The retention characteristics of Hawley and vacuum-formed retainers with different retention protocols.

BACKGROUND: 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. MATERIAL AND METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Comparison of Antibacterial Effects of ZnO and CuO Nanoparticles Coated Brackets against Streptococcus Mutans.

STATEMENT OF THE PROBLEM: During the orthodontic treatment, microbial plaques may accumulate around the brackets and cause caries, especially in high-risk patients. Finding ways to eliminate this microbial plaque seems to be essential. PURPOSE: The aim of this study was to compare the antibacterial effects of nano copper oxide (CuO) and nano zinc oxide (ZnO) coated brackets against Streptococcus mutans (S.mutans) in order to decrease the risk of caries around the orthodontic brackets during the treatment. MATERIALS AND METHOD: Sixty brackets were coated with nanoparticles of ZnO (n=20), CuO (n=20) and CuO-ZnO (n=20). Twelve uncoated brackets constituted the control group. The brackets were bonded to the crowns of extracted premolars, sterilized and prepared for antimicrobial tests (S.mutans ATCC35668). The samples taken after 0, 2, 4, 6 and 24 hours were cultured on agar plates. Colonies were counted 24 hours after incubation. One-way ANOVA and Tukey tests were used for statistical analysis. RESULTS: In CuO and CuO-ZnO coated brackets, no colony growth was seen after two hours. Between 0-6 hours, the mean colony counts were not significantly different between the ZnO and the control group (p>0.05). During 6-24 hours, the growth of S.mutans was significantly reduced by ZnO nanoparticles in comparison with the control group (p< 0.001). However, these bacteria were not totally eliminated. CONCLUSION: CuO and ZnO-CuO nanoparticles coated brackets have better antimicrobial effect on S.mutans than ZnO coated brackets.

Are Mesenchymal Stem Cells Implanted in Lip Defect Capable of Returning Orbicularis Oris Muscle Function?

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 × 7 × 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 × 5 × 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.

Effectiveness of Er:YAG laser-aided fiberotomy and low-level laser therapy in alleviating relapse of rotated incisors.

INTRODUCTION: In this study, we compared the effectiveness of laser-aided circumferential supracrestal fiberotomy (CSF) and low-level laser therapy (LLLT) with conventional CSF in reducing relapse of corrected rotations. METHODS: The study included 24 patients who were at the finishing stage of orthodontic treatment and had at least 1 maxillary incisor with 30° to 70° of rotation before starting therapy. The subjects were divided into 4 groups by treatment: conventional CSF, Er:YAG laser-aided CSF, LLLT, and control. After alginate impressions were taken, the archwire was sectioned from the experimental incisors, and they were allowed to relapse. The second impression was taken 1 month later, and the degree and percentage of relapse were calculated in photographs taken from the dental models. Gingival recession, pocket depth, and pain were also measured in the CSF groups. RESULTS: The mean percentages of relapse were 9.7% in the conventional CSF, 12.7% in the Er:YAG laser-aided CSF, 11.7% in the LLLT, and 27.8% in the control groups. Relapse was significantly greater in the control than the experimental groups (P <0.05), which were not statistically different from each other. The changes in sulcus depth and gingival recession were small and not significantly different among the CSF groups (P >0.05), but pain intensity was greater in subjects who underwent conventional CSF (P = 0.003). CONCLUSIONS: Er:YAG laser-aided CSF proved to be an effective alternative to conventional CSF in reducing rotational relapse. LLLT with excessively high energy density was also as effective as the CSF procedures in alleviating relapse, at least in the short term.

Evaluation of tooth size in patients with congenitally-missing teeth.

BACKGROUND AND AIMS: Hypodontia is a common developmental abnormality of dentition. This study aimed to determine tooth width in patients affected with mild hypodontia and compare the results with a control group without tooth agenesis. MATERIALS AND METHODS: The orthodontic records of 25 patients with congenital missing of one or two teeth (hypodontia group), and 25 subjects with full dentition (control group) were selected. The greatest mesiodistal width of each tooth was measured on the study models by a digital caliper. Tooth width measurements were compared between the groups using a student t-test at p < 0.05 of significance. RESULTS: Patients with hypodontia showed narrower teeth than the control subjects. The differences in tooth size between the two groups were statistically significant for the first and second premolars and first molar in the maxillary right and for the second premolar in the maxillary left quadrants (p < 0.05). In the lower arch, the first and second premolars and also first molar in both sides of hypodontia patients demonstrated significant reduction in tooth size compared to the control group (p < 0.05). CONCLUSION: These findings suggest that patients with mild hypodontia have narrower teeth than normal subjects especially in posterior segments, which may have clinical implications during the orthodontic treatment process.

Shear bond strength and antibacterial effects of orthodontic composite containing TiO2 nanoparticles.

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.

The effect of fluoride exposure on the load-deflection properties of superelastic nickel-titanium-based orthodontic archwires.

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 degrees 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.

Effects of a simulated oral environment and sterilization on load-deflection properties of superelastic nickel titanium-based orthodontic wires.

UNLABELLED: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Comparison between the external gonial angle in panoramic radiographs and lateral cephalograms of adult patients with Class I malocclusion.

The external gonial angle is an important angle of the craniofacial complex. It is significant for the diagnosis of craniofacial disorders. Lateral cephalogram and orthopantomograms can be used to determine this angle. In this study, we compared the external gonial angle determined from the two mentioned radiographs in Class I patients. We collected the radiographs of 70 patients with Angle's Class I (22 men and 48 women). The patients' age ranged from 15-30 years with a mean age of 18.24 years. The data gained were statistically evaluated by t-test. The following results were obtained. The mean value of the gonial angle in the lateral cephalogram was 125.00 degrees (men, 124.9 degrees and women, 125.04 degrees ) and in the orthopantomogram was 124.17 degrees (men 123.68 degrees , women 124.39 degrees ). The difference between these rates was 0.83 degrees (men 1.22 degrees , women 0.64 degrees ) and not significant (P = 0.406). Based on the obtained results, we can conclude that panoramic radiography can be used to determine the gonial angle as accurately as a lateral cephalogram. In addition, we can determine the right and left gonial angles of a patient in the orthopantomogram without interferences due to superimposed images of anatomical structures in a lateral cephalogram. For determination of the gonial angle, an orthopantomogram may be a better choice than a lateral cephalogram.