TECHNIQUES OF CARIES REMOVAL
• INTRODUCTION • CLASSIFICATION OF TECHNIQUES • OTHER TECHNIQUES • HAND PIECE • ENDOSTEPPER, SMART PREP BURS, FLUORESCENCE • HAND EXCAVATION • AIR ABRASION • AIR POLISHING • ULTRASONIC INSTRUMENTATION • SONO ABRASION • CHEMOMECHANICAL CARIES REMOVAL • LASERS • CONCLUSION
TECHNIQUES OF CARIES REMOVAL
INTRODUCTION: Caries removal or rather treatment of the infected dentine, is best defined by outcome criteria, i.e., procedures that lead to local arrestment of the carious process. Traditionally it includes the removal of all soft dentine, but a number of treatment principles can be employed in order to arrest the disease locally. The techniques used in carious dentine removal have developed since GV Black, in 1893, initially proposed the principle of “extension for prevention� in the operative treatment of carious lesions. He proposed that the removal of sound tooth structure and anatomical form at sites that might otherwise encourage plaque stagnation would help minimize caries and its progression. This was based on the knowledge of the disease process and restorative materials available at that time. Later, with the advent of adhesive restorative materials, newer techniques for removal of carious dentine have been developed in an attempt to minimize this excessive tissue loss. There are a number of techniques available for cutting tooth tissue. A classification of these techniques according to Banerjee, Watson and Kidd: Category
Technique
Mechanical, rotary
Handpiece + burs
Mechanical, Non-rotary
Hand excavators, air abrasion, air polishing, ultrasonics, sono-abrasion
Chemo-mechanical
Caridex, carisolv, enzymes
Photo-ablation
Lasers 2
Other than the techniques mentioned in the above classification, there are other techniques also, which include, 1) Controlled selective rotary excavation a. Torque controlled motors i. Endostepper ii. Carisolv power drive b. Polymer burs i. Smart prep burs c. Fluorescence aided caries excavation
Handpiece and Bur: A carious lesion is usually penetrated and extended using ultra high speed rotary instruments. Penetration through the carious enamel pit and fissure is accomplished with a click No.1 or No.2 round bur. After exposing the lesion, removal of the carious dentine progresses from the lateral borders of the lesion to its center using round steel excavating burs in a low speed contra-angled hand piece. As firm dentine is reached laterally, it is followed to the central area by removal of the carious dentine. A sharp round steel bur as large as is suitable for the size of the lesion is indicated. A positive rake angle would produce a more acute angle on the edge of the blade (edge angle). Burs with positive rake angles may be used to cut softer, weaker substances, such as soft carious dentin. If a blade with a positive rake angle is used to cut a hard material such as sound enamel or dentin, it would dig in leaving an irregularly cut surface and the cutting edges of the blade would chip and dull rapidly. 3
The steel bur has a greater number of flutes than does the carbide bur. Hence, a smoother cutting action is achieved by using this bur and the operator is provided with a better tactile cue. Discrimination between carious and normal dentin must be made and a light force is applied to the bur using a wiping motion. When the removal of the carious lesion has been accomplished using the tactile and visual cues, clinical judgment of the caries removal can be made using caries detecting dyes. Although, this method is quite efficient for caries removal, it is still aversive for patients, over preparation of tissues is possible and negative effects on the pulp could also result. Controlled selective rotary excavation: a) Torque controlled motors: i) Endostepper: It is that where the computer controlled engine makes possible a digital attitude to the number of revolutions and torque for each individual instrument. This system offers a patent twisting function – it is especially helpful while using files in the root canal, where the file can free itself by an adjustable left right movements. It causes less vibrations, that the patient hardly feels the treatment. b) Polymer burs: Smart prep bur: It is a round bur made of a polymer that is only hard enough to remove decayed dentin, stopping at the hard healthy dentin and making for a very conservative preparation.
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As these burs are made of a material that is harder than decay yet softer than healthy dentin, when the bur contacts healthy tissue, it becomes self-limiting. These burs are available in 3 sizes #2, #4, #6, which seem much smaller than their carbide round bur counterparts. They should be used at low speed i.e. 500-800 rpm as suggested by the manufacturer, and without water spray. They should be used with very light air brush type stroke. Old restorations, enamel or sound dentin is removed using burs at high speed followed by smart prep burs at low speed to remove only the decayed dentin. As soon as the bur hits anything not as soft as decayed dentin such as healthy dentin, affected dentin, enamel or a restoration the flutes just totally smossh together and render the bur completely useless. But there have been also some false positives as well with this bur. Although the bur had flaked, but upon checking the cavity with a spoon excavator, there was some decay left. c) Fluorescence aided caries excavation: Generally, carious regions can easily be overlooked and deciding whether excavation is complete or not is often difficult. Changes in tooth fluorescence have been used to detect early tooth surface caries for some time and is found to be one of the reliable method. Lennon et al. in 2002 studied the residual caries detection using visible fluorescence. Although oral microorganisms themselves are not known to fluoresce, several oral microorganisms were reported to produce orange-red fluorophores as byproducts of their metabolism. For this reason, orange-red
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fluorescence in dental hard tissues may be a good marker for the zone of bacterial invasion in dentine. The rationale for the use of visible orange red fluorescence for this purpose is that carious dental tissue fluorescences more intensely in the red portion of the visible spectrum (>540 nm) than the sound dentine. In this technique, generally a violet light (370-420 nm) will be generated using a 35 watt xenon discharge lamp and a blue band pass filter with peak transmission at 370 nm are used. This light will be fed into the fibre-optic slow speed hand piece so that it is focused onto the operating field during excavation. The operator can observe the cavity through a 530 nm – high pass filter. Under such observation, the areas exhibiting orange-red fluorescence indicate the presence of caries which can be removed by subsequent use of an appropriate size bur. Lennon in 2003, conducted a study on fluorescence aided caries excavation compared to conventional method and concluded that this method is more effective than conventional caries excavation. Mechanical Non-rotary: a) Hand excavators: Manual excavation of dental caries is done by using spoon excavator. They are frequently used in conjunction with rotary instruments or can also be used with other hand instruments such as enamel hatchet. The walls of the cavity should first be extended using either rotary instruments or enamel hatchet so that the margins of the carious area may be seen and readily approached. The extent of the lesion should determine the size of the spoon excavator to be used. The largest excavator
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that will conveniently fit the area is selected. Sharp excavators are effective and will reduce the force required for caries removal. The sharpened edge of the instrument should be carefully introduced under the most accessible margin of the carious area and gently but quickly forced under it avoiding as far as possible pressure in the direction o the pulp. An effort should be made to lift out the entire mass with one stroke, following as nearly as possible the hard underlying dentin. Failing in this, a second or third sweep of the instrument from a different direction should completely remove it. Following this, any remaining softened matter should be gently scraped out with the same instruments and the cavity should be cleaned. Advantages: 1. Long term observations have shown adequate tissue removal 2. Over excavation is unlikely 3. Accepted procedure especially in pedodontics and anxious patient 4. Does not require any expensive equipment Disadvantages: 1. High pressure causes pain Banerjee, Kidd and Watson in 2000 studied the efficiency (time taken) and effectiveness (quantity of dentine removal) by bur, air-abrasion, sono-abrasion and carisolv gel compared to conventional hand excavation. From the results, it was concluded that bur excavation was quickest but overprepared cavities relative to the autofluorescence test, whereas carisolv excavation was slowest but removed adequate quantities of tissue. Sono-abrasion tended to underprepare whereas air7
abrasion was more comparable to hand excavation in both the time and amount of dentine removed. They concluded conventional hand excavation appeared to offer the best combination of efficiency and effectiveness for carious dentine excavation within the parameters used in this study. b) Air-abrasion or kinetic cavity preparation: Dr. Robert B. Black was the first to study air-abrasives technology in dentistry in 1943. In 1945, he published a series of articles on the use of air-abrasive technique for cavity preparation and oral prophylaxis. In 1951, S.S.White introduced the first air-abrasive system – Airdent. Air abrasion is not a complete replacement for the dental hand piece with burs, it is merely an adjunct. Its use is limited to areas that can be easily seen and kept free from moisture. Desired cavity details can be obtained when the technique is augmented with hand instruments. The principle employed by the airdent unit utilizes kinetic energy or inertia as a rapid and not unpleasant means of removing tooth structure by incorporating a fine abrasive material in a high velocity gaseous propellent. Air abrasion is not a completely painless method of cavity preparation; however it eliminate the objectionable features of vibration, bone-conducted noise, pressure and heat. The traumatic influence on tooth structure and periodontal tissue is reduced to a minimum.
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Bur
Air abrasive
Vibration
No vibration
Bone-conducted noise
No bone conducted noise
Temperature rises
Just 1 or 2°F
Pressure – 2 pounds
10 – 14 gm
In cases where the tooth is hypersensitive, pulpal stimulation may be experienced in various degrees. Such stimulation may be controlled by reducing the pressure of the propellant or by reducing the amount of abrasive mixed with the propellant or both. AIR ABRASIVE SYSTEM: It consists of a unit, foot control and hand piece. Hand piece consists of a handle, a shaft – an adjustable contra-angle (ball and socket) and a tip or nozzle in a 90° relationship to the shaft. Basic principles of air-abrasive: Air abrasive depends for its action on a fine stream of suitable gas carrying a controlled quantity of small abrasive particles. Abrasive Materials: Al2O3 – For cutting tooth substance CaMgCO3 – Dolomite – oral prophylaxis Studies (1950), have shown a potential of inhalational problems by airabrasive particles. At present, the air-abrasive technique has US FDA approval for clinical use of 27.5 µ alumina particles which has very little health hazard, both to the patient 9
and the dentist. It possess a hardness of 9 on Moh’s scale and its particles possess sharp edges and pointed corners when properly prepared. Other materials: Polycarbonate resin Alumina – hydroxyapetite Propellants: Although compressed air may be used as a propellant, CO2 was found to possess certain advantage for this purpose. It is, Practically free from moisture Non-toxic in low concentrations Convenient and almost universally available The pressure of the liquid CO2 varies from 700 to 1300 pounds per square inch. This pressure is reduced to approximately 115 pounds in the line and further reduced within the range of approximately 80 to 45 pounds at the nozzle. Character of the abrasive stream: The abrasives escapes from the nozzle in a cone-shaped stream, the walls of which diverge from its long axis at an angle of approximately 3 ½ degrees. The particles of abrasive in the stream travel at speeds in excess of 1000 feet per second, which is well into the realm of supersonics. In order to use the air abrasive system properly, the operator should first understand the relation which exists between the distance at which the nozzle tip is
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held from the tooth surface and the angulation of the nozzle with respect to the proposed cavity. It is noted that with a nozzle tip distance of 1mm the angulation is zero. At 2 mm total angulation 0.45 it is 7°. At 5mm it is 13°. At 10 mm it is 23° and at 15mm it is 35°. Peruchi et al. in 2002 evaluated the cutting patterns produced by air abrasion system with an 80° nozzle angle, 50 µ abrasive particle size and 80 psi air pressure. The effects of 0.38 or 0.48 mm inner tip diameter at 2 or 5 mm from tip to the tooth surface and 15 or 30 sec of application time on cutting efficiency were evaluated. Statistical analysis revealed that the width of the cuts was significantly greater when the tip distance was increased. Significantly deeper cavities were produced by a tip with a 0.48 mm inner diameter. The application time did not influence the cuts. They concluded that precise removal of enamel is best accomplished when a tip with a 0.38 mm inner diameter is used at a 2mm distance. Cutting Speed: There are certain influencing factors which affect the cutting speed, they include the nature of the instrument – bur or diamond point it diameter, speed in rpm and pressure applied. Conversely the action of air abrasive is influenced by factors such as propellant pressure, type and particle size of the abrasive used, abrasive mixture, nozzle bore and length, nozzle distance from the enamel surface and nozzle angulation. 11
Studies have shown that an ordinary no.561 chrome plated dental bur is capable of removing approximately 6mg of enamel in 30 sec at 1725 rpm when applied with the pressure of 2 pounds. Whereas using aluminium oxide with a propellant pressure of 80 pounds per square inch, a nozzle of 0.018 inch inside diameter and nozzle tip distance of 7 to 13 mm with an angle of 90째, air abrasive is capable of removing 30 mg of enamel in 30 seconds. The type and size of abrasive will affect the coarseness of the abraded surface. The larger the size and harder the particles, the greater is the transferred kinetic energy to the surface and thus the rougher the final finish. Primary considerations relative to the use of air-abrasive hand piece: Hand piece Control: The operator must develop close co-ordination between the eye, hand and foot. Because there is no tactile relation between the instrument and tooth being operated on, the operator must rely solely on his visual sense. Thus, good eye sight and good lighting are imperative for this technique. Hand piece grasp: Unlike the rotary hand piece, an air abrasive hand piece is always held lightly in the pen grasp in as much as the reaction force resulting from the abrasive stream which is only 10 to 14 gm. In accomplishing the cutting action, the instrument is merely pointed. No pushing or pulling is ever necessary and the 3 rd or 4th finger is generally used not as a brace but as a rest for steadying the instrument.
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Nozzle angulation: Nozzle angulation must be correlated with nozzle tip distance. Generally speaking, the greater the nozzle tip distance the greater will be the angulation. Peruchi et al. in 2001 evaluated the effect of nozzle angle and the tip diameter on the cutting efficiency of an air abrasion system. They worked with prep star microabrasion machine using a hand piece with either 80° or 40° nozzle angles with 0.38 or 0.48 mm tip inner diameter. The parameters which were held constant were abrasive particle size – 27 µ, air pressure – 80 psi, distance – 2mm and duration – 15 sec. Statistical analysis revealed that the width of the cuts was significantly greater when the cavities were prepared using the 45° nozzle angle. Significantly deeper cavities were produced with the 80° nozzle angle. The nozzle diameter influenced the cutting efficiency in softer substrates, dentin and cementum. They concluded that precise removal of hard tissue is best accomplished using the 80° angle nozzle tips for all types of surfaces, enamel, dentin and cementum. Basic types of cuts: Regardless of the type, size or location of the cavity being prepared, the principles involved for the establishment of cavity walls and floor do not vary. There are two basic types of cuts using air abrasive hand piece. 1. Straight line cut 2. Angle cut
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1. Straight line cut: It is employed where high degree of definition is desired. This type of cut utilizes close nozzle distances and is precise and narrow. 2. Angle cut: The angle cut employs the use of greater nozzle distance, together with the required nozzle angulation. As the nozzle distance from the substance being cut increases, the angle of the walls increases proportionately. The advantages afforded by the employment of the angle cut are – a) greater cutting speed and b) less visual interference. Although there are advantages of using air-abrasion system, there are certain limitations. 1. The nozzle of the air-abrasive instrument does not come into actual contact with the tooth, providing no tactile guidance. 2. In case of secondary caries, it is difficult to remove the existing restoration. 3. High cost 4. When the abrasive particles strikes the surface of the mirror, it becomes frosted. 5. Might damage the cavosurface sound tooth enamel. Goto and Zhang in 1996, conducted a study to establish a protective method for cavo surface sound tooth enamel during air abrasive cavity preparation using protective varnish. Varnish was applied to the tooth surface in single, double and triple coats. Class V cavities were then prepared on the border area of varnish coated and intact tooth surface. The varnish was then washed off and the enamel
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margins were observed through SEM. They found that tooth surface enamel which was coated with varnish appeared intact and the cavo-surface margin remained at a right angle, whereas, the tooth surface enamel without varnish coating appeared rough and the cavo-surface margin exhibited a round shape. Waveren and Andersen in 2000 studied the quantification of surface enamel loss and a comparison of shear bone strength. Enamel loss was determined for 2 enamel conditioning methods: acid etching with 37% phosphoric acid and sand blasting with 50 ¾ aluminium oxide. The results showed that the enamel loss associated with sand blasting is equal to or smaller than that resulting from acid etching. The results also showed that the bond strength of the sandblasted groups was significantly lower than that of the etching groups. This indicates that sandblasting is not an alternative for the acid-etching technique currently used. Arzu and Osman in 2004, studied the effect of air-borne particle abrasion on the shear bond strength of four restorative materials to enamel and dentin. The control group specimens were treated with silicon carbide paper. Restorative materials tested were composite, compomer, GIC (L) and GIC. They concluded that the use of air-borne particle abrasion increased the shear bond strength of restorative materials tested to enamel and dentin. c) Air-polishing: It is the process by which water-soluble particles of sodium bicarbonate and tricalcium phosphate (0.08% by weight) – to improve the flow characteristics are applied onto the tooth surface using air pressure, shrouded in a concentric water jet. This is the important difference between this technique and that of air-
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abrasion. As the abrasive is water soluble it does not escape too far from the operating field. The bombardment of the hard tooth surfaces by these particles results in a continuous mechanical abrasive action which removes surface deposits. Razoog and Koka in 1994, noted that increasing the air-pressure beyond 90 psi actually reduced the abrasiveness of the microprophy system. This was due to a phenomenon found in one-dimensional, two phase fluid dynamics – choked flow. In this phenomenon, as the air pressure exceeds the critical pressure, the mass flow of particles will reduce thus limiting the system’s abrasiveness. The commercially recommended use of this technique is to remove surface enamel stains, plaque and calculus well away from the gingival margins of healthy teeth. However, overzealous use could easily remove a considerable amount of healthy tooth structure especially at the cervical margin. It has also been suggested that air-polishing could be used for the removal of carious dentine at the end of cavity preparation. Bester et al. in 1995 studied the effect of air polishing on the dentin smear layer and dentin. The purpose of this study was to determine the most effective period by which the smear layer can be removed by air-abrasive polishing without totally exposing the dentinal tubules and the effect air polishing has on dentin at different experimental application periods with regard to the appearance of the dentinal tubules (open or obliterated) and the amount of tissue loss from the dentinal surface. SEM observation showed smear layer removal as an immediate effect of air polishing. Application times of longer than 5 sec showed obstruction of dentinal tubule opening, possibly a result of abrasive powder residue. 16
Therefore, they concluded that air polishing removes the smear layer and the amount of dentine removed corresponded to the time of application. d) Ultrasonic instrumentation: Nielson et al. in 1950s, indicated the possibility of using an ultrasonic instrument to cut tooth tissue. He designed a Magnetostrictive instrument with a 25 kHz oscillating frequency. This is used in conjunction with a thick aluminium oxide and water slurry, created by the cutting action, the mechanism of which was the kinetic energy of water molecules being transferred to the tooth surface via the abrasive through the high speed oscillations of the cutting tip. It was found that the harder the tissue, the easier it was to cut. Soft, carious dentine apparently could not be removed, but the harder, deeper layer was more susceptible. There are many parameters that could potentially be adjusted to alter the cutting characteristics and Nielsen attempted to analyse the results from altering the pressure applied, the length of use of the instrument, the powder water ratio in the slurry, the nature of the material cut and the type of abrasive used. However, due to the erratic and unpredictable performance of this instrument, his results were inconclusive. Even though this method was developed only to a preliminary stage, it was used on forty patients in a clinical trial where they found the technique to be favorable in terms of the reduced vibration and sound generated when compared with the dental drill.
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e) Sono-abrasion: Further development from the original ultrasonics is the high frequency, sonic, air scalers with modified abrasive tips – a technique known as Sonoabrasion. The Sonicys micro unit designed by Drs Hugo is based upon the sonic flex 2000 L and 2000 N air-scaler hand pieces that oscillate in the sonic region (<6.5 kHz). The tip describe an elliptical motion with a transverse distance of between 0.08 0 0.15 mm and a longitudinal movement of between 0.55 – 0.135mm. These tips are diamond coated on one side using 40 µ grit diamond and are cooled using water irrigant at a flow rate of between 20-30 ml/min. The operational air pressure for cavity finishing should be around 3.5 bar. There are currently three different instrument tips: a lengthways halved torpedo shape (9.5 mm long, 1.3 mm wide), a small hemisphere (1.5 mm diameter) and a large hemisphere (2.2 mm diameter). The torque applied to the instrument tips should be in the region of 2N. If the applied pressure is too great, the cutting efficiency is reduced due to damping of the oscillations. This technique was initially developed, using different shaped tips, to help prepare pre-determined cavity outlines (Sonicys) but also works well in removing hard tissue when finishing cavity preparation. Yozici et al. in 2002 conducted an SEM study on different caries removal techniques on human dentine. The carious tissue was removed by hand excavation, bur excavation, air-abrasion, Laser ablation, chemomechanical removal and sono-abrasion. Surfaces treated by hand excavation, bur excavation and air abrasion were covered with a residual smear layer. Sono-abrasion with patent dentinal tubule completely removed the smear layer. A few patent orifices 18
of dentinal tubules were observed in dentin subjected to laser ablation and chemomechanical caries removal. Advantage of this caries removal technique is less over preparation than with rotary instruments and smaller access cavity is possible. Whereas the disadvantage being unclear completeness of excavation. f) Chemomechanical Caries Removal: Dentine consists of Mineral (70% wt), water (10% wt), organic matrix (20% wt). Of this organic matrix, 18% collagen and 2% non-collagenous substances
including
chondroitin
sulphate,
other
proteoglycans
and
phosphophoryns. Collagen is an unusual protein which contains large amounts of proline and one third of the amino acid content is glycine. The polypeptide chains are coiled into triple helices which are known as tropocollagen units; these tropocollagen units then orient side by side to form a fibril. Covalent bonds between the polypeptide chains and between the tropocollagen units from cross links and give the collagen fibrils stability, in dentine the fibrils are in the form of a dense mesh work which becomes mineralized. When caries occurs, acids produced by plaque bacteria by anaerobic fermentation of carbohydrate initially cause solubilization of mineral in enamel. As the process progresses, dentinal tubules provide access for penetrating acids and subsequent invasion by bacteria which results in a decrease in pH and causes further acid attack and demineralization. When the organic matrix has been demineralised, the collagen and other matrix components are then susceptible to enzymatic degradation, mainly by bacterial proteases and other hydrolyases with
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respect to collagen degradation, two zones can usually be distinguished within a lesion. There is an inner layer which is partially demineralised and can be remineralised and in which the collagen fibrils are still intact, and there is an outer layer where the collagen fibrils are partially degraded and cannot be remineralised. A CMCR reagent must be able to cause further degradation of this partially degraded collagen, by cleavage of the polypeptide chains in the triple helix or hydrolyzing the cross linkages. It involves the application of a solution that selectively softens the carious dentine, thus facilitating its removal. This limits the removal of sound tooth structure, the cutting of open dentinal tubules, pulpal irritation and pain compared with conventional mechanical methods. The principal of chemomechanical caries removal is based on the studies done by Goldman and Kronman in 1970s. They studied the effect of NaOCl (nonspecific proteolytic agent) on the removal of carious material from Dentine. They found that NaOCl was too corrosive for use on healthy tissues, therefore incorporated it into Sorensenâ&#x20AC;&#x2122;s buffer (which contains glycine NaCl and NaOH. Later it was found that chlorination of glycine to form N-Monochloroglycine was more effective in caries removal and was available as GK-1019. In subsequent studies, they found that the system was more effective if glycine was replaced by amino butyric acid, which was N-monochloro DL-2 aminobutyric acid â&#x20AC;&#x201C; available as GK-101E. The mechanism of action of these substances on collagen was unclear. Originally, it was thought that the procedure involved chlorination of the partially degraded collagen in the carious lesion and the coversion of hydroxyproline to 20
Pyrrole-2-carboxylic acid. Further studies suggest that cleavage by oxidation of glycine residues could be involved. This causes disruption of the collagen fibrils which become more friable and can then be removed. This system (GK-101E) was patented in the US in 1975 and received FDA approval for use in USA in 1985 and was then marketed as caridex. It consisted of two solutions:Solution I â&#x20AC;&#x201C; 1% Na OCl Solution II â&#x20AC;&#x201C; Glycine, Aminobutyric acid, NaCl and NaOH The pH of this solution was 11. A delivery system was also available with this which consisted of a reservoir for the solution, a heater and a pump which passed the liquid, warmed to body temperature through a tube to a hand piece and an applicator tips of various sizes and shapes. The solution was applied to the carious lesion by means of an applicator, which was then used to loosen the carious dentine by a gentle scrapping action; the debris together with the spent solution being removed by aspiration. Application was continued until the dentine remaining was deemed sound by normal clinical tactile criteria. It was found that with suitable accessible soft lesions, after 5-10 min treatment only clinically sound dentine remained. After the removal of carious dentine, the surface would appear to be the interface between carious and sound dentine, such surface has shown to have better adhesion with materials such as GIC, than with the conventional smear layer. 21
This system avoids the painful removal of sound dentine but is ineffective in the removal of hard eburnated parts of the lesion (may not be necessary). Rotary or hand instruments may sometimes be needed for the removal of tissue or material other than degraded dentin collagen-access to small or interproximal carious lesion, removal of enamel overlying the caries, removal of existing restorations as well as for cavity design when non-adhesive restorative materials are used. This system requires large volumes of solution – 200-500ml. Because of the time required for chemomechanical caries removal, large volumes of solution needed and the fact that the delivery system was no longer commercially available, use of chemomechanical caries removal, despite its potential, became minimal. Further research was carried out on chemomechanical caries removal and a new product was introduced by Medi Team in Sweden in 1998, which they marketed as carisolv. It is in the form of a pink gel which can be applied to the carious lesion with specially designed hand instruments or the recently introduced carisolv power drive. Carisolv gel is available in two different packages:a) Carisolv gel – Multimix b) Carisolv gel – Single mix The first marketed version of carisolv is a multimix system. 2 syringes – Syringe I: 0.5% NaOCl Syringe II:
Amino acids – Lysine, Leucine and glucamic acid Carboxymethyl cellulose
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Erythrocin NaCl and NaOH After the components of both the syringes are mixed, it is active for only 20 min. In recent years, the gel has been further developed at Sweden. To improve its efficacy, an increase of the amount of free chloramines was needed, which in turn required a higher concentration of NaOCl. One effect of the higher concentration of NaOCl is that the colour agent has been removed i.e., the gel is uncoloured. The mode of action is the same for both versions of the gel. Single Mix: One syringe contains material sufficient for 10-15 cases. This dispenses the exact amount required through a disposable mixing tip and it can be active for up to 1 month if stored in a refrigerator even after opening. The gel is applied to the carious lesion with one of the hand instruments and after 30 sec, carious dentine can be gently scraped. More gel is then applied and the procedure is repeated until no more carious dentin remains, a guide to this being, when the gel is removed from the tooth it is clear. Time required for caries removal using carisolv is 9 â&#x20AC;&#x201C; 12 min (5-15 min) and the volume required is 0.2 â&#x20AC;&#x201C; 1.0 ml. Advantages of Carisolv over Caridex: 1. Gel-consistency, there is better contact with the carious lesion and the quantity required is very less, enhances precision placement. 2. 3 amino acids are incorporated instead of one and the different charges have improved the interaction with the degraded collagen within the lesion, thus increasing the efficiency. 23
Case Selection: For the first few cases, it is advisable to select fully visible and easily accessible lesions such as buccal or occlusal caries, with 1-2 mm of opening, thus allowing the procedure to be observed. Instruments: Specially designed instruments are available which consists of 4 different handles with 8 interchangeable tips ranging in diameter from 0.3 to 2mm. They may have a feel or look of excavators, but they are designed to be used in a rapid whisking or curetting fashion, thereby limiting the removal of tooth structure to carious tissue only. The instrument also help to guide the operator around the cavity, tactile sensation helps differentiation between carious and non-carious dentine. 1) Multistar, star 3 – Basic instrument to apply gel and start removing caries. The multistar tip promotes penetration of the gel. When getting close to healthy dentine, use the star-shaped tip, scraping in all directions with its 4 pronged design. 2) Star 2, star 1, point – To remove caries in smaller cavities for example root caries or deciduous teeth. 3) Flat 1, flat 0 – Used to remove caries at the DEJ. 4) Flat 3, Flat 2 – To be used for example, close to the pulp and to remove the softened carious dentine from the cavity. 5) Extra bend star 3, flat 0 extra bend – Primarily used for crown margins and areas that are difficult to access.
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Carisolv power drive is a faster and easier way of working with carisolv. Advantages:1. It has unique torque limitations and this helps to protect the healthy dentine. 2. It works at very low speed, thereby minimizing noise and pain. 3. It has the ability to power drive to switch very smoothly between more powerful and more cautious caries removal. Power drive is used with special star bur â&#x20AC;&#x201C; 1.0, 1.5, 2.0. These burs work with power drive or a low speed handpiece of maximum 300 rpm. Mixing â&#x20AC;&#x201C; For a single mix system, it can be applied directly. If it is a multimix system, then it should be mixed immediately before use, as the effectiveness of this will decrease in 20-30 min. The unmixed gel should be stored in the refrigerator, but allowed to come to room temperature before use. The lids of both the syringes are removed and the syringes are secured together using the male and female connecting parts. The plungers are then pressed alternately to mix and activate the gel. Once the gel has uniform colour, it maybe dispensed directly into a container such as a dapen dish. It is then placed in the carious lesion for 30 sec, then rapid light pressure is applied with the instruments to facilitate removal of caries, the gel must be continuously applied until cavity preparation is complete. As the caries is removed, the gel becomes clouded with debris and it may be useful to flush the cavity intermittently for inspection. It is advised to use warm water, but cold water dispensed from the 3 way syringe does not appear to cause any significant discomfort to the patients.
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Cavity Assessment: Surface colour, structure and hardness Caries indicators can also be used. The gel no longer becomes cloudy once caries removal is complete. The sound dentine after caries removal has a slightly frosted and irregular appearance compared with the smooth shiny appearance achieved following conventional preparation. Reason â&#x20AC;&#x201C; following conventional cavity preparation, the smooth glossy appearance is that of the smear layer which is spread out across the underlying dentine. By contrast the chemomechanically treated surface lacks a smear layer, leaving the underlying dentine relatively rough surface of the dentine exposed, which has a characteristic matt finish. Advantages: 1. Only demineralised dentine containing denatured collagen is affected. 2. The gel is applied at room temperature, which reduces the risk of pain sometimes associated with the cool liquids that are used with other caries removal procedures. 3. The characteristics of the instruments assure ultimate tissue preservation. Enzymes: Studies have examined the possibility that carious dentine might be able to be removed by using certain enzymes.
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In 1989, Goldberg and Keil successfully removed soft carious dentine using bacterial Achromobacter collagenase, which did not affect the sound layers of dentine beneath the lesion. In 1996 Norbo, Brown and Jan had used the enzyme Pronase, a non-specific proteolytic enzyme originating from Streptomyces griseus, to help remove carious dentine. This might have significant clinical implications but further laboratory research is required for validation of this technique. Laser: Lasers are devices that produce beams of coherent high intensity light. It is an acronym for light amplification by stimulated emission of radiation. In 1960, Theodore Maiman developed the first working laser device which emitted a deep red-coloured beam from a ruby crystal and was postulated that it could be applied to cutting both hard and soft tissues in the mouth. However, further research found that the ruby laser produced significant heat that caused damage to the dental pulp. Laser devices use different physical media and sources to generate a variety of wavelengths that interact with specific molecular components in thermal tissues. Each of these wavelengths targets specific tissue components such as melanin, hemosiderin or haemoglobin, extrinsic tattoo materials, water and other materials. Lasers have been shown to effectively cut and ablate hard and soft tissues when the appropriate wavelength is selected. Absorption Characteristics: In 1983, Nagasawaâ&#x20AC;&#x2122;s light transmission data from dental hard substances has shown that selective ablation of caries based on natural absorption differences 27
would not be possible with lasers emitting in the infrared spectrum. Using a light source emitting wavelengths between 1 Âľ and 12.5, he demonstrated that absorption in healthy dentine is higher than absorption in carious dentine. Because that finding is the opposite of the authorâ&#x20AC;&#x2122;s goal, a measurement of the absorption of carious and healthy enamel and dentin by the UV and visible light spectrum was undertaken. The optical density of healthy and carious dentine and enamel was measured which had shown that in the wavelength range of 240 to 770 nm, carious lesion demonstrates a stronger absorption than healthy dentin and enamel. It was then shown that in the spectral range of 320 to 520 nm, the optical density and absorption of carious dentine is four times higher than for healthy dentine. Ablation: The ablation thresholds for carious and healthy dentine were determined using lasers emitting in the blue spectral range where the absorption differences between carious and healthy were the highest and it was found that selective ablation of caries is possible when applied energies are at least 0.4J/cm 2 but below 1.8J/cm2. Using that energy, caries should be removed and sound dentine is unaffected. The laser energy must be delivered uniformly to the lesion surface. Murray et al. stated that the remaining dentine thickness should be at least 0.5 mm to avoid evidence of pulp injury. Laser interaction with biocalcified tissues has been studied and it was found that CO2 lasers and Nd: YAG lasers produce surface changes in enamel such as roughness, creating, cracking, fissuring, melting and recrystallisation. In addition, some studies have demonstrated that these lasers can generate markedly elevated
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surface and pulpal temperature. The profound thermal effects and inability to precisely cut biocalcified tissues have eliminated the initial CO2 and Nd: YAG laser systems from consideration as modalities for dental surgery. The ArF excimer lasers have been reported to remove dental caries; the ability to effectively cut sound enamel and dentine, however has not proven to be efficacious. Krypton F excimer laser has been shown to cut dentin; however enamel is resistant to effective ablation. In vitro studies have shown that CO2 laser irradiation inhibits the progression of caries like lesion up to 85%. Subsequent studies have shown similar effects for Er : YAG and Er, Cr : YSGG with a 40% and 60% caries reduction respectively. Er : YAG lasers, ER : YSGG and Er, Cr : YSGG lasers operate at wavelengths of 2940, 2790 and 2780 nm. These wavelengths correspond to the peak absorption range of water in the infra red spectrum. Since all three lasers rely on water-based absorption for cutting enamel and dentine, the efficiency of ablation is greatest for the Er : YAG laser. These laser systems can be used for effective caries removal and cavity preparation without significant thermal effects, collateral damage to tooth structure or patient discomfort. A characteristic feature of Er-based laser systems is a popping sound when the laser is operating on dental hard tissues which varies according to the presence or absence of caries. In contrast to the popping sound during caries removal, one current generation Er, Cr : YSGG laser system creates a loud snapping sound even when not in contact with any structure in the mouth.
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A laser powered hydrokinetic system which has been said to work on the mechanism of Er, Cr : YSGG which delivers photons into an air-water spray matrix with resultant microexplosive forces on water droplets. This process is hypothesized to contribute significantly to the mechanism of hard tissue cutting. The laser powered hydrokinetic system with its accompanying air water spray has been shown to cut enamel, dentine, cementum and bone efficiently and clearly without any deleterious thermal effects on dental pulp. Abrasion: An important theoretical extension to the principal of water-based laser ablation of tooth structure is recently described effect of laser abrasion in which ER : YAG laser energy is used to accelerate the movement of particles of Sapphire 30-50 Âľ in diameter in aqueous suspension. As in air-abrasion, these particles causes brittle splitting, resulting in the substance removal. In the laser abrasionmethod, speed photography has documented particle velocity in the range of 50100 mts/sec which enables a rate of enamel removal higher than that of high air turbines with a very low volume of abrasive particles. This technique could be employed with current generation lasers once a suitable system with the suspension of particles has been developed.
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CONCLUSION: Various techniques for caries removal are available but the main problem at present is the apparent lack of the self-limiting nature of the individual methods. All the techniques will remove carious dentine with differing levels of efficiency but more importantly, it is still known if these techniques will discriminate between the soft, outer, necrotic, highly infected zone that needs to be excavated and the inner reversibly damaged, less infected zone which could be retained. Compared to most single technique, a combination of techniques would ensure better caries removal.
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