Comparison of mechanical properties between three different types of T-loop

T-loop is one of the most popular closing loops in orthodontic profession. However its activation is in the contrary to Bouschinger effect theory, since the formed bends would be opened during activation. The purpose of this study was to add a helix in a way to be more respondent to the Bouschinger effect theory.To compare the load deflection, maximal elastic load and range between three different types of T-loop.5 sample of each 3 different designs of T-loop [group 1: original T-loop, group 2: T-loop with the two inner helices, group 3: T-loop with the two helices constructed outside the horizontal part] had been tested with universal testing machine [Instron]. The load -deflection curves was plotted and the mechanical properties [load deflection, maximal elastic load and range] were measured. One way ANOVA was used to identify statistical differences between designs.The mean value of maximal elastic load in group 1 [6.02 +/- 0.27] was significantly higher than group 2 [5.16 +/- 0.46] and in group 2 were significantly higher than group3 [4.35 +/- 0.25] [p<0.001]. A significantly higher load deflection was reported in group 1 [0.73 +/- 0.36] in comparison to group2 [0.56 +/- 0.74] and group 3[0.56 +/- 0.69] [p=0.002], with no significant difference between two latest groups [p=0.999]. The mean range in group 3 [4.15 +/- 0.10] was significantly lower than group 1[5.43 +/- 0.13] and group 2 [5.59 +/- 0.15] [p=<0.001] with no significant difference between group 1 and 2 [p=0.149].The results revealed that increasing length of T-loop with helices will decrease Load deflection rate the place and design of helices might not be a crucial factor. The new design of T-loop with helices relevant to Bouschinger effect theory needs a further survey regarding their position

Effect of recycling and autoclave sterilization on the unloading forces of niti closed-coil springs: an in vitro study

Statement of Problem: Clinicians use the NiTi coil springs frequently for its appropriate mechanical properties

Purpose: The aim of this study was to determine the effect of recycling and autoclave sterilization on the unloading forces of NiTi closed coil springs

Materials and Method: Fourteen NiTi closed coil spring with the length of 9mm were selected. Each coil was stretched to a peak extension of 12 mm. A universal testing machine was used to acquire load/deflection curve of the coil springs at 25+/-2°C. The influence of thermocycling [1000 cycles,5-55°C], autoclaving [134°C, 32PSI, 3min] and mechanical strain [9mm extension] which simulated the oral condition, were considered. Data were statistically analyzed by adopting Repeated Measures MANOVA Paired t-Test

Results: Autoclaving in the 1, 4, 6 steps increased the force levels of coil springs about 2- 5gf [p< 0.01]. Thermocycling reduced their force levels about 4-6gf. Prolonged strain at 3, 5 steps decreased the magnitude of forces levels about 3-4gf

Conclusion: Concerning all the limitations; according to the results of this study; it is possible to recycle Ni-Ti closed-coil springs without significant reduction in their force levels

comparison of apical root resorption in incisors after fixed orthodontic treatment with standard edgewise and straight wire [MBT] method

Statement of Problem: One of the major outcomes of orthodontic treatment is the apical root resorption of teeth moved during the treatment. Identifying the possible risk factors, are necessary for every orthodontist

Purpose: The aim of this study was to compare the rate of apical root resorption after fixed orthodontic treatment with standard edgewise and straight wire [MBT] method, and also to evaluate other factors effecting the rate of root resorption in orthodontic treatments

Materials and Method: In this study, parallel periapical radiographs of 127 patients imaging a total of 737 individual teeth, were collected. A total of 76 patients were treated by standard edgewise and 51 patients by straight wire method. The periapical radiographs were scanned and then the percentage of root resorption was calculated by Photoshop software. The data were analyzed by Paired-Samples t-test and the Generalized Linear Model adopting the SPSS 15.0

Results: In patients treated with straight wire method [MBT], mean root resorption was 18.26% compared to 14.82% in patients treated with standard edgewise technique [p< .05]. Male patients had higher rate of root resorption,statistically significant [p< .05)]

Age at onset of treatment, duration of treatment, type of dental occlusion, premolar extractions and the use of intermaxillary elastics had no significant effect on the root resorption in this study

Conclusion: Having more root resorption in the straight wire method and less in the standard edgewise technique can be attributed to more root movement in pre-adjusted MBT technique due to the brackets employed in this method

Awareness of Iranian's general dentists regarding the latest prophylaxis guideline for prevention of infective endocarditis

Statement of Problem: Dental procedures leading to oral tissue injuries may provoke bacterial release to the blood stream causing infective endocarditis [IE] in vulnerable patients. The guideline which was proposed by AHA has been updated 9 times having the last update published in 2007. This study was endeavored to uncover the level of knowledge of general dental practitioners in Shiraz, concerning the 2007 AHA guidelines for endocarditis prophylaxis in patients with cardiac problems receiving dental treatments

Materials and Method: This cross- sectional and descriptive analytical study included 150 dentists as participants. All practitioners were given a self -report questionnaire which consisted of three sections. Questions were designed to assess their knowledge of antibiotic prophylaxis in patients with cardiac disease

Results: Almost all participants [93%] were aware of antibiotic prophylaxis to be essential for tooth extraction. Most participants did not believe in prophylaxis for noninvasive procedures [such as shedding of primary teeth, impression, intraoral radiography]. From all of the respondents, 75% considered Amoxicillin to be the antibiotic of choice and 57% were acquainted with the correct dose of Amoxicillin for high risk patients

Conclusion: The study identified a potential for under/over prescription of antibiotic prophylaxis under the current guideline. Burden of IE necessitates more accurate knowledge of antibiotic prophylaxis in the undergraduate curriculum and continuing education programs of dentistry

Comparison of dental arch changes and patients' discomforts between newly designed maxillary expansion screw and slow expansion procedures

Statement of Problem: One fourth of orthodontic patients can benefit from maxillary expansion but traditional expansion screws produce unfavorable heavy interrupted forces. A new spring- loaded expansion screw was designed which created light and continuous forces

Purpose: The purpose of this study was to compare the treatment effects and patients, discomfort with removable slow maxillary expansion and newly designed spring loaded expansion screw

Materials and Method: 35 healthy Iranian children were divided randomly to two groups: group I [25 patients] treated by removable expansion appliance and group II [10 patients] treated by spring- loaded expansion appliance. The active phase of expansion was monitored and arch sizes of the upper dental arches [inter- canine, inter- premolar, inter- molar and arch perimeter] were measured with a caliper on casts monthly. The patients requested to mark the intensity estimation of their discomforts during wearing of appliance on questionnaires which comprised 12 statements. The scores of individual question were added up to obtain a total score. The independent ttest and Mann- Whitney U-test were applied to analyze the data

Results: There were no significant differences in both groups in the mean of arch size changes in each appointment [p >0.05]. There was no significant difference in both groups in terms of the mean of scores of questionnaires [p =0.352]

Conclusion: There was no significant difference in terms of patients, discomfort and arch size changes in spring- loaded and removable expansion appliances. Since the newly designed expansion appliance does not need to be activated by patients, it might be assumed a proper substitute for traditional expansion appliances

Impact of an educational leaflet on parents' knowledge and awareness of children's orthodontic problems in Shiraz

Raising parents' awareness about dentofacial malocclusions is important for avoiding delays in seeking treatment. The aim of the present research was to assess the impact of an educational leaflet on parent's knowledge and awareness of orthodontic malocclusion in children. Parents of 533 7-9-year-old schoolchildren were randomized into a leaflet group who received an educational leaflet and a control group with no leaflet. Pre-and post-intervention test scores on a questionnaire about orthodontic problems were compared. Differences between post- and pre-test scores were significantly higher in the leaflet group than the control group for the total score and the domain on general awareness of orthodontic problems. Scores on the domain of knowledge of referral intervals did not differ significantly. Information leaflets may be useful for increasing parents' awareness of orthodontic problems in children

Assessment of parental awareness about malocclusion in Shiraz, Islamic Republic of Iran

Information empowers people to take charge of their health. The aim of this study in Shiraz, Islamic Republic of Iran was to evaluate parents' knowledge about dental malocclusion, referral routes and information sources. A random sample of 1000 7-9-year-old schoolchildren were given a questionnaire to complete at home. Questionnaires were completed by 795 parents. Knowledge about malocclusion was significantly greater in families with higher levels of education and income. Most respondents [83.5%] were aware of the importance of maintaining primary teeth to prevent malocclusion, and 25.1% thought that carious primary teeth must be extracted. Half of the parents [50.6%] did not know that spaces between primary teeth are normal. Only 28.8% of the children visited dentists for annual routine check-ups. Television [43.3%] was the most common source of dental information. The level of general public awareness about malocclusion needs to be improved

Prevalence of malocclusions in school-age children attending the orthodontics department of Shiraz University of Medical Sciences

To provide quantitative data about the prevalence of malocclusions in the Shiraz orthodontic population, we studied the records of 700 patients [391 girls and 309 boys] aged 6-14 years attending the undergraduate Department of Orthodontics at Shiraz University of Medical Sciences. The prevalence of Angle class I, II and III malocclusion of first molars was 52.0%, 32.6% and 12.3% respectively. Skeletal class I, II and III malocclusion was found in 18.0%, 70.0% and 12.0% respectively. There were no significant differences between the sexes in the prevalence of different types of skeletal malocclusion. Children with class III were significantly younger [mean age 8.9 years] than those with class I [9.6 years] or class II [9.7 years] malocclusions. Orthodontics students need more education and training in the management of class II malocclusion to improve the overall quality of care for patients

[Relation between craniofacial dimensions and anterior teeth size]

Size and form of teeth is not only important for aesthetic, but also should be in harmony with other parts of face. When there is no record before tooth loss, determination of proper tooth size is one of the most important step of treatment. The purpose of this study was to determine correlation ratio of mesiodistal widths of anterior teeth with craniofacial dimensions. In this cross-sectional study 100 cases [50 males and 50 females] were selected from dentistry students. Maximum frontal width, maximum bizygomatic width, bigonial width and cranial width were measured by face bow. Mesiodistal width of anterior teeth was measured by digital vernier. For analysis of data Pearson correlation and multiple regression tests were used. Anterior Bolton ratio [78.76 +/- 2.8] was not significantly different from normal anterior Bolton ratio. Bizygomatic width and canine widths showed a significant relation [0.2-0.3] and also bigonial width and lower canine width had a significant relation [0.2-0.3]. Proportions of bizygomatic width to upper centrals were 14.9 on right side and 14.7 on left side. A significant relation between upper and lower intercanine widths with bizygomatic and bigonial widths was found [p<0.05]. Although there are different ways for prediction of tooth size, according to relation between some craniofacial and tooth widths, these craniofacial widths can be used for prediction of tooth size

[Correlation between index of orthodontic treatment need [IOTN] and self-evaluation in 18-22 year old patients]

Index of orthodontic treatment need [IOTN] has several applications and advantages for determination of orthodontic treatment need. Due to the effects of different factors such as gender, age and socioeconomic status on treatment need based on self evaluation, it is important to evaluate correlation between orthodontic treatment need assessed by self- evaluation and real treatment need assessed by IOTN. The purpose of this study was to evaluate the correlation between orthodontic treatment need as assessed by IOTN and self- evaluation in 18-22 year old patients. Of 18-22 year old patients referred to Shiraz dental clinics, 240 were selected by random cluster sampling method. IOTN and self- evaluation questionnaires were filled in. In self-evaluation questionnaire, the mean scales for all the questions were determined as the scale of patient. The correlation between treatment need as assessed by IOTN and self-evaluation was evaluated by Pearson correlation and Partial correlation statistical analysis. There was a significant moderately positive correlation between Dental Health Component [DHC] and self-evaluation [r=0.51]. Also, the correlation between Aesthetic Component [AC] assessed by the examiner and patient and self evaluation was significantly positive. [r=0.39, r=0.31]. The significantly positive correlation between IOTN and self-evaluation indicates that in assessment of orthodontic treatment need, not only standard indices but also self-evaluation of the patient should be taken into account

[In vitro comparison of load activation rate of a designed screw with other common expansion screws]

Expansion screws such as Hyrax and Hass have high load-activation rate and their force system is somehow far from ideal for moving teeth. Hence, activation of such screws produces heavy forces that decay rapidly. Also, rapid reactivation of the appliance has the potential of damaging the teeth and periodontium. Moreover, lack of patient's cooperation in activation of screw could be considered as one of its main disadvantages. The purpose of this investigation was to assess and compare the force- activation curve of a designed screw with those of the commonly used expansion screws. In this experimental study, a screw was designed and manufactured in similar size as the other screws with the potential of 8 millimeter expansion in 2 times activation. The screw was embedded in acrylic material in a removable appliance and fixed on its plaster cast. The compression test machine was used to depict its load-activation curve. The curve was compared with other screws' curves. The results of this study showed that the designed screw had a lower load-deflection rate than other screws. It generated a light continuous force of 2- 3.5 pounds for 4 millimeter expansion. Compared with other screws which produce heavy and interrupted forces, the designed screw generated a light continuous force

[ comparative study between treatment outcomes of class I cases treated by Begg and Edgewise orthodontic systems]

Today there are two common and different systems available for orthodontic treatments: Begg and Edgewise techniques. Occlusal indices have the greatest reliability for comparing treatment outcomes, so in this study we used Peer Assessment Rating index for comparison of treatment outcomes of these two systems. Peer Assessment Rating index evaluates buccal occlusion [Antero-posterior, vertical and transverse], overjet, overbite and midline by scoring them. The purpose of this study which has been conducted for the first time, was to compare occlusal PAR index in class I patients treated by means of Begg and Edgewise methods. In this cross sectional study, 120 pre-treatment models of 60 class I patients were evaluated by Peer Assessment Rating index. [30 class I patients with Begg method and 30 class I patients treated with edgewise method were selected randomly from two separate private clinics]. Pre-treatment PAR indices in both groups were comparable. Changes in PAR index after treatment was compared between the two groups. Result were analyzed by general linear model and mANOVA. Sex and age distribution between the two groups were matching. Using PAR index, only improvement in buccal occlusion in Begg group was more significant than edgewise group. Considering total PAR index, no significant difference was obtained between the two groups, although duration of treatment in Begg method was significantly shorter than Edgewise. Occlusal outcomes [total PAR index] were similar in Begg and Edgewise methods. Treatment results by Begg method accomplished in shorter duration than Edgewise treatment