Our teeth, just like any other part of the body, will naturally degrade over time due to repeated use. This may cause aesthetic and functional damage to your teeth, and such cases are usually treated by placing ceramic materials over damaged teeth in the form of dental crowns and veneers.
Such ceramics are referred to as dental ceramics or dental porcelain, and their examples include feldspathic porcelain, zirconia ceramics, and alumina-based ceramics.
Surprisingly, our teeth are subjected to a wide range of temperatures due to different kinds of food that we introduce into our mouths, from a sip of hot coffee to a bite of ice-cold popsicles. These changes in temperature cause our teeth to expand and contract, as well as any dental crowns and veneers that may be placed over them. This phenomenon is called thermal expansion and contraction, and is illustrated in Figure 1.
Figure 1: Thermal Expansion and Contraction of Dental Materials.
However, different materials expand and contract at different rates. The material property that quantifies this degree of thermal expansion and contraction is called the coefficient of thermal expansion (CTE). Table 1 shows the CTE values for common materials used in dental restorations.
Table 1: Typical CTE values for common dental restoration materials (https://pocketdentistry.com/2-properties-of-materials/).
| MATERIAL | COEFFICIENT (× 106/°C) |
| Human Teeth | 8 – 15 |
| Ceramics | 8 – 14 |
| Glass ionomer base | 10 – 11 |
| Gold alloys | 12 – 15 |
| Dental amalgam | 22 – 28 |
| Composites | 25 – 68 |
| Unfilled acrylics and sealants | 70 – 100 |
| Inlay wax | 300 – 1000 |
In the context of dental ceramics, if the ceramic material’s CTE is significantly different than that of teeth, it may lead to leakage of oral fluids between the restoration and the teeth. Furthermore, in some veneers, a ceramic cap is placed over a metallic substrate, where two materials may have different values of CTE. This may lead to thermal stress being imposed on the veneer over repeated applications.
To ensure the durability of the dental ceramics against thermal stress, the material’s CTE must be well characterized. One of the main methods for measuring CTE is the thermomechanical analysis (TMA) technique.
Rigaku’s TMA8311 allows for quick and simple characterization of ceramic materials’ CTE over a wide range of temperatures, ensuring the compatibility of thermal expansion behaviour between the dental ceramics and the teeth.
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About the Author
Hitoshi Taniguchi is a Technical Specialist at C-Therm Technologies Ltd.. Hitoshi recently received his Bachelor of Science in Chemical Engineering from the University of New Brunswick and has swiftly made the transition from academia to industry. He is a certified Installation Technician for various pieces of thermal analysis equipment distributed by C-Therm and has played a significant role in developing new technologies and testing protocols at the company. With a strong interest in R&D, his daily tasks such as data acquisition, analysis, and technical presentations directly contribute to the development of new products. His previous experiences as a tutor for chemical engineering and mathematics courses show his passion in helping students succeed in academics.