Evaluation of the Biomechanical Properties of Austenitic Stainless Steel Fixed Retainers

The insertion of the fixed retention is an important stage of the orthodontic treatment after fixed appliances. The fixed retainers used in orthodontic treatments must be passive towards teeth, without developing any stress. This characteristic is challenging to achieve due to the mechanical properties (bending properties, stiffness) of the materials the retainers are manufactured from. Residual stress might be generated because of their flexibility and because the chemical composition of the stainless steel wires.This study aims to determine the mechanical properties of different austenitic stainlees steel wires used in retention. Also, we have compared the mechanical properties of wires with different sizes, as well as wires with the same size, new and intra-orally used. The results confirm that the mechanical parameters of the two types of wires used in fixed retention (3 braided round wires and 6 braided Flat wires) present statistically insignificant differences. The study also reflects that the mechanical properties of the intra-orally used wires showed decreased values of the parameters.

Mechanical properties of contemporary orthodontic adhesives used for lingual fixed retention

Objective:The aim of the present study was to test the mechanical properties of different adhesives used in orthodontics for fixed retainers and to investigate their possible interrelations.Materials and methods:Specimens of six different adhesive resins were prepared: Transbond XT, Transbond LR and an experimental BPA-free orthodontic adhesive, as well as IPS Empress Direct (IPS-ED), ZNano and Accolade. The mechanical properties tested were Martens hardness (HM), indentation modulus (EResults:Significant differences were identified among all the materials tested for HM, with Transbond LR presenting the highest value. This resin presented the highest EConclusions:The materials tested demonstrated significant differences in their mechanical properties, and thus differences in their clinical performance are anticipated.

Magic Clips for Fixed Retention

Despite major advances in orthodontic tooth movement, orthodontic retention remains a major problem. It has been estimated that only 10% of the population who have received orthodontics are still in acceptable occlusion as judged by orthodontists 20 years after retention. One of the means of maintaining stability has been the use of fixed retainers. This article will describe a very simple and effective method of stabilizing the retainer during bonding using clip. The method of stabilizing the fixed retainer described in this article is the most simplest, economical, least time consuming and also very effective method.

Evaluation and comparison of root resorption between tooth-borne and tooth-tissue borne rapid maxillary expansion appliances: A CBCT study

ABSTRACT Objective: To compare volumetric root resorption after rapid maxillary expansion (RME) between tooth-borne and tissue-borne appliances using CBCT. Repair in resorption cavities after 6 months of fixed retention was also compared. Materials and Methods: A sample of 33 subjects were randomly divided into two groups: Hyrax (n = 16) and Haas (n = 17). CBCT scans were taken 6 months before expansion, immediately after expansion, and 6 months after fixed retention. Mimics Innovation V 16.0 software was used for segmentation and volumetric measurement of 198 teeth. Bland-Altman plots, independent samples t test, repeated measures analysis of variance, and the Friedman test were used for statistical analysis. Results: Differences in root resorption after RME and repair after retention were not significant between the hyrax and Haas appliances or between male and female. Significant differences were found between preexpansion and postexpansion root volumes in the first premolars and molars—even in unattached second premolars. When the percentage of root volume loss is considered, no significant difference was found between the first premolar, second premolar, and first molar. Volumetric changes after 6 months of retention were not statistically significant. Conclusions: More resorption was observed in the Hyrax expander group. But it was not statistically significant. Repair was observed after 6 months of retention. Heavy RME forces affected premolars and molar similarly.