[Scanning electron microscopy analysis of marginal adaptation of composite resines to enamel after using of standard and gradual photopolimerization].

INTRODUCTION: Bonding between composite and hard dental tissue is most commonly assessed by measuring bonding strength or absence of marginal gap along the restoration interface. Marginal index (MI) is a significant indicator of the efficiency of the bond between material and dental tissue because it also shows the values of width and length of marginal gap. OBJECTIVE: The aim of this investigation was to estimate quantitative and qualitative features of the bond between composite resin and enamel and to determine the values of MI in enamel after application of two techniques of photopolymerization with two composite systems. METHODS: Forty Class V cavities on extracted teeth were prepared and restored for scanning electron microscope (SEM) analysis of composite bonding to enamel. Adhesion to enamel was achieved by Adper Single Bond 2 - ASB (3M ESPE), or by Adper Easy One--AEO (3M ESPE). Photopolymerization of Filtek Ultimate--FU (3M ESPE) was performed using constant halogen light (HIP) or soft start program (SOF). RESULTS: Quantitative and qualitative analysis, showed better mikromorphological bonding with SOF photopolymerization and ASB/FU composite system. Differences in MI between different photopolymerization techniques (HIP: 0.6707; SOF: 0.2395) were statistically significant (p < 0.001), as well as differences between the composite systems (ASB/FU: 0.0470; AEO/ FU: 0.8651) (p < 0.001) by two-way ANOVA test. CONCLUSION: Better marginal adaptation of composite to enamel was obtained with SOF photopolymerization in both composite systems.

[The investigation of ultrasound efficacy in cleaning the surface of new endodontic instruments]. / Ispitivanje efikasnosti ultrazvuka y ciscenju povrsina novih endodontskih instrumenata.

INTRODUCTION: Active parts and tips of various new stainless steel and nickel-titanium endodontic instruments can be coated with fragments or metal residues, which can become detached during endodontic treatment. These fragments may obstruct the root canals or even reach the periapical tissue during biomechanical preparation and should be removed before clinical use. OBJECTIVE: The aim of this study was to evaluate the presence of metal residues on both new stainless steel and nickel-titanium endodontic instruments, and to determine the cleaning efficacy of ultrasound using distilled water or disinfectant solution for removing these residues. METHODS: Forty-eight stainless steel and nickel-titanium instruments were carefully removed from their original packages with dental tweezers, in order to avoid any contact with the cutting flutes and tips. The instruments were evaluated in term of metal debris presence, using scanning electron microscopy (SEM) and x-ray energy-dispersive spectroscopy (EDS). The instruments were then removed from the electron microscopy analysis stubs and placed in an ultrasonic bath for 15 minutes at a frequency of 28 kHz, using distilled water or disinfectant solution. The surfaces of the instruments were re-evaluated after cleaning. RESULTS: Before ultrasound cleaning, a larger amount of metal debris was observed on the nickel-titanium endodontic instruments when compared to those made of stainless steel. The presence of metal particles on the instruments was evaluated by using EDS analysis. The use of ultrasound was effective in removing the metal residues from both types of endodontic instrument surfaces. CONCLUSION: The use of ultrasound proved to be an efficient method for the removal of metal particles from the surface of new stainless steel and nickel-titanium endodontic instruments.

[SEM investigation of composite restoration adaptation to enamel after use of total etch and self etch adhesive system].

INTRODUCTION: Quality and durability of enamel/composite interface essentially depend on an adhesive restorative system. OBJECTIVE: The aim of this study was to evaluate the quality of marginal adaptation of composite adhesive systems to enamel by scanning electron microscopy (SEM), and to analyse the morphology of the enamel surface along margins of composite restorations, following exposure to cariogenic solution. METHODS: The study material included 56 extracted human third molars. Class V cavities were prepared with margins at enamel. Cavities were restored with Single Bond/Z250 and Single Bond/Filtek flow, using the total etch adhesive system, and Prompt-L-Pop/Z250 and Prompt-L-Pop/Filtek flow, using the self etch adhesive system. After the restorative procedure, the restorations were submitted to demineralization during 7 and 28 days. Samples were stored in a cariogenic solution (lactic acid, pH 4.5; 0.1 M) at 37 degrees C or in deionized water (the control group). The margins of restorations and perimarginal enamel were examined by scanning electron microscope (SEM). The gap formations around restoration were measured on cervical, occlusal and approximate margins. RESULTS: The usage of the total etch adhesive system showed statistically significant lower marginal gap width around composite restoration, compared with the self etch system (p < 0.01). The SEM examination also showed perimarginal enamel zones presenting several signs of demineralization and erosion (alteration of rods, porosities) after acting of a cariogenic solution, in both adhesive methods. Less alteration was found on the enamel surfaces not included in the perimarginal zone. CONCLUSION: Treating the cavity with 35% phosphoric acid in the total etch system significantly improved the adaptation of the composite resins to enamel, compared with the self etch treatment. Stronger demineralization of the perimarginal enamel in a cariogenic solution was observed around all restorations in both adhesive systems.

[The resistence of conditioned enamel to the effect of cariogenic solution].

INTRODUCTION: Enamel surface around restoration is very sensitive to the effect of cariogenic solution. It is the consequence of the manner the cavity is prepared before restoration, the existence of marginal cracks around restoration, that is, irregular polishing of filling. OBJECTIVE: The aim of this study is to analyze the morphology of the marginal enamel surface around composite fifth class restoration after the application of cariogenic solution. METHOD: In this study 28 extracted molars were used. After the V class preparation of the buccal crown surface, teeth samples were divided into two groups. The first group was restored with the composite system Single Bond +Z250, applying the total etching technique. The second group was restorated with Prompt L-pop +Z250 and by applying self-etching primers. After the cavity restoration, teeth samples were kept in demineralising solution (lactic acid, pH 4.5, 0.1 M) at the temperature of 37 degrees C during 7 and 28 days. Control group samples were kept in distilled water during the experiment. The marginal enamel surface analysis was done by a scanning electron microscope. RESULTS: The achieved results showed that there was a denivelation and severe demineralization of the perimarginal enamel zone after 7 and 28 days, while on the remaining enamel there were some minor changes. Along the marginal composite/enamel joint there was the central type of demineralization of enamel prisms and preserved inter prismatic enamel.The existence of pores of different sizes and scattered enamel fractures was established. The marginal joint was mostly without any gaps in the first group samples, while in the second group samples there were narrow or wider edge gaps. CONCLUSION: After the application ofcariogenic solution, perimarrginal enamel showed conspicuous morphological damage in comparison to the remaining enamel surface.