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Objective To investigate differences in the heritability of skeletodental characteristics between twin pairs with skeletal Class I and Class II malocclusions. Methods Forty Korean adult twin pairs were divided into Class I (C-I) group (0° ≤ angle between point A, nasion, and point B [ANB]) ≤ 4°; mean age, 40.7 years) and Class II (C-II) group (ANB > 4°; mean age, 43.0 years). Each group comprised 14 monozygotic and 6 dizygotic twin pairs. Thirty-three cephalometric variables were measured using lateral cephalograms and were categorized as the anteroposterior, vertical, dental, mandible, and cranial base characteristics. The ACE model was used to calculate heritability (A > 0.7, high heritability). Thereafter, principal component analysis (PCA) was performed. Results Twin pairs in C-I group exhibited high heritability values in the facial anteroposterior characteristics, inclination of the maxillary and mandibular incisors, mandibular body length, and cranial base angles. Twin pairs in C-II group showed high heritability values in vertical facial height, ramus height, effective mandibular length, and cranial base length. PCA extracted eight components with 88.3% in the C-I group and seven components with 91.0% cumulative explanation in the C-II group. Conclusions Differences in the heritability of skeletodental characteristics between twin pairs with skeletal Class I and II malocclusions might provide valuable information for growth prediction and treatment planning.

The aim of this study was to investigate the pattern, amount, and distribution of postsurgical relapse in skeletal Class III patients treated with two-jaw surgery (TJS) using conventional three-stage method (CTM) and surgery-first approach (SFA). A total of 38 patients who underwent the nonextraction approach and TJS (LeFort I posterior impaction and mandibular setback) were divided into CTM and SFA groups (all n = 19/group). Lateral cephalograms were taken before treatment (T0), at 1 month before surgery (T1), immediately after surgery (T2), and at debonding (T3) for CTM patients and at T0, T2, and T3 stages for SFA patients. Cephalometric measurements and statistical analyses were performed. There were no significant differences in the cephalometric variables at all stages except maxillary incisor inclination (U1-UOP) and overbite at T0 between 2 groups. They also did not exhibit significant differences in the amounts of surgical movement except for advancement of the maxilla. The mandible in both groups was rotated slightly clockwise by surgery and counterclockwise during T2-T3 without a significant difference. Distribution of cases with "high relapse" (>30%) and "low relapse" (

OBJECTIVE: To compare the effect of secondary alveolar bone graft (SABG) on the tooth development stage of the maxillary central incisor (MXCI) and maxillary canine (MXC) in terms of the severity of unilateral cleft. MATERIALS AND METHODS: The subjects consisted of 50 boys with unilateral cleft lip and alveolus (UCLA) or unilateral cleft lip, alveolus, and palate (UCLP). The age- and sex-matched subjects were divided into group 1 (UCLA, n = 25; 9.3 ± 0.8 years old) and group 2 (UCLP, n = 25; 9.4 ± 0.6 years old). In panoramic radiographs taken 1 month before (T0) and 1 year after SABG (T1), tooth development stage was evaluated according to the Nolla developmental (ND) stage. A panoramic radiograph taken 3 years after SABG was used as a reference for the final root length of individual tooth. RESULTS: In groups 1 and 2, the ND stage of the MXCI did not exhibit differences between the cleft and non-cleft sides at T0 and T1, respectively. However, although the ND stage of the MXC of group 2 was delayed on the cleft side compared with the non-cleft side at T0 (P < .05), the MXC on the cleft side developed faster than that on the non-cleft side after SABG (P < .01). In terms of tooth development speed, group 2 showed a higher rate of faster developed MXCs on the cleft side compared with the non-cleft side after SABG than group 1 (36.0% vs 8.0%, P < .05). CONCLUSION: SABG performed at approximately 9 years of age might increase tooth development speed of MXC in patients with UCLP compared with patients with UCLA.

OBJECTIVE: To investigate the differences in the amount and pattern of the maxillary incisor (MXI) inclination change in skeletal Class III patients treated with extraction of the maxillary first premolars (MXP1) and two-jaw surgery (TJS) between conventional orthognathic surgery (COS) and surgery-first approach (SFA). MATERIALS AND METHODS: The study included 60 skeletal Class III patients who had normal maxillary position, prognathic mandible, and mild crowding in the maxillary arch (≤4 mm). The patients were divided into group 1 (COS, n = 36) and group 2 (SFA, n = 24). Lateral cephalograms were taken before treatment (T0), 1 month before surgery (T1), within 1 month after surgery (T2), and after debonding (T3) for COS patients and at T0, T2, and T3 for SFA patients. After measurement of the skeletodental variables, statistical analyses were performed. RESULTS: During T0–T2, the amount of MXI inclination change (ΔU1-SN) in group 1 was significantly larger than that in group 2 (−12.8° vs −4.4°; P < .001). During T2–T3, ΔU1-SN in groups 1 and 2 occurred in opposite directions (3.8° vs −5.9°; P < .001). However, the total amount of ΔU1-SN during T0–T3 was not different between groups 1 and 2 (−9.0° vs −10.3°). At T3 the U1-SN values for groups 1 and 2, respectively, moved closer to normal according to the values of the normal range rate (all 83%), relative percentage ratio (102.4% and 100.1%), and achievement ratio (77.7% and 97.8%). CONCLUSIONS: The results of this study might provide basic data for predicting the amount and pattern of MXI inclination change in SFA for skeletal Class III TJS patients.

Objective: This study aimed to compare the effects of conventional and orthodontic mini-implant (OMI) anchorage on tooth movement and arch-dimension changes in the maxillary dentition in Class II division 1 (CII div.1) patients. Methods: CII div.1 patients treated with extraction of the maxillary first and mandibular second premolars and sliding mechanics were allotted to conventional anchorage group (CA, n = 12) or OMI anchorage group (OA, n = 12). Pre- and post-treatment three-dimensional virtual maxillary models were superimposed using the best-fit method. Linear, angular, and arch-dimension variables were measured with software program. Mann-Whitney U-test and Wilcoxon signedrank test were performed for statistical analysis. Results: Compared to the CA group, the OMI group showed more backward movement of the maxillary central and lateral incisors and canine (MXCI, MXLI, MXC, respectively; 1.6 mm, p < 0.001; 0.9 mm, p < 0.05; 1.2 mm, p < 0.001); more intrusion of the MXCI and MXC (1.3 mm, 0.5 mm, all p < 0.01); less forward movement of the maxillary second pre molar, first, and second molars (MXP2, MXM1, MXM2, respectively; all 1.0 mm, all p < 0.05); less contraction of the MXP2 and MXM1 (0.7 mm, p < 0.05; 0.9 mm, p < 0.001); less mesial-in rotation of the MXM1 and MXM2 (2.6°, 2.5°, all p < 0.05); and less decrease of the inter-MXP2, MXM1, and MXM2 widths (1.8 mm, 1.5 mm, 2.0 mm, all p < 0.05). Conclusions: In treatment of CII div.1 malocclusion, OA provided better anchorage and less arch-dimension change in the maxillary pos terior teeth than CA during en-masse retraction of the maxillary anterior teeth. [Korean J Orthod 2012;42(6):280-290]