Morphometric analysis of the maxillary root apex positions according to crowding severity.

OBJECTIVES: To determine differences in arch forms derived from the root apices locations between individuals with <2 mm maxillary crowding and controls. SETTING AND SAMPLE POPULATION: The Department of Orthodontics, Pusan National University. Cone-beam computed tomography (CBCT) images of 102 patients in the control group and 95 patients in the crowding group. MATERIALS AND METHODS: X, Y and Z coordinates of the tip of the crowns and the apex of the root of the maxillary teeth (except second molars) were determined on the CBCT images. The acquired three-dimensional (3D) coordinates were converted into two-dimensional (2D) coordinates via projection on the palatal plane, and the Procrustes analysis was employed to process the converted 2D coordinates. The mean shape of the arch form derived from the location of the tip of the crowns and the apex of the root was compared between groups using the statistical shape analysis. RESULTS: There was a statistically significant difference (P = .046) between the groups for the mean shape of the root apex arch form, but the difference was small and clinically irrelevant as it is minor compared to the degree of crowding. CONCLUSIONS: Maxillary arch from at the level of the maxillary apices only shows minor differences between crowded and non-crowded dentitions.

MiRNA-181a regulates Toll-like receptor agonist-induced inflammatory response in human fibroblasts.

MicroRNAs (miRNAs) regulate the synthesis of cytokines in response to Toll-like receptor (TLR) activation. Our recent microarray study comparing normal and inflamed human dental pulps showed that miRNA-181 (miR-181) family is differentially expressed in the presence of inflammation. Prior studies have reported that the dental pulp, which is composed primarily of TLR4/2+ fibroblasts, expresses elevated levels of cytokines including interleukin-8 (IL-8) when inflamed. In this study, we employed an in-vitro model to determine the role of the miRNA-181 family in the TLR agonist-induced response in human fibroblasts. TLR4/2+ primary human dental pulp fibroblasts were stimulated with lipopolysaccharide from Porphyromonas gingivalis (Pg LPS), a known oral pathogen, and IL-8 and miR-181 expression measured. An inversely proportional relationship between IL-8 and miR-181a was observed. In-silico analysis identified a miR-181a-binding site on the 3' untranslated region (UTR) of IL-8, which was confirmed by dual-luciferase assays. MiR-181a directly binds to the 3'UTR of IL-8, an important inflammatory component of the immune response, and modulates its levels. This is the very first report demonstrating miR-181a regulation of IL-8.

Three-dimensional multipotent progenitor cell aggregates for expansion, osteogenic differentiation and 'in vivo' tracing with AAV vector serotype 6.

Multipotent adult progenitor cells (MAPCs) are bone marrow-derived stem cells with a high growth rate suitable for therapeutical applications as three-dimensional (3D) aggregates. Combined applications of osteogenically differentiated MAPC (OD-MAPC) aggregates and adeno-associated viral vectors (AAV) in bone bioengineering are still deferred until information with regard to expansion technologies, osteogenic potential, and AAV cytotoxicity and transduction efficiency is better understood. In this study, we tested whether self-complementary AAV (scAAV) can potentially be used as a gene delivery system in an OD-MAPC-based 'in vivo' bone formation model in the craniofacial region. Both expansion of rat MAPC (rMAPC) and osteogenic differentiation with dexamethasone were also tested in 3D aggregate culture systems 'in vitro' and 'vivo'. rMAPCs grew as undifferentiated aggregates for 4 days, with a population doubling time of 37 h. After expansion, constant levels of Oct4 transcripts, and Oct4 and CD31 surface markers were observed, which constitute a hallmark of undifferentiated stage of rMAPCs. Dexamethasone effectively mediated rMAPC osteogenic differentiation by inducing the formation of a mineralized collagen type I network, and facilitated the activation of the wnt/ß-catenin, a crucial pathway in skeletal development. To investigate the genetic modification of rMAPCs grown as 3D aggregates before implantation, scAAV serotypes 2, 3 and 6 were evaluated. scAAV6 packaged with the enhanced green fluorescent protein expression cassette efficiently mediated long-term transduction (10 days) 'in vitro' and 'vivo'. The reporter transduction event allowed the tracing of OD-rMAPC (induced by dexamethasone) aggregates following OD-rMAPC transfer into a macro-porous hydroxyapatite scaffold implanted in a rat calvaria model. Furthermore, the scAAV6-transduced OD-rMAPCs generated a bone-like matrix with a collagenous matrix rich in bone-specific proteins (osteocalcin and osteopontin) in the scaffold macro-pores 10 days post-implantation. Newly formed bone was also observed in the interface between native bone and scaffold. The collective work supports future bone tissue engineering applications of 3D MAPC cultures for expansion, bone formation and the ability to alter genetically these cells using scAAV vectors.

Influence of customized composite resin fibreglass posts on the mechanics of restored treated teeth.

AIM: To evaluate the mechanical behaviour of the dentine/cement/post interface of a maxillary central incisor using the finite element method and to compare the stresses exerted using conventional or customized post cementation techniques. METHODOLOGY: Four models of a maxillary central incisor were created using fibreglass posts cemented with several techniques: FGP1, a 1-mm-diameter conventionally cemented post; CFGP1, a 1-mm-diameter customized composite resin post; FGP2, a 2-mm-diameter conventionally cemented post; CFGP2, a 2-mm-diameter customized composite resin post. A distributed load of 1N was applied to the lingual aspect of the tooth at 45° to its long axis. Additionally, polymerization shrinkage of 1% was simulated for the resin cement. The surface of the periodontal ligament was fixed in the three axes (X =Y = Z = 0). The maximum principal stress (σ(max) ), minimum principal stress (σ(min)), equivalent von Mises stress (σ(vM) ) and shear stress (σ(shear)) were calculated for the dentine/cement/post interface using finite element software. RESULTS: The peak of σ(max) for the cement layer occurred first in CFGP1 (1.77 MPa), followed by CFGP2 (0.99), FGP2 (0.44) and FGP1 (0.2). The shrinkage stress (σ(vM) ) of the cement layer occurred as follows: FGP1 (35 MPa), FGP2 (34), CFGP1 (30.7) and CFGP2 (30.1). CONCLUSIONS: Under incisal loading, the cement layer of customized posts had higher stress concentrations. The conventional posts showed higher stress because of polymerization shrinkage.

Optical scattering power for characterization of mineral loss.

Mineral loss in early caries cannot be measured without invasive procedures. To quantify mineral loss without sectioning the tooth, one must determine the optical scattering of the enamel. Using enamel white-spot lesions, we hypothesize that the optical scattering power (Sp) of the demineralized enamel would provide a quantitative estimate of mineral loss. Enamel slabs were demineralized to produce artificial white spots. The data were acquired by means of a Charge-Coupled Device (CCD) camera and image-processing software. For the purpose of comparison, mineral loss (deltaZ) of the demineralized samples was determined by the use of a microhardness approach after the samples were sectioned. The scattering power correlated well with deltaZ (r2 = 0.82). In contrast, simple reflectance of the demineralized samples correlated poorly with deltaZ (r2 = 0.22). The validity of using scattering power to measure demineralization has been confirmed by a three-dimensional Monte Carlo Simulation.

Helical axis errors affect computer-generated occlusal contacts.

A helical axis describing mandibular motion can be calculated from two distinct positions of the mandible; however, as these positions come closer together, calculation errors increase. This study investigated the effects of errors in the calculated helical axis on simulated mandibular motion by the measurement of changes in occlusal contacts. A standard helical axis was calculated from a simulated lateral movement. A series of digital interocclusal records from centric to a 5 degree mandibular rotation about the standard helical axis was created. Digital dental cast models were aligned to the interocclusal records. Helical axis parameters and occlusal contacts calculated with the use of the aligned digital models were compared with those of the standard. Helical axes calculated from mandibular positions separated by 1.5 degrees to 5.0 degrees yielded equivalent occlusal contacts. Qualitatively, contacts for helical axes calculated from jaw rotations of 0.7 degrees or larger were nearly identical to those of the standard.

Accuracy of a system for creating 3D computer models of dental arches.

Three-dimensional imaging of dental tissues will have a major impact in dentistry if the images are accurate. The purpose of this study was to measure the accuracy and precision of a system for creating three-dimensional images of dental arches. Using vinyl polysiloxane impression materials and improved dental stone, we made 10 stone casts of a "dental" standard with known dimensions. The impressions and casts were scanned by means of a Comet 100 optical scanner. Custom software created three-dimensional images (computer models) from the scanned data. Accuracy was defined as the average of the absolute differences between the computer models and the standard. Precision was the standard deviation of accuracy over 10 repeated measures. Software processing improved the accuracy of the scanner data. Accuracy +/- precision for the casts and impressions was 0.024 +/- 0.002 mm and 0.013 +/- 0.003 mm, respectively. The system produced computer models with sufficient accuracy for clinical application.

Effects of implant healing time on crestal bone loss of a controlled-load dental implant.

The universally accepted concept of delay-loaded dental implants has recently been challenged. This study hypothesizes that early loading (decreased implant healing time) leads to increased bone formation and decreased crestal bone loss. We used 17 minipigs to study implants under a controlled load, with non-loaded implants for comparison. Radiographic and histological assessments were made of the osseointegrated bone changes for 3 healing times (between implant insertion and loading), following 5 months of loading. The effect of loading on crestal bone loss depended on the healing time. Early loading preserved the most crestal bone. Delayed loading had significantly more crestal bone loss compared with the non-loaded controls (2.4 mm vs. 0.64 mm; P < 0.05). The histological assessment and biomechanical analyses of the healing bone suggested that loading and bioactivities of osteoblasts exert a synergistic effect on osseointegration that is likely to support the hypothesis that early loading produces more favorable osseointegration.

Pacing may not prevent neurocardiogenic syncope: the importance of correct diagnosis.

A 28-year-old female with frequent attacks of syncope showed high degree atrioventricular (AV) block in Holter's electrocardiographic monitoring. A permanent pacemaker (VVIR) was implanted. However, the syncope recurred despite the normally-functioning pacemaker. The syncope associated with hypotension and bradycardia was reproduced by upright posture for 8 min. This neurocardiogenic syncope was prevented by propranolol (30 mg/day). Neurocardiogenic syncope should be ruled out before pacemaker implantation in patients with syncope, particularly in young adults with no apparent symptom/electrocardiography correlation.

Elasticity of alveolar bone near dental implant-bone interfaces after one month's healing.

Information is scarce about Young's modulus of healing bone surrounding an implant. The purpose of this preliminary study is to quantify elastic properties of pig alveolar bone that has healed for 1 month around titanium threaded dental implants, using the nanoindentation method. Two 2-year-old Sinclair miniswine were used for the study. Nanoindentation tests perpendicular to the bucco-lingual cross section were performed on harvested implant-bone blocks using the Hysitron TriboScope III. Nomarski differential interference contrast microscopy was used to identify pyramidal indentation measurements that were from bone. Reduced moduli, averaged for all anatomical regions, were found to start low (6.17 GPa) at the interface and gradually increase (slope=0.014) to a distance of 150 microm (7.89 GPa) from the implant surface, and then flatten to a slope of 0.001 from 150 to 1500 microm (10.13 GPa). Mean reduced modulus and its relationship to distance did not differ significantly by anatomic location (e.g., coronal, middle, and apical third; P>/=0.28 for all relevant tests) at 1 month after implantation.

Local capsaicin application to the stellate ganglion and stellatectomy attenuate neurogenic inflammation in rat bronchi.

The present study investigated the contributions of vagal and nonvagal sensory nerve fibers on neurogenic inflammation in rat bronchial airways. A surgical procedure was developed via the rat mediastinum ventral intercostal space to prepare an intercostal opening without causing pneumothorax for performing stellate ganglionectomy alone, thoracic vagus nerve section alone, and stellatectomy plus thoracic vagotomy, and for injecting capsaicin (2 microl, 10 mg/ml) and 6-hydroxydopamine (2 microl, 50 mg/ml) into the ganglion. One week later in our procedure, we investigated if neurogenic inflammation induced by an intravenous injection of capsaicin (300 nmol/ml/kg) and innervation density of substance P-immunoreactive sensory axons could be decreased after chronic denervation in the rat lower airways. The major findings were that surgical removal of the right stellate ganglion and local capsaicin application resulted in a significant attenuation of neurogenic plasma extravasation in the right bronchial tree evoked by systemic capsaicin application. Reduction of neurogenic plasma extravasation was totally abolished by combined stellatectomy and thoracic vagotomy. The number of substance P-containing axons was also greatly decreased following these surgical and capsaicin treatments. It is concluded that sensory nerve fibers from both vagal source and nonvagal (spinal) source, which associated with the stellate ganglion, contributed significantly to neurogenic inflammation in the bronchial airways with a slightly higher contribution from the vagus nerve.

New organosilicon maxillofacial prosthetic materials.

OBJECTIVES: The silicone elastomer A-2186 is a widely used maxillofacial prosthetic material. It is a pourable two-component silicone rubber cured by a platinum catalyst. Used as a prosthetic material, A-2186 has short working time and because of its hydrophobic nature, poor adhesion to non-silicone based adhesives. The purpose of this study is to evaluate the physical properties of new prosthetic materials based on methacryloxypropyl-terminated polydimethylsiloxane (MPDS-MF), and to compare the properties with those of A-2186. METHODS: Hardness, tensile strength, ultimate elongation, tear strength and adhesive bonding strength of MPDS-MF and A-2186 with and without additives were determined and compared. The bonding strengths of the extrinsic colorant carrier with the prosthetic materials were also determined. Statistical analyses were done using a two-way analysis of variance (ANOVA). For significant effects, post-hoc tests were done using the Bonferroni correction. RESULTS: The hardness of MPDS-MF is similar to A-2186. However, tensile strength, tear strength, ultimate elongation, and adhesive bonding strength of MPDS-MF are higher than those of A-2186. SIGNIFICANCE: MPDS-MF is cured by free radical thermal polymerization and crosslinking. The working time of MPDS-MF, unlike A-2186, is long. The presence of methacrylate groups in MPDS-MF enhances its adhesion to non-silicone based adhesive. Based on the present study, it appears that MPDS-MF is suitable for use in fabricating of clinical prostheses.

Multiresolution registration of coronary artery image sequences.

Registration of coronary arterial images taken at different times is very important for obtaining better visibility of differences between sequential images. A typical image registration algorithm often employs a similarity measure to detect the differences generated from the relative motion or gray level changes between these images. Although a number of image registration approaches have been proposed to resolve the registration problem of digital angiography, they are either computationally expensive or not very robust in the application to practical images. This paper presents a feature-based sum of absolute values of difference (SAVD) using a coarse-to-fine strategy. The proposed algorithm was demonstrated to be capable to automatically registering the arterial structures in the areas of interest selected from a pair of sequential images as well as providing fractional pixel precision in registration. Compared to other existing methods, the algorithm improves the speed and the reliability of registration when a pair of coronary arterial images are acquired at the same or almost the same phase of cardiac motion.

Three-dimensional reconstruction of biliary tract from biplane projections.

Over the past few years, very little has been done in the area of 3-D reconstruction of the bile duct. Since the system in use for 3-D visualization of the biliary tree is built by surgical or autopsy materials, it generally cannot be applied to clinical diagnosis. In this paper, an algorithm for three-dimensional reconstruction of the biliary tree from two mutually orthogonal is presented to provide accurate and reproducible 3-D information of the biliary tree structure. It has been proven to be useful in diagnosis prior to operation or non-surgical treatment, particularly, obstructive stones can be visualized by using a transparency technique. As experiments demonstrated, the proposed method can be used as a useful tool for the visualization of 3-D structure of biliary tree in clinical applications.

Stain removal efficacy: an in vitro evaluation using quantitative image analysis.

OBJECTIVE: This study developed a computer image analysis technique as a quantitative means to measure changes in dental stain after brushing with various dentifrices. METHOD AND MATERIALS: Enamel specimens with naturally occurring mature stain were cut from bovine incisors. The specimens were subjected to in vitro toothbrushing with one of the four tested groups, consisting of two dentifrices that make claims of stain removal (Aquafresh Whitening and Rembrandt Sensitive), a regular dentifrice, (Aquafresh Triple Protection), and water. Digital images of stain specimens were recorded under standardized lighting conditions and analyzed with an image analysis software. The area-intensity stain determinant, which accounted for the reflected intensity and the corresponding areas of stain, was computed. Stain removal efficacy was calculated based on the difference in area-intensity stain determinant before and after brushing. RESULTS: Brushing with any of the tested dentifrices removed more stain than did brushing with water alone. The finding that brushing with a regular dentifrice resulted in higher stain removal efficacy than brushing with water seems to indicate a role for abrasivity. Aquafresh Whitening had a higher stain removal efficacy than did Rembrandt for the removal of mature calcified stain used in this study. However, there were certain stains that none of the dentifrices removed. CONCLUSION: Computer image analysis provides an objective and quantitative measurement to distinguish in vitro stain removal efficacy of dentifrices.

Micromechanics of implant/tissue interfaces.

A series of finite element models was developed for evaluation of the micromechanics of implant/tissue interfaces. Conventional finite element global models of a dental implant, assuming a continuum implant/bone interface, were developed so that general stress patterns in the implant and surrounding tissue could be obtained. Stresses in bone were concentrated on the alveolar crest and apex region for all global models having a direct bone/implant contact. The addition of a 100-microns-thick layer of fibrous tissue into the bone/implant interface concentrated the stresses in the middle third of the bone adjacent to the implant surface. Stresses in the middle third were ten times higher than in the cases without fibrous tissue. Interfaces modeled under the assumption of a volume-weighted average material stiffness of bone tissue and metal confirmed these general stress patterns, but provided no stress details of the interfacial zone. Finally, the equivalent material constants of the interfacial zone with and without fibrous tissue were calculated by homogenization theory. From these equivalent constants, local strains around single threads were calculated. These equivalent material properties are sensitive to the microstructure. Therefore, it is now possible for stress patterns within the interfacial zone to be quantified and the local micromechanical behavior around individual surface structures for whole implants accounted for.

Recombinant biglycan promotes bone morphogenetic protein-induced osteogenesis.

The aim of this study was to determine the effects of glutathione-S-transferase-fused recombinant biglycan (GST-BGN) on craniofacial bone regeneration. We recently demonstrated a positive effect of tissue-derived BGN on bone morphogenetic protein 2 (BMP-2) function, which is exerted likely via the BGN core protein. Here, we investigated the effects of GST-BGN lacking any posttranslational modifications on BMP-2 function in vitro and in vivo. In the C2C12 cell culture system, BMP-2-induced Smad 1/5/8 phosphorylation and alkaline phosphatase activity were both enhanced by the addition of GST-BGN. For the in vivo effect, we employed a Sprague-Dawley rat mandible defect model utilizing 1 µg (optimal) or 0.1 µg (suboptimal) of BMP-2 combined with 0, 2, 4, or 8 µg of GST-BGN. At 2 weeks post-surgery, newly formed bone was evaluated by microcomputed tomography and histologic analyses. The results revealed that the greatest amounts of bone within the defect were formed in the groups of suboptimal BMP-2 combined with 4 or 8 µg of GST-BGN. Also, bone was well organized versus that formed by the optimal dose of BMP. These results indicate that recombinant BGN is an efficient substrate to promote low-dose BMP-induced osteogenesis.

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber.

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.