Biomedical subjects

Che-Tong Lin

Publications and source records attributed to Che-Tong Lin.

12 recordsLinked to original sources

PubMed2006

Vibrational analysis of mandible trauma: experimental and numerical approaches.

The aim of this study was to evaluate the effectiveness of vibrational assessment of the mandible fracture patterns. Measurement of natural frequencies and associated vibrational mode shapes was performed to determine the relationship between the dynamic behavior of the human mandible and incidence of mandibular fractures using both in vitro modal testing and finite element analysis. Our results show that the natural frequencies of the human mandible in dry and wet conditions are 567 Hz and 501 Hz, respectively. The first vibrational mode of human mandible is a bending vibration with nodes located at the mandibular body where bone fracture is less likely to occur. By contrast, high vibration amplitudes were identified in the symphysis/parasymphysis and subcondyle regions where bone fractures tend occur. These findings indicate that the vibrational characteristics of the mandible are potential parameters for assessment of the mechanisms of injury.

Finite Element Analysis↗

PubMed2006

Tissue engineered cartilage using human articular chondrocytes immortalized by HPV-16 E6 and E7 genes.

Chondrocytes are useful as a cell culture system for studying arthritic degeneration in tissue engineered cartilage. However, primary chondrocytes have short in vitro lifespan and rapid shift of collagen phenotype. In this study, we used a high dosage of retroviral vector LXSN16E6E7 to transduce human primary chondrocytes and obtained an actively proliferating cell line, designated hPi, which expresses HPV-16 E6/E7 mRNA in early passages. Parental primary chondrocytes cease to grow after five passages, whereas hPi could be propagated beyond 100 passages without requiring additional cell elements in defined medium. After 48 passages, hPi can also give many profiles similar to those of parental primary chondrocyte, including type II collagen in mRNA and protein level, aggrecan in mRNA level, lacunae in type I collagen matrices, and morphology with GAG-specific Alcian blue staining. hPi has shown neoplastic transformation, as examined by NOD-SCID mice tumorigenicity assays for 3 months. Our results indicated that human primary chondrocytes could be immortalized by transduction with HPV-16 E6/E7, preserving stable cartilage-specific differentiation markers. The established chondrocyte cell line could provide a novel model to engineer cartilage in vitro and in vivo for cartilage repair research and clinical application.

Animals↗

PubMed2006

Tissue-engineered intervertebral disc and chondrogenesis using human nucleus pulposus regulated through TGF-beta1 in platelet-rich plasma.

Human intervertebral disc (IVD) degeneration often initiated from the human nucleus pulposus (hNP) with aging leading to IVD destruction and extracellular matrix (ECM) depletion. Previously, we have successfully employed transforming growth factor-beta1 (TGF-beta1) to promote chondrogenesis of mesenchymal progenitor cells (MPCs) and immortalized human mesenchymal stem cells. In this study, we examine the role of TGF-beta1 in platelet-rich plasma (PRP) on disc regeneration, including proliferation, redifferentiation, and the reconstitution of tissue-engineered NP. hNP cells were isolated from volunteers with different ages and cultured in the presence of PRP. We found that the most effective concentration for hNP proliferation was 1 ng/ml TGF-beta1 in PRP, which was further applied in the following experiments. hNP cell proliferation in all age groups were increased time-dependently by PRP and cell morphologies showed aggregation. The mRNA of Sox9, type II collagen, and aggrecan were all significantly upregulated by PRP through RT-PCR. Glycosaminoglycan (GAG) accumulation reached the highest value at day 7 and continued to day 9 culture. PRP promoted NP regeneration via the Smad pathway was also determined and highly activated p-Smad2/3 at 30 min and continuously sustained to 120 min. Immunostaining of type II collagen indicates that PRP participates in chondrogenesis of tissue-engineered NP with collagen scaffolds. We concluded that growth factors in PRP can effectively react as a growth factor cocktail to induce hNP proliferation and differentiation, and also promote tissue-engineered NP formation. These findings are the first to demonstrate that PRP might be a therapeutic candidate for prevention of disc degeneration.

Adult↗

PubMed2006

Static magnetic fields up-regulate osteoblast maturity by affecting local differentiation factors.

Cell culture studies have shown that static magnetic fields induce osteoblastic differentiation at an early stage. However, the mechanisms of differentiated effects have not been well described. We postulated that static magnetic fields stimulate osteoblastic differentiation by regulating early local factors released by the cells. To examine our hypothesis, MG63 osteoblast-like cells were exposed continuously to 0.4-T static magnetic fields for 12, 24, 48, and 72 hours. The morphologic changes and matrix vesicles release were observed by scanning and transmission electron microscopy. The effects of static magnetic fields on levels of transforming growth factor-beta1, Type I collagen, osteopontin, and alkaline phosphatase were compared between the exposed and unexposed cells. The data suggest MG63 cells treated with static magnetic fields have more differentiated morphologic features. The local regulatory factors produced by static magnetic field-treated cells were greater than those of the control cultures. These findings provide evidence that static magnetic fields affect osteoblastic maturation by up-regulating early local factors.

Analysis of Variance↗

PubMed2005

Damping effects on the response of maxillary incisor subjected to a traumatic impact force: a nonlinear finite element analysis.

OBJECTIVES: The aim of this study was to evaluate the effects of damping on stress concentration in an impacted incisor. METHODS: Damping ratios of maxillary incisors were tested using an in vivo modal testing method. A finite element model of the upper central incisor was established for dental trauma analysis. To assess the effect of damping properties on induced stresses in the traumatized incisors, equivalent stresses in the finite element model with various damping ratios were calculated for comparison. The mechanisms of cushioning properties of the upper incisors on traumatic injuries were assessed by profiling the stress distributions in the incisor model sequentially with time. RESULTS: The measured damping ratio of maxillary incisors was 0.146+/-0.037. When the incisor was subjected to an impact force, high stresses were concentrated at the labial and lingual incisor edges, cervical ridge, and the area around root apex. When the damping ratios of the incisor model were set at 10- and 50-fold of the measured values, the peak stresses induced near the impact site of the incisor model were reduced from 24.0 to 23.2 and 15.9 MPa, respectively. On the other hand, the peak stress lagged and the stress existence period increased when the damping properties were taken into consideration. CONCLUSIONS: Damping properties of teeth provide protection to the tooth during traumatic injury by decreasing the peak stress magnitude due to release of strain energy over a longer period.

Adult↗

PubMed2005

Dynamic finite element analysis of the human maxillary incisor under impact loading in various directions.

The aim of this study was to investigate fracture patterns occurring when a human upper central incisor is subjected to impact loadings at various angles. A two-dimensional finite element (FE) model of the maxillary incisor and surrounding tissues was established. The structural damping factor for the tooth was then calculated and assigned to the model. Dynamic FE analysis was performed to stimulate the associated impacts. Time-dependent traumatic forces at 0 degrees, 45 degrees, and 90 degrees labially to the long axis of the tooth were applied to the model. Von Mises's equivalent stress contours within the FE models were calculated. Our results indicated that tooth damping lagged behind peak stress by 0.05 ms. In addition, we found that impact direction played an important role in terms of outcome for the fractured incisor. These results can, in part, explain the mechanisms underlying the alternative outcomes when upper incisors are subjected to impact.

Bite Force↗

PubMed2004

Comparison of tongue functions between mature and tongue-thrust swallowing--an ultrasound investigation.

Many studies have proved that tongue thrusting plays a significant role in the etiology of some orofacial deformities. To learn more about the relationship between tongue function and the form of orofacial structures, it is important to recognize patients with abnormal swallowing patterns. A cushion scanning technique in combination with M-mode ultrasound was applied to measure and compare tongue movements between mature swallowing and tongue-thrust swallowing. Forty subjects with a mature swallowing pattern (23 female, 17 male, aged 21.8 +/- 6.1 years) and 15 subjects with a tongue-thrust swallowing pattern (8 female, 7 male, aged 13.6 +/- 6.6 years) were included in this study. Duration, range, speed, and reproducibility for each of the swallowing subphases were calculated and compared. Tongue-thrust swallowers had a longer late transport phase than mature swallowers (P <.0009), and the tongue speed was faster in the early final phase (P <.05) compared with mature swallowers. Distinctly different movements can be positively differentiated with the method used.

Adolescent↗

PubMed2003

Measurement of tongue movement during vowels production with computer-assisted B-mode and M-mode ultrasonography.

OBJECTIVES: We sought to apply B- + M-mode ultrasonography in combination with the cushion-scanning technique (CST) in quantitative analysis of tongue movement during vowel articulation. STUDY DESIGN AND SETTING: Twenty normal persons (10 women and 10 men) were enrolled in this study. Each individual was asked to enunciate 5 vowels:/e/, /i/, /aI/, /o/, and /ju/. A noninvasive diagnostic technique, computer-assisted B-mode plus M-mode ultrasonography, was used in combination with the CST to assess their tongue movement. The sonographic signals were recorded on a video recorder and then transferred to a personal computer via a frame grabber for digital assessment. RESULTS: M-mode images show an amplitude-time diagram, whereas B-mode images reveal midsagittal tongue configuration. The ranges of tongue movement in midsagittal plane in male speakers during production of the vowels /e/, /i/, /aI/, /o/, and /ju/ were 8.29 +/- 1.76, 4.00 +/- 0.78, 13.82 +/- 2.86, 14.05 +/- 1.63, and 6.72 +/- 1.66 mm, respectively; for female speakers, the averages were 7.19 +/- 0.92, 3.36 +/- 1.31, 12.74 +/- 2.16, 12.86 +/- 2.18, and 7.11 +/- 2.09 mm, respectively. CONCLUSIONS: The computer-assisted B-mode plus M-mode ultrasonography in combination with the CST provides a standardized and quantifiable ultrasonographic examination for the clinical investigation of tongue movement during vowel articulation. In our study group, there was no difference in the thickness of tongue or the range of tongue movement in midsagittal plane during articulation of the selected vowels between males and females. Further exploration can be extended in the field of speech research by this valuable tool.

Adult↗

PubMed2003

Early detection of implant healing process using resonance frequency analysis.

In this study, in vitro and in vivo models were adopted for assessing the application of resonance frequency analysis (RFA) in the early detection of implant stability. In the in vitro tests, RF values of implants placed in bone block with predrilled cavities of 3.75 and 5.0 mm were measured and compared. Stone was used to fill the inter-space between implants and the bone blocks. Our results showed that poor initial stability conditions contributed to a lower initial RF (IRF) value (5.41+/-0.32 kHz) and a longer simulated healing period (41 min) than that of well-fitted conditions (9.63+/-0.34 kHz for IRF, 14 min for the simulated healing period, P<0.05). To validate such in vitro tests, animal models were also performed. Implants were placed in the left tibias of six rabbits using a general surgery procedure. The modal testing method was used to test the RF values of the implants. The RF values of the implants increased significantly (P<0.05) during the healing period and reached a plateau when the implant-bone interface was united. The variations of RF values of the testing implants showed a similar trend to the results of in vitro tests, i.e., implants with higher initial RF values had shorter simulated healing times. Based on these findings, we concluded that RFA is a reliable and accurate method for early assessment of the osseointegration process.

Acoustics↗

PubMed2003

Differential diagnosis between infantile and mature swallowing with ultrasonography.

In order to investigate the difference in tongue movement between visceral (infantile) and somatic (mature) swallowing patterns, 12 visceral (seven females, five males) and 14 somatic (eight females, six males) swallowers were examined with the B+M-mode ultrasound technique. Movements of the tongue tip and submental musculature during swallowing were recorded on video cassette and evaluated with a personal computer. The results demonstrated that the tongue dorsal surface, which was thought to be ideal for observing tongue function, was not suitable for differentiating between visceral and somatic swallowing patterns. Conversely, the movements of the genioglossus muscle were found to be identical within groups but significantly different (P < 0.01) from each other between the two swallowing patterns. Therefore, the genioglossus muscle can serve as a reliable means for differentiating between visceral and somatic swallowers.

Adolescent↗

PubMed2002

Resonance frequency assessment of dental implant stability with various bone qualities: a numerical approach.

Resonance frequency analysis (RFA) has been used by several investigators to assess the boundary conditions of dental implants. The goal of the current study was to determine the vibrating behavior of a dental implant under various surrounding bone conditions. A 3D finite element (FE) model of a cylinder-type titanium implant was developed. In this model, the implant was embedded into a cubic section of bone. The model was first validated using a series of modal testing experiments. The effects of bony conditions on the resonance frequencies of the implant were computed with different bone types and bone densities. Our results show that the resonance frequency of the implant with type III surrounding bone decreased linearly (r = -0.996, P < 0.01) from 17.9 kHz (without loss in bone density) to 0.6 kHz (90% loss in bone density) when the bone densities were decreased. On the other hand, without bone loss, the highest resonance frequency value (36.1 kHz) was found when the implant was placed into type I surrounding bone. In contrast, the resonance frequency of the implant with type IV bone quality was found to be 9.9 kHz, which is almost four-fold less than that found in the type I model. These results suggest that RFA could serve as a non-invasive diagnostic tool for detecting the stability of dental implants during the healing stages and in subsequent routine follow-up care after treatment.

Animals↗

PubMedDate not supplied

Evaluation of loading conditions on fatigue-failed implants by fracture surface analysis.

PURPOSE: The goal of this study was to determine the relationship between fracture surface morphology and applied stress level for dental abutment screws loaded in cyclic fatigue. If a correlation between fracture surface and load level can be determined, then the fracture surface analysis could be used as a tool to assess the mechanism by which a screw failed and the magnitude of the load at which it failed. MATERIALS AND METHODS: Test implants were loaded with static and cyclic forces. In the cyclic test, the load versus the number of cycles was plotted as a curve for biomechanical analysis. The fracture surfaces of the failed screws were observed and recorded using scanning electron microscopy (SEM). RESULTS: Two fracture phases, a smooth region and a rough region, were observed on the fracture surface. After identifying the boundary between the 2 regions, the smooth region ratio (SRR), the ratio of the smooth phase area to the area of the whole fracture surface, was measured using digitized SEM images. The mean SRRs were 0.60 +/- 0.03, 0.66 +/- 0.03, and 0.75 +/- 0.03 when the tested implants were subjected to dynamic loading of 60%, 55%, and 50% ultimate failure loading (UFL), respectively. Linear relationships were found between the SRR values and loading magnitude and between SSR and number of cycles. DISCUSSION: The smooth area on the fracture surface can be used to assess the load conditions and internal stress of fatigue-fractured implants. CONCLUSIONS: These results demonstrate that fracture surface analysis of fractured implants has the potential to become a useful indicator for assessing implant fracture mechanisms.

Dental Implants↗