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Pyknodysostosis is a rare bone disease that has autosomal dominant trait. It is characterized by short stature, diffuse osteosclerosis, acro-osteolysis, finger, and nail abnormalities. Other features include open fontanelles and sutures, relative proptosis and obtuse mandibular gonial angle with relative mandibular prognathism. Intraoral features such as dental abnormalities also have been reported. In this report, a case of pyknodysostosis in a 9-year-old boy is presented. Most of the observed features were comparable to the other case reports but some findings such as repeated chest infection, sleep apnea, kyphosis, scoliosis, root shortness, pulp narrowing, supernumerary and hypodontia could not be observed in this case. Instead, in this patient features such as anterior open bite and decreased anterior tooth display, not reported in other cases, was evident.

Background and Aims: Since there is a relationship between the tooth size and race, it seems that having statistical information about the tooth size in a society in which the orthodontic treatments are done, is very important. The aim of this study was to determine the relationship between the mesiodistal width of permanent incisors and first molars in both jaws with unerrupted permanent canine and premolars. New regression equations for prediction of the sum of mesiodistal width of canine and premolars were established. Materials and Methods: A total of 715 dental casts (526 female, 189 male) were recruited from the department of orthodontics of Shiraz dental school and private offices of orthodontists for this cross sectional study. The greatest mesiodistal widths of all teeth were measured with digital caliper with accuracy of 0.01 mm. All data were analyzed with SPSS software and Pearson Correlation, independent T-test, paired sample T-test and multiple linear regression tests. Results: Tanaka-Johnston equations and Moyer's prediction tables had significant difference with mesiodistal dental width of south Iranian population, so new regression equations (based on incisors and first molars) for different jaws and sexes were presented in this study for south Iranian population. The best suggested regression is the regression that is based on all maxillary and mandibular incisors and first molars and has 12 variables. The suggested regression for prediction of maxillary canine and premolars based on the summation of mesiodistal width of all incisors and first molars in both jaws was Y=0.177X+4.227 and for prediction of mandibular canine and premolars was Y=0.188X+2.730, which a the greatest in r2 prediction of unerrupted teeth in comparison with the regressions based on incisors alone or incisors and first molars in one jaw. Conclusion: Tanaka-Johnston and Moyer's prediction tables are overestimated the actual size of south Iranian's teeth width. So new regression equations based on incisors alone and incisors and first molars are suggested to increase the accuracy of space analysis in both jaws. [ABSTRACT FROM AUTHOR]

Background: The highly prevalent white spot lesions around orthodontic brackets necessitate introducing preventive materials without relying on patient compliance., Objective: To evaluate the antidemineralizing effect of two concentrations of xylitol varnish., Trial Design: Triple-blind, four-arm, parallel-group, single-center, randomized controlled clinical trial., Methods: A total of 120 orthodontic patients were randomly assigned to four groups (n = 30), using a computer-generated randomized block list. The treatment groups were: 10% xylitol, 20% xylitol, 5% fluoride, and placebo. Tooth demineralization was measured with DIAGNOdent at T1 (before treatment), followed by varnish application. At T2 (third month), the varnish was re-applied, and at the third (T2) and sixth (T3) months, and after treatment (T4), the demineralization was measured. The white spot lesion frequency was assessed visually after treatment. The participants, the clinician, and data assessors were all blinded to group assignments., Results: A total of 115 patients underwent per-protocol analyses. At T2, the mean DIAGNOdent numbers in the fluoride and 10% xylitol groups were significantly lower than the placebo group (P = 0.00), with a mean difference of 0.63 (95% CI, 0.15-1.10) and 0.5 (95% CI, 0.04-0.95), respectively. At T3, the fluoride and 10% xylitol groups had significantly lower mineral loss than the placebo group (P=0.046) with a mean difference of 0.52 (95% CI, 0.14-0.89) in the fluoride and 0.45 (95% CI, 0.03-0.86) in the 10% xylitol groups, respectively. However, at T4, only the mean for the 10% xylitol group was significantly different (P=0.049) from the placebo group, with a mean difference of 1.18 (95% CI, 0.42-1.93). Visual assessment showed that after treatment, the prevalence of white spot lesions in the fluoride (P=0.03) and 10% xylitol (P=0.00) groups was less than the placebo group with the odds ratio of 0.67 (95% CI, 0.46-0.96) and 0.43 (95% CI, 0.28-0.64), respectively., Conclusion: The 10% xylitol varnish short-term effects on caries control were significantly greater than 20% xylitol varnish and placebo but similar to fluoride varnish. However, the 10% xylitol long-term effect was almost better than fluoride varnish., Trial Registration: The protocol was registered at IRCT.ir under the code IRCT20180913041032N1., (© The Author(s) 2021. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: This study aimed to compare the effect of Er,Cr:YSGG laser with a tungsten carbide bur in orthodontic finishing on the enamel surface roughness and the heat generated in the pulp chamber. Methods: Before bonding, of 125 intact extracted premolar teeth, 15 teeth were randomly assigned to the control group. Of the remaining 110 bonded teeth, 50 were used to determine the laser parameters, and 60 were included in the main in vitro study. After debonding, the teeth were randomly distributed among four study groups ( n  = 15) for finishing with laser beams (Er,Cr:YSGG, Waterlase) with and without polishing with Sof-Lex discs, and finishing with a bur (tungsten carbide, Reliance) with and without polishing with Sof-Lex discs. The thermal changes were measured during finishing using a thermo-controller-coupled thermocouple placed in the pulp chamber. Enamel surface roughness was evaluated qualitatively under a scanning electron microscope (SEM) and quantitatively under an atomic force microscope (AFM). Results: The thermal changes of the bur group were significantly higher than those in the laser group ( p  = 0.0001). Quantitatively, the surface roughness values of all the study groups were significantly higher than those of the control group ( p  < 0.05), with no significant difference between the study groups ( p  > 0.05). SEM analysis confirmed the AFM measurements. Conclusions: Er,Cr:YSGG can be recommended as an alternative for a carbide bur for adhesive agent removal after orthodontic debonding, considering its mild thermal effect on the pulp. Polishing with Sof-Lex discs did not significantly reduce the surface roughness, regardless of the finishing procedure.

Objective: The aim of this study was to evaluate the effect of intraoral aging and sterilization on the physical properties of rectangular Nickel-Titanium (NiTi), Beta-Titanium and Cooper NiTi (Cu-NiTi) arch wires., Methods: Three types of preformed 0.018×0.025 inch wires: super elastic NiTi wire, Beta-Titanium wire and Cu-NiTi wire (20 of each type) were divided into 4 groups: as-received (T0), autoclave (T1), intra oral aging after sterilization (T2) and intra oral aging (T3). Specimens in T2 and T3 groups were used in oral environment of 30 participants for 8 weeks. In the next step a length of 30mm was cut from both ends of each arch wire, and 120 straight specimens were achieved and tested by Instron for evaluating their load deflection properties. Data were analysed by means of One-way ANOVA and Tukey's (honestly significant difference) HSD tests., Results: In NiTi wire, all conditions led to a significant decrease in deactivation mean load compared with control in most deflections (P=0.000). In Cu-NiTi wire, all conditions led also to a significant decrease in deactivation mean load compared with the control (P=0.000). In Beta-Titanium wire, sterilization had no significant effect on the load deflection properties; but significant increase was observed in T2 (in all deflections) and T3 (in 1.8-1mm) compared with the control., Conclusions: After all conditions, NiTi wire in spite of reduction in stiffness presented a mean load which stayed in category of heavy force. The Cu-NiTi wires saw an improvement in light physiologic force. In contrast, the Beta-Titanium stiffness increased after clinical usage, and the force level remained in the range of heavy force., (Copyright © 2019. Published by Elsevier Masson SAS.)

Class II malocclusion may be caused by the maxillary protrusion or the mandibular retrusion. One treatment method is to use a headgear, which might affect the dimensions of the patient's airway. The aim of this study was to assess the effect of a headgear on the airway dimensions in class II malocclusion patients. A digital search and a manual search were conducted for English-language articles published from January 2000 to December 2018 about human clinical trials, including the usage of a cervical headgear in class II malocclusion patients who had measurable changes in the airway and/or jaw size. The synthesis methods of the study consisted of data concerning the study design, the type of treatment device, the patient's age at the start, the sample size, the treatment duration, the type of radiography, and the results of treatment; this data was extracted and compared. The quality of the selected articles was assessed. All of the studies had a high risk of bias, providing low-quality evidence of the effectiveness of the headgear therapy on the airway dimensions. The conclusions of the articles differed from each other and there were different mechanisms of changes in the jaw or airway dimensions. Therefore, further studies are required to find the clearest results showing the effect of a cervical headgear in class II malocclusion.

Introduction: The aim of this study was to determine the effect of bleaching and desensitizing on shear bond strength (SBS) of metal brackets to enamel., Methods: One hundred extracted human premolar were randomly assigned to 5 groups of 20. In the first group (control), no bleaching or desensitizing agent was used. Groups 2 to 5 were bleached with 37.5% hydrogen peroxide and desensitized with 6.0% potassium nitrate. Surface treatment comprised of etching for 15seconds in groups 1, 2 and 3, Er:yag laser irradiation and etching in group 4 and sandblasting and etching in group 5. Premolar brackets were bonded with Transbond XT and cured for 20seconds and the SBS was tested using a universal testing machine. Adhesive remnant index (ARI) score was used to record the mode of bond failure., Results: No significant difference was found between the mean SBS (MPa) in groups 1(15.22), 4(14.02), and 5(12.62). SBS in group 4 was significantly higher than group 2 (8.15) (P<0.001). Also, SBS in groups 2 (P<0.001) and 3(11.74) (P=0.012) were significantly lower than group 1. An increased frequency of ARI score of 2 and 3 was observed in groups 1, 4 and 5., Conclusions: Bleaching plus desensitizing significantly decreased the SBS of orthodontic brackets. Delaying the bonding procedure for at least 2 weeks or alternative surface treatment methods such as combined laser and acid etching or combined sand blasting and acid etching can improve the SBS., (Copyright © 2019 CEO. Published by Elsevier Masson SAS. All rights reserved.)

Introduction: The number of adult patients seeking orthodontic treatment has been consistently increasing. Since the placing of the final restoration must be postponed until the completion of the orthodontic treatment, provisional restoration is recommended for the duration of the orthodontic treatment. These surfaces have special chemical properties, which necessitate the orthodontists to prepare the bonding area with special measures., Methods: Polycarbonate and polymethylmethacrylate (PMMA) crowns (n=80) were randomly subdivided into 4 groups. Conditioning methods were grinding, sandblasting, CO 2 laser and methyl methacrylate application. Samples underwent SBS testing. A scanning electron microscope (SEM) analysis was carried out. The data was analysed with ANOVA, Student t-test and Post-hoc test. Adhesive remnant index (ARI) was analysed with Chi 2 test., Results: In all surface treatments, the mean Shear Bond Strength (SBS) of PMMA was significantly higher than that of polycarbonate (P<0.001). In the polycarbonate groups, there was a significant difference between the mean SBS of the four treatment methods (P<0.001). However, there were no significant differences in PMMA group (P=0.076). In both crown materials, the mode of the failure was adhesive type, regardless of the conditioning method (P>0.05)., Conclusions: PMMAs rendered higher bond strength than polycarbonates. In PMMA, all the surface treatment methods resulted in acceptable bond strength. However, if bonding the brackets to polycarbonate crown is needed, other conditioning methods are preferred over CO 2 laser., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Introduction: There are controversies regarding the most reliable conditioning method of the aged composite surface to ensure optimum bond strength. The purpose of this study was to evaluate the shear bond strength of metal brackets to microhybrid composite restorations after different surface preparation techniques., Materials and Methods: A total of sixty microhybrid composite samples were prepared using upper right central incisor celluloid crown as a mold. Samples were treated with 4 different surface conditioning methods: (1) etching, (2) sandblasting, (3) grinding, and (4) CO 2 laser irradiation. Samples were then bonded with metal brackets and underwent shear bond strength testing. A scanning electron microscope was carried out and the data was analysed by one-way ANOVA and post-hoc Tukey test. Bond failure was examined by stereomicroscope and scored based on adhesive remnant index (ARI). Kruskal-Wallis test was used to compare ARI values (α=0.05)., Results: Shear bond strength values in the sandblasting group (17.18±1.53MPa) were significantly higher than the other groups. There was no significant difference between the grinding (12.87±3.38MPa) and laser (11.08±1.37MPa) groups (P=0.09). The lowest values were recorded in the etching group (6.78±1.69MPa). There was a significant difference in ARI scores among the four groups (P<0.001). ARI scores were mostly 2 and 3 in the sandblasting and grinding group, while in the etching and laser groups ARI was mostly 0 and 1., Conclusions: Surface preparation by sandblasting and CO 2 laser provides clinically acceptable results with regards to bond strength and ARI score, however grinding and acid etching failed to produce the same results., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Background. Tooth displacement changes the periodontium. The aim of orthodontic treatment is desired tooth movement with minimum side effects on the alveolar bone quality. The aim of the present study was to assess changes of alveolar trabeculation in children, young adults and adults and the two genders. Methods. In this cross-sectional study, 63 patients who had been treated in Department of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran, were chosen with convenient sampling method. They were divided into three groups based on their age. Their digitized panoramic radiographs (PRs) were evaluated at six interdental sites from the mesial aspect of the mandibular second molars to the distal aspect of the mandibular first premolars using a visual index. The trabeculation pattern was assigned as either dense (score 3), dense-sparse (score 2) or sparse (score 1). Data were imported to SPSS. Mean of the scores before treatment (score B) and mean of them after treatment (score A) were compared for each group with paired t-test. Changes between score B and sore A of the groups were compared using one-way ANOVA and post hoc tests. Results. Mean score A was significantly higher than mean score B in children (P = 0.001). In contrast, mean score A was significantly lower than mean score B in young adults (P = 0.003). Conclusion. Orthodontists should be cautious when treating young adults and adults regarding the probable, yet possibly temporary, negative effects of orthodontic therapy on the alveolar bone quality.

Introduction: The aim of this study was to determine the preferred lip position in silhouette profiles with different amounts of divergence., Methods: A normal profile was constructed based on normal values and was altered using software (Photoshop CS, version 8.0; Adobe Systems, San Jose, Calif) to produce a series of 15 profiles in 3 sets (straight, anterior, and posterior divergent). Each set consisted of 5 photographs with different lip positions from -4 mm to +4 mm in 2-mm increments. We asked 240 people in 5 panels (79 senior dental students, 26 orthodontists, 27 maxillofacial surgeons, 27 prosthodontists, and 81 laypeople) to rate the profiles. Mann-Whitney and Kruskal-Wallis tests, and intraclass correlation coefficients were used to analyze the data., Results: In the anterior and posterior divergent profiles, most groups tended to prefer the original lip positions for both the male and female profiles. In the straight divergent profile, the results were scattered and inconsistent in the different groups. In the posterior divergent profile, the orthodontists and the surgeons selected the 4-mm lip retrusion as the least attractive, and other groups selected the 4-mm lip protrusion as the least attractive. In the anterior and straight divergent profiles, all groups were unanimous in the selection of the 4-mm lip protrusion as the least attractive images. Significant differences were found between the raters in the rankings of some images. No significant difference was found between the male and female raters in the rankings of the profile images., Conclusions: It is important to establish a normal lip position, especially for a patient with an anterior or a posterior divergent profile. Posterior divergent patients should be treated cautiously so that excessive lip retrusion does not result., (Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Statement of the Problem: Some studies have reported the bond strength to be significantly lower in fluorotic enamels than the non-fluorosed., Purpose: The purpose of this study was to evaluate the shear bond streongth of metallic brackets to non-fluorosed and fluorosed teeth after different enamel conditioning., Materials and Method: A total of 176 freshly extracted human premolars (88 non-fluorosed and 88 fluorosed teeth) were used in this study for bonding the metallic brackets. Teeth with moderate fluorosis were used according to Thylstrup and Fejereskov index (TFI). Eighty non-fluorosed and 80 fluorosed teeth (TFI=4-6) were randomly divided into 8 equal groups of 20 teeth each. The remaining 16 teeth were used for scanning electron microscopy observation. The enamel surface was conditioned by 4 methods: acid etching  for 30 sec, acid etching for 120 sec, air abrasion followed by acid etching, and Er: YAG laser etching followed by acid etching. The morphology of etching patterns in different groups was studied under scanning electron microscope., Results: The shear bond strength of fluorosed teeth to the brackets was significantly lower than non-fluorosed ones (p= 0.003). The shear bond strength of laser-acid groups in both non-fluorosed and fluorosed teeth was significantly lower than other groups (p< 0.001). Weibull analysis indicated that the chance of failure under the applied force was different between fluorosed and non-fluorosed group. The scanning electron microscope observations revealed that the fluorosed teeth treated with phosphoric acid had fewer irregularities compared to non-fluorosed teeth. The most irregularities were detected in the teeth conditioned with phosphoric acid for 120 seconds., Conclusion: Fluorotic enamel adversely affects the bond strength of orthodontic brackets. None of the conditioning methods tested in this study could significantly improve shear bond strength of metallic brackets. Er: YAG laser conditioning followed by acid further reduced the bond strength in non-fluorosed and fluorosed teeth.

Introduction: The smile is a key facial expression, and a careful assessment of the facial profile in smiling is an essential part of a complete orthodontic diagnosis. The aim of this study was to determine the preferred maxillary incisor inclination in the smile profile with regard to different mandibular positions., Methods: A smiling profile photograph of a man with normal facial profile features was altered digitally to obtain 3 different mandibular sagittal positions in 4-mm decrements or increments from -4 to +4 mm. In each mandibular position, the inclination of the maxillary incisors was changed from -10° to +10° in 5° increments. A total of 234 raters (72 senior dental students, 24 orthodontists, 21 maxillofacial surgeons, 25 prosthodontists, and 92 laypeople) were asked to score each photograph using a Likert-type rating scale. Mann-Whitney, Kruskal-Wallis, and intraclass correlation coefficient tests were used to analyze the data., Results: In retruded and protruded mandibles, normal incisor inclination and the most retroclined incisors were selected as the most and the least attractive images, respectively, by almost all groups. With an orthognathic mandible, the image with the most retroclined incisors was selected as the least attractive, but the raters were not unanimous regarding the most attractive image. The intraclass correlation coefficient was 0.82 (high level of agreement). Also, the sex of the raters had no effect on the rating of the photographs., Conclusions: It is crucial to establish a normal incisor inclination, especially in patients with a mandibular deficiency or excess. An excessive maxillary incisor lingual inclination should be avoided regardless of the mandibular position., (Copyright © 2015 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Background: This study aims to evaluate and compare the effect of pre-procedural administration of acetaminophen, ibuprofen, and meloxicam in reducing pain after separator placement., Methods: Three hundred twenty-one patients who needed orthodontic treatment and aged above 15 were randomly assigned to one of the three study groups: group A: 650 mg acetaminophen, group B: 400 mg ibuprofen, and group C: 7.5 mg meloxicam. All subjects received a single dose of medication 1 h prior to separator placement. Using visual analog scale, patients recorded their pain perception during rest, fitting posterior teeth together, and chewing at time intervals of immediately, 2, 6, 24, and 48 h after separator placement., Results: There was no significant difference between acetaminophen, ibuprofen, and meloxicam in post-separator placement pain control when administered 1 h before the procedure. In all the groups, at rest, pain level elevated after separator placement and reached its peak at 24 h and then subsided until 48 h. But during chewing and fitting of the posterior teeth, some of the groups reached a peak in pain at 48 h. No significant difference was found in pain experience between males and females., Conclusions: Meloxicam can be used as an effective analgesic in orthodontic pain control considering it has less gastric side effects compared to the conventional nonsteroidal anti-inflammatory drugs., Trial Registration: Iranian Registry of Clinical Trials, IRCT2015041821828N1.

Objective: This study evaluated the effect of superpulse CO2 laser irradiation and deglazing of porcelain surfaces on the shear bond strength (SBS) of metal orthodontic brackets, and compared it with two conventional etching techniques., Methods: Forty-eight Feldspathic porcelain fused to metal specimens embedded in cylindrical acrylic resin tubes were fabricated, and all the specimens were divided into four groups. In Group 1, the specimens were roughened with a diamond bur and etched with hydrofluoric acid (HFA) gel for 4 min. In Group 2, the specimens were roughened with a bur and irradiated by a CO2 laser with a 2 W power setting for 20 sec. In Group 3, the specimens were only irradiated by a CO2 laser. In Group 4, the porcelain surface was sandblasted with 50 μm aluminum oxide. Before bonding, the bracket silane was applied on the porcelain surfaces. SBS was evaluated by a Universal testing machine (Zwickroll, Germany). The remaining adhesive after the bond failure was evaluated using an adhesive remnant index (ARI). Statistical analysis was conducted by analysis of variance (ANOVA), Tukey, and Kruskal-Wallis tests., Results: ANOVA revealed significant differences in SBS among the four groups (p<0.001). Group 1 demonstrated significantly higher bond strength (13.13±2.47) when compared with the other groups. Group 2 showed higher bond strength (9.60±1.91) when compared with group 4 (6.40±1.67) (p=0.016). Group 1 displayed the highest ARI scores among the groups., Conclusions: Deglazing combined with HFA etching produced the highest bond strength, but CO2 laser irradiation provided adequate bond strength and allowed for elimination of the HFA step. Deglazing is not recommended as a preliminary step before CO2 laser conditioning.

Introduction: The dental students, the same as other students, during their academic courses are required to learn a wide range of scientific subjects. Obviously, choosing the inappropriate method of study leads to confuse and disenchantment of students and it causes wasting of their energy. The purpose of this study was to assess the existing strengths and weaknesses of the skills and study habits in Dental Students of Shiraz University of Medical Sciences in 2009-10., Materials and Methods: In this cross-sectional study, all of the dental students (n = 274), who studied at the time of study at all levels in the academic year of 2009-10, were selected by the census. Data were collected by using the Huston University questionnaire consisted of two parts of demographic questions and 64 specific areas of study skills in eight domains of time management, concentration/memory, study aids/note taking, test strategies, information processing, motivation, self-assessment/reading, and writing skills. Following the retranslation of the questionnaire, the validity was confirmed by using the content validity method. The reliability was obtained by using the Cronbach's Alpha of 0.92. The data were analyzed with SPSS software version 17 and using analytical statistic tests., Results: Students who have previously participated in the study skills workshops had stronger skills in comparison with the students who had not participated in these workshops. Time management skills (P = 0.04), motivation (P = 0.0001) and information processing (P = 0.03) in students with professional status were in a more favorable position and showed significant differences in terms of educational levels. The study skills mean score of the students living in student housings in comparison with the other students were significantly higher (P = 0.04). Marital status showed no significant differences in reading skills., Conclusion and Recommendations: The review of study skills in the undergraduate and post-graduate dental students indicated that the residents had higher reading skills. By recognizing the existing strengths and weaknesses and holding programs through counseling centers can develop the study skills in the students.

Background: The aim of this prospective clinical study was to compare the mean durability and the failure rates of two types of orthodontic retainers., Methods: Orthodontic patients (142) aged between 14 and 28 years were recruited in this study. The polyethylene woven ribbon (Ribbond, Seattle, WA, USA) retainer was compared with a 0.0175-in flexible spiral wire (Respond, Ormco, Glendora, CA, USA) retainer. When treatment was completed, the retainers were bonded from canine to canine in the maxillary and the mandibular arches of the participants. In the follow-up visits, the patients were re-evaluated every 3 months over a period of 18 months. The time taken for the retainers to remain without any fracture was appraised. Kaplan-Meier analysis and the logrank test were employed to identify significant differences in the survival functions between the groups. The rates of the retainers' failure between the groups were analyzed using Chi-square test., Results: It was revealed that the mean survival of the flexible spiral wire retainer was 15.34±0.47 and 15.60±0.42 months in the maxillary and mandibular arches, respectively. The mean survival of the ribbon retainer was 13.95±0.55 and 14.26±0.57 months in the maxillary and mandibular arches, respectively. Ribbon retainers showed a failure rate of 50% in the maxillary and 42.6% in the mandibular arches. Flexible spiral retainers showed a failure rate of 36.5% in the maxillary and 37.8% in the mandibular arches. The differences were not statistically significant. Regarding the evaluation period, the differences had limited clinical significance., Conclusion: The mean survival time and the failure rates of the polyethylene woven ribbon retainer were comparable to the flexible spiral wire retainer during the 18 months after orthodontic treatment.

Bond failure after rebonding for newly placed brackets can be reduced by appropriate enamel surface treatment. This in vitro study investigated the effect of two enamel surface treatments on the bond strength of metallic brackets in the rebonding process. After debonding the brackets and removing the residual adhesive on the enamel surface of 50 upper premolar teeth, the teeth were divided into two equal groups. In the first group, the enamel surface was etched with phosphoric acid 37 per cent, and in the second group, the teeth were sandblasted prior to acid etching. After bonding of the new brackets, the shear bond strength (SBS), probability of bond failures, and adhesive remnant index (ARI) were determined and compared with the t-test, Weibull analysis, and chi-square test. Mean SBS in both groups did not differ significantly (P = 0.081). Most bond failures occurred with ARI scores of 2 and 3, and the difference between the two groups was statistically significant (P < 0.001). Weibull analysis showed that for a given stress, the probability of failure differed between groups. Enamel surface preparation with sandblasting prior to acid etching did not significantly improve SBS in bracket rebonding and left more residual adhesive remnants on the enamel surface.