An investigation of the corrosion behavior of zinc-coated stainless steel orthodontic wires: the effect of physical vapor deposition method.

BACKGROUND: Releasing of metal ions might implicate in allergic reaction as a negative subsequent of the corrosion of Stainless Steel (SS304) orthodontic wires. The aim of this study was to evaluate the corrosion resistance of zinc-coated (Zn-coated) SS orthodontic wires. METHODS: Zinc coating was applied on SS wires by PVD method. Electrochemical impedance spectroscopy (EIS), Potentiodynamic polarization tests and Tafel analysis methods were used to predict the corrosion behavior of Zn-coated and uncoated SS wires in both neutral and acidic environments. RESULTS: The values of Ecorr ,icorr and Rct ,which were the electrochemical corrosion characteristics, reported better corrosion behavior of Zn-coated SS wires against uncoated ones in both artificial saliva and fluoride-containing environments. Experimental results of the Tafel plot analyses were consistent with that of electrochemical impedance spectroscopy analyses for both biological solutions. CONCLUSION: Applying Zn coating on bare SS orthodontic wire by PVD method might increase the corrosion resistance of the underlying stainless-steel substrate.

Three-dimensional evaluation of the cortical and cancellous bone density and thickness for miniscrew insertion: a CBCT study of interradicular area of adults with different facial growth pattern.

AIM: The purpose of this study was to evaluate the effect of the density and the thickness of the cortical and the cancellous bone at selected inter-radicular areas in subjects with different facial growth patterns using cone beam computed tomography (CBCT) in order to choose the optimal area for miniscrew insertion. MATERIALS AND METHODS: From 150 CBCT scans, 45 scans were included in the study. The subjects were categorized into three groups based on their skeletal growth pattern according to SN-GoMe angle and facial height index. Cortical and cancellous bone density and thickness were measured at the selected inter-radicular areas. RESULTS: Compared to the other two groups, the hyperdivergent group had thinner cortical bone in the anterior region of the maxilla between the central and the lateral incisors on the buccal side at 4 mm from the alveolar crest (P-value: 0.012) and on the palatal side at 7 mm from the alveolar crest (P-value: 0.030). Cancellous bone density values in these areas were higher in subjects with hypodivergent and hyperdivergent growth pattern. Furthermore, in hyperdivergent group less dense cortical bone in the posterior region of the maxilla on the palatal side between the second premolar and the first molar (p-value: 0.020) and on the buccal side between the first molar and the second molar (p-value: 0.038 & 0.047) was observed. No significant differences were found in the mandible between the three groups. No significant differences were found between the male and the female subjects. CONCLUSION: Hyperdivegents presented thinner cortical bone in the anterior of the maxilla between the central and the lateral incisors. Less dense cortical bone was found between maxillary second premolar and first molar on the palatal side and also between the maxillary first molar and the second molar on the buccal side in this group too. Normal showed higher density values in the posterior of the maxilla compared to the other two groups. No significant differences were found among three groups in mandible.

Comparing the effects of Elaegnus Angustifolia, Hypericum Perforatum and Psidium Guajava extracts on metabolic activity of dental pulp-derived mesenchymal stem cells.

Dental pulp derived-mesenchymal stem cells (DP-MSCs) is considered a suitable are candidate for tissue engineering techniques and osseous reconstruction. Based on the hypothesis that Hypericum perforatum, Elaeagnus Angustifolia and Psidium guajava extracts can be used in cell-based bone tissue engineering due to meagre cytotoxicity response in the cell culture medium, their effects on the viability and metabolic activity of DP-MSCs were investigated and compared with each extract. DP-MSCs were extracted from human dental pulp, characterized by flow cytometry, and differentiated into Osteogenic and adipogenic lineages which were then cultured in different concentrations of E. Angustifolia, H. perforatum and P. guajava extracts at different time intervals followed by MTT assay evaluation. The dental pulp mesenchymal stem cells were evaluated for their plastic adherence ability, fibroblast-like and spindle morphology. According to flow cytometry data, isolated cells from DP-MSCs expressed MSCs markers. A comparison of herbal extracts' concentrations revealed that 500 µg/ml was toxic to dental pulp stem cells, a guide to the toxic dose for DP-MSCs. The P.guajava bore low toxicity and increased dental pulp stem cell viability in comparison to the other two herbal extracts. The hydro-alcoholic extracts of E. Angustifolia, H. perforatum, and P. guajava were efficient in DP-MSCs viability, and therefore were concluded to be useful in maintaining structural and functional cell viability. It was also concluded that the co-culture of stem cells with herbal elements could stimulate endogenous factors to enhance the proliferation and viability of MSCs.

Comparison of Glenoid Fossa Morphology Between Different Sagittal Skeletal Pattern Using Cone Beam Computed Tomography.

Morphology of glenoid fossa might help the clinician in the diagnosis, establishing more biological treatment modalities and treatment response between patients with different skeletal malocclusions. This study aimed to assess the glenoid fossa morphology in different sagittal facial types using CBCT. The CBCT images of 64 patients with normal vertical growth patterns were classified into class I, class II, and class III based on the skeletal sagittal analysis. Depth, width, and angle of glenoid fossa were measured and assessed on CBCT images. One-way analysis of variance (ANOVA) and Tukey post-hoc test were used to compare mean values among the groups. There was a significant statistical difference in means of glenoid fossa' width between groups with skeletal class III and skeletal class I (P value: 0.038). However, no significant statistical differences were found in angle(P value = 0.18) and depth (P value = 0.40) of glenoid fossa among 3 groups. This study showed the glenoid fossa in class I patients was wider than class III patients. There were no statistically significant differences in the angle and depth of glenoid fossa in patients with a different sagittal skeletal pattern.

Dental students in an orthodontic course flipped classroom: A semi-experimental study on knowledge, practice, attitude, and satisfaction.

OBJECTIVE: The purpose of this study was to determine the students' attitudes before and after the flipped classroom, and the effectiveness of this method to promote the students' lateral cephalograms tracing abilities, students' satisfaction and their final exam scores. MATERIALS AND METHODS: This is a single-group quasi-experimental research conducted on dental students of Shiraz University of Medical Sciences (SUMS), Iran in 2019. The intervention was carried out in a blended learning approach with the flipped classroom model. Thirty-five fourth-year dental students participated in a flipped classroom held during a semester for the lateral cephalograms tracing course. The students were provided with the educational materials before the class time through multimedia learning tools and the class time was devoted to discussions. The students were asked to fill out four questionnaires (pretest/posttest attitudes, pretest/posttest self-assessments of theoretical knowledge and practical skills in cephalograms, posttest of satisfaction from quality of the course, and posttest of students' views about effectiveness of blended learning tools) and final exam scores of students. RESULTS: Students' attitudes toward e-Learning were improved after the flipped classroom and the quality of this method was acceptable to the students (p < .001). Their self-assessment of theoretical knowledge and practical skills were promoted (p < .001). While all blended learning tools averaged more than the cut-off-point, short lecture (5.11 ± 0.98) and live feedback (4.98 ± 1.07) were considered to be the most efficient interactive tools. CONCLUSION: It seems that the flipped classroom has a positive effect on increasing students' knowledge, attitude, and satisfaction. In general, this method of learning seems to be favored by dental students. CLINICAL SIGNIFICANCE: The findings showed that blended learning had a positive effect on increasing knowledge, performance, and satisfaction among dental students. Therefore, blended learning as a reliable method might be used in training dental students.

Characteristics of Medial Depression of the Mandibular Ramus: A CBCT Analysis in Different Sagittal Skeletal Patterns.

Statement of the Problem: Medial depression of the mandibular ramus (MDMR) as a normal anatomical variation might complicate orthognatic surgeries that involve ramus. When planning an orthognatic surgery, it is clinically valuable to notice MDMR in osteotomy site to decrease the risk of failure. Purpose: The aim of present study was to evaluate the prevalence as well as characteristics of MDMR in three skeletal sagittal classifications. Materials and Method: This cross sectional study evaluated 530 cone beam computed tomography (CBCT) scans, of which 220 were enrolled. The skeletal sagittal classification, the presence of MDMR, the shape, depth, and width of MDMR were recorded for each patient by two examiners. Chi-square test was performed to determine the differences between three skeletal sagittal groups and between two genders. Results: The overall prevalence of MDMR was 60.45%. MDMR was mostly detected in class III (76.92%), followed by class II (76.66%), and class I (54.87%). In the analyzed CBCT scans, semi-lunar was the most common shape detected (42.85%), followed by triangular (30.82%), circular (18.04%), and tear-drop (8.27%). The depth of MDMR was not significantly different between three sagittal groups and between genders; however, the width of MDMR was higher in class III group and in male patients. In the present study, MDMR was found to be more common in patients with class II and class III skeletal classifications. Although, MDMR was more frequent in class III, the difference between class II and class III was not significant. Conclusion: More caution is needed during orthognatic surgery in patients with dentoskeletal deformities during the splitting of the ramus. Moreover, higher width of MDMR in class III and male patients should be concerned when planning an orthognatic surgery for these patients.

Design of a Knowledge Evaluation Questionnaire for Dental Specialists on Preservation and Extraction Indications of the First Permanent Molars.

Statement of the Problem: The first permanent molar (FPM) teeth are the most important elements of mastication and are crucial in the improvement of functionally proper occlusion. However, in childhood, these teeth are most susceptible to caries. The loss of an FPM in a child can cause changes in the dental arches. These changes can occur throughout a person's life. In such cases, the dentists and dental specialists need to decide whether to preserve or extract the FPM. Purpose: This study aimed to evaluate the extent of knowledge of dental specialists in Shiraz (Iran) on clinical guidelines for the preservation and extraction indications of FPMs. Materials and Method: The authors developed a dedicated questionnaire for the purpose of knowledge evaluation. A total of 6 orthodontists and 15 dental specialists, respectively confirmed the validity and reliability of the questionnaire. The 19-item questionnaire covered topics such as demographic data, preservation criteria for FPM teeth, and indications for FPM extraction. The survey was carried out across six dental disciplines in Shiraz (Iran) during July-August 2018. The data were analyzed using the SPSS software (version 22.0) with the dependent sample t test and one-way ANOVA. p Value< 0.05 was considered statistically significant. Results: Out of 89 dental specialists, 64 participants (53% male, 47% female) completed the questionnaire. The mean knowledge score for all participants was 10.09±3.93 (maximum of 19). The level of knowledge had a significant and inverse correlation with age (p< 0.001) and years of experience (p= 0.017). It also had a significant relationship with dental specialization (p< 0.001). Conclusion: The overall level of knowledge of the specialists was insufficient, except for the pedodontists and orthodontists. A re-education training program for dental specialists is strongly recommended.

Evaluating the Mechanical Properties of Zinc-Coated Stainless Steel Orthodontic Wires Using Physical Vapor Deposition.

The aim of this study was to evaluate the mechanical properties of stainless steel (SS) orthodontic wires coated with zinc (Zn), using a Physical Vapored Deposition (PVD) machine. A total of 100 straight SS orthodontic wires were cut into pieces of 5 centimeters in length and were divided into two groups. Half of the wires were coated with Zn using a PVD machine, and the others remained uncoated. Tensile strength (n = 15), three-point bending (n = 15), and frictional resistance at 0° (n = 10) and 10° (n = 10) were measured to compare the mechanical properties of the Zn-coated and uncoated orthodontic wires using the universal testing machine. The surface of the coated wires was observed by SEM and AFM. An independent t-test, multivariate ANOVA, and measurement ANOVA were used for data analysis. SEM and AFM showed a homogenous Zn layer of 0.28 ± 0.006 µm on the SS wires. The tensile strength and three-point bending strength significantly increased after Zn coating of wires with the PVD method (P < 0.05). The friction resistance significantly reduced at both angulations following the coating procedure. The angle between the wire and bracket had no significant effect on the frictional resistance (P > 0.05). Coating with Zn improved the tensile and load-bending strength of SS orthodontic wires and reduced their frictional resistance which might be advantageous in terms of reducing the risk of root resorption during the orthodontic treatment.

Comparison of individual and team readiness assurance tests in a modified team based learning method.

OBJECTIVE: Team based learning (TBL) is shown to have a positive impact on learning abilities. In this study, we compared the individual and group readiness assurance grades of dental students toward a modified TBL protocol for an orthodontic topic. METHODS: All of the dentistry students in 2 different annual intakes from Shiraz University of Medical Sciences took part in the study. The references and methods for holding the class was presented to the vice dean of educational affairs and to the students. At the beginning of the session, individual readiness assurance test (iRAT) was held. Then, the students were asked to arrange in 15-member groups for a modified TBL exercise. Each group took part in the team readiness assessment test (tRAT) and draw concept maps of 5 major topics. Then, they presented their team work, discussed them, and concluded. At the end of the session, the students reported their attitude on the pre-constructed assay form. The data were analyzed with SPSS software 17, using paired T test and Wilcoxon signed rank test. RESULTS: We observed statistically significant improvement in the tRAT score compared with iRAT in the male and female participants (P-value <0.001). More than 60% of the participants felt that TBL enhanced the overall satisfaction and pleasure from participation in class. CONCLUSIONS: Based on our study, team work depicted significant improvement in the students' scores of an orthodontic topic. According to students, satisfaction with TBL was favorable and improved with additional experience.

Computerized Analysis of Digital Photographs for Evaluation of Tooth Movement.

OBJECTIVES: Various methods have been introduced for evaluation of tooth movement in orthodontics. The challenge is to adopt the most accurate and most beneficial method for patients. This study was designed to introduce analysis of digital photographs with AutoCAD software as a method to evaluate tooth movement and assess the reliability of this method. MATERIALS AND METHODS: Eighteen patients were evaluated in this study. Three intraoral digital images from the buccal view were captured from each patient in half an hour interval. All the photos were sent to AutoCAD software 2011, calibrated and the distance between canine and molar hooks were measured. The data was analyzed using intraclass correlation coefficient. RESULTS: Photographs were found to have high reliability coefficient (P > 0.05). CONCLUSION: The introduced method is an accurate, efficient and reliable method for evaluation of tooth movement.

The efficiency of laser application on the enamel surface: a systematic review.

Used in conjunction with or as a replacement for traditional methods, it is expected that specific laser technologies will become an essential component of contemporary dental practice over the next decade. The current review is designed to focus on the acid resistance of laser application and tries to introduce laser settings capable to achieve this feature for clinical application. Application of laser for its acid resistance might be a valuable adjunct to conventional acid etching for susceptible sites in high caries risk patients such as patients with rampant caries, who cannot follow oral hygiene instructions due to their systematic disabilities, or those under orthodontic treatment with plaque retentive attachment on their teeth. The key words "enamel acid resistance" and "laser" were searched in PubMed. In brief, the current paper involves the results on 5 items: A summary on laser application; Suggested mechanisms of acid resistance; Different types of laser beams used in acid resistance; Comparison of application of different laser types; and Conclusion.

In vitro evaluation of microleakage around orthodontic brackets using laser etching and Acid etching methods.

OBJECTIVE: path of microleakage between the enamel and adhesive potentially allows microbial ingress that may consequently cause enamel decalcification. The aim of this study was to compare microleakage of brackets bonded either by laser or acid etching techniques. MATERIALS AND METHOD: The specimens were 33 extracted premolars that were divided into three groups as the acid etching group (group 1), laser etching with Er:YAG at 100 mJ and 15 Hz for 15s (group 2), and laser etching with Er:YAG at 140 mJ and 15 Hz for 15s (group 3). After photo polymerization, the teeth were subjected to 500 thermal cycles. Then the specimens were sealed with nail varnish, stained with 2% methylen blue for 24hs, sectioned, and examined under a stereomicroscope. They were scored for marginal microleakage that occurred between the adhesive-enamel and bracket-adhesive interfaces from the occlusal and gingival margins. Data were analyzed with the Kruskal- Wallis test. RESULTS: For the adhesive-enamel and bracket-adhesive surfaces, significant differences were not observed between the three groups. CONCLUSION: According to this study, the Er:YAG laser with 1.5 and 2.1 watt settings may be used as an adjunctive for preparing the surface for orthodontic bracket bonding.