INTRODUCTION: The original approach for the treatment of caries was purely surgical. It was thought that the only effective method of eliminating the disease was to completely remove all of the demineralized area of the tooth structure. Even the smallest area of demineralization required the removal of standard amount of sound tooth structure to prevent the progression of disease. This technique had been developed by Dr. G.V. Black as “Extension for prevention” which led to specific of sound tooth structure. Over recent years, the dental profession has shifted towards practicing preventive dentistry and adapting more conservative and tooth preserving procedures. In today’s seminar, I would like to discuss about newer invasive techniques for caries excavation. The techniques available to excavate caries clinically can be classified according to B.D.J. 2000 as: Category Techniques Mechanical, rotary Hand pieces + burs Mechanical, non-rotary Hand excavation, air abrasion Ultrasonics, sonoabrasion Chemo-mechanical Caridex, carisolv and enzymes Photo-ablation Lasers Each of the above mentioned techniques have their own claims of removing demineralize dentin selectively. An ideal method should fulfill certain factors to satisfy, both the operator as well as the patient. They are: Comfort and ease of use in the clinical environment. The ability to dissiminate and remove diseased tissue only. Being painless, silent, requiring only minimal pressure for optimal use. Not generating vibration or heating during periods of operation. Being affordable and easy to maintain. The handpieces and burs are in universal use with their obvious disadvantages like: Sensitive to vital pulp. Pressure/heat on tooth. Necessity of L.A. It was at this point that chemo-mechanical approach came in. It was claimed to be a non-invasive alternative for removal of caries. The technique involved applying a solution onto the decayed dentinal tissue allowing it to soften the tissue and finally scraping it off with blunt hand instrument. Many solutions were introduced and marketed since 1970’s which I would be discussing in detail. Before discussing individual products I would first like to enlighten the layers present in carious dentin. Which have importance in our seminar regarding the chemicals. Carious dentin consists of two layers: Outer layer.
Inner layer. 1. Outer layer: Decalcified – degenerated collagen fibres. Infected – non remienralizable. Necrotic (This layer should be removed). 2. Inner layer. Between outer and normal dentin. Less decalcified. Bacteria free. Remineralized collagen fibres present. Vital odontoblastic process present. This layer should be left intact. Ideally, when preparing the decayed tooth one should remove the outer decayed dentin layer while retaining the inner remineralizable layer intact. The chemomechanical method claims to do so. Let us now see the different products available to us. Chemo-mechanical approach: The chemo-mechanical approach was initially introduced in 1972 in the form of G.K. 101 solution. In 1976, Goldman and Kronman reported on the possibility of removing caries chemically using GK-101 (NMG), which consists of: N-monochloroglycine (NMG). Sodium hypochlorite. Glycine was added to counteract the corrosive effect of NaOCl. Also called as GK-101G. Its mode of action has been described as chlorination of free amino groups i.e. chlorination of amino groups of peptide bonds of protein forming NMG compounds This NMG has the ability to convert hydroxy proline an important factor to pyrole-2-(its glycine peptide carboxy glycine.) Therefore the partially degraded collagen in carious dentin was chlorinated by NMG solution and this also affected the secondary and quaternary structure of collagen by disrupting hydrogen bond. In this way carious material removal was facilitated. GK-101 (NMG) was tested in bovine Achilles tendon collagen to observe as what actually happens to the collagen fibres. SEM evaluation showed. Fraying fibrils – i.e. essential structure was intact, but there was separation of few peripheral fibres. Spinaling fibrils – i.e. attraction between adjacent fibres was lost and there was shortening of individuals fibres. Dissociating fibrils – i.e. structure was totally separating, fibre orientation was poor and hard to define. Amorphous material – i.e. there was little definitive structure and material which was hard to define as collagen. Advantages: Absence of pain. Absence of any deleterious effects on pulp. Studies done by Kurosaki et al and Brannstorm et al showed that it removed only outer carious diseased layer. They presumed that the softening may be due to a
selective attack of the solution specifically on degenerated collagen fibres, without affecting sound fibres of the inner layer and normal dentin underneath. Disadvantages: The process was very slow. Later they found that the system was more effective if glycine was replaced by amino-butyric acid, which evolved in the GK101E, which was approved by FDA (food and drug administration) in 1984 and was commercialized as “CARIDEX” GK-101E, contained instead of NMG – “Nmonochloro-DL-2-aminobutyric acid” (NMAB). The system consists of: reservoir. A heater. A pump. A handpiece with application tip with various shapes and sizes. In vitro studies done by – Goldman et al stated that caridex removed both the layers of caries leaving behind sound dentin. Schertz et al reported that in histological evaluation after using caridex exhibited 90% of caries with residual decay therefore he concluded that caridex should be used with a spoon excavator. Clinical studies done by: 1. Zinek et al showed 90-100% removal of decay with caridex (but it took a very long time.) Rompen and Chorpentier found caridex not bactericidal in 17 samples cultured from the decay. 2. Yip et al combined NMAB + 2 urea in deciduous teeth and found it to be better. Pioch and Stachle investigated the shear strength at the DEJ after treatment of caridex for adhesive and bonding systems. Caridex was found to reduce the shear strength at the DEJ in bovine teeth. This was attributed because of the denaturation of the collagen. This disadvantage to be related to fracture of tooth still needs further clinical studies and investigations. 3. Kurusaki et al, Walkman et al and Wedenberg and Burnstein investigated individually the biocompatibility of caridex to pulp. They found it to be biocompatible because of the alkalinity of caridex, it was found to produce a hard tissue matrix formation below the necrotic zone. Zones: Transient. Dark. Body of lesion. Surface. Yip et al investigated the mineralization of dentinal surface remaining after caridex usage in a small sample. They used “back scattered electron imaging” (BSI) and “electron probe micro-analysis” (EPMA) which measured the surface level of Ca++ and P-. The authors concluded that the amount of Ca and P was 2:1 which matched with the sound dentin because it is better. Other studies have reported that often usage of caridex, the dentinal surface produced. High degree of roughness.
Undercuts. Dentin scales. Dentin tubules were partially patent. Smear free surface. They postulated that it was better for adhesive restorative material without the necessity of acid etching. Zinck et al also evaluated patient acceptance and found out 93% acceptance level. Although caridex had many advantages it was Very expensive. Time consuming. Had bulky delivery system. Needed additional mechanical means to remove decay. Large volumes of solutions were required from (200-500ml.) Following this, a gel based system was introduced in collaboration with medi team (Dental attracting: Gotiberg AB) in 1998 called carisolv (Dental update 2000). Carisolv was initially approved for clinical use in dental practice by the Swedish counter part to US. FDA. Composition: The formulation is isotonic in nature and consists of 2 syringes. Syringes â€“ 0.5% NaOCl Syringe 3 amino acids glutanic Lucine. Lysine. Gel substance â€“ carboxy methyl cellulose Sodium chloride. Sodium hydroxide Erythrosine â€“ to make the gel visible. Saline solution (i.e. colonizing indicator). Mode of action: Carisolv is alkaline in nature with a pH of around 11. Upon mixing, the positively and negatively charged groups of aminoacids become chlorinated due to presence of NaOCl and NaOCl constituents. This leads to interaction with dentin which involves proteolytic degradation of collagen rather than demineralization of collagen, this softening and removal of the carious altered dentin and preserving the sound dentin. The gel consistency allows the active molecules access to the dentin for a longer period than the equivalent irrigating solution in caridex system. This gel also helps by lubricating the hand instrument specifically designed for carisolv. The instrument consists of 4 different handle with 8 interchangable tips ranging from 0.3mm-2mm. These instruments resemble excavators, but they are designed to be used in rapid whisking or curetting fashion, thereby limiting only to diseased tissue. The configuration of instrument allows access to all areas of lesion. Helps to give a tactile sensation. Helps in differentiating between carious and non-carious. Helps to apply the gel.
Cavity preparation: The two syringes should be mixed just prior to use, as its efficiency decreases after 20-30mts. The two gels are mixed till a uniform colour is obtained in a dapen dish. The mixed gel is then applied to carious lesion and left in place for 30 seconds to allow it to degrade the diseased dentin before instrumentation. Rapid, light pressure is applied with instrument to facilitate caries removal. As the caries removal, the gel becomes cloudy with debris indicating cleaning with water. Gel is applied again for further removal. Assessment (i.e. when to stop): 1. When the gel no longer becomes cloudy. 2. Tactile sensation on the carious dentin will present with â€œa catchâ€? whereas in a sound dentin the instrument will pass easily. 3. After completion, the cavity appears frosted and irregular appearance as compared to smooth preparation of conventional bur and hand piece. The reason for their visual difference is that in a conventional preparation the presence of smear layer, which is over the underlying dentin, gives a smooth, glossy appearance. In contrast, in chemo-mechanically treated dentin lacks smear layer and also forms irregular dentin layer giving a matt finish. Patients acceptance: Shorter time. No pain and discomfort. A number of theories have been postulated as to why there is reduce pain. They are: a. Lack of cutting into caries-free dentin. b. Relatively few dentinal tubes are exposed. c. There are no vibrations from drilling. d. No temperature variations. e. Dentin is always covered with a isotonic gel at body temperature. f. Psychologically quiet and less traumatic experience. Indications: 1. Where preservation of tooth structure is important. 2. Removal of root / cervical caries. 3. Management of coronal caries without cavitation. 4. Removal of caries at the margins of crown and bridge abutments. 5. Completion of tunnel preparation. 6. Where L.A. is contraindicated. 7. In anxious patients. 8. In deciduous dentition. 9. A traumatic restorative technique (ART). Advantages over Caridex: 1. Three amino groups are incorporated instead of one because interaction and degradation efficiency is increased. 2. Carisolv has higher viscosity, which allows for application of higher concentration of aminoacids and NaOCl without increasing the total volume or amount (only 0.2-1.0ml carisolv required as compared to caridex i.e. 250-500ml).
3. Increased viscosity also helps in precision placement. 4. The gel does not need to be heated or supplied through a pump. 5. Improved shelf life. In vitro studies: Jepsen et al analyzed collagen structure of residual dentin after usage of carisolv. They found that it differed from sound dentin and had characteristic denatured collagen. In clinical studies: From the abstracts published in Stockholm different authors concluded individually that although carisolv removed 99% of decay, it was slower as compared to conventional techniques. Enzymes: Studies have examined that caries could be removed by enzymes: 1989, Goldberg and Keil successfully removed soft carious dentin using bacterial achromobacter collagenase which did not effect sound dentin. Enzyme pronase, a non specific proteolytic enzyme originating from streptomyces griseus also helps in removing caries. Still experiments are going on for the validity of such enzyme. CONCLUSION: As with all new procedures, there are the uncertainty of learning new techniques, using new techniques, clinical time, cost etc, which need to be considered on an individual level. Over the decades, dentistry has changed dramatically and practitioners follow the new trends and master new techniques. Chemo-mechanical means removes less sound tooth structure and reduced pulpal irritation. This technique can help to supplement and complement other methods of caries removal, further research and clinically based experiments are required for acceptance of such new techniques. REFERENCES: 1. Chemo-mechanical method of caries removal â€“ Dental Update, 2000; 27; 398-401. 2.