It is useful to review how and why ceramics came to be used in dentistry, and this introduction serves three purposes: (1) to alert practitioners to the fact that the use of ceramics has always represented the adoption of high technology, not borrowed craft art; (2) to reinforce the concept that ceramic technology and improved ceramics were introduced to solve specific problems or to increase restorative versatility; and (3) to provide some background into the nature and science of ceramics. (Astute readers will also find clues about where to watch for the emergence of new ceramic technologies.)
In the Beginning
In the late 1600s and early 1700s, many European rulers and aristocrats were dispensing enormous sums to import porcelain from China and Japan. Schloss Charlottenburg in Berlin has an impressive assortment of porcelain, and Fig 1-1 represents just a small portion of the collection. Augustus II of Saxony (who was the reigning King of Poland and Elector of Saxony at the time) amassed one of the largest collections in Europe; it is now on display at Dresden’s Zwinger Museum housed in his former palace. Such expensive activity led China to be characterized as the “bleeding bowl” of Europe. Between 1604 and 1657 alone, over 3 million pieces of Chinese porcelain reached Europe.1 In just one day in 1700, East Indiamen ships unloaded 146,748 pieces of porcelain in a European port as the market for porcelain became insatiable.1
Fig 1-1 A small portion of the china collection from Schloss Charlottenburg in Berlin.
One response to this situation involved state-sponsored research into porcelain discovery. Notable European leaders, including Augustus II the Strong and the Medici family of Florence, were independently sponsoring research into the development of a European porcelain to match the hard, translucent, and sonorous material developed in Eastern Asia nearly 1,100 years earlier. Europeans strived for porcelain discovery without much success for about 200 years, and this activity is credited with the growth of modern analytical chemistry from its roots in alchemy. Figure 1-2 shows the historical timeline of porcelain discovery.
Fig 1-2 Timeline for the development of several related porcelains.
State-sponsored research into porcelain discovery initiated in France and the Germanic state of Saxony in the late 1600s. The efforts of Count Walther Von Tschirnhaus in developing the mineral resources of Saxony on behalf of Augustus II were particularly important for dentistry. He used a series of large “burning lenses” (magnifying glasses up to 1 meter in diameter) to create a solar furnace; these lenses directed to a focal spot, allowing Von Tschirnhaus to subject minerals to extensively high temperatures, easily in excess of 1,436°C.2
Meanwhile in Berlin (in the Germanic state of Prussia), Johann Friedrich Böttger was manipulating metals as a journeyman apothecary. Böttger’s parlor trick involved melting base metals such as silver coins and then adding a dose of the Arcanum of the philosopher’s stone.3 When poured into molds and cooled, the resulting product was analyzed to be pure gold! Böttger inadvisably performed this “transmutation” demonstration at his employer’s house to impress some important guests, resulting in a summons by King Frederick I of Prussia for a command performance. Placing discretion ahead of valor, Böttger fled south to Saxony, where he attempted to study medicine at Wittenberg University. Wanted posters appeared in Berlin, and a price was put on the head of Böttger. For the local representative of Augustus II in Wittenberg, the arrival of a contingent of a dozen troops from King Frederick seemed excessive for the capture and return of a supposedly common criminal. Therefore, Böttger was placed under house arrest for months while Augustus was alerted and the situation explored. With the presence of foreign troops confounding the situation, Böttger was finally spirited away by coach in the dead of night, using back roads to avoid Prussian troops, and delivered to Augustus in Dresden. To further deceive the Prussians, the Saxons continued to bring food to the room of Böttger. For any state needing to support armies, Böttger’s ability to turn base metals into gold was simply too important to let slip away, so Böttger was held as a prisoner under the wing of Von Tschirnhaus to perfect gold production.
Serendipity and a clever intuition prevailed to save Böttger from certain execution following over 3 years of unsuccessful gold making, a project costing Augustus a small fortune. Experimenting with his burning lenses, Von Tschirnhaus had discovered that while neither sand nor lime (calcium oxide) would fuse individually, they would do so when combined; in fact, the resulting white product looked suspiciously like porcelain. What had been discovered was the use of a “flux” to create lower melting intermediate compounds, promoting glass formation and allowing the fusion of the high-silica sand. Because it was known that high-quality clay was a major ingredient in Chinese porcelain, Saxony was secretly scoured for sources of the purest clay. Böttger, whose expertise in chemistry was by then extensive, realized that porcelain had to have a glassy component resulting from very high–temperature reactions. Building on the discovery of Von Tschirnhaus, he reasoned that lime added to clay was worth exploring.
Between 1704 and 1708, research was conducted under extreme secrecy beginning in the Albrechtsburg Castle, which still exists in the city of Meissen, Germany (Fig 1-3), and then in the dungeon basement of the feared Jungfernbastei (Maiden’s Bastion) in Dresden (Fig 1-4a). Böttger used what is known today as the “Edisonian approach,” whereby a wide variety of formulations are systematically tried. Figure 1-4b shows a page from his laboratory notebook memorializing the successful mixture of clay and lime (obtained from calcined alabaster that was pulverized and heated to drive off water and sulfur, leaving fine calcium oxide powder).
Fig 1-3 Recent photograph of Albrechtsburg Castle in Meissen, Germany, the site of an early porcelain discovery laboratory and the first manufacturing site of European porcelain rivaling that from China. Today’s Meissen factory and museum are located nearby.
Fig 1-4 (a) Early depiction of the feared Jungfernbastei (Maiden’s Bastion) in Dresden, the site of Böttger’s secret porcelain discovery research. (b) Page from Böttger’s laboratory notebook memorializing the successful mixture of clay and calcined alabaster in January 1708.
Manufacturing operations were moved back to Albrechtsburg Castle, and by 1708 the first pieces were being demonstrated at the Leipzig Easter Fair, with production for sale beginning in 1710. Around that time, Böttger substituted feldspar for lime as the flux, a move that (1) cleanly put the Meissen formulation within that of the Chinese “triaxial” porcelains (Fig 1-5) and (2) introduced