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The minimal intervention dentistry


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The minimal intervention dentistry

  2. 2. INTRODUCTIONFor almost the whole of the last century, both the teaching and practice ofoperative dentistry have been influenced to a very great extent by Dr. G.VBlack. His contributions to this field are numerous and were supported byextensive studies and meticulous observations based on the scientificknowledge available in his time. His classification of cavities is followed tothis day and most of the principles of cavity preparation taught by him arestill in use. Black‟s principles of cavity preparation were based on the factsabout dental caries known in his time and on the dental materials availableat that time. It was believed that once caries had begun, it would continueto progress until the tooth was lost. The concept of remineralization of earlydental caries was unknown and widespread use of various forms of fluoridefor prevention of dental caries was not as prevalent as it is today.
  3. 3. Also the few materials that were available then were all non-adhisiveand depended upon macro-retention. Therefore most of the cavity outlinesproposed by Black were wide and relied on the concept of extension forprevention that is, extension of the cavity outline into uninvolved pits and fissuresto prevent recurrence of caries in the tooth.This resulted in a “mechanistic” or “surgical” approach to treatment planningrather than a “biologic” or “holistic” or “therapeutic” one. Over the last few decades there has been extensive research in variousfields like cariology, effect of fluorides and other preventive methods in reducingthe incidence of caries and in the cements and composite resins. Also clinicalobservations on the modes and patterns of failure of various, restorativematerials using conventional and conservative methods of cavity preparationhave been carried out.
  4. 4. All this has encouraged researchers and clinicians to question existingconcepts and to adopt more conservative, less destructive methods andapproaches to the treatment of dental caries. This has ushered in an exciting new era in the practice of dentistry wherethe emphasis is on prevention and remineralization of caries whenever possiblerather than blindly following the traditional “drill and fill” approach. Extensive use of fluorides, pit and fissure sealants and diet modificationhave reduced the incidence of caries. When caries is detected early enough it ismonitored and remineralization is encouraged rather than placing restorations.Newer methods of ultraconservative, nonrotary cavity preparation like air abrasionare being introduced. The increasing popularity of adhesion in dentistry hasreduced the need for preparing wide cavities with undercuts and unnecessaryextensions. Also repair of existing restorations. Instead of total replacement isbeing advocated
  5. 5. Diet modificationSince dietary sucrose plays a major role in caries activity, modifying the dietcan be an effective means of preventing dental caries.Diet modification is recommended to patients with active caries and those whoare at high risk for caries development. These patients should be advised toincrease their consumption of foods with anticariogenic properties. Foods with anticariogenic effects Milk. Cheese. Fibrous foods, raw vegetables and grains. Sugar substitutes and artificial sweeteners. Tea.
  6. 6. Anticariogenic foods are those which neutralize the acids produced bybacteria, stimulate saliva and enhance the remineralization process.Milk: Cow‟s milk contains lactose which is the least cariogenic of all monoand disaccharides. It also contains calcium phosphate and casein whichprevent demineralization.Cheese: Cheese contains casein phosphopeptides (CPP) which makes itanticariogenic. So a cube of cheese consumed after a sugery snack reducesdemineralization.Fibrous foods: Raw vegetables and grains have natural protective factorslike organic and inorganic phosphates, polyphenol‟s, phytates and other non-digestible fibe‟s. They also stimulate salivary flow.
  7. 7. Sugar substitutes and artificial sweeteners: Nutritive sugar alcohols likesorbitol, xylitol. And mannitol have an anticariogenic effect. Of these, xylitol hasa specific anticariogenic effect.Xylitol is a recent addition to caries prevention prgrammes. It is a natural fivecarbon sugar that is obtained from birch trees, oats, corn cobs, stawberries andbananas. Patients who are at high risk for dental caries are recommended tochew xylitol gums for 5 to 30 minutes after eating or snacking.
  8. 8. Xylitol gums- mechanisms of action Prevent Streptococcus mutans from binding to sucrose. Increase the concentration of amino acids and ammonia thus neutralizing the plaque acids.Bacteriostatic effect as they are non –fermentable.Increase salivary flow.Enhance remineralization.
  9. 9. Artificial sweeteners like saccharin and aspartame are also non-cariogenicTea: Green, oolong and black teas contain fluorides and pclyphenols or flavionoidswhich suppress bacterial groqth and reduce the acidogenic potential of sucrose. Key dietary recommendations in caries prevention • Reduce the frequency and amount of sugary roods and drinks. Limit these foods to mealtimes. • Recommend diet9s high in proteins instead of sugar rich sweets and sticky foods. • Avoid snacks in between meals. If between meal snacking is unavoidable, recommend foods and drinks with low caries risk or those with anticariogenic effects. • Encourage consumption of foods which enhance mastication, salivary production and oral clearance at each eating session. • Encourage consumption of milk and water instead of sugary acidic soft drinks
  10. 10. Salivary StimulantsSaliva has a very important role in caries prevention due to its antiacterial,buffering and flushing actions. In patients with xerostomia, there is an increasedrisk for dental caries. For these patients, salivary stimulants like gums, paraffinwaxes or salivary substitutes can be prescribed as adjuncts to other preventivemethods. Artificial saliva with added protective agents like mucins are beingclinically tested on patients with xerostomia to check their anticariogenic potential.FlouridesSmall amounts of fluoride can increase the resistance of tooth structure todemineralization. So fluorides are an important component of any cariesprevention program. Fluoride is an essential nutrient for humans and is requiredonly in very small quantities. Natural sources of fluorides in the diet include fishlike salmon and sardines, rock salt, tea leaves, potatoes, jower, and bananas.Minerals water contains 1.5 to 7 parts per million (ppm) of fluoride depending onthe geological source.
  11. 11. The changing paradigms in modern operative dentistry and briefly discusses the various approaches which are being currently proposed.MODERN TRENDS “Minimal intervention dentistry”, “minimally invasive dentistry” or “ “preservative dentistry” is the way dentistry will be practiced in the future. Practice of dentistry based on this philosophy depends upon the following principles:1. Accurate caries diagnosis.2. Classification of the severity of caries using ragiographs .3. Assessment of individual caries risk (as low, moderate or high).4. Disease control.5. Remineralization of early carious lesions.6. Reduction in cariogenic bacteria.7. Minimal surgical intervention of cavitated lesions.8. Repair, rather than replacement of defective restorations.9. Follow up at periodic intervals to assess the outcome of caries management strategies.
  12. 12. To embrace these principles and to integrate them into daily practicerequires a change in the mindset regarding caries. Caries is no longer considered aprocess of irreversible demineralization of tooth structure requiring surgical removalof the pathological tissue and replacement with a suitable restorative material it isnow accepted that caries is a demineralization process where the tooth structurealternately loses and picks up calcium and phosphate lons depending on thesurrounding microenvironment. A drop in the pH below 5.5 can cause subsurfacedemineralization and the presence of fluoride can help in remineralization. With the introduction of technological advances like digital fiberoptictransillumination quantitative laser fluorescence, digital radiography etc, thediagnosis of dental caries is becoming more accurate and follow up morepredictable.
  13. 13. If evidence of demineralization is found radiographically, it is classified asfollows:E0 = Tooth with no caries.E1 = Caries in the outer half of enamel.E2 = Caries in the inner half of enamel.D1 = Caries in the outer third of dentin.D2 = Caries in the middle third of dentin.D3 = Caries in the inner third of dentin. No surgical intervention is needed if subsurface demineralization is foundin enamel or in the outer third of dentin. This is because the rate of progression ofcaries may be slowed down if fluoride therapy is provided or if the patientconsumes fluoridated water. Studies have shown that it can take as long as 6 to 8years for caries to progress through enamel. Therefore, it is important to delayoperative intervention for as long as possible.
  14. 14. XeroradiographyThis technique simulates the photocopying machine. It is a technique in whichthe image is recorded on an aluminium plate coated with a layer of seleniumparticles. These selenium particles are given a uniform electrostatic charge andare stored in a unit called conditioner. When X-rays are passed on to the film, itcauses selective discharge of the particles. This forms the latent image and isconverted to a positive image and is converted to a positive image by a processcalled „development‟ in the processor unit . the main characteristics of xero-radiographic technique are the ability to have both positive and negative printstogether. When positive current is applied to the film, negative are attracted andwhen negative current is applied, positive particles are attracted.
  15. 15. Xeroradiography is twice as sensitive as conventional D-speed films and aphenomenon of „Edge Enhancement‟ is possible with this technique. Edgeenhancement means differentiating areas of different densities especially at themargins or edges. Xeroradiography was considered to be superior as far as caries detectionwas considered, but recent studies have indicated that these are comparable to E-speed films of conventional radiography for diagnosing caries. disadvantages ofthis technique are:• The electric charge over the film, many a times, causes discomfort to thepatient since the oral cavity has a humid environment which acts as a mediumfor flow of current.• Exposure time varies, as manufacturers not indicate the exact thickness of theplate.•The process of development can‟t be delayed and is to be completed within 15minutes.
  16. 16. Although Xeroradiography technique seemed to be promising. Butfeatures of edge enhancement etc. were soon taken over by fast developingdigital imaging systems.Digital imagingWith the advent of computers in dentistry, researchers have even utilizedcomputers for diagnostic purposes also e.g. in digital imaging techniques. A digital image is an image formed and represented by a spatiallydistributed set of discrete sensors and pixels. When viewed from adistance, the image appears continuous, but closer inspection revealsindividual pixels. Digital image in simple means is an image that has beenrecorded with non-film receptors. There are two types of non-film receptorsfor recording digital images.
  17. 17. •The digital image receptor (DIR) which collects the X-rays directly (Direct digitalimaging).•Video camera for forming digital images of a radiograph (Indirect digitalimaging). Digital image receptor works on a charged couple device (CCD), whichis electronically connected, to a computer. CCD is a semiconductor made up ofmetal oxides such as silicon that is coated with x-ray sensitive phosphorous.The CCD is sensitive both to x-rays and visible light. The intraoral DIR is placedin the mouth instead of the x-ray film. The image area is limited by the size ofthe CCD present in the digital image receptor, once the image is captured by theCCD, (like an image of silver halide crystals in an x-ray film) it can be stored inthe computer memory for image processing and can be displayed for viewing.
  18. 18.  Radio – Visio-Graphy (RVG) 19 x 28 mm (Trophy – Japan) Flash Dent 20 x 24 mm (Villa – Italy) Sens-A – Ray 17 x 26 mm (Regam – Sweden) Vixa 18 x 24mm (Gendex – Italy)Advantages1. Darkroom is not required, instant image is viewed.2. The quality of image is consistent.3. Signal to noise ratio is high.4. Greater exposure latitude.5. Elimination of the hazards of film development.6. Radiation dose is decreased.7. Capability for teletransmission.
  19. 19. Disadvantages1.High cost of system2.The life expectancy of CCD is not fixed. Conventional film radiographs may provide insufficient density contrastin the area under suspicion for a carious lesion. Contrast can be enhanced bydigital mode. It has been shown that by digital mode one can enhance densityand contrast upto 70%. It has also been observed that digital method is 50%more sensitive in detecting occlusal caries as compared to conventional films.d) Computer image AnalysisThe variation between observers in the interpretation of radiographs is wellknown. Development of computers in the last few years have made it possibleto use automated procedures which are able to overcome the shortcomings ofhuman eye to quite a great extent. Software have been developed forautomated interpretation of digital radiographs in order to standardize image -
  20. 20. Assessment. These programs are based on the “expert system” which containsfacts about the pathologic conditions. The clinician enters the patient‟s dataand the programme compares the patient‟s data with the basic knowledge ofthe pathology. This programme tells us the possible diagnosis, and even tellsthe possibilities of other ailments. The system can suggest the need foradditional tests to improve the reliability of the diagnostic outcome. Automated analysis provides sensitive and objectiveobservations, which may also permit the detection of small lesions thatotherwise, may not be visible to naked eyes. Various authors have described asystem that is able to recognise features of teeth in intraoral as well asextraoral radiography. Applications have been developed to support theinterpretation of angular periodontal bone defects and to quantity cariouslesions.
  21. 21. Advantages1. Automated analysis may provide sensitive and objective observation of smaller lesions which otherwise are not perceptible to naked eye.2. It is possible to monitor the lesions.3. Quantification of small lesions is possible.Disadvantages1. There is always a need for standardization of exposure geometry.2. Sensitivity is higher but specificity is lesser.3. Time consuming and less economical. It is too early yet to say that the computer-aided diagnosis would replace the routine diagnosis. Much research is needed on this subject.
  22. 22. e) Subtraction Radiography Subtraction radiography is a technique by which structured noise is reduced in order to increase the detectability of changes in the radiographic pattern. The structured noises are the images, which are not of diagnostic value and interfere in routine interpretation of radiographis. Subtraction images can be obtained from photographic, electronic and digital methods. Presently Digital Subtraction Radiography (DSR) is being used and popularized in every field of dentistry. Other methods have the disadvantages such as:i) Inability to produce correct projection geometry.ii) Density and contrast may not be proper. The development of Digital Subtraction Radiography has overcome many of the Limitations of photographic images.
  23. 23. Digitization is achieved by taking a picture of the radiograph using highquality video camera. This is fed to a computer-imaging device, termed as digitizer.Two standardized radiographs produced with identical exposure geometry areused. The first one is the “Reference Image” and the subsequent images are forcomparison. The reference image is displayed on the screen. Then the subsequentimages are superimposed. The difference between the original and the subsequentimages will slow as dark bright areas, which can be interpreted readily. One shouldremember that digitzation does not increase the information available in the originalradiograph. Only turns the image into a form, which can be read by the computer. It has been demonstrated that approximal carious lesions are clearlyvisible by digital subtraction solution (Halse et al 1990)29. Subtraction radiographyhas also been demonstrated to be superior to conventional film radiography fordetecting artificially produced recurrent caries by reducing the false positivediagnosis. It also useful in detecting the progress of re-mineralization and de-mineralization patterns of dentinal caries.
  24. 24. The assessment of alveolar bone height is determining the progression ofperiodontal disease has been one of the major uses of subtraction digitalradiography. It is demonstrated that Digital subtraction radiography is 90 %accuratein detecting as little as 5 % mineral loss of bone compared to the 30-60 % of themineral content of the bone that has to be lost before a radiographic lesion could beseen on a conventional radiograph. The minimal thickness of bone that can bedetected under optimal conditions has been found to be 0.12 mm. For all theseobservations, correct projection geometry is mandatory.II. Electrical resistanceSound tooth enamel is a good electrical insulator due to its high inorganic content.Caries/enamel demineralization results in increased porosity. Saliva fills these poresand forms conductive pathways for electric current. The electric conductivity ishence directly proportional to the amount of demineralisation that has occurred.Electrical resistance is measuring the electrical conductivity through these pores. An instrument called „Van Guard electronic caries detector‟ has beendesigned to measure the electrical conductivity of the tooth. The diagrammaticversion is shown in Fig. 4.9. The electrical conductivity is expressed numerically ona scale from 0-9, indicating a change from sound tooth to an increased degree ofdemineralization. Various studies have confirmed the validity of this test.
  25. 25. Advantages• Very effective in detecting early pit and fissure caries.• It can monitor the progress of caries during caries control programme.Disadvantages• It can only recognise demineralization and not caries specifically. The hypomineralization areas, may be of developmental origin or carious origin will give similar type of readings.• Presence of enamel cracks may lead to false positive diagnosis.• A sharp metal explorer is utilized which is pressed into the fissure causing traumatic defects.• Separate measurements are required for different sites making full mouth examination quite time consuming. A modified form of the instrument „Electronic caries Monitor‟ not onlydetects caries at a single point on tooth but also can screen whole of the occlusalsurface for caries by covering the surface with a conducting medium before placingprobe tip.
  26. 26. III. Fibre Optic Trans IIIumination (FOTI)Fibre Optic Trans IIIumination (FOTI) works under the principle that since acarious lesion has a lowered index of light transmission, an area of cariesappears as a darkened shadow that follows the spread of decay through thedentine. Fibre Optic Trans IIIumination was initially designed for the detection ofproximal caries. (Friedman and Marcus, 1970)25. Fiberoptic consists of a halogen lamp and a rheostat to produce a lightof variable intensity. The 150-watt lamp generates a maximum light intensity of4000 lx at the end of 2 mm diameter cable. Two attachments are used; a planemouth mirror mounted on a steel cuff and a fiberoptic probe of 0.5 mm diameterso that it can be placed in the embrasure region. It produces a narrow beam oflight for transillumination. The reheostat is set to give a light of maximum intensity.For examination, the tip of the probe is placed in the embrasure immediatelybeneath the contact point of the proxmial surface to be examined either on thebuccal or lingual surface depending on the tooth. The marginal ridge is viewedfrom the occlusal surface. A shadow extending to the dentino-enamel junction beneath marginalridge may be evident if there is a break in the integrity of the enamel of marginalridge.
  27. 27. Advantages• No hazards of radiations.• Simple and comfortable for the patients.• Lesions, which cannot be diagnosed radiographically, can be diagnosed by this method.• Not time consuming.Disadvantages• Permanent records are difficult to maintain as can be kept in radiographs.• It is subjected to intra and inter observer variations.• Difficult to locate the probe in certain areas.IV. Laser Auto Fluorescence (LAF)In this, visible light has been used as the light source for the detection of smoothsurface and fissure caries at an early stage (Bejlkagen et al., 1982)8. The tooth isilluminated with a broad beam of blue green light of 488 nm wavelengths from anargon ion laser and the fluorescence observed in the 540 nm range. Thisfluorescence of enamel occuring in the yellow region (540 nm) is observedthrough a yellow high pass filter to exclude the tooth scattered blue light.
  28. 28. Demineralized areas appear dark in this region. Healthy tooth fluoresces differently from that of carious tissue impregnated with fluorescent dyes. Demineralized tissues absorb dyes like Fluorol TGA, Sodium fluorescein etc and fluoresce strongly. This is referred to as dye enhanced lased fluorescence. Recently, a quantified version of laser fluorescence has been developed and tested successfully. In this technique a micro camera is used to capture the real image. A computer screen displays the real images of the teeth under examination.Advantages• It is convenient and a relatively fast method.• Carious lesions can be detected and their mineral loss measure. Natural lesions with a diameter of less than 1mm and a depth of 5-10mm have been detected and measured with this technique.• Preventive measures can be evaluated.• It is suitable for quantifying mineral loss around different restorations.
  29. 29. V. Ultraviolet illuminationUltraviolet light (UV) has been used to increase the optical contrast between thecarious region and the surrounding sound tissue. The natural fluorescence of toothenamel, as seen under UV light illumination is decreased in areas of less mineralcontent such as in carious lesions, artificial demineralization or developmentdefects. The carious lesions appears as a dark spot against a fluorescentbackground.Advantage• It is a more sensitive method than the visualtactile method.Disadvantages• The specificity is a problem between the carious lesions and the development defect.• Still this method has not been developed into a quantitative method.VI. Endoscope/VideoscopeEndoscopic technique is based on observing the fluorescence that occurs whentooth is illuminated with blue light in the wavelength range of 400-500 nm.Difference is seen in the fluorescence of sound enamel and carious enamel. Whenthis fluoresced tooth is viewed through a specific broadband gelatine filter, whitespot lesions appear darker than enamel.
  30. 30. Similarly a white light source can be connected to an endoscope by afiberoptic cable so that the teeth can be viewed without a filter. This technique isreferred to as white light endoscopy. It has been demonstrated in vitro that this technique allows visualization ofsmall carious lesions in the enamel that are difficult to detect with the naked eye orwith radiographs. The clinical detection of small carious lesions would greatlyfacilitate the preventive management of lesions in vivo because „early‟ lesions havethe potential to remineralize and the remineralized lesions are more resistant tosubsequent attack than the adjacent sound enamel. Additionally, a camera can be used to store the image. The integration ofthe camera with the endoscope is called a videoscope. A miniature colour videocamera is mounted in a custom-made metal mirror holder. This is designed in sucha way that the image of the surface of enamel can be viewed by expertindependent examiners who had also examined the teeth visually and byconventional methods.Advantages• It provides a magnified image.• Clinically feasible.
  31. 31. Disadvantages• Requires meticulous drying and isolation of teeth.• Time consuming.• Very costly.VII. Ultrasonic imagingUltrasonic imaging was introduced for detecting early carious lesions in smoothsurfaces. The demineralisation of natural enamel is assessed by ultrasound pulseecho technique. It is observed that there is a definite correlation between themineral content of the body of the lesion and the relative echo amplitudechanges. The ultrasonic probe is used which sends longitudinal waves to thesurface of the tooth and also serves the function of receiving the waves. Initialwhite spot lesions, which extend only upto enamel, produce no or weak surfaceechoes. The sites with visible cavitation produce echoes with substantially higheramplitude. The method, if improved, can be a realistic alternative to radiographicdiagnosis of caries on the approximal surfaces. It is also more sensitive thanvisua-tactile method, however it is not a quantitative method.
  32. 32. VIII. Dye Penetration MethodDyes have a widespread use in dentistry. Dyes can visualise a subject from itsroutine background or if several objects have a similar appearance, colouring by adye may discriminate between them and allow identification. The observation ofthe colouring can be qualitative or quantitative. For a qualitative assessment, it issufficient to observe for colour or differentiate coloured objects from the noncoloured ones.Dyes such as basic fuschin is used.
  33. 33. The focus should be on preservation of enamel and dentin, even in the event ofdemineralizatin as long as cavitation has not occurred. Attempts are made to first control caries progression, assess the caries riskstatus of the individual and monitor evidence of remineralizatin of initial lessions. Ifsuch an attempt which focuses on infection control rather than placement ofrestorations is adopted, it results in at least a 50 % reduction in restorationplacement. After all attemps have been made to shift a patient from the high risk to lowrisk group, only then should surgical intervention be made, that is, cavity preparationand restoration. This is necessary if there is frank cavitation, patientdiscomfort, unacceptable form, function or esthetic
  34. 34. RESTORATIVE OPTIONS Once surgical intervention is deemed necessary three factors determine the future course of action:1. The use of adhesive restorative materials.2. Ultraconservative cavity preparation techniques and outlines.3. Repair instead of replacement of defective old restorations.
  35. 35. 1. Adhesive restorative materialsa. Glass ionomer cements: In the context of minimally invasive dentistry, glassionomer cements possess two desirable properties adhesion to tooth structureand release of fluoride.Glass ionomer cements being water based are relatively brittle materials. Therefore their use is limited to fissure sealing, cevical restorations, proximal cavities in anterior teeth and for restorations in the deciduous dentition. It can also be used as a long term intermediate restoration in extensive cavities to arrest the progress of demineralization.
  36. 36. b. Composite resins: Bonding of composite resins enamel is now in practice ofthe least over three decades and is a well established procedure.Bonding to dentin however was the weak link until Fusayama developed the totaletch concept and Nakabayashi proposed the concept of hybrid layer formation.At present, the effectiveness of a suitable hydrophilic monomer as a primer beforeusing the adhesive has been proved beyond doubt and is a well acceptedprocedure.This has opened up previously unthought of techniques and ultraconservativecavity preparations which will go a long way in preserving the structural integrity ofteeth thereby reducing the need for frequent replacement of old restorations.
  37. 37. 2. Cavity preparationFor patients in a high caries risk group, sealing pits and fissures in recently eruptedteeth which demonstrate a highly convoluted fissure system will greatly reduce riskof developing caries in future. Once cavitations has occurred, surgical intervention is necessary asplaque control becomes impossible. At this point, it becomes important toreconsider standard cavity preparation procedures. As emphasis is being placed on caries preventive methods and the use ofadhesive materials, the approach to cavity preparation should also be conservative.It is necessary to prepare cavities only to gain access to the caries, to removeinfected and degraded enamel and dentin. Slightly undermined enamel may be leftbehind to be supported by the restoration and adjacent uninvolved fissures can besealed without unnecessary widening. Therefore the approach shifts from thepreviously taught “extension for prevention” to “prevention of extension”. Thispreserves as much original tooth structure as possible.
  38. 38. For proximal cavities in posterior teeth, various new approaches are beinginvestigate like “tunnel” preparation; which preserve the marginal ridge above thecarious lesion. If the proximal lesion is close to the marginal ridge, “slot” or“minibox” preparations are being advocated without involving the occlusar surface.
  39. 39. Minimal cavity preparation techniques – The desire for preparing smallerdimension, microcavities has stimulated several minimal preparationtechniques utilizing newer technologies like: Air abrasion Song abrasion. Chemomechanical Lasers.
  40. 40. Air Abrasion: Dental Health Without the DrillAir abrasion is a drill-less technique that is being used by some dentists to remove toothdecay and for other applications.How Does Air Abrasion Work?During air abrasion, an instrument that works like a mini sandblaster is used to sprayaway decay. During air abrasion, a fine stream of particles is aimed at the decayedportion of the tooth. These particles are made of silica, aluminum oxide, or a bakingsoda mixture and are propelled toward the tooth surface by compressed air or a gas thatruns through the dental handpiece. Small particles of decay on the tooth surface areremoved as the stream of particles strikes them. The particles of decay are then"suctioned" away.Is Air Abrasion Safe?Yes, air abrasion is safe. The only precautions needed before air abrasion are protectiveeye wear (to prevent eye irritation from the spray) and the use of a rubber dam (a rubbersheet that fits around teeth) or protective resin applied to nearby teeth and gums toprotect areas of the mouth that arent being treated. The suctioning of particles alsoprevents them from being breathed into the lungs.
  41. 41. What Are the Advantages of Air Abrasion?Compared with the traditional drilling method, the advantages of air abrasion are many andinclude the following:Air abrasion generates no heat, sound, pressure, or vibration.Air abrasion reduces the need for anesthesia, particularly if the cavity is shallow.Air abrasion leaves much more of the healthy tooth tissue behind.Air abrasion leaves the working area relatively dry, which is an advantage during theplacement of composite fillings.Air abrasion reduces the risk of microfracturing and chipping of the tooth, which someexperts believe can lead to premature restorative failures.Air abrasion allows the dentist to treat multiple sites in the mouth during a single visit.The procedure is relatively simple and quick.
  42. 42. What Are the Disadvantages?Air abrasion is not necessarily totally painless. The air can cause sensitivity and socan the abrasives used.Air abrasion is not recommended for deep cavities (those close to the tooths pulp). Itis best suited for removing small cavities that form early on the surface of teeth.Only composite filling material can be used following air abrasion because it adhereswell to the smooth surface created by the air abrasion (amalgam or silver fillingsrequire drill-based cuts to prevent the filling from falling out).Who Are the Best Candidates for Air Abrasion Procedures?Air abrasion is ideal for use in children and others who are fearful and have minimaldecay.What Other Types of Procedures Are Performed With Air Abrasion?Air abrasion can also be used to:Remove some old composite restorations, but not metallic restorations such as silveramalgam fillingsPrepare a tooth surface for bonding or sealantsRemove superficial stains and tooth discolorations
  43. 43. 3. Repair of defective restorations. An embrrassingly high percentage of restorations require eventualreplacement. Invariably the outline of the next restoration is more extensive. Thissets off a “restorative cycle” where larger and larger restorations are placed till thetooth requires endodontic treatment or extractions. This approach should be discouraged and repair rather than replacement ofold restorations. Should be take up. This, however, is not well accepted by theprofession as it is considered “patchwork” dentistry and a departure from traditionalteaching. In the interest of long-term preservation however,repair of defectiverestorations should be taken up as long as it does not compromise of the new andold parts of the restoration.
  44. 44. As this approach is fairly new it is still difficult to lay down definite guidelinesregarding which restorations can be safely repaired and which requirereplacement. When repair of an existing restoration is being considered thepatient‟s risk for caries, professional judgement regarding the risk versusbenefits and conservative principle should be taken into account
  45. 45. .CONCLUSION Minimal intervention techniques cause less tooth destruction thanconventional techniques, thus increasing the long-term survival of teeth. Thisapproach is intended to diagnose dental defects, mainly caries, early so that thetreatment options can combine a preventive philosophy, remineralization of earlylesions and minimal intervention for the materials, scientific background andtechnology for the adoption o this approach are with us today and it is uptopractitioners and leachers to translate these concepts into everyday clinical use.