Showing 9 results for Angle
H. Ravanmehr , K. Kashani ,
Volume 11, Issue 4 (8-1998)
Abstract
Facial prognathism, which is a problem in some orthodontic patients, is characterized by a number of cephalometric changes. Most clinicians use SNA angle in lateral cephalometric analysis to evaluate the amount of maxillary prognathism. Since SNA angle is not a reliable measurement for maxillary prognathism, and taking into account that the amount of prognathism changes in relation to cranial anatomy, according to Bjork it's better to measure the facial prognathism by the angle between anterior and posterior cranial base. According, two angles are recommended NSBa and NSAr.In this study 80 lateral cephalograms from three malocclusion groups, were studied and the amount of maxillary prognathism in relation to SNA and NSAr angles and their relationship to each other were measured.
The results were as follows:
1- Studying facial prognathism in relation to SNA and NSAr angles it was found that SNA angle is influenced by cranial base shape
2- The mean value of anterior and posterior cranial bases didn't show significant differences.
3- The mean value of SNA angle didn't show significant statistical difference in various malocclusion groups.
4- The correlation coefficient of ANB angle and wit's measurement is low.
A. Khavari , S. Yassaei ,
Volume 14, Issue 4 (1-2002)
Abstract
The purpose of this study was to investigate the soft tissue profile changes of the lower face following premolars extraction and incisor retraction. In order to do that, pre-and post treatment lateral cephalometric radiographs of 40 female orthodontic patients, with cl. II div. I malocclusion (22 patients) and bialveolar protrusion (11 patients) were analyzed. At beginning of orthodontic treatment, their mean age was 18.10 years, ranging from 15-24. All cephalometric radiographs were analyzed by a conventional and confirmed method called "combination analysis". The findings revealed that "lip tension" is a significant factor in soft tissue response to orthodontic treatment, so that in patients with lip strain, nasolabial angle increase was significantly more that those without lip strain. Moreover, regarding the increase of vermilion thickness of the upper lip, a significant difference was observed between two groups. In patients with lip strain, following premolars extraction and incisors retraction, lip strain was reduced or eliminated and upper lip vermilion thickness increased, following incisors retraction, the slope of nasal inferior border, in the group with lip strain, was reduced, while in the group without lip strain, this slope increased.
S. Nokar , A. Monzavi , F. Hashemi ,
Volume 15, Issue 2 (5-2002)
Abstract
Retention, resistance and marginal integrity mostly depend on tooth preparation. An appropriate convergence angle fulfil this purpose, to high extent. In this study, a new method was used to measure the convergence angle of the teeth prepared for single crowns in Genera! practitioners" offices in Tehran. In order to do this. 325 dyes, prepared by General dentists in Tehran, were collected from 10 laboratories. All dyes wore trimmed at the area below the finishing line and then were scanned (Genius Color page- FIR 6) buccoiingualiy and mesiodistaily. Convergence angle of dyes were also measured with Adobe Photoshop (5.0) software. Data were analyzed by variance analysis test and 1- student bv the help of SPSS software. Results showed that the average convergence angle ranged from 16.18+8.34 to 35.1 8~10.38 which belonged to maxillary canine and mandibular molars, respectively, and the measured convergence angle is more than the ideal value of 10-16 degrees. Dyes of the madibular molars were ma"illar" convergent. These conclusions are helpful for professors, dentistry students and dentists, and arc an indicative of the practice quality of General practitioners in Tehran. Due to the fact that a convergence angle, more than the allowed limitation, endangers retention, resistance and marginal integrity of the restoration, paying attention to the principles of tooth preparation and proper application of instruments and dental cements, can progress fwed restorations quality.
H. Razmi , A . Yousefi ,
Volume 16, Issue 3 (5-2003)
Abstract
Statement of Problem: The goal of a successful endodontic surgery is to establish an adequate seal in apical region. Therefore during surgery, root-end resection is essential for an appropriate situation and proper access.
Purpose: The aim of this study was to determine the most appropriate root-end resection angle to establish adequate apical seal in periapical surgery
Materials and Methods: Forty-five intact extracted human maxillary central incisors were randomly divided into three 15-tooth groups. The root canals were instrumented and then obturated using lateral condensation technique. AM roots were resected at 3mm from apical portion. Angles of root resection for each group were 0, 30 and 45 degrees. Then all teeth surfaces, except the cut ones, were covered with nail polish and immersed in methylen blue for 7 days. After 7 days, nail polish was removed from the surfaces and samples were split in buccolingual direction. Then, dye penetration (mm) was measured using a stereozoom microscope (Loupe) [X4 magnification] and eye lens. In order to analyze the data, unilateral variance analysis was used.
Results: The values of dye penetration were: 7.23±3.34 (0°), 8.46±3.01(30°) and 9.74±4.11 (45°). There
was no significant difference between three groups (P>0.05).
Conclusion: It is suggested that the angle of root-end resection put a limited effect on apical seal if retrograde cavity depth is increased.
Mr. Sharifian , P. Motahhari , S. Shahsia ,
Volume 19, Issue 2 (5-2006)
Abstract
Background and Aim: Achieving appropriate seal in canal obturation is the main goal of endodontic therapy. However, in some cases, it can not be obtained by non-surgical procedures alone. Retrograde surgery is one of the most common procedures in endodontics. Apical seal improvement can be obtained by root end filling and decreasing the root end resection angle (bevel angle). The aim of this study was to investigate the role of bevel angle on apical microleakage following the use of amalgam and MTA as root end filling materials.
Materials and Methods: In this experimental study, 128 extracted human teeth were instrumented and obturated by lateral condensation technique. The teeth were divided into two groups and the apical root resection was performed by high speed fissure bur (one group perpendicular to the long axis of the teeth and the other 45 to the long axis. The 3 mm root end cavity was prepared by ultrasonic device. Each group was divided into two subgroups: One filled with amalgam and the other with MTA. Teeth were incubated for 72 h, covered by two layers of nail polish (except for apical 3mm) and submerged in methylene blue for 48 h. Teeth were washed under tap water and mesiodistally dissected by low speed disc. Dye penetration was evaluated by stereomicroscope. Data were analysed by two way ANOVA and Tukey tests with p<0.05 as the limit of significance.
Results: The results showed that retrofill material type had a significant effect on microleakage and MTA was superior to amalgam in this respect. Bevel angle failed to show any significant effect on apical microleakage.
Conclusion: Based on the results of this study, it seems that the use of MTA instead of amalgam in clinical practice can improve the success rate of endodontic surgery whereas the bevel angle can be determined based on the status of each individual case However, increasing the bevel angle seems to increase microleakage due to exposure of more dentinal tubules.
H. Dorriz , R. Afzalifar , B. Afzalifar ,
Volume 20, Issue 3 (6-2007)
Abstract
Background and Aim: As central incisors have a prominent role in esthetics, appropriate preparation, considering natural tooth anatomy and proper planes have always been considered. The aim of this study was to determine the number of planes in labial surface of maxillary central incisors using image processing and mathematical analysis.
Materials and Methods: This pilot study was performed on 32 intact maxillary central incisors in dental students of Tehran university of medical sciences. Photographs were taken from profile view of each tooth by a digital camera. Images were processed and number of planes was obtained using SigmaScan Pro. version 5.00 software and a customized program. Data were analyzed by t-test and regression tests with p<0.05 as the level of significance.
Results: 96.9% of central incisors had three planes and 3.1% had two planes in labial surface. The angle between middle-cervical and middle-incisal planes showed statistically significant difference (p< 0.01).
Conclusion: Based on the results of this study, a few percentage of maxillary central incisors had two planes and most of them had three planes in their labial surfaces. Thus, considering three planes for restoring maxillary central teeth is closer to principles of tooth preparation and esthetics.
J. Chalipa, Mh. Hosseini, Mk . Hosseinian Serajelou, A. Khorshidian,
Volume 23, Issue 1 (6-2010)
Abstract
Background and Aims: One of the common human evolutionary anomalies is dental Missing. Evolution of dental system is toward deduction of teeth number. The Missing of third molar is interesting subject for dentists and genetic researches because of its variety in different races. Consideration of bilateral effect of third molar Missing with jaw relation is an important subject. The aim of this study was to evaluate the third molar missing in Cl I and Cl II skeletal (without rotation) and comparison of them together.
Materials and Methods: The patients of the orthodontic department of school of Dentistry (Tehran University of Medical Sciences) were analyzed. About 121 patients had Cl I and 60 patients had ClI jaw relation. This relation identified based on cephalometric lateral radiographic ANB corner angle. Patient who had rotation in maxilla or mandible based on SN-Go Gn angle were excluded. The incidence of third molars agenesis in individual dentition quadrants, upper and lower jaw and right and left side of dentition was examined from panoramic radiography. AChi-square test was used for statistical analysis of data.
Results: Missing of one or more third molar in skeletal Cl I and Cl II was 43% and 33.3%, respectively. Missing of one or more third molar in Cl II was fewer than Cl I, but no statistically significant differences were seen between them.
Conclusion: There was not a direct relationship between jaw relation and third molar Missing.
Mohsen Shirazi, Armina Mellat, Behzad Salari,
Volume 29, Issue 3 (10-2016)
Abstract
Background and Aims: In the field of orthodontics, gaining comprehensive information around dento-skeletal complex is necessary to choose the best treatment plan for each patient. The aim of this study was to investigate the linear and angular parameters in panoramic radiographs to find a path to correlate transvers to sagittal dimensions.
Materials and Methods: Total number of sixty two, 8-14 years old children who sought for orthodontic therapy were selected (32 skeletal Class III and 30 skeletal Class I). They were exposed to x-ray to obtain the panoramic and lateral views in a controlled condition. Various linear and angular parameters were measured after tracing the landmarks on the panoramic radiograph. Data were obtained and analyzed using T-test. The level of significance was set at 0.05 (P<0.05).
Results: Linear parameters of Co-Co, Go-Go and PTM-PTM were significantly lower in class III patients than class I ones (P=0.04, 0.04, 0.02, respectively). The ramus width value was also lower in class III patients. Angular parameters of Me˄ and N˄ also showed the same results (P<0.001). Go˄ angle was significantly lower in the class I than class III patients (P=0.002, 0.007).
Conclusion: Some traceable linear and angular parameters were found in the panoramic radiographs which had the potential to correlate the transverse with sagittal dimension.
Mehrafruz Daneshian, Kianoosh Malekzadeh, Masoomeh Afsa,
Volume 35, Issue 0 (5-2022)
Abstract
Background and Aims: Achieving non-invasive methods for the proper detection of secondary caries adjacent to dental restorations has a great importance. As alterations in horizontal and vertical angles of X-ray beam would affect the detection of dental caries on radiographs, this study was designed to evaluate the effect of changing the horizontal angle of X- ray on detection of dental caries adjacent to class II amalgam restorations in posterior teeth on periapical radiographs.
Materials and Methods: In this in vitro study, artificial carious lesions were prepared in axial walls of the amalgam restoration cavities in interproximal surfaces of 27 human extracted premolar teeth. Periapical radiographies with different horizontal X- ray angles were obtained, observed, and rated by 5 maxillofacial radiologists for detection of carious lesions. For each observer, the sensitivity, specificity, accuracy, PPV, and NPV of radiographs in the individual horizontal angles were calculated and compared by nonparametric Kruskal Wallis test. Interobserver agreement was assessed by fleiss’ kappa coefficient.
Results: The highest accuracy of periapical radiographs for the detection of secondary caries of mesial dental surfaces was in 5-degree of mesial and distal X- ray angle (86.66%) and for the distal dental surfaces was allocated to 10-degree of distal X- ray angle (85.90%). Also, there was a significant difference in the accuracy between different horizontal angles (mesial and distal 0, 5, 10, 15-degree) (P=0.01). The higher agreement between observers in detecting mesial surface caries was in 10-degree of distal angle (0.86) and in detecting distal caries was in 5-degree of distal angle (0.89).
Conclusion: In the case of doubt in the existence of recurrent caries in the interproximal tooth surface, if the carious lesion is not visible on standard radiographic image with direct angle of X- ray, A 5- 10 degree of x- ray horizontal angle can improve the detection of secondary caries under amalgam restorations in interproximal dental surfaces.
