Evaluation of Stress Pattern Caused by Mini-Implant in Mandibular Alveolar Bone with Different Angulations and Retraction Forces: A Three-Dimensional Finite Element Study

Objective:The objective of the study was to evaluate the stress pattern in cortical and cancellous bones, periodontal ligament, and in the implant itself when a mini-implant (MI) is inserted in the inter-radicular space between mandibular first molar and second premolar at various angulations and different retraction forces.Methods:Finite element study was conducted with MI insertion at 30°, 45°, 60°, 75°, and 90° angulations in the mandibular posterior region (between second premolar and first molar). At these angulations, horizontal forces of 150, 200, and 250 g were applied to the middle of the MI head. von Mises stress values were then evaluated using the ANSYS software.Results:Highest von Mises stress values were detected in the MI itself, followed by cortical bone, cancellous bone, and periodontal ligament. The von Mises stress values in cortical bone were highest at 30° angulation and lowest at 90° angulation. In the cancellous bone, the stress value was found to be maximum at 90°. The von Mises stress values in the MI were lowest at 90°. In all four structures, as the load increased from 150 to 250 g, the von Mises stress values increased.Conclusion:The von Mises stress values in the cortical bone, MI, and periodontal ligament were found to be lowest at 90°. Placement of the MI at 90° appears to be an ideal angulation when applied with a horizontal load. Force range used is within clinically recommended levels; however, the increase in load causes an increase in the stress values

An In-Vitro Evaluation of Microbial Adhesion on Different Types of Orthodontic Brackets

Introduction: Information regarding the adhesion of bacterial species and plaque accumulation to bracket material is limited. Adequate information is needed in order to offer patients orthodontic treatment without significantly increasing their risk of developing white spots, caries, or gingival inflammation. Aim: To determine the levels of the caries-inducing S. mutans species on metallic, self-ligating and ceramic brackets and to compare the total bacterial counts and counts of species present on these bracket materials. Materials and Methods: By means of an in-vitro study, six commercially available bracket systems {3M Gemini (A), American Ortho (B), Ormco (C), Begg (D), Ceramic (E) and Self-ligating (F)} were compared. The brackets were bonded in the cell well culture plate and the agar plates were prepared. Brain heart infusion medium including bacteria and artificial saliva was introduced to each bracket system containing 10 premolar brackets and were incubated. After 72 hours, the adherent bacteria were then detached by sonication and the Colony-Forming Units (CFU) of Streptococcus mutans were calculated on each bracket and were analysed using Statistical Package for the Social Sciences (SPSS) software version 17.0 for Windows. Results: Between the different bracket types, significant differences were found in terms of biofilm formation. The Begg brackets showed the least bacterial adhesion and the selfligating brackets showed the highest bacterial adhesion and was statistically significant among all the groups (p<0.05). Ceramic brackets also showed a higher bacterial adhesion after the self-ligating brackets. Among the three groups of metallic brackets, 3M brackets showed the least bacterial adhesion but was statistically insignificant (p>0.05). Conclusion: Different orthodontic brackets serve as different loci for biofilm formation showing that the Begg brackets are the most hygienic among all the brackets taken in this study

An in vitro comparison of resistance to second and third order archwire activations of three different varieties of esthetic brackets

Background: When ceramic brackets were introduced as an esthetic alternative to the stainless steel brackets, it was a step ahead in the use of esthetic appliances for orthodontic treatment. Although ceramic brackets had overcome the drawbacks of the initial polycarbonate brackets such as staining and bracket slot distortion, they posed an altogether different problem. This was on account of the physical properties of the ceramic material, namely brittleness. Purpose of the Study: The purpose of this study is to investigate the physical properties of three different varieties of esthetic brackets, i.e., "MXI" ceramic bracket, "Spirit MB" bracket (Ormco), a composite bracket with metal slot reinforcement and the third one fiber bracket, with silicious copolymer, Natura (Leone Co.). Aims and Objective of the Study : The objective of this study is to compare the torsional resistance of the brackets and resistance of brackets to second order archwire activations. Conclusion: The strength of the selected brackets was more than sufficient to withstand orthodontic load without any fracture or deformation