Papers by Keyword: Dental Material

Abstract: Chitosan can be extracted from the hermetia illucens chitin. It has excellent biocompatibility, non-toxic, bioresorbable, anti-inflammatory and wound healing properties. It can be formed into a gel, granules, sheet/film, porous structure, or scaffold in dental medications. Hermetia illucens cocoons were collected and extracted from the by-product of organic waste management in Bandung City. The samples were dried in the oven at 105°C for 48h and grounded in the powder grinder and sieved. Demineralization proces were done by immersed samples in 1 M HCl for 6h. The powder then deproteinized using 1 M NaOH solution for 8h at 80 ^oC, filtrated, and washed with distilled water. Then, the samples were immersed in 1% KMnO4 solution for 1h, and cleaned the residue with an oxalic acid solution. Samples obtained were dried in the oven at 60 ^oC for 48h before deacetylated with deionized water. Characterization were done by Fourier Transform Infrared spectroscopy (FTIR), and Scanning Electron Microscope (SEM). IR spectra showed disctinctive OH bond at 3253.62 cm^-1 and amide I band at 1616.98 cm^-1. Degree of deacylated were calculated using infrared spectra data and resulting 77.372% indicating good character of chitosan. The result SEM were inducated typical pattern of chitosan. Further study is to fabricate the medical-grade chitosan for dental material. The chitosan from the hermetia illucens is a promising natural biopolymer for dental applications and organic waste management solutions.

Abstract: Composite resin is one of the most important materials used in all industrial and medical fields nowadays, but it has many properties and advantages that distinguish it from metals. Many problems appeared previously due to the materials used and to overcome these problems, A composite resin with great physical and mechanical properties and compatibility has been developed. Composite resins are resin filled with high compressive strength, corrosion resistance, light weight, ease of application and high transparency. The aim of this study is to demonstrate the improvement of mechanical properties represented in tensile strength, fatigue life, impact resistance and hardness For polymeric materials such as epoxy after adding nanomaterials (graphene).

Abstract: Dry socket disease, a pocket wound caused by the tooth extraction that resulted in severe acute pain which requires a topical analgesic with rapidly pain reduction and suppress the pain until the wound healed. This study aimed to investigate factors affecting gelation temperature and gelation time of lidocaine hydrochloride (LH)-loaded polyelectrolyte complex (PEC) thermosensitivity gel for treating dry socket wound. The first factor was investigated the effects of the ratio of three different types of polymers as chitosan (CS), hyaluronic acid (HA) and poloxamer407 (P407) on the phase transition caused by temperature. The second factor was examined the effects of gel preparation methods. The results showed that increasing concentration of the cationic polymer as CS induced the separation of the solution to gel (sol-to-gel) system due to the charge of CS and the charge of PEC. The ratio of HA:P407 affected the gel forming which high concentration of P407 reduced the gelation temperature while low concentration of HA disturbed the sol-to-gel state causing coagulation. The viscosity, spreadability, and swelling were significantly increased due to the concomitant increased in each polymer, HA and P407. The particle of the formulation observed under microscope was found to be less than 1 µm. Phase inversion from sol-to-gel was found after a min at 23°C. Since gelation temperature of the purposed formula is supposed to form gel below 37°C within a short period of injection. The results of the study indicate the suitable sol-to-gel forming in the appropriate temperature and time which should be used for further investigation in the efficacy and safety.

Abstract: Silver alloy is one of semi-precious alloys for dental prosthesis, which has been applied remarkably in Japanese dental field. Ag-20Pd-17.7Cu-12Au alloy (G12), which was newly developed for commercial dental silver alloy, shows the unique hardening mechanism after a simple solution treatment (ST) at relatively high temperature. However, the relationship between ST at various temperature and the mechanical strength of G12 has not been investigated fully. Therefore, the relationship between ST and mechanical properties of G12 after ST at various temperatures was investigated systematically in this study. G12 subjected to ST at relatively high temperature of 1173 K is composed of three kinds of phases with Ag-rich α₂ phase, Cu-rich α₁ phase and β phase of Pd-Cu intermetallic compound. Although nominal melting point of G12 was around 1233 K, the high Cu concentration area like α₁ phase was partially dissolved and then the α₁, α₂ and partial β phases re-precipitated during cooling. On the other hand, the microstructure of G12 aged at 673 K after ST at 1023 K (STA) was mainly composed of two kinds of phases with α₂ and α₁ phases with a small amount of β phase, which was a typical microstructure of STA. The Vickers hardness of G12 subjected to ST at 1173 K was identical to that of the same alloy subjected to STA although the tensile strength, fatigue limit and ductility deteriorated to some degrees. The corrosion potential of G12 changed drastically with the temperature of ST. The potential may have been increased by the decrease in the volume fraction of the α₁ phase with relatively high Cu content.

Abstract: In this work three dental ceramics were characterized according to ISO 6872: yttria-stabilized zirconia (ZrO₂-Y₂O₃), lithium disilicate (Li₂Si₂O₅) and the spinel-zirconia composite (MgAl₂O₄-ZrO₂). The zirconia ceramic and the zirconia-spinel composite were sintered at 1600°C-2h, while the lithium disilicate was thermally treated at 820°C-20min. These materials were characterized by relative density, X-ray diffraction, scanning electron microscopy, hardness, fracture toughness, chemical solubility and cytotoxicity. The XRD results showed for the stabilized zirconia only the tetragonal phase of ZrO₂, and to the composite only the phase MgAl₂O₄, Li₂Si₂O₅ was the only phase to lithium disilicate. Relative density results showed that the zirconia and the lithium disilicate showed high densification (> 99.5%) and the composite had a relative density of 75% (10% composite doped with ZrO₂) and 90% (50% doped with ZrO₂). Hardness and toughness showed 450HV and 3.2MPa.m^1/2 to ZrO₂-MgAl₂O₄ composites, 525HV and 1.8MPam^1/2 to lithium disilicate and 1280HV and 8.0MPa.m^1/2 to zirconia. The materials evaluated showed chemical solubility <30μg/cm² and the results of cytotoxicity tests indicated cell viability of the samples near 100% for all the materials, showing good chemical stability and potential for dental applications.

Abstract: Bioceramics have rapidly emerged as one of major biomaterials in modern biomedical applications because of its outstanding biocompatibility. However, one drawback is its low tensile strength and fracture toughness due to brittleness and inherent microstructural defects, which to a certain extent prevents the ceramics from fully replacing metals used as load-bearing prostheses. This paper aims to model the crack initiation and propagation in ceramic fixed partial denture, namely dental bridge, by using two recently developed methods namely continuum-to-discrete element method (CDEM) in ELFEN and extended finite element methods (XFEM) in ABAQUS. Unlike most existing studies that typically required prescriptions of initial cracks, these two new approaches will model crack initiation and propagation automatically. They are applied to a typical prosthodontic example, thereby demonstrating their applicability and effectiveness in biomedical applications.

Abstract: Objective: to investigate glass infiltrating rates (depth/time) within dental CAD/CAM alumina at different temperatures. Methods: micron α-alumina powder was prepared with cold isostastic pressure at 250 MPa and sintered at 1450°C. The presintered alumina specimens were then infiltrated with special glass at 1150°C, 1200°C and 1250 °C. The infiltrating depths and time to form the infiltrate at the different temperatures were evaluated. Results: As the infiltrating temperature increased, the viscosity of the infiltrating glass decreased, and the infiltrating depth increased. A 1 mm infiltration depth into the presintered alumina at 1150°C, 1200°C and 1250°C required 95 min, 22 min and 8 min, respectively. Conclusion: An optimal infiltrating time required to reach a suitable infiltration depth into the presintered alumina was observed at 1200°C, an important finding for clinical applications at this commonly used furnace temperature.

Abstract: In this work lithium disilicate glass-ceramic and glasses based on the Li2O-SiO2 system have been investigated by replacing the high-purity SiO2 starting powder by silica obtained from rice husk. Glasses were developed at the stoichiometric composition of 66%.molSiO2:33%.molLiO2 using SiO2 obtained by thermochemical treatment of rice husk. The influence of rice husk-SiO2 on phase formation, microstructure, hardness and fracture toughness was determined and discussed. Investigations were carried out by means of differential thermal analysis, X-ray fluorescence, X-ray diffractometry and scanning electron microscopy. Amorphous and transparent glasses were obtained after melting. The glasses presented Tg near to 480 0C, crystallization peak at 660 0C in both glasses from different silica sources and Li2Si2O5 as the crystalline phase after heat treatment. The hardness (HV300gF) presented average values near to 430 HV for both high-purity and rice husk silica powders. Fracture toughness measurements present results near to 1.7 MP am1/2 for both compositions.

Abstract: In this work itria stabilized ZrO2 based ceramics for dental applications has been sintered and characterized in terms of physical and mechanical properties. Nanostructured blocks were sintered at 1400 0C and microstrutured blocks sintered at 1600 0C. Both nanostructured and microstructured materials were characterized in terms of densification, crystalline phases, mechanical properties and microstructure. Fracture toughness and four point bending strength were evaluated and compared. For the nanostructured zirconia, the reduced grain size allowed the increase of its toughening capacity, generated from maximization of volumetric fraction of retained tetragonal zirconia particles. For this material higher bending flexural strength is related to induced nucleation of microcracks, increase of energy absorption during crack propagation and developed compressive surface stress. The fracture toughness obtained at nanostructured samples sintered at 1400 0C is approximately 20% higher when compared to microstrucutured samples. These results represent the toughening ability of nanostructured zirconia, originated from higher amount of retained tetragonal phase and grain boundary microcracks. The higher Weibull moduli in this case are indicative of material reliability improvement and these results are correlated to grain size and its influence at mechanical strength.

Abstract: In the acidic oral environments containing fluoride ions, hydrofluoric acid (HF) would form and affect the color of Titanium porcelain crown, but there is a lack of information on how color is affected by this oral fluid. The purpose of this study was to investigate the effects of various artificial saliva simulating oral environments in the presence of fluoride ions with different pH value on the color of self-made dental opaque, body porcelain, belonging to the Na2O-K2O–MgO–CaO–Al2O3–SiO2 glass system. Disc-shaped specimens, 5 mm diameter and a 2-mm thickness, were made by firing. Specimens were immersed in artificial saliva in the presence of fluoride ions with different pH value for 7, 14, 21 days, and then the color of the specimens was compared with the color of the initial specimen. The interactions were present in L*a*b* values between pH value and the day of immersion. The changes in L*a*b* color data as the day of immersion and pH value increased were revealed, which can resulted in perceptual color changes in L*a*b* color parameters.