Overjet at the Anterior and Posterior Segments: Three-Dimensional Analysis of Arch Coordination

Objectives: To compare the amounts of anatomical overjet measured from facial axis (FA) points with the amounts of bracket overjet measured from bracket slot center (BSC) points. Materials and Methods: The samples consisted of 27 subjects with normal occlusion whose models were fabricated with a three-dimensional (3D) scanner and the 3Txer program (Orapix Co Ltd, Seoul, Korea). 3D virtual brackets (0.022″ Slot, MBT setup, 3M Unitek, Monrovia, Calif) constructed with a 3D-CAD program were placed on an FA point with the 3Txer program. The arch dimension and the amounts of overjet from FA and BSC points were measured. Paired t-tests and analysis of variance (ANOVA) tests were used for statistical analysis. Results: No significant difference in arch width and depth was observed between FA and BSC points. Although the amounts of overjet measured from FA points showed homogenous distribution, a tendency to decrease from the anterior segment (2.3 mm) to the posterior one (2.0 mm) was noted. However, the amounts of overjet measured from BSC points were variable, especially in the premolar and molar areas. Significant discrepancies in the amounts of overjet in most of the areas between FA and BSC points (more than P < .05), except the lower second premolar and second molar areas, were reported, even though insets and offsets are part of the prescription for the base of straight-wire appliance (SWA) brackets. Conclusions: The hypotheses that the amount of overjet measured from BSC points was 3 mm through the whole segments and that distribution of the amounts of overjet from BSC points was the same as that from FA points were rejected

Effect of frequent laser irradiation on orthodontic pain A single-blind randomized clinical trial

Objective: To analyze the effect of low-level laser therapy (LLLT) on perception of pain after separator placement and compare it with perceptions of control and placebo groups using a frequent irradiation protocol. Materials and Methods: Eighty-eight patients were randomly allocated to a laser group, a light-emitting diode (LED) placebo group, or a control group. Elastomeric separators were placed on the first molars. In the laser and LED groups, first molars were irradiated for 30 seconds every 12 hours for 1 week using a portable device. Pain was marked on a visual analog scale at predetermined intervals. Repeated measure analysis of variance was performed for statistical analysis. Results: The pain scores of the laser group were significantly lower than those of the control group up to 1 day. The pain scores in the LED group were not significantly different from those of the laser group during the first 6 hours. After that point, the pain scores of the LED group were not significantly different from those of the control. Conclusions: Frequent LLLT decreased the perception of pain to a nonsignificant level throughout the week after separator placement, compared with pain perception in the placebo and control groups. Therefore, LLLT might be an effective method of reducing orthodontic pain.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000004298/6SEQ:6PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000004298ADJUST_YN:YEMP_ID:A072100DEPT_CD:852CITE_RATE:1.184FILENAME:ao_july,_laser.pdfDEPT_NM:치의과학과SCOPUS_YN:YCONFIRM:

Comparison of arch forms between Egyptian and North American white populations

Introduction: The aim of this study was to evaluate the morphologic differences in the mandibular arches of Egyptian and North American white subjects. Methods: The sample included 94 Egyptian subjects (35 Class I, 32 Class II, and 27 Class III) and 92 white subjects (37 Class I, 29 Class II, and 26 Class III). The subjects were grouped according to arch form types (tapered, ovoid, and square) to compare their frequency distribution between ethnic groups in each Angle classification. The most facial portions of 13 proximal contact areas were digitized on scanned images of mandibular casts to estimate the corresponding clinical bracket point for each tooth. Four linear and 2 proportional measurements were taken. Results: In comparing arch dimensions, inter-molar width was narrower in Egyptians than in the whites (P = 0.001). There was an even frequency distribution of the 3 arch forms in the Egyptian group. On the other hand, the most frequent arch form was ovoid followed by tapered and square in the white group; the square arch form was significantly less frequent than the tapered and ovoid arch forms (P = 0.029). Conclusions: The arch forms of Egyptians are narrower than those of whites. The distribution of the arch form types in Egyptians showed similar frequency, but the square arch form was less frequent in whites. It is recommended to select narrower archwires from the available variations to suit many Egyptian patients. (Am J Orthod Dentofacial Orthop 2011;139:e245-e252)Partly funded by Catholic University of Korea, the alumni fund of the Department of Dentistry, and the Graduate School of Clinical Dental Science.

Effects of alveolar bone displacement with segmental osteotomy: micro-CT and histomorphometric analysis in rats

Abstract The purpose of this study was to evaluate the effects of segmental osteotomy on the blood vessels and osteoclasts in rats using micro-computed tomography (micro-CT) and histomorphometric analysis. After segmental osteotomy was performed around the maxillary first molars of 36 male Sprague-Dawley rats (n = 72), the samples were divided into a control group (no displacement), 0.5 D group (0.5 mm buccal displacement) and 1.0 D group (1.0 mm buccal displacement) (n = 24/group). At 1, 2, 4 and 8 weeks after surgery, changes in the blood vessel volume were investigated using micro-CT with perfusion of radiopaque silicone rubber. Tartrate-resistant acid phosphatase (TRAP) staining was used for histomorphometric analysis. Two-way repeated measures analysis of variance (rmANOVA) was performed to compare the volume of blood vessels and number of TRAP-positive osteoclasts among the groups. Regarding blood vessel volume, the displacement groups had no significant effects, while the time points had significant effects (p = 0.014). The blood vessel volume at 1 week was significantly smaller than that at 2, 4, and 8 weeks (p = 0.004, p = 0.026, and p = 0.005, respectively). Regarding TRAP cell count, the displacement groups had no significant effects, while the time points had significant effects (p < 0.001). The number of TRAP-positive osteoclasts at 8 weeks was significantly smaller than that at 1, 2, and 4 weeks (p < 0.001, p < 0.001, and p = 0.002, respectively), and the count at 4 weeks was smaller than that at 1 week (p = 0.011). Therefore, a regional osteoclast-related acceleratory phenomenon was maintained until 4 weeks after surgery

Evaluation of dental and basal arch forms using cone-beam CT and 3D virtual models of normal occlusion

Objectives: To evaluate the relationship between the mandibular dental and basal arches using CBCT, and to assess the correlation between basal arch dimensions derived from CBCT and 3-dimensional (3D) virtual models in a cohort sample exhibiting normal occlusions. Methods: The facial axis (FA) and root centre (RC) points of mandibular teeth were identified on 32 CBCT images. FA and WALA points were digitised on 3D models of 28 mandibular casts from the same sample. The relationships between dental and basal arch dimensions, and between the two basal depth dimensions derived from RC and WALA points were statistically assessed by Pearsons correlation. Results: Strong correlations were found between dental and basal intercanine and intermolar arch widths. Also, the basal intercanine width showed a moderate correlation with dental intermolar width and depth. The basal intercanine and intermolar widths measured on 3D models showed moderate correlations with those measurements on CBCT, whereas the basal canine and molar depths showed no correlations. Conclusions: The dental and basal anterior and posterior arch widths were strongly correlated in normal occlusion. No correlations were found between the arch depths measured from WALA points and RC points. Hence, RC points may represent more useable landmarks compared to WALA points in the evaluation of basal arch forms. It is recommended that the relationship between the dental and basal arches is evaluated during treatment planning in order to improve arch co-ordination.OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000004298/5SEQ:5PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000004298ADJUST_YN:NEMP_ID:A072100DEPT_CD:852CITE_RATE:.281FILENAME:국윤아-백승학-호주-2013-archform-cbct.pdfDEPT_NM:치의과학과SCOPUS_YN:YCONFIRM:

Three-dimensional evaluation of the relationship between dental and basal arch forms in normal occlusion

Objective: The purposes of this study were to evaluate the relationship between the dental and basal arch forms; to analyze their differences in the tapered, ovoid, and square arch forms in normal occlusion by using three-dimensional (3D) virtual models; and to test the hypothesis that the overjet and max-illomandibular basal arch width difference have a significantly positive correlation. Methods: Seventy-seven normal occlusion plaster casts were examined by 3D scanning. Facial axis (FA) and WALA points were digitized using the Rapidform 2006 software. The dimensions of the dental and basal arches and the over-jet were measured. The samples were classified into 3 groups according to arch forms: tapered (n = 20), ovoid (n = 20), and square (n = 37). Analysis of variance (ANOVA) was used to compare the dental and basal arch dimensions. The Pearson correlation coefficients between the intercanine as well as the inter-molar widths at the FA and WALA points were calculated. Results: With regard to the basal arch dimensions, the tapered arch form showed a larger mandibular intermolar depth than the ovoid. Strong correlations were noted between the basal and dental intermolar widths in both the upper and lower arches (r = 0.83 and 0.85, respectively). Moderate correlation was found between the upper and lower intercanine widths (r = 0.65 and 0.48, respectively). Conclusions: The 3 dental arch form groups differed only in some dimensions of the skeletal arch. Moderate correlations were found between the basal and dental inter-canine widths. These findings suggest that the basal arch may not be a principle factor in determining the dental arch form.This study was supported in part by the Alumni Fund of the Department of Dentistry and Graduate School of Clinical Dental Science, Catholic University of Kore

Comparison of overjet among 3 arch types in normal occlusion

Introduction: The purposes of this study were to examine the amounts of overjet in the anterior and posterior segments of 3 arch forms by using facial axis points on 3-dimensional virtual models and to verify the minimum posterior extension required for classification of the arch form in normal occlusions. Methods: Facial axis points were digitized on 97 virtual models with normal occlusion, classified into 20 tapered, 25 ovoid, and 52 square arch forms. Intercanine and intermolar arch widths and depths were measured. The best-fitting curves were created, and overjet was measured at each facial axis point. Two-way analysis of variance (ANOVA) was performed to assess the relationship between arch form and overjet in different areas. The minimum posterior extension to determine arch type was analyzed with the chi-square test. Results: Subjects with a tapered arch form had larger overjet compared with those with ovoid and square forms, except at the central incisor. A significant difference in overjet among different areas was found in subjects with a square arch form (P < 0.0001). No significant difference (P = 0.864) was found among the first and second premolar and the first molar groups for classifying arch-form types. Conclusions: A significant difference was found in anterior and posterior overjet according to arch types. The extension to the first premolar was sufficient to classify arch form type. It might be beneficial to consider more coordinated preformed superelastic archwires according to variations in overjet of different arch types. (Am J Orthod Dentofacial Orthop 2011;139:e253-e260)