A REVIEW ON OZONE THERAPY IN TREATMENT OF DENTAL CARIES Ozone therapy for the treatment of dental caries ABSTRACT: Dental caries is a bacterially mediated disease characterized by demineralization of the tooth surface, which may lead to cavitation, discomfort, pain and eventual tooth loss. Ozone is toxic to certain bacteria in vitro and it has been suggested that delivering ozone into a carious lesion might reduce the number of cariogenic bacteria. This possibly could arrest the progress of the lesion and may, in the presence of fluoride, perhaps allow re-mineralization to occur. This may in turn delay or prevent the need for traditional dental conservation by 'drilling and filling'. OBJECTIVES: To assess whether ozone is effective in arresting or reversing the progression of dental caries. INTRODUCTION: • Dental caries is a bacterial disease that can affect persons of all ages. • Traditional non-operative treatment of caries can consist of mechanical or chemical removal of plaque, home dental care, treatment with fluoride from toothpaste or other fluoride-containing substances, fissure sealing and dietary guidance. • Traditional operative treatment of caries consists of the removal of the demineralised dental tissue with a drill and subsequent replacement of the missing dental tissue. • Ozone therapy is a new method for the treatment of caries that is marketed as a treatment that acts by destroying the cariogenic bacteria. • Ozone therapy has been investigated in a few trials that do not fully meet the criteria that must be met before a treatment can be called evidencebased. There is therefore a fundamental need for more evidence before it is possible to determine whether ozone therapy can be included in the repertoire of dental care methods. • Future studies of ozone therapy should clarify the extent to which the treatment can replace non-operative and/or operative procedures, and the effect of this should be assessed through long-term studies. • In view of the relatively limited knowledge available about the effect of ozone therapy, including uncertainty as to whether the treatment can replace operative and/or non-operative procedures, it is not possible to determine whether ozone therapy is more cost-effective than traditional caries treatment. DENTAL CARIES:- Dental caries is the most common cause of toothache and if left untreated can lead to loss of the tooth The disease can affect children and adults of all ages. Studies show that caries affects both halves of the jaw symmetrically, but that not all teeth and tooth surfaces are equally vulnerable to caries. Over the past 30-40 years the incidence of caries in the population of the industrialized world has declined considerably as a result of prevention and treatment based on new research on the etiology and progression of the disease. Fluoride, especially from toothpaste, has played an important role. Caries can develop when the following factors are present concomitantly: a tooth, bacteria and substrate, including fermentable sugar for these bacteria. Certain bacteria form acid when they take up sugar, and the minerals in the tooth gradually dissolve when its environment becomes acidic (pH below approx. 5.5) Plaque (visible bacterial deposits) and fermentable sugar are necessary for the development of caries, but are not sufficient alone . Further essential requirements are that conditions on the surface of the tooth remain undisturbed (for example: through lack of brushing) and time. Popularly speaking, these factors comprise the »attack mechanism«. Other factors only affect the rate of progression of the caries. These factors, which are called determinants, include the occurrence of fluoride in the saliva, the saliva secretion rate and buffering capacity, and the diet and frequency of food intake. The diet can increase the demineralisation rate, while the other determinants have an inhibitory effect and are considered to be »defence mechanisms«. In general, the risk of caries is also affected by social status and health attitudes. Present methods for prevention and treatment of caries:- The treatment of caries depends on how advanced the disease is on the individual teeth. The depth of the cavity relative to the nerve is the parameter most often used to subdivide caries in stages. The following three stages are used: superficial, median and deep (close to the tooth’s nerve). Treatment is traditionally subdivided into non-operative and operative treatment. The most important non-operative treatments are mechanical or chemical removal of plaque, home dental care (tooth brushing and cleaning with floss or tooth picks) and dietary guidance (restrictive use of carbohydrates), treatment with fluoride from toothpaste or other fluoride-containing substances such as fluoride chewing gum or fluoride gel, and fissure sealing. It has been shown quite clearly that fluoride reduces caries. Fissure sealing is a treatment whereby fissures in the surface of the tooth are sealed with a resin-based fissure sealant to prevent the acid produced by the bacteria from dissolving the minerals in the tooth. This is particularly used in children and young people as the chewing surfaces of the rearmost molars can very rapidly develop the median and deep stages of caries. The non-operative treatments are used with the early stages of caries. Operative treatments are used in the median and deep stages of caries. The carious tissue is removed with a drill, and the cavity is filled. If the nerve and blood vessels of the tooth have been damaged, root treatment can be performed. No drug treatment is presently able to eradicate the harmful bacteria - in this case cariogenic bacteria - without concomitantly eradicating the protective bacteria. The caries bacteria belong to the normal bacterial flora in the oral cavity and are important for our health in general. New method for treating caries:- Within the past few years, ozone therapy has been launched as a new method for treating caries. Ozone (O3) is a gas with a characteristic, penetrating odour that is present in small amounts in atmospheric air. Ozone is an extremely strong oxidant that oxidises nearly all metals to the highest oxidation stage. Ozone reacts with numerous inorganic and organic compounds. It bleaches dyes and kills bacteria. Among other things, ozone is used to purify drinking water and water in dental equipment and for sterilising instruments for medical use. For many years, ozone has been used to treat infections (O3 bagging). Ozone destroys the bacterial cell membrane, where after the bacteria die [11]. As bacteria cause caries, it was natural to investigate whether ozone could be used to treat caries. HealOzone® is a CE-labelled apparatus for clinical ozone therapy of caries. HealOzone, which has been developed by Curozone Inc., Canada and is distributed by KaVo Dental Ltd., converts oxygen to ozone. The ozone is thereafter led to a hand piece fitted with a silicone cup. Differently shaped silicone cups are available that correspond to the form of various teeth and their surfaces. This ensures close contact between the silicone cup and the carious area of the tooth so that the ozone does not escape. The ozone is led through the silicone cup over the tooth for a minimum of 10 seconds. The ozone in the silicone cup is collected again and reconverted to oxygen by the apparatus. Ozone treatment of the caries lesion is completed after 2-3 minutes. Thereafter a solution containing 2% sodium fluoride and 5% xylitol is applied to promote healing (re-mineralization) of the caries lesion. HealOzone has only been tested by a small number of dentists in Denmark. In other EU countries such as Germany and England, HealOzone is already in use in many private dental Practices. Evidence:- Ozone has been used to treat established carious lesions of various stages, but has not been used for prevention. A number of studies have investigated the effect of ozone on caries. A recent Cochrane Review identified 3 randomized controlled trials (RCTs) and a further 42 conference papers, abstracts and posters, etc. (from an unknown number of studies). Only the three RCTs were included; the remaining articles were excluded for reasons such as a lack of blinding, randomization or controls, less than six months follow-up or a lack of investigation of extracted teeth. Two of the three RCTs included in the analysis investigated the effect of ozone therapy on crown lesions, while the third investigated the effect on root lesions. The Cochrane Review concluded that these trials provide no evidence that the application of ozone arrests or reverses the decay process. A further two studies concerning the effect of ozone therapy on carious root lesions have been published. One of these studies demonstrated a significant reduction in the number of bacteria in ozone-treated lesions compared with placebo-treated lesions immediately after the treatment. The study showed that 20 sec of ozone therapy resulted in harder dentine in 81% of the ozone-treated teeth, while 10 sec of ozone therapy resulted in harder dentine in just 22% of the ozone-treated teeth. This indicates that the number of bacteria in carious root lesions is considerably reduced by ozone therapy, and that the lesions clinically change to stages in which progression of the caries can be considered to have ceased. The objective of the other trial was to assess the effect of ozone therapy in combination with the daily use of re-mineralizing products. The control period was up to 18 months, and the patients were recalled for examination and repeat treatment after 3, 6, 12 and 18 months. The trial showed that 69- 100% of the ozone-treated lesions (duration of treatment 40 sec) became harder during the 18-month trial and none became softer. In the placebo group only 1% of the caries lesions became harder, while 4-37% became softer (worsening). The regained hardness of the dental tissue could indicate that caries can be arrested. The change could also be partly attributable to the uptake of minerals from the saliva, the daily influence of re-mineralization products or the effect of the solution applied after the ozone treatment, but this is uncertain. It is also unclear to what extent the caries had been removed by the subjects themselves through tooth brushing between examinations. Neither of the studies determined the degree of caries prior to initiation of treatment (baseline). Whether the ozone-treated lesions re-mineralize is not sufficiently clarified. Neither is it clear whether one or two ozone treatments are sufficient to arrest future progression of the lesion, although the preliminary results seem to indicate that ozone treatment should be repeated at regular intervals. In these studies the patients did not report any adverse side effects of the treatments [15,16]. Ozone therapy is a non-operative treatment and should also be compared with other non-operative treatments for controlling caries. In the two abovementioned trials the ozone therapy was used to treat root caries, which is normally treated both non-operatively and operatively depending on to what extent and how rapidly the patient develops caries, the stage of progression and the location of the caries lesion on the tooth. Lesions that are difficult to access such as those between two teeth will not be amenable to ozone treatment, as the silicone cup cannot penetrate into the gap. Thus ozone therapy of caries is only suitable for easily accessible surfaces where the caries can also be removed with a toothbrush or other non-operative procedures. Goals of ozone therapy:- Setting the standard-of-care and therapeutic goals are based on sound evidence-based science is critical. Therapeutic goals are inclusiveand not exclusive of standard of care. The goals of oxygen/ozone therapy are5: Elimination of pathogens. Restoration of proper oxygen metabolism. Induction of a friendly ecologic environment. Increased circulation. Immune activation. Simulation of the humoral anti-oxidant system. Systems for generating ozone gas in dentistry:- Ultraviolet system: Produces low concentrations of ozone, used in aesthetics and for air purification. Cold plasma system: used in air and water purification. Corona discharge system: produces high concentrations of ozone. It is the most common system used in the medical/ dental field. It is easy to handle and it has a controlled ozone production rate. Forms of application:- · As an infusion into infected jaw bone (cavitation). · As an infusion into the temporomandibular joint for the treatment of pain and inflammation. · As an irrigant during new root canal therapy to disinfect the involved tooth. · Adjunctive therapy with the use of Ozonated Olive Oil for periodontal disease. INDICATIONS:- In dentistry, ozone has got its role in various dental treatment modalities. Ozone therapy presents great advantages when used as a support for conventional treatments.1,7 Prophylaxis and prevention of dental caries. Remineralisation of pit and fissure, root and smooth surface caries. Restoration of open cavitations along with conventional conservative measures. Bleaching of discoloured root canal treated teeth. Endodontic treatment. Desensitization of extremely sensitive tooth necks. Soft tissue pathoses. The treatment of infected, badly healing wounds and inflammatory process. OZONE THERAPY IN PROSTHODONTICS:- Microbial plaque accumulating on the dentures is composed of several oral microorganisms, mainly C. albicans. Denture plaque control is essential for the prevention of denture stomatitis. In an attempt to solve this problem Arita et al. assessed the effect of ozonated water in combination with ultrasonication on C. albicans. Following exposure to flowing ozonated water (2 or 4 mg/l) for one minute they found no viable C. albicanssuggesting the application of ozonated water might be useful in reducing the number of C.albicanson denture bases.17 OZONE THERAPY IN SURGERY:- The influence of ozonized water on the epithelial wound healing process in the oral cavity was observed by Filippi. It was found that ozonized water applied on the daily basis can accelerate the healing rate in oral mucosa. This effect can be seen in the first two postoperative days. The comparison with wounds without treatment shows that daily treatment with ozonized water accelerates the physiological healing rate.18 Patients treated with ozone got healed more quickly without the need for systemic medication when compared to the control group. This finding suggested ozonated oil might be effective in the treatment of alveolitis.19 Application of ozone therapy after tooth extraction and in case of post-extraction complications, was found quite useful.20 OZONE THERAPY IN ENDODONTICS:- Current research has been focused on determining guidelines for ozone use. The principle line of study has evolved using the ozone to determine its effect on several kinds of caries (pit and fissure,21 noncavity22, and primary root caries21,23,24,25). The oxidative impact on this microbiota has been recognized in several studies; however, there is a divergence of opinion regarding the amount of time that ozone gas should be applied. One study suggests application of ozone gas for a period of 10 to 20 seconds resulted in 99% of the microorganisms being destroyed 24,25. Another report states 40 seconds of application was insufficient to decontaminate the area and failed to act on underlying infected dentin26. Interesting data shows ozone does not affect the sealing ability of the bonding-system. Ozone therapy was also used in prevention of dental caries in fissures of the first permanent molars in children.20 An interesting data shows ozone does not affect the sealing ability of the bonding-system 27. Polymicrobial infections complicate cases of apical periodontitis. As a result, current research is focused on finding treatment solutions with a high antimicrobial effect while minimizing injury to the periapical tissues. The oxidative power of ozone characterizes it as an efficient antimicrobial and its indication for use in endodontic therapy seems quite appropriate. Its antimicrobial action has been demonstrated against bacterial strains such as: Mycobacteria, Staphylococcus, Streptococcus, Pseudomonas, Enterococcus and E. coli 31,32 S. aureus33, E. faecalis 34,35 and C. albicans17 using in vitro research models. The ozone showed effectiveness over most of the bacteria found in cases of pulp necrosis, but not when the bacteria are organized in biofilm20 in vitro studies. Bleaching:- In root canal treated teeth, crown discolouration is a major aesthetic problem, especially in anterior teeth. Conventional walking bleaching requires much more time and results are not often satisfactory. Also, capping the tooth with ceramic crown is not always a good idea. But, now ozone has the answer to all these questions. After placing the bleaching agent into the inner of the tooth, the crown is irradiated with ozone for minimum of 3-4 minutes. This ozone treatment bleaches the tooth within minutes and gives the patient a happy and healthier-looking smile. Desensitization of Sensitive Root Necks:- Quick and prompt relief from root sensitivity has been documented after ozone spray for 60 seconds followed by mineral wash onto the exposed dentine in a repetitive manner. This desensitization of dentine lasts for longer period of time. Smear layer present over the exposed root surface prevents the penetration of ionic Calcium and Fluorine deep into the dentinal tubules. Ozone removes this smear layer, opens up the dentinal tubules, broadens their diameter and then Calcium and Fluoride ions flow into the tubules easily, deeply and effectively to plug the dentinal tubules, preventing the fluid exchange through these tubules. Thus, ozone can effectively terminate the root sensitivity problem within seconds and also lasts longer than those by conventional methods. OZONE THERAPY IN PERIODONTICS:- Dental biofilm makes it difficult for antibiotics in targeting putative periodontal pathogens. Higher concentrations of antibiotics are required to kill these organisms which are inevitably associated with toxic adverse effect on the host microbial flora. The application of ozone therapy in periodontics showed promising results. Both gaseous and aqueous ozone are used as a substitute to mechanical debridement. Ozonated water (4mg/l) strongly inhibited the formation of dental plaque and reduced the number of sub gingival pathogens both gram positive and gram negative organisms. Gram negative bacteria, such as P. endodontalis and P. gingivalis were substantially more sensitive to ozonated water than gram positive oral streptococci and C. albicans in pure culture. Furthermore ozonated water had strong bactericidal activity against bacteria in plaque biofilm. In addition, ozonated water inhibited the accumulation of experimental dental plaque in vitro. Aqueous ozone was found to be more biocompatible than gaseous ozone. It resulted in toxic effect on human oral epithelial and fibroblast cells compared to antiseptics such as chlorehexidine digluconate, sodium hypochlorite and hydrogen peroxide during a 1-minute time period.28,29 Ozone gas found to be toxic to the human oral epithelial and gingival fibroblast cells and aqueous ozone was more biocompatible than gaseous ozone.30 The application of ozone therapy in chronic gingival and periodontal diseases, showed subjective and objective improvement of their status, as well as patients with periodontal abscess, with no exudation was observed.20 OZONE THERAPY IN STOMATOLOGY:- Sechi et. al evaluated the effect of ozonized sunflower oil on different bacterial species isolated from different sites. Ozone proved to be effective against all bacteria when tested, while mycobacteria were shown to be the most susceptible to the oil.31 Macedo and Cardoso described a case report of the application of ozonated oil on herpes labialis and mandibular osteomyelitis and demonstrated faster healing times than conventional protocols.36 Ozone Toxicity:- Ozone inhalation can be toxic to the pulmonary system and other organs. Complications caused by ozone therapy are infrequent at 0.0007 per application. Known side-effects are epiphora, upper respiratory irritation, rhinitis, cough, headache, occasional nausea, vomiting, shortness of breath, blood vessel swelling, poor circulation, heart problems and at a times stroke.4Because of ozone's high oxidative power, all materials that come in contact with the gas must be ozone resistant, such as glass, silicon, and Teflon. However, in the event of ozone intoxication the patient must be placed in the supine position, and treated with vitamin E and n-acetylcysteine.2 CONTRADICATIONS:- The following are contraindications for the use of ozone therapy: Pregnancy. Glucose-6-phosphate-dehydrogenase deficiency (favism). Hyperthyroidism. Severe anaemia. Severe myasthenia. Acute alcohol intoxication. Recent myocardial infarction. Haemorrhage from any organ. Ozone allergy. Ongoing studies:- The School of Dentistry, University of Copenhagen, is currently conducting a randomized trial of the efficacy of ozone therapy in preventing caries, and whether the effect lasts for a long time. The results can be expected in 2-3 years. Among other things, the trial will investigate whether the effect is attributable to the ozone treatment per se, the solutions applied after treatment or to a combination of both . IMPLEMENTATION:- At the present time, evidence for the efficacy of the treatment is lacking. There is a need to document an effect over and above that provided by ordinary tooth brushing before it is possible to determine whether ozone therapy can be included in the repertoire of dental care methods. If an effect of ozone therapy on dental caries can be demonstrated it might be possible to use the method in dental care as a supplement to home dental care and professional tooth cleaning/ brushing. There is no evidence that ozone therapy offers any advantage compared with current preventative measures such as regular tooth brushing, rinsing with fluoride or fissure sealing. ADVANTAGE & RESEARCH HISTORY:- The use of ozone in dental practice takes dental care into the 21st Century. It sets the standard of a modern pharmaceutical method to treat dental and medical patients;  The prior few years have seen publication of a number of articles assessing Ozone therapy. The ability of ozone to kill micro-organisms associated with non-cavitated occlusal caries was investigated by A Baysan and D Beighton of the King’s College, London Dental Institute, London, Uk. Their paper was published in 2007 in the journal Caries Research (Caries Res, 2007; 41:337-341). The authors report that treatment of the lesions in freshly extracted molar teeth with 40 seconds of ozone failed to significantly reduce the numbers of viable bacteria in the infected dentine beneath the demineralized enamel. In 2008, JE Dähnhardt and colleagues from the School of Dental Medicine, Bern, Switzerland, assessed the ability of ozone to manage hypersensitive teeth. What was found was that immediately after 40 seconds of ozone treatment there was a reduction in the pain level of treated teeth by approximately 55 percent. However there was also a significant reduction in pain within the control teeth as well so that comparing test and control teeth over time (54 weeks) did not reveal a significant difference in pain reduction (Am J Dent. 2008; 21(2):74-76). Also in 2008 GM Knight, et al, from the University of Adelaide, South Australia used an in vitro model to assess the effect of ozone application to dentine on biofilms formation and to measure bacterial viability. Their study was published in the Australian Dental Journal (Aust Dent J. 2008; 53(4):349-353). For this in-vitro study, dentinal discs were cemented onto the bases of screw top vials and then infused with ozone for 40 seconds. An equivalent number without ozone treatment served as controls. Then nutrient material and streptococcus mutans and lactobacillus acidophilus was allowed to grow out for four weeks. Optical density and scanning electron microscopy and SEM analysis was used to identify the resulting colonization. What was found was that Ozone infusion appeared to prevent biofilm formation, in contrast to the control specimens which had substantial growth. The optical density was almost twice that of the ozone infused dentine. It was concluded that in this preliminary study that the infusion of ozone appeared to prevent biofilms formation from S mutans and L acidophilus. Another in-vitro study by E Johansson and colleagues from the Umea University Department of Odontology, Sweden published in 2009 demonstrated elimination of S. mutans, L. casei, and A. naeslundii with 60 seconds of Ozone treatment (J Dent. 2009; 37(6)449-53). Three other recent in-vitro studies suggest that ozone delivered for 60 seconds may be able to provide an antibacterial effect against S. mutans but in one of the studies L casei was more resistant to destruction (O Polydorou, et al, The antibacterial effect of gas ozone after 2 months of in vitro evaluation; Clin Oral Investig, 2011; feb – ahead of print)( E Johansson, et al.  Antibacterial effect of ozone on cariogenic bacterial species. J Dent., 2009; 37(6):449-453). Other evidence suggests that the dosage level is inversely associated with subsequent bacterial viability (Castillo A., et al, In vitro reduction of mutans streptococci by means of ozone gas application. Quintessence Int., 2008; 39(10):827-831). To summarize the newest research, the literature appears to be without reported randomized controlled in-vivo longitudinal trials assessing the use of Ozone infusion on caries development or control. With the exception of the pain study cited above, the only recent published research has involved only in-vitro assessment of the potential bactericidal properties of the treatment. Studies from Europe (Abu-Salem et al, 2003; Baysan and Lynch 2001; Holmes, 2003; Holmes and Lynch, 2003) have shown conclusively that the use of ozone in dental care is effective as a non-destructive method to manage decay and its destructive effects. The use of ozone has been shown to be the ideal way to manage anxiety of patients young and old - and their carers (Dahnhardt et al, 2003; Domingo et al, 2004). The effects of ozone reduce tooth destruction in routine preparation (Clifford, 2004; Holmes, 2004; Holmes and Lynch, 2004) and ozone reduces the time and the cost of dental care (Domingo and Holmes, 2004; Johnson et al, 2003) and raises the practice income. In Endodontics, ozone is effective against Enterococcus faecalis (Chang et al, 2003). Professor Velio Bocci from Milan University (1994) has emphasised that the potential toxicity of O3 should not preclude its employment for medical, dental & veterinary purposes. This statement has been echoed by thousands of health professionals who use ozone in clinical practices around the world, and millions of patients that have been treated. The correct operation of the Ozi-cure meets all current Health and Safety Regulations in all countries. The Ozi-cure is completely safe when used according to the Ozi-cure Operating Instructions. Ozone is perceived to be a dangerous gas; let's put this into a scientific context. In 1978 an FDA Report showed that 1.5 million people were hospitalised by pharmaceutical reactions, and there were 140,000 deaths from prescription drug usage. In stark contrast, a 1980 German Medical Society Report for Ozone Therapy cited 5.6 million ozone treatments carried out for that year. Of the 5.6 million ozone treatments, there were just 40 reported cases of side effects (0.000007%), and 4 deaths from inappropriate administration of ozone gas. Ozone remains the safest and effective pharmaceutical treatment. In World War I, ozone was used to treat wounds, burns and infections. The modern development of ozone's application to Medicine began in the 1950s in Europe, Australia, Israel, Cuba, Brazil and Columbia. Today, over 9000 doctors, dentists & vets worldwide now routinely use ozone in their clinical management. Since 1998 researchers, lead by Professor Edward Lynch from Queen's Dental Hospital and Belfast University, Ireland, have opened a radically and revolutionary way forward. The dental profession no longer has to destroy tooth tissue to eliminate bacteria. A simple 60 second (average treatment time) treatment with a device that delivers a burst of ozone will destroy all the bacteria that caused the infection and the decay. It destroys all the organic effluents that are produced by these bacteria; this is shown in Fig 1 opposite. The top data shows the spread of organic bio-molecules produced by an active carious lesion. The lower data shows the effect of 10 seconds of ozone; the profile now consists of a single main spike of acetate acid, and the other oxidation by-product is carbon dioxide. This H MNR research proved that ozone worked as a pharmaceutical approach to caries in-vitro. By effectively sterilising the lesion, minerals from the patients own saliva will re-enter the areas of mineral loss to harden them. Once hardened, it is more resistant to future bacterial attack and mineral loss. Research in Cuba, Europe, the USA and South Africa concerning the anti-microbial efficacy of ozone has continued over the last twenty years and has conclusively shown the ability of both gaseous and dissolved ozone to eradicate a wide range of bacteria, bacterial spores and viruses (Baysan and Lynch, 2001; Ishizaki, 1986; Katzeneleson, 1974; Vaughan, 1987; Whistler and Sheldon, 1989). A clinical guide for the use of ozone in dental and medical practice is included with every Ozi-cure device sold. CONCLUSION:- Dentistry is changing as we are now using modern science to practice dentistry. The ozone therapy has been more beneficial than present conventional therapeutic modalities.Every Monday morning, dental practices over the world power up for a week's worth of drilling and filling, tooth removal, and reconstruction work. Queues of fearful patients, tearful children being comforted by anxious parents, people in considerable pain, line up outside the doors to their dental surgeries. Once inside, these patients are subjected to the traditional smells of oil of cloves, disinfectants, and the noises of the high pitch whine of the dental drill; the odd scream or two filters through the hushed, usually silent waiting room into the street outside. It is a sad fact of life that every dentist is trained that if there is an area of decay in your tooth, the only way to treat this is to drill the decay out or amputate it, and then place a filling that will have to be replaced at some stage.   For a small minority of patients, where their dental practices have chosen to invest in a new technology, the opposite happens almost every day. The queue is one of bright, cheerful adults and children; there are few smells to associate this practice with the traditional one down the road. The noise of the drill is seldom heard, and happy smiling faces emerge from the treatment room.