Barat-Ali Ramazanzadeh

This study aimed to compare the effectiveness of two different protocols of wearing vacuum-formed retainers (VFRs) with the standard protocol of wearing Hawley retainer in maintaining the results of orthodontic treatment. This single-blind randomized clinical trial consisted of 90 patients who finished orthodontic treatment at the Department of Orthodontics of Mashhad Dental School, and required removable retainers. The participants were randomly divided into 3 groups and received the following treatments. Group 1: Hawley retainers (4 months full-time and then night-only); group 2: VFR_4M (4 months full-time and then night-only); group 3: VFR_1W (1 week full-time and then night-only). The study models were prepared after debond and at 4 and 8 months later, and intercanine width, intermolar width, arch length and the Little's irregularity index were compared between groups. No significant differences were found in intercanine and intermolar widths between groups (P<05). Upper arch length was significantly lower in Hawley group than the two VFR groups (p<0.05), but lower arch length values were comparable. Upper irregularity index was significantly lower in two VFR groups compared to Hawley group (p<0.05), whereas in the lower jaw, only VFR_4M group showed significantly lower crowding than Hawley group (p<0.05). Both retention regimens of VFRs were more effective than Hawley retainer in maintaining arch length and tooth alignment in the upper arch. For better incisor alignment in the lower jaw, the patients should be advocated to wear VFR 4 months full-time and then at night instead of wearing Hawley retainer. Key words:Essix, Hawley retainer, orthodontic treatment, retention, vacuum-formed retainer.

Introduction: This study aimed to evaluate the amount of orbicularis oris muscle formation and function after using scaffold-free cells and mesenchymal stem cells scaffold in repaired cleft lip of rats. Methods: Forty male Wistar rats were used. A triangular cut (7 x 7 x 4 mm) was made on the upper lip of 30 rats and then divided into 3 equal groups. In the first group (control), the defected cuts were closed by routine surgical procedures. The second group consisted of cell scaffold and the third scaffold-free cells (5 x 5 x 3) in the area of the incision. Two months after restoration, muscle electromyography activity was examined alongside 10 normal rats and tissue samples were histologically examined. Data were analyzed statistically by SPSS software and ANOVA and the Kruskal-Wallis test. The significance level was considered at P < 0.05. Results: Electromyography activity in second and third groups was not significantly different from each other and with normal muscle. The control group had, however, higher activity than normal muscle (P < 0.001). The amount of newly formed muscle tissue in the scaffold group had a clear statistical difference with the cell scaffold (P = 0.018) and control group (P < 0.001). Furthermore, the inflammatory reaction showed a significant statistical difference in the control and scaffold group (P = 0.001) and the scaffold and cell-scaffold groups (P = 0.007). There was no significant difference in the number of formed fibroblast cells and collagen tissue in the area between the 3 groups. Conclusions: The results of this study show that extracellular matrix scaffold can reduce tension in the repaired cleft lip area by increasing muscle formation and decreasing scar tissue contraction, confirming the benefits of this type of scaffold.

Nanofillers can reduce enamel demineralization without compromising physical properties of the composite. The aim of this study was to evaluate shear bond strength (SBS) and antibacterial effects of an orthodontic composite after adding titanium oxide (TiO₂) nanoparticles. Light cure orthodontic composite paste (Transbond XT) was blended with TiO₂ nanoparticles. A total of 30 extracted premolars were randomly allocated into two groups of 15. In order to bond brackets, Transbond XT adhesive and nanocomposite were used in each group, respectively. SBS of two groups were determined, and the adhesive remnant index (ARI) scores were assessed. A total of 45 composite discs specimen were prepared. Of the 45 discs, 30 discs were made from nanocomposite and tested for antibacterial properties immediately and 30 days after curing by direct contact test. The antibacterial properties of the remaining 15 discs that were made from the conventional composite were tested immediately after curing as control group. Student’s t-test and chi-square tests were used to analyse the data with the significance level of 0.05. No significant difference was found between SBS of conventional and nanocomposites, 24 hours after curing (P = 0.58). Chi-square test showed that ARI scores of two groups were not significantly different after debonding (P = 0.69). Comparison of antibacterial effects between conventional and nanocomposite demonstrated significant difference between two groups, with nanocomposites having a higher antibacterial activity (P = 0.03). Colony count revealed no significant difference in bacterial growth immediately and 30 days after curing in nanocomposite group. Adding TiO₂ nanoparticles to orthodontic composite enhances its antibacterial effects without compromising the SBS.

Background: It has been demonstrated that fluoride prophylactic agents may cause hydrogen absorption in NiTi wires and degrade their mechanical properties. Aims: To investigate the effect of a fluoride mouthwash on load-deflection characteristics of three types of nickel-titanium-based orthodontic archwires. Methods: Twenty maxillary 0.016 inch round specimens from each of the single-strand NiTi (Rematitan ‘Lite’), multi-strand NiTi (SPEED Supercable) and Copper NiTi (Damon Copper NiTi) wires were selected. The specimens were kept in either 0.2% NaF or artificial saliva solutions at 37°C for 24 hours (N = 10). The wire load-deflection properties were measured by a Zwick testing machine, using a three-point bending test. An un-paired student’s t -test, a one-way ANOVA and a Tukey post-hoc test were used to assess statistical significance. Results: Immersion in NaF solution affected the load-deflection properties of NiTi wires. The unloading forces at 0.5 and 1.0 mm deflections were significantly lower in fluoride-treated specimens compared with the control groups ( p < 0.05). Unloading forces at 1.5, 2.0 and 2.5 mm deflections were not statistically different between fluoride- and saliva-treated specimens ( p > 0.05). Conclusions: The results suggested that subjecting NiTi wires to fluoride agents decreased associated unloading forces, especially at lower deflections, and may result in delayed tooth alignment.

The aim of this study was to evaluate the load-deflection characteristics of three types of nickel-titanium wires and investigate the effects of recycling on superelastic properties of them. Thirty specimens for any of the single-strand Ni-Ti (Rematitan "Lite'), multi-strand Ni-Ti (SPEED Supercable) and Copper Ni-Ti (Damon Copper Ni-Ti) were tested. Ten specimens of each wire were subjected to three point bending test in the as-received condition (T0). The remaining wires were kept in a simulated oral environment for 2 months. Then, half of these specimens were tested for their load-deflection properties (T1), while the others were autoclave sterilized before testing (T2). Statistical analysis was performed by one-way ANOVA and Tukey test. Rematitan "Lite"showed significantly greater force than Damon Copper Ni- Ti and Damon Copper Ni-Ti, demonstrated significantly greater force than Supercable (p < 0.05). The effect of recycling on bending properties of nickel-titanium wires was significant (p < 0.05). T1 wires were generally associated with significantly lower forces than T0 specimens in deflections less than 2.0 mm, while load-deflection characteristics of T2 wires were not considerably different from those of T0 specimens. Supercable is useful when very light force is needed during orthodontic treatment, for example in severe crowding cases and traumatized teeth. Damon Copper Ni-Ti may be suitable for routine orthodontic treatment in adolescent and adult patients. It is suggested that clinicians who want to recycle nickel-titanium wires use autoclave sterilization.

Facial soft tissue cephalometric parameters are specific to each society. These measurements should be considered during planning treatment for orthodontic patients. We establish lateral cephalometric facial soft tissue norms in adolescent boys and girls with normal occlusion in Mashhad in the northeast of Iran, and compare them with those of other societies.

Objective: This study evaluated Sodium Fluoride mouth rinse effects on elastic properties of different elastomeric chains. Study design: In this in vitro experiment, two orthodontic chains were tested. In the first group, they were stored in artificial saliva for the entire duration, and in the second group they were immersed daily in 0.05% NaF mouth rinse for 1 minute, artificial saliva–NaF mixture for 30 minutes, and then in artificial saliva for the rest of the day. Specimens were tested at baseline, 1 hour, 24 hours, 1, 2 and 3 weeks and then the displacement of specimens to obtain 150g and 300g, also the applied force after stretching them to 100% of their original length were evaluated. Results: In contrast to force degradation, chains of both companies required more displacement to achieve both forces in the saliva- NaF mixture than saliva itself; however, the difference was only significant for the 300g force (P = 0.020). American Orthodontics chains required more displacement than Dentaurum chains to obtain both forces, also they had more load relaxation (P<0.001). Conclusions: Daily use of NaF mouth rinse does not affect force degradation and the displacement of both chains to achieve conventional orthodontic forces, but for higher force levels the displacement increase is statistically significant.

The aim of this study was to compare the effects of orthodontic extrusive and intrusive forces on histological changes of the human dental pulp. In this clinical trial, 52 sound upper first premolars from 26 patients scheduled for extraction for orthodontic reasons were selected. They were divided into 2 groups, based on the time intervals for histological evaluation (3 days and 3 weeks). In each group, 10 teeth received orthodontic extrusive forces, 10 teeth underwent intrusive forces, and 6 teeth served as controls. After each period, teeth were extracted and prepared for histological examination under light microscopy and some histological parameters were evaluated. The data were statistically analyzed by Kruskall-Wallis and Mann Whitney tests. Of the parameters evaluated, just vacuolization and disruption of the odontoblastic layer showed statistically significant differences between the control group and both of the experimental groups in each test period (P < 0.05). Additionally, there was no significant difference between 3-day and 3-week intervals in each experimental group, except for fibrosis in the extrusive group which significantly increased after 3 weeks of force application (P = 0.001). Histological pulp changes following extrusive and intrusive force applications for 3 days and 3 weeks show no difference from each other. (J Oral Sci 51, 109-115, 2009)