فهرست مطالب

Orthodontics - Volume:3 Issue: 3, Dec 2008
  • Volume:3 Issue: 3, Dec 2008
  • تاریخ انتشار: 1387/09/11
  • تعداد عناوین: 10
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  • Mohammad Hossein Toodeh Zaim, Hossein Ahga Aghili, Zohre Tahatabaei *, Zahra Yousefzade Pages 59-64
    Aim
    Prediction of mesiodistal width of unerupted permanent canines and premolars in mixed dentition period is necessary for space analysis. Use of panoramic radiographs instead of periapical radiographs in space analysis decreases the cost and X-ray exposure. The aim of this study was prediction of mesiodistal width of unerupted permanent canine and premolars by panoramic radiographs.
    Materials and Method
    Panoramic radiographs and dental casts of 60 orthodontic patients were selected. The largest mesiodistal width of dental crown of upper and lower canines and premolars on the panoramic and dental cast and also mesiodistal width of lower incisors on dental cast were measured, SPSS was used and data were analyzed by Pearson's coefficient correlation between panoramic, cast and linear regression analysis and paired sample T-test.
    Results
    R for predication of total unilateral mesiodistal width of permanent canine and premolars from cast and panoramic in upper jaw was 0.589 and in lower jaw was 0.69l. R for prediction of mesiodistal width for unerupted canine and premolars by use of lower incisors width from dental cast and radiographic width of upper permanent canine for upper jaw and lower second premolar far lower jaw were respectively 0.664 and 0.999.
    Conclusion
    Based on introduced linear equation for prediction of mesiodistal width of canine and premolars, the best equation resulted from use of lower incisor width from dental cast and one radiographic agent which is canine in upper arch and second premolar in lower arch.
    Keywords: Mixed dentition, Linear regression analysis, Mesiodistal crown width, Panoramic Radiography
  • Mahtab Nouri, Amin Aminian *, Majid Heidarpour, Alireza Akbarzadeh Bagheban, Reza Massudi Pages 65-73
    Aims

    Comparison of 3D laser scanning and 2D conventional scanning in analysis of arch dimensions.

    Methods

    Twenty setups of upper and lower casts were duplicated in 20 corresponding dental stone models. 3D laser scanner was constructed in Shahid Beheshti University, and then casts were scanned with this machine. 2D scanning was performed by conventional scanner. Intercanine and intermolar widths and canine and molar depth were calculated directly on casts by digital caliper and on both scans. The mean differences between these three methods were evaluated by repeated measure analysis of variance and between each pair by paired t-test.

    Results

    The correlation between intercanine and intermolar widths of all three modalities were higher than 0.9, but for canine and molar depths the correlation was not so strong and for canine depth was the weakest (R=0.45).The differences between intercanine and intermolar widths of all three modalities for upper and lower casts were significant, but for canine (and molar) depths, only the difference between 3D and direct technique for the upper casts was significant (P < 0.05). The highest recorded differences for intercanine and intermolar widths and molar and canine depths were 0.67, 0.42, 0.59 and 0.71 mm respectively.

    Conclusions

    Digital models are valid reliable clinical tools for arch dimension evaluations. In addition, the most reliable measurements are intercanine and intermolar widths.

  • Soghra Yassaei, Zohre Tabatabaei *, Hossein Torabi Pages 74-79
    Aim
    Hyoid and its attached muscles involved in three basic functions: deglutition, phonation, respiration and control of pharyngeal spaces. The aim of this study was to valuate hyoid bone position in relation to facial growth pattern in class III malocclusion.
    Material and Methods
    This was a retrospective descriptive analytical study, performed on lateral ccphalograms of fifty patients with class III malocclusion with prognathic profile. Cephalograms were classified to three facial growth pattern groups so each group comprised of minimum 15 samples. T-test and ANOVA were used to compare the difference of mean value of growth pattern groups. P< 005 was considered as the level of significance.
    Results
    The difference between means of ANB angle (0.78 degree) were significant (P=0.027) in three facial growth pattern groups. The indices determining the growth pattern were significantly different in three facial growth pattern groups (P<0.001). The findings showed a significant difference in H-RGN between three facial growth pattern groups and also showed no significant difference in H-Pal P, H-SN, H-Mand P, H-C3 between three growth pattern groups.
    Conclusion
    The anteroposterior position of hyoid bone related to cervical colunm was not affected by facial growth pattern. But its antroposterior position related to mandible was affected by facial growth pattern. There were significant differences between hyoid bone position in three facial growth patterns. Vertical position of hyoid bone was not affected by facial growth pattern.
    Keywords: Hyoid, Growth Pattern. Class III Malocclusion
  • Shahla Momeni Danaei, Maryam Omidkhod, Morteza Oshagh *, Yaser Kerdegari, Amirhosein Najafi Pages 80-87
    Aim
    The main goal of this study was to assess the need and demand for orthodontic treatment among 14-18-year-old students in Shiraz.Subjects and
    methods
    1818 students (965 boys, 853 girls) were selected by using random cluster sampling process from the four education district of Shiraz. The dental health (DHC) and aesthetic (AC) components of the Index of Orthodontic Treatment Need were used as an assessment measure of the need for orthodontic treatment, Also, a questionnaire about demographic characteristics was completed. The examinations were carried out by two calibrated orthodontic post-graduate students. The data were analyzed using the student t-test and chi-squared test.
    Results
    The results showed 59.9% of students had "no need" for orthodontic treatment, 28.3% were in borderline category and 11.6% showed a definite need for an orthodontic treatment. Also, there was significant association between IOTN and father's education (P<0.003)
    Conclusions
    Less than one - fifth of 14-18- year- old students in Shiraz were considered in great need of orthodontic treatment using DHC of IOTN and girls had significantly higher need for orthodontic treatment than boys. This study provides baseline data on the need and demand for orthodontic treatment which is important for planning public orthodontic and dental services.
    Keywords: Malocclusion, students, IOTN (Index of Orthodontic Treatment Need)
  • Koroush Taheri Talesh, Javad Yazdani, Amir Mohammadi, Azin Sohrabi, Aydin Sohrabi * Pages 88-92
    Introduction
    It has been advocated that treatment of dentofacial deformities with jaw osieotomies may influence upper airway morphology, and several studies has shown that mandibular setback surgery has the potential to diminish airway size and alter the hyoid bone position.
    Objective
    The purpose of this study was to evaluate the effect of mandibular setback on the pharyngeal airway size, and hyoid bone position and to evaluate if a pre-surgical prediction on PAS can be made or not.
    Materials and methods
    Twenty eight pre- and post-operative (3-4 months) lateral cephalograms of 28 individuals (16 females and 12 males older than 17) who had undergone vertical ramus ostetomy setback surgery to correct skeletal class III discrepancies. Cephalograms were traced and a paired-sample t-test was used to evaluate the difference between 11 linear variables pre- and post-operative measurements. Coefficient correlation was calculated for the amounts of setback and the change in airway size.
    Results
    The vertical and horizontal position of hyoid and hyoid-mandible distance do not change significantly. Hyoid-2nd cervical vertebra and hyoid-pogonion distances reduced significantly. In the case of upper airway indicators, the width of pharynx was calculated at 4 different levels. In all 4 levels, statistical analysis revealed significant reduction but the correlation of reduction in the size of pharynx versus amount of setback is not significant (respectively from the most superior width to the most inferior one r=0.15, r=0.13, r=0.09, r=0.19).
    Conclusion
    This study suggested that mandibular setback surgery can decrease the pharyngeal airway size.
    Keywords: mandibular setback surgery, pharyngeal airway, Hyoid Bone
  • Allahyar Geramy *, Amir Hooman Sadr Haghighi, Seyed Amir Reza Fatahi Meybodi, Hasan Salehi Pages 93-99
    Aim
    Canine retraction is an important part of orthodontic treatments and should be coincided with preservation of posterior anchorage, The strain energy input of different appliance designs in teeth PDL is assessed.
    Materials and methods
    Eight 3D finite element (FE) models of upper right maxillary molars and second premolar were designed. The models contained teeth, their PDL, and bone with their attachments. Combinations of wire cross scetion(round and rectangular), force application on the first or second molar, including or excluding the second molar, and adding the second molar to the system via ligature wire is considered in different models. The strain energy input to the PDL of different teeth was evaluated.
    Results
    Engagement of all teeth, force application to the second molar resulted in 0.00017129 mJ and shifting toward applying force to the first molar resulted in 0.00017398 mJ. When the second molar was free from wire but laced; this energy finding was 0.00014499 mJ which increase to 0.0003991 mJ when the second molar was really out of the system. Findings for the rectangular wire were 0.00000084, 0.000001148, 0,0001026, and 0.0002929 respectively.
    Conclusion
    Rotation prevention of the second molar is the key point in using its anchorage value.
    Keywords: Canine Retraction, Anchorage Preservation, finite element method, Energy Analysis
  • Ladan Eslamian *, Kaveh Alavi, Sanaz Mehdizadeh Pages 100-108
    Background and Aim
    Conventional orthodontic treatment may affect on physical appearance and psychological aspect of patients. However, patient's attitude, expectations and self - concept influence the result of treatment. The aim of this study was to evaluate the expectations and self - concepts of patients referred to have orthodontic treatment to a private office and Shahid Beheshti, Dental School. Materials &
    Methods
    To evaluate patient's expectations and self-concept, a questionnaire consisting of 13 close and 2 open questions was prepared. To determine whether the problems of patients are realistic, an orthodontist visited all patients and recorded the findings on a structured questionnaire. In addition some variables that might influence the score that patients recorded to evaluate their own dental esthetic were analyzed. To analyze the data, Chi-square, t test, ANOVA, Kappa statistic and multi-variable linear regression model were used.
    Results
    Totally 252 individuals (92 males and 160 females) were evaluated. The most common orthodontic disharmony according to patient's view was irregularity in upper and lower front teeth (51.6%). Social problems were not common, but more than half of the girls sometimes had experienced shyness when laughing, due to their dental appearance. The patients' mean score to their own dental esthetic was 6.4±1.9, ranged from 0 to 10. This score was related to occlusion problems more than other variables.
    Conclusion
    The patients did not diagnose their occlusion problems properly. Nevertheless they had not low self - esteem.
    Keywords: Therapeutic expectations, Occlusion, Self - concept, Therapeutic incentives
  • Parviz Padisar, Mahtab Nouri *, Elham Zajkani Pages 109-115
    Aim
    One of the core parts of clinical orthodontics is the analysis of dentofacial growth. Changes that occur in the shape, form and size of dentoalveolar arch may result in various problems during diagnosis and treatment planning. The aim of this study was to investigate the late changes of alignment in the anterior teeth of mandible during 4-years follow up in young adults with normal occlusion in Qazvin
    Materials and Methods
    This was a longitudinal descriptive survey with 23 samples (13 girls and 10 boys). Subjects with an age range of 13±1 were selected for dentoalveolar change assessment. Two dental models were prepared from each subject one at the start of the investigation and one at the 4 years follow up; photographs of each model were taken at the time. Inter-canine distance, anterior arch depth, arch shape index, anterior teeth width (6 anterior teeth), anterior arch circumference (ATSALD) were measured using AutoCAD 2004 software and digital caliper. Means and standard deviations were measured using Npar test analysis. Data were compared at 0 and 4 years and between two genders using Wilcoxon test (P<0.05).
    Results
    The most prevalent changes in samples belonged to ATSALD (2.2mm increase) over the four years. The least changes were detected in arch shape index. Anterior arch circumference and ATSALD were the dominant changes in boys and girls, respectively.
    Conclusion
    During this critical growth period, anterior crowding of mandibular teeth increases in both boys and girls, while the inter-canine distance and arch shape index decrease.
    Keywords: Late irregularity, Crowding, Mandibular arch, longitudinal study, Normal occlusion
  • Ali Tayebi, Farnoosh Fallahzadeh *, Hamid Raji, Kazem Khosravi Pages 116-122
    Introduction
    One of the most important aspects of self-etching primer system in orthodontics is the duration of adhesive resin use after application of self-etching primer. Evaluating time delay effect on band strength is the objective of this study.
    Materials and methods
    In this interventional-axperimental study, premolar with sound buccal enamel were selected, and randomly divided in four groups, In the first group buccal surface were etched for 30 seconds, with 37% phosphoric acid. After washing and drying, primer XT was applied on teeth and brackets. Transbond XT was used in bonding. Light with 500 mw  was glowed from mesial, occlusal and distal surface for fifteen seconds, 5 and 10 minutes respectively. After thermocycling of all samples, debonding strength was measured with the help of DARTEC machine. Analysis was done by ANOVA and Duncan.
    Results
    The highest shear bond strength (19.4 Mpa) was seen in group one and the lowest (9.87 Mpa) in group four. Between the remaining groups and group one, there was a significant difference in mean shear bond strength. Scan electron microscope showed a strong deep tag between tooth enamel surface and adhesive in group one.
    Conclusion
    Significant difference in shear bond strength of two groups, traditional etching and self-etching primer was observed. Mean of shear bond strength with self-etching primer method was acceptable and delay in applying resin composite had no significant effect on shear bond strength of brackets to enamel.
    Keywords: resin composite, self-etching primer, acid etch technique
  • Mohammad Hosein Ahangar Atashi, Reza Fekrazad, Leila Ebrabimpour * Pages 123-130
    Aim
    The demineralization of enamel adjacent to orthodontic brackets is a clinical problem which can lead to some esthetic concerns after the treatment. The present study investigated the effect of laser, fluoride and combination of two techniques on the demineralization of enamel adjacent to orthodontic brackets.
    Materials and Methods
    In this in vitro study, 60 healthy human premolars were selected and the brackets were bonded to them. The specimens were randomly assigned to 4 groups (n=15): topical APF application, laser irradiation, Laser + fluoride and control specimens. Er,Cr:YSGG laser was irradiated at 12.5 mJ/cm2 pulse energy without water spray While APF gel was applied on the specimen surfaces for 4 minutes. All specimens were demineralized for 10 days in a 0.2M acetate buffer solution and the calcium content were subsequently determined with atomic absorption spectrometery. The data were subjected to analysis of variance and Tukey post hoc test.
    Results
    The mean calcium content of specimens with APF fluoride application was 6.52±1.241 PPM, in laser was 6.66±0.64 PPM, in laser + fluoride specimens was 6.21±0.77 PPM and in control ones was 7.09±0.56 PPM, The calcium content of specimens subjected to laser irradiation and fluoride was significantly lower than control specimens (p=0.029), while no other significant differences were noted in the next comparisons.
    Conclusion
    Er,Cr:YSGG laser irradiation does not increase acid resistance of enamel around orthodontic brackets with mentioned parameters, so, it is not recommended for clinical usage. Although, fluoride application following laser irradiation significantly increased acid resistance of specimens compared to control.
    Keywords: Er, Cr:YSGG laser, fluoride, demineralization, Acid resistance