Micro-scale finite element modeling of ultrasound propagation in aluminum trabecular bone-mimicking phantoms: A comparison between numerical simulation and experimental results.

The present study investigated the accuracy of micro-scale finite element modeling for simulating broadband ultrasound propagation in water-saturated trabecular bone-mimicking phantoms. To this end, five commercially manufactured aluminum foam samples as trabecular bone-mimicking phantoms were utilized for ultrasonic immersion through-transmission experiments. Based on micro-computed tomography images of the same physical samples, three-dimensional high-resolution computational samples were generated to be implemented in the micro-scale finite element models. The finite element models employed the standard Galerkin finite element method (FEM) in time domain to simulate the ultrasonic experiments. The numerical simulations did not include energy dissipative mechanisms of ultrasonic attenuation; however, they expectedly simulated reflection, refraction, scattering, and wave mode conversion. The accuracy of the finite element simulations were evaluated by comparing the simulated ultrasonic attenuation and velocity with the experimental data. The maximum and the average relative errors between the experimental and simulated attenuation coefficients in the frequency range of 0.6-1.4 MHz were 17% and 6% respectively. Moreover, the simulations closely predicted the time-of-flight based velocities and the phase velocities of ultrasound with maximum relative errors of 20 m/s and 11 m/s respectively. The results of this study strongly suggest that micro-scale finite element modeling can effectively simulate broadband ultrasound propagation in water-saturated trabecular bone-mimicking structures.

Adjunctive techniques for enhancing mandibular growth in Class II malocclusion.

Class II malocclusions are generally characterized by mandible retrusion. For this reason, forward bite jumping appliances, also known as functional appliances were originally designed to enhance mandibular forward projection. However, there is still insufficient evidence to support the effectiveness, predictability and stability of functional appliances in modifying mandibular growth. This article was aimed at presenting evidences and hypotheses that mandibular growth may be enhanced through the use of adjunctive methods in conjunction with functional appliances. In formulating our hypothesis, we considered relevant data, mostly derived from animal studies, concerning alternative methods, such as low-intensity ultrasound and light-emitting diode, as well as their related cellular and molecular mechanisms. According to the evidences covered in this article, we suggest that both methods are potentially effective, and theoretically able to act in synergistic way to enhance functional appliances treatment on mandibular and condylar additional growth. The rationale for the use of these methods as adjunctive therapies for mandibular underdevelopment is attributed to their abilities on stimulating angiogenesis, cell differentiation, proliferation, and hypertrophy, as well as enhancing matrix production and endochondoral bone formation, especially on the condyle of growing animals. This article also proposed a study design which would be able to either prove or refute our hypothesis. If ratified, it would represent a significant scientific accomplishment which provides support for further investigations to be carried out on well-designed clinical trials.

The finite element method for micro-scale modeling of ultrasound propagation in cancellous bone.

Quantitative ultrasound for bone assessment is based on the correlations between ultrasonic parameters and the properties (mechanical and physical) of cancellous bone. To elucidate the correlations, understanding the physics of ultrasound in cancellous bone is demanded. Micro-scale modeling of ultrasound propagation in cancellous bone using the finite-difference time-domain (FDTD) method has been so far utilized as one of the approaches in this regard. However, the FDTD method accompanies two disadvantages: staircase sampling of cancellous bone by finite difference grids leads to generation of wave artifacts at the solid-fluid interface inside the bone; additionally, this method cannot explicitly satisfy the needed perfect-slip conditions at the interface. To overcome these disadvantages, the finite element method (FEM) is proposed in this study. Three-dimensional finite element models of six water-saturated cancellous bone samples with different bone volume were created. The values of speed of sound (SOS) and broadband ultrasound attenuation (BUA) were calculated through the finite element simulations of ultrasound propagation in each sample. Comparing the results with other experimental and simulation studies demonstrated the capabilities of the FEM for micro-scale modeling of ultrasound in water-saturated cancellous bone.

The validity, reliability, and time requirement of study model analysis using cone-beam computed tomography-generated virtual study models.

OBJECTIVES: To investigate the validity, reliability, and time spent to perform a full orthodontic study model analysis (SMA) on cone-beam computed tomography (CBCT)-generated dental models (Anatomodels) compared with conventional plaster models and a subset of extracted premolars. SETTING AND SAMPLE POPULATION: A retrospective sample of 30 consecutive patient records with fully erupted permanent dentition, good-quality plaster study models, and CBCT scans. Twenty-two extracted premolars were available from eleven of these patients. MATERIALS AND METHODS: Five evaluators participated in the inter-rater reliability study and one evaluator for the intrarater reliability and validity studies. Agreement was assessed by ICC and cross-tabulations, while mean differences were investigated using paired-sample t-tests and repeated-measures anova. RESULTS: For all three modalities studied, intrarater reliability was excellent, inter-rater reliability was moderate to excellent, validity was poor to moderate, and performing SMA on Anatomodels took twice as long as on plaster. CONCLUSIONS: Study model analysis using CBCT-generated study models was reliable but not always valid and required more time to perform when compared with plaster models.

Long-term results of bilateral mandibular distraction osteogenesis using an intraoral tooth-borne device in adult Class II patients.

The aim of this prospective clinical study was to evaluate the short-term and long-term skeletal and dental changes after mandibular osteodistraction with tooth-borne appliances in adult orthodontic patients. The sample consisted of 10 non-growing Caucasian patients with a Class II skeletal relationship due to mandibular deficiency, together with Class II dental malocclusion. All patients underwent mandibular distraction osteogenesis (MDO) using the ROD1 tooth-borne device. Lateral cephalograms were evaluated at four time intervals: pretreatment (T1), after mandibular distraction (T2), after orthodontic fixed appliance therapy (T3), and at long-term observation 8-year post-distraction (T4). Statistical analyses compared the skeletal and dental changes in intervals T1-T2, T2-T3, T3-T4, T1-T4, and T2-T4. MDO with the ROD1 tooth-borne device produced significant long-term (T1-T4) increases in the SNB angle (2.3°), total mandibular length (5.9mm), and corpus length (4.5mm). Potential adverse sequelae included significant increases in mandibular plane angle (4.3°), lower anterior dental height (2.8mm), and lower posterior dental height (2.5mm). Significant increases in lower incisor proclination occurred during distraction (7.5°). Distraction osteogenesis with tooth-borne appliances offers a minimally invasive surgical method with stable results for correcting mandibular deficiency in non-growing patients.

The effect of low intensity pulsed ultrasound in a 3D ex vivo orthodontic model.

OBJECTIVES: This study investigated the effects of low intensity pulsed ultrasound (LIPUS) on dentoalveolar structures during orthodontic force application using a novel organ culture system. METHODS: Mandibles were dissected from 28-day-old male Sprague Dawley rats, sliced into 1.5mm and cultured at 37°C and 5% CO(2), prior to application of a 50g force to each mandible slice. Slices were randomly divided into three groups of control, 5 and 10min LIPUS application and cultured for five days before histological and histomorphometrical analysis. RESULTS: Cementum and predentine thickness and subodontoblast and periodontal ligament cell counts were increased in the ultrasound groups, with increases statistically significant in the 10min treated groups. Odontoblasts remained viable during LIPUS exposure and osteoclast activity was increased by LIPUS. CONCLUSIONS: LIPUS may influence remodelling of the dentine-pulp complex and associated tissues during orthodontic force application ex vivo.

Design and implementation of therapeutic ultrasound generating circuit for dental tissue formation and tooth-root healing.

Biological tissue healing has recently attracted a great deal of research interest in various medical fields. Trauma to teeth, deep and root caries, and orthodontic treatment can all lead to various degrees of root resorption. In our previous study, we showed that low-intensity pulsed ultrasound (LIPUS) enhances the growth of lower incisor apices and accelerates their rate of eruption in rabbits by inducing dental tissue growth. We also performed clinical studies and demonstrated that LIPUS facilitates the healing of orthodontically induced teeth-root resorption in humans. However, the available LIPUS devices are too large to be used comfortably inside the mouth. In this paper, the design and implementation of a low-power LIPUS generator is presented. The generator is the core of the final intraoral device for preventing tooth root loss and enhancing tooth root tissue healing. The generator consists of a power-supply subsystem, an ultrasonic transducer, an impedance-matching circuit, and an integrated circuit composed of a digital controller circuitry and the associated driver circuit. Most of our efforts focus on the design of the impedance-matching circuit and the integrated system-on-chip circuit. The chip was designed and fabricated using 0.8- ¿m high-voltage technology from Dalsa Semiconductor, Inc. The power supply subsystem and its impedance-matching network are implemented using discrete components. The LIPUS generator was tested and verified to function as designed and is capable of producing ultrasound power up to 100 mW in the vicinity of the transducer's resonance frequency at 1.5 MHz. The power efficiency of the circuitry, excluding the power supply subsystem, is estimated at 70%. The final products will be tailored to the exact size of teeth or biological tissue, which is needed to be used for stimulating dental tissue (dentine and cementum) healing.

Effects of ultrasound modes on mandibular osteodistraction.

Previous studies have shown that therapeutic pulsed ultrasound (pulsed) has superior stimulatory effect on bone fracture healing compared with continuous ultrasound (continuous). Our predictive hypothesis was that pulsed ultrasound can produce better bone formation during mandibular osteodistraction than continuous ultrasound. Thirty-six New Zealand rabbits were divided into 3 groups of 12. Osteodistraction was performed at 3 mm/day for 5 days. Group 1 received pulsed, group 2 received continuous ultrasound, and group 3 was the control group (distraction only). Bone formation was assessed by quantitative bone density (QBD), mechanical testing, and histological examination. In the first 2 wks post-distraction, group 2 showed enhanced bone formation more than group 1 (p < 0.05); however, in the 3rd and 4th wks, group 1 showed more bone formation than group 2 (p < 0.05). Earlier stages of bone healing were enhanced more by continuous, whereas late stages were enhanced more by pulsed, ultrasound.

Vibratory coherence as an alternative to radiography in assessing bone healing after osteodistraction.

Distraction osteogenesis is used in orthopedics to lengthen bones by cutting or breaking the bone and gradually separating the two pieces as new bone fills the intervening space. There is a need for early assessment of the degree of bone healing that allows for normal functioning without unwanted side effects. This study compared different techniques used to evaluate the degree of bone healing during mandibular osteodistraction in 21 rabbits. For each rabbit, the mandible was cut in a surgical procedure and then 72 h later distraction began at a rate of 3 mm per day. Bone formation at the distraction site was assessed by in vivo photodensitometry on head radiographs, an in vivo (nondestructive) vibratory coherence test across the distraction site, a postmortem, ex vivo (destructive) three-point bending mechanical test, and by postmortem, ex vivo (destructive) histological examination. Statistical analyses included analysis of variance and correlation coefficient tests. The findings revealed that the results of bone photodensity and the mechanical three-point test are highly and positively correlated with the results of the vibration test. The use of the vibration test may provide a substitute for or augment the routine use of radiography for in vivo evaluation and monitoring of bone healing.

Surgical and orthodontic considerations for distraction osteogenesis with ROD appliances.

Tooth-borne/hybrid distraction devices offer a new approach for intraoral DO and better control of the distracted bony segments. These appliances also offer a unique characteristic by using the teeth as reference points for obtaining parallelism of the distraction devices to each other and to the vector of distraction in bilateral cases. More studies may be needed for long-term evaluation of the obtained results with intraoral distraction devices as well as biomechanical analysis of stress distribution throughout the mandible after distraction.

Erythroderma.

Erythroderma can be caused by a variety of underlying dermatoses, infections, and systemic diseases. Many of the findings on history, physical examination, and laboratory evaluation are nondiagnostic. Distinctive clinical and laboratory features pointing to a specific disease may be evident, however. Conclusive clinicopathologic correlation may require multiple and repeated skin biopsies. The prognosis of erythroderma has improved with the advent of innovative dermatologic therapies (e.g., cyclosporine and synthetic retinoids) and advances in the management of systemic manifestations. Death from sepsis, cardiac failure, adult respiratory distress syndrome, and capillary leak syndrome continue to be rarely reported. A high index of suspicion for these complications must be maintained to facilitate early medical intervention.

Study of craniofacial morphology and skeletal maturation in juvenile diabetics (Type I).

The aims of this study were to examine the craniofacial morphology of patients with juvenile diabetes, to investigate the effects of juvenile diabetes on general growth and skeletal maturation, and to analyze the pattern of association between craniofacial morphology and skeletal maturation in these patients. The sample consisted of 20 male patients with juvenile diabetes whose ages ranged from 14 to 16 years and who were affected with the condition at least 5 years before the study. Twenty normal subjects, with the same age range, were chosen as a control group. Height, weight, lateral cephalometric and hand-wrist radiographs were taken for all subjects, corrected for magnification distortion, and analyzed. The diabetic patients showed decreased skeletal maturation and decreased cephalometric linear and angular measurements when compared with the control group. These results should be considered when diabetic patients require orthodontic or orthopedic treatment.

Mandibular lengthening using preprogrammed intraoral tooth-borne distraction devices.

PURPOSE: This report describes the application of an intraoral device for treatment of malocclusions characterized by mandibular deficiency and the surgical technique for its placement. PATIENTS AND METHODS: In an office setting, 5 retrognathic patients underwent mandibular lengthening via distraction osteogenesis with an intraoral tooth-borne distraction device. Under local anesthesia and sedation, mandibular corticotomies, mobilization, and placement of the distractors were performed. Preoperative, intradistraction, and postoperative dental casts, photographs, and cephalometric radiographs were used to analyze the results. RESULTS: In 3 of the 5 cases, distraction occurred along the planned vector. The remaining 2 cases showed opening rotations of the mandibular anterior segment along with the advancement. CONCLUSIONS: This study documents that the mandible and the dental arch can be lengthened successfully using this technique.

High-output congestive failure due to arteriovenous fistula resulting from lumbar disc surgery--a case report.

A patient is described who developed high-output congestive failure following surgery to a lumbar disc. Diagnosis of arteriovenous fistula was suggested by the signs of high-output state and a continuous bruit heard over the low back scar. Confirmation was demonstrated by abdominal aortography. Corrective surgery resulted in resolution of congestive failure.