Evaluación de un método químico-mecánico de remoción de dentina cariada - estudios clínico y de laboratorio

Resumen

Nowadays, in view of the new concepts on the pathogenesis and progression of dental caries (Featherstone 2004), we are living a transition period oriented towards prevention and early diagnosis, minimally invasive treatment, aesthetics and the well-being of the patient (Ericson D 2003). As a result of these factors and of the new materials and adhesive techniques, the preparation is more conservative (Ericson D 2004), and the same happens with the techniques used. Nevertheless, from a patient's perspective, dental treatment does not have a good reputation (Noack MJ 2004). Conventional removal of caries lesions involves the use of a bur with a high-speed air-turbine handpiece to access the lesion and a low-speed contra-angled handpiece for carious dentin removal. The general opinion is that this technique can only be perceived as unpleasant and painful by many patients, and there is frequently the need for local anesthesia to manage pain. On the other hand, since Fusayama's investigations in the 1970s, there is a distinction between 2 different layers of carious dentin presenting specific characteristics: an outer layer (infected, non-remineralizable, non-vital) and an inner layer of carious dentin (Ohgushi K 1975; Fusayama T 1979). Several studies have shown that using conventional methods for carious tissue removal and diagnosis of carious dentin, there is the risk of excessive removal of sound dental structure (Kidd EAM 2004) associated with an increased risk of pulp exposure (Björndal L 2002; Noack MJ 2004) or, in alternative, leaving residual carious tissue (Anderson MH 1985; Anderson MH 1985; Kidd EAM 1989) and possibly compromising the longevity of the restorations or treated teeth (Mjör IA 1989) (Mjör IA 2000b) (Hickel R 2001). Chemo-mechanical removal of dentin has recently been revolutionized by the introduction of a new substance (CarisolvTM - MediTeam, Sweden) that had its in vitro and in vivo efficacy and safety demonstrated in scientific literature (Ericson D 1998) (Ericson D 1999) (Arvidsson A 2001) (Wennerberg A 2001) (Young C 2001b) (Fure S 2004) (Bergmann J 2005) (Lozano-Chourio MA 2006). In the majority of the cases there is no need for local anesthesia, thus lowering the patient's discomfort (Burke FJT 1999; Ericson D 1999) (Haffner C 1999; Fure S 2000; Munshi AK 2001; Nadanovsky P 2001; Maragakis GM 2001a; Ansari G 2003; Chaussain-Miller C 2003; Kakaboura A 2003; Fure S 2004; Kavvadia K 2004; Bergmann J 2005; Wang J 2005; Wang J 2005; Hamidinia F 2006; Lozano-Chourio MA 2006). In current literature, very few clinical studies assessed the efficacy and safety of the CarisolvTM system in prospective studies over one year (Fure S 2000; Nevrin K 2000; Zimmerman M 2000; Barata TJE 2003; Arceguet G 2004; Fure S 2004). In this investigation, a prospective, randomized controlled, open study was performed at the Department of Restorative Dentistry of the Instituto Superior de Ciências da Saúde - Egas Moniz. The objectives were the evaluation of the safety and efficacy of the CarisolvTM method for chemo-mechanical removal of coronal caries comparatively to the conventional rotary instruments as well as the patient's comparative acceptance and opinion concerning the two techniques. Patients were observed at the one-year follow-up appointment to evaluate the presence of eventual adverse effects. It was concluded from this clinical study that the benefits of CarisolvTM initial formulation are more of great value both in terms of efficacy and safety when used as an alternative or as a complement to drilling. No side effects related to the use of CarisolvTM have been demonstrated during the treatment time or after one-year at the follow-up visit. All the patients responded positively to the treatment, considering it pleasant or acceptable. Nevertheless, time consumption is significantly higher when compared with the conventional rotary excavation method. The current formulation of CarisolvTM (MediTeam Dental AB, actual Orasolv AB - Göteborg, Sweden) was approved by the FDA. It is colorless, contains half the concentration in amino acids, and almost double the quantity of sodium hypochloride when compared with the original formulation (0.475% active chlorine after mixture with the amino acid solution) (MediTeam Dental; Fure S 2004). In an era dominated by the adhesive technique as the main method used in minimally invasive medical procedures, it seems imperative to clarify the effects of this new CarisolvTM formulation containing a higher concentration of sodium hypochloride (MediTeam Dental; Fure S 2004) on the dentin structure, as well as the effects of its conjugation with new adhesive systems currently commercially available. At the moment there is little knowledge on resin adherence to sound dentin treated with CarisolvTM, and no information on the adhesive difference between affected dentin and sound dentin following the application of the chemo-mechanical technique (Erhardt MCG 2004). Furthermore, the evaluation of its effect on sound dentin would provide a base on which to improve our knowledge of its effects during the treatment of caries lesions (Hosoya Y 2005). On the other hand, laboratory studies and clinical trials on the effect of CarisolvTM on adhesion mechanisms, and especially its interference with recent self-etching materials are still incipient. In order to develop these issues, we are conducing a microstuctural laboratorial study to evaluate the effects of the new CarisolvTM formulation on the dentin surface characteristics using a Scanning Electron Microscope (SEM). Alteration of dentinal tubules exposure and smear-layer thickness has been observed. Other testing were performed to evaluate the effects of the CarisolvTM new formulation on dentin adhesion of etch and rinse conventional adhesive systems and of self-etch new systems, 15analyzing the bond strengths and their fracture mode, as well as the dentin/adhesive system interface ultra-morphology. The selected self-etch material was self-etching primer ClearfilTM SE Bond (Kuraray Europe GMBH, Düsseldorf, Germany) and the etch and rinse system chosen as control was a simplified system in two steps, in order to minimize variability: AdperTM ScotchbondTM1 XT (3M ESPE AG Dental Products, Seefeld - Germany). Z100 (3M ESPE AG Dental Products, Seefeld - Germany) was the composite resin applied in all techniques. For the shear-bond strength evaluation a system developed at the University of California, San Francisco was used: The Single-Plane Shear Test Assembly (SPSTA). (Watanabe LG 2000). For aging simulation, the samples were stored for a period of 6 months and 12 months in a chloramine solution at 0.04% strength in PBS (phosphate buffered saline) at a pH value of 7.4, and incubated at 37ºC. The storage aging effects on adhesion were evaluated through shear bond strength testing and fracture modes were observed, in addition to a dentin / adhesive system interface ultra-morphology study with observation of hybrid layer characteristics. Vickers hardness analysis was used in the study of the dentin mechanical properties as well as energydispersive analysis of X-ray (for the study of dentin composition modification). From a microstructural point of view, CarisolvTM apparently induces differences between diseased and sound dentin. However, after conditioning, the diseased dentin showed a thinner smear-layer when compared with the same values before conditioning. Conditioning with the self-etch primer exposed more tubules when compared with phosphoric acid conditioning. Regarding dentin adhesion, pre-treatment with CarisolvTM did not significantly affect shear bond strength. The etch and rinse adhesive system showed mean shear bond strength values (MPa) significantly higher than those from the self-etching primer adhesive system. The hybrid layer thickness seemed to follow the same behavior as the shear bond strength values, was unaffected by the use of CarisolvTM, and showed a tendency towards higher values with the etch and rinse adhesive system. The aging of the samples in a chloramine solution at 0.04% strength in PBS had a significant effect on adherence at 6 and 12 months, showing a decrease in bond strength and microstructural changes compatible with a loss of efficient resin / dentin adhesion as well as microhardness and Ca/P ratio in dentin at 6 and 12 months. With all its medical advantages, and in spite of not having a significant effect on the adhesion of etch and rinse or self-etch primer type adhesives according to this study, chemo-mechanical removal of dentin using CarisolvTM (MediTeam, Sweden) can sometimes be considered as an alternative technique, other times as complementary technique, but the continuous development in dental adhesive technology creates the need to continue with these long term laboratory studies and clinical trials, in order to perform medical procedures based on updated scientific evidence.