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Sheng-Yang Lee

Publications and source records attributed to Sheng-Yang Lee.

15 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

Radiolocalized sentinel lymph node biopsy in squamous cell carcinoma of the oral cavity and analysis of various parameters.

BACKGROUND: Sentinel lymph node (SLN) biopsy seems to be a method that solves the problem of neck management with oral squamous cell carcinoma. Using blue dye methods for detection of neck SLNs from the surface of the operative field seems difficult; therefore, we used radiolocalization alone to detect and extract sentinel nodes. Aside from the various histological and clinical parameters examined in this procedure, we also determined whether they had any clinical significance in relation to the detection of SLNs during the operation. METHODS: Enrolled subjects had preoperative clinical N0 stage squamous cell carcinoma of the oral cavity and had received an unfiltered (99m)Tc sulfur colloid peritumoral injection. Localization of the SLNs was performed by using lymphoscintigraphy and a handheld gamma probe. RESULTS: In total, 28 oral squamous cell carcinoma patients were included in this prospective study. Sixty-four SLNs in 27 patients were identified by this method. The identification rate was 96.4%. No false-negative predictions of SLN were noted among any of the patients studied. The numbers of the SLNs found during the operation were larger in patients with positive findings than those with negative findings (P < .05 by the Mann-Whitney U-test). CONCLUSIONS: SLN radiolocalization provided an acceptable identification rate. The cases of positive findings for metastasis seemed to statistically have more SLNs than did those with negative findings, but more evidence is needed to prove this point. Therefore, SLN biopsies for extracting all possible high-risk nodes may be conducive for oral squamous cell carcinoma surgery.

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

Factors influencing the wearing of protective gloves in orthodontic practice.

The purpose of this study was to explore how wearing, or not wearing, protective gloves affects the efficiency of orthodontists in performing certain orthodontic procedures. Thirty-six volunteers were randomly selected from members of the Taiwan Association of Orthodontists. A visual analogue scale (VAS) was used to determine the degree of convenience subjects felt in performing 11 specified orthodontic procedures, with and without gloves. In addition, the time required to bend round and rectangular archwires and to tie and untie ligature wires was recorded.The results showed that for 10 of the 11 orthodontic tasks there was perceived to be no difference when wearing, or not wearing, gloves. Only when bending a round archwire was there perceived to be a difference. When the four orthodontic procedures were undertaken on a typodont and timed, no significant difference was found between the use of gloves/no gloves.

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

Inhibition of hemagglutinating activity by monoclonal antibody against Porphyromonas gingivalis 40-kDa outer membrane protein.

Periodontitis is a chronic inflammatory disease of periodontal tissues that results in alveolar bone loss, and Porphyromonas gingivalis, which has a high hemagglutinating activity, has been implicated as an important pathogen in the development of periodontitis. This bacterium has a high hemagglutinating activity. We previously succeeded in gene cloning the 40-kDa outer membrane protein (OMP) from P. gingivalis 381. Although recombinant (r) 40-kDa OMP itself did not show hemagglutinating activity, its polymeric form, constructed with a cross-linking reagent, significantly expressed that activity. Furthermore, an affinity-purified antibody against r40-kDa OMP inhibited the hemagglutinating activity of P. gingivalis vesicles. In the present study, in order to clarify the pathological role of 40-kDa OMP and develop passive immunotherapy, we examined the inhibitory effect of monoclonal antibodies (MAbs) against r40-kDa OMP on the hemagglutinating activity of P. gingivalis vesicles. The MAbs reacted with r40-kDa OMP, the outer membrane fraction, vesicles, and P. gingivalis cell extracts, and significantly inhibited the hemagglutinating activities of the polymeric r40-kDa OMP as well as of P. gingivalis vesicles. These findings suggest that MAbs against 40-kDa OMP may be useful for the development of passive immunotherapy and for assessing treatment for periodontal diseases caused by P. gingivalis infection.

Animals↗
PubMed2004

Inhibition of Porphyromonas gingivalis hemagglutinating activity by synthetic peptides derived from phage display selection using MAb against the recombinant outer membrane protein.

Porphyromonas gingivalis has been implicated as an pathogen in the development of periodontitis, and hemagglutinins have been identified as an important adhesion onto the gingival tissue cells, and to attach and lyse erythrocytes to uptake Fe ion as an essential nutriant. The 40-kDa outer membrane protein (OMP) has been moleculary cloned from P. gingivalis 381. Since the antibody against recombinant (r) 40-kDa OMP inhibited the hemagglutinating activity, and the polymeric form of r40-kDa OMP itself expressed hemagglutinating activity, the 40-kDa OMP is thought to be one of the hemagglutinins. Moreover, we established MAbs against r40-kDa OMP which were capable of inhibiting hemagglutinating activity of P. gingivalis vesicles. In the present study, a phage-displayed epitope mapping system was used to identify the functional domain expressing hemagglutinating activity by biopanning using the neutralizing mAb, Pg-ompA1. The minimal epitope requirements of the MAb and the predicted amino acid sequences were identified in the region of (96)IALDQTLGIP(105) in 40-kDa OMP. Synthetic peptide, (87)WPRVGQLFIALDQTLGIPTFSVCRME(116), mapped the relevant molecule within a short stretch and is corresponding to residues of 40-kDa OMP. Chemically synthesized peptide was used to determine its inhibitory activity against hemagglutinating activity. The synthetic peptide significantly abolished hemagglutinating activity in a dose-dependent manner. These findings suggest that the synthetic peptide is an effective antagonist of erythrocyte binding, and this peptide may be a potent inhibitor of hemagglutination of P. gingivalis cells. The use of synthetic peptide neutralizing hemagglutinating activity of P. gingivalis represents a possible new therapeutic approach to P. gingivalis infected periodontitis.

Amino Acid Sequence↗
PubMed2004

Differentiation of the human mesenchymal stem cells derived from bone marrow and enhancement of cell attachment by fibronectin.

The ability of human mesenchymal stem cells (hMSC) to differentiate into osteoblasts was examined through the use of osteogenic induction medium (MSCOIM) cultures. hMSC first attached to the dish surface and exhibited fibroblast-like spindle shapes, and after proliferation, formed cuboidal shapes. Calcium assays and the use of von Kossa and alizarin red S staining showed that hMSC were capable of mineralization when cultured in MSCOIM. Gene expressions of Cbfa-1 and BMP-4, which are markers for osteogenic differentiation, were also increased during the hMSC differentiation into osteoblasts. When compared to albumin (Alb)-coated dishes, microscopic observation documented enhanced cell attachment and spreading when hMSC were cultured on fibronectin (FN)-coated dishes. Adherent cell numbers also exhibited a greater increase on the FN-coated dishes during earlier culture stages than that seen for the Alb-coated dishes. These findings suggest that hMSC have the capability to differentiate into osteoblasts and that FN can stimulate the attachment and spreading of the hMSC.

Bone Marrow Cells↗
PubMed2003

Factors influencing the resonance frequency of dental implants.

PURPOSE: Resonance frequency (RF) analysis has been used by several investigators to assess the boundary conditions of dental implants. However, a scientific investigation of the association between the structural condition of the alveolar bone and the dynamic behavior of dental implants has not yet been reported. The aim of this study was to assess the factors influencing the RF of dental implants using an in vitro modal analysis. MATERIALS AND METHODS: Resonant vibration within implants was induced by an impulse-force hammer. The induced vibration signal was subsequently detected using an acoustic microphone and analyzed by fast Fourier transform. The resultant data were further analyzed to test the statistical effects of the embedding-material boundary height, thickness, and density on the RF values of the sample implants. RESULTS: Significant changes (P <.05) in RF values were revealed for implants embedded within a high-density block when decreasing boundary height reached 6, 5, and 4 mm, at respective thickness increments of 10, 15, and 20 mm. For analogous low-density samples, significant changes (P <.05) in RF values were found when respective decreasing boundary height reached 6, 4, and 3 mm. CONCLUSIONS: Our findings indicate that boundary height, width, and density factors can influence the RF of dental implants and that a lower boundary density and greater boundary thickness can lead to more obvious RF changes.

Alveolar Bone Loss↗
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↗
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

Surface changes and acid dissolution of enamel after carbamide peroxide bleach treatment.

OBJECTIVES: To evaluate the effects of home bleaching (carbamide peroxide) on enamel surface morphology and the degree of acid dissolution. METHODS: Buccal surfaces of 15 caries-free human premolars were used in the study. The 15 teeth were cut in half in a buccal-lingual direction at midline; in total, 15 pairs of specimens were obtained. Group A consisted of five pairs that studied surface morphology change and Group B consisted of 10 pairs that studied the susceptibility of bleached enamel to acid dissolution. Tooth halves were prepared following a fluoride-free prophylaxis paste cleaning. One half of the tooth was untreated (control), and the other half was bleached (experimental) for eight hours daily for 10 days using 10% carbamide peroxide. Tooth samples were then stored in distilled water for seven days, after which scanning electron microscopy (SEM) was performed on Group A. Only halves from the same tooth were compared to rule out natural variations between teeth. Group B was etched with 37% phosphoric acid before being examined by SEM. The severity of the acid attack was graded from I to V, and the grades of each pair were compared. RESULTS: Results of the SEM observation showed that surface porosity slightly increased after bleaching, and more surface dissolution by phosphoric acid was seen with bleached, compared to unbleached, enamel.

Carbamide Peroxide↗
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↗