In Vitro Effect of Photobiomodulation Therapy with 980 nm Diode Laser on Gene Expression of Key Regulators of Bone Remodeling by Human Periodontal Ligament Cells under Mild Orthodontic Forces.

This study investigated the effect of photobiomodulation (PBM) with 980 nm diode laser as monotherapy and in combination with compressive and tensile orthodontic forces on expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL), sclerostin (SOST) and periostin (POSTN), by human periodontal ligament cells. Isolated cells were cultured and subjected to either tensile (10% elongation) or compressive forces (25 g cm-2 ) for 24 and 48 h. Subsequently, the cells received PBM (100 mW power, 3 or 6 J cm-2 energy density) immediately after load cycle. RT-PCR was applied to assess the genes expression. Data were analyzed by one-way ANOVA, followed by post hoc Tukey test (P ≤ 0.05). We found that PBM in combination with orthodontic forces led to upregulation of bone resorption genes (RANKL and SOST) at the pressure side and their downregulation at the tension side. The expression of osteogenic genes (OPG and POSTN) increased at the tension side and decreased at the pressure side. PBM alone did not affect gene expression. In conclusion, these findings suggest that this PBM protocol may be effective in enhancement of the gene expression in favor of bone remodeling acceleration that should be confirmed in future animal and human studies.

Comparative assessment of the orthodontic wire's friction coated with zinc oxide nanoparticles by two methods of chemical precipitation and hydrothermal process.

INTRODUCTION: In orthodontic treatment with sliding technique, reduction of frictional forces could result in a more effective treatment. Recently, wire coating with nanoparticles were proposed to reduce frictional forces.

Evaluation of the Shear Bond Strength and Adhesive Remnant Index in Debonding of Stainless Steel Brackets Assisted with Nd:YAG Laser Irradiation.

OBJECTIVES: The purpose was to compare shear bond strength (SBS), pulp temperature, and adhesive remnant index (ARI) in debonding of stainless steel brackets from enamel surface using neodymium-doped yttrium aluminum garnet (Nd:YAG) laser versus the conventional debonding method. MATERIALS AND METHODS: Forty-eight extracted premolars were bonded to stainless steel brackets. The samples were divided into three experimental groups and one control group. In the first three groups, Nd:YAG laser was used for debonding with the power of 1, 1.5, and 2 W, respectively, for 10 seconds. The SBS and ARI of the samples were assessed. Pulp temperature was recorded before and after irradiation. Two samples from each group were used for determining enamel morphology after debonding using scanning electron microscopy (SEM). RESULTS: The mean SBS in the groups was 33.05, 28.69, 24.37, and 31.53 MPa, respectively, with no statistically significant differences (P=0.205). Significant differences in post-irradiation temperature were noted among the lased groups (P=0.000). Debonding mainly occurred at the adhesive-enamel interface in the 1-W laser and control groups and at the bracket-adhesive interface in the 1.5-W and 2-W laser groups. Enamel structure was amorphous and irregular following laser irradiation. CONCLUSION: Based on the results of this study, the use of Nd:YAG laser could not significantly affect the SBS. Therefore, this laser would not be suitable for debonding of metal brackets. The use of a 2-W laser could significantly raise the pulpal temperature. Nd:YAG laser renders a more heterogeneous enamel morphology compared to conventional debonding methods.

Decreased bone density induced by antiepileptic drugs can cause accelerated orthodontic tooth movement in male Wistar rats.

PURPOSE: The aim of the present study was to evaluate the effect of the carbamazepine and valproic acid on orthodontic tooth movement in male Wistar rats. METHODS: Evaluation of tooth movement after 21 days of drugs infusion was carried out by feeler gauge. Bone densitometry on lateral cephalograms was conducted on days 1 and 21. After dissection of the maxillae, histologic parameters were evaluated. RESULTS: Orthodontic tooth movement was accelerated in experimental groups rather than controls. Optical density was significantly increased in these groups. In histologic sections, mesioapical portion of the PDL (Periodontal Ligament) was wider in experimental groups. Also, distoapical portion of the PDL was wider only in valproic acid group. CONCLUSION: Valproic acid and carbamazepine can decrease the bone density which may induce the accelerated orthodontic tooth movement in rats.

Effect of Cyclic Loading on Shear Bond Strength of Orthodontic Brackets: An In Vitro Study.

OBJECTIVES: In clinical conditions, orthodontic brackets are exposed to periodic stresses mainly induced by mastication and intraoral forces. The objective of the present study was to evaluate the effects of cyclic loading to simulate masticatory forces on shear bond strength (SBS) of metal brackets bonded to teeth using self-etch and total-etch bonding systems. MATERIALS AND METHODS: Eighty-four caries- and crack-free bovine mandibular incisors were selected and randomly assigned to two groups based on the type of bonding system. After bonding, all samples were thermocycled (500 cycles) followed by cyclic loading of the half of the specimens in each group by applying 40 N load with 2 Hz frequency for 10,000 cycles. The SBS was measured using a universal testing machine. The adhesive remnant index (ARI) score was calculated subsequently. Data were analyzed using Kolmogorov-Smirnov test, two-way ANOVA and Mann-Whitney test. RESULTS: The SBS was 10.09±3.78 MPa and 14.44±6.06 MPa for self-etch and total-etch bonding systems in cyclic loading group, respectively. The SBS was 9.43±5.3 MPa and 11.31±5.42 MPa in self-etch and total-etch groups without cyclic loading, respectively. Cyclic loading did not cause any significant difference in SBS (P>0.05). The ARI scores of the groups were significantly different (P<0.05). CONCLUSIONS: The present results demonstrated that low masticatory forces at 10,000 cycles did not have a significant impact on bracket-adhesive SBS; however, they significantly changed the ARI score. Even though the total-etch bonding system yielded higher SBS than the self-etch system, the performance of both was clinically acceptable.

Comparison of Enamel Morphologic Characteristics after Conditioning with Various Combinations of Acid Etchant and Er:YAG Laser in Bonding and Rebonding Procedures: A SEM Analysis.

OBJECTIVES: Many studies have evaluated re-etched enamel by using scanning electron microscopy (SEM); however, there is no evidence regarding the use of Erbium-doped yttrium aluminium garnet (Er:YAG) laser at primary and secondary bonding instead of acid etching with regards to enamel surface changes. The purpose of the present study was to determine that whether or not the methods of primary and secondary enamel preparation affect enamel characteristics after rebonding, by using SEM analysis. MATERIALS AND METHODS: Twelve freshly extracted premolars were divided into 4 groups. The samples in each group were conditioned by acid etchant or Er:YAG laser at primary conditioning, according to the instructions. Afterwards, they were bonded with orthodontic brackets. After debonding, the samples were prepared for second conditioning. Also, two samples were conditioned only once with acid etchant or laser, to compare enamel morphology changes with those after re-etching. Finally, buccal enamel surfaces were evaluated using SEM. RESULTS: Enamel etching patterns were observed in the samples which had been acid-conditioned at first or at both conditionings. The samples irradiated by Er:YAG laser showed amorphous and irregular surfaces, with no signs of typical etching patterns. A large deep gap was seen in one of the samples irradiated with laser at primary and secondary conditionings, which might have penetrated the underling layers of enamel and dentin. CONCLUSIONS: Enamel surface preparation with Er:YAG laser produces irregular and indistinct morphologic changes, completely different from those produced after acid etching at both conditioning and reconditioning. Therefore, it is recommended to use this laser with caution to avoid permanent enamel damage.

Effect of supplementary zinc on orthodontic tooth movement in a rat model.

INTRODUCTION: Osteoclasts and osteoblasts are responsible for regulating bone homeostasis during which the trace element zinc has been shown to exert a cumulative effect on bone mass by stimulating osteoblastic bone formation and inhibiting osteoclastic bone resorption. OBJECTIVE: The aim of the present study was to investigate the effects of zinc (Zn) on orthodontic tooth movement (OTM) in a rat model. MATERIAL AND METHODS: A total of 44 male Wistar rats were divided into four groups of 11 animals each and received 0, 1.5, 20 and 50 ppm Zn in distilled water for 60 days. In the last 21 days of the study, nickel-titanium closed coil springs were ligated between maxillary right incisors and first molars of all rats, and tooth movement was measured at the end of this period. Histological analysis of hematoxylin/eosin slides was performed to assess root resorption lacunae, osteoclast number and periodontal ligament (PDL) width. RESULTS: Mean OTM was calculated as 51.8, 49.1, 35.5 and 45 µm in the 0, 1.5, 20 and 50 ppm zinc-receiving groups, respectively. There were no significant differences in neither OTM nor histological parameters among the study groups (p > 0.05). CONCLUSION: According to the results obtained in the current investigation, increase in supplementary zinc up to 50 ppm does not affect the rate of OTM neither bone and root resorption in rats.

PubMed-Indexed Dental Publications from Iran: A Scientometric Study.

OBJECTIVES: Scientometric methods and the resulting citations have been applied to investigate the scientific performance of a nation. The present study was designed to collect the statistical information of dental articles by Iranian authors published in PubMed. MATERIALS AND METHODS: We searched the PubMed database for dental articles of Iranian authors until June 31, 2015. All abstracts were manually reviewed in order to exclude false retrievals. The number of articles per dental subspecialties, distribution of research designs, Scopus/Google Scholar citation of each article, number of authors and affiliation of the first/corresponding author were extracted and transferred to Microsoft Excel. The data were further analyzed to illustrate the related scientometric indicators. RESULTS: A total of 3,835 articles were retrieved according to the selection criteria. The number of PubMed-indexed publications between 2008 and 2015 showed a seven-fold increase. The majority of articles were written by four authors (24.56%). Systematic reviews and clinical trials constituted 9.20% of all publications. The number and percentage of articles with ≥4 citations from Google Scholar (n=2024; 52.78%) were higher than those from Scopus (n=1015; 26.47%). According to affiliated departments of the first authors, the top three dental subspecialties with the highest number of publications belonged to endodontics (19.82%), orthodontics (11.13%) and oral and maxillofacial surgery (10.33%). Moreover, the majority of articles originated from Shahid Beheshti- (14.47%), Tehran- (13.72%) and Mashhad- (12.28%) University of Medical Sciences. CONCLUSIONS: Analysis of PubMed-indexed dental publications originating from Iran revealed a growing trend in the recent years.

Assessment of the Role of NO-cGMP Pathway in Orthodontic Tooth Movement Using PDE5 Inhibitors: An Animal Study.

OBJECTIVES: Nitric oxide (NO) is a signaling molecule that mediates mechanical bone loading. Cyclic guanosine 3', 5' monophosphate (cGMP) is a NO-induced effector molecule. The aim of this study was to assess the effect of NO-cGMP pathway on orthodontic tooth movement (OTM) in rats by use of two phosphodiesterase 5 (PDE5) inhibitors namely sildenafil and tadalafil as chemical tools. MATERIALS AND METHODS: Forty-five male Wistar rats were divided into three equal groups (n=15) based on the substance they received. The first group received daily injections of tadalafil; the second group received daily injections of sildenafil and the third group received daily injections of normal saline. The orthodontic appliances consisted of nickel-titanium closed-coil spring ligated between the maxillary right incisor and the first molar of the animals for 21 days. The amount of tooth movement was measured in all three groups at the end of this period. Histological analysis was performed to assess root resorption lacunae, osteoclast number and periodontal ligament (PDL) thickness. RESULTS: All appliance-treated molars in the experimental and control groups showed evidence of tooth movement. The mean OTM was calculated to be 0.39±0.16, 0.32±0.16 and 0.26±0.16mm in tadalafil, sildenafil and control groups, respectively and there were no significant differences in OTM among the study groups (P>0.05). In the tadalafil group, significantly greater root resorption on the tension side was seen when compared with controls (P≤0.05). CONCLUSIONS: Tadalafil and sildenafil PDE-5 inhibitors affecting the NO-cGMP pathway did not affect OTM in rats.

Orthodontic research output from iran in international and national journals.

OBJECTIVE: The number of scientific papers is a conventional metric to measure a country's research performance in a particular area. The aim of this survey was to demonstrate statistical information about orthodontic research published in international and national journals. MATERIALS AND METHODS: Pubmed as an international and IranMedex and SID as national databases were searched between1997 and 2012. The keyword searching method was used in English and Persian. Abstracts were reviewed and unrelated articles were omitted. Data were obtained and transferred to Microsoft Excel to survey the scintometric indicators. RESULTS: According to the defined criteria, a total of 733 papers were found showing a considerable increase. Five hundred papers (68.2%) were published in domestic journals, and 233 (31.8%) were published in PubMed indexed journals. Most of the orthodontic articles originated from Shahid Beheshti University of Medical Sciences (22.9%). The Journal of Dental School, Shahid Beheshti University of Medical Sciences published most of the national papers (27.8%) and the Australian Orthodontic Journal published the majority of international papers (9.9%) In terms of study design, 52.5% of the articles were observational and 39.4% were interventional. CONCLUSION: Orthodontic research production in Iran has made significant strides in the recent years and researchers should focus on the quality of the study in this field in order to apply research production in evidence base dentistry.

Designing Orthodontic Craniofacial Templates for 8-14 year-old Iranian Girls Based on Cephalometric Norms.

OBJECTIVES: Cephalometry and its related analyses have an important role in the evaluation of orthodontic patients. Access to an analysis that gives maximum information in the least possible time is an effective way to indicate craniofacial disharmony; therefore, craniofacial templates are very useful tools. The purpose of the present study was to provide orthodontic craniofacial templates for 8-14-year-old Iranian girls. MATERIALS AND METHODS: One thousand two-hundred and nine girls (age range, 8-14 years) were examined. Eighty of these cases were finally chosen for the study and their lateral cephalograms were traced. Both Basion-Nasion (Ba-N) and Sella-Nasion (S-N) lines were selected for superimposition in this study. Based on these two mentioned lines, a template for each age was designed. Simple linear regression and multivariant regression analysis were used to evaluate the angles and to landmark the vectors, respectively. RESULTS: Findings show that most points change significantly at different ages in the S-N method. In the Ba-N method, all points except for S and Ba have significant changes at different ages. CONCLUSION: Templates that resulted from both methods were the same and alteration in the reference line and points does not change the total form of the average tracings of each age.

Comparison of desensitizing efficacy of an Iranian dentifrice and a commercially available dentifrice: a randomized double-blinded controlled clinical trial.

OBJECTIVE: The aim of this randomized controlled clinical trial was to investigate the effect of a new Iranian toothpaste and a commercially available toothpaste containing desensitizing agent (5% potassium nitrate) on dentine hypersensitivity in a 24-week study. MATERIALS AND METHODS: Fifty healthy volunteers, who had at least two sensitive root surfaces, completed the study period. The participants were randomly given one of the two toothpastes; Iranian (antihypersensitive Pooneh) or commercially available (fresh mint Sensodyne) toothpaste. Visual analogue scales (VASs) indicating the intensity of tooth hypersensitivity responding to tactile, airblast and cold-water stimuli were examined at baseline and weeks 2, 4, 12 and 24. RESULTS: Overall, VAS scores for tactile, airblast, and cold-water tests significantly reduced compared with the baseline in both groups (all P values <0.001). However, there was no significant difference between the two groups regarding the measured parameters. CONCLUSION: This study demonstrated that the Iranian dentifrice (antihypersensitive Pooneh) was as effective as the commercially available one (fresh mint Sensodyne) in reducing tooth hypersensitivity.

Effect of atorvastatin on orthodontic tooth movement in male wistar rats.

OBJECTIVES: Statins are used as cholesterol-lowering drugs by many patients and have been recently shown to affect bone metabolism. The aim of this study was to determine the effect of atorvastatinon on orthodontic tooth movement (OTM) in rats. MATERIALS AND METHODS: Thirty-six adult male Sprague-Dawley rats were randomly divided into three groups of 12 samples each. Group A, served as control with no medication while groups B and C received a daily gavage of carboxymethyl cellulose (CMC) as vehicle and atorvastatin (5 mg/kg) as test substance, respectively. In all three groups, 6mm nickel-titanium closed-coil springs were ligated between the maxillary incisors and first left molars to deliver an initial force of 60g. Tooth movement was measured following sacrifice, 21 days after appliance insertion. Root resorption, PDL width and osteoclast number were histologically evaluated and compared between the groups. RESULTS: The mean amount of tooth movement was 0.62 mm in group A, 0.59 mm in group B and 0.38 mm in group C. OTM reduction following administration of atorvastatin was statistically significant (p<0.05), but there was no significant difference in the studied histologic variables among the three groups (p>0.05). CONCLUSION: According to the results obtained in the current study, atorvastatin appears to reduce tooth movement in rats; however its effect on osteoclasts, especially osteoclastic function, requires further investigation.

A comparison between craniofacial templates of Iranian and western populations.

Templates are very useful tools for diagnosis of malocclusions. A number of templates have been provided for some populations in previous years. Since craniofacial characteristics of different ethnic groups are not the same, each population needs its own norms. The aim of this study was to provide orthodontic craniofacial templates for 8-16 year old Iranian boys and compare dentoskeletal features between Iranian and western populations. 3330 boys with the age range of 8-16 years were examined in Tehran, and 107 cases were finally chosen for the study and their lateral cephalograms were traced. Since there is no universal, consensus about the selection of one specific point or line for cephalometric superimposition, both the sella nasion (SN) and basion nasion (Ba-N) lines were chosen for this purpose. Based on both SN and Ba-N lines, a template was prepared for each age. Simple linear regression analysis was used to evaluate the angles and the multivariant regression analysis for evaluation of landmark vectors. Posterior cranial base, maxillary and mandibular lengths, upper and lower anterior facial heights (N-ANS and ANS-Me) and posterior facial height (S-Go) are greater in Iranian population. But anterior cranial base, height and inclination of the incisors and molar height are similar in two populations.

Comparison of occlusal balance contacts in patients treated with standard edgewise and preadjusted straight-wire appliances.

This study investigated the functional occlusion in two groups of patients treated to a Class I canine and molar relationship by fixed appliance therapy. Group A consisted of 24 patients treated with standard edgewise appliances, whereas the 15 patients in group B were treated with a straight-wire appliance. The occlusal contacts were assessed intraorally with articulating ribbon of 8 microns thick. All procedures and measurements were performed by the same examiner. The results revealed that balancing contacts were significantly more frequent in group A. In both groups, most subjects had balancing contacts between their second molars (P<.05). The prevalence of posterior protrusive contacts in group A was similar to group B. Most of the subjects in group B demonstrated canine guidance on laterotrusion, whereas in group A, the majority exhibited group function (P<.05). Mutually protected occlusion was present in an overwhelming percentage of group B, as compared to no patient in group A (P<.05). Patients treated with edgewise appliances did not exhibit ideal functional occlusal relationships, whereas most individuals after straight-wire appliance therapy had a mutually protected (ideal) occlusion.

Comparison of wire loop and shear blade as the 2 most common methods for testing orthodontic shear bond strength.

INTRODUCTION: The purpose of this study was to compare 2 common methods of measuring orthodontic shear bond strength. METHODS: Brackets were bonded to 40 bovine incisors, and the teeth were mounted in a jig. The teeth were paired for symmetry, and the pairs were divided into 2 groups for debonding. In group 1, the shear force was applied with a rectangular wire under the tie wings. In group 2, a shearing blade applied force to the junction between the bracket base and the adhesive. RESULTS: Debonding with the shear blade produced higher (24.86 +/- 7.44 MPa) and more dispersed (coefficient of variation = 29.91%) bond strengths compared with the wire loop (17.12 +/- 3.16 MPa, coefficient of variation = 18.44%). Adhesive remnant index (ARI) scores showed a tendency for cohesive failure in the enamel in the shear-blade group (ARI = 5) compared with adhesive failure (ARI = 3) in the wire group. CONCLUSIONS: There is a need to standardize bond strength tests. The results of this study favor the wire-loop method, which might have more similarity to clinical loads. The regression formula might make comparison of previous studies easier.