Developments in Dental Technologies – It’s Enough to Make You Smile

Up until recently, despite a massive improvement in the delivery of dental treatment, much of the technology currently used still involves techniques that were first practised by the Romans. The latest developments in digitalisation, computer and laser technologies have and will continue to revolutionise dentistry in ways that dentists could only have dreamed of 20 years ago. This short review looks at some of the latest industry developments and technological advances in the field and highlights the author’s views on the trends which may provide a glimpse of how dental practice will look in 10-15 years time.

Digital X-ray Dentistry: Every Picture Tells a Story

The latest digital X-ray technologies are just one example of how the digital revolution has dramatically boosted the ability of the dental practitioner to make and view accurate x-ray images of the teeth in a fraction of the time taken, using conventional X-ray technologies. In addition to the enhanced resolution and workflow afforded by digital solutions, other major advantages are that the patient has a significantly reduced level of exposure to harmful radiation. Suppliers of digital X-ray equipment such as Schick Technologies Inc, Gendex Dental Systems and Signet S.A.S. advise dentists that there is a reduction in exposure of radiation of up to 90% using the new digital X-ray systems.

Dental practitioners are also able to view images instantly so that both the dentist and patient can clearly see the pictures providing better diagnoses and understanding of the clinical problems. The images can be increased in magnification so that the dentist can zoom in on a single tooth, rotate it, sharpen it and change the colours so that an individual tooth can be customised to match the other teeth.

Another important consideration is that the dental practice does not have to send away to have the conventional X-ray films developed, or, if they used to develop them themselves, they do not have the expense of traditional X-ray film or chemical development. With the advent of Picture Archive and Communication Systems (PACS) any number of copies can be made or stored electronically in the system's database and can be integrated into the practice’s computerised patient record system.

To produce a direct digital x-ray image, three components are necessary: an x-radiation source, a sensor, and a computer. The images are captured using a solid-state detector or sensor such as a charge- coupled device (CCD), a complementary metal oxide semiconductor (CMOS), or a charge induction device (CID). Most direct digital systems use a CCD device. CCD, CMOS, and CID sensors are referred to as "wired" because they are linked by a fibre optic cable to the computer. The sensor itself is basically a silicon chip with an electronic circuit on it. Sensors range in thickness from 3.2 mm to 8.8 mm. Their actual imaging area is smaller than the outside dimensions and is usually smaller than conventional film. The images are displayed instantly on a computer monitor.

Currently there are an estimated 16 intraoral digital x-ray systems available in the US and at least that number marketed throughout Europe. It is clear to HBS Consulting that this market is developing rapidly throughout North America, Europe and Japan and it is anticipated that the market will grow in double digit figures over the foreseeable future.

Dental Laser Systems: At the Cutting Edge of Technology

There has been an explosion of new applications for dental laser systems and with it the market entry of a plethora of new and innovative products supporting the armamentarium of the modern dental practice. Traditionally, lasers have been classified according to the physical construction of the laser (e.g., gas, liquid, solid state, or semiconductor diode), the type of medium which undergoes lasing (e.g., Erbium: Yttrium Aluminium Garnet (Er:YAG)) (Table 1), and the degree of hazard to the skin or eyes following inadvertent exposure.

Table 1: Common Laser Types Used in Dentistry

Table 2: Diagnostic Laser Applications for Clinical Practice

Low power lasers are used routinely for the detection of caries using visible blue light from the argon laser, relying on the lack of fluorescence from carious enamel and dentine to demonstrate the presence of the lesion. Later developments used visible red laser light from a semiconductor diode laser to be used to elicit fluorescence from bacterial deposits, and from calculus. The DIAGNOdent from KaVo Dental GmbH is an example of a 655nm diode laser, used for the early detection of caries by measuring laser fluorescence from within the tooth structure, whilst the Waterlase® from BIOLASE is an example of a YSGG dental laser.

Although the technologies involved in caries detection, resin curing, cavity preparation and soft tissue surgery are highly developed there are major opportunities for the development of laser-based photochemical reactions for various applications. These applications include the targeting of specific cells, pathogens or molecules. In addition it is anticipated that there are other opportunities where there is expected to be a combination of diagnostic and therapeutic laser techniques in the one device, for example the detection and removal of dental caries or dental calculus.

Intra-Oral, Extra-Oral Cameras and Scanners: Seeing is Believing

Intra-oral and extra-oral cameras have allowed dental practitioners to increase their diagnostic capabilities allowing them to visualise each individual tooth providing a previously unseen view. These images can then be stored, and later enlarged and printed. With the images produced by the intraoral camera, patients have an opportunity to see each of their teeth and dentists can indicate problems such as broken teeth, plaque, decay, gum disease, defective fillings, and so on. These pen sized devices are designed to transmit video images to a computing unit where the images are enlarged and transmitted to a television screen. Typically the intraoral and extra oral cameras can be plugged directly into the desk top computer or the laptop through the standard USB interface. Typical examples of intraoral cameras include the SciCan Classic III, the Schick Technologies Inc USBCam®, the Kodak 1000, the SuniCan Portable camera, the Dentron GmbH CaddyCam/DentalScout P2000 and the Aurora - Wireless High Resolution IntraOral Camera

The development of these cameras as well as digital X-rays has been made possible by the development of silicon image sensor technologies and the latest developments of CMOS (complementary metal oxide semiconductor) sensors and amorphous-silicon sensor semiconductor devices. Market intelligence suggests that the proportion of CMOS image sensors in this digital application is expected to continue growing and that CMOS technology has yet to meet its full potential as the CMOS technology supersedes CCD (charge coupled device) technologies.

Several vendors are developing CMOS image sensors, such as Matsushita, Texas Instruments, and NEC. Toshiba is offering a 330,000-pixel, 1/4- in. CMOS sensor for use in digital cameras and Kodak and Motorola have joined forces to produce CMOS image sensors. Photobit Corporation, originally a start up CMOS-sensor manufacturer that had its roots in the NASA Jet Propulsion Laboratory in Pasadena, CA, developed the CMOS Active Pixel Sensor (CMOS-APS). The CMOS-APS technology enables the integration of a complete imaging system, including pixel array and control area, onto a single piece of silicon. Photobit Corporation had been collaborating with Gentex Corporation on the development of CMOS products for use in digital medical imaging products. Micron Technology Inc, acquired Photobit Corporation in 2002 and with it inherited its IP and Image Sensors products and technologies.

CAD/CAM Dental Systems: The Here and Now

CAD/CAM technologies have revolutionised the way laboratories and dentists operate. Pick up any dental industry trade publication or clinical journal and you’ll likely find an article on the use of CAD/CAM technology within the dental industry. There are now a wide variety of different systems currently on the market as illustrated in Table 3, each with their particular proprietary specifications and software packages. The CEREC Series CAD/CAM System from Sirona has emerged as the leading product throughout the world and this is especially so for chair-side restorations. Whilst Sirona is coming under increasing competitive pressure from other major suppliers such as 3M and Nobel Biocare in the chair-side restoration they themselves have been focusing on-exploiting and developing the growing dental laboratory market.

In order to achieve their financial and marketing objectives they have been progressively changing the attitudes of dental practitioners/technicians and patients by emphasising the long-term benefits of CAD/CAM technology – namely, providing stronger, safer and aesthetically pleasing restorations. Clearly there continues to be a huge market potential for dental CAD/CAM systems as more companies seek to gain market share and as new companies enter the market to exploit this rapidly growing industry sector (it is rumoured that Ivoclar Vivadent will be launching a new CAD/CAM system at the 2005 IDS meeting).

Table 3: CAD/CAM Manufacturers and Products

Dental Ceramics Come of Age

A number of amazing advances in the dental ceramics segment have been made over the last decade improving the biocompatibility, durability and aesthetics qualities. The properties of Felspathic porcelain as a veneering porcelain in all-ceramic and metal-ceramic crowns can be modified by altering the basic Potash Feldspar-Quartz-Kaolinite mix. For example, the translucency properties of dental porcelains can be changed by the removal of mullite and free quartz, while increasing sodium oxide and alkaline earth oxides as bivalent glass modifiers. These apparently minor composition changes have made significant improvements to the cosmetic appearance of dental porcelains while retaining the integrity and strength of the restorations. To help match the coefficient of thermal expansion between the dental porcelains and metal alloys used in dental metal-ceramic techniques researchers have altered the Potash Feldspar content.

Leucite has also been widely used as a constituent of dental ceramics to modify the coefficient of thermal expansion. This is most important where the ceramic is to be fused or baked onto metal. The recent introduction of the pressed leucite reinforced ceramic system, in the IPS Empress, for example, has leucite in a different role. This material relies on an increased volume of fine leucite particles to increase flexural strength. Similar versions are now available for metal-ceramic restorations using finely dispersed leucite grains to increase toughness and strength and to modify wear patterns and rates to make them similar to enamel wear rates.

In addition, recent modifications through heat curing after pressing the original aluminous porcelains commonly known as Porcelain Jacket Crowns (PJC), popularised in the mid 1960’s by McLean, have significantly improved its strength. The Nobel Biocare company from Sweden has introduced two systems that essentially use a system of pressing alumina onto a metal die, removing the pressed shape from the die and then sintering it. One system is used to make alumina profiles that are then used as cores to build up ceramic superstructures for single tooth implants, CeraOne®, and the second is to make cores for conventional crowns, a process known as Procera®. Other modifications such as those developed by Vita Zahnfabrik are based on a sintered cast alumina which is then infiltrated with a Lanthana based glass. This modification resulted in a glass infiltrated alumina core (In-Ceram®) on which a felspathic ceramic could be baked to provide the functional form and aesthetic component of the restoration.

Development and production of a glass-ceramic material for dental CAD/CAM-systems

Corning Inc. in the USA originally developed machinable glass-ceramics based on fluormica phases in the early 1970s. Further developments resulted in the creation of Dicor. The Dicor® ceramic uses the lost wax system to produce a glass casting of the restoration. The casting is then heat treated or “cerammed”, during which tetra silicic fluormica crystals are formed to increase the strength and toughness of the glass ceramic. The preheated version of the Dicor® ceramic is the basis from which further developments of glass-ceramic materials for use with dental CAD/CAM systems including modifications such as Macor®. Fraunhofer-Institut für Silicatforschung (ISC) in Germany, were made. These products are now known as Mark II blocks and are produced by Vita Zahnfabrik H. Rauter GmbH & Co. KG, Bad Säckingen, Germany for use with the CEREC 2 by Sirona Dental Systems GmbH, Bensheim, Germany.

The Future Vision for Dentistry: To 2015 and Beyond

So what of the future? Many amongst practitioners, researchers and those from within the dental industry believe that the revolutionary replacement materials of the last century have run their course. From the enormous advances that have recently been made in the biomaterials field, it seems that the time is ripe for another imminent biomaterials revolution within the next decade.

Nanotechnologies

Nanotechnologies such as electrospun polymer nanofibers with diameters ranging from 50 nanometers to 500 nanometers offer the possibility of providing extraordinary strength and structural perfection. More futuristic concepts predict that in the future trillions of preprogrammed, artificially made molecules (nano-molecules) will be injected via a robotic arm into pre-prepared nano-tube sized cylindrical holes in the jawbone of the patient. Man-made molecular signals will then be used to provide precisely programmed trajectories and paths to the trillions of specially-made teeth and bone cells to begin the job of regrowth. Visionists expect that this technology will be used to reconstruct teeth and gum tissue. It is predicted that eventually, even the jaw itself could be reconstructed using nanotechnologies to deposit nanobot diamond-like substructures that fill in and augment disease-deficient and thinning areas of the patient’s jaw. Figure 1 shows what a 'Nanobot' might look like as it repairs blood cells in the body.

Figure 1: Illustration of a Nanobot Like Structure in Red Blood Cells

Stem Cell Biology

Another exciting development has been in the advances made in tissue engineering and the possibilities that stem cell biology could lead to both the repair and replacement of teeth. Professor Paul Sharpe, a pioneer in regenerative dentistry, of the Dental Institute, King’s College, London believes that the stem cells responsible for forming dentin and enamel can be identified and isolated. The stem cells could then be stimulated to grow in a laboratory environment into a sufficiently large number of cells referred to as a tooth bud. The tooth bud would then be inserted into the gum, where it takes resources from the body to grow into a full-sized tooth, stimulating the growth of nerves and blood vessels so it is fully integrated into the gum line.

Another exciting development has been the discovery of dental epithelial stem cells in continuously growing teeth. The niche for the adult stem cells of these teeth is formed at the region of the apical end in tooth development. The region possesses a commonly specialised histological structure for the maintenance of adult stem cells and the production of various progenitor cells producing dental tissues. The molecular signals regulating the maintenance and cell fate decision of adult stem cells, such as Notch1, Lunatic fringe, fibroblast growth factor (FGF)-10, are expressed in the epithelial structure and the surrounding mesenchyme. Based on recent histological and molecular biological research it is suggested that the eternal tooth buds producing various dental progeny are formed at the apical end in the development of continuously growing teeth. It is clear that stem cell biology and implantable tooth buds herald a new and exciting era of research into tissue engineering and solutions to dental caries.

Dental Vaccines

Another recent development which has occurred as a result of recent major advances in molecular biology and genetic engineering is the development of dental vaccines as a method of preventing the bacteria Streptococcus mutans, the main causative agent of dental caries from living in the mouth. Scientists at Boston’s Forsythe Institute, for example, are developing a nasal-spray vaccine that stimulates the body’s immune system to attack the enzyme that allows harmful bacteria to accumulate on the teeth. Elsewhere, scientists are developing vaccines that use toothpaste, mouthwash and even candy to administer antibodies that destroy or neutralise cavity-causing organisms. Scientists have already demonstrated that they can use vaccines to control the bacteria that cause gum disease in animals, and research continues on the development of an effective active immunisation of dental caries with dental caries vaccines containing defined antigens.

These are but a few of the exciting developments which could make a future trip to the dentist a more exciting one rather than the feared, austere image of our childhood memories. We have yet to see the future but it is evident that the industry enters a period of continuing and sustainable prosperity.

Author: Dr. Paul Taylor, Consultant