virtual movement are measured at its conclusion. The aim of moving the bone segments is to render the mandibular occlusion plane parallel to the reference occlusion plane. The vertical growth of the maxilla is realized by secondary recuperation. The distractor used was of an external multidirectional type allowing elongation of the mandibular ramus and mandibular corpus, closure of the goniac angle, and lateralization or medialization of the ramus. On the 15th day, the mandibular angle was reduced by 10 degrees, which allowed closure of the anterior gap and recentering of the incisive areas by a half-cuspid. The patient presented with a complex bone deficit in the three spatial directions, which allowed the development of software for modeling the distraction. Other clinical cases will be necessary to validate this 3D imaging-based technique.

[Three-dimensional modeling of mandibular distraction]. / Modélisation tridimensionnelle de la distraction mandibulaire.

Facial hemi-atrophy affects 1 in 4000 or 5000 children. We propose treating this deformation of the 1st branchial arch with the "bone distraction" lengthening technique first described by Ilizarov in the 1950s, which has already been employed with the mandible. We have modelled mandibular distraction in facial hemi-atrophy patients and discuss the benefits of such pre-surgical planning encompassing the assistance of pre- and post-operative as well as surgically coordinated orthodontic therapy. Using X scanner views of a 5 year-old girl patient, we have developed a distraction-simulation software, which makes the pathological side harmonious with the healthy side along the medial sagittal plane. In order to obtain facial symmetry, put bones in balance, and orient the occlusal plane horizontally, essential requisites of occlusal stability, it is necessary: to employ a 2 or 3-dimensional distractor, to pre-plan the distraction and screw positioning, to set up a fixed orthodontic treatment plan prior to beginning distraction therapy.