In the 1800s, some dental fillings were known to explode inside patients' mouths.

During the 19th century, dentistry was largely unregulated and practitioners experimented with various metallic alloys for fillings. These mixtures often included silver, tin, lead, and copper, which were packed into cavities to stop decay. When two dissimilar metals are placed in an acidic environment like human saliva, they create a galvanic cell. This electrochemical reaction generates a small electrical current and can lead to the electrolysis of water or other chemicals in the mouth.The primary byproduct of this specific chemical reaction is hydrogen gas. Because the fillings were often sealed tightly into the tooth structure, the gas had no way to vent or dissipate. Over time, the internal pressure would reach critical levels within the confined space of the pulp chamber. This phenomenon was documented in various medical journals of the era, including a notable report by Dr. W.H. Atkinson in the 'Dental Cosmos' journal in 1860.One famous case involved a clergyman in 1817 whose tooth exploded with such force that it nearly knocked him over. Another instance in 1871 described a woman whose tooth shattered with a bang so loud it caused temporary deafness in one ear. Modern amalgam fillings are much more stable and do not pose this risk because the chemical composition is carefully controlled. Today, the use of composite resins has largely replaced these volatile early metal mixtures entirely.