|Year : 2012 | Volume
| Issue : 2 | Page : 115-121
Comparison of mechanical and chemomechanical methods of caries removal in deciduous and permanent teeth: A SEM study
A Avinash1, SD Grover2, M Koul2, MT Nayak3, A Singhvi3, RK Singh4
1 Department of Paedodontics & Preventive Dentistry, Rungta College of Dental Sciences and Reaearch, Bhilai (C.G), India
2 Department of Paedodontics & Preventive Dentistry, Career Post Graduate Institute of Dental Sciences and Hospital, Lucknow (UP), India
3 Department of Oral Pathology & Microbiology, Vyas Dental College & Hospital, Jodhpur (Rajasthan), India
4 Department of Paediatric and Preventive Dentistry, Faculty of Dental Sciences, Chhatrapati Shahuji Maharaj Medical University, Lucknow (UP), India
|Date of Web Publication||23-Aug-2012|
Department of Pedodontics & Preventive Dentistry, Rungta College of Dental Sciences, Kohka- Kurud road, Bhilai-490024 (C.G)
| Abstract|| |
Background: Mechanical method of caries removal is associated with the removal of sound tooth structure, production of pain, heat, annoying sounds, and vibrations. Chemomechanical caries removal method is based on removal of only carious dentin leaving sound dentin intact. Aim: The aim of this study was to compare the efficacy of mechanical and chemomechanical methods of caries removal in deciduous and permanent teeth. Study Design: A total of 30 carious teeth including 15 deciduous and 15 permanent teeth having dentinal caries selected randomly and cut into two halves through center of the lesion, were subjected to caries removal by mechanical (Group A), and chemomechanical methods (Group B). Time taken for removal of caries was noted with stopwatch. Samples were prepared and seen under the scanning electron microscope for the presence of bacterial colonies. Data were analyzed using statistical package for social sciences (SPSS) Software. Results: No significant difference was found for the presence of bacterial colonies in both groups of deciduous and permanent teeth; however, time taken for caries removal by the chemomechanical method was twice than the mechanical method. Conclusion: despite the insignificant presence of bacterial colonies and twice time taken as compared to mechanical method, chemomechanical method was easy to introduce, was painless, did not form smear layer and conserved the sound tooth structure.
Keywords: Bacterial colonies, caries removal, chemomechanical, mechanical
|How to cite this article:|
Avinash A, Grover S D, Koul M, Nayak M T, Singhvi A, Singh R K. Comparison of mechanical and chemomechanical methods of caries removal in deciduous and permanent teeth: A SEM study. J Indian Soc Pedod Prev Dent 2012;30:115-21
|How to cite this URL:|
Avinash A, Grover S D, Koul M, Nayak M T, Singhvi A, Singh R K. Comparison of mechanical and chemomechanical methods of caries removal in deciduous and permanent teeth: A SEM study. J Indian Soc Pedod Prev Dent [serial online] 2012 [cited 2014 Mar 7];30:115-21. Available from: http://www.jisppd.com/text.asp?2012/30/2/115/99982
| Introduction|| |
In every field of dentistry, an awareness of the importance of preserving tooth tissue, combined with a patient-friendly approach, is becoming self-evident. Wherever possible, tissue should be preserved; invasive treatment should be kept to a minimum and natural tissue should be replaced with artificial substitutes only when it is absolutely unavoidable. The best way to ensure maximum life for the natural tooth is to respect the sound tissue and protect it from damage by using minimally invasive techniques in restorative dentistry. 
Dental caries is considered one of the most serious dental diseases that results in localized dissolution and destruction of the calcified tooth tissues and eventually leading to the infection of the dental pulp when left untreated. Usually, dentinal caries could be recognized as two distinct successive layers, which are different in their clinical features, as well as in their microscopic and chemical structures. The outer layer (infected dentin) is highly decalcified and infected with bacteria. Despite the possible discoloration, the inner layer (affected dentin) is less decalcified with intact collagen fibers and no bacterial invasion. Moreover, it is more resistant to the proteolytic attack and the progression of carious lesions. In this instance, there is no necessity to continue preparing the tooth until the dentin is stain-free. But the ability to discriminate and remove only the diseased tissue remains essential. 
Due to continuous advancement in mechanical and adhesive properties of dental filling materials, the excessive tooth cutting required to obtain resistance and retention form in conventional cavity preparation is minimized. Traditional means of cavity preparation are based on a philosophy of extension for prevention and includes high-speed handpieces and slow rotating instruments. However, this modality of cavity preparation usually induces pain, annoying sounds and vibrations. Drilling often removes parts of tooth, which are healthy, in addition to the decayed areas. This weakens the tooth and makes it less durable in the long run. Therefore, chemomechanical removal of caries has been developed as an alternative to the conventional methods of removing caries. 
The idea of chemomechanical caries removal has been developed in 1970s by an endodontist M. Goldman, while using five percent sodium hypochlorite (5% NaOCl) in removing organic materials in the root canals.  This chemical got the ability to dissolve carious dentin and since that time, the idea of removing caries by chemical means was borne. The chemomechanical method of caries removal was first introduced in 1975 by Habib et al. by using 5% sodium hypochlorite (NaOCl), followed by introduction of GK-101 in 1976 by Goldman et al. However, NaOCl itself was too corrosive to be used on healthy tissues because of its high reactivity and its ability to decompose non-necrotic tissue. Subsequently NaOCl was diluted and buffered with sodium hydroxide, sodium chloride, and glycine producing a solution of 0.05% N-monochloroglycine (NMG) having a pH of 11.4, commercially known as GK 101. It was followed by introduction of N-Monochloro-D-2-Aminobutyrate (NMAB), that is, GK101E (CARIDEX) in 1984.  CAREIDEX proved to be useful in chemical caries removal however it had unpleasant taste, lengthy procedure time (10-15 min), use of large volumes of solution (200-500 mL), complicated delivery system and high cost limits, which led to the introduction of CARISOLV system developed by the Swedish Medi Team in 1997.
Various in vivo and in vitro studies have been reported for the effectiveness of Carisolv in primary and permanent teeth. , The purpose of this study was undertaken to evaluate and compare the efficacy of chemomechanical material (Carisolv) and the mechanical method of caries removal in deciduous and permanent teeth under the scanning electron microscope (SEM).
| Materials and Methods|| |
This study was carried out in the Department of Paedodontics and Preventive Dentistry, Career Post Graduate Institute of Dental Sciences, Lucknow (UP) and Birbal Sahni Institute of Paleobotany, Lucknow (UP). Freshly extracted human primary and permanent carious molars were selected randomly for the study. The teeth were stored in phosphate-buffered saline containing 0.2% (w/v) sodium azide at 4°C. All soft tissue and extrinsic deposits were removed from the teeth using hand scalars and the debris was cleaned with slurry of pumice and water followed by rinsing in distilled water and dried with compressed air for 5 s. Each tooth was sectioned through the centre of the lesions into two halves in the mesiodistal longitudinal plane using a diamond-impregnated circular disc (Sanwa Diamond Tools Pvt. Ltd.-India) on a slow speed micromotor hand piece with water slurry. The cut surface of both pieces of each tooth was visually examined to see the extent of carious lesion. The teeth in which carious lesion extended up to the dentin were considered in the study and a total of 30 carious including 15 deciduous and 15 permanent teeth were selected.
The two halves of each deciduous and permanent tooth were divided into two groups: Group A and Group B according to the method of caries removal used, that is, the mechanical method and chemomechanical method.
In Group A, the carious lesion from one half of each tooth was removed mechanically with a slow-speed size 3 round steel bur (Mani inc.) until it was caries free whereas, other half of the same tooth was removed chemomechanically with Carisolv gel (Dr. Reddy's Lab). Carious lesion was covered with Carisolv gel and left undisturbed for 30 s according to the manufacturer's instructions. When the gel was cloudy, it was removed gently by scraping with the spoon excavator without applying pressure, after which additional fresh gel was applied on the excavation site. The removal of carious dentin was continued until the gel was no longer cloudy. The gel was then removed and the cavity was wiped with a moistened cotton pellet and rinsed with lukewarm water. The cavities prepared with each caries removal system were checked as being caries-free with visual and tactile criteria [Figure 1]. The preparation time for each caries removal technique for each sample was noted using a stopwatch. For the mechanical method, the time was calculated from the beginning of caries removal with a bur until it was free from caries, whereas for Carisolv gel the time was calculated from the start of application of gel until it was no longer cloudy.
Each sample was rinsed in distilled water and placed in 2.5% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) for a minimum of 24 h, then washed and dehydrated in a series of graded alcohol solutions (50%, 70%, 80%, 95%, and 100%) for 10 min each. Then the specimens were mounted on aluminum stubs with a vacuum resistance adhesive tape and a thin silver foil was placed on the corner of the samples. Silver paint was applied on each stub to give continuity for analysis. Each stub was given a code number to keep record for reference. Specimens were than coated with metal (gold-palladium alloy) under vacuum pressure (Polaron sputter coater SC 7640). Gold palladium coating is based on the phenomenon of ion sputtering by the establishing of electromagnetic field under vacuum between gold palladium disc in the center and the conductive silver paint on the mounted aluminum stubs attached all around the disc. Then the specimens were evaluated by using a scanning electron microscope (LEO 430 Oberkochen, Germany) and images were captured. SEM observations were performed by a single examiner.
|Figure 1: Samples after caries removal ( a ) deciduous teeth and ( b ) permanent teeth|
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Each of the coated samples was scanned under SEM at an accelerating voltage (15 KV). Representative photomicrographs of the dentinal surface of the specimens were taken to analyze the presence or absence of bacterial deposits and micromorphological changes after caries excavation. The carious lesion of each specimen was divided into six equal fields and bacterial deposits were seen in each field at the magnification of ×1000. The bacterial deposits on the carious surface of the specimens were then recorded from the photographically enlarged photomicrographs, which were enlarged to ×5000. When the bacterial deposits were seen in four or more than four fields in each specimen, it was marked as bacteria present and absent when seen in less than four fields. The presence or the absence of bacterial deposits of each specimen was noted [Figure 2],[Figure 3],[Figure 4] and [Figure 5] and the data were collected in the tabulated form. Similarly, the surface roughness and the presence or absence of smear layer was also seen in both mechanical and chemomechanical group. The data thus obtained was subjected to statistical analysis.
|Figure 2: Scanning electron microscopy of deciduous teeth treated with mechanical method ( a ) showing no bacterial deposits and ( b ) showing bacterial deposits|
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|Figure 3: Scanning electron microscopy of deciduous teeth treated with chemomechanical method ( a ) showing no bacterial deposits and ( b ) showing bacterial deposits|
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|Figure 4: Scanning electron microscopy of permanent teeth treated with mechanical method ( a ) showing no bacterial deposits and ( b ) showing bacterial deposits|
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|Figure 5: Scanning electron microscopy of permanent teeth treated with chemomechanical method ( a ) showing no bacterial deposits and ( b ) showing bacterial deposits|
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| Results|| |
The statistical analysis was done using SPSS (Statistical Package for Social Sciences) Version 15.0 Software. The values were represented in Number (%) and Mean ± SD. In deciduous teeth, bacterial colonies were found in 13.33% and 33.33% in group A and group B, respectively, while in permanent teeth, 13.33% and 40% specimens showed the presence of bacterial colonies in group A and group B, respectively. There was no significant difference in the presence of bacterial colonies in both the groups of deciduous and permanent teeth [Table 1]. For deciduous teeth, the mean time taken for procedure in Group A was 2:33 ± 0:12 minutes:seconds, while in Group B it was 4:59 ± 0:21 minutes:seconds, thereby showing that in Group B, the mean time taken was significantly higher as compared to Group A (P < 0.001).
|Table 1: Comparison of deciduous and permanent teeth for presence of bacterial deposits|
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For permanent teeth, the mean time taken for procedure in Group A was 2:43 ± 0:28 minutes:seconds while in Group B it was 5:10 ± 0:38 minutes:seconds, thereby showing that in Group B, the mean time taken was significantly higher as compared to Group A (P < 0.001) [Table 2].
| Discussion|| |
In ancient times, the caries removal was done with the use of hand drill, which was later surpassed in 1871 by James Morrison's instrument developed from Issac Singer's sewing machine.  This led to the evolution of rotary instruments - from low speed to ultrahigh speed. However, the removal of dental caries using rotary instruments is frequently associated with thermal and pressure effects on the pulp producing pain. Moreover, drilling may also involve the removal of sound tooth tissue adjacent to the caries affected area.  Due to the shortcoming of the drill, alternative techniques such as air abrasion, sonoabrasion, ultrasonic instrumentation, laser, and chemomechanical approach to caries removal were developed. Out of these, air abrasion, sonoabrasion, ultrasonic instrumentation and laser are costly and tooth - sensitive methods and therefore, less frequently used. ,
The chemomechanical method of caries removal has a disintegrating effect on caries tissue, while leaving healthy dentin largely intact. The affected tissue consists of mostly demineralized, partly disrupted collagen fibers together with other components of the dentin extracellular organic matrix.  The chemomechanical caries removal reagent must be able to cause further degradation of partially degraded collagen, by cleavage of the polypeptide chains in the triple helix and/or hydrolyzing the cross linkages. Chemomechanical caries removal with Carisolv TM involves chemical softening of carious dentin followed by its removal by gentle excavation. 
The Carisolv gel TM comprises of a clear fluid of high viscosity which contains three different aminoacids (glutamic acid, lucine, and lycine), sodium chloride, water and sodium hydroxide, and a transparent fluid consisting of sodium hypochlorite. When the gel and fluid are mixed, amino acids bind chlorine and form chloramines at a pH of 11. The formation of chloramines, reduce the reactivity of chlorine without altering its chemical function. The result of this process is breakdown of degraded collagen found in demineralized portion of a caries lesion.  The degraded collagen has an open structure and is therefore more susceptible to further breakdown by chloramines. The porous nature of demineralized dentin allows penetration of Carisolv. The unaffected collagen is more resistant to degradation but the framework of degraded collagen is broken down and can be easily scrapped away. 
Depth of microbial invasion cannot be diagnosed with clinical criteria for complete caries removal.  In chemomechanical group 37% of samples and in mechanical group 13% showed the presence of bacterial colonies. It is well known that it is not always possible to remove the bacteria completely from the cavity. However, previous study state that these number of microorganisms are not that virulent to cause dental caries and could be considered as clinically acceptable. Knight showed that lactobacilli, staphylococci, and streptococci could persist under the restorations for a considerable time; however, it was pointed out that conditions are unfavorable for the bacterial growth and metabolism when they are separated from the oral environment. 
In this study, the SEM analysis showed slightly higher occurrence of bacteria after the chemomechanical caries removal (Carisolv) when compared to the mechanical method. This finding could be explained by less extensive preparation with Carisolv when compared to the one with mechanical drill. Chemomechanical method (Carisolv) preserves the sound dentin where remaining bacteria can be found. On the other hand, Yazici et al. explain the presence of bacteria by the absence of smear layer in the chemomechanically treated cavities, which enables direct pushing of bacteria into the dentin tubules with hand instruments. 
In this study, high occurrence of bacterial colonies was observed near dentinoenamel junction. It is confirmed with the histological study of Cederlund et al., in which residual caries was not observed in dentin after the chemomechanical caries removal, while it was a frequent finding at the dentinoenamel junction (6 of 10 cavities).  Yazici et al. reported more frequent presence of bacteria after the Carisolv treatment (9 out of 14) when compared to the conventional rotary instruments (1 out of 14), especially at the dentinoenamel junction.  This is why it is very important to assure the direct access to the dentinoenamel junction. Carisolv gel cannot act chemically to the undermined enamel, and in that case carious lesion will not be exposed to the gel enough.
Results of this study are similar with those of earlier SEM studies of permanent dentin characteristics after the chemomechanical removal. ,, Those investigations showed irregular, porous surfaces with opened dentin tubules. The smear layer was minimally formed , or could have not been observed.  Hosoya et al. investigated the influence of Carisolv treatment on sound human primary and young permanent dentin and found Carisolv to be more effective in removal of the smear layer in primary dentin than in permanent dentin.  However, the present study does not confirm differences in removal of smear layer between deciduous and permanent dentin. The absence of a smear layer is a result of the specific preparation technique without thermal or mechanical effects, the high pH of the gel,  and the proteolytic action of NaOCl.  On the other hand, Cederlund et al. reported smooth, smear-like dentin surfaces with occluded tubules after the treatment with Carisolv.  These findings cannot be explained, although, the protocols of investigations of Cederlund et al. were the same or similar to the other studies of dentin surfaces after the chemomechanical caries removal. ,,
In the operative treatment of carious lesions in dentin, the morphology and nature of the prepared dentin surface influences bonding of adhesive restorative materials. After mechanical removal of caries with rotary instruments, an amorphous layer is formed on the surface of the dentin. ,, The presence of smear layer can affect the adhesion of modern dental materials.  Thus, it has to be removed or modified prior to the placement of the restoration. The fact that the dentin surfaces are irregular, without an extensive smear layer and with open tubules induced a thought that these characteristics could improve bonding between restoration and tooth.  However, the microtensile bond strengths of different dentin adhesives did not differ between the chemomechanical technique, conventional burs, sonic preparation system, and air abrasion,  or between chemomechanically treated dentin and healthy dentin.  In addition, shear bond strengths of different adhesive systems did not differ after chemomechanical and conventional treatment with burs. 
Several studies have compared the time taken for Carisolv caries removal with conventional excavation and/or the use of round burs. , This Carisolv system generally takes longer time. In the present study, the mean time required for caries removal with the Carisol in permanent teeth was 5 min and 10 s and 4 min and 59 s for deciduous teeth which were longer than drilling.
These values are in conformity with the results obtained by Ericson et al. and Munshi et al. However, if time for anesthesia is included in the time for drilling, the time taken for Carisolv procedure could be considered less. Moreover, the decreased need for local anesthesia could be useful especially for children and older patients with medical problems. On the other hand, patients have considered the Carisolv procedure to be faster, most probably due to the comfort and pain-free technique associated with this system.
| Conclusion|| |
In conclusion, the chemomechanical method demonstrated the presence of insignificantly higher number of bacterial colonies and took twice time to remove caries in both deciduous and permanent teeth but was easy to induce, did not form smear layer and conserved the healthy tooth structure. Further research is needed into this topic, to assess whether this method will help to supplement or complement other methods of caries removal in primary and permanent teeth.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]