Does mechanical locking-base ceramic brackets reduce cracks at debonding?

Objectives: Debonding of chemically bonded ceramic brackets has been mostly led to enamel damages. This study aimed to evaluate enamel cracks followed by debonding ceramic brackets with mechanical retention. Study Design: Sixty extracted human premolar teeth were randomly divided into two groups. Metallic brackets and recently available ceramic brackets with mechanical retention were bonded to the teeth in first (MB) and second (CB) group respectively. After a week, the brackets were debonded using a pair of bracket-removing pliers assembled to a testing machine. Optical stereomicroscope and trans-illumination techniques were used to calculate the cracks and measure their length before bonding and after debonding. Paired t-test, independent t-test and McNemar's test were used for statistical analysis. Results: Metallic brackets showed higher mechanical bond strength compared to ceramic brackets with mechanical locks. In both groups, higher numbers of teeth with enamel cracks and a significant increase in the length of enamel cracks were evident subsequent to debonding. Inter-group deference in the number of teeth with cracks and the length of enamel cracks before or after debonding was not significant. Conclusions:The risk of producing enamel cracks after debonding of ceramic brackets with mechanical retention is the same as metallic brackets

Bolton's intermaxillary tooth size ratios among Iranian schoolchildren

Objectives: The aims of the present study were to determine anterior and total tooth-width ratios in a representative Iranian sample in Tabriz city and compare them with the Bolton standards. Study design: A total of 54 Iranian schoolchildren (12-14 years old) in Tabriz were examined. Alginate impressions were taken for subjects and poured by the dental stone. The mesiodistal widths of the teeth were measured using a digital caliper. The overall and anterior Bolton's intermaxillary tooth size ratios for each model pair was calculated. Results: There were no significant differences (p > 0.05) between the right and left sides of the dental arch and a symmetry in size exists. There were no significant differences between genders for all teeth measured except for the maxillary central incisors, maxillary canines and mandibular canines. Anterior and overall Bolton ratios for males were 77.72±0.25 and 92.44±0.19 and for females were 78.48±0.30 and 92.45±0.23 percent, respectively. There were no statistically significant differences between males and females for the anterior and overall ratios. The anterior and overall Bolton ratios among Tabrizian schoolchildren were 78.10±0.28 and 92.24±0.21 percent, respectively. There was no statistically significant difference between these ratios and those were found in the Bolton study. Conclusion: No significant differences between the mesiodistal sizes of contralateral teeth were observed and a symmetry in size exists. There were no significant differences in the mesiodistal sizes of similar teeth between males and females except for the maxillary central incisors, maxillary canines and mandibular canines. Significant differences in Bolton ratio between males and females, and examined population (student from Tabriz, Iran) and the Bolton's weren't observed either. © Medicina Oral S. L

Effect of surface treatment with sandblasting and Er,Cr:YSGG laser on bonding of stainless steel orthodontic brackets to silver amalgam

Objectives: Satisfactory bonding of orthodontic attachments to amalgam is a challenge for orthodontists. The aim of this in vitro study was to compare the shear bond strength of stainless steel orthodontic brackets to silver amalgam treated with sandblasting and Er,Cr:YSGG laser. Study Design: Fifty-four amalgam discs were prepared, polished and divided into three groups: In group 1 (the control group) the premolar brackets were bonded using Panavia F resin cement without any surface treatment; in groups 2 and 3, the specimens were subjected to sandblasting and Er,Cr:YSGG laser respectively, before bracket bonding. After immersing in distilled water at 37°C for 24 hours, all the specimens were tested for shear bond strength. Bond failure sites were evaluated under a stereomicroscope. Data was analyzed using one-way ANOVA and a post hoc Tukey test. Results: The highest and lowest shear bond strength values were recorded in the laser and control groups, respectively. There were significant differences in mean shear bond strength values between the laser and the other two groups (p<0.05). However, there were no significant differences between the sandblast and control groups (p=0.5). Conclusions: Amalgam surface treatment with Er,Cr:YSGG laser increased shear bond strength of stainless steel orthodontic brackets. © Medicina Oral

Arch width changes in patients with Class II division 1 malocclusion treated with maxillary first premolar extraction and non-extraction method

Background: The aim of this study was to determine arch width changes during maxillary first premolars extraction and non-extraction treatment in patients with Class II division 1 malocclusion. Material and Methods: Dental casts of 91 Class II division 1 patients (36 males and 55 females) were evaluated. The minimum age of the subjects at the beginning of treatment was above 16 years. 48 patients were treated with extraction of the maxillary first premolars and 43 patients were treated without extraction. Pre- and post-treatment maxillary and mandibular inter-canine and inter-molar arch widths were measured. Results: At the end of treatment, maxillary and mandibular inter-canine widths of both groups increased significantly. The maxillary inter-molar width decreased in the extraction group and increased in the non-extraction group. The mandibular inter-molar width increased significantly in both groups. No significant differences were observed between males and females. Conclusions: The results of this study indicated that there was a tendency for an increase in arch width during both the extraction and non-extraction treatment except maxillary inter-molar width in the extraction cases

Analysis of KRT5 and KRT14 gene mutations and mode of inheritance in Iranian patients with clinical suspicion of Epidermolysis bullosa simplex

Background: Epidermolysis bullosa simplex is a hereditary skin disorder caused by mutations in several genes such as KRT5 and KRT14. Skin fragility in basal keratinocytes presence regions led to the cytolysis of epidermis and blistering. Aim of this study was to detect the molecular defects in KRT5 and KRT14 genes hot spots in patients with clinical suspicion of EBS and investigation of their probable genotype-phenotype correlations. Methods: Exons 1 and 6-7 of KRT5 and exons 1 and 4-7 of KRT14 amplification and mutation detection were performed by polymerase chain reaction and Sanger sequencing, respectively. Novel variants pathogenicity evaluated by bioinformatics tools. Results: Nine important variants detected in seven different patients within 6 Iranian families affected by Epidermolysis bullosa simplex, of which four variants were novel. Three patients had a mottled pigmentation phenotype G96D (p. Gly96Asp) and F97I (p. Phe97Ile) in KRT5. One of them showed a Dowling-Meara phenotype A417P (p. Ala417Pro) and E477D (p. Glu477Asp) in KRT5 and another had a Koebner type phenotype R397I (p. Arg397Ile) and Q444* (p. Gln444Ter) in KRT5. A novel variant G92E (p. Gly92Glu) in KRT5 in a double heterozygous state with a challenging variant A413T (p. Ala413Thr) in KRT14 identified in one patient with Koebner type phenotype. Also, a previously reported mutation I377T (p. Ile377Thr) in KRT14 gene identified in this study. Conclusion: The results of molecular data analysis showed that the most severe phenotypes were associated with mutations in highly conserved regions. In some cases, different inheritance modes were observed. © Iran University of Medical Sciences

Calcium Homeostasis and Cone Signaling Are Regulated by Interactions between Calcium Stores and Plasma Membrane Ion Channels

Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca2+ entry (SOCE) to Ca2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca2+ channels. Exposure to MRS 1845 resulted in ∼40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse

Comparison of the Effects of Traditional with Combined (Traditional and Electronic) Educational Methods on Promoting the Practical Skill of Fabricating the Removable Orthodontic Appliance

Introduction: Computer aided education can compensate for some deficiencies and limitations of traditional education. The aim of this study was to evaluate the effect of e-learning, as an adjunctive method of traditional education, in the form of video clips and PowerPoint presentations on the skills of fabricating the wire components of removable orthodontic appliance in the preclinical course of dental students. Methods: This prospective quasi-experimental study was performed on 40 eighth semester dental students who were taking the course practical orthodontics 1 in Tabriz School of Dentistry in 2012-13 academic year. Participants were selected through convenience sampling and randomly divided into two groups. The control group received traditional trainings including practical training of fabricating the wire components of removable orthodontic appliance, and the experimental group received the same plus e-learning. The skills in fabricating three major components of removable orthodontic appliance namely Z spring, Adams clasp and labial bow were evaluated using a 21-item checklist. Data were analyzed by means of independent and paired t-tests. Results: The mean scores of the control and the experimental groups were 14.2±1.4 and 15.5±1.8 (out of 20) respectively and their difference was statistically significant (P=0.026, t=2.31). The mean score of labial bow fabrication was higher in the experimental group than that of the control group (p=0.01, t=2.72). However, the mean scores of Z spring and Adams clasp fabrication were not significantly different in the two groups. Conclusion: Using E-learning as an adjunctive method of traditional education can improve the practical skills of fabricating the wire components of removable orthodontic appliances