PubMed · 6100326
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E Dorigo, M Pariatti. [Acid etching: special aspects].. https://pubmed.ncbi.nlm.nih.gov/6100326/
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The most popular techniques for determining the quality of the hybrid layer (HL) have relied on morphologic characterization of the polished adhesive/dentin (a/d) interfaces before and after acid-bleach chemical treatment. Using these techniques, the existence of smooth, acid-resistant layers has been consistently reported for most adhesive systems. The purpose of this study was to determine whether popular specimen preparation techniques that include polishing and acid-bleach treatment modify the a/d interface, mask the complexity of the HL, and lead to inaccurate assessment of the quality of the HL. To understand the impact of specimen preparation techniques on the morphology of the resin-dentin interface, polished and unpolished specimens from the same tooth were closely compared after different acid-bleach chemical treatment procedures. Two one-bottle adhesives, that is, 3M Single Bond and Pulpdent UNO, exhibiting distinct differences in hydrophilic/hydrophobic composition, were used in this investigation. Using specimens from the same tooth, the effect of chemical treatments on the morphology of the resin-dentin interdiffusion zone and the differences in the morphology of polished and unpolished specimens after these same treatments were studied with scanning electron microscopy. It was shown that conventional specimen preparation techniques that include polishing and acid-bleach treatment can adversely affect and even obscure the structural detail of the a/d interface in specimens that possess a porous HL. The results indicated that the Pulpdent UNO/dentin interface had better quality than the 3M Single Bond/dentin interface. The difference in the quality of HL can be attributed to factors such as compositional differences that impact the adhesive interaction with water, that is present within the substrate during wet bonding. The inability of the conventional acid-bleach procedure to reveal the differences in the scanning electron microscopy interfacial morphology was overcome in this investigation by using a multistep technique.
OBJECTIVES: To examine the effects of an experimental bonding technique that reduces the permeability of the adhesive layer on the coupling of resin cements to dentine. METHODS: Extracted human third molars had their mid to deep dentin surface exposed flat by transversally sectioning the crowns. Resin composite overlays were constructed and cemented to the surfaces using either Panavia F (Kuraray) or Bistite II DC (Tokuyama) resin cements mediated by their respective one-step or two-step self-etch adhesives. Experimental groups were prepared in the same way, except that the additional layer of a low-viscosity bonding resin (LVBR, Scotchbond Multi-Purpose Plus, 3M ESPE) was placed on the bonded dentine surface before luting the overlays with the respective resin cements. The bonded assemblies were stored for 24 h in water at 37 degrees C and subsequently prepared for microtensile bond strength testing. Beams of approximately 0.8 mm(2) were tested in tension at 0.5 mm/min in a universal tester. Fractured surfaces were examined under scanning electron microscopy (SEM). Additional specimens were prepared and examined with TEM using a silver nitrate-staining technique. RESULTS: Two-way ANOVA showed significant interactions between materials and bonding protocols (p<0.05). When bonded according to manufacturer's directions, Panavia F produced bond strengths that were significantly lower than Bistite II DC (p<0.05). The placement of an additional layer of a LVBR improved significantly the bond strengths of Panavia F (p<0.05), but not of Bistite II DC (p>0.05). SEM observation of the fractured surfaces in Panavia F showed rosette-like features that were exclusive for specimens bonded according to manufacturer's directions. Such features corresponded well with the ultrastructure of the interfaces that showed more nanoleakage associated with the more permeable adhesive interface. The application of the additional layer of the LVBR reduced the amount of silver impregnation for both adhesives suggesting that reduced permeability of the adhesives resulted in improved coupling of the resin cements to dentin. CONCLUSIONS: Placement of an intermediate layer of a LVBR between the bonded dentine surface and the resin cements resulted in improved coupling of Panavia F to dentine.
OBJECTIVES: This study evaluated the microleakage and internal seal of fissure sealants placed by use of self-etching priming agents in comparison to phosphoric acid etching of enamel. METHODS: Seventy-two caries-free extracted human molars were divided into six groups with 12 teeth each. Occlusal surfaces were cleansed by either pumicing (Groups I, III, V) or by 15-s air-abrasion treatment with 25 microm aluminum oxide particles (Groups II, IV, VI). Fissures were sealed with the self-etching priming systems, Clearfil Liner Bond 2 (Groups I, II) or Resulcin AquaPrime (Groups III, IV). In Groups V and VI, sealants were placed after phosphoric acid etching. Half of the teeth in each group were thermocycled. After staining with 0.5% methylene blue, the teeth were sectioned for evaluation of microleakage. Internal adaptation of the fissure sealants was analyzed by SEM on replicas of cross sections. RESULTS: Independent of the methods used for cleansing of the occlusal surfaces, fissure sealants in Groups I and II showed significantly more microleakage and less sufficient internal seal as compared to sealants placed in Groups III to VI. Sealants placed by Resulcin AquaPrime (Groups III, IV) leaked significantly more than sealants applied after phosphoric acid etching (Groups V, VI) of the enamel. However, statistical analysis (H-test) did not reveal significant differences concerning the internal adaptation of sealants placed in Groups III, IV, V and VI. CONCLUSIONS: Concerning the microleakage data, use of the self-etching bonding systems, Clearfil Liner Bond 2 and Resulcin AquaPrime, cannot be recommended for fissure sealing, since the sealing ability is less effective as compared to the conventional acid-etching technique.