A Comparison Of Caries Excavation Methods

A comparison on the use of Mechanical Excavation, Carisolv and Erbium lasers on the removal of caries Introduction Denial caries is a biological and chemical process that can occur on any tooth surface in the oral cavity where dental plaque is allowed to accumulate over a period of time. Plaque is an example of a biofilm on tooth surfaces so it is not simply just a random collection of bacteria but an organised colony working collectively. This community has a collective physiology and works together. The bacteria in the biofilm are always metabolically active. Within the biofilm there are bacteria known as aciduric bacteria which are able to produce acid from dietary carbohydrate, this in turn can cause demineralisation of tooth tissues. The formation of is a naturally occurring process which cannot be prevented however the progression of disease can be controlled so that a caries lesion is never formed. Alternatively, a carious process can become arrested and even an advanced carious lesion can come to a halt. However, if the lesion is not adequately controlled, caries can progress into the dentine and ultimately result in bacterial invasion, death of the pulp and spread of infection into the periapical tissues, causing pain.1 Key tooth structure cannot be restored once it is destroyed; however remineralisation of very small carious lesions is possible if dental hygiene is kept at an optimal level. For small lesions topical fluoride can be used to encourage remineralisation and for larger lesions the progression of dental caries can be stopped by treatment. The aim of treatment is always to preserve tooth structures and prevent further loss of the natural tooth. Methods for caries removal and cavity preparation have been under strong pressure to become more minimally invasive and more comfortable for patients. Current caries removal systems use the drill on a high speed hand piece to gain access to the carious lesions, and a low speed hand piece to remove carious dentine. This can be unpleasant and painful for patients and local anaesthesia is usually required to control the pain. Due to this, a dentist must be aware of the impor¬tance of preserving tooth tissue, combined with a patient-friendly approach. It has been shown that operative treatments can often lead to the need for further operative and more inva¬sive treatment. 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 absolutely necessary. The best way to ensure a maximum life for the natural tooth is to leave as much of the sound tissue alone and protect it from damage by using minimally invasive techniques in restorative dentistry.2

There are a variety of techniques available for cutting tooth tissue. Some claim to selectively remove demineralised dentine whilst others are not able to make this distinction so well. Some techniques may not even be able to remove softened tissue effectively. For this reason it is important that the practitioner knows what might be expected from these various techniques. This particular article compares the use of rotary hand pieces, Carisolv and Erbium lasers in the caries removal process.

Methods Mechanical Excavation Mechanical Excavation is currently the conventional method for caries removal. The first step in in the process is to establish the ideal outline form. The enamel must first be penetrated using a high speed hand-piece and a flat pulpal floor which is 0.5mm in to the dentin should first be established. When a tooth has an open carious lesion which only minimally penetrates the dentin, the entire carious lesion is removed during an ideal cavity preparation.3 However, this is not the case when the carious lesion is extensive and extends beyond the ideal depth. In this case of an extensive carious lesion, an ideal outline form is first established, and only after the initial cavity preparation is completed, is the remaining carious dentin removed. The purpose of completing the initial cavity preparation before extending axially or pulpally is twofold. First, it allows adequate visibility and convenience for accessing and removing the remaining carious lesion. Secondly, completion of the initial cavity preparation allows immediate placement of a base or restoration, especially if there is a pinpoint pulpal exposure. This would not be possible if the carious lesion still needed to be removed along the lateral walls. The carious lesion is then inspected on the lateral walls, the buccal and lingual walls, as well as on the pulpal floor. The next step is to extend laterally to the point that the carious lesion is isolated. The goal is to place the walls 0.25 to 0.5mm beyond the carious lesion. This extension is to isolate the carious lesion pulpally by placing the walls in a sound and intact dentino-enamel junction.4 With the carious lesion exposed and isolated, and all the lateral walls and enamel rods supported by a sound dentino-enamel junction, removal of the remaining carious lesion may start. At first a low speed hand piece with the largest round bur that will fit in the carious lesion is used with light force and a wiping motion. The picture below is an example of a round rose head bur that should be used with a slow piece to remove carious dentin. An excavator should also be used to remove carious dentin as they have a lower risk of causing pulpal exposure. Forces for the purpose of removing defective dentin should be directed laterally and not towards the centre of the carious lesion. Caries removal starts from the lateral borders of the lesion. In the deeper areas, instrumentation should be done with a light force and extreme care.5 The carious lesion is removed in a spiralling manner, beginning with the most superficial caries at the outer lateral wall. As firm dentin is reached laterally, it is followed to the central area. The only area where the carious lesion remains is the very centre, the lateral walls are clean. The deepest area of the carious lesion over the pulp is isolated and removed last.

Carisolv When caries occurs, bacteria in plaque produces acids which dissolve the minerals in enamel. As this process continues, the bacteria and penetrating acids are allowed to pass through the tooth structure via dentinal tubules which results in further decrease of pH and acid attack causing more demineralisation. 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 hydrolases.6 Within a carious lesion there are normally two zones which can be identified. There will be an inner layer where there may be partially degradation but the collagen fibres would still be intact so this region would have the capability of being re-mineralised. There will also be an outer layer where the collagen fibres are partially degraded so this region cannot be re-mineralised.7 Based on the characteristics of this outer layer it must have been possible to find a chemo-mechanical caries removal agent that could target and completely degrade this partially demineralised region. . In the 1980`s a system of this kind came onto the market. It consisted of two solutions. Solution I contained sodium hypochlorite and Solution II contained glycine, aminobutyric acid, sodium chloride and sodium hydroxide. The two solutions were mixed immediately before use to give the working reagent which was stable for one hour. A special delivery system had to be used with the reagent where the solution would be warmed to body temperature using a heater and pumped through a tube into the hand piece which had an applicator tip. The applicator tip came in various shapes and sizes and was used to loosen the carious dentine via a gentle scraping motion. The debris together with the spent solution was then removed by aspiration. Application was continued until the dentine remaining was deemed sound by normal clinical tactile tests. After 5-10 minutes of treatment on suitable accessible soft lesions, only clinically sound dentine remained.8 Carisolv hit the headlines in January 1998. Although this is similar to the Caridex systems in its mechanism of action, it is in the form of a pink gel which can be applied directly to the carious lesion with using hand instruments and no special delivery system is needed.9 Also, the volume required is under a millilitre since it is in the form of a gel. A new twin syringe mixing system containing sufficient material for 10-15 treatments has been introduced. This dispenses the exact amount required through a disposable mixing tip, and it can be active for up to one month if stored in a refrigerator after opening. The gel is applied to the carious lesion with one of the hand instruments and after 30 seconds, carious dentine can be gently removed. More gel is then applied and the procedure repeated until no more carious dentine remains. When the gel removed from the lesion is clear, this will be a sign that the carious dentine has been removed. The time required for the procedure is about 9-12 and the volume of gel is only 0.2-1.0ml. Rotary instruments may still be required for some cavities but reports indicate that patient acceptance is very good.

Erbium Laser The laser has been increasingly used in medical and dental applications in the past two decades and several wavelengths have been investigated as a substitute to high speed hand pieces. High intensity lasers(Erbium Lasers) are able to promote controlled temperature rises in a small and specific area of dental hard tissue. Depending on the temperature rise and the interaction of laser irradiation with dental tissues, it is possible to produce specific micro structural and mechanical changes related to a correct clinical application. The use of lasers for cavity preparation and caries removal is based on the ablation mechanism, in which dental hard tissue can be removed by thermal or mechanical effect during laser irradiation.11 The thermal ablation process that occurs in dental hard tissues is also known as explosive(water-mediated) tissue removal. This process can be explained as a result of the fast heating of the subsurface water confined by the hard tissue matrix, due to the higher interaction with infrared laser irradiation. The heating of these water molecules leads to an increase on molecular vibration and an increase on subsurface pressures that can exceed the strength of the above tissue. Finally, there is an `explosion` of tissue due to the material failure, resulting in the removal of the material.12 This process has been studied for the past 30 years, with the intention of choosing the best laser wavelength and parameter to effectively promote tissue removal or selective caries removal with minimal thermal consequences. Depending on laser wavelength and tissue characteristics, laser irradiation can be absorbed, scattered, reflected or transmitted into dental tissues. These effects must be well known by professionals to help them choose the best equipment for a specific clinical application and to avoid thermal and mechanical damages to the target and surrounding tissues. Depending on the clinical situation, dentists need different laser wavelengths and irradiation parameters to obtain distinct effects on the same tissue. Erbium lasers are also effective on removal of dental caries. In vitro studies revealed that Er:YAG can selectively remove dental caries due to the higher amount of water and organic content compared to that of sound tissues. It is therefore possible to obtain a conservative therapy, with no removal of sound tissue and lack of thermal damages.13 However, the adjustment of laser energy density in commercial equipment is sometimes difficult to promote the selective ablation of infected dentin. Also, the clinical results still depend on the experience and knowledge of the professional, added to the use of manual instruments for correct diagnosis of remaining tissue. In fact, clinical trials report the well acceptance of patients, the maintenance of pulp vitality and marginal seal, the good quality of restorations and the absence of secondary caries even after two years.14 Also, it is reported that these lasers can fulfil the requirements of Minimal Invasive Dentistry, due to the possibility of conservation of the sound tissue structure during caries removal and to the possibility of surface decontamination of affected dentin.

Results/ Pros and Cons: A study was carried out in Fatima Jinnah Dental College Hospital, Karachi from October 2003 to March 2004.15 The study involved thirty patients with mandibular molars which were carious on both sides. One side of each patient was randomly selected for treatment Carisolv and the other using conventional methods. In the study group, the carious lesion was treated with Carisolv, and in control group excavators and rotary hand pieces were used. A single person observed all of the treated lesions. Time required to remove caries and extent of caries removal was observed for both techniques. Carisolv proved to be just as effective as hand pieces in removing caries and had no effect on healthy enamel and dentine. The average time taken to remove caries using Carisolv was 12.19 minutes and with the traditional burs the average time was 7.4 minutes.15 Despite this drawback Carisolv proved its value since the method is minimally invasive and affects only the carious part of the tooth. As a result, the teeth last longer, the risk of complications is reduced and patient comfort is enhanced. An improved, faster acting chemo-mechanical reagent should be developed with longer shelf life after opening. Cavity preparations by Erbium laser irradiation were investigated in 50 teeth of 44 patients aged 23-58 years in Japan in 2002.16 No adverse reactions such as systemic/localized allergy were observed in any of the cases. Regarding intraoperative pain as¬sessment, no pain at all was felt in 34 cases (68%). However, slight pain was felt in 11 cases (22%), in two cases (4%) pain was tolerable; and in three cases (6%) pain was intolerable to the patients. Regarding intraoperative discomfort, 42 of 50 cases (84%) felt no discomfort at all and in eight eases (16%) the machine noise was slightly uncomfortable. During the assess¬ment of cavity preparation completion, it was found that cavity preparation was completed with the laser system alone in 47/50 cases (94%). However, additional anaesthesia was neces¬sary in 3/50 cases (6%).16 Clinical trials have demonstrated that Erbium lasers can be considered a safe and efficient treatment for caries removal, since it is reported that pulpal response is similar to those obtained by the use of conventional bur. Also, due to the lack of noise, pressure, discomfort and sometimes the necessity of local anaesthesia, it is reported a good compliance of patients, mainly the paediatric ones. However, it must be emphasized that the time necessary to remove caries by laser irradiation is almost two or three times longer than the bur treatment, depending on the repetition rate and energy. The increase of energy density and repetition rate can lead to discomfort and pain to patients, besides increasing the surface temperatures. For this reason the strategies used for improving the laser ablation speed are limited. Conclusion It can be concluded that the use of Carisolv and Erbium Lasers are just as effective as rotary instruments in the removal of caries with the added benefit of reduced anaesthetic and low annoyance. These systems can be especially useful on patients with a phobia of dental procedures. The main disadvantage of to the use of Carisolv and Erbium Lasers is the extended time needed in cavity preparation so it comes down to the patient whether time or comfort is the most important factor.

References 1)Edwina Kidd (2005) Essentials of Dental Caries, 3rd edn., Oxford University Press: 2)Hiremath (2006) Textbook Of Preventive And Community Dentistry, : Elsevier India. 3)Satish Chandra (2008). Textbook of Operative Dentistry. New Delhi: Jaypee Brothers. 86-8 4)Graham J Mount. (2009). cavity classification & preparation. Minimal intervention dentistry. 1 (1), p150-162 5)Suzanne Noble. (2012). Suzanne Noble. In: Suzanna Clinical Textbook of Dental Hygiene and Therapy. New York: John Wiley & Sons. 6)Thylstrup A, Fejerskov O. Text book of Clinical Cariology. (2nd ed) 111-157. Copenhagan: Munksgaard 1994. 7)Ogushi K, Fusayama T. Electron microscopic structures of two layers of carious dentine. JDent Res 1975; 54: 1019-1026 8)Burke F, Lynch E. Chemomechanical caries removal. J Irish Dent Assoc 1995: 41; 10-14 Yip H K, Beeley J A, Stevenson A G 9)24 Ericson D, Simmerman M, Raber H, Götrick B, Bornstein R. Clinical evaluation of efficacy and safety of a new method for chemomechanical removal of caries. Caries Res 1999; 10)Moran C, Lynch E, Petersson L, Borshboom P. Comparison of caries removal using CarisolvTM or a conventional slow speed rotary instrument. Caries Res 1999; 33; 313 10)Moran C, Lynch E, Petersson L, Borshboom P. Comparison of caries removal using CarisolvTM or a conventional slow speed rotary instrument. Caries Res 1999; 33; 313 11)Neves, A.A., Coutinho, E., De Munck, J. & Van Meerbeek B. (2010). Caries-removal effectiveness and minimal-invasiveness potential of caries-excavation techniques: a micro-CT investigation. Journal of Dentistry. Vol.39, No.2, pp.154-62. 12)Ana, P.A., Bachmann, L. & Zezell, D.M. (2006) Lasers effects on enamel for caries prevention. Laser Physics, Vol.16, No.5, pp. 865-75. 13)Eberhard, J., Eisenbeiss, A.K., Braun, A., Hedderich, J. & Jepsen, S. (2005) Evaluation of selective caries removal by a fluorescence feedback-controlled Er:YAG laser in vitro. Caries Research. Vol.39, No.6, pp.496-50 14)Yazici, A.R., Baseren, M. &, Gorucu, J. (2010). Clinical comparison of bur- and laser prepared minimally invasive occlusal resin composite restorations: two-year follow-up. Operative Dentistry. Vol.35, No.5, pp.500-7. 15)Hosein T, Hasan A.. (2004). Efficacy of chemo-mechanical caries removal with Carisolv. J Coll Physicians Surg Pak.. 18 (4), p222-225. 16)Matsumoto K, Hossain M. (2002). Clinical assessment of Er,Cr:YSGG laser application for cavity preparation. J Clin Laser Med Surg. 20 (1), 17-21