Iranian Journal of Orthodontics
Volume:6 Issue: 3, Sep 2011

Third molar impaction is usually related to lack of space for eruption. The aim of this study was to assess third molar angulation following extraction and non extraction orthodontic treatment.
This study was carried out on pretreatment and post treatment panoramic and cephalometric radiographs of 70 CL I malocclusion patients. Thirty-five patients (24 female and 11 male) with mean age of 16.3±1.8 years had been treated with extraction of four first premolars (extraction group) and thirty-five patients (27 female and 8 male) with mean age of 16.9±2.6 years had been treated without extraction (nonextraction group). In each group, upper and lower third molar angulation, on pre and post treatment radiographs were assessed. Changes in third molar angulations from pretreatment to post treatment in each group were assessed with Mann- Whiteny U test . Changes in two groups were compared with Wilcoxon test.
statistical analysis revealed some degree of improvement in third molar angulation in both groups . changes of upper left third molars in extraction group and upper right and lower left third molars in non extraction group were statistically significant . The changes of third molar angulation between two groups were not statistically significant.
Extraction of first premolars during orthodontic treatments does not influence unerupted third molar angulation.

Aim: Evaluation of facial shape and proportions is one of the most important steps in determining treatment options and outcomes. Balancing the position of the lips in relation to the nose and chin has a direct effect on patient aesthetic preference. Therefore the aim of this study was evaluation of the correlation between nasolabial angle and antero-posterior position of maxilla in orthodontic patients who referred to private dental office in Yazd city.
Material and In this cross- sectional descriptive study position of maxilla were evaluated based on Mc. Namara and Steiner analysis in the lateral cephalometric radiographs of 47 orthodontics patients (21 male and 26 female). Nasolabial angle (NLA) and lower nasolabial angle (LNLA) were measured and correlation between these parameters were analyzed by ANOVA test and Pearson’s correlation tests using SPSS(version 16).
Diffrences of Wit’s appraisal SNA and Mc namara values amoung three groups of maxillary deficiency, maxillary excess and orthognatic patients were statistically significant (p.value0.05)
Due to compensation of skeletal problems by teeth, NLA can not describe position of maxilla perfectly.

Soft tissue changes and especially smile is one of the most important parameters in diagnosis and treatment planning in orthodontics. The main aim of this study was evaluating the correlation of the smile line with verticaldental parameters of occlusion.
In this cross sectional study, 46 patients (23 females and 23 males) aged between 18 to 25 years old were selected. The subjects were asked to pose a smile and several variables were measured and recorded which were mainly related to smile line. A lateral cephalometric radiography was ordered for each patient and anatomic landmarks were determined. And then correlation between 6 vertical dental parameters and some smile variables were analyzed. In order to determine association between quantitative variables, correlation coefficient of Pearson was used. P There was significant correlation between palatal-occlusal plane with quantitative variables such as tooth-lower lip position and inter labial distance during smile. No significant correlation was seen with other smile variables. There was significant correlation between upper 6 to palatal plane with smile width but no correlation was found with other smile variables. Upper 6 to Frankfort plane had significant correlation with clinical crown and smile width but not with other smile variables.
According to the result of this study, dental vertical variables affect the vertical component of smile, which means vertical development in the dentition can lead to the distance between some vertical variables of posed smile.

Aim: The objective of this study was to determine the effect of thermocycling on shear bond strengths (SBSs) of a light cured compositeafterdifferent thermal cycles.
80 Bovine incisors were randomly divided into 4 groups of 20 teeth. Each teeth were etched with 37% phosphoric acid and brackets were bonded using a light cured composite (Resilience). Thermocycling was done between 5° C and 55° C for 500, 3000 and 6000 cycles in group 2,3 and 4 respectively. Teeth in group1 (control group) were not being thermocycled. The SBS values were measured by means of Dartec testing machine.
The results showed significantly higher SBS values for the control group compared to test groups (2-3 and 4). No significant different was observed between test groups.
Thermal changes during thermocycling significantly reduce the mean SBS of conventional etch and rinse adhesive system (Resilience), but SBS in 500, 300 and 6000 cycles had no significant difference. Clinical significance: Alteration in values of shear bond strengths under thermocycling would be representative of expected behavior of orthodontic brackets in clinical situations.

Cleft lip and palate is among the most common congenital anomalies of the head and neck region. Treatment of cleft lip and palate is challenging and requires the cooperation of various medical teams. A 15 year-old patient with a cleft lip and palate presented to the Department of Orthodontics at ShahidBeheshti University, School of Dentistry complaining of unattractive appearance. The patient had unilateral cleft lip and palate and congenitally missing maxillary left lateral incisor and mentioned a history of surgical repair of the cleft in childhood. He had a concave profile, -5mm overjet, -5 mm Wits appraisal and abnormal eruption path of teeth especially for the maxillary left central incisor. The patientunderwent orthodontic treatment without orthognathic surgery. Post-treatment records showed excellent results in terms of occlusion and facial balance and harmony.

Since orthodontic therapy may have detrimental effects to the tooth structures or periodontium, practitioners recommend their patients to use different mouth washes. These chemical agents may be potentially damaging to metal components of orthodontic appliances. The aim of the present study was to evaluate the effect of three common mouthwashes on mechanical properties of NiTi orthodontic wires.
27 pieces of 0. 016inch Niti wires were randomly assigned into 9 groups including 3 control and 6 experimental groups. After the first month of immersion in artificial saliva, the wires in 3 groups were immersed in Chlorhexidine, Persica and Hydrogene Peroxide for 30min, 1. 5h and 1. 5h respectively. The control groups included asreceived wires, wires immersed only in artificial saliva and Saliva tooth brush. Mechanical properties of the wires were evaluated by three point deflection test. Two way ANOVA and Tukey tests were used to compare groups.
Persica caused significantly lower force in 2 and 3 mm deflection during loading compared to Peroxide, chlorhexidine and “as received”. Chlorhexidine also significantly reduced the loading force during 3mm deflection in comparison to saliva control. In 2 mm deflection during unloading Persica significantly reduced unloading force in comparison to all groups including: chlorhexidine, peroxide, saliva control and “as received”. It is also seen that chlorhexidine caused lower force compared to saliva control. Then, NiTi wires in 3 groups underwent 3200 tooth brushing cycles and were compared with each other and with 2 control groups (saliva brushing and «as received») by Tukey test. The results showed that only in 3mm loading deflection there was significant difference between Persica and Peroxide, and also between peroxide and as received wires.
Persica was the most effective mouthwash on mechanical properties of NITI wires.

Third molar impaction is usually related to lack of space for eruption. The aim of this study was to assess third molar angulation following extraction and non extraction orthodontic treatment.
This study was carried out on pretreatment and post treatment panoramic and cephalometricradiographs of 70 CL I malocclusion patients. Thirty-five patients (24 female and 11 male) with mean age of 16.3±1.8 years had been treated with extraction of four first premolars (extraction group) and thirty-five patients (27 female and 8 male) with mean age of 16.9±2.6 years had been treated without extraction (nonextraction group). In each group, upper and lower third molar angulation, on pre and post treatment radiographs were assessed. Changes in third molar angulations from pretreatment to post treatment in each group were assessed with Mann- Whiteny U test . Changes in two groups were compared with Wilcoxon test.
statistical analysis revealed some degree of improvement in third molar angulation in both groups .changes of upper left third molars in extraction group and upper right and lower left third molars in non extraction group were statistically significant . The changes of third molar angulation between two groups were not statistically significant.
Extraction of first premolars during orthodontic treatments does not influence unerupted third molar angulation.

The maxillary canine is the second most frequently impacted tooth following third molars. The etiology of the impacted canine is obscure, but probably multifactorial. There are some evidences that patients with a few certain features of occlusion may be at higher risk to the development of impacted canine. The aim of this study was to investigate the association between occurrence of canine impaction and other aspects of occlusion.
This study was conducted with patients aged 14 years or older who consequently presented to Orthodontics clinic, School of Dentistry, Hamedan. The patients with impacted canine were examined for occlusal condition clinically . Data were recorded and analyzed statistically.
28 males and 69 females withcanine impaction were found among 600 evaluated patients. Of 97 patients with impacted canine, 48.5% had occlusal relation of Class I, 21.6% of Class II D1, 18.6% of Class II D2, and 11.3% of Class III. The statistical analysis showed that there is no relation of impacted canine to occlusion, as well as to crowding, agenesis, anterior or posterior cross bite (P> 0.05), but canine impaction presented a significant correlation to smaller size of lateral incisors and spacing (P The study concluded that there was anassociation between canine impaction and the small size of lateral incisor and spacing.