Journal of the Massachusetts Dental Society - Winter 2014

Dental Technology Over 150 Years: Evolution and Revolution

Paul Feuerstein 2014-01-19 21:58:40

A patient entering a dental office is often greeted and then checked in through the practice management system’s digital appointment book. The provider is notified by an electronic signal that is visual, audible, or both. The patient is led to the treatment area and sits in a dental chair, which is adjusted to the individual’s size and position for the treatment, and the light is positioned. Sometimes a radiograph is taken, local anesthetic is delivered, and a handpiece—air turbine or electric—is used for the procedure. How different is this process today from a dentist treating a patient in 1864? Understating the obvious, there have been remarkable advances in dentistry over these past 150 years, many due to changes in technology. Mechanical engineers have reinvented dental chairs and handpieces. Pharmacology and chemistry have evolved exponentially, changing the materials and processes we use. Computers have become embedded into dental equipment, as well as the management side of the office. Many of these changes over the past 150 years will be looked at in this article. When you think of technological advances in dentistry, you may think of radiography and computers. Digital radiography and new 3-D cone beam tomography have obviously evolved through the years, and there are few, if any, offices that do not have a computer system to help manage the bookkeeping of the office. However, look around your operatory. Practically everything you use on a daily basis to treat your patients has been improved upon because of technology. Toothbrushes For example, the simple toothbrush has gone high-tech. The first natural brushes were invented in ancient China using the bristles from the necks of pigs. The 17th and 18th centuries had dentists in France promoting the use of toothbrushes, while later in England, William Addis created the first mass-produced model. The first American to patent a toothbrush was H. N. Wadsworth, and many U.S. companies began to mass-produce toothbrushes after 1885. Right here in Massachusetts, the Pro-phy-lac-tic toothbrush made by the Florence Manufacturing Company is one example of an early American-made toothbrush. Florence Manufacturing was the first to sell toothbrushes packaged in boxes; an interesting aside is that during World War II, it also manufactured dummy plastic training bayonets for the U.S. Navy.1 It wasn’t until 1938 that the first nylon bristle toothbrush was manufactured by DuPont. The first electric toothbrush was developed in Switzerland by Dr. Phillippe- Guy Woog in 1939, but it wasn’t released until 1954. In 1960, Squibb marketed the first American-made electric toothbrush called the Broxodent. General Electric introduced a rechargeable cordless toothbrush in 1961, and in 1987, Interplak was the first rotary-action electric toothbrush for home use.2 Powered brushes have continued to evolve with numerous models that either rotate (fully or partially) or vibrate (sonic or ultrasonic), or a combination of the two. Oral-B and Philips Sonicare are probably the most visible in the current marketplace, with variations and features from UV sterilization of the heads to USB recharging. There are even new models that are Bluetooth enabled and can record a person’s brushing time and even technique, answering the question for your children, “Did you brush last night?” Dental Chairs The first adjustable dental chair was invented in 1790 by Josiah Flagg, who is also credited with being the first American dentist.3 Dr. Flagg began with a large, wooden Windsor chair and modified it to accommodate an adjustable headrest. (Before this, dental patients sat in a wooden chair without any headrest at all.) Forty years later, James Snell designed and created the first fully reclining dental chair, which was an improvement, but it still sat on four legs.3 The first pump-style chair incorporated the adjustable features of the Snell model and provided a foot pump that raised and lowered the patient. In 1867, British dentist Dr. James Beall Morrison constructed a chair that could be raised up to three feet.3 It allowed the patient to recline fully, and it was also capable of tilting to the left and right. By the way, in the 1880s, Dr. Alfred Southwick, a dentist in Buffalo, New York, invented the electric chair that would be used for execution, since he claimed he “was accustomed to performing procedures on subjects in chairs.”4 In 1887, Dewell Stuck had an idea for a new type of dental chair. After being turned down by a barber chair manufacturer in Rochester, New York, he was introduced by a mutual friend to Frank Ritter, who was a cabinetmaker with a furniture upholstering business. The original Stuck Dental Chair had a completely dry movement, with no oil used whatsoever. The Stuck Chair was the first chair to have a disc base, the other dental chairs of that day being supported on four legs. In 1891, the Celebrated Columbia Chair (also called the “Jacknife Chair”) was introduced. It was the first chair to use hydraulic pressure for the raising and lowering mechanism, and it was able to be raised higher and positioned lower than other chairs on the market. By 1893, the famous New Columbia Chair was introduced and sold more than 6,500 units. Ritter Dental went on to create other products, including 1915’s Dental Operating Unit, which combined the services of air, water, gas, and electricity in one compact assembly, thus bringing together all operating essentials to the side of the Ritter Chair.5 Twentieth-century dental chairs continued to evolve, designed mostly for stand-up dentistry until some models were introduced that were geared toward sitdown dentistry. In 1954, a group of dentists, including Dr. Sanford S. Golden, met to develop a reclining chair for patients that would allow the dentist to sit while operating, resulting in the introduction of the Ritter Euphorian Chair.5 Although this chair received an award for being the first dental chair exhibiting a major change in 50 years, it would not permit the patient to be fully reclined without his or her feet going up in the air. The introduction of the Den-Tal-Ez(R) chair by John Naughton in 1958 was the event that ushered in the era of modern sit-down, four-handed dentistry. 6 This chair had an articulated seat and back, and became accepted as the standard by the profession. Many companies have continued to create, modify, and technologically advance dental chairs. Pelton Crane, for example, has been in existence for more than 100 years, and its “Chairman” chair was so successful that, despite its being out of production, many dentists are still having these chairs serviced, upgraded, and reupholstered due to patient comfort and the unusual “traverse” function that moves the chair forward and back. This is a tribute to its durable design. Modern dental chairs offer an ever-increasing list of benefits for patients and dental professionals. They are built out of aluminum, steel, and heavy plastic, and most offer smooth electric or hydraulic height and tilt adjustments. Earlier dental chairs often lacked padding and were constructed from bare wood; if they had any fabric covering at all, it was sewn from upholstery fabric. This made the chairs very difficult to sanitize between patients, particularly if the fabric was not easily removable. Newer padding provides greater patient comfort. The modern chair typically has a vinyl covering that is impregnated with an antimicrobial substance, such as Microban. If any bodily fluids come in contact with the chair, the microbes will quickly die. Vinyl is also very easy to wipe down and tolerates strong disinfectant cleaners. Dental chairs are ergonomically designed to fit the contours of the patient’s body, and newer designs are more aesthetically pleasing to patients. The newer models also usually have integrated electronics and computer controls with memory functions. More and more chairs also have circuitry that allows integration of multiple devices with onefoot control, which means fewer wires and hoses in the way of providers and patients. A typical new dental unit has handpieces, sonic and ultrasonic cleaning devices, intraoral cameras, curing lights, and other equipment integrated with these chairs. The Dental Handpiece Hand burs—the mainstay of drilling techniques in the 18th and early 19th centuries for excavating teeth—probably evolved from ancient techniques. By the 19th century, hand drills with steel bur heads were used, with the long handles being twirled by the fingers. 7 Later, a “bur thimble” was used, and some drills were made bendable by attaching flexible shanks between the bur heads and the handles, which allowed the posterior of the mouth to be accessed. Many other mechanical devices were introduced that advanced the technology of dental drills, including the Lewis drill in 1838, John A. Chevalier’s “drill stock” from the 1850s (or earlier), and Charles Merry’s drill from about 1858.8 George Fellows Harrington demonstrated his “clockwork drill” known as Erado in Great Britain in 1865, describing it as suitable “for drilling, cutting, grinding, and polishing teeth while in the mouth.”8 Wound like a clock, using a large key, Harrington’s drill ran for two minutes per winding, and sold for six guineas. In 1871, Dr. James Beale Morrison patented the treadle engine, which was powered by foot pedals.3 Early drills were difficult to control and operated at low speeds, making excavations tedious. The first electric dental drill was invented in 1868 by George F. Green, a mechanic with the S.S. White Company.8 In 1872, S.S. White put the first electric drill on the market. The motor was incorporated directly into the handpiece, but the majority of dentists used the foot-driven drill because most offices were not electrified. Then in 1893, Doriot’s handpiece was the first design that employed an electric motor to directly power the handpiece. A series of developments in the mid- 20th century led to the use of high-speed instrumentation. In rapid succession, Norlen’s Dentalair (1948) was followed by Walsh’s air turbine handpiece (1949), Nelsen’s water turbine handpiece (1952), and then Page’s belt-driven high-speed handpiece (1955). In 1957, the practice of dentistry was revolutionized overnight by the introduction of John Borden’s Airotor handpiece, which was operated by air and allowed for rotational speeds of up to 200,000 rpm. The handpiece featured miniature ball bearings, and modern air-operated high-speed handpieces have evolved from this design.7 The electric handpiece continued to be refined as an alternative to the air turbine. Micromotors appeared around 1965 and their continuing development has made them lighter and smaller, and an alternative to the air turbines. Due to the precise control of rotation speed—as well as torque control—these handpieces have enhanced some areas of operative dentistry, but probably the biggest impact they’ve had has been in revolutionizing rotary endodontics. Going forward, implant surgery is almost exclusively being performed with electric motors, allowing precision with very slow rotation at the required torque. Alongside the handpieces, cavity preparation using abrasives has been an option that some offices have followed. In 1949, the S.S. White Company brought out a “sand-blasting” device called the Airbrasive, which used compressed carbon dioxide gas to blow a fine stream of abrasive aluminum oxide powder onto the tooth surface.8 It promised to be quieter and more comfortable for the patient, with less heat generation and no pressure on the tooth. Though highly touted, the machine could make only cup-shaped depressions in the enamel, leaving most of the work still to be done by the rotary drill. The patient wore a rubber dam that exposed only the tooth being treated. A large tube, attached to a strong vacuum, sucked up the used abrasive and recycled it. Unfortunately, the collection system was not completely effective; much of the abrasive bounced back off the rubber sheet and into the dentist’s face. Goggles could be used to shield the eyes, but they quickly frosted over. Air abrasion using small particles under pressure to remove tooth structure, though, has not disappeared. There are many new units in the marketplace that use air, helium, or a combination of air and water. They are very useful for small, minimally invasive procedures and often do not require the use of anesthetic. One final note is that in 1955, the Cavitron was introduced.8 It used ultrasonic vibrations to power a metal tip that cut into the tooth with the aid of an abrasive slurry, but it failed because the tip wore away as quickly as the tooth. It should be noted that without the abrasive, the machine has remained a useful tool to remove heavy tartar from teeth. This name has remained through today, and it explains why a periodontal instrument has this operative name.9,10 Lasers Lasers were first used in medicine around 1967–1970, with the advent of the argon and CO2 lasers.11 However, the introduction of laser use in dentistry did not occur until 1989, with the production of the American Dental Laser for commercial use.12 This laser, using an active medium of Nd:YAG, emitted pulsed light and was developed and marketed by Dr. Terry Myers, an American dentist. Though low-powered and, due to its emission wavelength, inappropriate for use on dental hard tissue, the availability of a dedicated laser for oral use gained popularity among dentists. This laser was first sold in the United Kingdom in 1990, and as that decade progressed, the use of lasers in dentistry increased with argon, Nd:YAG, CO2, and semiconductor diodes, but these all were primarily used for soft tissue and not the tooth structure. In 1989, experimental work by Keller and Hibst using a pulsed erbium YAG (2,940 nm) laser demonstrated its effectiveness in cutting enamel, dentin, and bone. This laser became commercially available in the United Kingdom in 1995 and was followed by a similar Er,Cr:YSGG laser in 1997, which launched the operative dentistry lasers we use today.11 For a glimpse into the future of laser dentistry, a new CO2 laser, Convergent, which was just given Food and Drug Administration (FDA) approval for cutting hard tissue, is being developed right in the MDS’s backyard, in Natick, Massachusetts. Caries Detection For ages, the primary instrument for finding caries clinically has been the dental explorer. When a “catch” in a suspicious area was confirmed, a radiograph was grounds for preparing a tooth for a restoration. In several situations, if the catch was not verified, the area was “watched” until it “was big enough to fill.” This goes back to G. V. Black preparations and amalgam as the restorative material of choice.7 There was actually no way to do a “small amalgam.” Even the pits, sometimes filled with gold foil, were still larger than the actual carious area. And the danger of “watching” too long was the advancement of the caries to necessitate a much larger restoration. With the advent of composites and bonding procedures, the dentist could place a much smaller restoration, but at issue was the timing. The explorer was still the standard, and studies began to show that in the case of a shallow decalcification, the explorer might actually puncture the enamel, forcing a restoration in lieu of modern methods of remineralization.13 The restorative topic is too broad for this treatise, but the detection has been evolving rapidly over the past years. Several methods have been used, including liquid caries-detecting dyes, which although more useful during cavity preparation, are not completely reliable, according to a number of studies.14 In 1998, the first technology introduced for caries detection was the DIAGNOdent™ from KaVo, which uses infrared laser fluorescence. It detects and quantifies hypomineralization of dental caries of occlusal and smooth surfaces. Using a diode laser, the light is absorbed and induces infrared fluorescence by organic and inorganic materials. The emitted fluorescence is collected at the probe tip, transmitted to the system, and displayed as a number between 0 and 99— the higher number indicates greater bacterial presence. Other methods of detection use quantitative light-induced fluorescence (QLF), which is based on the autofluorescence of teeth. When teeth are illuminated with high-intensity blue light, they will start to emit light in the green part of the spectrum. The fluorescence of the dental material has a direct relation with the mineral content of the enamel, causing the carious or demineralized areas to glow orange.15 This process has been modified by various manufacturers, who incorporate the technology into intraoral camera devices. The results are instantly displayed on a computer screen, alerting the practitioner (and educating the patient) as to where the carious or decalcified lesions are actually located. Current products such as Air Techniques’ Spectra, Acteon’s SoproCARE and SoproLIFE, and Carestream’s 1600 camera use variations of this technology to act as an adjunct to the aforementioned explorer and digital radiography. There has also been some use of transillumination of the enamel to “see” caries. The simple use of a bright fiberoptic light against the tooth will vividly show fractures and give a hint of decay. There was a product introduced, DIFOTI, that included a camera to record these phenomena, and it seems that KaVo will relaunch this idea with a product to be called DiagnoCam. Another new product, Canary from Canada, is using laser fluorescence as well as heat to sense caries. It is able to map the area in 3-D by having the operator move the wand and internal camera around the area in question. Carestream sensors also have an optional program called Logicon, which actually reads the interproximal areas and shows the potential areas for caries. Looking forward, there are several companies developing other methods of caries detection. We may one day use optical coherence tomography or OCT (Lantis Laser) and ultrasonics to “see” inside of teeth, as well as under and through restorations (S-Ray). In summary, even with all of these technologically advanced devices, the clinician, of course, has to use good clinical judgment. Radiology The history and current state of radiology is one of the most understood evolutions and revolutions by the dental profession. The details need not be chronicled here other than the main points. As we know, in 1895 Wilhem RoÅNntgen discovered X-rays. A German dentist, Dr. Otto Walkoff, produced the first dental radiograph ever recorded with a 25-minute exposure using a glass receptor in his mouth while lying on the floor of his dental treatment room. A year later, in 1896, C. Edmund Kells, a dentist in New Orleans, was the first to use X-rays for dentistry. Unfortunately, he ultimately lost his fingers, hand, and arm due to numerous exposures over the years and eventually died from the effects of excess radiation. In 1913, Kodak produced the first prepackaged dental X-ray film. The packet of waxed waterproof paper contained two pieces of single-coated film. This film basically was still photographic film. In 1919, Kodak produced the first true dental X-ray film designed for direct exposure by X-rays. The packet contained thin sheets of lead to reduce backscatter radiation reaching the film.16,17 Dr. Frank Van Woert was another pioneer of oral and maxillofacial radiology. 18 He made a practical demonstration of dental radiography before the New York Odontological Society in 1897. He was one of the first to use Kodak film (instead of glass plates). These were wrapped in rubber dam and held in place with compound. He later invented a metal film holder, an improved bisecting angulator, an automatic timing switch, and the daylight processing tank.19 Springing ahead to 1987, French dentist Dr. Francis Mouyen invented and introduced digital imaging to the dental profession.17 The system, called RadioVisioGraphy, was launched in Europe by the French company Trophy Radiologie. Dr. Mouyen invented a way to employ fiber optics to reduce down a large X-ray image to a smaller size that could be sensed by a charge coupled device (CCD) image sensor chip. Once the X-ray imaging chip specifications were finalized, Trophy Radiologie contracted Fairchild Imaging Company in Silicon Valley, California, to develop the actual CCD imaging chips. At Fairchild, a young Finnish physicist and CCD image sensor design engineer named Paul Suni helped create the enabling CCD image sensor technology that was needed to make the digital radiography system a reality. The new technology was ready to expand. Two decades later, today’s digital radiographic systems have developed a great superiority and have many benefits.20 For those practitioners who prefer a more filmlike system, phosphor plates have been created to match the sizes of the traditional dental films. These reusable, thin plates are exposed by the X-ray head exactly like the film, and then placed in a “digital developer” that yields an image in as few as five seconds. The plates are erased and can be reused. The next steps were development of a digital panoramic system that is superior to the film-based systems. Due to the location of the sensor, its sensitivity, and the altered route of the moving head, the digital “pans” are crisper and do not have the overlap center void we have been used to seeing. We are now seeing an explosion of 3-D dental imaging, similar to the medical computed tomography (CT) scans that have been available for many years. These new cone beam CT units use more than 80 percent less radiation and the scans take as little as 90 seconds for a full field of view. This imaging will have an impact on diagnosis and treatment planning in all areas of dentistry. There is a lot of effort now being made to integrate this technology with others, such as digital intraoral impressions, implant planning software, endodontic treatment, and more. Dental Anesthesia There is historical evidence that the ancient Chinese used acupuncture around 2700 B.C. to treat the pain associated with tooth decay. In 1846, Dr. William T. G. Morton, a Massachusetts dentist, was the first dentist to use ether as an anesthesia for tooth extraction, rendering the patient unconscious.21 Around the same time, Dr. Horace Wells introduced the use of nitrous oxide for dental anesthesia in the 1840s, and the first anesthesia machines appeared in 1902.22 Although its use fell in disfavor because of its weak anesthetic properties, nitrous oxide continues to be used today for its “second gas effect.” Two main discoveries paved the way for local anesthesia: the discovery of cocaine as an anesthetic in 1884 by Viennese physician Carl Koller7 and the development of the hypodermic syringe in 1851 by French physician Charles Pravaz.22 In 1884, William S. Halsted used a 4% cocaine solution in a hypodermic syringe to deliver the first mandibular local anesthetic block.7 The deficiencies and dangers of cocaine, however, led to a search for a substitute. In 1905, Alfred Einhorn discovered procaine (novocaine), the first widely used anesthetic.7 Other local anesthetic agents were discovered later.22 Today, we have an array of local anesthetics to choose from, including lidocaine, procaine, marcaine, articaine, mepivocaine, and others. Oraverse (Septodont) was developed to reduce the time the patient feels numb by at least 50 percent. A new company, Onpharma, has developed a system to change the pH of the cartridges from acidic to neutral using sodium bicarbonate. Early research shows this reduces the “burn” during delivery and reduces the time of the onset of anesthesia, thus the product being named Onset. Lighting and Magnification The first artificial dental light was probably a candle. In the latter part of the 19th century, dentists used kerosene lamps with focusing devices to direct light into patients’ mouths. After the introduction of electricity, large ball-like ceiling fixtures were used in operatories. In the first decade of the 20th century, the first patient lights that could be focused directly into the mouth were introduced. With the introduction of lights such as the Castle Pano Vision(R) in the 1950s, high illumination was finally realized, permitting the dentist to visualize the oral cavity to a more significant degree. Mouth mirrors were introduced in the 1800s, but it wasn’t until 1950 that front surface mirrors were advocated and later came into widespread use. Now, clear images were possible—without the double image of the glass-covered mirrors formerly in use.7 In the 1950s, miner-type headlamps were used by dentists—often oral surgeons—but by the 1990s, vastly improved small headlamps were available to dentists so that any operative dentist could utilize enhanced intraoral illumination. Today, with the advent of lightemitting diodes (LEDs), these headlights are brighter and lighter, weighing as little as 3 grams. The use of magnification in dentistry was first noted in 1866 by Dr. William Atkinson, who published on the merits of intraoral magnification.23 In 1873, Parsons recommended the use of a large two- to three-inch-diameter magnifying lens with a handle to examine teeth intraorally for gold margins, fissures, and cracks.24 The magnification in use by the 1930s consisted of rather crude devices, and later plastic loupes were clipped onto eyeglass frames or attached to headbands. By the 1980s, high-quality ground-glass optical telescopes were available to the dental profession, allowing for higher magnification with lenses that allow more light in and weigh considerably less than their predecessors. There are also studies that mention a secondary benefit of the use of telescopes in helping operators to maintain improved posture.25,26 Cameras in Dentistry The first intraoral photos could be traced back to 1839, which was the time Louis J. M. Daguerre presented the first process of photography to the world at the Paris Academy of Sciences. Later that same year, New York dental instruments manufacturer Alexander S. Wolcott designed and patented the first camera based on Daguerre’s model. These initial pictures, which were extraordinary copies on silver-coated copper plates, were referred to as daguerreotypes, after Daguerre.27 Dentists began searching for a photographic device to obtain intraoral images, but there was no clear way to get light from the camera’s flash inside the dark cavern that is the mouth. Even with close-up photography, the lens was often inches from the subject. With Lester Dine’s invention of the ring flash in 1952, the dentist had the ability to pinpoint light directly into the patient’s mouth, providing full illumination from external anteriors to posterior intraoral quadrants.28 In addition, a concept called through-the-lens (TTL) flash metering was created. This concept allowed the camera to judge the light around the subject through the lens, and to control the light output based on this. The next issue was that the dentist could not review until the film was devel- Operatory setup, circa 1921 oped. The invention of instant film cam- eras, while not the quality of 35 mm film, offered the user the ability to take a photograph and see results within a matter of minutes. The Polaroid Macro5 had a long run of popularity, as it had five different lenses (intraoral and extraoral) with a set of coordinated mirrors and retractors. Unfortunately, with the demise of instant film, many offices have these now-useless cameras sitting in storage. The first “intraoral cameras” to resemble what we currently use were actually video cameras, but the resolution was far behind that of the 35 mm film images. The video’s integration with computers was cumbersome, often requiring an elaborate video-capturing system and a large cart—and an expense of more than $15,000. The introduction of the first real intraoral camera came in 1987 from Fuji Optical Systems of Los Gatos, California. The camera was released as DentaCam through Patterson Dental Supply. In 1989, Video Dental Concepts also came up with an intraoral dental camera that makes use of a dental endoscopic handpiece. The design was groundbreaking, and it included components from France’s ETS Groux Optical Corp. and the local Panasonic Industrial Camera Division. This was the first component-based intraoral camera with a dental endoscope, a light source, and a remote-head micro camera. It inspired and set the standard for many, many years.27 The digital cameras that we use now combine the best of all three of the previous photographic concepts: the quality of 35 mm film, the speed of instant photography, and the computerized integration of video. The newest digital cameras can connect to a computer network with wires using a universal serial bus (USB) port or wirelessly directly from the cameras, giving extremely high-resolution images as quickly as the intraoral cameras. Of course, the optics in the latter have also been improving to the point of perhaps higher resolution than we actually clinically need. The Future of Dental Technology What will happen in the next 150 years? Current scientists are developing better restorative materials that are more biocompatible and bond more securely to existing tooth structure. Enamel should be able to be rebuilt or reconstructed with genetically engineered replacement tissue. Current restorations will soon be exclusively constructed by computers via computer-aided design and computer-aided manufacturing (CAD/CAM). Laboratories now have less and less plaster and wax than previously. New ceramic materials (including one developed by Dr. Russell Giordano right here at Boston University Henry M. Goldman School of Dental Medicine) are more biocompatible and lifelike than ever before. Implant design has been ongoing for replacement of teeth. However, if we think even further ahead, we should see the eradication of caries using new genetic models and technology. And beyond that, we can look forward to biologically replacing teeth by growing new ones. Recent research in China has been looking at stem cells for just this purpose. This is an exciting time to be in dentistry and health care in general. Conclusion Those of us who have been in practice for more than 40 years have seen the dental technology evolution/revolution firsthand in this last third of the Massachusetts Dental Society’s 150 years. The students currently in dental schools, as well as dental hygiene and dental assisting schools, have grown up in a digital age and often do not realize how lucky they are. Terms such as developer and fixer, mercury dispensers, 35 mm film, and rubber base are a foreign language and things they learn about in dental history books. These students will be the new pioneers, looking to improve and enhance the current products and processes to what was once thought unimaginable. As many of this author’s peers prepare for retirement, there will always be an eye open to hear what fun we will all be missing. ■ References 1. Wikipedia. Pro-Phy-Lac-Tic_Brush_Company. Available from: http://en.wikipedia.org/wiki/Pro-Phy-Lac-Tic_Brush_Company. 2. Bellis M. History of dentistry and dental care. Toothbrush, toothpaste, dental floss & toothpicks. Available from: http://inventors.about.com/od/dstartinventions/a/dentistry_2.htm. 3. Ring ME, Hurley N. James Beall Morrison: the visionary who revolutionized the practice of dentistry. JADA. 2000;131(8):1161-1167. 4. Macleod M. The electric chair. Crime Library. Criminal minds and methods. Available from: http://www.trutv.com/library/crime/notorious_murders/not_guilty/chair/3.html. 5. Ritter Dental Company. The early years 1887– 1919. Available from: http://www.ritterdental.com/Story/TheEarlyYears.htm. 6. DentalEZ Group. Dr Practice by DentalEZ. What changed dentistry? 2011 Feb. Available from: http://www.dentalez.com/blog/itemlist/tag/John%20Naughton. 7. Schulein TM. Significant events in the history of operative dentistry. J Hist Dent. 2005;53(2): 63-72. 8. Ring ME. Behind the dentist’s drill. Amer Heritage’s Invention & Tech. 1995;11(2). Available from: http://50.57.231.74/IT/content/behind-dentist’s-drill-1?page=2. 9. Gardner F. History of dentistry: review of dentistry. Hine M, editor. CV Mosby Company; 1975. 10. Feinberg E. A short history of modern dentistry. Available from: http://www.edwardfeinbergdmd.com/history_of_dentistry.htm. 11. Parker S. Verifiable CPD paper: introduction, history of lasers and laser light production. Br Dent J. 2007;202(1):21-31. 12. UKEssays.com. Dental laser applications. Available from: http://www.ukessays.com/essays/health/dental-laser-applications.php. 13. Summit JB, Robbins JW, Schwartz RS. Fundamentals of operative dentistry: a contemporary approach. 2nd edition. Carol Stream (IL): Quintessence Publishing. 2001. p. 31. 14. M. Javaheri M, Maleki-Kambakhsh S, Etemad- Moghadam SH. Efficacy of two caries detector dyes in the diagnosis of dental caries. J Dent (Tehran). 2010;7(2):71–76. 15. Inspektor Research Systems. Quantitative lightinduced fluorescence. Available from: http://www.inspektor.nl/dental/qlfmain.htm. 16. Standley E, Emmerling H. Dental radiography: technology, infection control, and exposure guidelines. Available from: http://www.rdhmag.com/articles/print/volume-31/issue-1/features/ dental-radiography.html. 17. Ruprecht A. Oral and maxillofacial radiology: then and now. JADA. 2008;139(Suppl 3):5S-6S. 18. Schiff T. Principles of intraoral imaging. INeedCE.com. PennWell Publishing. Available from: http://www.unigrip.com/pdf/Principles%20of%20Intraoral%20imaging.pdf. 19. Singer SR. The history of oral radiology. Part II. 2009 April. Available from: http://c.ymcdn.com/sites/www.aaomr.org/resource/resmgr/mel/ the_history_of_oral_radiolog.pdf. 20. Fidanoski B. Digital radiography. Available from: http://www.fidanoski.ca/dentistry/digital-dental-radiography.htm. 21. Bause GS. How American dentists helped pioneer oxygenation of general anesthetics worldwide. J Hist Dent. 2009;57(3):123-133. 22. Bellis M. History of dentistry and dental care. Fillings, dentist chair, drills, false teeth & Novocain. Available from: http://inventors.about.com/od/dstartinventions/a/dentistry_3.htm. 23. Atkinson WH. Glasses in dental operations. Dent Cosmos. 1866;8(5):456-460. 24 Parsons JH. Periscope. Dent Cosmos. 1873;15(3):153-155. 25. Simonsen RJ. The use of field magnification. Quintessence Int. 1985;16(7):445. 26. Caplan SA. Magnification in dentistry. J Esthet Dent. 1990;2(1):17-21. 27. Favorite Plus. History of the intraoral dental camera. 2013 July. Available from: http://www. favoriteplus.com/blog/history-intraoral-dentalcamera/. 28. Glassgold M. The history of dental photography. Dineonline. Available from http://www.dinecorp.com/?page_id=124.

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