Isolation and characterization of Leptolyngbya sp. KIOST-1, a basophilic and euryhaline filamentous cyanobacterium from an open paddle-wheel raceway Arthrospira culture pond in Korea.

AIMS: Cyanobacteria have been used as sustainable bioresource producers for foods, feeds and other valuable natural products. However, selection of a new species (other than Arthrospira), with advantageous properties for alimentary purposes, continues to be a challenge due to potential toxicity and low biomass productivity. In this study, we report a valuable filamentous cyanobacterium isolated from Korea. METHODS AND RESULTS: Morphological and phylogenetic analyses demonstrated that the isolate belongs to the genus Leptolyngbya, and consequently designated Leptolyngbya sp. KIOST-1. Interestingly, Leptolyngbya sp. KIOST-1 possessed numerous advantageous characteristics for biomass production, similar to Arthrospira. The isolate readily propagated in SOT medium with efficient biomass productivity, and its optimum growth was observed at 30°C under alkaline and saline conditions. Moreover, more than half of the cellular components in Leptolyngbya sp. KIOST-1 were composed of protein, with approx. 40% of essential amino acids. Most importantly, no significant cytotoxicity was detected in the isolate. CONCLUSIONS: Leptolyngbya sp. KIOST-1 has a number of advantageous characteristics for alimentary purposes due to its efficient productivity, high protein content and lack of potential cytotoxicity. SIGNIFICANCE AND IMPACT OF THE STUDY: Leptolyngbya sp. KIOST-1 may be considered a potential candidate for industrial biomass production, similar to Arthrospira.

Bone Regeneration of Blood-derived Stem Cells within Dental Implants.

Peripheral blood (PB) is known as a source of mesenchymal stem cells (MSCs), as is bone marrow (BM), and is acquired easily. However, it is difficult to have enough MSCs, and their osteogenic capacity with dental implantations is scarce. Therefore, we characterized peripheral blood mesenchymal stem cells (PBMSCs) cultured on a bone marrow-derived mesenchymal stem cell (BMMSC) natural extracellular matrix (ECM) and demonstrated the osteogenic capability in an experimental chamber implant surgery model in rabbits. We isolated PBMSCs from rabbits by culturing on a natural ECM-coated plate during primary culture. We characterized the PBMSCs using a fluorescence-activated cell scanner, cell proliferation assay, and multiple differentiation assay and compared them with BMMSCs. We also analyzed the osteogenic potential of PBMSCs mixed with hydroxyapatite/tricalcium phosphate (HA/TCP) by transplanting them into immunocompromised mice. Then, the mixture was applied to the canals. After 3 and 6 wk, we analyzed new bone (NB) formation inside the chambers using histological and histomorphometric analyses. The PBMSCs had a similar rate of BrdU-positive cells to BMMSCs, positively expressing CD90 but negative for CD14. The PBMSCs also showed osteogenic, adipogenic, and chondrogenic ability in vitro and osteogenic ability in vivo. Histological and histomorphometric results illustrated that the PBMSC and BMMSC groups showed higher NB than the HA/TCP and defect groups in the upper and lower chambers at 6 wk and in the upper canal at 3 wk; however, there was no difference in NB among all groups in the lower canal at 3 wk. The PBMSCs have characteristics and bone regeneration ability similar to BMMSCs both in vitro and in vivo. ECM was effective for obtaining PBMSCs. Therefore, PBMSCs are a promising source for bone regeneration for clinical use.

Bone regeneration at dental implant sites with suspended stem cells.

During the maintenance of bone marrow-derived mesenchymal stem cells (BMMSCs), suspended cells are discarded normally. We noted the osteogenic potential of these cells to be like that of anchorage-dependent BMMSCs. Therefore, we characterized suspended BMMSCs from rabbit bone marrow by bioengineering and applied the suspended BMMSCs to double-canaled dental implants inserted into rabbits. After primary isolation of BMMSCs, we collected the suspended cells during primary culture on the third day. The cells were transferred and maintained on an extracellular-matrix-coated culture plate. The cells were characterized and compared with BMMSCs by colony-forming-unit fibroblast (CFU-f) and cell proliferation assay, fluorescence-activated cell sorter (FACS), in vitro multipotency, and reverse transcription polymerase chain reaction (RT-PCR). We also analyzed the osteogenic potential of cells mixed with hydroxyapatite/tricalcium phosphate (HA/TCP) and transplanted into immunocompromised mice. We compared the viability and proliferation of the suspended BMMSCs and BMMSCs on the titanium implant surface and observed cell morphology. Then, the cells mixed with HA/TCP were applied to the double-canaled implants during installation into rabbit tibia. Four weeks later, we analyzed bone formation inside the canal by histomorphometry. The suspended cells showed higher CFU-f on the extracellular matrix (ECM)-coated culture plate and similar results of proliferation capacity compared with BMMSCs. The cells also showed osteogenic, adipogenic, and chondrogenic ability. The suspended cells showed levels of attachment survival and proliferation on the surfaces of titanium implant discs to be higher than or similar to those of BMMSCs. The suspended cells as well as BMMSCs showed stronger bone formation ability in both upper and lower canals of the implants compared with controls on double-canaled implants inserted into rabbit tibia. In this study, we showed that suspended cells after primary BMMSC isolation have bone regeneration capacity like that of BMMSCs, not only in vitro but also in vivo. ECM was valuable for propagation of MSCs for cell-based bone regeneration. Therefore, the suspended cells could also be useful tools for bone regeneration after implant surgery.

Impact of cellular microenvironment and mechanical perturbation on calcium signalling in meniscus fibrochondrocytes.

Mechanical signals regulate a multitude of cell functions and ultimately govern fibrous tissue growth, maintenance and repair. Such mechanotransduction processes often involve modulation of intracellular calcium concentration ([Ca2+]i). However, most studies interrogate these responses in cells in simplified culture systems, thereby removing potentially important inputs from the native extracellular microenvironment. The objective of this study was to test the hypothesis that the intracellular calcium response of meniscus fibrochondrocytes (MFCs) is dependent on both the microenvironmental context in which this perturbation is applied and on the tensile deformation. Using a custom micro-mechanical tester mounted on a confocal microscope, intracellular calcium activity in MFCs in response to incremental tissue strains (0, 3, 6 and 9 %) was monitored in situ (i.e., in the native tissues) on MFC-seeded aligned scaffolds and MFC-seeded silicone membranes. The [Ca2+]i regulation by MFCs within the native meniscus tissue microenvironment was considerably different from [Ca2+]i regulation by MFCs on either aligned nanofibrous scaffolds or flat silicone membranes. Additionally, increasing levels of tensile deformation resulted in a greater number of responding cells, both in situ and in vitro, while having no effects on temporal characteristics of [Ca2+]i signalling. Collectively, these findings have significant implications for mechanobiology of load-bearing fibrous tissues and their responses to injury and degeneration. In addition, from a tissue engineering perspective, the findings establish cellular benchmarks for maturing engineered constructs, where native tissue-like calcium mechano-regulation may be an important outcome parameter to achieve mechanical functionality comparable to native tissue.

A retrospective analysis of 29 isolated sphenoid fungus ball cases from a medical centre in Korea (1999-2012).

BACKGROUND: Isolated sphenoid sinus disease (ISSD) is rare. Fungus ball (FB) is the third most common ISSD. We analysed the characteristics of isolated sphenoid FB based on demographic data, presenting symptoms, preoperative computed tomography (CT), magnetic resonance imaging (MRI), and treatment outcomes. METHODOLOGY: From 1999 to 2012, 29 patients were identified with isolated sphenoid FB. Demographic data; clinical characteristics; endoscopic, CT, and MRI findings and treatment outcomes were retrospectively analysed. RESULTS: The most common symptom was headaches, which were localized in various regions of the brain. Other symptoms were uncommon. The most common CT findings were sclerosis, calcification, enlarged sinus and total opacification. On T2-weighted MRI images, we most commonly observed signal void. Endoscopic transnasal paraseptal sphenoidotomy was performed in all patients, and for most, this was performed under local anaesthesia. No recurrence was observed in any patient. CONCLUSION: Isolated sphenoid FB is predominantly observed in older women, and it is characterised by headaches and sclerosis of the sinus wall observed on CT scans. In cases of isolated sphenoid FB, endoscopic transnasal paraseptal sphenoidotomy can be successfully performed under local anaesthesia, which may facilitate rapid recovery and a low morbidity rate.

Isolation and characterization of a lytic Myoviridae bacteriophage PAS-1 with broad infectivity in Aeromonas salmonicida.

To search for candidate control agents against Aeromonas salmonicida subsp. salmonicida infections in aquaculture, one bacteriophage (phage), designated as PAS-1, was isolated from the sediment samples of the rainbow trout (Oncorhynchus mykiss) culture farm in Korea. The PAS-1 was morphologically classified as Myoviridae and possessed approximately 48 kb of double-strand genomic DNA. The phage showed broad host ranges to other subspecies of A. salmonicida as well as A. salmonicida subsp. salmonicida including antibiotic-resistant strains. Its latent period and burst size were estimated to be approximately 40 min and 116.7 PFU/cell, respectively. Furthermore, genomic and structural proteomic analysis of PAS-1 revealed that the phage was closely related to other Myoviridae phages infecting enterobacteria or Aeromonas species. The bacteriolytic activity of phage PAS-1 was evaluated using three subspecies of A. salmonicida strain at different doses of multiplicity of infection, and the results proved to be efficient for the reduction of bacterial growth. Based on these results, PAS-1 could be considered as a novel Aeromonas phage and might have potentiality to reduce the impacts of A. salmonicida infections in aquaculture.

The relationship between implant stability quotient values and implant insertion variables: a clinical study.

The aim of this study was to determine whether resonance frequency analysis can be integrated into the routine clinical evaluation of the initial healing of dental implants. In addition, this study was designed to verify whether there was a correlation between implant stability quotient (ISQ) values, maximum insertion torque values, angular momentum and energy, and to evaluate the importance of different clinical factors in the determination of ISQ values and maximum insertion torque values at implant insertion. Two different implant designs of 81 dental implants in 41 patients were evaluated using ISQ values. Maximum insertion torque values were obtained during the placement procedure. Two new methods were used to calculate the angular momentum developed due to implant installation as well as the energy absorbed by the bone. A linear correlation between ISQ values and maximum insertion torque values at the initial implant surgery was found (P < 0·01). There was a correlation between ISQ values and angular momentum (P < 0·05), although ISQ values and energy did not show a significant linear correlation at the initial surgery (P > 0·05). There was a correlation between maximum insertion torque values, each part's angular momentum, and their energies during installation (P < 0·01). The sequence of the variables that influenced ISQ values was implant location, design, diameter, and gender of the patient. The results of this experiment suggest that both ISQ values and new methods to calculate angular momentum and energy can help to predict implant stability.

Effect of biomimetic deposition on anodized titanium surfaces.

Surface energy and hydrophilicity of implant surfaces have been known to play an important role in subsequent cellular responses on the implant surface. The aim of the present study was to evaluate the effects of biomimetic deposition of anodized surfaces on surface wettability, surface energy, and osteoblast responses. Ti discs with 2 different surface topographies (machined and anodized) were immersed in Hanks' balanced salt solution (HBSS) and modified simulated body fluid (SBF) solution for 2 weeks at physiologic conditions of 37 °C, initial pH of 7.4, and p(CO(2)) of 0.05 atm. Scanning electron microscopic (SEM) observation and energy-dispersive spectroscopic (EDS) microanalysis showed the deposition of calcium phosphate (CaP) onto anodized Ti surfaces immersed in modified SBF. Surface energy, surface wettability, and osteoblast responses, including cell attachment capacity, cell proliferation rate, and cell differentiation level, significantly increased on anodized Ti surfaces immersed in modified SBF. The effects of biomimetic deposition with modified SBF on physiochemical surface characteristics and cell biological responses were greater on anodized surfaces than on machined surfaces. These results indicate that biomimetic deposition with effective SBF may enhance the interaction between anodized Ti surfaces and their biological environment, consequently improving bone healing of dental Ti implants.

Marginal bone loss around three different implant systems: radiographic evaluation after 1 year.

This study was designed to radiographically evaluate the effect of surface macro-and microstructures within the coronal portion of the external hex implant at the marginal bone change after loading. The fifty-four patients included in the study were randomly assigned to treatment groups with rough-surface implants (TiUnite, n = 45), a hybrid of smooth and rough surface implants (Restore, n = 45) or rough-surface with microthreads implants (Hexplant, n = 45). Clinical and radiographic examinations were conducted at the time of implant loading (baseline) and at 1-year post-loading. A three-level mixed-effect ancova was used to test the significance of the mean marginal bone change of the three implant groups from baseline to 1-year follow-up. At 1-year, significant differences were noted in marginal bone loss recorded for the three groups (P < 0.0001). The rough surface with microthread implants had a mean crestal bone loss of 0.42 +/- 0.27 mm; the rough surface implants, 0.81 +/- 0.27 mm; and the hybrid surface implants, 0.89 +/- 0.41 mm. Within the limitations of this study, a rough surface with microthreads at the coronal part of implant maintained the marginal bone level against functional loading better than implants without these two features.

In vivo comparison of force development with various materials of implant-supported prostheses.

The purpose of this study was to measure axial loading, generating bending moments on fibre reinforced composite (FRC) implant prostheses using strain-gauged customized abutment in vivo. Bending moments of conventional implant prosthetic material were also measured and the data were compared with those for FRC. Three unit fixed dental prostheses were made for two dental implant fixtures, which had been functioning properly for more than one year using Tescera ATL, porcelain fused to metal and gold as occlusal material. Three patients participated in this study; two patients had two implants on one side of the mandible and one had two implants on both sides of the mandible. Five sets of fixed dental prostheses were fabricated for each material and these were cemented with Temp-bond on strain-gauged customized abutments, which were screwed into the underlying implant fixtures. Axial loadings and bending moments were measured when a patient bit the experimental fixed dental prosthesis. ANOVA and the Tukey HSD test (alpha = 0.05) were used for statistical analysis. There were no significant differences in normalized bending moments among the three different implant prosthetic materials. Within the limitations of this study, Tescera ATL generated bending moments similar to conventional implant prosthetic materials such as gold and porcelain.

Preparation and characterization of bioactive calcium silicate and poly(epsilon-caprolactone) nanocomposite for bone tissue regeneration.

A novel biocomposite of nanosized calcium silicate (n-CS) and poly(epsilon-caprolactone) (PCL) was successfully fabricated directly using n-CS slurry, not dried n-CS powder, in a solvent-casting method. The in vitro bioactivity of the composite was evaluated by investigating the apatite-forming ability in simulated body fluid. A proliferation assay with mouse L929 fibroblasts was used to test the in vitro biocompatibility. The composition, hydrophilicity, and mechanical properties were also evaluated. Results suggest that the incorporation of n-CS could significantly improve the hydrophilicity, compressive strength, and elastic modulus of n-CS/PCL composites, with the enhancements mainly dependent on n-CS content. The n-CS/PCL composites exhibit excellent in vitro bioactivity, with surface apatite formation for 40% (w/w) n-CS (C40) exceeding that of 20% (w/w) n-CS (C20) at 7 and 14 days. The Ca/P ratios of apatite formed on C20 and C40 surfaces were 1.58 and 1.61, respectively, indicating nonstoichiometric apatite with defective structure. Composites demonstrated significantly better cell attachment and proliferation than that of PCL alone, with C40 demonstrating the best bioactivity. The apatite layers that formed on the composite surfaces facilitated cell attachment (4 h) and proliferation during the early stages (1 and 4 days). Collectively, these results suggest that the incorporation of n-CS produces biocomposites with enhanced bioactivity and biocompatibility.

Effects of implant geometry and surface treatment on osseointegration after functional loading: a dog study.

The purpose of this study was to evaluate the geometry and surface characteristics of osseointegration after functional loading by radiographic, periodontal and histomorphometric analyses. We analysed three groups of implants with different geometry and surface characteristics using experimental dogs. The control group received Brånemark implants (group 1). Group 2 and group 3 implants each had a 0.5-mm pitch height but differed in surface characteristics. Group 2 implants were machine surfaced and group 3 implants were thermally oxidized at 800 degrees C for 2 h in a pure oxygen atmosphere. For these experiments, which used a total of four healthy beagle dogs, the implants were randomly installed into the extracted first, second and third premolar positions. The animals received radiographic and clinical periodontal examinations at 6 and 12 months post-loading, and were then killed for histomorphometric analysis. The radiographic analysis showed that mean crestal bone resorption in the control group was greater than that observed in the experimental groups (P < 0.05). The percentage of bone-to-implant contact for group 3 (83.7%) was significantly higher than in groups 1 (74.4%) and 2 (75.0%) (P < 0.05). Overall, implant geometry and surface treatment affected the rate of crestal bone resorption and bone healing surrounding the dental implants.

Comparison of physical, chemical and cellular responses to nano- and micro-sized calcium silicate/poly(epsilon-caprolactone) bioactive composites.

In this study, we fabricated nano-sized calcium silicate/poly(epsilon-caprolactone) composite (n-CPC) and micro-sized calcium silicate/poly(epsilon-caprolactone) composite (m-CPC). The composition, mechanical properties, hydrophilicity and degradability of both n-CPC and m-CPC were determined, and in vitro bioactivity was evaluated by investigating apatite forming on their surfaces in simulated body fluid (SBF). In addition, cell responses to the two kinds of composites were comparably investigated. The results indicated that n-CPC has superior hydrophilicity, compressive strength and elastic modulus properties compared with m-CPC. Both n-CPC and m-CPC exhibited good in vitro bioactivity, with different morphologies of apatite formation on their surfaces. The apatite layer on n-CPC was more homogeneous and compact than on m-CPC, due to the elevated levels of calcium and silicon concentrations in SBF from n-CPC throughout the 14-day soaking period. Significantly higher levels of attachment and proliferation of MG63 cells were observed on n-CPC than on m-CPC, and significantly higher levels of alkaline phosphatase activity were observed in human mesenchymal stem cells (hMSCs) on n-CPC than on m-CPC after 7 days. Scanning electron microscopy observations revealed that hMSCs were in intimate contact with both n-CPC and m-CPC surfaces, and significantly cell adhesion, spread and growth were observed on n-CPC and m-CPC. These results indicated that both n-CPC and m-CPC have the ability to support cell attachment, growth, proliferation and differentiation, and also yield good bioactivity and biocompatibility.

Osseointegration of anodized titanium implants under different current voltages: a rabbit study.

The oxide layer that covers a titanium surface is extremely stable and appears to have excellent biocompatibility, which can result in successful osseointegration. The aim of this study was to analyse the characteristics of an oxide layer formed by anodic oxidation (anodization), and to evaluate the extent of bone healing around the anodized implant. The screw-type implants were made of commercially pure titanium (Grade 2). The Group 1 samples had a turned surface, and three other types of experimental specimens were anodized under constant voltages of 190 V (Group 2), 230 V (Group 3) and 270 V (Group 4). The surface characteristics of each sample type were inspected. Removal torque was measured after a 4-week healing period and the histomorphometric analysis was performed 6 weeks after implantation in rabbit tibiae. There was an increase in both the size and number of pores as the anodizing voltage increased. The Ra value of the Group 4 samples was higher than those in the Group 1 and 2 samples (P < 0.05). Group 3 showed a difference compared with Group 1 (P < 0.05). A thicker oxide layer, which contained crystalline (anatase) TiO(2) with the inclusion of some electrolytes (Ca, P), was formed at the higher anodizing voltage. Group 4 had higher removal torque values and percentages of bone-to-implant contact than the other groups (P < 0.05). The anodized titanium implants showed more intimate and stronger connections with peri-implant bone during early osseointegration than the turned titanium implants in this experimental model.

A biocompatibility study of a reinforced acrylic-based hybrid denture composite resin with polyhedraloligosilsesquioxane.

Acrylic-based denture materials have several common weak points, such as shrinkage after curing, lack of strength and toxicity. In order to solve these problems, we adapted a hybrid system using acrylic polymer and polyhedraloligosilsesquioxane (POSS). The aim of the study was to investigate the biocompatibility of a reinforced acrylic-based hybrid denture composite resin with POSS. Specimens of a novel polymeric denture base resin, in which POSS was used to partially replace the commonly used base monomer, were fabricated. In order to examine changes in biocompatibility with time, fresh specimens, along with specimens soaked in distilled water for 24 and 72 h were fabricated. Three other types of acrylic denture base resins were used to prepare the resin specimens. Biocompatibility (as measured by a metabolic assay, an agar overlay test, and a mutagenesis assay) of the composites was tested. The metabolic and mutagenesis assays were conducted with pure culture medium as a control. In this study, the reinforced acrylic-based hybrid denture composite resin with POSS showed improved biocompatibility and lower mutagenicity than the control. Statistical examinations showed the cell metabolic activity of the novel polymeric denture base resin in the 72-h immersion case as having almost the same inclination as the control. We hope that these results might aid in the development of a reinforced acrylic-based denture resin.

Biological responses of anodized titanium implants under different current voltages.

The oxide layer of a titanium surface is very stable, and seems to result in excellent biocompatibility and successful osseointegration. The purpose of this study was to investigate the effects of high anodic oxidation voltages on the surface characteristics of titanium implants and the biologic response of rabbit tibiae. Bone tissue responses were evaluated by removal torque tests and histomorphometric analysis. Screw-shaped implants with microthreads were made of commercially pure titanium (Grade II). We prepared anodized implants under 300 V (group I), 400 V (group II), 500 V (group III) and 550 V (group IV). The surface characteristics of specimens were inspected according to three categories: surface morphology, surface roughness and oxide layer thickness. The screw-shaped implants were installed in rabbit tibiae. The removal torque values were measured and histomorphometric analysis was done after 1- and 3-month healing periods. Data indicate that as anodic oxidation voltage increased above 300 V, oxide layer thickness increased rapidly and pore size also increased. The roughness values of the implants increased with voltage up to 500 V, but decreased at 550 V. In the removal torque test, group III showed higher values than groups I and II at a statistically significant level (P < 0.05) after a 1-month healing period. In histomorphometric analysis, groups III and IV, after a 3-month healing period, showed greater bone to implant contact ratios for the total implant surface than did group I (P < 0.05).

An abutment screw loosening study of a Diamond Like Carbon-coated CP titanium implant.

The aim of this study was to quantify the extent of abutment screw loosening and thus understand the role of frictional and wear factors in abutment screw loosening by using a cyclic loading device to compare Diamond Like Carbon (DLC)-coated and non-coated implants. The properties of DLC films, including hardness, wear resistance, chemical stability, and biocompatibility, are similar to those of real diamond materials. In this study, a 1-mum thick DLC film served to protect and lubricate a layer of commercially-pure titanium affixed to the top of a dental implant (external hexagon-shaped implant). A cyclic loading force was then applied to the top of the prosthetic portion of the implants in order to determine the difference in looseness of the titanium abutment screw between ten DLC-coated implants and ten non-coated implants. The abutment screw loosening tests were performed with 100 N of force at a frequency of 20 Hz. Data indicate that implants with a DLC coating are more resistant to an applied force (P = 0.002) than are those without the coating. We hope these results will be useful for preventing implant abutment screw loosening.

Stress distributions in maxillary bone surrounding overdenture implants with different overdenture attachments.

In this study, effects of different overdenture attachments on the stress distributions in the maxillary bone surrounding the overdenture implants are studied. Four different types of attachment are considered. They are rigid Dalbo Stud, movable Dalbo Stress Broken, movable Dalro, and movable O-ring attachments. Three-dimensional finite element analysis was conducted with commercial package to obtain the stress distributions in the maxillary bone. Varying the attachment types and angle of inclination of load, the stress distributions in the portions of compact bone and trabecular bone were monitored separately. The analysis was conducted by assuming two different boundary conditions at the interface between cap and overdenture abutment in order to evaluate influence of interface boundary condition on stress distribution in the maxillary bone. They were perfect bonding condition and contact with friction at the interfaces. However, it is preferable to assume perfect bond condition at the interface for rigid type attachment systems and contact with friction at the interface for movable type attachment systems. From the numerical results, it was found that the load transfer mechanism of the implant system is altered significantly by the types of the overdenture attachment and also special care must be taken to assign proper boundary conditions at the interface for the analysis. The movable type Dalro attachment generated the highest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for contact with friction. The rigid type Dalbo Stud attachment generated the smallest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for perfect bonding condition.

Effect of tooth brushing and thermal cycling on a surface change of ceromers finished with different methods.

This in vitro study evaluated the effect of tooth brushing and thermal cycling on the surface lustre and surface roughness of three ceromer systems treated with different surface finishing methods. The ceromers studied were: (1). Artglass, (2). Targis, (3). Sculpture and (4). the control group, Z 100. Half of the Targis and Sculpture groups were polished and the rest were coated with staining and glazing solution, respectively. All specimens were subjected to thermocycling 10000 times. Tooth brushing abrasion tests were performed in a customized tooth-brushing machine with 500 g weight applied on a back-and-forth cycle for 20000 repetitions. The lustre determined by measuring the light reflection area and the average roughness was compared between groups and between pre- and post-test values. All materials showed a lower lustre and rougher surface after thermocycling and tooth brushing (P < 0.05). All ceromer specimens, except glazed Sculpture, showed a higher lustre and similar roughness to the control group. The post-brushing results revealed that glazed Sculpture presented discretely fallen out glaze coatings and had maximum change. However, stained Targis showed minimum change (P < 0.05) and polished Targis presented more changes than that of the staining treatment. It is therefore concluded that the glaze coatings for Sculpture don't exhibit long-term durability, while stain coatings for Targis acted like a protective layer.

Evaluation of design parameters of osseointegrated dental implants using finite element analysis.

Finite element analyses were performed for various shapes of dental implant to study effects on stress distribution generated in the surrounding jaw bone and to determine an optimal thread shape for even stress distribution. It was found that the square thread shape filleted with a small radius was more effective on stress distribution than other dental implants used in the analyses. Additional analyses were performed on the implant with the thread shape obtained from previous analyses for varying other design parameters, such as the width of thread end and height of thread for various load directions, to determine the optimal dimensions of the implant. Stress distribution was more effective in the case when the width of thread end and the height of thread were 0.5p and 0.46p, respectively, where p is the screw pitch. Then, using the optimal implant thread dimensions determined previously, stress analyses were performed with various screw pitches and implant lengths, to investigate effects on stress distribution and to find the way to reduce the maximum effective stress generated in the jaw bone. Results show that the maximum effective stress decreased not only as screw pitch decreased gradually but also as implant length increased.