Seong Sik Kim

Effects of buccal corridors on smile esthetics in Japanese and Korean orthodontists and orthodontic patients

INTRODUCTIONnThe purpose of this study was to evaluate the influence of the size of buccal corridors on the assessment of attractive smile esthetics by Japanese and Korean orthodontists and orthodontic patients.nnnMETHODSnBuccal corridors were modified digitally from 0% to 25% compared with the inner intercommissural width. Using a visual analog scale, 41 Japanese and 25 Korean orthodontists, and 96 Japanese and 72 Korean orthodontic patients (15-29 years old) rated the attractiveness of 6 smiles with altered buccal corridors. The influence of the size of the buccal corridor on smile esthetics was assessed.nnnRESULTSnAlthough there was no significant sex difference in judging the effects of buccal corridors for the Korean and Japanese orthodontists, significant sex differences were shown for the Japanese orthodontic patients. There were significant differences in the 6 levels of median esthetic scores for all groups: 0%, 5%, and 10% buccal corridors in the smiles tended to be preferred to the other smiles, to become clinically significant for all groups. The median esthetic score decreased to become clinically significant from 10% to 15% buccal corridors for all groups.nnnCONCLUSIONSnJapanese and Korean orthodontists and orthodontic patients prefer narrow or medium buccal corridors to broad buccal corridors.

Flexible Gd2O2S:Tb scintillators pixelated with polyethylene microstructures for digital x-ray image sensors

Flexible scintillators for digital x-ray image sensors were designed, fabricated and characterized. In these scintillaotrs, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) scintillator pixels were embedded into a polyethylene (PE) substrate. To evaluate the difference in the spatial resolution according to the pixel size, we designed three scintillators with pixels of different pitch sizes: 50 µm pitch size (P50), 100 µm pitch size (P100) and 200 µm pitch size (P200). Because of the high flexibility and good formability, polyethylene was used as the substrate of the scintillator. To fabricate nickel micromolds with high-aspect-ratio microstructures, two microfabrication techniques were employed: silicon dry-etching using a deep reactive ion etching (DRIE) process and nickel electroforming. The pixelated PE microstructures were fabricated by a hot embossing process. Because the solution-type Gd2O2S:Tb precursor can be handled at room temperature, Gd2O2S:Tb was used as the scintillator material. The measured sensitivities of the P50 and P100 models were, respectively, about 65% and 97% of that of the P200 model. The lower sensitivity values of the models with a small pitch size were due to two factors, such as the different pixel heights and the different fill factors. Because a scintillator with a small pixel size has a low fill factor, the sensitivity of the scintillator decreases as the pixel size decreases. The fill factors of the P50, P100 and P200 models were 36%, 49% and 56.25%, respectively. On the other hand, the spatial resolution of the scintillator increases as the pixel size decreases. Therefore, P50 gave the best spatial resolution among the designed models. The spatial frequency at 10% of the modulation transfer function (MTF) with P50 was 13.5 mm−1, while that with P200 was 10.0 mm−1. The resolution pattern and the tooth x-ray images obtained from a scintillator with a smaller pixel size was also clearer than that obtained from a scintillator with a larger pixel size. PE-based flexible Gd2O2S:Tb scintillators can be utilized directly in flexible x-ray image sensors.

Effects of vertical positions of anterior teeth on smile esthetics in Japanese and Korean orthodontists and orthodontic patients

STATEMENT OF PROBLEMnThe perception of a pleasing smile may differ between the countries in Asia or may be converging on a more internationally pleasing one.nnnPURPOSEnThe aim of this study was to evaluate the influence of vertical positions of anterior teeth on smile esthetics as assessed by Japanese and Korean orthodontists as well as by orthodontic patients.nnnMATERIALS AND METHODSnA standard composite smile was constructed from different females intraoral and extraoral photographs. Vertical positions of anterior teeth were modified digitally in 1-mm increments, from 5u2009mm upper lip coverage of the incisors to 5u2009mm gingival exposure. Using a visual analog scale, 41 Japanese orthodontists and 96 Japanese orthodontic patients, 25 Korean orthodontists, and 72 Korean orthodontic patients rated the attractiveness of 11 smiles with altered gingival displays.nnnRESULTSnOverall, the Japanese and Korean raters assigned similar esthetic scores between the corresponding groups. The male orthodontic patients assigned higher scores to the smiles with upper lip coverage of the teeth than the corresponding females did in both countries. The female patients assigned clinically significant higher scores to the smiles from 2u2009mm upper lip coverage of the teeth to 0u2009mm gingival exposure in both countries.nnnCONCLUSIONSnIn both countries, the orthodontists and the female patients shared the similar preference in the smile evaluation of vertical positions of anterior teeth, whereas the male orthodontic patients were more tolerant of upper lip coverage of the anterior teeth than the orthodontists and the female patients.nnnCLINICAL SIGNIFICANCEnThis study proposes 0u2009mm to 2u2009mm of upper lip coverage of the teeth as a threshold of acceptability for esthetic smile evaluations in female orthodontic patients. For male orthodontic patients, the paper proposes negative gingival display as a threshold of acceptability for esthetic smile evaluations.

Quantitative evaluation of midpalatal suture maturation via fractal analysis

Objective The purpose of this study was to determine whether the results of fractal analysis can be used as criteria for midpalatal suture maturation evaluation. Methods The study included 131 subjects aged over 18 years of age (range 18.1–53.4 years) who underwent cone-beam computed tomography. Skeletonized images of the midpalatal suture were obtained via image processing software and used to calculate fractal dimensions. Correlations between maturation stage and fractal dimensions were calculated using Spearmans correlation coefficient. Optimal fractal dimension cut-off values were determined using a receiver operating characteristic curve. Results The distribution of maturation stages of the midpalatal suture according to the cervical vertebrae maturation index was highly variable, and there was a strong negative correlation between maturation stage and fractal dimension (−0.623, p < 0.001). Fractal dimension was a statistically significant indicator of dichotomous results with regard to maturation stage (area under curve = 0.794, p < 0.001). A test in which fractal dimension was used to predict the resulting variable that splits maturation stages into ABC and D or E yielded an optimal fractal dimension cut-off value of 1.0235. Conclusions There was a strong negative correlation between fractal dimension and midpalatal suture maturation. Fractal analysis is an objective quantitative method, and therefore we suggest that it may be useful for the evaluation of midpalatal suture maturation.

Correlation between skeletal and dental changes after mandibular setback surgery-first orthodontic treatment: Cone-beam computed tomography-generated half-cephalograms

Objective To investigate skeletal and dental changes after application of a mandibular setback surgery-first orthodontic treatment approach in cases of skeletal Class III malocclusion. Methods A retrospective study of 34 patients (23 men, 11 women; mean age, 26.2 ± 6.6 years) with skeletal Class III deformities, who underwent surgery-first orthodontic treatment, was conducted. Skeletal landmarks in the maxilla and mandible at three time points, pre-treatment (T0), immediate-postoperative (T1), and post-treatment (T2), were analyzed using cone-beam computed tomography (CBCT)-generated half-cephalograms. Results The significant T0 to T1 mandibular changes occurred -9.24 ± 3.97 mm horizontally. From T1 to T2, the mandible tended to move forward 1.22 ± 2.02 mm, while the condylar position (Cd to Po-perpendicular plane) shifted backward, and the coronoid process (Cp to FH plane) moved vertically. Between T1 and T2, the vertical dimension changed significantly (p < 0.05). Changes in the vertical dimension were significantly correlated to T1 to T2 changes in the Cd to Po-perpendicular plane (r = -0.671, p = 0.034), and in the Cp to FH plane (r = 0.733, p = 0.016), as well as to T0 to T1 changes in the Cp to Po-perpendicular plane (r = 0.758, p = 0.011). Conclusions Greater alterations in the vertical dimension caused larger post-treatment (T2) stage skeletal changes. Studying the mandibular position in relation to the post-surgical vertical dimension emphasized the integral importance of vertical dimension control and proximal segment management to the success of surgery-first orthodontic treatment.

Differentiation and characteristics of undifferentiated mesenchymal stem cells originating from adult premolar periodontal ligaments

Objective The purpose of this study was to investigate the isolation and characterization of multipotent human periodontal ligament (PDL) stem cells and to assess their ability to differentiate into bone, cartilage, and adipose tissue. Methods PDL stem cells were isolated from 7 extracted human premolar teeth. Human PDL cells were expanded in culture, stained using anti-CD29, -CD34, -CD44, and -STRO-1 antibodies, and sorted by fluorescent activated cell sorting (FACS). Gingival fibroblasts (GFs) served as a positive control. PDL stem cells and GFs were cultured using standard conditions conducive for osteogenic, chondrogenic, or adipogenic differentiation. Results An average of 152.8 ± 27.6 colony-forming units was present at day 7 in cultures of PDL stem cells. At day 4, PDL stem cells exhibited a significant increase in proliferation (p < 0.05), reaching nearly double the proliferation rate of GFs. About 5.6 ± 4.5% of cells in human PDL tissues were strongly STRO-1-positive. In osteogenic cultures, calcium nodules were observed by day 21 in PDL stem cells, which showed more intense calcium staining than GF cultures. In adipogenic cultures, both cell populations showed positive Oil Red O staining by day 21. Additionally, in chondrogenic cultures, PDL stem cells expressed collagen type II by day 21. Conclusions The PDL contains multipotent stem cells that have the potential to differentiate into osteoblasts, chondrocytes, and adipocytes. This adult PDL stem cell population can be utilized as potential sources of PDL in tissue engineering applications.

Effects of vermilion height on lip esthetics in Japanese and Korean orthodontists and orthodontic patients

OBJECTIVEnTo evaluate the influence of vermilion height on the assessment of lip attractiveness by Japanese and Korean orthodontists and orthodontic patients.nnnMATERIALS AND METHODSnVermilion heights were modified by increasing or decreasing the vermilion height in 1.0-mm increments from -3.0 mm to 3.0 mm with reference to an average vermilion height. Participants ranged from 15 to 29 years of age and comprised 29 Japanese and 25 Korean orthodontists and 96 Japanese and 72 Korean orthodontic patients. They all rated the attractiveness of seven images with altered vermilion height using a visual analog scale.nnnRESULTSnAcross the participant groups, there were significant differences in the median esthetic scores for the seven vermilion height levels tested. The Japanese and Korean raters assigned the highest scores to the average vermilion height and assigned the lowest scores to the +3-mm increased vermilion height. The ranges of vermilion height preferred by orthodontists were found to be within the ranges preferred by orthodontic patients when evaluating the preferences in lip esthetics by country.nnnCONCLUSIONSnWe conclude that the -1-mm to +1-mm range for the average vermilion height is considered attractive for lips for both Japanese and Korean people.

Improvement of Filtration Performance Using Self-Tuning of Flow Resistance

In this paper, we present the filtration of a liquid sample from polystyrene microparticles analogous to the separation of a biological liquid from mixed particles such as whole blood. The proposed self-tuning of flow resistance can prevent the excessive clogging of microparticles in the microfilter by allowing the automatic change of the flow direction when the microfilter is clogged. Numerically, at about 80% of the clogging of microparticles in the pillar channel, the sample flow is regulated suddenly to the bypass channel. Experimentally, the clogging behavior at the five successive pillar channels and the self-tuning of flow are compared by measuring the clogging area and volume with time. Also, the microfilter array connected in a series can provide an increase in the sample volume proportionally without excessive pressure build-up. This implies the potential to reduce cell fracture in the filtration of biological cells.

Miniscrews versus surgical archwires for intermaxillary fixation in adults after orthognathic surgery

Objective We compared the skeletal and dental changes that resulted from the use of two methods of intermaxillary fixation (IMF)-miniscrews and surgical archwire-in 74 adult patients who had Class III malocclusion and were treated with the same orthognathic surgical procedure at a hospital in Korea. Methods All the patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy with rigid fixation. They were divided into two groups according to the type of IMF used-group 1 underwent surgical archwire fixation and group 2 underwent orthodontic miniscrew fixation. In a series of cephalograms for each patient, we compared vertical and horizontal tooth-position measurements: (a) immediately after surgery (T0), (b) 3 months after surgery (T1), and (c) 6 months after surgery (T2). Cephalometric changes within each group were examined using one-way analysis of variance (ANOVA) while the independent samples t-test procedure was used to compare the two groups. Results After surgery, the maxillary incisors tended to be proclined in both groups although there were no significant differences. Incisor overbite increased significantly in both groups from T0 to T1, and the miniscrew group (group 2) showed slightly greater overbite than the archwire group (group 1). Conclusions This study suggest that the use of orthodontic miniscrews and orthodontic surgical archwire for IMF in adult patients results in similar skeletal and dental changes.

Comparison of postoperative changes in the distal and proximal segments between conventional and sliding mini-plate fixation following mandibular setback

Objective The purpose of the present study was to evaluate the postoperative three-dimensional (3D) changes in the proximal segments after mandibular setback sagittal split ramus osteotomy and to compare the changes between the conventional mini-plate fixation and semi-rigid sliding plate fixation. Methods Cone-beam computed tomography (CBCT) images were used to evaluate the postoperative 3D changes in the proximal segments during the healing process. CBCT images were superimposed using the symphysis and the lower anterior mandible as references. Results There were no statistically significant differences between the conventional mini-plate and semi-rigid sliding plate groups (p > 0.05). With respect to the distribution of changes greater than 2 mm in the landmarks, the right condylion, right coronoid process, and left condylion showed ratios of 55.6%, 50.0%, and 44.4%, respectively, in the semi-rigid sliding plate group; however, none of the landmarks showed ratios greater than 30% in the conventional mini-plate group. Conclusions There were no statistically significant differences in postoperative changes in the segments between the conventional mini-plate and semi-rigid sliding plate groups. Nevertheless, while selecting the type of fixation technique, clinicians should consider that landmarks with greater than 2 mm changes were higher in the semi-rigid sliding plate group than in the conventional mini-plate group.