There are two objectives. One is to show the differences in the mechanical properties of various dental restorative materials compared to those of enamel and dentin. The other is to ascertain which dental restorative materials are more suitable for clinical treatments. Amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were processed as dental restorative material specimens. The specimens (width, height, and length of 1.2, 1.2, and 3.0 mm, respectively) were compressed at a constant loading speed of 0.1 mm/min. The maximum stress (115.0 ± 40.6, 55.0 ± 24.8, 291.2 ± 45.3, 274.6 ± 52.2, 2206.0 ± 522.9, and 953.4 ± 132.1 MPa), maximum strain (7.8% ± 0.5%, 4.0% ± 0.1%, 12.7% ± 0.8%, 32.8% ± 0.5%, 63.5% ± 14.0%, and 45.3% ± 7.4%), and elastic modulus (1437.5 ± 507.2, 1548.4 ± 583.5, 2323.4 ± 322.4, 833.1 ± 92.4, 3895.2 ± 202.9, and 2222.7 ± 277.6 MPa) were evident for amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy, respectively. The reference hardness value of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy was 90, 420, 130–135, 86.6–124.2, 1250, and 349, respectively. Since enamel grinds food, its abrasion resistance is important. Therefore, hardness value should be prioritized for enamel. Since dentin absorbs bite forces, mechanical properties should be prioritized for dentin. The results suggest that gold alloy simultaneously has a hardness value lower than enamel (74.8 ± 18.1), which is important in the wear of the opposing natural teeth, and higher maximum stress, maximum strain, and elastic modulus than dentin (193.7 ± 30.6 MPa, 11.9% ± 0.1%, 1653.7 ± 277.9 MPa, respectively), which are important considering the rigidity to absorb bite forces.

The application of β-cyclodextrin (CD) to remove unattractive volatile compounds has been applied in various food products. This study investigated the effect of CD concentration (1–4%) on the beany flavor masking and textural modification of yuba film prepared by isolated soy protein (ISP) in the presence of (+CD), or after removing, the flavor-entrapped CD (−CD). Based on gas chromatography–mass spectrometry (GC–MS), the addition of CD caused a decrease in 1-octen-3-ol, benzaldehyde, hexanal, and 2-heptanone, which are characterized as the major beany flavor compounds. Regardless of presence or removal, the use of CD was effective in reducing beany flavor in yuba film. Scanning electron microscopy (SEM) observation indicated that the CD present in yuba film was distributed on the lower surface and matrices of the films. In yuba film containing 4% CD, the CD crystals were concentrated on both the upper and lower surfaces of the film. The textural properties of the yuba film were affected by the presence or removal of CD, and better puncture strength was obtained when yuba was made after removing the CD. Therefore, this study indicates that the addition of CD was a good approach to mask the beany flavor of soy protein-based products, and textural properties could be improved by removing CD from the product formulation.

The dental hard tissues of a tooth are combined of enamel and dentin together. The enamel protects the dentin and comes in direct contact with food during mastication. Bite force is expressed as compression force. The purpose of this study is to identify the primary roles of enamel and dentin during mastication by analyzing their mechanical properties and hardness. Healthy human teeth (age: 19.3 ± 4.1) were used as specimens for mechanical tests. The teeth, which underwent epoxy resin molding, were machine cut to make 10 enamel specimens, 10 dentin specimens and 10 enamel–dentin composite (ED) specimens of 1.2 mm × 1.2 mm × 3.0 mm (Width × Height × Length) in size. Compression tests were conducted using a micro-load system at 0.1 mm/min test speed. Teeth surface hardness (HV) was measured by a Vickers diamond indenter with a 300g indentation load. Data were obtained from 4 points on each enamel specimen and 4 points on each dentin specimen. The strain (%), stress (MPa) and modulus of elasticity (E, MPa) of the specimens were obtained from compression tests. The MAX. strain of the enamel, dentin and ED specimens were 4.5 ± 0.8 %, 11.9 ± 0.1 % and 8.7 ± 2.7 %, respectively. The MAX. stress of the enamel, dentin and ED specimens were 62.2 ± 23.8 MPa, 193.7 ± 30.6 MPa and 126.1 ± 54.6 MPa, respectively. The E values of the enamel, dentin and ED specimens were 1338.2 ± 307.9 MPa, 1653.7 ± 277.9 MPa and 1628.6 ± 482.7 MPa, respectively. The E of the dentin specimens was the highest and the E of the enamel specimens was the lowest, but the E values of all specimens was not significantly different in the T-test (P > 0.1). The measured hardness value of the enamel specimens (HV = 274.8 ± 18.1) was about 4.2 times higher than that of the dentin specimens (HV = 65.6 ± 3.9). Because of the values of MAX. stress and MAX. strain of the enamel specimens, the enamel specimens tended to fracture earlier than the dentin and ED specimens; therefore, enamel was considered to be more brittle than dentin and ED. Enamel is a harder tissue than dentin based on their measured hardness values. Therefore, enamel has a higher wear resistance, making it suitable for grinding and crushing, whereas dentin has a higher force function, making it suitable for abutment against bite force.

Tooth reconstruction materials are used to reconstruct damaged teeth as well as to recover their functions. In this study, the mechanical properties of various tooth reconstruction materials were determined using test specimens of identical shape and dimension under the same compressive test condition; the hardness values of them were obtained from previous studies and compared with those of enamel and dentin. Amalgam, dental ceramic, dental gold alloy, dental resin, zirconia and titanium were processed as tooth reconstruction material specimens. For each material, 10 specimens having a of 3.0 × 1.2 × 1.2 mm (length × width × height) were used. The stresses, strains, and elastic moduli of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were obtained from the compressive test. The hardness values of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were obtained from the references [14–19]. And, the stresses, strains, elastic moduli, and the hardness values of enamel and dentin were obtained from the reference [13]. The mechanical role of enamel is to crush food and protect dentin because of its higher wear resistance, and that of dentin is to absorb bite forces because of its higher force resistance. Therefore, the hardness value should be prioritized for enamel replacement materials, and mechanical properties should be prioritized for dentin replacement materials. Therefore, zirconia and titanium alloy were considered suitable tooth reconstruction materials for replacing enamel, and gold alloy, zirconia, and titanium alloy were considered suitable tooth reconstruction materials for replacing dentin. However, owing to the excessive mechanical properties and hardness values of zirconia and titanium alloy, these may show poor biocompatibility with natural teeth. Thus far, no tooth reconstruction material satisfies the requirements of having both a hardness value similar to that of enamel and mechanical properties similar to those of dentin.

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