Biomedical subjects

Reza Sadat-Khonsari

Publications and source records attributed to Reza Sadat-Khonsari.

8 recordsLinked to original sources

PubMed2007

The third-order angle and the maxillary incisor's inclination to the NA line.

OBJECTIVE: To evaluate the relationship between the angular measurement data (incisor's long axis to NA line) and the third-order angle (TA) according to Andrews' description. MATERIALS AND METHODS: The materials in the study included the lateral radiographs and corresponding dental casts of 32 males and 35 females between 10 and 25 years of age, regardless of their skeletal and dental relationships. All subjects were white and none had undergone orthodontic therapy. Using lateral radiographs, upper and lower incisor angulations were assessed in reference to the NA line. These data were compared with third-order angles derived from direct dental cast measurements, which were performed using an incisor inclination recording appliance. RESULTS: The third-order angle measurements recorded from the dental casts were a mean of 16.2 degrees (SD = 5.3 degrees) smaller than the axial inclination according to the NA line. In this sample, there was a range of 42.7 degrees for the TA variable (mean = 5.6 degrees, SD = 9.73 degrees) and 47 degrees for the 1NA/deg variable (mean = 21.7 degrees, SD = 8.67 degrees). A highly significant correlation existed (r = 0.84) between Andrews' angle and the inclination estimated in reference to the NA line. CONCLUSION: Incisor inclination can be better estimated by recognizing the relationship between the torque angle and the axial inclination referred to the NA line. Third-order measurements using dental casts can offer a simple way to get an objective and rapid vision of the incisor's inclination.

Adolescent↗

PubMed2005

The retention catalogue: an instrument for quality management.

UNLABELLED: GOAL AND MATERIAL: We evaluated the clinical use of the "retention catalogue" employing a standardized questionnaire. RESULTS: Statistical evaluation of the standardized questionnaire demonstrated that the retention catalogue (RC) is an effective method in daily practice for orthodontists to convey patient information on the causes and prevention of relapses in crowding. CONCLUSIONS: Routine utilization of the retention catalogue is recommended. It both contributes to successful retention management and offers the orthodontist a certain degree of legal protection. CONCLUSIONS: Routine utilization of the retention catalogue is recommended. It both contributes to successful retention management and offers the orthodontist a certain degree of legal protection.

Germany↗

PubMed2004

Torque deformation characteristics of plastic brackets: a comparative study.

AIM: The purpose of this study was to compare the torque deformation characteristics of seven commercially available plastic brackets, both amongst each other and with stainless steel brackets. MATERIAL AND METHODS: Ten brackets each of (1) pure polycarbonate, (2) ceramic reinforced polycarbonate, (3) fiberglass reinforced polycarbonate, (4) ceramic reinforced polycarbonate with metal slot, (5) fiberglass reinforced polycarbonate with metal slot, (6) polyurethane, and (7) polyurethane with metal slot were exposed to torsion in a torquemeter, following an aging process according to ISO 10477. Ten stainless steel brackets served as a control group. Torsion was applied continuously using a material testing machine (Zwick Z2.5, Zwick Materialprüfung, Ulm, Germany). RESULTS: The results showed within the group of plastic brackets that metal slot reinforced brackets were subject to the lowest degree of deformation, followed by the brackets made of pure polyurethane, pure polycarbonate and fiberglass reinforced polycarbonate. The ceramic reinforced polycarbonate brackets showed the highest deformation under torque stress. The plastic deformation of the ceramic reinforced, fiberglass reinforced and pure polycarbonate brackets started even in the recommended torque range of 10-20 Nmm. The additional ceramic and fiberglass in the plastic brackets investigated in this study did not improve the torque stability of the polycarbonate brackets. The pure polyurethane brackets showed no significant difference from the pure polycarbonate brackets at the moment of 15 Nmm which is the optimal torque for a maxillary incisor. CONCLUSION: A comparison with the stainless steel brackets illustrated that plastic brackets are suited for clinical application only if they have a metal slot.

Biomechanical Phenomena↗

PubMed2004

Temporomandibular joint dysfunction in Marfan syndrome.

OBJECTIVE: The aim of this study was to examine the prevalence of signs and symptoms of temporomandibular joint (TMJ) dysfunction in persons with Marfan syndrome. STUDY DESIGN: A questionnaire was distributed to 350 patients with Marfan syndrome. Twenty-one patients were additionally subjected to a clinical examination and magnetic resonance imaging (MRI) of the TMJ. RESULTS: The prevalence of symptoms of TMJ dysfunction was 51.6% (n=145), with 24.2 % (n=68) indicating symptoms of subluxation, and 34.9% (n=98) of the patients already undergoing medical treatment for their TMJ problems. Anterior disc displacement with and without reduction was observed in 17 of the examined patients (81.0%), with 4 of these patients additionally showing osteoarthrosis of the affected temporomandibular joints. CONCLUSION: TMJ dysfunction appears to be an important aspect in Marfan syndrome.

Adult↗

PubMed2003

The helical axis of the mandible during the opening and closing movement of the mouth.

BACKGROUND: The movement of a rigid body through space may be comprehensively described by constructing a "finite helical axis" (FHA). The rigid body carries out a rotation around this axis for discrete periods of time while at the same time moving along this axis. MATERIAL AND METHODS: The free opening and closing movement of the mouth was registered in eight asymptomatic test persons, using the CADIAX electronic axiography system (GAMMA-DENTAL, Klosterneuburg, Austria). Subsequently, the position of the FHA in space, the angle of rotation around this axis, and the amount of translation along the FHA were determined for each subject, using the coordinates of the measuring styluses. RESULTS: During the initial phase of the mouth-opening movement, the FHAs were near the condyle. Over the course of the opening movement, they moved toward downward backward, downward and downward forward, and finally to forward upward toward the condyle upon reaching maximum mouth opening. During the closing movement, the FHAs shifted back in the reverse direction. During both the opening and the closing movement, there was a slight translational movement along the FHAs, which provided an indication of mandibular deviation.

Diagnosis, Computer-Assisted↗

PubMed2003

Mandibular instantaneous centers of rotation in patients with and without temporomandibular dysfunction.

PATIENTS AND METHODS: The free opening movement of the mandible was examined in 30 patients with and without dysfunctions, using the CADIAX electronic axiography system. All patients in the diseased group showed dysfunctions in the left temporomandibular joint. Half of the 20 asymptomatic patients were skeletal Class II, the other half skeletal Class III. Based on the data collected for the left temporomandibular joint, the movement of the mandible during the mouth-opening movement in the sagittal and vertical planes was described as the pathway over time of the various instantaneous centers of rotation (ICR), using physico-biomechanical factors. RESULTS AND CONCLUSION: It emerged that the ICR path in the patients with dysfunctions was irregular with erratic changes of direction. A harmonious ICR path beginning near the condyle was typical of the healthy group; as the mouth opened, the path moved toward downward backward and finally shifted toward forward and forward upward. Therefore, such an ICR path pattern can be used as an indicator in detecting dysfunctions.

Adolescent↗

PubMed2003

In vitro study on the fatigue limit of single-lap joints.

Lasting adhesion between attachment and tooth is an essential prerequisite for all adhesive techniques in dentistry. However, the maximum static fatigue load is only one material-related parameter for the quality of this adhesion. Another parameter is the dynamic loading capacity of a bonded joint, which was determined in the present study for Dual adhesive resin by means of fatigue testing. This revealed a significant correlation between the recorded static and dynamic fatigue load and the gap width, which varied between 0.01 mm, 0.15 mm and 0.5 mm in the experimental setup. At 18.8 MPa, the median gap width of 0.15 mm yielded the highest static resistance, with a dynamic resistance 15% below this figure. Both the smaller and the larger gap showed significantly lower static fracture strengths (0.01 mm: 13.6 MPa; 0.5 mm: 13.7 MPa), whereas a dynamic load on the 0.01 mm bond, in contrast to the 0.5 mm bond, led to only a 5% reduction in bonding strength.

Biomechanical Phenomena↗

PubMed2002

Results of transplanting developing third molars as part of orthodontic space management. Part 1: clinical and radiographic results.

PATIENTS AND METHOD: The aim of the present study was to contribute to a more accurate indication and better integration of developing third molar transplantation into orthodontic space management, using the results gleaned from the authors' own pool of patients. For this purpose, a clinical and radiographic examination of 61 transplanted developing molars in 57 patients was carried out after an average of 3.3 years. RESULTS: The overall success rate was 85%. Failure was due in 10% of cases to impaired periodontal healing (inflammatory root resorption, ankylosis, or increased pocket probing depths) and in 5% of cases to insufficient or arrested postoperative root development accompanied by increased transplant mobility. The incidence of postoperative cessation of further root development was significantly higher (p = 0.011) in transplants at early developmental stages, which also had a negative impact on the final root length, the crown-root ratio and the mobility values of these transplants. CONCLUSIONS: The transplantation of developing third molars should be given stronger consideration in treatment plans for orthodontic space management although it represents a real alternative to orthodontic space closure only in exceptional cases. However, unlike implantological or prosthodontic treatment, it offers an opportunity to replace a missing or non-retainable tooth with a patient's own vital and fully functional tooth, provided the appropriate transplant is selected.

Adolescent↗