Micro-computed tomographic evaluation of the effect of fluoride agents on white spot lesions: An in vitro study.

OBJECTIVE: To investigate remineralizing effect of three fluoride regimens on artificially demineralized enamel around orthodontic bracket by analyzing mineral density (MD) acquired from micro-computed tomography (micro-CT). METHODS: Forty-eight bracket bonded bovine incisors were prepared to create demineralized enamel (DE) surface. The samples were divided into four groups according to the fluoride regimen: 1) no fluoridation, 2) 1.23% acidulated phosphate fluoride (APF) gel, 3) fluoridated toothpaste, and 4) 0.05% sodium fluoride mouthwash. Micro-CT was scanned after demineralization (T0), and 2 weeks (T1) and 4 weeks (T2) of fluoridation. RESULTS: APF gel showed highest remineralization of DE during T1-T0 interval among the groups (p < 0.05); followed by toothpaste, mouthwash and no fluoridation. APF gel and toothpaste demonstrated significant increase in MD after 4 weeks of application (p < 0.05). CONCLUSIONS: Remineralization effects of three fluoride regimens were depicted through micro-CT analysis, of which APF gel was most effective.

Prediction of hand-wrist maturation stages based on cervical vertebrae images using artificial intelligence.

OBJECTIVE: To predict the hand-wrist maturation stages based on the cervical vertebrae (CV) images, and to analyse the accuracy of the proposed algorithms. SETTINGS AND POPULATION: A total of 499 pairs of hand-wrist radiographs and lateral cephalograms of 455 orthodontic patients aged 6-18 years were used for developing the prediction model for hand-wrist skeletal maturation stages. MATERIALS AND METHODS: The hand-wrist radiographs and the lateral cephalograms were collected from two university hospitals and a paediatric dental clinic. After identifying the 13 anatomic landmarks of the CV, the width-height ratio, width-perpendicular height ratio and concavity ratio of the CV were used as the morphometric features of the CV. Patients' chronological age and sex were also included as input data. The ground truth data were the Fishman SMI based on the hand-wrist radiographs. Three specialists determined the ground truth SMI. An ensemble machine learning methods were used to predict the Fishman SMI. Five-fold cross-validation was performed. The mean absolute error (MAE), round MAE and root mean square error (RMSE) values were used to assess the performance of the final ensemble model. RESULTS: The final ensemble model consisted of eight machine learning models. The MAE, round MAE and RMSE were 0.90, 0.87 and 1.20, respectively. CONCLUSION: Prediction of hand-wrist SMI based on CV images is possible using machine learning methods. Chronological age and sex increased the prediction accuracy. An automated diagnosis of the skeletal maturation may aid as a decision-supporting tool for evaluating the optimal treatment timing for growing patients.

A long-term longitudinal study of the osteoarthritic changes to the temporomandibular joint evaluated using a novel three-dimensional superimposition method.

The aim of this study was to assess the changes in individual condyles from 5 to 8 years in patients with temporomandibular joint (TMJ) osteoarthritis using 3-dimensional cone beam computed tomography (3D CBCT) reconstruction and superimposition. To assess the longitudinal TMJ changes, CBCT was performed at initial (T0) and final (T2) timepoints that were at least 5 years apart and at a middle (T1) timepoint. To improve the accuracy, we used a novel superimposition method that designated areas of coronoid process and mandibular body. The differences in the resorption and apposition amounts were calculated between each model via maximum surface distances. The greatest resorption and apposition observed were - 7.48 and 2.66 mm, respectively. Evaluation of the changes in each condyle showed that osteoarthritis leads to both resorption and apposition. Resorption was mainly observed in the superior region, while high apposition rates were observed (in decreasing order) in the posterior, lateral, and anterior regions. The medial parts showed greater apposition than the lateral parts in all regions. Our superimposition method reveals that both resorption and apposition were observed in condyles with TMJ osteoarthritis, and resorption/apposition patterns depend on the individual condyle and its sites.

Decreased maxillary sinus volume is a potential predictor of obstructive sleep apnea.

OBJECTIVES: To investigate the associations between nasal airway volume and the presence and severity of obstructive sleep apnea (OSA) in adults. MATERIALS AND METHODS: The medical records of adult patients who visited the sleep clinic at University Hospital between June 2013 and April 2017 and underwent overnight polysomnography for the diagnosis of obstructive sleep apnea were reviewed retrospectively. Using computed tomography, the volumes of the nasal airways and maxillary sinuses were measured, and associations with the presence and severity of OSA were analyzed while controlling for the effects of possible confounders such as lateral cephalometric variables, maxillary widths, tongue/hyoid position, and soft palate dimensions. RESULTS: Comparison between normal subjects and patients with OSA revealed that the latter had decreased ratios of maxillary sinus volume to whole nasal airway volume (P = .029) than normal subjects. OSA severity was greater in those with inferior positions of the hyoid (P = .010), in older patients (P = .011), and in those with high body mass index (P = .001). The volume of the total nasal airway or maxillary sinuses were not associated with OSA severity. CONCLUSIONS: A decreased ratio of maxillary sinus volume to whole nasal airway volume is associated with adult OSA. However, OSA severity is not associated with either maxillary sinus volume or whole nasal airway volume.

Factors associated with spontaneous mesialization of impacted mandibular third molars after second molar protraction.

OBJECTIVES: To investigate factors associated with spontaneous mesialization of impacted third molars after second molar protraction to close the space caused by a missing mandibular first molar (L-6) or retained deciduous mandibular second molars with a missing succedaneous premolar (L-E). MATERIALS AND METHODS: Panoramic radiographs of patients treated with mandibular second molar protraction to close the space due to missing L-6 or L-E (14 males, 36 females, mean age = 18.6 ± 4.4 years) were analyzed before treatment (T1) and after second molar protraction (T2). Factors associated with the amount of third molar mesialization were investigated using regression analyses. RESULTS: Mandibular second molars were protracted by 5.1 ± 2.1 mm and 5.8 ± 2.7 mm, measured at the crown and root furcation, respectively. After second molar protraction, third molars showed spontaneous mesialization by 4.3 ± 1.6 mm and 3.8 ± 2.6 mm, measured at the crown and root furcation, respectively. Nolla's stage of the third molar at T1 (B = 0.20, P = .026) and second molar protraction time (B = 0.04, P = .042) were significantly associated with the amount of third molar mesialization. CONCLUSIONS: Greater third molar mesialization was observed when Nolla's stage of the third molar was higher before treatment and when the second molar protraction time was longer.

Influence of changing various parameters in miniscrew-assisted rapid palatal expansion: A three-dimensional finite element analysis.

OBJECTIVE: This study aimed to analyze the effect of changing various parameters of the bone-borne rapid palatal expander (RPE) using the finite element method (FEM). METHODS: In eight experimental groups, we investigated the effect of the number, position, and length of miniscrews; positional changes of the expander; and changes in the hook length on maxillary expansion. In finite element analysis, we compared the magnitude and distribution of stress, and the displacement changes following expansion of the bone-borne RPE. RESULTS: When we compared the number and position of miniscrews, placing miniscrews in the anterior and posterior sides was advantageous for maxillary expansion in terms of stress distribution and displacement changes. Miniscrew length did not significantly affect stress distribution and displacement changes. Furthermore, anteroposterior displacement of the expander did not significantly affect transverse maxillary expansion but had various effects on vertical changes of the maxilla. The maxilla rotated clockwise when the miniscrews were placed in the anterior region. The hook length of the expander did not show consistent results in terms of changes in stress distribution and magnitude or in displacement changes. CONCLUSIONS: The findings of this study suggest that changes in the location and length of the miniscrews and displacement of the bone-borne RPE could affect the pattern of the maxillary expansion, depending on the combination of these factors.

Change in alveolar bone level of mandibular second and third molars after second molar protraction into missing first molar or second premolar space.

OBJECTIVE: To investigate the factors associated with the change in alveolar bone level of mandibular second and third molars after second molar protraction into the space of the missing first molar (L6) or second premolar (LE). METHODS: Fifty-one patients in whom space of the missing L6 or LE was treated with second molar protraction (13 males, 38 females, mean age 19.6 ± 4.7 years) from 2003 to 2015 were included. The alveolar bone level and position and angulation of the mandibular second and third molars were measured in panoramic radiographs at pre-treatment (T1), and after the alignment of the third molars following second molar protraction (T2). Factors associated with alveolar bone loss on the distal aspect of the mandibular second molars were assessed using linear regression analysis. RESULTS: Age at T1 (P < 0.001) and third molar angulation at T1 (P = 0.002) were significant factors for the prediction of alveolar bone level distal to the second molars. LIMITATION: This study used two-dimensional panoramic radiographs, and we could observe only the interproximal bone level. CONCLUSIONS: After second molar protraction into the missing first molar or second premolar space, mandibular second molars may exhibit alveolar bone resorption in the distal root in older patients and in those with mesially tilted third molars before treatment.

Colorimetric evaluation of white spot lesions following external bleaching with fluoridation: An in-vitro study.

OBJECTIVE: This study was performed to investigate the effects of external tooth bleaching with flouridation on the appearance of white spot lesions (WSLs) in vitro. METHODS: In total, 125 bracket-bonded bovine incisor enamel blocks with artificial WSLs were randomly divided into a control group and four treatment groups (home bleaching, home bleaching + fluoridation, in-office bleaching, and in-office bleaching + fluoridation). A spectroradiometer (SR) and digital images (DIs) were used to evaluate colorimetric parameters (Commission Internationale l'Eclairage L*a*b*) for all specimens. Color measurements were obtained before WSL formation (T1), after WSL formation (T2), and after completion of the external tooth bleaching treatment (T3). RESULTS: The SR-based color change after bleaching was significantly greater in the treatment groups than in the control group (p < 0.05). SR-based lightness (L*) and red-green (a*) values were significantly higher at T2 than at T1 (p < 0.001), with no significant changes in yellow-blue (b*) values. At T3, SR-based L* values had increased while a* and b* values had decreased in the treatment groups (p < 0.001). The DI-based color difference between the sound enamel and WSL areas (ΔE*DI) increased significantly from T1 to T2 in all groups (p < 0.001) and significantly decreased from T2 to T3 in the treatment groups (p < 0.001). No significant differences in ΔE*DI at T3 were shown between the four treatment groups (p > 0.05). CONCLUSIONS: The findings of this study suggested that external tooth bleaching with fluoridation can alleviate the conspicuity of WSLs.

3-D finite element analysis of the effects of post location and loading location on stress distribution in root canals of the mandibular 1st molar.

Objective The purpose of this study was to evaluate, by using finite element analysis, the influence of post location and occlusal loading location on the stress distribution pattern inside the root canals of the mandibular 1st molar. Material and Methods Three different 3-D models of the mandibular 1st molar were established: no post (NP) - a model of endodontic and prosthodontic treatments; mesiobuccal post (MP) - a model of endodontic and prosthodontic treatments with a post in the mesiobuccal canal; and distal post (DP) - a model of endodontic and prosthodontic treatments with a post in the distal canal. A vertical force of 300 N, perpendicular to the occlusal plane, was applied to one of five 1 mm2 areas on the occlusal surface; mesial marginal ridge, distal marginal ridge, mesiobuccal cusp, distobuccal cusp, and central fossa. Finite element analysis was used to calculate the equivalent von Mises stresses on each root canal. Results The DP model showed similar maximum stress values to the NP model, while the MP model showed markedly greater maximum stress values. The post procedure increased stress concentration inside the canals, although this was significantly affected by the site of the force. Conclusions In the mandibular 1st molar, the distal canal is the better place to insert the post than the mesiobuccal canal. However, if insertion into the mesiobuccal canal is unavoidable, there should be consideration on the occlusal contact, making central fossa and distal marginal ridge the main functioning areas.

Bone availability for mandibular molar distalization in adults with mandibular prognathism.

OBJECTIVES: To investigate the retromolar space available for molar distalization in patients with mandibular prognathism. MATERIALS AND METHODS: Using cone-beam computed tomography, the posterior mandibular dimensions in 110 consecutive patients with Class I or Class III malocclusion were measured (mean age, 27.0 ± 7.1 years). The shortest linear distances from the distal root of the right mandibular second molar to the inner border of the mandibular cortex were measured at the level of root furcation and 2, 4, and 6 mm apical to the furcation along the sagittal line and the posterior line of occlusion. The retromolar distances were compared between the Class I and Class III malocclusion groups using general linear mixed models. RESULTS: The retromolar space measured through the sagittal line showed no significant intergroup difference. Among the distances measured through the posterior line of occlusion, the space measured at depths 0 and 2 mm to the furcation were significantly greater in the Class III group than in the Class I group. CONCLUSIONS: Patients with Class III malocclusion have greater retromolar space for mandibular molar distalization along the posterior line of occlusion only at the level of the second molar furcation.

Comparison of antimicrobial activity of traditional and new developed root sealers against pathogens related root canal.

BACKGROUND/PURPOSE: Bacterial infection is closely associated with the failure of endodontic treatment, and use of endodontic sealer with antimicrobial activity and biological compatibility is necessary for the success of root canal treatment. The purpose of this study was to investigate and to compare the antibacterial effect of two calcium silicate-based root canal sealers (Endoseal and EndoSequence BC sealer) as recent development sealers and with three conventional root canal sealers (AH Plus, Sealapex, and Tubli-Seal), before or after setting, on Porphyromonas endodontalis, Porphyromonas gingivalis, and Enterococcus faecalis. MATERIALS AND METHODS: The sealers were soaked in phosphate buffered saline to elute its compositions after and before setting, and the elutes were performed the antimicrobial assay. Also, X-ray fluorescence analysis was carried out to compare compositions of two calcium silicate-based sealers. RESULTS: The conventional root canal sealers have strong antibacterial activity against the Gram-negative bacteria, P. endodontalis and P. gingivalis. Endoseal sealer showed antibacterial activity against not only the Gram-negative bacteria, but also against the Gram-positive bacteria, E. faecalis. However, Endosequence BC sealer exhibited a weak antibacterial effect on all bacteria in this study. X-ray fluorescence analysis exhibited that Endoseal contained more types and more amount of the oxide compound known to have strong antimicrobial activity such as Al2O3, Fe2O3, MgO, Na2O, NiO, and SO2 than Endoseqeunce BC. CONCLUSION: Endoseal, which contains various types of oxide compounds, seems to be a suitable sealer for preventing bacterial infection in both treated and untreated root canals.

Factors associated with long-term vertical skeletal changes induced by facemask therapy in patients with Class III malocclusion.

OBJECTIVES: This study investigated the long-term vertical skeletal changes induced by facemask therapy in patients with Class III malocclusion and different vertical skeletal patterns. MATERIALS AND METHODS: A total of 54 patients (20 boys and 34 girls; mean age, 7.7 ± 2.0 years) with Class III malocclusion who were successfully treated with facemask therapy were included in this study. Vertical skeletal changes (overbite depth indicator, angle between the Sella-Nasion (SN) plane and Gonion-Gnathion (GoGn) line, angle between the Frankfort horizontal (FH) plane and mandibular plane, gonial angle, and angle between the SN plane and palatal plane) were measured on lateral cephalograms from before treatment (T0) to after facemask therapy (T1) and from T0 to after retention (T2). Multivariate linear regression analysis was used to study the associations of the patients' skeletal patterns with the short-term (T0-T1) and long-term (T0-T2) vertical skeletal changes as a result of facemask therapy. RESULTS: The mean treatment period of facemask therapy (T0-T1) was 1.4 ± 0.6 years, and the mean retention period (T1-T2) was 6.9 ± 2.6 years. Age at T0 was significantly correlated with vertical skeletal changes from T0 to T1. Differences in the treatment results between sexes were not significant. The angle between point A-point B line and mandibular plane to mandibular plane angle at T0 and the angle between the FH plane and mandibular plane at T0 were significant predictors for short-term and long-term changes. Changes in the Sella-Nasion-point A from T0 to T1 and from T1 to T2 significantly affected vertical changes in the short term and long term, respectively. CONCLUSIONS: Vertical skeletal changes as a result of facemask therapy are significantly associated with severity of the skeletal Class III malocclusion and mandibular plane angulation before treatment and the amount of forward maxillary growth during the treatment and retention periods.

3-D finite element analysis of the effects of post location and loading location on stress distribution in root canals of the mandibular 1st molar

Abstract Objective The purpose of this study was to evaluate, by using finite element analysis, the influence of post location and occlusal loading location on the stress distribution pattern inside the root canals of the mandibular 1st molar. Material and Methods Three different 3-D models of the mandibular 1st molar were established: no post (NP) - a model of endodontic and prosthodontic treatments; mesiobuccal post (MP) - a model of endodontic and prosthodontic treatments with a post in the mesiobuccal canal; and distal post (DP) - a model of endodontic and prosthodontic treatments with a post in the distal canal. A vertical force of 300 N, perpendicular to the occlusal plane, was applied to one of five 1 mm2 areas on the occlusal surface; mesial marginal ridge, distal marginal ridge, mesiobuccal cusp, distobuccal cusp, and central fossa. Finite element analysis was used to calculate the equivalent von Mises stresses on each root canal. Results The DP model showed similar maximum stress values to the NP model, while the MP model showed markedly greater maximum stress values. The post procedure increased stress concentration inside the canals, although this was significantly affected by the site of the force. Conclusions In the mandibular 1st molar, the distal canal is the better place to insert the post than the mesiobuccal canal. However, if insertion into the mesiobuccal canal is unavoidable, there should be consideration on the occlusal contact, making central fossa and distal marginal ridge the main functioning areas.

Bond Strengths of Orthodontic Metal Brackets to Tribochemically Silica-coated Zirconia Surfaces Using Different 10-Methacryloyloxydecyl Dihydrogen Phosphate-containing Primers.

PURPOSE: To evaluate the effects of tribochemical silica coating and different 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primers on the shear bond strength (SBS) of orthodontic metal brackets to yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) surfaces. MATERIALS AND METHODS: One hundred ninety polished Y-TZP specimens were randomly assigned to 19 groups (n = 10): 30 specimens were used for surface analyses after polishing with 600-grit silicon carbide paper, airborneparticle abrasion with 50-µm alumina (A), or tribochemical silica coating (CoJet [C]); 160 specimens were used in SBS testing of orthodontic metal brackets to Y-TZP after alumina airborne-particle abrasion or tribochemical silica coating and application of either ESPE-Sil (S) (ASn, ASa, CSn, CSa), Alloy Primer (AP) (AAPn, AAPa, CAPn, CAPa), Clearfil Ceramic Primer (CP) (ACPn, ACPa, CCPn, CCPa), or Scotchbond Universal (U) (AUn, AUa, CUn, CUa) and either stored in water for 24 h (non-aged, n) or thermocycled 5000 times (aged, a). The surface analyses and SBSs were statistically analyzed with ANOVA and Tukey's tests. RESULTS: Both mechanically treated surfaces had significantly greater surface roughness and surface free energy than did the polished surfaces. The type of primer and aging significantly affected the bond strength. Among the thermocycled specimens, the AAPa, AUa, and CCPa groups showed the greatest SBS. CONCLUSION: After alumina airborne-particle abrasion, the application of Alloy Primer, Clearfil Ceramic Primer, or Scotchbond Universal provided stable bonding to Y-TZP ceramics. After tribochemical silica coating, however, only Clearfil Ceramic Primer produced a durable bond to Y-TZP ceramics.

Dimensional accuracy of ceramic self-ligating brackets and estimates of theoretical torsional play.

OBJECTIVE: To ascertain the dimensional accuracies of some commonly used ceramic self-ligation brackets and the amount of torsional play in various bracket-archwire combinations. MATERIALS AND METHODS: Four types of 0.022-inch slot ceramic self-ligating brackets (upper right central incisor), three types of 0.018-inch ceramic self-ligating brackets (upper right central incisor), and three types of rectangular archwires (0.016 × 0.022-inch beta-titanium [TMA] (Ormco, Orange, Calif), 0.016 × 0.022-inch stainless steel [SS] (Ortho Technology, Tampa, Fla), and 0.019 × 0.025-inch SS (Ortho Technology)) were measured using a stereomicroscope to determine slot widths and wire cross-sectional dimensions. The mean acquired dimensions of the brackets and wires were applied to an equation devised by Meling to estimate torsional play angle (γ). RESULTS: In all bracket systems, the slot tops were significantly wider than the slot bases (P < .001), yielding a divergent slot profile. Clarity-SLs (3M Unitek, Monrovia, Calif) showed the greatest divergence among the 0.022-inch brackets, and Clippy-Cs (Tomy, Futaba, Fukushima, Japan) among the 0.018-inch brackets. The Damon Clear (Ormco) bracket had the smallest dimensional error (0.542%), whereas the 0.022-inch Empower Clear (American Orthodontics, Sheboygan, Wis) bracket had the largest (3.585%). CONCLUSIONS: The largest amount of theoretical play is observed using the Empower Clear (American Orthodontics) 0.022-inch bracket combined with the 0.016 × 0.022-inch TMA wire (Ormco), whereas the least amount occurs using the 0.018 Clippy-C (Tomy) combined with 0.016 × 0.022-inch SS wire (Ortho Technology).

An in vitro evaluation of the antibacterial properties of three mineral trioxide aggregate (MTA) against five oral bacteria.

OBJECTIVE: The purpose of this study was to evaluate the antibacterial ability of three MTA (MTA-Angelus, Endocem MTA, and ProRoot MTA) against five typical oral bacteria (Streptococcus mutans, Enterococcus faecalis, Lactobacillus rhamnosus, Lactobacillus paracasei, and Porphyromonas gingivalis). DESIGN: For disc diffusion test, each test material was placed into agar plates after inoculation of each bacterial strain. The zones of inhibition of bacterial growth were then measured. Antibacterial broth test was performed by adding the test material into the media. Colony-forming units were counted after incubation with bacteria. The data were analyzed using ANOVA and the Tukey's test. RESULTS: Disc diffusion test showed that the antibacterial activity against S. mutans, L. rhamnosus, L. paracasei, and P. gingivalis ranked in decreasing order of MTA-Angelus>ProRoot MTA>Endocem MTA (p<0.05). An inhibitory effect against E. faecalis was only observed in Endocem MTA. Antibacterial broth test showed that the antibacterial activity against all bacteria was Endocem MTA>MTA-Angelus>ProRoot MTA (p<0.05). CONCLUSION: Discrepant results were obtained from the disc diffusion and antibacterial broth test, with MTA-Angelus and Endocem MTA being most effective, respectively. Both tests revealed that the most resistant bacteria was E. faecalis, which was not susceptible at all, except to Endocem MTA in disc diffusion test.

In vitro microleakage of six different dental materials as intraorifice barriers in endodontically treated teeth.

The aim of this study was to compare the coronal sealing ability of six different dental materials: Three MTA-based cements and three established restorative materials by in vitro dye penetration method. For in vitro infiltration experiments, seventy extracted single-rooted human teeth were used. After crowns of teeth were reduced, root canals were prepared, and filled with gutta-percha cone. Teeth were randomly divided into 6 groups with 10 teeth per group. The orifice of each tooth was prepared to 3 mm depth and filled with the following materials: (I) ProRoot WMTA; (II) EndoCem Zr; (III) Angelus White; (IV) LuxaCore; (V) Fuji II LC; and (VI) Elite. After 5,000 cycles of thermocycling between 5°C and 55°C, dye penetration of each specimen was measured. The order of less dye infiltration of coronal filling materials was: ProRoot WMTA

The relation between idiopathic scoliosis and the frontal and lateral facial form.

OBJECTIVE: The purpose of this study was to evaluate the relation between idiopathic scoliosis and facial deformity in the horizontal, vertical, and anteroposterior planes. METHODS: A total of 123 female patients aged 14 years or older, who visited the Spine Clinic at the Department of Orthopedics, Korea University Guro Hospital for treatment of idiopathic scoliosis, were enrolled. Whole-spine anteroposterior and lateral radiographs were taken with the patient in a naturally erect position, and frontal and lateral cephalograms were taken in an erect position with the Frankfort horizontal line parallel to the floor. Scoliosis was classified according to the Cobb angle and Lenke classification of six curve types. Cephalometric tracing in all cases was carried out with V-Ceph 5.5 by the same orthodontist. The Kruskal-Wallis test was performed to determine whether any relation existed between each group of the idiopathic scoliosis classification and the cephalometric measurements of frontal and lateral cephalograms. RESULTS: The measurements did not reveal any significant association between the Cobb angle and cephalometric measurements and between the curve type based on the Lenke classification and cephalometric measurements. CONCLUSIONS: Based on the results of this study, no apparent relation was observed between the severity of scoliosis and facial form variations in idiopathic scoliosis patients.

Effect of Co doping concentration on structural properties and optical parameters of Co-doped ZnO thin films by sol-gel dip-coating method.

The structural and optical properties of Co-doped ZnO thin films prepared by a sol-gel dip-coating method were investigated. X-ray diffraction analysis showed that the thin films were grown with a c-axis preferred orientation. The position of the (002) peak was almost the same in all samples, irrespective of the Co concentration. It is thus clear that Co doping had little effect on the position of the (002) peak. To confirm that Co2+ was substituted for Zn2+ in the wurtzite structure, optical measurements were conducted at room temperature by a UV-visible spectrometer. Three absorption peaks are apparent in the Co-doped ZnO thin films that do not appear for the undoped ZnO thin film. As the Co concentration was increased, absorption related to characteristic Co2+ transitions increased because three absorption band intensities and the area underneath the absorption wells between 500 and 700 nm increased with increasing Co concentration. The optical band gap and static dielectric constant decreased and the Urbach energy and extinction coefficient increased with increasing Co concentration.

The predictability of dentoskeletal factors for soft-tissue chin strain during lip closure.

OBJECTIVE: To investigate the dentoskeletal factors which may predict soft-tissue chin strain during lip closure. METHODS: The pretreatment frontal and lateral facial photographs and lateral cephalograms of 209 women (aged 18-30 years) with Angle's Class I or II malocclusion were examined. The subjects were categorized by three examiners into the no-strain and strain groups according to the soft-tissue chin tension or deformation during lip closure. Relationships of the cephalometric measurements with the group classification were analyzed by logistic regression analysis, and a classification and regression tree (CART) model was used to define the predictive variables for the group classification. RESULTS: The lower the value of the overbite depth indicator (ODI) and the higher the values of upper incisor to Nasion-Pogonion (U1-NPog, mm), overjet, and upper incisor to upper lip (U1-upper lip, mm), the more likely was the subject to be classified into the strain group. The CART showed that U1-NPog was the most prominent predictor of soft-tissue chin strain (cut-off value of 14.2 mm), followed by overjet. CONCLUSIONS: To minimize strain of the soft-tissue chin, orthodontic treatment should be oriented toward increasing the ODI value while decreasing the U1-NPog, overjet, and U1 upper lip values.