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The Joy of High Tech


Rodford Edmiston

Being the occasionally interesting ramblings of a major-league technophile.

The Bit Between Your Teeth

      The requirements of medicine have frequently driven technological development. Dental tools alone have stimulated major accomplishments in stainless steel and similar materials, because of the strength, elasticity and corrosion resistance needs involved. When you consider that some of these have to actually operate at high speed with great precision while cutting away something as hard as tooth enamel, then be sterilized for subsequent use...!

      Most people are wary of modern, air-driven mini-turbine dental drills. Trust me, the old, mechanical ones were far worse. Especially before electric motors were added, and they had to be bowed, pedaled, cranked or wound. Often by the dentist, while he was working! The essential difference is speed. Typical modern drills spin at up to four hundred thousand RPM, with some specialty drills going as high as 800K! Just getting something to hold together at such speeds is difficult.

      The oldest dental drills were likely small bow drills with tiny flint chips for bits, probably adapted from bead drills. There is evidence for these and other custom tools being used for dental work in the Indus Valley going back about nine thousand years. (Said evidence including teeth which have obviously been drilled, some of them as deeply as 3.5 mm.) Then as now, not all dentistry was for health reasons; there are multiple examples from that era of human teeth which are artistically modified. Some of the decorations are very fine and intricate. Likely, the practice of drilling out decay evolved from this.

      The myth of tooth worms sprang up in multiple locations around the world in antiquity. That is, toothaches were thought to be cause by tiny worms which dug into the teeth and made them hurt. (Actually not far from the truth. Just substitute microscopic single-celled organisms for worms.) Drilling out cavities may have begun as an effort to find and remove these "worms."

      However drilling out decayed spots was developed, it was long recognized that when drilling teeth, faster was better. Bow drills were replaced by cranked drills, which gave more control but speeds of only about 15 RPM. Throughout the second half of the Nineteenth Century inventors worked on ways to increase the rotational speed of dental drills. There was a proliferation of cranked, pedaled and even spring-wound engines of dental care, many of them intimidating constructions of ironmongery. Dental offices of the period sometimes resembled torture chambers, despite such decorative touches as fringes on the velvet-covered seat cushions.

      The first electric powered dental drill patent was filed in 1875, and things began looking up. By 1914 drills were turning as fast as 3000 RPM. In 1868, American dentist George F. Green came up with a pneumatic dental drill. Unfortunately, it was powered by a pedal-operated bellows. This made it little better than the purely mechanical drills of the time, though it showed the way to something much better.

      Practical air turbine drills came along in the Nineteen-Fifties, and were much improved in the Sixties. The modern incarnation of the dental drill is the air turbine handpiece, developed by John (later Sir John) Patrick Walsh and members of the staff of the Dominion Physical Laboratory in Wellington, New Zealand. Dr. Walsh was granted a provisional patent for the now-typical handpiece in October 1949. He based it on an existing miniature angle grinder, though the actual patented design used a different angle. The first commercial air-turbine dental drill was manufactured in the US in 1957.

      Then there are the dental burs. These are usually made of high-strength stainless steel, tungsten, or some similar material, and coated with tungsten carbide or diamond. Some burs are made entirely of tungsten carbide. These are cutters, rather than grinders, which operate more slowly.

      One reason for using cutters is that slicing tiny chips out of teeth generates less heat than grinding with an abrasive. Even with water cooling of the burr and tooth, this is an important concern. The water also serves to flush away material which might obstruct the dentist's view of the work. You definitely want people working on your teeth to be able to see what they're doing.

      Today, for some work lasers (which explosively ablate tiny bits of tooth with short, intense bursts of light) and what are essentially miniature sand blasters are used. There is even exploration of the use of tiny jets of plasma for the job. Whether any of these will provide a significant improvement over the high-speed cutting burr remains to be seen. Regardless, once the excavation is completed, the filling must begin.

      Gold - along with some of its alloys - is in most respects an excellent material for dental work. It is soft enough to be shaped easily, doesn't corrode, and holds up surprisingly well (a gold crown might last more than thirty years). However, gold conducts heat very well, which can cause discomfort or worse, and the metal is expensive. Historically, other materials used for fillings include: gold alloys, silver, platinum, lead (!) amalgams, tin, aluminum, asbestos (!!), steel, chromium alloys, porcelain, thorium (!!!) (this was found in a number of Civil War era teeth by later researchers, the metal has physical and chemical properties close enough to tin that under the circumstances it was probably mistaken for that metal), mercury amalgam and titanium. Current amalgam fillings use less mercury than older compositions and are more chemically stable, with very little loss of mercury, at least while intact. Composite fillings are less durable than amalgam, but improving. Glass composite fillings are used for temporary work, and may soon be used for permanent filling.

      Gutta percha - a particular form of latex from a specific genus of tropical trees - wouldn't make a good permanent filing, but it has been used as a dental material for well over a century. Today it's most common application is in root canals, to fill the spaces left by the living tissue which is removed. Gutta percha has a number of interesting properties, one of the most useful being that it is biologically inert. Gutta percha is different enough from standard latex that the modern consensus is that someone allergic to the latter is very unlikely to have a reaction to the former.

      Drilling and filling are, of course, remedies. Prevention may be much older. People have been picking and flossing their teeth for thousands of years. We know this because museums have old teeth with grooves typical of picking and flossing. Numerous materials have been used for picking, including porcupine quills. Likewise, many plant and animal fibers have been used to clean between teeth, with silk thread being among the most successful.

      Exactly when people began brushing their teeth is unknown. Primitive peoples today are known to chew certain types of twigs and use the altered end to clean their teeth. This sort of brush wouldn't preserve very well, of course. However, there are known examples. A chewed stick almost certainly used for oral hygiene has been dated to about 3000 BC. We also know the Chinese were making for-purpose tooth brushes centuries ago.

      The Chinese probably also invented the practice of scraping plaque from teeth to prevent cavities. Indeed, among the services performed by the first Chinese in the New World was cleaning the teeth of the Europeans who conquered that land.

      The first real Chinatown in the New World grew in Mexico City in the early Seventeenth Century. Most of the inhabitants were Christians who came to the New World with the pacific trade (which largely consisted of silver heading west and silk and porcelain heading east, but there was also a substantial movement of people). They brought many things with them, among those advanced (for the era) dental care.

      At this time, barbers were the primary providers of basic medical care, including dentistry. (Tooth care and hair cutting may seem to be disparate services, but both are hygiene related. Also, I'm certain most readers of this are aware of where the red stripes in the barber's pole come from.) Chinese medicine was arguably the most advanced in the world then, surpassing even that of the Arabs. Moreover, those who came to the New World often learned from European practice and combined the best of that with their own. The resulting dental services they provided - which included scraping plaque from teeth - gave both immediate aid and long-term benefit far beyond what was typical in Europe. Their success rates were higher for extractions and surgery, due in large part to an herbal paste which is today known to have both antibiotic and anti-inflammatory properties. Their knowledge included radical (from the European viewpoint) concepts in dental care. Finally, they were often cheaper (for better work) than their European counterparts.

      Having this resource available was so obviously beneficial - and became so popular among wealthy Spaniards and others - that even when segregation laws were passed in Mexico City to control Chinese merchants, barbers and so forth, the dentists were effectively exempted.

      Repeatedly, materials and methods developed specifically for dentistry have driven both materials science and engineering generally. Even when dentistry didn't drive technology, it has often been an early adopter. Nylon was first used for toothbrushes in 1938. Dr. Charles C. Bass adapted nylon for use as dental floss shortly after the wonder material was developed. However, due to World War Two it wasn't widely adapted until after the War.

      Before nylon, most toothbrushes used things such as hog bristles, mounted in handles of wood or perhaps bone or ivory. These were understandably less durable and less sanitary than modern brushes. Today the majority of bristles are still made of nylon. This has multiple physical and economic properties which make it as close to idea as we're likely to get any time soon. With nylon, even the stiffness of the bristles can be adjusted, to made a brush soft, medium, or firm.

      The evidence for toothpaste doesn't go back quite so far as that for tooth brushing. The ancient Greeks used a mix of crushed bones or sea shells as a tooth powder. Later formulations of tooth powders involved chalk, pulverized brick, salt and pulverized charcoal. As might be imagined, some of these did more harm than good. How much harm was likely not realized in full, due to short life spans from other causes. By the beginning of the 20th Century a mixture of hydrogen peroxide and baking soda was being recommended. The first manufactured toothpaste in a tube was invented in 1892, when Dr. Sheffield's Creme Dentifrice went on the market. Dr. Sheffield (yes, he was a real, medical doctor and dentist) was inspired by artist paints in tubes. His product was developed and marketed by Colgate & Company.

      Regardless of how well people brush and floss and how good the brushes and floss are, some folks are going to need work on their teeth. That means dealing with sensations ranging from unpleasant to agonizing.

      Novocain - a brand name of procain - was first introduced in 1905, and probably used in dentistry immediately afterwards. Millions of people still sigh with relief after the shot starts working, no matter how much they cringe as the needle approaches.

      Nitrous oxide has an even older history of alleviating dental pain. Horace Wells used it on a patient on December 11, 1844. However, due to difficulties in administering the gas, a patient would often get too little or, worse, too much. Today Nitrous is most commonly used as an adjunct to relax patients, with the actual pain relief coming from a local injection.

      There is one area of dental technology which keeps promising much but somehow never delivering. Every few years, I read a breathless announcement that researchers have developed a coating for teeth which will seal them and eliminate cavities. Then nothing, until the next breathless announcement of a remarkable new development which will et. cetera, et. cetera.

      Oddly, I never hear why the previous development didn't work out.

          This document is Copyright 2015 Rodford Edmiston Smith. Anyone wishing to repost it must have permission from the author, who can be reached at: stickmaker@usa.net