Iranian Journal of Orthodontics
Volume:3 Issue: 1, Jan 2008

The development of human dentition from adolescence to adulthood has been the subject of extensive stud by numerous dentists, orthodontists and other experts in the past. In recent years, substantial effort has been evident in the field of mathematical analysis of the dental arch curve, particularly of children from varied age groups and diverse ethnic and national origins. The proper care and development of the primary dentition into permanent dentition is of major importance and the dental arch curvature, whose study has been related intimately by a growing number of dentists and orthodontists to the prospective achievement of ideal occlusion and normal permanent dentition, has cluded a proper definition of form and shape. Authors have put forth mathematical models to describe the teeth arch curve in humans. Some have imagined it as a parabola, ellipse or conic while others have viewed die same as a cubic SP-Line. Still others have viewed the beta function as best describing the actual shape of the dental arch curve. Both finite mathematical functions as also polynomials ranging from 2nd to 6th order have been cited as appropriate definitions of the arch in various studies by eminent authors. Each model had advantages and disadvantages, but none could exactly define the shape of the human dental arch curvature and factor in its features like shape, spacing and symmetry/asymmetry, This paper presents key mathematical models and compares them through some secondary research study.

To analysis the effect of unilateral shortening (Asymmetric Length, AL type) vs. expansion of head-gear outer-bow (Asymmetric Expansion, AE type) in delivering unilateral distal force. In 36 situations, composed or different outer-bow shortening, expansion and different neck contour and position, the resultant distal force was analyzed. Applying an analysis described by Haack and Wienstein, the ratio by which the resultant distal force was divided between 2 terminal molars was calculated. In AL type head-gear a greater portion of force was delivered to contra-lateral terminal while in AE type headgear the ratio of force delivery between two molars could not be higher than 1.04 due to geometrical limitations. AL type head-gear is a predictable and effective way for asymmetric distal force delivery. The greater force will be received by the contra-lateral terminal to the shorter arm of the outer-bow. AE type is not suggested for distal force delivery due to its geometric limitation and relative ineffectiveness.

Determining the proximity between predictions performed  by Dolphin imaging software before and after the orthogonathic surgery with standard manual method.

twenty long face C1 III patients, that had been undergone surgery were selected and their cephalograms and study cast records, before treatment, before surgery and after surgery were evaluated. The outcome was predicted with Dolphin imaging software and with standard manual method before and after surgery.

Differences of the variables by the software prediction in the presurgical and postsurgical stages in comparison with standard prediction method were usually insignificant.

Dolphin imaging software (version 10.0) has a good accuracy for prediction of presurgical and postsurgical outcome of long face C1 III orthogonathic patients.

The appearance of osteoclasts is the first step in orthodontic tooth movement. During orthodontic force application, the periodontal ligament (PDL) undergoes hyalinization. This tissue damage prevents the tooth from moving until the adjacent bone and necrotic tissue are removed by osteoclasts. There is a range of forces that produce the maximum rate of tooth movement. The purpose of this study was to compare the effect of different orthodontic forces on osteoclast numbers. Forty rats were randomly divided to 4 experimental groups. Appliance exerted 25gr in light, 40gr in moderate and 60gr in heavy group. There was not any appliance in control group. Animals were sacrified after 14 days and tissue samples were prepared. The mesial and distal surfaces of first upper molar and adjacent alveolar bone were studied. Osteoclast numbers, cementoclast numbers, root length, root resorption, depth and length of resorptive cavities, PDL. width in coronal-middle-apical, apical and coronal inflammation, bone resorption, necrotic bone and tooth movement were evaluated. Mesial and distal surfaces were also compared. In menial osteoclast numbers, depth of resorptive cavities, bone resorption, necrotic bone, PDL width and in distal apical inflammation, bone resorption, necrotic bone and PDL width were significant. Tooth movement was significantly different between all groups. (P<0.05) This data suggest that osteoclasts numbers are increased when force is increased. The magnitude of the orthodontic force is believed to be an important factor, not only for the magnitude of the tooth movement but also for any tissue damage.

A successful orthodontic treatment depends on a variety of Factors such as patient cooperation. Prediction of patient cooperation could be helpful for anticipating problems that might arise during treatment and alleviating them before they can interfere with treatment. Thus the aim of present study was to determine the relationship between psychological factors and cooperation of orthodontic patients.

In this cross-sectional study, 48 Class I female fixed orthodontic patients (13-17 years old) were selected. For all patients Eyesenck questionnaires were completed and personality status of each patient for extroversion, neuroticism, psychoyicism and lie was determined. Patients' cooperation was also assessed through evaluating patients' folders in the first year after treatment using Orthodontic Patient Cooperation Scale. Finally, Spearman correlation test and t- test were used for statistical analysis.

The results of present study revealed that there exists a negative relationship between Extraversion (E), Neurosis (N) and Psychosis(P) traits of the Juvenile Eyesenck Personality Test(See Appendix) with patients' cooperation in the girls and a positive relationship between Lying trait(L) of the test and the cooperation. However, the results of Spearman correlation test showed there were no significant differences between patients' cooperation and PEN and L trails of the Juvenile Eyesenck Personality Test (p-value> 0.05).

Orthodontic patients' psychological features could not predict their cooperation exactly.

The aim of modem orthodontic treatments is to improve facial esthetics as well as dental occlusion and create an attractive smile. The purpose of the present study was to assess lip line in deep bite patients in comparison to the normal situation. Twenty young (18-24 years) females with anterior deep bite (vertical overlap of upper teeth was more than one third of lower teeth height) participated in this study. Two Standard photographs in frontal view were taken in rest position and posed smile. Incisor show was measured in these two gestures in photoshop program. Descriptive statistical methods were used to analyze data. The average incisor show in our deep bite patients was 76.5% of central tooth crown total height. In 35% of our patients less than 70% of the incisor height was exposed during posed smile, and in 75% of the cases incisor teeth were not seen in rest position. Incisor show was less than minimum level of smile attractiveness in 35% of deep bite patients and the incisors were not seen at rest in 75% of these patients.

Nasopharyngeal space is estimated from a point on the posterior part of the soft palate till the nearest point on the wall of the pharynx and the aim of the present study was to study the nasopharyngeal indices in nasal breathers with class I and III malocclusions. This was a descriptive analytical study done by the case - control method on 35 lateral cephalometries of patients with skeletal Class III malocclusion as the study group and 30 lateral cephalometries of patients with skeletal Class I malocclusion as the control group. The population under study included patients referring to the orthodontic clinic and their age range was between 10 and 20 years. The lateral cephalometric radiographies were traced and data was analyzed using coefficient relation and t test. The bony height of the nasopharyngeal space had a statistically significant positive relationship with the anterior facial height. The bony area of nasopharyngeal space had a significant positive relationship with the anterior and lower facial height. There was no significant difference between the bony dimensions of the nasopharyngeal space and nasopharyngeal and oropharyngeal airway of the two groups. There was no significant difference between nasopharyngeal area parameters in skeletal Class I and Ill malocclusion. In nasal breather with skeletal Class III malocclusion, dimensions of nasopharyngeal area have no significant effect on facial growth pattern.

The BSSO is an excellent operation for a mandibular setback. Beyond 7-8 mm of posterior repositioning of the mandible with a BSSO is difficult, and consideration should be given to an inverted L osteotomy or intraoral vertical ramus osteotomy. (IVRO) Currently the period of immobilization ranges between 7-21 days following the release of IMF, guiding elastics should be used to direct the mandible to maximal intercuspation. This study implied a 1 year follow- up on a group of 40 patients, who had undergone modified subcondylar osteotomy for mandibular setback. Relapse is measured as the distance from Sn perpendicular to Pog at the lateral cephalogram preoperative, one week, and one year postoperatively. Modified intra-oral subcondylar osteotomy with short term immobilization appeared to be a relatively safeeand reliable procedure.The mean skeletal horizontal relapse at Pog of the whole group, after one year was 0.6mm and neuro-senory disturbance (NSD) incidence alter 6 months was 2.5%.

Quality management in orthodontics is a complex issue which aims at providing high quality services to patients. Development of a well established quality control policy according to regional characteristics and socio-economic features of the consumers, is of great importance. However, there is also an inevitable need for careful supervision regarding the implementation of the quality control program. This study is to evaluate and improve standards in removable orthodontic treatment. Data was retrieved from students, patients, orthodontists and technicians filled the relevant fields of questionnaires. The patients were chosen from those who had passed their second follow up session. The following health service modules were assessed in the questionnaires: "The pre-admission phase for patients", "The pmcass of admission". "The treatment, the follow up and the retention phase", and "The laboratory". The results were analyzed in two categories; the patient related questions (clinic) including modules from entrance to dismissal and the technician related questions (appliance construction). The pattern of the answers in the first category was: 8.1% "Very poor", 12.7% "Poor', 32.5% "Moderate", 48.8% "Good" and 0% "Very good". The second category of questions yielded the following pattern of response: 16.1% voted "Very poor", 61.2% voted "Poor" and 12.6% voted "Moderate", 9.6% "Good" and 0% "Very good". In general, the majority of participants (38.4%) marked the answer choice "Good". Generally, the treatment provided for patients seemed to be of "good" standard. However, further attention has to be devoted to laboratory-related aspects of Orthodontic services.

The main goal of this study was to compare the effects of a differently designed functional appliance (R-appliance) with a bionator treated group in Class II Division I (C1 II Div I) cases. 22 patients (12 girls, 10 boys) treated with R-Appliance were selected as experimental group. Control group consisted of 22 patients (11 boys, 11 girls) treated with a bionator. All of the patients had a C1 II Div I malocclusion due to mandibular deficiency. Lateral cephalograms were analyzed at the beginning (T1, T 1) and the end of the study (T 2, T 2). Paired T-test showed that SNB significantly increased in both groups. The same test revealed that IMPA was reduced in the R-appliances treated group by 4.5°±3.5° (P<0.001) but it was increased by 1.9°±3.9° (P<0.03) in the bionator group. Analysis utilizing T-test showed that the inter group difference of IMPA was statistically significant (P<0.01). SNA showed an increase of 0.1°±1.6° (P<0.9) in the R-appliance treated group; while, it was decreased for 0.4°±0.9° (P<0.1) in the bionator treated group.
Both groups were successful in advancement of mandible; however, the R-appliance achieved this result without retroclination of the lower incisors.