Fracture behavior of short fiber-reinforced CAD/CAM inlay restorations after cyclic fatigue aging.

The aim of this study was to assess the fracture behavior of molar teeth restored with MOD inlays made of experimental short fiber-reinforced CAD/CAM composite block (SFRC CAD) before and after cyclic fatigue aging. Standardized MOD cavities were prepared on 60 intact mandibular molars. Three groups of CAD/CAM made inlay restorations (Cerasmart 270, Enamic, and SFRC CAD) were fabricated (n = 20/group). All restorations were luted with self-adhesive dual-cure resin cement (G-Cem One). Half of restored teeth per each group (n = 10) were quasi-statically loaded until fracture without aging. The other half underwent cyclic fatigue aging for 500,000 cycles (Fmax = 150 N) before being loaded quasi-statically until fracture. Then, the fracture type was visually inspected. The microstructure and elemental content of CAD/CAM materials were assessed using SEM and EDS. Two-way analysis of variance (ANOVA) was used to statistically examine the data, and it was followed by the Tukey HSD test (α = 0.05). ANOVA demonstrated that both material type and aging had a significant effect (p < 0.05) on the load-bearing capacity values of the restorations. Teeth restored with SFRC CAD showed significantly the highest (p < 0.05) load-bearing capacity (2535 ± 830 N) after fatigue aging among all groups. SEM images showed the ability of short fibers in SFRC CAD composite to redirect and hinder crack propagation. With regard to fracture mode, Enamic group revealed 85% of catastrophic failure (vs. 45% and 10% for Cerasmart 270 and SFRC CAD, respectively). Large MOD cavities on molar teeth were most favorably restored with SFRC CAD inlays, yielding the highest load-bearing capacity and more restorable failures.

A comparative assessment of color stability among various commercial resin composites.

OBJECTIVES: The aim was to evaluate the color stability of six commercial restorative resin composites after being exposed to commonly consumed beverages. Repolishing impact on the stained composite was also assessed. METHODS: One-hundred and fifty disc specimens (8 mm diameter & 3 mm thickness) were prepared from Filtek™ Universal Restorative, SDR flow+, everX Flow, G-ænial A'CHORD, G-ænial Universal Flo and G-ænial Universal Injectable. To assess the color stability in five various beverages, 25 specimens from each material were randomly distributed into five groups (n = 5), according to the utilized staining solution. Group 1: distilled water, Group 2: coffee, Group 3: red wine, Group 4: energy drink, Group 5: coke. The color changes (∆E) for all materials were measured using spectrophotometer at the baseline, after 84 days of staining and after repolishing. Data was collected and analyzed using ANOVA (α = 0.05). RESULTS: Both material type and staining solution had a significant effect on the color stability of specimens (p < 0.05). Compared to other beverages, the color value of the specimens submerged in coffee and wine showed the most statistically significant (p < 0.05) mean ∆E. SDR flow + in coffee and wine presented the highest ∆E when compared to other tested materials (p < 0.05). After staining of the composites, repolishing was successful in lowering the ∆E value. CONCLUSIONS: All the beverages had an impact on the color stability of the tested resin composites, with coffee and wine demonstrating the most significant effects. The variations in color stability varied depending on the specific material utilized. Dentists should possess awareness regarding the chemical interactions that occur between different beverages and various types of resin composites. Additionally, repolishing serves as an effective technique for eliminating surface discoloration in composite restorations.

Effect of polyacrylic acid on dentin protease activities.

OBJECTIVE: This study tested whether treatment of demineralized dentin with polyacrylic acid (PAA) has any activatory or inhibitory activity on dentin matrix metalloproteinases (MMP)s or cathepsin K (CAT-K). METHODS: Dentin beams (1mm×2mm×6mm; n=10) were completely demineralized with EDTA. After initial dry mass assessment, the beams were dipped into 37% phosphoric acid (PA), PA+2% benzalkonium chloride (BAC), PA+2% chlorhexidine digluconate (CHX), 10% PAA, PAA+BAC or PAA+CHX for 20s. Demineralized beams without treatment served as control. All beams were incubated in simulated body fluid (SBF) for 1 week and the dry mass loss was evaluated. Aliquots of SBF were used to analyze solubilized telopeptide fragments using ICTP as indicator of MMP-mediated collagen degradation and CTX for CAT-K-mediated degradation. Additional demineralized beams (n=10) were used to measure the influence of different chemical treatments on total MMP activity of EDTA-demineralized dentin using generic MMP assay. Data were analyzed by ANOVA (α=0.05). RESULTS: Dry mass loss ranged from 6% (PA) to 2% for (PA-BAC) or (PAA-BAC) (p<0.05). ICTP release of PAA-treated group was significantly higher (p<0.05) than the control, and not significantly different from the PA group (p>0.05). PA+CHX or PAA+CHX and PAA+BAC showed significantly lower ICTP than PA or PAA groups (p<0.05). CAT-K activity increased significantly after 10% PAA treatment compared to control (p<0.05) or to PA postreatment. SIGNIFICANCE: Demineralized dentin treated with 10% polyacrylic acid activated CAT-K more than 37% phosphoric acid; 2% chlorhexidine digluconate seems to be a better inhibitor of MMPs and CAT-K than 2% benzalkonium chloride.

Effect of light curing type on cytotoxicity of dentine-bonding agents.

AIM: To compare the cytotoxic effects of dentine-bonding agents (DBAs) polymerized with two different curing units at 24 h and 72 h on L-929 cells. METHODOLOGY: Disc-shaped test samples of light-activated DBAs were prepared according to manufacturers' instructions and cured with either conventional quartz tungsten halogen or light-emitting diode light curing units (LCUs). After curing, the samples were transferred into a culture medium for 24 h. Eluates were obtained and pipetted onto L-929 mouse fibroblast cultures (3 x 10(4) cells per well), incubated for evaluation after 24 and 72 h. After both incubation periods, measurements were performed by an dimethylthiazol diphenyltetrazolium assay. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells with a control (culture without sample). Statistical significance was determined by a three-way analysis of variance followed by the Mann-Whitney U-test. RESULTS: No significant three-factor interaction occurred amongst LCUs, DBAs and time factors (P = 0.955). LCUs and DBAs had a significant two-factor interaction (P < 0.001). In general, the test materials cured with the light-emitting diode LCU demonstrated higher cell survival rates when compared with the those cured with the quartz tungsten halogen. CONCLUSIONS: Differential toxic effects of the DBAs cured with the quartz tungsten halogen or the light-emitting diode on the fibroblast cells may prove to be very important when suitable DBAs or LCUs are used for operative restorations.

Surface roughness of flowable and packable composite resin materials after finishing with abrasive discs.

The aim of this study was to compare surface roughness of flowable (Admira Flow, Filtek Flow, Tetric Flow) and packable (Admira, Filtek P60, Tetric HB) composite resin restorative materials finishing with Sof-Lex discs by means of average surface roughness (Ra) measurement using a surface profilometer and scanning electron microscopy (SEM). For each test group five specimens were prepared and roughness was measured in five different positions using a profilometer with a traversing distance of 4 mm and a cut-off value of 0.8 mm. The radius of the tracing diamond tip was 5 microm and measuring force and speed was 4 mN and 0.5 mm/s, respectively. The surface roughness of each individual disk was taken as the arithmetic mean of the Ra values measured in five different positions. Additionally, one specimen of each test group after finishing was observed under SEM with the magnification of x800 and x2500. Before finishing with Sof-Lex discs, flowable composite materials showed a smoother surface than packable composites restoratives (P < 0.05). However, after the finishing procedures similar surface textures were observed both from packable and flowable composites (P > 0.05).

Microleakage of different types of temporary restorative materials used in endodontics.

A temporary filling should seal the endodontic access cavity to avoid reinfection of the root canal system during endodontic treatment. The aim of this study was to evaluate the marginal seal of four temporary filling materials in endodontic access cavities in vitro, using the dye penetration method. Endodontic access cavity preparations were in 50 incisor and 50 molar noncarious nonrestored crowns of extracted human teeth. The coronal access of 10 teeth per group were filled with Coltosol, Algenol, IRM, Fermit or Fermit-N. After storing the teeth in demineralized water for 48 hours, they were immersed in 2% methylene blue dye for 24 hours. All the teeth were sectioned longitudinally and the linear depth of dye penetration was evaluated under a stereomicroscope. There was no significant difference in the microleakage observed in the high elasticity light-cured resin composite (Fermit) versus the low elasticity light-cured resin composite (Fermit-N) groups (p > 0.05).

The effect of bonding agents on the microleakage and bond strength of sealant in primary teeth.

This in vitro study investigated the effect of use of three dentine bonding agents: Scotchbond Multi-Purpose Plus (3M Dental Products, St. Paul, Minnesota, U.S.A.), Syntac (Vivadent, Schaan, Liechtenstein), Optibond Dual Cure (Kerr, Romulus, MI, U.S.A.) on microleakage and shear bond strength of a fissure sealant (Helioseal F, Vivadent, Schaan, Liechtenstein) bonded to either dry or wet (saliva contaminated) enamels of primary teeth. Newly extracted 112 non-carious primary teeth were sectioned and embedded in resin blocks. Eight groups were formed for each test. Each group consisted of 14 specimens. Group 1 and 2: fissure sealant was applied directly to etched enamel in dry and wet condition, respectively; Group 3 and 4: fissure sealant was applied onto etched and Scotch-bond Multi-Purpose Plus treated enamel in dry and wet condition, respectively; Group 5 and 6: fissure sealant was applied onto etched and Syntac treated enamel in dry and wet condition, respectively; Group 7 and 8: fissure sealant was applied onto etched and Optibond Dual Cure treated enamel in dry and wet condition, respectively. The results revealed that the use of an enamel-dentine bonding agent under fissure sealant increased the bond strength and decreased the microleakage. The use of enamel-dentine bonding agents under sealant in moisture contaminated conditions gave better results than applying sealant alone onto non-contaminated teeth. Finally, Scotchbond Multi-Purpose Plus yielded the best results for both tests.

Flouride release from various restorative materials.

Fluoride release from six light-activated restorative materials, including two resinmodified glass-ionomers, two composites, and two compomers, was evaluated and compared with one conventional acid-based glass-ionomer cement. The amount and rate of release varied among the tested materials. Both resin-modified glass-ionomers and the conventional acid-base glass-ionomer cements released more fluoride then the composites and compomers (p < 0.05). Additionally, composite materials released less fluoride than compomer materials (p < 0.05). Release of fluoride by the tested materials showed a significant decrease after all the tested time intervals.

Evaluation of coronal microleakage of four different glass-ionomer cements in endodontically treated teeth.

Four different glass-ionomer materials were evaluated for coronal microleakage in permanent lingual access restorations of endodontically treated anterior teeth. Forty extracted human anterior teeth were randomly divided into four groups following chemomechanical preparations and obturations with gutta-percha and sealer. Logobond, Aqua Ionobond, Ionoseal and Ketac-Cem were placed in 2 mm thickness over the gutta-percha obturation from cemento-enamel junction. Eight teeth were used as negative and positive controls. The teeth were thermocycled, coated with nail varnish and paraffin except around the access preparation. Next they were placed in dye and cleared to allow visualization of dye penetration. There was a tendency for the Ketac-Cem group to lack least but there were no statistically differences among the groups.