By: Professor Chen Yaming
The development of crown restoration technology has allowed for the preservation of many teeth that would have otherwise required extraction. However, during the extensive use of crown restorations, some issues have emerged.
Speaking of this, I recall a student from the School of Stomatology at Nanjing Medical University, where I used to work. After interning at a tertiary specialized dental hospital, she was deeply frustrated by the chaos surrounding crown restorations at that time. She even wrote me a letter expressing her feelings.
Here is a quote from her letter: “What struck me the most during my internship in the Department of Oral Medicine was the artificial dental diseases caused by many crown and bridge restorations! There were cases where gingival pockets formed due to overhanging or incomplete removal of cement, leading to alveolar bone resorption and eventual tooth mobility necessitating extraction. There were also cases where poor contact between the crown and tooth resulted in severe food impaction, leading to tooth decay. Furthermore, ill-fitting margins caused root surface caries in some cases. Once, one of my patients from the Department of Oral Medicine vehemently refused crown restoration in the prosthodontic department. The reason was that a week earlier, the patient had to have the tooth extracted due to crown restoration-induced periodontitis…”
Looking back at these words, one can still sense the intern’s frustration at that time. Many years have passed, and this intern is now likely a chief physician. I wonder if she still remembers the letter she wrote and the emotions she had at that time.
Porcelain-fused-to-metal crowns are priced higher than simple “steel crowns,” which has attracted some doctors to abuse the treatment without considering the patients’ actual conditions. This has also caused some dentists who have no understanding of restoration to attempt porcelain-fused-to-metal restorations in clinical practice, with predictable consequences.
In terms of materials for porcelain-fused-to-metal crowns, some new situations have emerged. Initially, nickel-chromium alloy or cobalt-chromium alloy was used for the inner layer of porcelain-fused-to-metal crowns. Later, “titanium alloy porcelain-fused-to-metal crowns” appeared, with claims that titanium metal is superior to nickel-chromium or cobalt-chromium alloys, justifying the higher prices. Indeed, titanium is an excellent metal material, but basic chemistry knowledge tells us that titanium has a melting point above 1700°C, and the melting process must be carried out in an inert gas environment. However, the porcelain powder used for porcelain-fused-to-metal crowns has a melting point of only about 1000°C. How can these two be compatible? In fact, the titanium content in the titanium alloy used for porcelain-fused-to-metal crowns is only around 4%. The titanium content in “titanium alloy” is extremely low, strictly speaking, it can only be called “titanium-containing alloy steel.” It cannot be considered a “high-end” material.
In order to attract attention, various media outlets have bombarded the public with all sorts of dental advertisements, aggressively promoting porcelain-fused-to-metal restorations. This has created a sense of saturation and even dental promotional ads can be seen on the backrests of public buses, leaving people speechless!
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