Iranian Journal of Orthodontics
Volume:5 Issue: 1, Mar 2010

Desirable tooth movements need optimal force systems. Loops are employed to move teeth properly. Lloop is used frequently due to its ease of fabrication. The aim of this study is to assess the expected forces and moments when a definite length of wire is bent to form L-loop. In other words, the effect of loop height and width on the produced force and moment is evaluated by the finite element method (FEM).
Six 3D finite element models were designed of an L-loop without pre-activation bends keeping the total lengths of wire equal to 24.34 0.5 mm. The cross section of wire was 0.016”× 0.022”. The force produced by activation in a 0.1 millimeter increment was recorded.
In model L1, the findings start with 0.086 N in 0.1 mm of activation and increased to 0.88 N in 1 mm of loop opening. The pattern of findings was almost the same for other loop designs (L2 through L6) with an increase in findings. M/F ratios were almost constant in a loop design along its activation starting with 3 in L1 and reaching about 1.9-2 in L6.
Moment to force ratios were almost constant in a loop design along its activation. increasing width and decreasing height with almost the same length of loop wire can increase force and therefor reduce M/F ratio.

Aim: The objective of this study was to compare and evaluate the effects of two functional appliances including modified activator and modified twin block appliances on the profiles of facial soft tissue.
This study included 30 patients suffering from skeletal class II abnormalities. Participants were randomly allocated into one of two treatment groups for functional appliances, the modified twin block group and the modified activator group (ten girls and five boys, with a mean age of 10.4± 0.82 years in the modified twin block group; nine girls and six boys, with a mean age of 9.8± 0.94 years in the modified activator group). The mean duration of treatment was 20.4± 6 months in the modified activator group, and 17.9 ± 5 months in the modified twin block group which included the eight months of aftertreatment maintenance. Data were analyzed using a paired t-test and an independent samples t-test.
In the modified activator treatment group, changes in the labiomental angle (p=0.02), the angle of facial convexity (p=0.004), the Ls-S vertical (p=0.034), the distance between the labial surface of the upper central incisor and the upper lip (p=0.012), the Li-E Line (p=0.029), the total anterior facial height (p=0.008) and the pog’-S vertical (p=0.013) were significant. The difference between two groups was significant only in Li-E line.
The effects of modified activators and modified twin block appliances on the soft tissue profile was almost the same, and both resulted in significant alterations to the soft tissue profile.

Aim: Disorders of dentition and gums are highly common in contemporary societies and its prevalence is increasing gradually. All psychological and social problems due to dentofacial esthetics and oral function and periodontal disease deterioration and dental caries has made orthodontic treatments important and considering that the relationship of molars is the key to occlusion, this study examines the occlusion relationship (1st molar- canine).
1800 students aged 9-10 from 20 regions of Tehran were randomly selected and studied using cross-sectional method. After excluding mentally retarded and aberrant ethnicities and those with previous orthodontic treatment from sample size, the remnants were examined as 5 groups (class I, class II, class III, different right and left, unidentifiable) based on Angel classification.
48.4% of subjects were identified to have class I occlusion, 25.6% class II, 6.7% class III, 15.9% had different right and left, and 3.3% had unidentifiable occlusion.
the prevalence of normal occlusion in this study was much lower compared with similar studies in other parts of the world and in Iranian literature as well. Malocclusion showed an ascending fashion; disagreement of class I and II malocclusions with similar Iranian and foreign studies seem to explain genetic background, type of diet, differences in instrument and measurements, and sample size and ethnicity and other factors.

Aim: of this in vitro study was to evaluate the effects of Co2 laser irradiation on demineralization adjacent to orthodontic brackets and their shear bond strength in human premolar teeth. Enamel demineralization adjacent to orthodontic brackets is a major problem that requires new professional method independent to patient cooperation.
Sixty human premolars were randomly divided to two groups (n=30). Group1, enamel surface irradiated with Co2 laser. Group2 without any enamel surface treatment. In both groups, a bracket at buccal surface was bonded with Transbond XT and cured with conventional light cure. Demineralization in all sample induced with artificial caries solutions. A universal testing machine was used to determine shear bond strengths. The teeth were sectioned bucco-lingually and were evaluated under polarized light microscope. Average lesion depths were calculated from three depth measurements. The Two independent sample T- tests were used to compare the study type group in detail.
The mean of shear bond strengths in the group1 and 2 were 13.90±5.01and 15.84 ±3.68 Mpa respectively, but not statistically significant (P=0.102).The mean lesion depth in group1and 2 was 72.29±58.09 µm 120.01±76.49µm respectively, which was significant (P=0.018)
Co2 laser irradiation can reduce enamel demineralization while not affecting the shear bond strengths significantly.

Aim: Facial appearance is an important factor for a successful orthodontic treatment that include softtissue profile, finding of standard cephalometric values for various population can be useful. The aim of this study was To detect the mean soft tissue facial profile for Iranian adolescent as determined by the Holdaway analysis and also detect any differences between values of boys and girls.
Lateral cephalometric radiographs for 58 Iranian adolescent with normal occlusion were used. sample were consist of 35 girls (mean age 16y,7m) and 23 boys (mean age 15y,3m). All of subjects were positioned in cephalostat with the lips in rest and the teeth in centric occlusion. The landmarks were detected on the basis of Holdaway definition.
Iranian soft tissue showed differences in some variables when comparing to Holdaway ideal values including upper lip sulcus depth, soft-tissue subnasal to H-line, inferior sulcus to H line, skeletal profile convexity and H angle, but all of them were in the normal range. Soft tissue chin thickness was the only parameter that showed differences from normal range. When comparing two sexes, upper lip thickness and soft tissue chin thickness were greater in boys in relation to girls.
Persian people differ from Holdaway''s soft tissue norms in an increased skeletal profile convexity, H angle, and soft tissue chin thickness. These are recommended for use when formulating a treatment plan for this ethnic group. Iranian boys had thicker upper lip and greater soft tissue chin thickness in relation to girls.

Aim:The aim of this study was to compare the shear bond strength [SBS] of two different light sources, light-emitting diode and quartz-tungsten halogen, under thermal cycle frequencies.
Method and materials:Sixty human premolar teeth were divided into two groups, on which composite (Transbond XT™ adhesive paste) cured with light-emitting diode in group I, and with quartz-tungsten halogen in group II. Samples thermocycled 500 cycles, the exposure to each bath was 10 seconds and the transfer time between the two baths was 10 seconds. 500 cycles between 5°C and 55°C were performed. An Instron testing machine [Dartec Hc.10, England] was used for the shear bond test at a crosshead speed of 1mm/min. Force was applied directly to the bracket–tooth interface. The load at failure was recorded by a personal computer connected to the test machine. SBS values were expressed in mega Pascal [MPa]. T-test was used to compare the shear bond strength between two groups.
The comparison of both groups indicated that the quartz-tungsten halogen groups demonstrated higher mean shear bond strength [p=19.947Mpa] than light-emitting diode groups [19.878Mpa]. There was no statistical difference in the shear bond strength values between the two light sources. [P value =0.918]
Both light sources showed favorable shear bond strength performance and there was no statistical difference in the shear bond strength values between these two light sources.

Aim: the main goal of this study was to investigate the relationship between Kurdish orthodontic patients’ severity of malocclusion and their social and psychological impact.
The sample consisted of 100 patients, 45 males and 55 females, aged 13–22 years. A translated pre-tested questionnaire [Psychosocial Impact of Dental Aesthetics Questionnaire PIDAQ] was used to assess the subjects’ social and psychological impact by their occlusal irregularities; the actual severity of malocclusion was determined using the Dental Aesthetic Index (DAI) on 100 stone study models. Statistical analysis was carried out using chi-square test for assessing the associations, Spearman and Pearson correlation coefficients used for assessing correlations. Analysis of variance and multiple regression tests were also carried out to complete the statistical analysis.
of the multiple regression analysis showed that not only DAI score were significantly associated with higher score of PIADQ but other factor like Gender was a significant variable in predicting the psychosocial impact of dental esthetics, while age was not significantly associated with PIADQ scores.
there was significant weak positive correlation between DAI score and PIADQ scale of the study sample at p

Hyperdontia is more common in the permanent dentition than primary teeth. The rampancy of hyperdontia in the permanent dentition is reported to vary between 0.1 and 3.8 % and its rampancy in the primary dentition is found to be 0.3-0.8 %. A 20-year-old woman contacted the Faculty Practice Clinic at the Tehran University with concern regarding tooth caries. The panoramic radiography showed seven retained supernumerary teeth. Several clinical exams were then performed to rule out the presence of systemic pathology, and they all showed normal results. It is reported that the premolar region in the lower arch is the most common place for supernumerary teeth. Worldwide; many studies have reported the prevalence of supernumerary canines, which has been estimated from 0 to 1.5%. In our case occlusion was normal and no discrepancies observed.

Since the publication of Angle’s definition of malocclusion types, many cephalometric researches have been carried out to determine characteristics of Class II division 2 malocclusions; however controversies still remain. Considering the fact that a high percentage of patients seeking orthodontic treatment have this malocclusion, the present study was conducted in order to investigate Cross-Sectionally the cephalometric characteristics of Class II/2 malocclusions in 8-12 years old patients of Tehran Orthodontic Clinics. Patients’ files and pretreatment dental casts were screened, 30 Class II Division2 (17 girls, 13 boys) and 30 normal occlusion subjects were selected, each lateral cephalograms was traced and 36 dental and skeletal parameters were measured. Moreover student t test was carried out to assess the differences between malocclusion groups. Besides maxillary incisal position (retruded in class II/2 group) which was used as an inclusion criterion, the following differences were observed: 1-The maxillary position is retruded compared to normal group. 2-The mandibular length is longer but its sagittal position is retruded. 3-The chin is more prominent. 4-The mandibular growth vector is horizontally oriented and the mandibular plane is flat, creating the appearance of a hypodivergent facial pattern. So Lower anterior facial height was on average smaller. 5-And finally retroclination of mandibular incisors compared to normal group is evident. These findings indicate that besides the dental characteristics, Class II/2 malocclusion patients are also skeletally different from normal occlusion group to a certain extent.

Aim: Ideal facial esthetic and smile as one of it''s components are the major topics in orthodontic treatment. One important goal in modern orthodontics is harmony between facial soft tissue in static and dynamic state. The objective of this study is evaluation of correlation between facial index and modified smile index (MSI).
This study was a descriptive-cross sectional study. 130 patients who referred to orthodontic department of dental faculty of Yazd shahid sadoughi university of medical science were chosen. The facial index of subjects were determined on the basis of Farkas study as (N’-Gn’÷Zy-Zy ×100). Then photographs of their social smile from frontal view were captured and inter commissural distance (IC) and inter labial gap(ILG) were also measured and MSI was determined as [(ILG÷IC)×100]. By using SPSS software and statistical analysis (T-test and Pearson correlation) mean value of MSI and facial index was attained in men and women and The correlation rate between facial index and MSI was also evaluated.
The results of statistical analysis (T-test and Pearson correlation) showed that: The facial index mean value was 107.68±7.15 (108.39±7.26 in men and 106.98±7.03 in women).there was no statistical difference between 2 sexes. (Pvalue: 0.265) The MSI mean value was 17.76±3.79 (17.33±3.75 in men and 18.19±3.80 in women).there was no statistical difference between two sexes.(Pvalue:0.198) There was no statistical correlation between facial index and MSI (Pvalue:0.920)
There are different faces and MSI but there is no correlation between facial form and smile type.