Iranian Journal of Orthodontics
Volume:1 Issue: 1, Mar 2006

The main object of this study was to find out the correlation between types of malocclusion and temporomandibular joint (TMJ) disorders among students.

This study was descriptive and cross-sectional in which 425 persons were examined. From this number, 308 persons were male, and 117 were female. All samples were students of Mashhad University of Medical and Dental Sciences. The range in age was 19 to 32 years with a mean of 26.1 years. Samples were selected randomly. SPSS soft ware was used and statistic evaluation was done.

The correlation between malocclusion and TMJ discomfort at a level of ?=0.05 was not signifi-cant. The highest level of correlation existed between TMDs and CI II malocclusion. The rate of TMJ dis-comfort in various types of malocclusion was respectively as follow: CI II>CI I>CI III. The correlation between TMJ discomfort and head, neck and back pain was meaningful (P=0.0298). The rate of women with TMJ discomfort to men was 1.6: 1. Most patients with TMJ discomfort complained of joint noises and a small number of them remarked symptoms such as pain, jaw opening limitation, and other symptoms of the disorder. Joint noises were mainly in the form of clicking. TMJ discomfort accompanied by gastric dis-order (generally speaking) was meaningful (P=0.0214).

From this study it was concluded that there was no significant correlation between maloc-clusion and TMJ discomfort at a level of α=0.05 among students. The highest level of correlation, which still was not statistically significant, existed between TMDs and CI II malocclusion. The correlation between TMJ discomfort and head, neck and back pain was significant. It is suggested that specific studies be done to clear out the exact relation between gastric disorder and TMJ discomfort.

The long-term outcome and clinical results of gaparthro plasty used for the treatment of condylar ankylosis of the mandible in children with application of postoperative activator appliances and costochondral rib graft are evaluated and compared.

A nonrandomized, retrospective clinical study of 10 cases of condylar ankylosis (18 Joints) of the mandible surgically treated during a 12 year period from 1990 to 2002 was performed. Four patients were treated by condylectomy and interpositional Flap and Six patients were treated by condylectomy and Immediate costachondral rib grafts. The First group underwent long-term postoperative therapy using removable activator appliances. Casts, radiographs, photographs, computed tomography (CT) Scans, were Used post surgically to evaluate rib graft, condylar growth and function, occlusion, and Facial and condylar symmetry.

Symmetry, arch coordination, correction of occlusal canting, mandibular deviation, facial growth , and prevention of reandkylosis were obtained and better controlled in those cases that cnderwent long-tern orthodontic activator therapy post operatively and were followed closely.

Children with long-standing condylar ankylosis of the mandible and its resultant facial asymmetry and occlusal canting (Secondry to a non functional joint and Maxillary compensation) treated with condylectomy and interpositional flap treated more favorably when activators were used postsurgically. The patients that failed to comply with or continue activator therapy postsurgically developed complications relating to mandibular deviation , occlusal dysharmony, asymmetry and rankylosis of the temporo mandibular joint (TMJ).

Several bracket characteristics are now in market. Preformed archwires are used without frequent need to add bends. V-bends are used in many situations. This bend as a basic maneuver is assessed thoroughly in this study. Finite Element Method (FEM) was selected to analyze the situation. A 3D model of two maxillary central incisors with their supporting structures and an archwire were modeled. A V-bend in different positions relative to the teeth was defined. Forces produced were monitored. Center V-bend (a/L=1/2) produced two moments in opposite direction. Moving towards one tooth added vertical forces in opposite direction. At a/L ˜˷115, intrusive movement was noticed; while signs of intrusion and change in angulation was detected at 1/10< a/L<1/5. When a/L reached 0.42/6.408 same direction of moments were shown. V-bend force system is quite sensitive to its position.

Tanaka and Johnston have offered a very simple method for estimating mesio-distal witdh of unerupted canines and premolars; But it seems that these estimations are not appropriate for Iranian population. In this investigation we've tried to offer a new formula to estimate the width of unerupted teeth in Iranians.
In this study we measured the size of premolars and canins on 400 dental casts and did a regression analysis to find any correlation between the size of these teeth and four lower incisors.
We found that using Tanaka and Johnston analysis in Iranian children, unerupted teeth estimated wider than actual size.This study showed that there was a strong correlation between the width of lower incisors and unerupted canine and premolars of both jaws in Iranian population.
As we found Tanaka and Johnson's formula will estimate canines and premolars wider and a new formula is offered for Iranian population.

There are several studies to evaluate lento-skeletal changes after treatment of skeletal class 2 malocclusion with Dr Farmand's functional appliance but in non of them facial harmony has been considered. The purpose of the present study is evaluation of facial harmony in addition to dentoskeletal changes after treatment with Dr Farmand 's functional appliance. Initial and final cephalograms of eighteen treated skeletal class 2 div 1 patients have been selected. All of them had been treated with Farmand's appliance before termination of growth spurt. Each cephalogram was separately traced two times. Means of before and after treatment data were compared with paired t-test. Skeletal class 2 relationship has been successfully corrected through decreasing ANB angle (1.88±1.75, p=0.00), 66 and angle of convexity(-1.47±1.21 , p=0.00), and Also dental changes (upper incisor retrusion and lower incisor protrusion) were occurred (decrease of U1 to SN was -4.77±4.71 , p=0.00 and increase in IMPA was +3.93±2.87 ,p=0.00). Soft tissue changes involved retrusion of upper lip to E-line (-2.86±1.88, p=0.00) and decrease of upper sulcus dept (-1.55±2.04, p=0.005) and lower sulcus dept (-2.44±1.85 ,p=0.00) which played an important role in improvement of facial harmony . Lower lip was placed more anteriorly relative to H-line (1.37±1.48 p=0.001) which is not desirable in profile harmony. Dr Farmand's functional appliance is effective in treating skeletal class 2 patients by producing skeletal as well as dental improvement. Soft tissue harmony also is improved but final position of lower lip must be regarded more carefully.

This study was designed to compare the tooth size discrepancy as a factor of skeletal mal-occlusion in orthodontic patient population of Shiraz.

The study employed the pretreatment models of 200 patients, which were selected through a random available sampling method. The mesiodistal dimensions of teeth were measured by digital electron calipers (accurate to 0.01 mm) and the Bolton indices were determined. The study population was divided into four malocclusion groups according to Angle classification (Class I, Class II Div 1, Class II Div 2 and Class III). The data were analyzed using ANOVA and Duncan tests by SPSS software and the level of significance was p<0.05.

The mean anterior ratio (79.01) of the total malocclusion group had a statistically significant difference with that of Bolton (77.2) but no significant difference was found for the overall ratio. The posterior and overall ratios of Class III malocclusion group were statistically greater than the other malocclusion groups. However, regarding the anterior ratio, the Class Ill group had a greater mean than Class II with no difference with Class I malocclusion group.

Comparing the two types of Class II malocclusion for ratios, no significant differences were observed.

Mesiodens is the most common supernumerary tooth occurring in 0.15% to 1.9% of The population. A racial variation is believed in the prevalence of supernumeraries. The purpose of This crosssectional study was to determine the prevalence of mesiodens.
2687 Iranian children 6-9 years old were selected and peripcal radiographs were taken.
The general prevalence of mesiodens was found to be 1.6% (1.11 , 2.08). Males showed a higher prevalence of mesiodens than that of females; 5:10.
A maxillary occlusal radiograph is highly recommended to make clear The presence or absence of supernumerary teeth.

The purpose of this review was to address the question whether mandibular distractionostegenesis (DO) has any effect on temporomandibular joint (TMJ). A literature survey from the pub Med database used the medical subject heading terms osteodistraction, T.M.J and 13 articles written in English were obtained. mandibular DO may accompany with some resorption & remodeling of TMJ but apparently if correctly used produces less TMJ problems compared with conventional mandibular osteotomies and even according to some studies, It is beneficial to structure and position of TMJ. This technique has been proposed for advancement of mandible in patients with TMJ problem and for ramus lengthening for prevention of relaps and TMJ problems. Mandibular Do can be a valuable technique for reconstruction of ramus and condyle in severe mandibular deformities such as TMJ ankylosis and hemifacial microsomia. Transverse distraction of mandible may accompany with TMJ problems and should be used cautiously.

Everyday because of developing new materials and techniques, more adults become interested in orthodontic treatments. Soft positioner and its new generation in the name of Invisalign System is an example. The present case report was designed to study the effects of soft elastic foils as serial aligners on treat-ing the mild to moderate crowding.
Three teenage patients with crowding not more than 6 millimeters were select-ed. After the preparation of orthodontic diagnostic records and filling the periodontal chart, manual teeth setup was carried out on working casts with a maximum 0.5 millimeter displacement. Aligners were made up of bioplast foils. The appliance was worn by patient full time for at least 2 weeks. Then the new one was made and this procedure was continued until complete tooth alignment. The last aligner was used as retainer for three months later. These variables were evaluated after treatment : dental alignment , over jet . overbite, inclination of upper & lower incisors, lips relation to E line, mandibular plan angle, clicking in TMJ, periodontal status and tooth pain. Active treatment period lasted between 3-5 months.
Anterior crowding was completely corrected in all patients. Protrusion of upper & lower incisors were seen in lateral cephalograms. Overbite, mandibular plan angle and lips relation to E line did not change. Improvement of periodontal status were recorded in all patients. Low to moderate toothache was reported during the first 2 days .
Mild to moderate crowding could be corrected successfully with soft elastic foils (Serial Aligners) without deleterious effects on TMJ and periodontium however manual tooth setup was time consuming. (IJO 2006; 1: 75 - 78)