Stability of clockwise rotation of the maxillary occlusal plane in skeletal Class III patients treated with two-jaw surgery.

OBJECTIVE: The objective of the study was to investigate the post-surgical stability of clockwise rotation of the maxillary occlusal plane (MXOP) after Le Fort I osteotomy for posterior impaction and advancement, in skeletal Class III patients who had undergone two-jaw orthognathic surgery (2J-OGS). MATERIALS AND METHODS: The sample set consisted of 46 patients (18 males and 28 females). Using lateral cephalograms taken at the initial evaluation (T0), before 2J-OGS (T1), after 2J-OGS (T2) and at debonding (T3), the amount of MXOP change (criterion: 2° in ΔMXOP [between T2 and T3]) was used to assign patients to Group 1 (G1, high relapse, -3.09°) or Group 2 (G2, low relapse, -0.99°). Findings were statistically compared between the groups. RESULTS: Compared with G2, G1 exhibited more severe skeletal Class III relationships and a flatter MXOP at T0, a greater increase in ΔANB, and more clockwise rotation of ΔMXOP and ΔFMA between T1 and T2. G1 also showed a greater decrease in ΔANB, higher counterclockwise rotation of ΔMXOP and upward movement of U1 between T2 and T3. Regression analysis yielded the following equation: MXOP (ΔT2-T3) = -0.37 X MXOP (ΔT1-T2) -0.43. CONCLUSIONS: The higher the clockwise rotation of the MXOP during 2J-OGS in skeletal Class III patients, the greater the subsequent relapse (counterclockwise rotation) of the MXOP.

Heritability of maxillary dental cephalometric variables among monozygotic twins, dizygotic twins and their siblings.

OBJECTIVES: The purpose of this study was to investigate the heritability of dental cephalometric variables by analyzing vertical linear measurements and angular measurements of the upper incisor, canine, and first molar. MATERIALS AND METHODS: Among the 553 Korean patients who participated in twin studies conducted at Samsung Medical Center, 150 patients had their lateral cephalometric radiograph data included in this study. The group was comprised of 36 monozygotic (MZ) twins (males, 16 pairs; females, 20 pairs), 13 dizygotic (DZ) twins (males, 7 pairs; females, 6 pairs), and 26 same-sex sibling pairs (males, 11 pairs; females, 15 pairs). All patients were over 20 years old with a mean age of 39.75 years. Lateral cephalometric diagrams and linear measurements (6 vertical factors, 6 horizontal factors) were taken. Three axial planes were measured for each tooth; intraclass correlation coefficients (ICCs) were obtained for each group and heritability was calculated using Falconer's method. RESULTS: ICCs of vertical linear measurements (average 0.837, P < 0.01) and the tooth axis of the central incisor and canine (average 0.679, P < 0.001) were higher in the MZ group compared to the DZ and sibling groups; thus, these variables showed high heritability. CONCLUSIONS: Orthodontic treatment aiming to alter the tooth axis of the maxillary central incisor or canine or other vertical factors with greater heritability can be difficult, requiring strategic treatment planning to achieve desired treatment outcome and stability. CLINICAL RELEVANCE: The active early treatment to gain tooth eruption space can lead to normal tooth position.

Cone-beam computed tomography and digital model analysis of maxillary buccal alveolar bone thickness for vertical temporary skeletal anchorage device placement.

INTRODUCTION: This study aimed to quantify the buccal alveolar bone thickness (BABT) in the maxillary molar region to provide a practical guideline for vertical temporary skeletal anchorage device (TSAD) placement using cone-beam computed tomography (CBCT). It also aimed to develop a linear regression model for use in digital models to predict available BABT. METHODS: The sample for this retrospective study consisted of 31 sites (24 patients; mean age, 28.75 years; range, 18-44 years) in which vertical TSADs were placed successfully in the maxillary posterior interradicular area during the total arch distalization procedure. BABT was measured at 3 points of the interradicular space using CBCT, and the buccal alveolar region thickness (BART), which included buccal-attached gingival thickness and the buccal alveolar bone, was measured using the digital model. In CBCT, BABT was measured at the most convex point of the lamina dura of the root adjacent to the vertical TSAD mesially, at the most convex point of the lamina dura of the root adjacent to the vertical TSAD distally, and the central point between the mesial and distal points. Three linear measurements were obtained at 2, 4, and 6 mm apical to the alveolar crest: the mesial thickness, the central thickness (centralCBCT), and the distal thickness. In the digital model, the most convex points of the clinical crowns of 2 teeth adjacent to vertical TSAD and their contact point along with the corresponding Will Andrews and Lawrence Andrews ridge were identified. The horizontal distance paralleling the model base was digitally measured and recorded at 3 positions: the mesial, central, and distal points. Then, the following 3 linear measurements were taken directly on each 3-dimensional dental model: the mesial thickness, the central thickness (centralModel), and the distal thickness. RESULTS: Both BABT and BART at the central position (centralCBCT, 3.44 mm; centralModel, 6.28 mm) were thicker than at the 2 exterior positions (mesial thickness, 2.16; distal thickness, 2.59 mm; mesial thickness, 2.74 mm; distal thickness, 2.99 mm). BABT was thinnest at 2 mm from the alveolar crest, and there was no statistically significant difference between 4 mm and 6 mm. There was a strong correlation between centralModel and centralCBCT. CONCLUSIONS: The mean BABT and BART at the central position, in which we suggest placing vertical TSADs, were 3.44 ± 0.69 mm in CBCT and 6.28 ± 1.11 mm in the digital model, respectively. The minimum BABT and BART at the central position in which vertical TSAD was placed successfully were 2.38 mm in CBCT and 4.25 mm in the digital model. There was a strong correlation between centralCBCT and centralModel, and we developed a linear regression model that resulted in a useful formula for estimating the actual available BABT at the central position: centralCBCT = 0.57 × centralModel - 0.15.

Pharyngeal Airway Morphology in Skeletal Class III With Mandibular Asymmetry is Improved After Bimaxillary Orthognathic Surgery.

PURPOSE: The relationship between pharyngeal airway morphology and jawbone movements in skeletal Class III patients with mandibular asymmetry after orthognathic surgery remains unclear. This study was to measure the changes in pharyngeal airway morphology in skeletal Class III patients with mandibular asymmetry after bimaxillary surgery and evaluate associations between changes in pharyngeal airway morphology and skeletal movements. METHODS: In this retrospective cohort study, skeletal Class III patients who underwent bimaxillary surgery were enrolled. The predictor variable was facial symmetry status divided into 2 groups, asymmetric (Group A) and symmetric (Group B). The primary outcome variables were changes in airway parameters, including cross-sectional linear distances, cross-sectional area (CSA), minimum CSA (Min-CSA), and volume; and airway asymmetry index between the preoperative and 6-month postoperative imaging studies. Correlation analysis was performed between upper airway and skeletal changes. RESULTS: Twenty-five patients were included in this study, with 15 patients in Group A (mean age: 23.00 years; BMI: 22.83) and 10 patients in Group B (mean age: 22.30 years; BMI: 22.48). Group A showed a higher asymmetry index than Group B at T0; however, no significant differences compared to Group B at T1. The airway volume was significantly decreased in the oropharynx in Group A at T1, whereas it showed no significant differences in Group B (P < .05). Lateral movement of B point and Menton showed positive correlations with changes in Min-CSA in the oropharynx and negative correlations with changes in airway asymmetry index (P < .05). CONCLUSIONS: Pharyngeal airway exhibited an asymmetrical and constricted morphology in Group A before surgery. The airway morphology in Group A showed a tendency to adopt a symmetrical and less constricted shape after surgery. The airway space was reduced in the oropharynx in Group A after surgery. Surgical correction of mandibular asymmetry correlated with the improvement of pharyngeal airway morphology.

Heritability of Facial Skeletal and Dental Characteristics of Monozygotic and Dizygotic Twins Using Cephalometric Analysis and Falconer's Method.

The purpose of this study was to investigate the heritability of facial skeletal and dental characteristics of the monozygotic (MZ) and dizygotic (DZ) twins. The samples consisted of Korean MZ and DZ twins (n = 13 pairs/each twin; 7 pairs of males and 6 pairs of females; mean age, 39 years, respectively). The linear, angular, and ratio variables, which could describe the size and shape of the facial horizontal and vertical, dental, mandible and cranial base structure, were measured. The Falconer's method was used to calculate the heritability (h; close to or below 0, low heritability; close to or above 1, high heritability). In the facial horizontal and vertical aspects, the highest h values were shown at SNA (degree, 1.53), SNB (degree, 2.12), SN-Pog (degree, 2.19), SN-palatal plane angle (degree, 1.29), SN-mandibular plane angle (degree, 1.59), N-ANS/ANS-Me (1.66), and ANS-Me/N-Me (1.62). In the dental aspects, although L1-occlusal plane angle (degree, 1.38) and SN-occlusal plane angle (degree, 2.09) showed high h values, most of the dental variables showed low h values. In the mandible and cranial base, lower gonial angle, mandibular body length, and cranial base angle showed high h values (N-Go-Gn [degree], 1.07; Go-Pog [mm], 0.92; N-S-Ba [degree], 1.51). The descending order of the overall mean h values was the facial horizontal (1.10), facial vertical (0.71), mandible (0.59), cranial base (0.37), and dental characteristics (-0.11). The shape of facial skeletal structure and location of the occlusal plane within skeletal framework was more influenced by genetic factors than environmental factors.

Alveolar Molding Effect in Infants With Unilateral Cleft Lip and Palate: Comparison of Two- and Three-Dimensional Measurements.

The purpose of this study was to compare the results of two- (2D) and three-dimensional (3D) measurements for the alveolar molding effect in patients with unilateral cleft lip and palate. The sample consisted of 23 unilateral cleft lip and palate infants treated with nasoalveolar molding (NAM) appliance. Dental models were fabricated at initial visit (T0; mean age, 23.5 days after birth) and after alveolar molding therapy (T1; mean duration, 83 days). For 3D measurement, virtual models were constructed using a laser scanner and 3D software. For 2D measurement, 1:1 ratio photograph images of dental models were scanned by a scanner. After setting of common reference points and lines for 2D and 3D measurements, 7 linear and 5 angular variables were measured at the T0 and T1 stages, respectively. Wilcoxon signed rank test and Bland-Altman analysis were performed for statistical analysis. The alveolar molding effect of the maxilla following NAM treatment was inward bending of the anterior part of greater segment, forward growth of the lesser segment, and decrease in the cleft gap in the greater segment and lesser segment. Two angular variables showed difference in statistical interpretation of the change by NAM treatment between 2D and 3D measurements (ΔACG-BG-PG and ΔACL-BL-PL). However, Bland-Altman analysis did not exhibit significant difference in the amounts of change in these variables between the 2 measurements. These results suggest that the data from 2D measurement could be reliably used in conjunction with that from 3D measurement.

The surgical outcomes of anterior segmental osteotomy in Asian skeletal class II patients.

PURPOSE: Anterior segmental osteotomy (ASO) following the surgery-first approach is a long-established treatment modality to resolve lip protrusion in patients with skeletal class II patterns. However, the indications and effectiveness of ASO still remain uncertain. The objective of this study is to investigate the effectiveness of ASO in Asian skeletal class II patients by evaluating the skeletal and soft tissue changes and analyzing pre-treatment variables that determine successful outcomes in occlusal as well as esthetic aspects. METHODS: The lateral cephalograms of 44 skeletal class II patients who underwent ASO and orthodontic treatment for resolving lip protrusion were retrospectively collected. Hard and soft tissue variables of two groups, normalized (NG) and unnormalized (UNG) ANB after treatment were compared and analyzed. The rotational effect of the anterior segment on the hard and soft tissue was also investigated. RESULTS: ASO was successful in correcting the skeletal class II relationship and lip protrusion (ΔANB - 2.3°, 4-5 mm lips retraction) in most cases. However, for patients with severely camouflaged skeletal class II incisors involving a large ANB and SNA, a large ANB still remained post-treatment. The study also found that rotation of the upper and lower anterior segments further augmented the amount of lip retraction. CONCLUSIONS: ASO was found to successfully correct ANB of skeletal class II patients under the following conditions (ANB 5.3° ± 1.5°, SNB 77.3° ± 4.5°, U1 to FH 115° ± 7.5, L1 to FH 48.0° ± 4.6). However, patients with larger ANB and SNA values may require bi-maxillary surgery. In addition, ASO has limitations in correcting gummy smile in cases of extreme maxillary excess. For patients requiring a large amount of lip retraction, rotation of the anterior segment may be beneficial in conjunction with bi-maxillary surgery.

The prediction of sagittal chin point relapse following two-jaw surgery using machine learning.

The study aimed to identify critical factors associated with the surgical stability of pogonion (Pog) by applying machine learning (ML) to predict relapse following two-jaw orthognathic surgery (2 J-OGJ). The sample set comprised 227 patients (110 males and 117 females, 207 training and 20 test sets). Using lateral cephalograms taken at the initial evaluation (T0), pretreatment (T1), after (T2) 2 J-OGS, and post treatment (T3), 55 linear and angular skeletal and dental surgical movements (T2-T1) were measured. Six ML modes were utilized, including classification and regression trees (CART), conditional inference tree (CTREE), and random forest (RF). The training samples were classified into three groups; highly significant (HS) (≥ 4), significant (S) (≥ 2 and < 4), and insignificant (N), depending on Pog relapse. RF indicated that the most important variable that affected relapse rank prediction was ramus inclination (RI), CTREE and CART revealed that a clockwise rotation of more than 3.7 and 1.8 degrees of RI was a risk factor for HS and S groups, respectively. RF, CTREE, and CART were practical tools for predicting surgical stability. More than 1.8 degrees of CW rotation of the ramus during surgery would lead to significant Pog relapse.

A new rationale for preservation of the mandibular third molar in orthognathic patients with missing molars.

Controversies exist regarding the need for prophylactic extraction of mandibular third molars in patients who plan to undergo orthognathic surgery. An 18-year-old male patient was diagnosed with mandibular prognathism and maxillary retrognathism with mild facial asymmetry. He had a severely damaged mandibular first molar and a horizontally impacted third molar. After extraction of the first molar, the second molar was protracted into the first molar space, and the third molar erupted into the posterior line of occlusion. The orthognathic surgery involved clockwise rotation of the maxillomandibular complex as well as angle shaving and chin border trimming. Patients who are missing or have damaged mandibular molars should be monitored for eruption of third molars to replace the missing posterior tooth regardless of the timing of orthognathic surgery.

Alveolar bone changes after molar protraction in young adults with missing mandibular second premolars or first molars.

OBJECTIVES: To assess the changes in alveolar bone of the mandibular second molars following molar protraction and investigate the factors associated with the alveolar bone changes. MATERIALS AND METHODS: Cone-beam computed tomography of 29 patients (mean age 22.0 ± 4.2 years) who had missing mandibular premolars or first molars and underwent molar protraction were reviewed. Alveolar bone level was measured as the distance from the cementoenamel junction at six points, buccal, lingual, mesiobuccal (MB), mesiolingual (ML), distobuccal (DB), and distolingual (DL), of the second molars at pretreatment (T0) and after molar protraction (T1). Factors associated with alveolar bone changes at the distal and mesial of the second molars were assessed. RESULTS: Mean alveolar bone changes ranged from -1.2 mm (bone apposition) to 0.8 mm (bone resorption). The presence of a third molar impaction at T0 (P < .001), third molar angulation at T0 (P < .001), and Nolla's stage of third molar at T0 (P = .005) were significantly associated with alveolar bone level changes distal to the second molars. Treatment duration (P = .028) was significantly associated with alveolar bone level changes mesial to the second molar. CONCLUSIONS: Patients with impacted third molars, third molars at an earlier stage of development, and mesially angulated third molars at pretreatment may have less alveolar bone resorption distal to the second molars following protraction. Patients with increased treatment time may have reduced alveolar bone resorption mesial to the second molars.

Midfacial soft tissue changes after maxillary expansion using micro-implant-supported maxillary skeletal expanders in young adults: A retrospective study.

OBJECTIVE: The aim of this retrospective study was to assess the midfacial soft tissue changes following maxillary expansion using micro-implant-supported maxillary skeletal expanders (MSEs) in young adults by cone-beam computerized tomography (CBCT) and to evaluate the correlations between hard and soft tissue changes after MSE usage. METHODS: Twenty patients (mean age, 22.4 years; range, 17.6-27.1) with maxillary transverse deficiency treated with MSEs were selected. Mean expansion amount was 6.5 mm. CBCT images taken before and after expansion were superimposed to measure the changes in soft and hard tissue landmarks. Statistical analyses were performed using paired t-test and Pearson's correlation analysis on the basis of the normality of data. RESULTS: Average lateral movement of the cheek points was 1.35 mm (right) and 1.08 mm (left), and that of the alar curvature points was 1.03 mm (right) and 1.02 mm (left). Average forward displacement of the cheek points was 0.59 mm (right) and 0.44 mm (left), and that of the alar curvature points was 0.61 mm (right) and 0.77 mm (left) (p < 0.05). Anterior nasal spine (ANS), posterior nasal spine (PNS), and alveolar bone width showed significant increments (p < 0.05). Changes in the cheek and alar curvature points on both sides significantly correlated with hard tissue changes (p < 0.05). CONCLUSIONS: Maxillary expansion using MSEs resulted in significant lateral and forward movements of the soft tissues of cheek and alar curvature points on both sides in young adults and correlated with the maxillary suture opening at the ANS and PNS.

Twin study-genetic comparison of matrix versus intramatrix rotation in the mandible and three different occlusal planes.

BACKGROUND: The purpose of this study is to investigate the heritability of total rotation, matrix rotation, and intramatrix rotation of the mandible in Korean monozygotic (MZ) twins, dizygotic (DZ) twins, and their siblings. MATERIALS AND METHODS: The samples consisted of 75 pairs of Korean twins (39.7 + 9.26 years; MZ group, 36 pairs; DZ group, 13 pairs; sibling group, 26 pairs). Lateral cephalograms were taken, and 13 variables related to internal and external mandible rotation were measured. Three types of occlusal planes (bisected occlusal plane, functional occlusal plane, and the MM bisector occlusal plane) were used to evaluate genetic influence on the occlusal plane. Heritability (h2) was calculated by using the intraclass correlation coefficient (ICC) and Falconer's method. RESULTS: With regard to mandibular rotation, the MZ twin group showed significantly higher ICC values compared to the DZ twin and sibling groups. The ICC mean values for 13 cephalometric measurements were 0.85 (MZ), 0.62 (DZ), and 0.52 (siblings) respectively. The heritability of the total rotation (0.48) and matrix rotation (0.5) between the MZ and DZ groups was higher than that of the intramatrix rotation (- 0.14). All of the three types of occlusal plane showed high heritability, and among the three types, the functional occlusal plane showed the highest heritability (h2 = 0.76). CONCLUSION: Based on these findings that showed a strong genetic effect on total rotation and matrix rotation, maintaining these rotations should be carefully considered in the orthodontic treatment plan, while the lower border of the mandible may be responsive to various treatments. Occlusal plane change, especially with regard to the functional occlusal plane, may not be stable due to strong genetic influences.

A study on the morphologic change of palatal alveolar bone shape after intrusion and retraction of maxillary incisors.

The purpose of this study is to evaluate the changes in the palatal alveolar bone thickness and find the factors related to the resorption of the palatal alveolar bone caused by tooth movement after the maxillary incisors were retracted and intruded during orthodontic treatment. The study group comprised of 33 skeletal Class II malocclusion patients who underwent extraction for orthodontic treatment. Palatal alveolar bone thickness changes and resorption factors were identified and analyzed. The changes of maxillary central incisors and palatal alveolar bone thickness were measured, and the corresponding sample t test was performed using SPSS (IBM SPSS version 22). The amount of palatal alveolar bone resorption was measured and various parameters were analyzed to determine which factors affected it. Correlation analysis adopting the amount of palatal alveolar bone resorption as a dependent variable demonstrated that the SNB, mandibular plane angle, and the inclination of the maxillary central incisor were significantly correlated with before treatment. On the other hand, mandibular plane angle, angle of convexity, the inclination of the upper incisor, and the occlusal plane (UOP, POP) were significantly correlated with post-treatment. In addition, the variables related to palatal contour (PP to PAS, SN to PAS, palatal surface angle) and occlusal planes (UOP/POP) were significantly correlated with the difference in palatal bone resorption. During initial diagnosis, high angle class II with normal upper incisor inclination can be signs of high-risk factors. In addition, maintaining the occlusal plane during treatment helps to prevent palatal bone loss.

Alveolar bone remodeling during maxillary incisor intrusion and retraction.

BACKGROUND: Maxillary incisor protrusion is a prevalent dental deformity and is often treated by upper incisor intrusion and retraction. The mechanical loading triggers the resorption and apposition of the bone. Alveolar bone remodeling is expected to follow orthodontic tooth movement in a one-to-one relationship. However, in many cases, the outcomes are different. Alveolar bone might still remain thick causing lip protrusion and other aesthetic problems after treatment. Additional corrective procedures such as alveoloplasty. On the other hand, if the labial bone becomes too thin, periodontal problems like gingival recession might occur. The unpredictability of the treatment result and the risk of requiring corrective procedures pose significant challenges to both the providers and patients. The aim of this study is to determine factors that can help to predict the alveolar bone reaction before maxillary incisor intrusion and retraction. METHODS: The cohort included 34 female patients (mean age 25.8 years) who were diagnosed with skeletal class II malocclusion with upper incisor protrusion. These patients underwent extraction and orthodontic treatment with upper incisor intrusion and retraction. Lateral cephalograms at pre-treatment and post-treatment were taken. Linear and angular measurements were analyzed to evaluate the alveolar bone changes based on initial conditions. RESULTS: The study found that the relative change, calculated as change in alveolar bone thickness after treatment divided by the initial alveolar thickness, was inversely correlated with the initial thickness. There was a significant increase of labial alveolar bone thickness at 9-mm apical from cementoenamel junction (B3) (P < 0.05) but no statistically significant change in the thickness at other levels. In addition, the change in angulation between the incisor and alveolar bone was inversely correlated with several initial angulations: between the initial palatal plane and upper incisor angle, between the initial palatal plane and upper incisor labial surface angle, and between the initial palatal plane and bone labial surface angle. On the other hand, the change in labial bone thickness was neither significantly correlated with the initial thickness nor significantly correlated to the amount of retraction. CONCLUSION: The unpredictability of alveolar bone remodeling after upper incisor intrusion and retraction poses significant challenges to treatment planning and patient experience. The study showed that the initial angulation between the incisor and alveolar bone is correlated with the change in angulation after treatment, the initial thickness of the alveolar bone was correlated with the relative change of the alveolar bone thickness (defined as change in thickness after treatment divided by its initial thickness), and the amount of intrusion was correlated with the alveolar bone thickness change at 9-mm apical from the cementoenamel junction after treatment. The results of the present study also revealed that the change in labial alveolar bone thickness was neither significantly correlated with the initial thickness nor significantly correlated to the amount of retraction.

Influence of heritability on craniofacial soft tissue characteristics of monozygotic twins, dizygotic twins, and their siblings using Falconer's method and principal components analysis.

OBJECTIVE: The purpose of this study was to investigate the influence of heritability on the craniofacial soft tissue cephalometric characteristics of monozygotic (MZ) twins, dizygotic (DZ) twins, and their siblings (SIB). METHODS: The samples comprised Korean adult twins and their siblings (mean age, 39.8 years; MZ group, n = 36 pairs; DZ group, n = 13 pairs of the same gender; and SIB group, n = 26 pairs of the same gender). Thirty cephalometric variables were measured to characterize facial profile, facial height, soft-tissue thickness, and projection of nose and lip. Falconer's method was used to calculate heritability (low heritability, h2 < 0.2; high heritability, h2 > 0.9). After principal components analysis (PCA) was performed to extract the models, we calculated the intraclass correlation coefficient (ICC) value and heritability of each component. RESULTS: The MZ group exhibited higher ICC values for all cephalometric variables than DZ and SIB groups. Among cephalometric variables, the highest h2 (MZ-DZ) and h2 (MZ-SIB) values were observed for the nasolabial angle (NLA, 1.544 and 2.036), chin angle (1.342 and 1.112), soft tissue chin thickness (2.872 and 1.226), and upper lip thickness ratio (1.592 and 1.026). PCA derived eight components with 84.5% of a cumulative explanation. The components that exhibited higher values of h2 (MZ-DZ) and h2 (MZ-SIB) were PCA2, which includes facial convexity, NLA, and nose projection (1.026 and 0.972), and PCA7, which includes chin angle and soft tissue chin thickness (2.107 and 1.169). CONCLUSIONS: The nose and soft tissue chin were more influenced by genetic factors than other soft tissues.

Teeth discoloration during orthodontic treatment.

OBJECTIVE: Teeth discoloration is a rare orthodontic complication. The aim of this study was to report the clinical progression of discoloration during orthodontic treatment. METHODS: Discolored teeth, detected during orthodontic treatment between January 2003 and December 2012 by a single dentist using similar techniques and appliances, were analyzed. RESULTS: The total number of teeth that showed discoloration was 28. Progression of discoloration was evaluated in only 24 teeth that were observed without any treatment. During the observation period, the discoloration "improved" in 8 of the 24 teeth (33.3%) and was "maintained" in 16 (66.6%). The electric pulp test performed at the time of initial detection of discoloration showed 14.3% positivity, which improved to 21.4% at the final follow-up. None of the initial and final follow-up radiographic findings showed any abnormalities. CONCLUSIONS: When teeth discoloration is detected during orthodontic treatment, observation as an initial management is recommended over immediate treatments.

Determination of midsagittal plane for evaluation of facial asymmetry using three-dimensional computed tomography.

PURPOSE: The aim of the present study was to investigate the disagreement of cephalometric analysis depending on the reference determination of midsagittal plane on three-dimensional computed tomography. MATERIALS AND METHODS: A total of 102 young women with class III dentofacial deformity were evaluated using three-dimensional computed tomography. The cranial and facial midsagittal planes were defined and the amounts of jaw deviation were calculated. The amounts of jaw deviation were compared with paired t-test (2-tailed) and Bland-Altman plot was drawn. RESULTS: The landmark tracing were reproducible (r≥.978). The jaws relative to the cranial midsagittal plane were 10-17 times more significantly deviated than to the facial midsagittal plane (P<.001). Bland-Altman plot demonstrated that the differences between the amounts of jaw deviation from two midsagittal planes were not normally distributed versus the average of the amounts of jaw deviation from two midsagittal planes. CONCLUSION: The cephalometric analyses of facial asymmetry were significantly inconsistent depending on the reference determination of midsagittal plane. The reference for midsagittal plane should be carefully determined in three-dimensional cephalometric analysis of facial asymmetry of patients with class III dentofacial deformity.

The effect of antioxidants on the production of pro-inflammatory cytokines and orthodontic tooth movement.

Orthodontic force causes gradual compression of the periodontal ligament tissues, which leads to local hypoxia in the compression side of the tissues. In this study, we investigated whether antioxidants exert a regulatory effect on two factors: the expression of pro-inflammatory cytokines in human periodontal ligament fibroblasts (PDLFs) that were exposed to mechanical compression and hypoxia and the rate of orthodontic tooth movement in rats. Exposure of PDLFs to mechanical compression (0.5-3.0 g/cm(2)) or hypoxic conditions increased the production of intracellular reactive oxygen species. Hypoxic treatment for 24 h increased the mRNA levels of IL-1ß, IL-6 and IL-8 as well as vascular endothelial growth factor (VEGF) in PDLFs. Resveratrol (10 nM) or N-acetylcysteine (NAC, 20 mM) diminished the transcriptional activity of hypoxiainducible factor-1 and hypoxia-induced expression of VEGF. Combined treatment with mechanical compression and hypoxia significantly increased the expression levels of IL-1ß, IL-6, IL-8, TNF-α and VEGF in PDLFs. These levels were suppressed by NAC and resveratrol. The maxillary first molars of rats were moved mesially for seven days using an orthodontic appliance. NAC decreased the amount of orthodontic tooth movement compared to the vehicle-treated group. The results from immunohistochemical staining demonstrated that NAC suppressed the expression of IL-1ß and TNF-α in the periodontal ligament tissues compared to the vehicle-treated group. These results suggest that antioxidants have the potential to negatively regulate the rate of orthodontic tooth movement through the down-regulation of pro-inflammatory cytokines in the compression sides of periodontal ligament tissues.