Pinheiro, Borges, Lima DISCUSSION as fluoride and strontium, released from the GIC. The hypothesis tested in this study was vali- For remineralization to be effective, the freshly dated. Results obtained showed that the tradi- mixed GIC must be closely adapted to the caries- tional amalgam filling protocol is effective, since affected dentin. This allows the relatively high no secondary caries was observed by clinical and initial release of fluoride and other ions from the radiograph criteria, besides a progressive remin- cement to augment physiological remineraliza- eralization in dentin was detected by DIAGNOdent tion and the relatively low initial pH to reduce the readings after the 12-month follow-up period. numbers and viability of the cariogenic microor- DIAGNOdent is a laser fluorescence device able ganisms present.9 Although the infected dentin to capture the fluorescence emitted from dental was manually removed during cavity preparation, tissues when teeth are stimulated by its diode la- a certain amount of bacteria still remain.26 The ser with a wavelength of 655 nm.21 The tooth sur- fluoride release by GIC,27 in addition to maintain- face is illuminated by a red light (modulated exci- ing a seal at the cavosurface restoration margin, tation wavelength at 655 nm), which is produced by could inhibit residual bacteria proliferation,2 and a laser diode and transmitted by an optical fiber. prevent secondary caries. Since indirect pulp cap- The laser induces fluorescence in the mineralized ping was placed on the cavity floor of middle-third tooth tissues, at a greater intensity in carious than cavities in this investigation, GIC was not able to in sound tooth tissues, which is then transmitted stimulate the pulp to produce a mineral barrier af- by an optical fiber to a photodiode with a long pass ter the 12-month follow-up, which would increase filter (wavelength >680 nm) in the detection device, the distance between pulp and GIC. so that changes in the fluorescence intensity are Although in vitro studies16,17 have shown in- numerically quantified and translated to values creased microleakage in amalgam restorations ranging from 0 to 99.22 Since the scores emitted by under cavity varnish due to dissolution of the var- DIAGNOdent showed a decrease at the 12-month nish before the formation of corrosion products, evaluation, dentin remineralization occurred. this in vivo investigation demonstrated that the Dentin color and DIAGNOdent scores were as- clinical relevance of laboratory studies is ques- sessed to avoid influences from possible amalgam tionable. Results of the present study with regard staining not visually perceived in cavity walls. Al- to secondary caries probably indicate the ability of though clinicians have correlated dentin darken- corrosion products to form at the interface between ing with its high mineral content, in this study no tooth and restoration, which could help to protect correlation was shown between dentinal colors it against penetration of oral fluids and cariogenic and DIAGNOdent scores, and no statistically sig- microorganisms. It is important to highlight that nificant darkening was shown after 12-months of admixed alloys produce corrosion products faster observation. This finding presupposes that dentin than unicompositional alloys.28 Since the Velvalloy color may not depend only on the mineral content, amalgam used in this study is an admixed alloy, but also on other variables, such intrinsic charac- corrosion products were probably produced before teristics of collagen fibrils and staining substanc- varnish dissolution. es released from microorganisms. However, fur- Adhesive dentistry has focused on improve- ther researches are needed to confirm this theory. ments of composite resins and adhesive systems, Remineralization and even hypermineralization since composite restoration have become popular of demineralized dentin has been demonstrated because of their esthetic appeal.29 Nevertheless, by various GICs in vitro23 and in situ.24 High concen- amalgam is still extensively used worldwide,30 trations of fluoride and strontium ions have been mainly in public health care services which at- found in dentin beneath GIC.9 Mineral re-deposi- tend low-income, high caries risk patients. In the tion into demineralized dentin lesions has exhibit- actual dentistry, the minimally invasive dentistry ed higher resistance to the second acid challenge, approach has gained great attention worldwide.31 for example, restoration leakage and recurrent Therefore, this in vivo study showed that conven- caries attack.25 Thus, the increase in mineral con- tional tooth restorations with amalgam preparing tent achieved in dentin after the 12-month obser- the cavity by a minimal tissue removal can be ef- vation period was possibly composed of ions, such fectively made. July 2012 - Vol.6 267 European Journal of Dentistry