Comparison of arch forms between Israeli and North American white populations.

INTRODUCTION: Identification of the dental arch form of the orthodontic patient is a key aspect for achieving a stable, functional, and esthetic dentition. Failure to customize preformed archwires with the patient's arch form might increase the probability of relapse and lead to an unnatural smile. The primary objective of this study was to identify the arch forms of Israeli subjects with dental normocclusion and malocclusions. The secondary objective was to clarify the morphologic differences between Israeli and North American white subjects with various malocclusions. METHODS: The sample included 134 Israeli (40 Class I, 61 Class II, and 33 Class III) and 160 North American (60 Class I, 50 Class II, and 50 Class III) subjects. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth based on mandibular tooth thickness data. Four linear and 2 proportional measurements were made. The dental arches were classified as square, ovoid, and tapered forms to determine and compare the frequency distributions between the 2 ethnic groups. RESULTS: The most frequent mandibular arch form of the Israeli group was found to be ovoid as opposed to tapered in the North American white group. The white population had statistically significant decreased arch widths and increased arch depths compared with the Israeli population. The analysis of the Israeli sample indicated that, as the malocclusion shifts from Class III through Class I to Class II, the weight of the arch form tends to shift from square and ovoid to ovoid and tapered. CONCLUSIONS: Our results suggest that, when treating Israeli patients, one should expect to use the preformed ovoid arch form orthodontic wires in a significant percentage of patients.

Comparison of common hard tissue cephalometric measurements between computed tomography 3D reconstruction and conventional 2D cephalometric images.

OBJECTIVE: To compare cephalostat two-dimensional (2D) measurements to 3D computed tomography (CT) measurements in order to determine the compatibility of CT landmarks identification for orthodontic purposes. MATERIALS AND METHODS: Ten human skulls were x-rayed in conventional lateral cephalogram and then scanned with spiral CT. Twenty-eight linear and angular cephalometric measurements were registered on the 2D lateral cephalogram and compared to the same measurement on the 3D CT scan. Significance of the results was determined by t-test for paired differences (P < .05). RESULTS: No difference was found between 2D and 3D images for linear or ratio measurements. As for the angular cephalometric measurements, only the sella turcica dependent measurements, showed significant difference between 2D and 3D. CONCLUSIONS: The compatibility of using most of the common orthodontic examined cephalometric measurements on 3D volume rendered image was proven except for the angular measurements that included sella anatomic landmark.

Measurement of friction forces between stainless steel wires and "reduced-friction" self-ligating brackets.

INTRODUCTION: In this study, we assessed the friction forces between various self-ligating brackets and stainless steel orthodontic wires, subjected to different shear and bending forces in the buccolingual plane. METHODS: Three kinds of self-ligating brackets and 2 kinds of ligated controls were tested in a newly developed in-vitro system. Friction was tested with stainless steel orthodontic wire in 3 deflection states. The Bonferroni multiple comparisons test was applied to evaluate intergroup differences (P <0.05). Wire samples were examined with a scanning electron microscope before and after sliding. RESULTS: The results showed significant intergroup differences in friction resistance in response to wire deflection. In nonzero buccolingual deflections, passive self-ligating brackets developed higher friction forces, comparable with those in the conventional elastic ligation control group. The control brackets with reduced friction ligature had considerably lower friction forces than any other group. The active self-ligating bracket ranked between the self-ligating brackets and the reduced friction ligature group. A tribologic survey showed substantial surface alterations among wire samples coupled with passive self-ligating brackets. CONCLUSIONS: In contrast to manufacturers' claims, this study illustrates that, in certain clinical situations, a firm passive bracket clip can have a negative influence on the wire-bracket frictional characteristics.

Early headgear effect on the eruption pattern of maxillary second molars.

OBJECTIVE: To test the hypothesis that the use of a combination headgear (HG) during the first phase of orthodontic treatment has no effect on the eruption pattern of the maxillary second permanent molars. MATERIALS AND METHODS: The records of the patients in a two-phase randomized clinical trial of early Class II treatment were utilized. The HG group comprised 47 patients, and the control (CON) group comprised 52 patients. The mean age of both groups was 9.4 years at the beginning of the clinical trial (T1). Cephalograms and panoramic views obtained at T1 and at the end of 15 months of phase I treatment or observation (T2) were utilized. The vertical and horizontal movements of the first and second upper molars (U6 and U7, respectively) were measured. The beginning of phase II (T3) and the end of phase II (T4) records were visually reviewed for follow-up of the eruption of the U7. RESULTS: The pattern of movement for the distal and vertical displacement of the U6 and U7 was significantly different in the HG and CON groups (P < .001). At the end of phase I, none of the U7 in either group were diagnosed as malposed or suspected for impaction. At the end of phase II, all but one U7 with a possible cystic lesion had erupted. CONCLUSIONS: The hypothesis is rejected. Forces exerted by combination headgear to the U6 in phase I have a distalizing effect and a transitory slowing down effect on the eruption of the U7 buds. These latter teeth always erupted except when pathology occurred.

Lip posture following debonding of labial appliances based on conventional profile photographs.

OBJECTIVE: To assess changes in lip posture following debonding of labial appliances on the basis of a new soft tissue analysis performed by computerized tools with the use of conventional nonstandardized profile photographic pictures. MATERIALS AND METHODS: Profile photographs of 33 patients were taken just before and just after debonding of labial brackets. Pictures were examined twice through custom-made analysis in which Viewbox software was used. The validity of this new analysis was assessed in a preliminary study. A reference line was constructed between the center of the tragus and the outer canthus. The point where this elongated line intersected with the profile was coined nasion-modified and served as the vertex point for angles used to evaluate the prominence of the lips. The final position of the lines was determined when they were tangent to the appropriate landmarks. Analysis of variance (ANOVA) and t-tests for paired differences were used. RESULTS: The reproducibility of this photoanalysis was confirmed in the preliminary study, in that no significant differences were found between measurements (P < .05). No statistically significant differences were noted in lip posture between pre-debonding and post-debonding pictures (P < .05). CONCLUSIONS: In keeping with the design of this study, soft tissue profile photoanalysis showed that the presence of bonded labial appliances had no effect on lip posture.