Fatigue life prediction considering variability for additively manufactured pure titanium clasps

PURPOSE

This study aims to develop a numerical prediction method for the average and standard deviation values of the largely varied fatigue life of additively manufactured commercially pure titanium (CPTi grade 2) clasps. Accordingly, the proposed method is validated by applying it to clasps of different shapes.

METHODS

The Smith-Watson-Topper (SWT) equation and finite element analysis (FEA) were used to predict the average fatigue life. The variability was expressed by a 95% reliability range envelope based on the experimentally determined standard deviation.

RESULTS

When predicting the average fatigue life, the previously determined fatigue parameters implemented in the SWT equation were found to be useful after conducting fatigue tests using a displacement-controlled fatigue testing machine. The standard deviation with respect to stroke and fatigue life was determined for each clasp type to predict variability. The proposed prediction method effectively covered the experimental data. Subsequently, the prediction method was applied to clasps of different shapes and validated through fatigue tests using 22 specimens. Finally, the fracture surface was observed using scanning electron microscopy (SEM). Many manufacturing process-induced defects were observed; however, only the surface defects where the maximum tensile stress occurred were crucial.

CONCLUSIONS

It was confirmed that the fatigue life of additively manufactured pure titanium parts is predictable before the manufacturing process considering its variability by performing only static elasto-plastic FEA. This outcome contributes to the quality assurance of patient-specific clasps without any experimental investigation, reducing total costs and response time.

Contrast-enhanced computed tomography of retromandibular vein position and course patterns relative to the mandible during sagittal split ramus osteotomy

Background

Sagittal split ramus osteotomy is an established procedure used in oral and maxillofacial surgery. Major bleeding is representative intraoperative complication involves vessels such as the inferior alveolar, facial, and maxillary arteries and accompanying veins, in particular the retromandibular vein (RMV). We previously described the RMV course patterns using embalmed cadavers. However, owing to the possible influence of formalin fixation and unclear skeletal classification of the jaws, the present study aimed to use contrast-enhanced computed tomography to confirm the RMV in patients with defined jaw deformities.

Methods

Twenty patients with orthognathic jaw deformities (40 sides) were included. The RMV and the lateral and posterior views of the mandible were evaluated using contrast-enhanced computed tomography. Course patterns and RMV positions were classified as previously reported.

Results

Three patterns were identified in the lateral view. Type A: RMV posterior to the posterior border of the ramus (n=25; 62.5%). Type B: adjoining the posterior border of the ramus (n=12; 30.0%). Type C: anterior to the posterior border of the ramus (n=3; 7.5%). Five course patterns were identified in the posterior view. Pattern I: rectilinear course running medial to the posterior border of the ramus (n=3; 7.5%). Pattern II: diagonal course running medially from immediately posterior to posterior border of the ramus (n=11; 27.5%). Pattern III: rectilinear course running immediately posterior to the posterior border of the ramus (n=12; 30.0%). Pattern IV: diagonal course running from lateral to medial relative to the posterior border of the ramus (n=8; 20.0%). Pattern V: diagonal course running from lateral to immediately posterior relative to the posterior border of the ramus (n=6; 15.0%). In the no-course pattern group, the RMV inferior to the lingula was lateral to its position and superior to that of the lingula. In half of the cases, the left and right sides exhibited different running patterns. We observed no correlation between the skeletal patterns of jaw deformities and the course of the RMV.

Conclusions

Type B/Pattern II that runs in a straight line bordering the posterior margin of the ramus requires the most attention during surgery. These findings suggest the possibility of predicting intraoperative bleeding risk.

Comparison of the fatigue life of pure titanium and titanium alloy clasps manufactured by laser powder bed fusion and its prediction before manufacturing

PURPOSE

In this study, the fatigue properties of additively manufactured titanium clasps were compared with those of commercially pure titanium (CPTi) and Ti-6Al-4V (Ti64), manufactured using laser powder-bed fusion.

METHODS

Fourteen specimens of each material were tested under the cyclic condition at 1 Hz with applied maximum strokes ranging from 0.2 to 0.5 mm, using a small stroke fatigue testing machine. A numerical approach using finite element analysis (FEA) was also developed to predict the fatigue life of the clasps.

RESULTS

The results showed that although no significant differences were observed between the two materials when a stroke larger than 0.35 mm was applied, CPTi had a better fatigue life under a stroke smaller than 0.33 mm. The distributions of the maximum principal stress in the FEA and the fractured position in the experiment were in good agreement.

CONCLUSIONS

Using a design of the clasp of the present study, the advantage of the CPTi clasp in its fatigue life under a stroke smaller than 0.33 mm was revealed experimentally. Furthermore, the numerical approach using FEA employing calibrated parameters for the Smith-Watson-Topper method are presented. Under the limitations of the aforementioned clasp design, the establishment of a numerical method enabled us to predict the fatigue life and ensure the quality of the design phase before manufacturing.

Clinical Application of Inferior Alveolar Nerve Block Device for Safe and Secure IANB by Any Operator

The inferior alveolar nerve block (IANB) is an established technique with a success rate of 60-80%; however, large errors have been reported among operators. Some dentists do not prefer to use IANB because of the risk of complications. Nevertheless, it is a useful technique for pain control, and a secure IANB offers significant benefits to operators and patients. This case series study aimed to investigate the efficacy of the "IANB Device," a nerve block guide for IANB, and the adverse events associated with its use in clinical practice. IANB was performed using the device on five patients who had undergone detailed computed tomography examination for chronic orofacial pain in the third division of the trigeminal nerve. Lidocaine 1% (1 mL, no adrenaline added) was used as the local anesthetic. IANB was performed by three dentists with 2, 5, and 11 years of experience in orofacial pain treatment. Thus, the data were collected in triplicate for each patient. The primary endpoints were whether adjustment of the IANB device was required, changes in the sensation threshold of the lower lip, the time to disappearance of pain, the presence or absence of tongue sensation ("Do you have numbness in your tongue?": "Yes/No"), and discomfort (visual analog scale). The incidence of any other adverse events was recorded. The procedure was judged to be successful if the pain disappeared and an elevation in the sensation threshold of the lower lip was observed. Adjustment of the IANB device was not required in any patient. A significant elevation in the sensation threshold of the lower lip and the disappearance of pain were observed in all patients. Three of the five patients reported experiencing tongue numbness. Discomfort with the use of the IANB device was less than 30 mm on the visual analog scale. No notable complications were observed. The appropriate type, concentration, and dosage of the local anesthetic must be considered during general dental treatment and oral surgical procedures. Our findings suggest that the IANB device is useful for eliminating errors between operators, enhancing safety, and improving the success rate.

Digital technology for fabrication of removable dental prosthesis with double crowns combining fiber-reinforced composite and zirconia

PATIENTS

This clinical report describes the process for fabricating a double-crown-retained removable dental prosthesis combining a fiber-reinforced composite and zirconia using digital technology. An 83-year-old woman presented with gingival swelling around the maxillary right premolar. The swollen tooth was the abutment tooth of a cross-arch fixed partial denture. An intraoral scanner (IOS) and computer-aided design/manufacturing as digital technology were used to plan treatment with a double-crown-retained removable dental prosthesis. A metal-free prosthesis using zirconia for the primary crown and fiberglass-reinforced composite resin for the secondary crown was planned, and the patient consented to the treatment plan. After autotransplantation of a tooth as one of the abutments, the IOS was used to obtain digital scans of the prepared surface of the abutment teeth, opposing dentition, and occlusal relationships. First, primary crowns were milled using zirconia. Next, the intraoral scanner obtained a pick-up impression of the primary crowns, and secondary crowns were designed and milled from the fiber-reinforced composite. After delivery, the patient expressed satisfaction with the functionality, esthetics, and fit of the double-crown-retained removable dental prosthesis.

DISCUSSION

Digital technology offers many advantages such as efficient fabrication of double crowns, reduced material costs, improved biocompatibility, and good aesthetics of metal-free materials.

CONCLUSION

This clinical report describes the application of digital technology for the fabrication of a double-crown-retained removable dental prosthesis combining a fiber-reinforced composite and zirconia, resulting in patient satisfaction.

Osteotomy training for dental students using three-dimensional simulation software and maxillofacial three-dimensional-printed models

PURPOSE/OBJECTIVES

Simulated educational models of teeth, bones, and gums have been used for a long time in procedural skills training in dentistry.  The advent of three-dimensional (3D) printing technologies and additive manufacturing has facilitated the production of more advanced 3D printed models that can be utilized for surgical and dental training together with other technologies (e.g., 3D scanners and image analysis software).

METHODS

We conducted training on osteotomy in the maxilla and mandible using maxillofacial simulation software (MSS) and a 3D-printed model for 5th-year undergraduate dental students (13 students in 2017 and 11 students in 2018 with more than half of their results). We compared the group (13 students) who performed osteotomy after participating in the simulation lecture with those (11 students) who performed osteotomy after performing self-simulation (they were instructed to bring their personal computers and install the MSS) using tests and questionnaires (pre- and post-curriculum).

RESULTS

The average test score was significantly higher in the group who performed osteotomy using the 3D-printed model after performing self-simulation; participants in this group had acquired a better understanding of the surgical procedure. Comparison using questionnaires showed a significant difference in the students' understanding of instruments and surgical techniques between both groups.

CONCLUSION

The MSS and 3D printed models are widely used clinically. Incorporating these in the curriculum will help accelerate student development. In addition, prompt education on the purpose and usefulness of these tools will not only facilitate simulation software and 3D-printed model-based treatment plan in the clinic but also promote further research.

Comparative Study of Morphology and Distribution of Valves in Human Retromandibular Vein

The objective of this study was to analyze the distribution and morphology of the valves in the human retromandibular vein. The retromandibular, internal thoracic, azygos, femoral, and brachial veins were harvested from 46 cadavers donated to the Department of Anatomy at Tokyo Dental College for dissection. The frequency of the valves in each vein, the length of the cusps, and the thickness of the vein itself were measured. Valves were present at high frequency (92.1%) in the veins of the limbs and had cusps at least twice as long as the internal diameter of the vein. Veins in the trunk contained a lower frequency of valves, with cusps that tended to be shorter (1.60±0.77) than those of the venous valves in the limbs (2.12±0.60). The valves of the retromandibular vein tended to resemble venous valves in the trunk in terms of both frequency and morphology. The main function of venous valves in the limbs is to prevent retrograde flow. Conversely, valves in the veins of the trunk and retromandibular vein play a role in retaining blood in the veins, and their relationship to other veins means that they can cause major hemorrhage.

Mixed reality and three dimensional printed models for resection of maxillary tumor: a case report

In the field of oral and maxillofacial surgery, many institutions have recently begun using three-dimensional printers to create three-dimensional models and mixed reality in a variety of diseases. Here, we report the actual situation model which we made using three-dimensional printer from virtual operation data and the resection that was performed while grasping a maxillary benign tumor and neighboring three-dimensional structure by designing an application for Microsoft® HoloLens, and using Mixed Reality surgery support during the procedure.

Accuracy of 3D printing compared with milling - A multi-center analysis of try-in dentures

OBJECTIVES

In recent years, computer-aided design/computer-aided manufacturing (CAD/CAM) has been used to produce removable complete dentures. Most workflows include fabrication of milled or 3D-printed try-in prostheses. 3D-printing accuracy is affected by laboratory-specific and operator-dependent factors. This international five-center study sought to compare the accuracy of 3D-printed and milled try-in dentures.

METHODS

The construction file of a maxillary removable complete denture was selected as a reference. Eight try-in dentures were 3D printed at each of the five centers. Each center used their own printer (Objet260 Connex, Stratasys; MAX, Asiga; Anycubic Photon, Anycubic 3D; PRO2, Asiga and cara Print 4.0, Kulzer) along with their own material, printing settings, post-processing and light-curing parameters. At center 2, eight try-in dentures were milled to serve as a benchmark (PrograMill PM7, Ivoclar Vivadent). Dentures were scanned and aligned to the reference file using best-fit algorithms. Geometric accuracy was analyzed using the root mean square value (trueness) and standard deviation (precision) of the distributed absolute mesh deviations. Mean values of the five sets of printed dentures and the single set of milled dentures were compared.

RESULTS

Milled dentures showed a mean trueness of 65 ± 6 μm and a mean precision of 48 ± 5 μm. Thus, they were significantly more accurate than the 3D-printed dentures in four out of five centers. In mean absolute numbers, 3D printing was less true than milling by 17-89 μm and less precise by 8-66 μm.

CONCLUSIONS

Although milling remains the benchmark technique for accuracy, differences between milled and 3D-printed dentures were non-significant for one printing center. Furthermore, the overall performance of 3D printing at all centers was within a clinically acceptable range for try-in prostheses.

CLINICAL SIGNIFICANCE

The accuracy of 3D printing varies widely between and within laboratories but nonetheless lies within the range of accuracy of conventional manufacturing methods.

Comparison of artificial tooth position in dentures fabricated by heat curing and additive manufacturing

BACKGROUND

The purpose of this study was to compare the displacement of tooth arrangement in dentures fabricated by additive manufacturing (AM) and heat curing.

METHODS

Three-dimensional (3D) scanning was performed for edentulous jaw models. After the teeth were arranged, 3D scanning for the wax denture was performed. Heat-cured dentures were fabricated with heat-cure polymer resin. Based on data obtained by subtracting the model data from wax denture data, AM dentures were fabricated from ultraviolet-cured acrylic resin. Accuracy was verified by superimposing heat-cured and AM dentures on the tooth region data from the wax dentures and measuring displacement of the tooth arrangement.

RESULTS

In the maxillary dentures, the amount of tooth displacement for the heat-cured dentures and for the AM dentures ranged from -0.08 to +0.06 mm and from -0.25 to +0.06 mm respectively. A significant difference was observed between two dentures. In the mandibular dentures, the amount of tooth displacement for the heat-cured dentures and for the AM dentures ranged from -0.09 to +0.07 mm and from -0.03 to +0.07 mm respectively. No significant difference was observed between two dentures.

CONCLUSIONS

The artificial teeth of the maxillary dentures fabricated by AM showed a greater displacement compared to those by heat curing.

A safe, stable, and convenient three-dimensional device for high Le Fort I osteotomy

BACKGROUND

Le Fort I osteotomy is a highly effective treatment for skeletal jaw deformities and is commonly performed. High Le Fort I osteotomy is a modified surgical procedure performed for improving the depression of the cheeks by setting the osteotomy higher than the conventional Le Fort I osteotomy. Developments in three-dimensional (3D) technology have popularized the use of 3D printers in various institutions, especially in orthognathic surgeries. In this study, we report a safe and inexpensive method of performing a high Le Fort I osteotomy using a novel 3D device and piezosurgery, which prevent tooth root injury without disturbing the operation field for patients with a short midface and long tooth roots.

RESULTS

A 17-year-old woman presented with facial asymmetry, mandibular protrusion, a short midface, and long tooth roots. We planned high Le Fort I osteotomy and bilateral sagittal split ramus osteotomy. Prevention of damage to the roots of the teeth and the infraorbital nerve and accurate determination of the posterior osteotomy line were crucial for clinical success. Le Fort I osteotomy using 3D devices has been reported previously but were particularly large in size for this case. Additionally, setting the fixing screw of the device was difficult, because of the risk of damage to the roots of the teeth. Therefore, a different surgical technique, other than the conventional Le Fort I osteotomy and 3D device, was required. The left and right parts of the 3D device were fabricated separately, to prevent any interference in the surgical field. Further, the 3D device was designed to accurately cover the bone surface from the piriform aperture to the infra-zygomatic crest with two fixation points (the anterior nasal spine and the piriform aperture), which ensured stabilization of the 3D device. The device is thin and does not interfere with the surgical field. Safe and accurate surgical performance is possible using this device and piezosurgery. The roots of the teeth and the infraorbital nerve were unharmed during the surgery.

CONCLUSIONS

This device is considerably smaller than conventional devices and is a simple, low-cost, and efficient method for performing accurate high Le Fort I osteotomy.

Accuracy of Le Fort I osteotomy with combined computer-aided design/computer-aided manufacturing technology and mixed reality

The aim of this study was to verify the reproducibility and accuracy of preoperative planning in maxilla repositioning surgery performed with the use of computer-aided design/manufacturing technologies and mixed reality surgical navigation, using new registration markers and the HoloLens headset. Eighteen patients with a mean age of 26.0 years were included. Postoperative evaluations were conducted by comparing the preoperative virtual operation three-dimensional image (Tv) with the 1-month postoperative computed tomography image (T₁). The three-dimensional surface analysis errors ranged from 79.9% to 97.1%, with an average error of 90.3%. In the point-based analysis, the errors at each point on the XYZ axes were calculated for Tv and T₁ in all cases. The median signed value deviation of all calculated points on the XYZ axes was -0.03mm (range -2.93mm to 3.93mm). The median absolute value deviation of all calculated points on the XYZ axes was 0.38mm (range 0mm to 3.93mm). There were no statistically significant differences between any of the points on any of the axes. These values indicate that the method used was able to reproduce the maxilla position with high accuracy.

Course of the Maxillary Vein and its Positional Relationship With the Mandibular Ramus Require Attention During Mandibuloplasty

PURPOSE

The maxillary vein is associated with major hemorrhage, an intraoperative risk factor during mandibuloplasty. Our objectives in this study were to identify the anatomical course of the maxillary vein relative to the mandible, and to ascertain the relationship of its course with that of the maxillary artery.

METHODS

Thirteen sides of 13 cadavers in the possession of the Department of Anatomy of Tokyo Dental College were used. The maxillofacial region was first dissected, after which the upper part of the mandibular ramus was removed and the maxillary artery, maxillary vein, and pterygoid venous plexus were identified. The length of the maxillary vein and its height from the mandibular plane were then measured, and its anatomical course was recorded.

RESULTS

The maxillary vein ran downward along the inner aspect of the temporal muscle, then from the base of the coronoid process it ran horizontally near the bone surface of the inner aspect of the mandibular ramus. After joining the inferior alveolar vein, it joined the superficial temporal vein to form the retromandibular vein. The mean length of the maxillary vein was 22.2 ± 3.2 mm. At the posterior margin of the mandibular ramus, its mean height above the mandibular plane was 34.2 ± 5.4 mm. From the posterior margin of the mandibular ramus to the lowest point of the mandibular notch, the maxillary vein was located within the areolar connective tissue directly above the periosteum adjoining the inner aspect of the mandibular ramus.

CONCLUSIONS

In the wide area from the center of the maxillary notch to the posterior margin of the mandibular ramus, the maxillary vein runs extremely close to the periosteum on the inner aspect of the mandibular ramus, suggesting that it may pose a risk of hemorrhage in various oral surgical procedures.

Relationship between the immunohistological examination and fluorescence visualization of oral squamous cell carcinoma

Disorders of the oral mucosa are considered easy to diagnose since they can be visualized and examined directly. A change in the color of the oral mucosa reflects histopathological changes and is an important diagnostic parameter. However, the subjective perception of color varies. To determine the extent of resection for oral mucosa conditions, it is necessary to digitize the color and perform objective assessments. In recent years, fluorescence visualization devices and analysis software that measure tissue luminance G have been employed for the identification of oral mucosa diseases. Fluorescence visualization is presumably based on the decrease in epithelial flavin adenine dinucleotide content and luminance G values due to the destruction of collagen cross-links [fluorescence visualization loss (FVL)]. However, cases with differences between luminance values and histopathological presentation exist. Therefore, additional factors may affect fluorescence visualization. The present study used a portable, non-contact oral mucosa fluorescence visualization device for luminance measurements in seven patients with oral squamous cell carcinoma. Furthermore, Picro-Sirius Red and immunohistochemical staining were performed for CK13, CK17, Ki67, p53 and E-cadherin in the FVL(+) (lesion) and FVL(−) (resection stump) areas to elucidate the principle of fluorescence visualization. Fluorescence was significantly lower in the FVL(+) than in the FVL(−) areas, and the mean luminance G value was 56. The Picro-Sirius Red stain revealed collagen destruction in the FVL(+) areas but no collagen disruption in the FVL(−) areas. CK13 was negative in the FVL(+) and positive in the FVL(−) areas, whereas the opposite pattern was observed for CK17. In the FVL(+) area, p53 staining was positive. E-cadherin expression was enhanced in the FVL(−) areas and reduced in the FVL(+) areas. Furthermore, the luminance G value tended to be lower in cases with weaker E-cadherin staining. The aforementioned results suggest that decreased E-cadherin expression may be a factor that regulates fluorescence visualization.

Micro- and nano-bone analyses of the human mandible coronoid process and tendon-bone entheses

The coronoid process provides attachment to temporalis and masseter muscles, and thus plays an important role in mastication. Tendons connect muscles and bones, mediating the transmission of functional loads to bones. Thus, tendon-bone entheses govern mechanical stress in bones. The preferential orientation of biological apatite (BAp) crystallites, the main mineral component in bones, is an important index for bone quality and function, and is largely influenced by locally applied stress. In this study, we analyzed BAp orientation, Young's modulus, and bone mineral density (BMD) at different sites in the human coronoid process. No differences in BMD were found among the analyzed sites, but BAp crystal orientation was observed to differ. BAp crystallites showed a uni-directional orientation in the mesiodistal direction at the coronoid process apex, but were oriented in the direction vertical to the occlusal plane at other sites. Young's modulus tended to vary according to the BAp orientation. At the apex, a tendon form with characteristics different from those at other sites, including the presence of a fibrocartilaginous layer that may act as a stretching brake to control stress concentration, was observed. These findings suggest that the functional pressure of the temporalis muscle affects bone quality and strength.

Accuracy of Clasps Fabricated with Three Different CAD/CAM Technologies: Casting, Milling, and Selective Laser Sintering

PURPOSE

To compare the fabrication accuracy of clasps made using different CAD/CAM technologies.

MATERIALS AND METHODS

Five clasps were created using three CAD/CAM technologies: casting from a resin pattern using additive manufacturing; computer numerical controlled milling; and selective laser sintering (SLS). Differences between the scan data of the clasps and the CAD data were statistically analyzed.

RESULTS

There were significant differences in all parts of the clasps. The difference values were small overall for the SLS clasp.

CONCLUSION

This study demonstrated that SLS for clasp fabrication is outstanding in terms of fabrication accuracy and reproducibility.

Maxillary reconstruction using tunneling flap technique with 3D custom-made titanium mesh plate and particulate cancellous bone and marrow graft: a case report

Background

Reconstructive surgery is often required for tumors of the oral and maxillofacial region, irrespective of whether they are benign or malignant, the area involved, and the tumor size. Recently, three-dimensional (3D) models are increasingly used in reconstructive surgery. However, these models have rarely been adapted for the fabrication of custom-made reconstruction materials. In this report, we present a case of maxillary reconstruction using a laboratory-engineered, custom-made mesh plate from a 3D model.

Case presentation

The patient was a 56-year-old female, who had undergone maxillary resection in 2011 for intraoral squamous cell carcinoma that presented as a swelling of the anterior maxillary gingiva. Five years later, there was no recurrence of the malignant tumor and a maxillary reconstruction was planned. Computed tomography (CT) revealed a large bony defect in the dental-alveolar area of the anterior maxilla. Using the CT data, a 3D model of the maxilla was prepared, and the site of reconstruction determined. A custom-made mesh plate was fabricated using the 3D model (Okada Medical Supply, Tokyo, Japan). We performed the reconstruction using the custom-made titanium mesh plate and the particulate cancellous bone and marrow graft from her iliac bone. We employed the tunneling flap technique without alveolar crest incision, to prevent surgical wound dehiscence, mesh exposure, and alveolar bone loss. Ten months later, three dental implants were inserted in the graft. Before the final crown setting, we performed a gingivoplasty with palate mucosal graft. The patient has expressed total satisfaction with both the functional and esthetic outcomes of the procedure.

Conclusion

We have successfully performed a maxillary and dental reconstruction using a custom-made, pre-bent titanium mesh plate.

Novel condylar repositioning method for 3D-printed models

Background

Along with the advances in technology of three-dimensional (3D) printer, it became a possible to make more precise patient-specific 3D model in the various fields including oral and maxillofacial surgery. When creating 3D models of the mandible and maxilla, it is easier to make a single unit with a fused temporomandibular joint, though this results in poor operability of the model. However, while models created with a separate mandible and maxilla have operability, it can be difficult to fully restore the position of the condylar after simulation. The purpose of this study is to introduce and asses the novel condylar repositioning method in 3D model preoperational simulation.

Methods

Our novel condylar repositioning method is simple to apply two irregularities in 3D models. Three oral surgeons measured and evaluated one linear distance and two angles in 3D models.

Results

This study included two patients who underwent sagittal split ramus osteotomy (SSRO) and two benign tumor patients who underwent segmental mandibulectomy and immediate reconstruction. For each SSRO case, the mandibular condyles were designed to be convex and the glenoid cavities were designed to be concave. For the benign tumor cases, the margins on the resection side, including the joint portions, were designed to be convex, and the resection margin was designed to be concave. The distance from the mandibular ramus to the tip of the maxillary canine, the angle created by joining the inferior edge of the orbit to the tip of the maxillary canine and the ramus, the angle created by the lines from the base of the mentum to the endpoint of the condyle, and the angle between the most lateral point of the condyle and the most medial point of the condyle were measured before and after simulations. Near-complete matches were observed for all items measured before and after model simulations of surgery in all jaw deformity and reconstruction cases.

Conclusions

We demonstrated that 3D models manufactured using our method can be applied to simulations and fully restore the position of the condyle without the need for special devices.

Developmental characteristics of secondary cartilage in the mandibular condyle and sphenoid bone in mice

OBJECTIVE

Secondary cartilage develops from osteochondral progenitor cells. Hypertrophic chondrocytes in secondary cartilage increase within a very short time and then ossify rapidly. In the present study, we investigated the sequential development process of osteochondral progenitor cells, and the morphology and size of hypertrophic chondrocytes in secondary cartilage.

DESIGN

ICR mice at embryonic days (E) 14.5-17.5 were used. The mandibular condyle and the medial pterygoid process of the sphenoid bone were observed as secondary cartilage, and the cranial base and the lateral pterygoid process of the sphenoid bone, which is primary cartilage, were observed as a control. Thin sections were subjected to immunostaining and alkaline phosphatase (ALP) staining. Using a confocal laser microscope, 3D stereoscopic reconstruction of hypertrophic cells was performed. To evaluate the size of hypertrophic chondrocytes objectively, the cell size was measured in each cartilage.

RESULTS

Hypertrophic chondrocytes of secondary cartilage first expressed type X collagen (Col X) at E15.5. SRY-box 9 (Sox 9) and ALP were co-expressed in the fibroblastic/polymorphic tissue layer of secondary cartilage. This layer was very thick at E15.5, and then rapidly became thin. Hypertrophic cells in secondary cartilage were markedly smaller than those in primary cartilage.

CONCLUSIONS

The small hypertrophic cells present in secondary cartilage may have been a characteristic acquired in order for the cartilage to smoothly promote a marked increase in hypertrophic cells and rapid calcification.

Three-dimensional analysis of incisive canals in human dentulous and edentulous maxillary bones

Background

The purpose of this study was to reveal the structural properties that need to be considered in dental implant treatment by investigating differences between dentulous and edentulous maxillae in the three-dimensional (3D) microstructure of the incisive canals (ICs) and their surrounding bone.

Methods

A total of 40 maxillary bones comprising 20 dentulous maxillae and 20 edentulous maxillae were imaged by micro-CT for 3D observation and measurement of the IC and alveolar bone in the anterior region of the IC.

Results

The Y-morphology canal was most frequently observed at 60% in dentulous maxilla and 55% in edentulous maxilla. There was a significant difference between dentulous and edentulous maxillae in IC diameter and volume, but no significant difference between the two in the major axis of the ICs.

Conclusions

The anatomic structure surrounding the IC has limited area for implant placement. Therefore, where esthetic and long-term maintenance requirements are taken into account, careful attention is needed when setting the placement position. Also, due to the resorption of bone, edentulous maxillae have a different IC morphology from dentulous maxillae, and therefore, a cautious approach is required.

Reappearance of cardiac presynaptic sympathetic nerve terminals in the transplanted heart: correlation between PET using (11)C-hydroxyephedrine and invasively measured norepinephrine release

Previously, sympathetic reinnervation of the transplanted heart has been described using invasive catheterization techniques and noninvasive radionuclide imaging techniques. However, little is known about the agreement between these 2 methods. Thus, correlation between (11)C-hydroxyephedrine (HED) PET and invasively measured norepinephrine (NE) release was investigated in transplant recipients in this study.

METHODS

Using PET and the catecholamine analog HED, 17 patients were studied between 2 mo and 13.6 y after transplantation. Based on results in completely denervated hearts, areas with HED retention >7%/min were defined as reinnervated. Additionally, transcardiac NE release induced by intravenous tyramine (55 microg/kg) was measured by coronary sinus and aortic catheterization within 1 wk of the PET study. NE levels between coronary sinus and aortic root, DeltaNE(CS-AO), were calculated at baseline and after tyramine administration. Differences of more than 3 SD of baseline (>163 pg/mL) were interpreted as reinnervation.

RESULTS

HED retention indicated reinnervation in 10 patients. Maximal HED retention ranged from 4.3%/min to 16.4%/min. DeltaNE(CS-AO) 1 min after tyramine administration ranged between -10 pg/mL and 1157 pg/mL, and 8 patients were above the reinnervation threshold. Fisher's exact test demonstrated good agreement between results of PET and DeltaNE(CS-AO) measurements (P = 0.002). Maximal HED retention was also significantly correlated with NE release (r = 0.69; P = 0.001).

CONCLUSION

Results of invasively measured NE release and noninvasive (11)C-HED PET are well correlated. This study further supports the usefulness of PET as a noninvasive approach for detection of reappearance of catecholamine uptake sites after heart transplantation.

Efficient gene activation in cultured mammalian cells mediated by FLP recombinase-expressing recombinant adenovirus

A recombinant adenovirus (rAd) expressing Cre recombinase derived from bacteriophage P1 has already been extensively used for the conditional gene activation and inactivation strategies in mammalian systems. In this study, we generated AxCAFLP, a rAd expressing FLP recombinase derived from Saccharomyces cerevisiae and carried out quantitative comparisons with Cre-expressing rAd in both in vitro and in cultured cells to provide another efficient gene regulation system in mammalian cells. In the in vitro experiments, the relative recombination efficiency of FLP expressed in 293 cells infected with FLP-expressing rAd was approximately one-thirtieth that of Cre even at 30 degrees C, the optimum temperature for FLP activity, and was approximately one-ninetieth at 37 degrees C. Co-infection experiments in HeLa cells using a target rAd conditionally expressing LacZ under the control of FLP showed that an FLP-expressing rAd, infected at a multiplicity of infection (MOI) of 5, was able to activate the transgene in almost 100% of HeLa cells whereas the Cre-expressing rAd was sufficient at an MOI of 0.2. Since an MOI of 5 is ordinarily used in rAd experiments, these results showed that the FLP-expressing rAd is useful for gene activation strategies and is probably applicable to a sequential gene regulation system in combination with Cre-expressing rAd in mammalian cells.

Global and regional functional measurements with gated FDG PET in comparison with left ventriculography

The purpose of this study was to validate the measurement of global and regional left ventricular cardiac function with ECG-gated fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) by comparison with the corresponding indices from X-ray left ventriculography (LVG). Twenty-six patients (23 men, 3 women, mean age 60.4 years) underwent LVG and ECG-gated (eight frames/cycle) FDG-PET within an interval of 10.2+/-6.8 days. A volumetric sampling approach was used to obtain both global (EF: ejection fraction) and regional [%WT: relative regional count increase from end-diastolic (ED) to end-systolic (ES) phase] functional parameters. The gated PET parameters were compared with the corresponding findings of LVG in seven myocardial segments. EF(gated PET) and EF(LVG) did not differ significantly (30%+/-10% vs 32%+/-10%, P=NS). The two EF values correlated significantly, showing no significant systematic measurement bias [EF(gated PET) = 2.61+0.86 x EF(LVG), R=0.84, P<0.0001]. Inter- and intra-observer reproducibility for EF were R=0.95, P<0.0001 and R=0.92, P<0.0001, respectively. Regional function was evaluated with LVG in 144 myocardial segments comprising 35 normokinetic, 70 hypokinetic and 39 a/dyskinetic segments. Visual analysis of LVG and gated PET correlated significantly (P<0.001), with an overall concordance ratio of 58% (83/144, kappa=0.35). Gated PET overestimated the regional function in 27% (39/144) and underestimated it in 15% (22/144). %WT showed significant differences between each pair of groups (a/dyskinesis, 13.2%+/-9.3%; hypokinesis, 17.1%+/-8.8%; normokinesis, 21.8%+/-10.9%). Inter- and intra-observer reproducibility was significant for %WT (R=0.77, P<0.0001 and R=0.79, P<0.0001, respectively). In conclusion, gated FDG PET permits assessment of global left ventricular cardiac function. In addition, assessment of regional function is feasible using the visual or the quantitative parameters.

Role of relative myocardial perfusion reserve for evaluating stenosis severity in patients with single-vessel coronary artery disease using

A statistically significant correlation was observed between the severity of anatomic stenosis and coronary flow reserve in experimental animals. A similar correlation in human coronary artery disease (CAD) was shown using positron emission tomography (PET) and pharmacologic vasodilator stress. The present study tested whether the concept of relative myocardial perfusion reserve (MPR) might be superior to absolute MPR in correlating coronary stenosis determined by quantitative coronary arteriography in patients with single vessel CAD using [13N]ammonia and PET. The study group comprised 21 patients (62 +/-10 years old; 15 men, 6 women) with normal left ventricular function who underwent angioplasty for isolated left anterior descending coronary artery stenosis. Absolute MPR, the ratio of dipyridamole-induced hyperemic blood flow to baseline blood flow by [13N]ammonia PET, and relative MPR, the ratio of MPR in regions supplied by stenosed coronary arteries to MPR in remote regions, were measured before and 3 months after angioplasty. The percent diameter stenosis was also quantified on coronary arteriograms just before the angioplasty and again at 3 months after. The study found that absolute MPR (r=0.755; p<0.0001) and relative MPR (r=0.814; p<0.0001) were inversely and nonlinearly correlated with the percent stenosis on angiography. The fitting curve of the correlation between relative MPR and coronary stenosis on angiography was identical to that observed in animal models. Therefore, relative MPR measured by [13N]ammonia PET more accurately and specifically describes stenosis severity in patients with CAD compared with absolute MPR, probably because of its independence from hemodynamic variations and the effects of coronary risk factors.

Non-invasive assessment of the effect of cardiac sympathetic innervation on metabolism of the human heart

The role of cardiac sympathetic nerves in the regulation of myocardial metabolism is not well defined. Owing to the presence of incomplete reinnervation, heart transplant recipients provide a unique model to study the effects of efferent sympathetic innervation. Using this model, we sought to determine the influence of cardiac sympathetic signals on substrate utilisation and overall oxidative metabolism. In 21 transplant recipients, positron emission tomography was applied to determine sympathetic innervation with the noradrenaline analogue carbon11 hydroxyephedrine, oxidative metabolism with carbon11 acetate (n=14), and glucose utilisation with fluorine-18 fluorodeoxyglucose (n=7). The reinnervated area comprised 22% +/- 20% of the left ventricle. Oxidative metabolism was similar in denervated and reinnervated myocardium [0.06 +/- 0.01 vs 0.06 +/- 0.01/min for k(mono)], while glucose uptake was significantly higher in denervated myocardium (6.9 +/- 6.6 vs 6.0 +/- 6.2 micromol/min/100 g; P=0.03). Reinnervation mainly occurred in the territory of the left anterior descending artery, where retention of 11C-hydroxyephedrine (6.8 +/- 2.7%/min) was higher compared with territories of the left circumflex (4.1 +/- 1.7%/min; P<0.01) and right coronary (3.8 +/- 1.1%/min; P<0.01) arteries. Oxidative metabolism was similar in all three territories, but compared with the reinnervated territory of the left anterior descending artery (53% +/- 16% of maximum), relative FDG uptake was higher in territories of the left circumflex (76% +/- 6%, P<0.01) and right coronary (67% +/- 10%, P<0.05) arteries. Similar degrees of regional heterogeneity were not observed in normals. Thus, while overall energy production through oxidative metabolism remains unaffected, cardiac utilisation of glucose in the fasting state is increased in the absence of catecholamine uptake sites. Innervated myocardium, however, may preferentially utilise free fatty acids, suggesting a role for sympathetic tone in substrate utilisation.

Effects of disopyramide and verapamil on renal disposition and nephrotoxicity of cisplatin in rats

PURPOSE

The purpose of this study was to determine the effects of disopyramide and verapamil on the renal handling of cisplatin (CDDP) and nephrotoxicity in rats. The stereoselective effect of verapamil was also studied.

METHODS

CDDP was administered to rats by i.v. bolus injection or by infusion at a constant rate with or without concomitant administration of racemic disopyramide, racemic verapamil, or each verapamil enantiomer. The concentrations of CDDP in plasma and in the kidney and liver were determined by HPLC. In separate experiments, CDDP was administered as described above, and blood urea nitrogen (BUN) was monitored for 7 days.

RESULTS

The BUN level after administration of CDDP was significantly reduced by coadministration of either disopyramide or verapamil. Renal accumulation of CDDP was significantly reduced by these drugs, whereas accumulation into the liver was not significantly changed. The relationship between the BUN levels and the area under the curve of CDDP concentration in the kidney versus time (AUCk) was analyzed using a sigmoid Emax model; this showed that the reduced BUN levels were explained by the AUCk. Furthermore, verapamil showed stereoselective inhibition of the renal accumulation of CDDP.

CONCLUSIONS

The renal accumulation of CDDP was inhibited by disopyramide and verapamil, and this inhibition resulted in the amelioration of nephrotoxicity.

Discrepancy between brain magnetic fields elicited by pattern and luminance stimulations in the fovea: adequate stimulus positions and a measure of discrepancy

A conventional equivalent current dipole estimation provides one of the quantitative measures to evaluate the discrepancy between two single-dipole-like magnetic field patterns, though there is one problem; all stimulus positions in the visual field do not necessarily contribute to the generation of a single-dipole-like magnetic field. Another important problem occurs when the field pattern is complex and cannot be approximated by a dipole. This makes it difficult to evaluate the discrepancy between two magnetic field patterns by the dipole parameters. In this paper, we determined the stimulus positions adequate for generating single-dipole-like magnetic field patterns by evaluating the magnetic field's goodness-of-fit to the field generated by a single dipole. We propose to use a similarity (SIM) as a quantitative measure of the discrepancy between two complex magnetic field patterns. The SIM is defined as an angle between two magnetic field vectors. We evaluated the discrepancy between the 100 ms post-stimulus responses to pattern-reversal (Rv) stimulus, pattern-onset (Pat) stimulus, and luminance-onset (Lumi) stimulus. The following results were obtained: (1) Stimulation of some of the octants in the fovea, far from the vertical meridian, elicited a single-dipole-like magnetic field pattern at a latency of 100 ms, though stimulation of the central part of the fovea, and stimulation of the octants along the vertical meridian, did not elicit a single-dipole-like magnetic field pattern; (2) The discrepancy between responses was quantitatively evaluated by the SIM even if the field patterns were complex; (3) The SIM analysis showed that the discrepancy between the responses to the Rv and the Lumi stimuli, as well as that between the responses to the Pat and the Lumi stimuli, were greater than that between the responses to the Rv and the Pat stimuli.

Effects of epidermal growth factor on neonatal growth of rat intestines

The effects of epidermal growth factor (EGF) on neonatal intestines were examined in the rat. In 5-day-old rats, sucrase, trehalase, alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (gamma-GTP) activities in the small intestines were significantly increased after subcutaneous injection of EGF for 3 days (1 microgram/rat/day). gamma-GTP activity was also accelerated after oral EGF administration (2 micrograms/rat/day). Small intestines of 12-day-old rats injected with EGF for 10 days (1 microgram/rat/day) were significantly heavier than those of controls. These results suggest that EGF influences neonatal growth improving enlargement and functional development of their intestines.

Effects of epidermal growth factor on mouse fetal growth

The effects of epidermal growth factor (EGF) on fetal growth were examined in mice. EGF is synthesized in large amounts by the mouse submandibular glands. On the 18th day of gestation, the body weight of fetuses whose mothers had undergone sialoadenectomy (excision of the submandibular glands) was significantly lower than that of controls. However, the maternal-plasma EGF concentration was not significantly affected by sialoadenectomy. The body weight of fetuses whose mothers were injected with EGF for 7 days during pregnancy was significantly higher than that of controls. Sialoadenectomy altered the blood amino acid concentrations in adult female animals, especially the levels of leucine and isoleucine. These results suggest that EGF influences fetal growth mainly by regulating maternal nutrition.

Multichannel measurements of magnetic compound action fields of the median nerve in man

Magnetic compound action fields (CAFs) evoked by electrical stimulation of the median nerve at the wrist were recorded with 7-channel 2nd-order SQUID gradiometers. CAFs measured over the elbow and upper arm were biphasic with field patterns and polarities corresponding to the depolarization and repolarization fronts of the action potential volley.

Describing head shape with surface harmonic expansions

Surface harmonic expansions are used to represent boundaries between regions of different conductivity in the human head. This facilitates calculation of the electric potential and magnetic field generated by neural current sources using discretized integral equations.

[Clinical efficacy of ifosfamide for liver metastasis of breast cancer]

Chemotherapy for liver metastasis of breast cancer has rarely been found effective. We devised a new regimen of chemotherapy for recurrent breast cancer mainly using ifosfamide. It was found clinically applicable and particularly effective for liver metastasis. The tumor decreased in size and the levels of various tumor-markers markedly decreased following drug administration. This treatment has made for longer survival for some patients. Side effects could be well controlled with steroid hormones and Na-bicarbonate.

Nonspecific suppressor T cells cause decreased mixed lymphocyte culture reactivity in bone marrow transplant patients

Decreased reactivity in mixed lymphocyte culture (MLC) was observed in patients within 1 yr after allogeneic and autologous bone marrow transplantation. Suppressor activity of peripheral blood mononuclear cells (PBMC) from transplant patients was studied by adding these cells as modulator cells to a bidirectional MLC with cells from normal individuals. PBMC from transplant patients markedly suppressed MLC reactivity in a dose-dependent manner. Suppressor activity was present in cells forming rosettes with sheep erythrocytes. Treatment of modulator cells with monoclonal antibodies against T cell differentiation antigens (OKT8, OKIa1) and complement completely abolished suppression of MLC. Suppressor activity was unaffected by 30 Gy irradiation. Suppressor activity declined gradually after transplantation and was inversely correlated with MLC reactivity of each patient at a significant level (p less than 0.01). These observations suggest that OKT8+ Ia+ radioresistant suppressor T cells play a role in the development of decreased MLC reactivity observed during the early post-transplant period.

Nonspecific suppressor T cells cause decreased mixed lymphocyte culture reactivity in bone marrow transplant patients

Decreased reactivity in mixed lymphocyte culture (MLC) was observed in patients within 1 yr after allogeneic and autologous bone marrow transplantation. Suppressor activity of peripheral blood mononuclear cells (PBMC) from transplant patients was studied by adding these cells as modulator cells to a bidirectional MLC with cells from normal individuals. PBMC from transplant patients markedly suppressed MLC reactivity in a dose-dependent manner. Suppressor activity was present in cells forming rosettes with sheep erythrocytes. Treatment of modulator cells with monoclonal antibodies against T cell differentiation antigens (OKT8, OKIa1) and complement completely abolished suppression of MLC. Suppressor activity was unaffected by 30 Gy irradiation. Suppressor activity declined gradually after transplantation and was inversely correlated with MLC reactivity of each patient at a significant level (p less than 0.01). These observations suggest that OKT8+ Ia+ radioresistant suppressor T cells play a role in the development of decreased MLC reactivity observed during the early post-transplant period.

Effect of activated lymphocytes on the regulation of hematopoiesis: enhancement and suppression of in vitro BFU-E growth by T cells stimulated by autologous non-T cells

Autologous mixed lymphocyte culture (AMLR) is an immunologic response with memory and specificity and plays a role in immune regulation. Effects of T cells activated by AMLR were studied in the regulation of in vitro erythropoiesis. AMLR-activated T cells were cocultured with autologous non-T, nonphagocytic peripheral blood mononuclear cells for assaying erythroid progenitor cells (BFU-E). T cells activated for 3 days in AMLR showed significant enhancement of in vitro colony growth by BFU-E. In contrast, activated T cells from day 7 AMLR caused significant suppression of BFU-E growth. Both enhancing and suppressing activities of AMLR-activated T cells were mediated by an la-positive and radiosensitive population within the OKT4+ subset. These observations suggest that AMLR-activated T cells may play a role in the immune-mediated regulation of in vitro erythropoiesis. It is also suggested that heterogeneous T-cell subsets may exert regulatory functions in the regulation of in vitro hematopoiesis.