In 1976, Goldman et al. described a commercially available system - 'Caridex' - for chemo-mechanical excavation for the first time ever. Caridex was removed from the market relatively quickly because of its insufficient excavation results and was followed by Carisolv (MediTeam, Gothenburg, Sweden) in 1997).
One problem of chemo-mechanical removal of caries using Carisolv is the time needed for treatment; compared to rotary instruments it is very long. For this reason, the manufacturer of Carisolv changed its composition. Since 2002, an improved version of Carisolv has been available on the market.
Carisolv is a gel which is supposed to dissolve only the outer layer of dentine caries which is then removed with special manual instruments. As described for SmartPrep/SmartBur, Carisolv is to remove the non-remineralisable layer of dentine caries but not touch the remineralisable layer.
Carisolv consists of 2 components that are mixed immediately before treatment is started.
Component 1 contains:
- 7.5 mg of the amino acids leucine, lysine and glutamic acid in distilled water,
- sodium hydroxide,
- carmellose (to increase viscosity).
Component 2 contains:
- 0.95 percent sodium hypochlorite.
During use, the pH value is 12. Compared with the first Carisolv formulation, the NaOCl concentration in the new Carisolv has been doubled, and the content of the amino acids glutamic acid, leucine and lysine reduced by half. The red colouring agent erythrosine (E 127B) is no longer contained.
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Effect of Cariosolv
If components 1 and 2 of Carisolv are mixed, the sodium hypochlorite reacts with the amino acids and is changed to chloramines; the binding of Cl to the amino group is unstable. Therefore, in carious dentine, chloration of denaturated collagen is possible; hydroxyproline is then converted into pyrrol-2-carboxylic acid.
The weakened collagen structure between the outer and the intact parts of dentine caries is destroyed and the collagen molecule dissolved by chloration of functional groups that are important for the secondary and quarternary collagen structures.
The amino acids reduce the hypochlorite's aggressiveness so that only the denaturated collagen in the dentine damaged by caries is dissolved, not the intact collagen in healthy dentine
. Otherwise, the part the amino acids lysine, leucine and glutamic acid play in chemo-mechanical removal of caries seems to remain unclear.
Strid and Hedward (1987) observed that the three differently charged amino acids (lysine = positive, glutamic acid = negative, and leucine = neutral) result in different interactions with the denaturated collagen if combined with NaOCl. Electrostatic interactions occur as well as diffusion.
Use of the three chloro-amino acids of Carisolv with their lateral chains' different characteristics may thus result in electrostatic reactions with the three protein fractions which can be effective against caries. NaOCl alone is not able to release the proteins' co-valent peptide bindings, neither type 2 nor type 3 collagen chains. Only the combination of the three differently charged amino acids (positive, negative, neutral) which pave the way for the NaOCl, and the NaOCl itself results in the three different reactions between the chloro-amino acids and the denaturated dentine:
- Diffusion produces an electrostatic effect of the components of the changed dentine.
- Organic tissue becomes hydrophilic due to the high pH. This enables the chloro-amines to penetrate into the demineralised dentine.
- The loosely bound chlorine ions of the unstable chloro-amino acid molecules react with the dentine's carious collagen.
Selective removal of dentine caries
One the one hand, the high pH-value of 12 results in ballooning of the organic tissue thus facilitating the penetration of chloro-amines into the demineralised part of the lesion, whilst on the other hand, it will not dissolve the dentine's mineral parts.
This differentiation protects healthy dentine.
Though Carisolv initially dissolves changed collagen and causes damage to cellular components such as the odontoblast processes, it will not damage healthy collagen fibrillae, and thus healthy dentine.
Therefore, only the part of the dentine beginning to be chemically dissolved can be removed mechanically, not enamel and healthy dentine.
This defined endpoint of caries removal is the special feature of chemo-mechanical dentine caries excavation when compared with other excavation methods (above all those using a rose-head burr).
"Over-excavation" is not possible.
Chemo-mechanical caries excavation can thus be considered a minimally-invasive form of treatment; however, the question as to the effectiveness of the method producing sufficient removal of caries remains.
The effectiveness of Carisolv in the original formulation for caries excavation has been assessed in in-vivo and in-vitro studies. In own experiments, the effectiveness of Carisolv was compared with conventional methods to remove carious dentine. Clinically, the rose-head burr showed significantly better excavation results then Carisolv (Dammaschke et al. 2001a); however, the excavator did not. Histologically, significant differences between the types of excavation could not be demonstrated. Excavation results using Carisolv are similar, but with clearly more time needed for excavation. Splieth et al. (1999) achieved similar results in a comparative study of the effectiveness of chemo-mechanical caries removal compared to conventional excavation.
Excavation at the dentino-enamel junction (DEJ)
Insufficient excavation at the dentino-enamel junction (DEJ) seems to be a problem in chemo-mechanical caries removal. Cederlund et al. (1999) were able to prove in their in-vitro study the absence of caries at the dentinal surface following use of Carisolv; however, in 60 % of the cases, residual caries was observed in the area of adjacent dentine. In a biochemical analysis of the dentine remaining following in-vitro excavation using Carisolv, high quantities of denaturated collagen were found which leads to the conclusion that the caries could not be removed completely with Carisolv.
In an initial comparative in-vivo examination comparing effectiveness of Carisolv in its original and amended formulations, Fure and Lingström (2004) did not observe a significant difference of excavation times needed. Only lesions close to the pulp required less time for excavation when the new gel was used.
Since the concentration of amino acids was reduced to half and that of sodium hypochlorite doubled to enhance effectiveness of the new Carisolv, the alkaline sodium hypochlorite is the main component of Carisolv. The question arises as to whether the use of a very alkaline solution of sodium hypochlorite in the form of a gel, or of alkaline calcium hydroxide that is also frequently used in dental medicine, would achieve similar results in chemo-mechanical caries removal. However, in an in-vitro study, Carisolv achieved significantly better excavation results than use of NaOCl or Ca(OH)2 alone (Dammaschke et al. 2005).
Negative effects of Carisolv in its original or amended composition on the pulp or on healthy dentine not affected by caries could not be proved. Excavation using Carisolv that is 'automatically' sufficient is not to be expected. Clearly prolonged excavation times must be expected if Carisolv is used.
For visual assessment of the possible absence of caries, always bear in mind that, other than when a rose-head burr and excavator have been used, the dentinal surface will always have a matt appearance and feel rough.
Pulsed ruby lasers were the first lasers used for manipulation of dental hard substance in the mid-1960ies (Goldmann et al. 1964). The relatively long pulse of the laser beam of up to a few microseconds can lead to serious thermal side effects in the dental hard substance.
Nowadays, three options of substance removal in hard tissue using lasers are differentiated:
- excimer lasers work in the ultra-violet range (wave length of 193 nm - 348 nm); they stimulate molecules and destroy them.
- Er:YAG lasers (wave length of 2.94 µm) are in the absorption range of water - they heat H2O molecules in enamel or dentine. The sudden heating results in the evaporation of the water leading to destruction of hard tissue. Therefore, use of the Er:YAG laser does not result in melting or evaporation of crystalline hard tissue but leads to thermo-induced micro-explosions.
- Due to the development of heat, use of the CO2 laser (wave length of 9.6 µm - 10.6 µm) leads to evaporation of tissue through carbonisation).
At present, erbium lasers (Er:YAG, Er:YSGG) are the only devices available for caries removal in the practice.
The energy threshold of carious tissue is only little lower than that of healthy dental hard substance; therefore, Er:YAG lasers are able to remove caries but selective selective removal of dentine affected by caries without any damage to healthy tissue is not possible.
However, carious surfaces can be sterilised by laser irradiation; the bactericidal effect reaches to a depth of up to 0.4 mm.
The reaction of the pulp following manipulation using lasers in deep cavities was shown to be reversible. Irritation dentine develops as a response after approx. two weeks. Keller et al. (1991, 1992) were able to determine initial signs of pulp reaction when they used the Er:YAG laser in dogs on dentine close to the pulp.
However, this does not seem to be due to the temperature increase but to mechanical irritation through compression waves resulting from the special ablation process of the Er:YAG lasers. De-focussed use of CO2 lasers with low energy density results in carbonisation of the dentine with reversible pulp damage. Use of other lasers, such as focussed CO2 or Er:YAG lasersmay lead to pulp necrosis due to the high temperature increase. A possible genetic damage in affected nuclei is discussed with regard to the use of excimer lasers due to their effect within the ultraviolet range. It is also not possible to remove sufficient dental hard substance with this system.
Another disadvantage of any laser system is that, due to the vertical exit of the laser beam from the handpiece, it is not possible to remove caries in undercut areas.
Lasers are also not recommended for cavity preparation because they do not efficiently remove larger quantities of enamel and dentine because of the distance. Furthermore, this process would cause an intolerable increase in temperature. Therefore, lasers will never replace high-speed angle handpieces.
Lasers can be differentiated not only by their different wavelengths but also by the pulse length of their beam. While the pulse length of the first lasers for use in dental medicine was a few microseconds, recent research has used femtosecond lasers. (one microsecond (µs) is equivalent to a millionth part of a second. 1 µs =1 x 10-6 s. A microsecond (1 µs) is the time required by light to travel a distance of 299.79 m. A femtosecond (fs) is one quadrillionth of a second. 1 fs =1 x 10-15 s. A femtosecond (1 fs) is the time required by light to travel a distance of 0.3 µm.) If lasers with their wavelength of 780 nm (transition from the visible red colour to the infrared range) and their pulse length of 700 fs are a real alternative for the manipulation of dental hard tissue and excavation of dentine caries remains to be seen. Initial electron-microscopic examinations of dentine manipulated using this laser type are fairly promising. To date, there are no comparative scientific studies.
Advantages of the laser:
- absence of mechanical irritation and vibration;
- disinfection of the dentine wound.
Disadvantages of the laser:
- increased temperature,
- dubious excavation of caries,
- limited possibility to excavate caries from undercuts,
- tactile loss,
- absence of a defined edge of cavity preparation,
- purchase is expensive.
Ozone consists of three oxygen atoms (O3) and is strongly disinfecting. In nature, ozone forms from oxygen molecules (O2) that are irradiated with UV light, amongst other things, resulting in an activated, though unstable form of oxygen that quickly decomposes. Therefore, ozone has strongly oxidising properties, and higher concentrations have a toxic effect because they cause damage to cell membranes.
Initial descriptions of use in dental medicine were reported in the 1930s; in the middle of the past century, Dechaume (1952) reported caries treatment using ozone.
Since 2003, KaVo (Biberach) have been marketing their HealOzone device in Germany. It produces ozone that can be applied via a handpiece to the tooth surface.
The vent on top of the handpiece is surrounded by a rubber cap. The rubber-capped vent of the handpiece is placed on the tooth and ozone is applied for a few seconds. The rubber cap serves as a kind of suction device surrounding the tooth in order to prevent escape of ozone into the oral cavity; instead, it re-enters the instrument by suction. Ozone is released only if the suction device closes tight and the HealOzone device induces a vacuum and negative pressure on the site to be treated. The duration of release of ozone from the device is 10 seconds or 20 seconds, respectively, thus killing almost all bacteria present in the area of the device's exit. The aim is to bring development of carious lesions to a standstill so that the dentine is able to remineralise.
Hence, HealOzone does not follow the classical approach of drilling (caries removal) and filling. Dental hard tissue affected by caries is disinfected and a filling hopefully avoided.
In the literature, some in-vitro and in-vivo studies for the treatment of carious root surfaces have been described where disinfection of the dental hard tissue using ozone is evident (Baysan et al. 2000, Baysan and Lynch 2004).
However, an evidence-based meta-analysis by Rickard et al. (2004) did not prove that ozone was able to influence the progress of caries. To date there is no evidence that the application of ozone to the dental surface stops caries or even induces re-mineralisation. The optimal ozone concentration during treatment is not known, nor are the ideal duration of application, how long the disinfecting effect of ozone will last, how deep it penetrates the lesion, or possible side effects of ozone. HealOzone should not be used for the treatment of carious lesions until thorough and robust studies have been conducted to prove scientifically a long-term effect of ozone on the surface of the tooth.
The classical rose-head burr will certainly continue to be used for some time as the standard instrument for the removal of carious dentine.
Innovative technology, such as air-abrasion or sono-abrasion devices, lasers or HealOzone will probably have problems finding their way into dental practice in the near future, if only for the high purchasing costs and subsequent costs arising for treatment.
The mere selection of materials for the manufacture of self-limiting instruments that are harder than carious dentine but softer than healthy one is an interesting idea. Unfortunately, SmartPrep has not yet been found to remove sufficient quantities of caries in the scientific investigations conducted so far.
An interesting novelty enabling sufficient caries excavation is Carisolv gel. But again, its disadvantages are the increased costs of the material and prolonged times required for excavation.
Classical excavators should be used in areas close to the pulp because of their substance-sparing properties.
There are still no real alternatives to excavators or rose-head burrs suitable for use in the dental practice for the treatment of dentine caries.
- Baysan A, Lynch E (2004) Effect of ozone on the oral microbiota and clinical severity of primary root caries Am J dent 17, 56 60 (2004).
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