Bruna Marin Fronza

Monomer conversion, microhardness, internal marginal adaptation, and shrinkage stress of bulk-fill resin composites

OBJECTIVE To evaluate degree of conversion (DC), Knoop microhardness (KHN), internal marginal adaptation (IA), and polymerization shrinkage stress (PS) of one conventional and four bulk-fill composites. METHODS Bulk-fill composites tested were Surefil SDR (SDR), Filtek Bulk-Fill (FBF), Tetric EvoCeram Bulk-Fill (TEC), and EverX Posterior (EXP). The conventional composite Herculite Classic (HER) was tested using both incremental and bulk-fill insertion techniques. Standardized Class I preparations (4-mm-depth) were made in extracted molars and restored with each product system (N=5). After 1-week wet storage, restorations were cross-sectioned and DC and KHN were evaluated at four depths (1, 2, 3, and 4mm) using confocal Raman spectroscopy and KHN techniques, respectively. Epoxy resin replicas of restorations were evaluated using scanning electron microscopy for IA. PS was determined using composite bonded to acrylic rods attached to a universal testing machine (N=5). RESULTS Within bulk-fill products, only SDR and FBF demonstrated similar DC at all depths, and KHN values did not statistically differ among depths, except for TEC. Neither placement method nor depth affected KHN or DC, except the DC of HER bulk-fill at 4mm. Incrementally layered HER, and bulk-fills SDR and TEC demonstrated the lowest proportion of internal gaps. Highest and lowest PS values were measured for EXP and TEC, respectively. SIGNIFICANCE DC with depth was not uniform among all bulk-fill materials, although no difference in KHN was found. Higher PS correlated positively with higher proportion of interfacial gaps. The incremental technique using conventional composite showed reduced gap formation.

Self-Etch Adhesive Systems: A Literature Review

This paper presents the state of the art of self-etch adhesive systems. Four topics are shown in this review and included: the historic of this category of bonding agents, bonding mechanism, characteristics/properties and the formation of acid-base resistant zone at enamel/dentin-adhesive interfaces. Also, advantages regarding etch-and-rinse systems and classifications of self-etch adhesive systems according to the number of steps and acidity are addressed. Finally, issues like the potential durability and clinical importance are discussed. Self-etch adhesive systems are promising materials because they are easy to use, bond chemically to tooth structure and maintain the dentin hydroxyapatite, which is important for the durability of the bonding.

Evaluation of bulk-fill systems: microtensile bond strength and non-destructive imaging of marginal adaptation.

The objective of this study was to investigate microtensile bond strength (MTBS) and interfacial adaptation (IA) of bulk-fill restorative systems bonded to dentin in Class-I-preparations. Box-shaped preparations (4-mm-long, 3-mm-wide, 2-mm-high) made in extracted molars, and Teflon matrix with the same dimensions positioned over the occlusal surface were restored, providing a total of 4-mm composite depth using three bulk-fill restorative systems: Tetric EvoCeram Bulk Fill with Tetric N-Bond (TEC/TNB), SureFil SDR Flow with XP Bond (SDR/XPB) and Filtek Bulk Fill Flowable Restorative with Scotchbond Universal (FBF/SBU); or incrementally restored with a conventional restorative system: Herculite Classic with OptiBond FL (HER/OBF). The specimens were sectioned into beams and the MTBS measured after 24-hours or one-year storage. For evaluation of IA, round-tapered tooth preparations (3-mm-diameter, 1.5-mm-deep) were made, restored with each material and their cross-sectional images were obtained after 24-hours using optical coherence tomography (OCT). The gap percentage for each restoration system was calculated using image analysis software. MTBS for both storage periods: HER/OBF=TEC/TNB=SDR/XPB>FBF/SBU (ANOVA, Tukeys post-hoc, P<0.05) differed significantly among groups, which values were significantly reduced after one-year. SDR/XPB showed comparatively lesser gap formation at the tooth-interface after 24 hours (ANOVA, Dunnetts T3 post-hoc, P<0.05). For deeper restorations, bond strength of TEC/TNB and SDR/XPB can be equal to that of HER/OBF after 24-hours and one-year; however, in a shallower preparation, SDR/XPB showed greater initial interfacial adaptation.

Modulation of Streptococcus mutans virulence by dental adhesives containing anti-caries agents

OBJECTIVES The aim of this in vitro study was to analyze the effect of the incorporation of two anti-caries agents into dental adhesives on the reduction of the virulence of Streptococcus mutans and on the adhesion to dentin. METHODS Apigenin (1mM) and tt-Farnesol (5mM) were added separately and in combination to a self-etch adhesive (CS3 - Clearfil S3 Bond Plus) and to an each-and-rinse adhesive (OPT - OptiBond S). Biofilm of S. mutans was grown on adhesive-coated hydroxyapatite disks for 115h and bacterial viability, dry-weight, alkali soluble, water soluble, intracellular polysaccharides and protein were quantified. Bond strength and dentin-adhesive interface were performed to analyze the effects of the incorporation on the physical properties and to identify changes in hybrid layer morphology. RESULTS Addition of Apigenin and Apigenin+tt-Farnesol to CS3, and Apigenin or tt-Farnesol to OPT reduced the dry-weight of S. mutans biofilm. Insoluble polysaccharide decreased with the addition of Apigenin to CS3 and tt-Farnesol to OPT. Intracellular polysaccharide decreased with addition of Apigenin and Apigenin+tt-Farnesol to CS3. No changes in dentin bond strength, resin-dentin interfacial morphology, total amount of protein and soluble polysaccharide were observed with the additions. SIGNIFICANCE Biofilms that are less cariogenic around dental restorations could decrease secondary caries formation; in addition, the reduction of virulence of S. mutans without necessarily killing the microorganism is more unlikely to induce antimicrobial resistance.